^-..^^ Digitized by the Internet Archive in 2011 with funding from The Library of Congress http://www.archive.org/details/galvanizingtinni01flan GALVANIZING AND TINNING A Practical Treatise on the Coating of Metal with Zinc and Tin by the Hot Dipping, Electro Galvanizing, Sher- ardizing and Metal Spraying Processes, with Information on Design, Installation and Equipment of Plants. By W^TF FLANDERS Malleable Iron Fittings Co. With the Assistance of the following Specialists John Cai.der, R. D. Foster, C. J. Kirk, a. f. schoen, Louis Schulte, Wm. G. Stratton, Samuel Trood. Metal Coatings Co. of America Hanson & Van Winkle Co. U. S. Sherardizing Co. New Haven Sherardizing Co. Ele-Kem Co. R. N. Bassett Co. Consulting Engineer U. P. C. BOOK COMPANY, Inc. 243 W. 39tJi St. Nf.w York Reprinted 1922 Copyrighted 1916 By DAVID WILLIAMS COMPANY Copyrighted 1922 By the U. P. C. BOOK COMPANY. Inc. Printed in U. S. A. JUN 13 1922 (am AB77127 PREFACE THE original work "Galvanizing and Tinning" was prepared to meet the demand for reliable information on the meth- ods of protecting iron and steel from corrosion which the editors of the Metal Worl-er and Tlie Iron Age were continually receiving. Mr. Flanders, who had specialized on the hot dipping processes of coating with zinc and tin for many years, was induced to describe the proper design and equipment of plants and the methods he had found most satisfactory. Since it was published, many improvements have been made in the hot galvanizing and tinning processes. Several new methods of utilizing zinc and tin for protection against corrosion have also ))een devised and perfected. Mr. Flanders did not feel qualified to treat these new processes, and, as a majority of them are cov- ered by patents, it was difficult to obtain practical information regarding their application, as well as the design and installation of the apparatus. Several of the experts who had sj^ecialized on the new processes refused to contribute because they deemed their methods "trade secrets," while others supplied splendid advertising matter for their special process, but little practical data. The treatment of hot galvanizing and tinning is as compre- hensive and reliable as Mr. Flanders' practical experience could make it. This covers a period of over thirty-five years as mechanic, builder and manager of plants. He was ably assisted in this work by Mr. H. A. Smith, who contributed a large amount of data that is new. In revising the chapter on re-tinning, Mr. Flanders received much valuable assistance from Mr. AV. C. Holland, a former shop- mate, and from Mr. J. B. Smith, mechanical engineer, and Mr. W. E. Mumford, metallurgist. Many interesting and valuable articles by other experts, bearing •2 PREFACE on protective coating of zinc and tin, which have appeared in vari- ous trade papers, have been included and proper credit given in the text. The aim of all who have assisted in the preparation of this work has been to make it of the greatest practical value to the men actually engaged in the plant, as well as to those who are contem- plating the installation of plants. If the readers of the book fail to find the information they desire, the publishers will be pleased to have them submit the problems for the consideration of the experts who collaborated in making it so nearly complete. The Editor Nev/ York, May, 1922. TABLE OF CONTENTS CHAPTER I PAGE Corrosion and Its Prevention 9 Tliporv of Corrosion— Galvanizing Proccssos Descrilicd — Zinc Coating tiie Best Rust Preventive — Hints on Selection of Em- ployees and Handling of Work and Equipment. CHAPTER II Hot Galvanizing Plant and Equipment 14 Arrangement, Drainage and Ventilation of the Galvanizing Room — Tlie Equipment — Laws of Physics Applying to Hot Galvan- izing — The Selection of Proper Grades of Iron and Steel for a Kettle — Methods of Testing Material for Manufacture of Ket- tle — Sizes of Kettles for Different Work — Plans and Details of Construction for Different Style Kettles — Plan and Details of Construction of Arrangement for Drying Castings — Bricking In a Galvanizing Kettle — Tanks for Acid Solutions and Water — Tools for Galvanizing. CHAPTER III The Pyrometer 34 Use of Pyrometer — Protecting Pyrometer from Action of Zinc — Proper Location of Pyrometer in Kettle — Temperature of Zinc Required to Secure Uniform Coatings — Selection of Pyrometer — Temperature Table and Method of Calculating Numbers of De- grees Drop Per Hour in Molten Zinc While Cooling — Correct INIethod of Using Tliermometer. CHAPTER IV Materials Used in Galvanizing 41 Spelter — Lead — White and Gray Granulated Sal Ammoniac — Zinc Ammonium Chloride — Muriatic, Sulphuric and Hydro- fluoric Acids — Coke — Oil — Glycerine — Aluminum. CHAPTER V Pickling 44 Securing Uniform Action with Acids — Mechanical Pickling — ■ Pickling Sheets — Over Pickling — LTnder Pickling- — Acid Con- simiption in Pickling — Removing Scale with Sulphuric Acid — Time Required for Removal of Scale — Removing Scale with Muriatic Acid — Substitutes for Acids — Cleaning Sandy Castings with Sulphuric Acid — Cleaning Castings with the Aid of Hydro- fluoric Acid — Temperature of Pickle — A "Quick" Pickle. CHAPTER VI Water Rolling, Tumbling and Sand Blasting ... 51 W'ate^r Rolling — Dry Tumbling — Dcssign and Construction of Wet Tumbling Barrel — Preparing Castings for Tumlding — Load- ing Tumbling Barrel — Time Required to Clean Work in Tnm- bling Barrel — Mixtures for Cleaning Castings in Tumbling Bar- rel — Testing Castings to See if They are Properly Cleaned — Re-charging Tumbling Barrel — Handling Delicate Castings in Tumbling Barrel — Storing Castings After Tumbling — Prepairiug- 3 4 CONTENTS PAGE Work for Galvanizing or Tinning With the Sand Blast — Simple Home-made Type — Single Hose Type Apparatus — Two Hose Type Apparatus — Sand Blast Rolling Barrel — Air Pressures Re- quired in Sand Blasting — Construction and Ventilation of Sand Blasting Room — Condition of Sand — Diamond Grit and Steel Shot Used as Substitute for Sand — Preparing the Cleaned Work for the Dippings — Drying the Work. CHAPTER VII Hot Process of Galvanizing 66 Filling a New Kettle — Firing a New Kettle — The Temperature of the Zinc — Dipping the Work in the Molten Zinc — Removal of Surplus Zinc — Drying and Cooling Work — Cost of Production. CHAPTER VIII Galvanizing Sheets 73 Galvanizing Sheets by Hand — Construction of Davies Machine for Galvanizing Sheets — Davies Method- — Heathfield Method — Bayliss Process — Material Required to Galvanize Sheets. CHAPTER IX Galvanizing Wire, Netting and Tubes 77 An Improvement in Galvanizing Wire Cloth — The Influence of Galvanizing on the Strength of Wire — Tests Used to Determine Strength of Wire — Absorbed Hydrogen Gas Does Damage — The Automatic Galvanizing of Tubes — Plan and Elevation of Ma- chine for Automatic Galvanizing of Tubes. CHAPTER X By-Products of the Hot Galvanizing Process ... 84 Zinc Dross — Running Over or "Sweating" Zinc Dross — Plan and Details of Construction for Kettle Used in Recovering Zinc Dross — Sal Ammoniac Skimmings — Screening, Storage and Re- covery of Zinc Ashes. CHAPTER XI Replacing Old Galvanizing Kettles 92 Life of Kettles — Repairing Leaks in Kettles — Tools for Boiling Out Kettles. CHAPTER XII The Schoop Metal Spray Process 94 Evolution of Apparatus — Operation of Old Stationary Type — Details of Construction of Old Stationary Type^Operation of First Portable Type — Details of First Portable Type — Opera- tion of the Cyclone Apparatus — Details of Construction and Operation of Modern Spraying Pistol — Melting Point of Zinc and Tin in Schoop Process — Gas Pressure Required — Applying the Coating — Thickness of Deposit — Cost of Coating. CHAPTER XIII Tinning Malleable Iron Castings, Wrought Iron, and Steel . 106 Plant and Equipment — Plan of a Tinning Plant — Tools and Kettles. CONTENTS 5 PAGE CHAPTER XIV Preparing the Work for Tinning Ill Removing Scale and Rnst with Sulphuric Acid — Cleaning Sandy Castings with Sulphuric Acid — Cleaning with Muriatic Acid — Cleaning Sandy Castings with Hydrofluoric Acid — Water Rolling — Removing Paint or Grease. CHAPTER XV Applying the Coating of Tin 115 Tinning with Two or More Kettles of Tin — Setting Up the Kettles — Passing the Work Through the Tinning Kettle — Tem- perature and Time Required — Tinning Wire in Coils — Tinning Steel Spoons and Similar Articles. CHAPTER XVI Re-Tinning 121 Construction of Re-tinning Plan Having Four Kettles — Tools Required — Method of Handling Work — Use of Listing Kettle — Removal of Surplus Tin in Skimming Kettle — Finishing of Re- tinned Work — Replacing Re-tinning Kettles. CHAPTER XVII Tinning Gray Iron Castings 129 Plans of Plants, Showing Arrangement of Equipment — Eleva- tions and Details of Constrviction of Kettles — Tools Required. CHAPTER XVIII preparing Gray Iron Castings for Tinning .... 133 Removing Sand from the Castings — Freeing Gray Iron Castings from Sand by Hydrofluoric Acid — Cleaning Sandy Castings with Sulphuric Acid — Cleaning Castings with the Sand Blast — The Use of Hot Alkali Bath in Certain Cases — Tumbling — Water Rolling. CHAPTER XIX Coating Gray Iron Castings with Tin . . . . , . 138 Dipping the Castings — Flux for Tinning Kettle — Handling Cast- ings in Roughing Kettle — Time Required to Tin Castings — Re- moval of Slag from Kettle — Proper Heat for Tinning — Construc- tion of Oil Tank — Tongs Used in Tinning — Construction and Use of Switching Box — Tinning with Three Kettles of Tin — Effect of Overheating — Storage of Dross. CHAPTER XX Cleaning Old Galvanized and Tinned Work .... 146 Cleaning Old Galvanized Work — Refinishing Old Galvanized Work — Cleaning Old Tinned Work — Kettles for Refinishing Old Galvanized and Tinned Work. 6 CONTENTS PAGE CHAPTER XXI Electro-Galvanizing Plant and Equipment .... 148 Electro-Galvanizing — Equipment for Electro-Galvanizing Plant — Mechanical Galvanizing and Patented Devices — The Miller Chain Conveyer Machine — -Daniels Screw Conveyer Machine — The Fleischer Cable or Chain Conveyer Machine- — The Daniels Barrel— The Pothoif— The Schulte Barrel— The Ele-Kem Galvan- izing Barrel — A Cleaning, Rinsing and Plating Barrel Unit — Modified Form of the Cleaning, Rinsing and Plating Barrel Unit — The Meaker Continuous Type Machine — Hanson & Van Winkle Pipe and Tube Galvanizing Machine — The Pothoff Tube Galvan- izing Machine — King's Continuous Wire Clotli Machine — The Root Wire Cloth Machine — Schulte Wire Galvanizing Machine — Electrical Equipment — Anodes — Cost of Installation. CHAPTER XXn Preparing Work for Electro-Galvanizing 209 Removing Sand from Castings — Removing Oil or Grease — Re- moving Mill Scale — Scratch-Brushing — Copper Flashing — Tum- bling and Sand Blasting — Schulte Grinding and Scouring Ma- chine — Electro-Cleaning. CHAPTER XXIII Electro-Galvanizing Solutions and Their Application . 217 Composition of Galvanizing Solutions — Twenty-foTir Good For- mulas — Agents for Experimenting on or Improving Solutions — Modern Methods of Applying the Coatings — Cost of Operation — Tests for Thickness of Zinc Coating. CHAPTER XXIV The Art of Sherardizing 227 Dry Galvanizing in Prehistoric Times — Theory of Sherardizing — How Precipitation of a Vapor on Metal Occurs — Methods of Producing Zinc Vapor. CHAPTER XXV Location and Equipment of the Sherardizing Plant . . 233 Cleaning Apparatus — The Sherardizing Furnace or Oven — Coke Burning Furnaces — Gas and Oil Burning Furnaces — Electric Heated Furnaces — Wiring Diagrams — Drums — Dust Separating Machine— The Transfer Car — Cooling Frames — Pyrometers. CHAPTER XXVI Materials Used in Sherardizing 256 Dvist from the Zinc Smelter — Freeing Dust from Iron — Use of ManufacturedsZinc Dust — Method No. 1 for Determining Metal- lic Zinc in Zinc Dust — ^Method No. 2 for Determining Metallic Zinc in Zinc Dust — Method No. 3 for Determining Metallic Zinc in Zinc Dust. CHAPTER XXVII Preparing Material and Loading 261 Pickling of Steel — Pickling Malleable and Gray Iron Castings — Loading the Drums — Packing the Electric-Heated Drum. CONTENTS 7 CHAPTER XXVIII page Temperature and Duration of Heats 267 Tliickiiess of C()atini>- — Tcmporatnrc an Important Factor — Operation of the Electric-Heatod Drum — Slicrardi/.infjr with Zinc Under Vacuum — Time an Important Factor — Motion During Shcrardizing- — General Operation — Cooling and Unloadiny. CHAPTER XXIX Don'ts in Sherardizing Practice 278 Eliminating Black Spots on Finished Work — Obviating Non- Uniformity of Coating — Improving Psychological Condition of Men— ^Caution — Don'ts. CHAPTER XXX Coloring and Finishing Sherardized Articles .... 282 Bulling — (_'utting Down — Burnishing — Nickel — Copper — Bronze — Japanning — Enameling — Lacquering. CHAPTER XXXI Cost of Sherardizing Material Per Ton with Different Fuels . . . . ' 287 Cost for Fuel Oil Burning — Producer Gas — Coke — Illuminating Gas — Disposal of Used Zinc or Zinc Residue. CHAPTER XXXII Galvanizing Specifications and Tests 291 Specifications for Hot and Electro-Galvanizing — Preece or Copper Sulphate Test — Limitations of the Preece Test — Lead Acetate Test — Caustic Soda Test — The Preece Test — Manipulation and Temperature of the Preece Test — Consideration of Objections to Preece Test — Manipulation of Lead Acetate Test — Preece and Lead Acetate Tests Compared — Electrolytic Methods of Testing — Caustic Soda Test — Government Test — Salt Spray Test — Con- struction of Box for Salt Spray Test — Chart of Comparative Tests — Hydrochloric Acid and Antimony Chloride Tests for Sheots and Wire. Galvanizins and Tinning CHAPTER I Corrosion and Its Prevention 1E0N and steel will invariably rust or corrode if exposed to the atmosphere without protection, and Mr, Alfred Sang, in The Iron Age, explains the reasons for this fact in an ex- cellent manner, as follows: "One of the most persistent problems which confront the worker in iron and steel is the prevention of corrosion. We can- not rid ourselves of the agents which effect the corrosion of iron without at the same time ridding ourselves of the agents which are essential to life itself. "Air is indispensable both to human respiration and for the for- mation of rust and other oxides, for which it supplies the oxy- gen; moisture is necessary for the formation of clouds, which make the earth fertile, and it also supplies the medium in which rusting takes place and hydrates the oxide; carbonic dioxide is an animal by-product and a raw material for the vegetable world, and the exchange of carbonic dioxide and oxygen, which is con- tinually taking place between the animal and the vegetable knig- dom, is of vital importance. Then, on the other hand, rust is not readily formed, if at all, unless there be an acid present, and the acid which is most universally distributed is carbonic acid, or hydrated carbonic dioxide. "There is, as you see, a close relationship between the processes of living and rusting, but, while human beings make up for the rusting or decaying of their tissues by nutrition, it has not yet been discovered how to feed or regenerate iron, and until such a discovery is made we are compelled to take our cue from the ancient Egyptians and resort to embalming. "There are two general ways of embalming iron to prevent its decomposition, which might be called, respectively, the metal- lic and non-metallic methods. In the non-metallic method the ar- 9 10 GALVANIZING AND TINNING tides are coated with, an organic substance, usually oil, or varnish, the efficiency of which depends on its being more or less airtight; when coloring matter is added to the oil it becomes a paint, but I understand from authorities on the subject that a varnish free from pigments is preferable to anything else. The metallic method consists of coating the iron with some other metal, and it is this method which I have come to discuss with you. "Iron rusts less easily than does steel; this is perhaps due to steel being a very composite material. In the iron, which forms the bulk of its composition, are dissolved or immersed a great variety of other substances; some of these are simple, such as graphite, silicon and manganese, and others are compound, such as carbides, sulfides, phosphides and silicides. The carbon com- pounds are very numerous and diversified, being due to different heat treatments; the best known are cementite, pearlite and mar- tensite. Just as variety is to some people the spice of living, so is heterogeneous composition the spice of rusting, in the present in- stance at any rate. jSTor is this by any means a solitary instance ; it is a well-known fact that chemically pure zinc is dissolved very slowly by certain acids, whereas the commercial product, especially if it be high in iron, is rapidly dissolved." Great trouble and expense annually falls upon manufacturers, metal workers and property o^vners through the rusting or cor- roding of iron and steel. An illustration of this is shown by the following, which recently appeared in The Iron Age: "The receivers of Milliken Brothers, Incorporated, 11 Broad- way, New York, have lately made some extensive experiments in connection with protecting from oxidation steel grillage beams used in building construction. More or less water is present in nearly every building where grillage beams are used. There- fore, unless the beams are absolutely protected, there will be oxi- dation. As such beams are not usually exposed to view and can- not be examined, if oxidation takes place after the building is up and the oxidation becomes serious, the security of the building is threatened. "Finding that coating the beams with paint, asphalt or tar cannot be absolutely relied on for a great length of time, Milli- ken Brothers have experimented with galvanizing by the hot process, after all the shop work has been done on the steel. It has been shown that concrete will adhere to galvanized steel CORROSION AND ITS PREVENTION 11 beams as firmly as to iinpainted beams, and much better than to painted beams. Architects and engineers who have had occasion to examine galvanized Ashlar anchors and galvanized pipes used in connection with concrete have found that concrete will attach itself as readily to galvanized material as ungalvanized material. The advantage of galvanizing is that it gives the steel beam a complete zinc coating which will resist the a'ction of the water and therefore protect the steel. The expense connected with the gal- vanizing is considered small in comparison with the resulting benefits.'^ Zinc Coating the Best Rust Preventive It is my purpose in this volume to deal with the subject of coat- ing iron and steel products with zinc, or, as generally termed, gal- vanizing them (to prevent rusting), which has become a large and important industry in which much capital is invested and many men are employed. Zinc is without doubt the best protective coat- ing for iron and steel, and the reasons are clearly stated in The B7-ass World, which says: "It is difficult for many persons to understand why zinc is the best rust preventive for iron or steel, and they believe it is on ac- count of its cheapness that it is so extensively used. They have an idea that lead, being a cheaper metal, would answer far better, and as it is more non-corrosive than zinc, would protect the iron better. This is not a fact, however, as will subsequently be explained. "The very fact that zinc is a corrosive metal does not affect its properties when applied as a coating to iron or steel. Indeed, if it did not corrode, it would not be of value for such a purpose. When iron or steel, which has been coated with zinc, is exposed to the atmosphere, a galvanic action is set up, although, of course, ex- tremely slight. Any two dissimilar metals form a galvanic couple, but as zinc is the most electropositive metal, the galvanic action between the zinc and iron is as great as could be obtained when iron is used for one of the metals composing the couple. "The 1 esult is, therefore, that with the slight galvanic action set up on galvanized iron or steel, when exposed to the atmosphere, a corrosion takes place. Did it not follow, then there would be no protection. In this case, the zinc, being the electropositive metal, suffers corrosion at the expense of the electro-negative metal iron. The effect is that the corrosion goes on with the zinc exclusively 12 GALVANIZING AND TINNING and iron is not corroded at all, provided any zinc is left on the iron or steel. This condition takes place whether a light or heavy coating of zinc is present. The only advantage of a heavy zinc coating is that it will last longer, but under ordinary atmospheric conditions, where a slight amount of moisture is the only exciting liquid, the galvanic action is very small and the zinc coating, be it ever so light, lasts a long time. In the case of sea-water or air saturated with salt moisture, the corrosion, of course, is much more rapid and a heavier zinc coating is required to resist it for a length of time. ■^'The reason for the protection of iron or steel by a zinc coating is, therefore, on account of the fact that the zinc corrodes at the expense of the iron or steel by the galvanic action set up. Zinc, however, when exposed to the air, does not corrode rapidly or deeply and, in fact, very lightly. This property is of great value, as the zinc coating does not corrode rapidly, even with the galvanic action set up, so that it lasts for a far greater length of time than would naturally be expected. The very fact, however, that the zinc corrodes at the expense of the iron is all that is necessary to pro- tect the iron or steel, even though it be extremely slight. ''^Other metals like lead or tin, on account of their not being electropositive to iron, do not act like zinc. They act simply as a covering like a paint or varnish, and if portions of the iron happen to be exposed, even such as a pinhole, the iron begins to corrode. AVith a zinc coating, however, this will not take place." Therefore there are well founded reasons for the growth and development of the galvanizing industry, since zinc is the best pro- tective coating for iron and steel and is comparatively low in price. The oldest galvanizing process and the one most generally used is the hot or dipping process, although the "cold" or Electro process is used to considerable extent and it has unquestionably gained ground since its invention, about twenty years ago. Sherardizing has come into use since the introduction of the Electro process. While its inventor does not use the term "galvanizing" in connec- tion with the Sherardizing process, it is, in fact, as truly a gal- vanizing process as is the hot dipping or Electro process. The protective coating in the Sherardizing process is metallic zinc de- posited from zinc dust or zinc oxide, while in the hot and Electro processes the zinc is used in the form of slabs or cast anodes. CORROSION AND ITS PREVENTION 13 As the hot or dipping process is the oldest, we will give it our first attention, and writer will describe to the best of his ability methods employed in the different branches of the business, giving ]-)rineipal attention to miscellaneous work, such as gray or malle- able iron castings, wi'ought iron and steel forgings, coal hods, and other articles made from sheet iron, devoting for obvious reasons short paragraphs to the galvanizing of sheets, pipe, wire, wire cloth and poultry netting. The galvanizing of these materials is simply one process in their manufacture ; and most of the concerns producing them either use methods of their own or patented de- vices, which it would be unfair on one hand, and useless on the other, to describe. Job shops for the handling of miscellaneous galvanizing are found in nearly all large cities in this country, and many manufacturers of specialties operate their own galvanizing plants. It may not be out of place to say that it has been, and still is, the practice of some engaged in this business to make as much of a mystery of the operations as possible. Mystery and secret for- mulae were looked upon (not so many years ago either) as the key to monopolizing many so-called metallurgical processes ; but those times have passed, and the reading public will have little trouble in following out any present methods if it will note the publica- tions and lucidly written books bearing on the subjects in ques- tion. One fallacy generally credited is that galvanizing kettles must never be allowed"to cool off. While it is true that it is not advisable to allow a kettle holding several tons of zinc to cool off at frequent intervals, and it is not in the interest of economy for one having a small amount of galvanizing to attempt to do it him- self, there is no reason why a kettle containing a few hundred pounds of metal cannot be operated fairly successfully, and pos- sibly to good advantage, if one is not conveniently located for sending the work to a jobbing galvanizer. We wish to impress the reader with the fact that we are not advocating the installation of a galvanizing plant as a matter of economy unless one has sufficient work to keep it in constant operation and employ skilled help. Unskilled workmen cannot produce best results, and the materials he must use are expensive. The operation of a very small plant will be found a costly experiment at the best, and should never be attempted unless actually necessary. CHAPTER II Hot Galvanizing Plant and Equipment TO THOSE contemplating the installation of a galvanizing plant the first consideration shonld be to isolate it as much as possible from the main factory, as the fumes arising from the chemicals used in the business are not only destructive to tools and machinery, but to many kinds of finished goods. It is very difficult to dispose of these fumes in such a way that they will not prove an annoyance as well as a menace to machmery, tools and stock. The Galvanizing Room In fitting up a room or building in which to locate the plant provision should be made to obtain the l)est possible ventilation. The building should be high posted, with a good ventilator in the Fig 2 — Front and Side Elevation of a Movable Hood roof, and better working conditions are obtained by covering the kettles and acid tanks with hoods connected to an exhaust fan of suitable size and speed. If an exhaust fan is used, most of the fumes arising from the kettles and acid tanks can be discharged into a stack or chimney of suitable height, and thus disposed of making conditions fairly comfortable. 14 HOT GALVANIZING PLANT AND EQUIPMENT 15 Where hoods are used over the kettles and tanks they should come as low as possible and not interfere with the workmen. They should be large enough to project well beyond the kettles or tanks so as to catch everything possible in the way of steam and smoke that naturally rises when the plant is in operation. When the work consists of castings and other small articles, there is no objection to having the hoods come to within 6 feet 6 inches of the floor. Where hoods are used on large kettles they should be suspended from a carriage or trolley on an overhead track which will permit of their being easily moved out of place when it is desirable to do so. We illustrate our method of putting up a movable hood by Fig. 2, although it is entirely possible that some- thing much better might be devised. Fig. 3 — Shop Akkangement with Tile Drains for Acid Tanks Considerable water is used in the hot process of galvanizing when miscellaneous work is done, and provision should be made to secure proper drainage. A good plan is to put catch basins under the various acid and water tanks, connected by tile pipe to sewer, as sho^vn in floor plan. Fig. 3. The floor can be cement or brick. If the work to be handled is gray iron it is not absolutely neces- sary to use steam, but if it is of a nature that requires the re- moval of scale, or if malleable castings are to be galvanized in quantities, steam should be brought into the room. 16 GALVANIZING AND TINNING A floor space 25 feet by 48 feet will accommodate an outfit such as we illustrate in Fig. 3. Much less floor space can be made to accommodate a very small plant that is designed to operate only at irregular intervals. Fig. 4 — Floor Plan of Galvanizing Room with Underground Flue Fig. 3 is the ground plan of a galvanizing plant, in which A is a tank for containing a solution of sulphuric acid and water for removing scale and rust; B is a water tank for storing work that has been cleaned; C is a tank for muriatic acid; D is a tank for hydrofluoric acid; E is the plate for drying the work before im- mersing it in the molten zinc; F is the kettle containing the molten zinc; G G are tanks, one of which is divided, and contain HOT GALVANIZING PLANT AND EQUIPMENT 17 the water used for cooling the work after it has been removed from the galvanizing bath; H is an underground flue connecting the drying plate E with the chimney or stack J ; K is a pit giving access to the fire and ash pit under the drying plate E ; M M are catch basins, located under the several acid and water tanks, with tile pipe connections N to sewer. Another plan of a galvanizing plant is shown by Fig. 4. This plant, which occupies a floor of 25' x 50', was designed for use where the old-fashioned method of pickling sandy castings with sulphuric acid was to be employed. A small plant of this kind could be put in a much smaller floor space. In floor plan Fig. 4, A is a tank for containing a solution of sulphuric acid and water for removing scale and rust. B is a water tank for storing work that has been cleaned. C is a platform where castings are placed to free them from sand with the use of sulphuric acid. D is a tank used to contain the solution for removing the sand from the castings after they have been placed on the platform. E is a tank for containing muriatic acid. F is the plate for drying the work before immersing it in the molten metal. G is the kettle containing the metal, and H is the tank used for cooling the work after it is coated with the zinc. I I indicate the loose planks covering the ash pits, shown in Fig. 11 as P P. K is an under- ground flue connecting the drying plate F with the chimney or stack L; and M is a pit to give access to the ash pit under the drying plate F. The Equipment The equipment of a galvanizing plant for miscellaneous work consists of a kettle of suitable size, which should be built of the very best material obtainable; a drying "arch," ''plate" or "oven" for drying the castings prior to immersing them in the molten zinc; wooden tanks for containing water and the different acid solutions; and miscellaneous tools best adapted to the work in hand, such as tongs, hooks and baskets of perforated sheet iron or wire cloth. Considerable ingenuity can be exercised in devising implements for handling the various kinds of work. We shall refer to this matter of tools later under a special head. The material used in the construction of galvanizing kettles and tools which come in contact with the molten spelter is a matter of great importance. In this connection, the statement of the super- 18 GALVANIZING AND TINNING intendent of one of the largest sheet galvanizing plants in the country is interesting, and we give it herewith. The endeavor to find the most suitable material for manu- facturing those parts of the machinery which are immersed in spelter, as well as the best container for the molten spelter, has occupied the attention of galvanizers for all time. The only sub- stances which are not dissolved are vitreous, and consequently, im- practical. All of the common metals are soluble in molten zinc, and all of them are miscible in all porportions, with the exception of lead and iron. For this reason, and because of the many other desirable properties which iron possesses, it is universally used at the present time. The old galvanizers made their machinery of wrought iron; but with the introduction of Bessemer and open hearth steel have quite generally adopted this material, because it possesses certain very distinct advantages over wrought iron. It does, however, go into solution much more rapidly than the old wrought iron did; so that for the last ten years the search has been for a material which will work as well as steel does, and resist the solvent action as well as the iron. The laws of physics teach us that an impure substance will go into solution more rapidly than a pure one, and we do not find exceptions when dissolving iron in zinc. The purer the iron the more slowly it goes into solution. This is the reason that the old-fashioned puddled iron lasted so much longer than the modern steel. Now that ingot iron is being commercially produced, it has been very easy to demonstrate this fact in a scientific manner. In a recent investigation the following facts were disclosed: Sixteen gauge samples of various analysis were suspended in molten spelter for twelve days with the following results: Sulphur Phosphorus Carbon Manganese Silicon Copper Loss in 12 Having satisfactorily demonstrated that there was a very marked difference between pure iron and steel (impure iron), another set Armco Iron Steel Steel .032 .036 .022 .008 .067 .006 .010 .045 .010 .017 .372 .145 trace trace trace .048 trace .192 11.2% 40.9% 27.00% HOT GALVANIZING PLANT AND EQUIPMENT 19 of experiments was conducted to bring out the difference in the effect between slight variations in very pure iron. Samples of the following analysis were used, and were suspended for four hun- dred fifty hours (three 150 hour periods). 1 2 3 4 5 Silicon trace trace trace trace trace Sulphur .022 .025 .025 .026 .027 Phosphorus .003 .004 .003 .003 .005 Carbon .015 .04 .015 .01 .10 Manganese .02 .005 .04 .01 .065 Copper .045 .035 .11 .11 Oxygen .015 .017 .025 .041 .03 Total Impurity .120 .126 .218 .200 .227 Iron by difl'erence 99.88 99.874 99.782 99.80 99.773 Loss in 450 hours 34.4% 38.5% 42.0% 55.7% (41.5% loss in 300 hours.) Average weight of coi iting in 150 hours 370 314 272 248 212 It will be noticed that the rate of solution increases directly in proportion to the amount of impurit3^ These specimens were all weighed very carefully, were totally immersed in spelter, not com- ing in contact with the salammoniac flux at any time ; the coating being stripped off with sodium hydroxide, which dissolves the spelter but does not attack the iron. From these results it is evi- dent that while dealing with commercially pure iron it is essential to secure the very purest. A material containing 99.84% iron being much better than one containing only 99.75% iron. You will note also that the rate of solution increases with the amount of oxygen; showing the additional necessity of securing a thoroughly degassified and deoxidized material. Another interesting fact to be noticed in the table given above is that the weight of coating taken on varies inversely as the rate of solution; that is, the more rapidly the material dissolves, the lighter coating it takes on. These facts as worked out in the laboratory are very interest- ing, but needed verification in actual practice before they could be of any real importance to the galvanizer. For this reason, all parts of the galvanizing machine under the spelter, in one manu- facturer's plant, were manufactured of Armco Iron. He finds that cast Armco Iron lasts just about as long as rolled or forged 10 carbon steel; whereas Armco Iron, properly worked and heat 20 GALVANIZING AND TINNING treated, will last from three to seven times as long as mild steel will. Flux boxes, for example, lasting from eight to ten months. These statements are borne out and given additional weight by a comparison of galvanized Armco Iron sheets with galvanized mild open hearth steel sheets. The iron content of a clean spelter bath is approximately .02%. Any iron in excess of this forming dross, and settling to the bottom. The coating on Armco Iron sheets contains about 3% iron, while the coating on steel sheets contains about 4% ; showing very definitely that even in the short time that the sheets are in the spelter bath, steel goes into solution much more rapidly. It is a source of great satisfaction to know that a material is being commercially produced, which lasts even longer in the spelter than the old-fashioned wrought iron, and at the same time possesses all the excellent working qualities of steel. The Selection of a Kettle In deciding what size kettle to install one must be guided by the nature and quantity of work to be done. If small articles are to be handled, and the quantity is such as to require the plant to be operated only at intervals, a kettle 8 feet long, 15 or 18 inches wide and 20 inches deep will answer every purpose, but it is ex- tremely difficult to keep an even temperature of the metal in a kettle of this size. The only excuse for using such a small kettle is for doing an extremely limited amount of work as a matter of convenience, with cost as a secondary consideration. Bricking in a Galvanizing Kettle There are several methods of heating galvanizing kettles. Some are heated with soft coal, some with fuel oil and some with natural gas. The fuel most commonly used, however, is coke. For this reason we shall show, by illustrations, three methods of bricking in coke-fired kettles. We do not attempt to describe any particu- lar method of oil or natural gas heating, as concerns using either fuel usually have their own methods of application. Figs. 5, 6 and 7 show methods of setting a small kettle not deep enough to require ash pits at the sides and not designed to be operated continually. The grates F F are bars of iron that may be withdrawn when it is desired to let the fires out, and replaced when required for use. Fig. 5 is a top plan of the brick work and HOT GALVANIZING PLANT AND EQUIPMENT 21 kettle. Fi'j;. (i is a Ncrlical cross section of Fig. 5 at A A, aud Fiff. 7 is a horizontal section oi" Fig. G at B B. «Ioj ^-t-. D —— a.-. li t: Fig. 5- eff 'bjy^, -PLA^^ OF Kettle Fig. 7- Secf/'on B-B -Arrangement at Grate Line Section A- A Fig. 6 — Vertical Cross Section of Furnace and Kettle Fig. 8 shows the casting details for setting kettle as sho^vn in Figs. 5, 6 and 7. D is a plate to cover top of brick work surround- ing the kettle, and its position is designated in Fig. 5 as D D. E is a casting used on outside of brick work on both sides of kettle and in connection with bolts passing through their ends serve to bind the brick work together. Their position is designated in Fig. 6 as E E. F is a grate bar, the position of which is shown in Fig. 7 at F F, and G G are the castings for supporting each end of the grate bars F. Their position is designated as G G in Figs. 6 and 7. The castings for the upper and lower draft hole casings with doors, designated as H and I in Figs. 5 and 6, can be made the same as castings K, L, M and N in Fig. 13. 22 (GALVANIZING AND TINNING ^ <^ B O Fig. 8 — Casting Details for Setting Kettle if r^ 1 r-r~i r-r-L Qu -Vl /^ ^^^^^^^^^■»" O -A ■=i=r ^^W^ q_j Li__|-Hr FiG. 9 — Top Plan of Brickwork for Larger Kettle lax ^, I . I , I . I . I . I . I . I . T^A^" Fig. 10 — Side Elevation of the Same Kettle HOT GALVANIZING PLANT AND EQUIPMENT 23 Figs. 9, 10, 11 and 12 show manner of setting larger kettles where grates are used ; Pig. 9 being a top plan of the brick work ; Fig. 10 a side elevation; Fig. 11 a vertical section at A A; Fig. 9 and Fig. 12 a horizontal section at the grate line. Fig. 11 — Vertical Cross Section of Kettle and Furnace Fig. 12 — Horizontal Section at the Grate Line Fig. 13 gives details of all castings necessary for setting all grate-fired kettles, as shown in Figs. 9, 10, 11 and 12. A, Fig. 13, is a coping plate, the position of which is shown in Figs. 9, 10 and 11 as A A. These plates, when held in place by the bolts C, serve to prevent the sides of the kettle from springing outward when the iron blocks D, Fig. 13, are in their place, as shown in 24 GALVANIZING AND TINNING Figs. 9 and 11. Coping plates for kettles 4 to G ft. long should be 2 finches thick and 10 inches wide. The fire spaces E E in Figs. 9 and 1 1 should not be more than 7 inches wide, and the same length as the inside of the kettle. F in Fig. l3 is an iron plate 1 inch thick, and the position of these plates on the brick work is shown as F F in Figs. 9 and 11. Gr in Fig. 13 is a section of grate, the position of which is designated G G in Figs. 11 and 12. The openings of these grates should be about 1 inch wide, and the A 1 1 1 1 II ii i*^^ ^^p^ ^=^ 3 M 3 D Fig. 13 — Details of Castings lcr Siottixg G::ate-Fired Kettle grates should be wide enough to span the fire spaces E E in Figs. 9 and 11 and rest on plates 11 tl and the pier I on which the kettle B rests, as shown in Fig. 11. Plates like H in Fig. 13 are used to rest the outer edge of the grates G G on, as shown in Figs. 11 and 12, and also to help support the brick walls on each side of the kettle. Plates such as H in Fig. 13 may also be used to cover the top of fire boxes E E in Figs. 9 and 11, and should be about % inch thick and 12 inches wide; their length to be determined by the length of the kettle. K in Fig. 13 is a cast iron casing for the HOT GALVANIZING PLANT AND EQUIPMENT 25 upper draft holes, indicated as K K in Figs. 10 and 11. These casings should be about 10 inches long with openings about 4 by 4 inches. They should also be arranged to close with sliding doors L, as shown at L, Fig. 10. M in Fig. 13 shows a cast iron casing for the lower set of draft holes in which the openings should be about 8 by 13 inches. Th^ir position in the brick work is desig- nated M in Figs. 10, 11 and 12. N in Fig. 13 is a sliding door for the draft hole casings M, and they are designated N in Figs. 10 and 11. in Fig. 13 is a cast iron foundation washer which is built in the brick work on the bottom ends of the vertical bolts C. The ash pits P P, Fig. 11, should be about 2 feet wide and covered with loose floor planks so that easy access may be had to the ash pits for the purpose of opening or closing the lower Fig. 14 — Plan and Elevations of Kettle drafts, and also for removing the ashes from the spaces R R under the grates G G-. Fig. 12 shows the grates G Gr in position, and also the manner of laying the bricks between the draft casings M M. I indicates the pier on which the kettle rests. It will be seen that the brick work between the lower draft casings M M is built in a way which will allow all possible access to the grates G G from the ash pits P P. The walls along each side of the kettle should have a lining of fire brick extending from the grates upward to the coping plates A A, as shown in Fig. 11. Fig. 14 shows a kettle ni which the body is formed of one piece, with rivets placed where the fire will not affect them. While a kettle for general use built after this illustration is our preference for many reasons, it does not follow that the work could not be done in a kettle of some other shape. 26 GALVANIZING AND TINNING Figs. 15, 16 and 17 show the setting of kettles fired without grates and with only one set of draft holes. Fig. 15 is a sectional Fig. 15 — Section^ of Brickwork and KLettle at A A, Fig. 17 plan of the hrick work and kettle through 17 at A A. Fig. 16 is a sectional side elevation through Fig. 15 at B B. Fig. 17 is a sec- tional end elevation through Fig. 15 at C C. .'<2k; k Ci. *. ^' * n// <-^ ,„i J) Fig. 16 — Side Elevatiojn at B B, Fig. 15 Figs. 18 to 23 show construction of a simple and effective ar- rangement for drying eastings previous to dipping them in the molten zinc. Fig. 18 is a side elevation of a "drier" showing HOT GALVANIZING PLANT AND EQUIPMENT 27 furnace front with fire and ash pit doors. Fig. 19 is a longitudinal section of Fiar. 22 at C C. Fig. 20 is a lateral section of Fig. 22 Fig. 17 — Section at C C, Fig. 15 J l IL Jl IL 1\ \L 1 1 II IJ J \ I E n i \ r 3 Fig. 18 — General View of Furnace for Drying Castings at A A. Fig. 21 is a lateral section of Fig. 22 through B B, ghowing ash pits and grates. Fig. 22 is a longitudinal section of 28 GALVANIZING AND TINNING Fig. 21 through D D, and shows arrangements of flues. Fig. 23 is a longitudinal section of Fig. 21 through E E, and shows grate and fire box with fire brick lining. We give the method of setting kettles with and without grates for the reason that there is a diversity of opinion as to which is Secffon C-C Fig. 19 — Loivgitudijval Sectiotv" at C C, Fig. 22 ::iO- M^M^IMIMWW^M^^M: Fig. 20- Sscf/on /^-/t -Cross Section at A A. Fig. 22, Showing Flues the better method. Without discussing this matter pro or con, the author will simply say that he prefers a kettle fired without grates. Some claim that a grate fired kettle lasts much longer than one HOT GALVANIZING PLANT AND EQUIPMENT 29 4^^ p^' ^.4~f. Sect/on s-3 Fig. 21 — Vertical Section Through B B, Fig. 22, Showixg Furnace AND Flues A ^ Sec-r/or> O-o Fig. 22 — Plan of Drier, Showing Top Flues at D D, Fig. 21 30 GALVANIZING AND TINNING set without grates, as without grates the draft comes directly onto the side of the kettle, which results in burning it out much quicker than would otherwise be the case. Secr/on £-£■ Fig. 23 — Plan Showing Guate and Fire Box at E E, Fig. 21 Tanks for Acid Solutions and Water In our opinion, the best lumber for acid tanks is cypress, al- though some prefer the different varieties of pine. Most galvaniz- ers use wooden tanks for containing the cooling and rinsing waters. Water tanks made of boiler iron will give very good service, in fact they are more economical than wooden water tanks. Wooden tanks for holding the various acid solutions should invariably be put together with copper bolts, nuts and washers, and it is a good plan to line the inside of such tanks with rough boards that can be replaced when worn orut. These linings protect the inside of the tanks and will increase their life very materially. It will be found a good plan to coat the inside of wooden tanks intended for cold acid with asphaltum. The asphaltum should be heated as HOT GALVANIZING PLANT AND EQUIPMENT 31 hot as possible without danger of its catching fire and put on thickly with an old broom. When asphaltum is used in this way it is absolutely necessary to protect it with a rough board lining such as mentioned above. It was formerly considered necessary to line acid tanks with sheet lead, but of late years this is rarely done, as the use of lead linings makes the maintenance of acid tanks a very serious item of expense. If the tanks are properly constructed there is no necessity for lining with lead. ^^.^^^^^^:>^^^^^^^^^=;;^^^ <^l(^> WfW° r l©8 Fig. 30c — Details of Tumbling Barrel Equipment power at night, remove the cover, and allow enough fresh water to flow into the barrel to displace at least half of the solution, and leave it in that condition until morning, taking care that the valves do not leak, that the iron is completely covered, and that the water is not left running, as iron will rust in running water even if the water covers it. In rolling a batch of castings it will often be found that a black foam will rise to the surface of the solution when the bar- rel is opened. This is formed by the iron dust left on castings that are cleaned by dry tumbling, and it will also be found when WATER ROLLING, TUMBLING AND SAND BLASTING 57 preparing castings that have l)eon faced with foiUKlry facing of any sort. When this foam or scum is present, let water flow into the ])arrol, with the opening in a position that will allow the ohjectionable matter to float off. The first one or two batches prepared in a new barrel are liable to give trouble in tinning unless the inside of the barrel, with the shot to be used, is cleaned with a strong alkali solution. The simplest way is to put the shot into the barrel, and, after filling it about half full of strong, hot alkali solution, close the barrel and allow it to run an hour or more, after which the interior of the barrel and the shot used should be rinsed with plenty of clean water. It sometimes happens that castings are encountered which have a ground work of delicate design into which the sand has been burned. If such castings are placed in the rolling barrel with a good quantity of shot and given two or three hours' rolling in a solution of hydrofluoric acid and water, 1 part acid to ?5 or 100 of water, they will be cleaned very nicely. AYlien this is done let the hydrofluoric solution run out of the barrel before charging it with the regular solution of muriatic acid, sal ammoniac and water. The operator must bear in mind at all times that as a safe- guard against accident he must see that the valves on the rolling barrel are kept in good working order. These valves should be adjusted to open at a pressure of 40 pounds. If, by reason of a leak in any part of the barrel, gas is not generated the work will not tin properly. Do not approach the barrel with a light at any time when the gas is escaping, or at any time when the gas is being generated in the barrel. If after stopping the barrel it is found that the valves leak, as they may from becoming clogged, stop the leak, as the solution will escape, thereby allowing the work to oxidize. Badly oxidized eastings will not tin. The solu- tion contained in tank P, Fig. 51, is calculated to remove a light oxide, but castings that are heavily oxidized must be re-rolled. Storirxg the Castings After Tumbling As soon as the operator has determined that the castings are properly rolled for tinning he proceeds to dump the contents of the tumbling barrel into the receiving tank, located directly under the barrel. The cubic contents of this tank should be about one- third greater than the rolling barrel. From this receiving tank 58 GALVANIZING AND TINNING the castings should be removed to the storage tank designated C in Fig. 51. A good-sized coke fork is best for handling the castings from tank to tank, as it lets the shot or stars fall to the floor sejDarate from the castings. In placing the castings in the storage tank care should be taken to have those with depressions or cavities go under the water with the openings up. In other words, castings of a shape that would retain pockets of air under the water should be so placed that no air can be retained. If air is retained there will be a rusty place formed on the casting to which the tin will not adhere. The water in storage tank C, Fig. 51, will in a short time become charged with the acid solution from the rolling barrel unless it is changed frequently. If much acid is present in the water it will impair the action of the alkali solution into which the cast- ings i3ass directly from this tank. If a few jDounds of the alkali selected for use (caustic soda or soda ash) is added two or three times a week to the alkali solution, it will do its work properly for some time, although it is best to clean out the tank and make up fresh solution once in two weeks when it is in constant use. Cleaning Work with the Sand Blast While the art of sand blasting is old, its use in preparing mate- rial to be galvanized or tinned is comparatively new. Not so many years ago the process of tinning common gray iron was considered a great secret. As a matter of fact, there were only one or two concerns able to do it on a commercial ))asis, and their operation was confined to comparatively small castings. The methods employed were complicated and expensive. The use of the sand blast has made the tinning of gray iron a simple matter, especially in the case of unusually large or fragile castings. While the best commercial appearance is still obtained by use of the wet rolling Ijarrel, there are many kinds of castings that it is impracticable to prepare in that manner owing to their size or delicate construction. To obtain even fairly economical time re- sults with tlie water rolling barrel it is necessary to have it re- volve not less than 35 or 40 revolutions per minute, and even with this speed it takes no less than 3 hours to jDroperly prepare a batch of castings for tinning, and often a much longer time. On the other hand, the sand blast barrel will prepare a similar batch of castings in from 15 to 20 minutes. WATER ROLLING, TUMBLING AND SAND BLASTING 59 Cold galvanizinfl^ as well as Sherardizing can he done on work coming direct from the sand hlast, practically eliminating the use of acids, and a much brighter coating is obtained. As acid works more or less into castings in the cleaning process, even its partial elimination is another distinct feature in favor of sand l)lasting for any process of coating. Another feature in favor of the sand blast is that old work can be thoroughly and quickly cleaned by this method. It is our prac- tice to use a pressure type of hose machine in the cleaning, for hot galvanizing of -old anchors, old anchor chain, and in fact old material of a heavy nature of almost every kind. TRADE MARK ATENT APPHe Fig. 31 — A Simple Two-hose Type of Sand Blast The large variety of shapes and weights of castings makes it impossible for us to give a definite time for cleaning by this method. In a general way we will say that such articles as food choppers, saddlery hardware, etc., when cleaned in a sand blast barrel will require from 10 to 15 minutes, the consumption of free air per minute being 135 cubic feet at 60 pounds pressure, while heavier castings or old work that is badly rusted may re- quire a considerably longer time. For steel castings and forgings a higher pressure will give the best results. This applies to both the hose and the automatic machine type. The value of the sand Ijlast for plating plants in general is only beginning to be appreciated, and while it does not entirely elimi- nate the use of acids, it goes a long ways in that direction and is one means of making working conditions in a hot galvanizing plant, which are bad enough at best, much more endurable. That the subject of sand blasting and the apparatus referred 60 GALVANIZING AND TINNING to may be better understood, we refer to the same herewith more full,y. The term sand blast in its simplest form means a stream of sand and air under pressure. In this condition the sand gather- ing velocity as it is carried along with the air strikes the object in its path with great force. The cutting action of the blast is greater when the blow is slantwise rather than straight against the object. A simple form of sand blast de- vice can be made from a Y pipe fit- ting, using regular stock fittings to complete the job, but the action of the lilast would destroy the several parts after a few hours' service. Far better satisfaction will l^e obtained by purchasing an outfit like that shown in Fig. 31. One popular and service- able suction sand blast outfit consist- ing of cast iron nozzle with remov- able air tip, easily replaceable hard iron blast tip, air valve, sand hose, sand blast helmet and gloves, costing not over $25.00. In this type of ap- paratus the end of the sand hose is placed in a pail or pile of sand and the air turned on at the nozzle. The next, and most widely-known system, is the pressure or single hose type, Avhere the sand is placed in a closed tank and air admitted to the same under the same initial pressure as that to be used in the blast. In this machine, see illustration, Fig. 33, there is a mixing chamber at the bottom into which the sand is fed through a valve, and the sand mixing with the air which is ad- mitted through a separate opening is discharged through a single hose. At the outer end of the hose is a hard iron nozzle holder, having means for replacing the hard iron tip which wears away very rapidly. The hose must be specially made for sand blast use, the core being composed of practically pure rubber. The present tendency in sand blast practice is toward higher air pressures, say 60 pounds, using smaller nozzles and hose. It is easier for the operator to handle this apparatus than the more cum- FiG. 32 — Single Hose Type Sand Blast Apparatus WATER ROLLING, nTMBLING AND SAND BLASTING 61 bersome where lower pressures are used. The maintenance cost is also less. A very satisfactory outfit consists of tank, one-inch hose and :^-inch blast nozzle, the consumption of free air at 60 pounds pressure being about 67 cubic feet and the power required to compress the air approximately 10 H. P. The present tendency is to get away from the hand operated blast owing to the reluctance of men to follow this work continu- ously. Accordingly self-contained, dustless machines have l)een designed which handle tons of material in a day. These are made in the form of a rotary table, a sliding table or planer type and revolving barrel. Sand Blast Rolling Barrel For cleaning small and medium-sized castings, forgings, etc., the sand blast rolling process is to be preferred in many ways. A popular type is shown in Fig. 33. The self-contained feature confining the blasting operation and recovery of abrasive to the inside of harrel makes it a dustless, as well as a more efficient, method. The process is entirely automatic after the work is placed in machine, and the operator is at liberty to attend to other matters if he so desires. Unlike the tumbling mill running approximately 40 R.P.M., the sand blast rolling barrel revolves 2 R.P.M., making it possible to clean fragile castings without rounding the corners, etc. This method has proven valuable in cleaning letters or orna- mental design work on castings, the slow movement of barrel pre- vents defacement and the blast removes all dirt and cleans them perfectly. The inner barrel B in Figs. 34a and 34b is made from heavy sheet steel, one-half inch thick, having a number of holes in same which allows the sand, after coming from the blast nozzle F and striking castings, to fall through at bottom of inner l:)arrel B to outer shell A. As the barrel revolves (direction of arroAv) the sand or grit falls into buckets C and is carried to the top of the l)arrel, where, by its own gravitation, it falls back through the holes which it entered, passing through screen E, removing all foreign sub- stances, into sand-hopper D, ready to be used again. G is the exhaust pipe for removing dust, H the slide valve in hopper, I the cast steel hopper support, J the petcock for drip, K the compressed air inlet, L the exhaust outlet. 62 GALVANIZING AND TINNING While it is possible to do sand blasting in an open space, yet the dust arising from the operation is so objectionable that it is customary to provide a room for this work, the same to be con- nected to an exhaust fan having capacity siifficient to change the air in the room not less than five times every minute. Fresh air Fig. 33 — Self-contained Sand Blast Barrel must be admitted at a point as far distant from the exhaust con- nection as possible. The smaller the room the better, for less power will be required to run the fan. The walls of the room are usually of wood, nailed on and easily rencAved as occasion de- mands. A most satisfactory lining is discarded fire service hose, which should be sjDlit and, with the inner side facing out, nailed to the siding. The operator must be provided with a helmet and should also use a respirator. Leather gloves are also a necessity. WATER ROLLING, TUMBLING AND SAND BLASTING 63 Fig. 34a — Front View, Showing Details of Sand Blast Barrel 6 i «t .A ~-4?f U-'-: ©I 4:>®::~v ■S-F J_©i] ^yt:^^--^-^--iS= _^_ ^_B._____^ Fig. 34b — Side View, Showing Details of Sand Blast Barrel 64 GALVANIZING AND TINNING It is always important to use a good hard, washed quality of silica sand, passing the same through an 8 or 10 mesh screen for general work. The sand must always he dry, likewise it is im- portant that the air should he dry. In the case of a pressure or closed tank system, the very strictest attention must he paid to these particulars. Diamond Grit and Steel Shot Used as Substitute for Sand In many instances sand is being replaced by steel grit or chilled shot. Both have their particular field, the shot No. 5 Globe, or 16/30 Harrison, giving most excellent service in connection with the sand blast barrel. As this class of material is expensive, it must not be allowed to go to waste, good floors and tight rooms being required when used with the hose machine. Diamond grit and steel shot have proven a very satisfactory sub- stitute for sand, though opinions difi^er as to their relative value due to local conditions. Diamond grit is angular in shaj^e and otherwise known as crushed steel ; its edges are sharp and it has all the cutting qual- ities of sand. There are several advantages in using this material Avhich are due to its slow deterioration. It does not break up like sand and, therefore, may be used many times before replacement is neces- sary. It is dustless in itself and naturally eliminates the dust that would otherwise be generated by the use of sand. This material is made in a number of sizes, enabling the user to adapt a size satisfactory to the finish desired. Steel shot carries the same general advantages as grit, though, ])eing glol3ular in form, its actual cutting qualities are not so severe. Its action is more of a peaning effect ratlier than cutting, and castings cleaned have a tendency toward a shiny appearance rather than the sand blast finish as produced by sand or grit. Preparing the Cleaned Work for Dipping To enable the zinc to unite with the work properly, a solution of muriatic acid and water is used. This not only serves as a flux, but removes any rust that has formed on the work in the operation of inspection. It will naturally be inferred from the above that all work should be carefully inspected to determine whether the cleaning process has been properly performed before it is subjected to the muriatic acid treatment. While the char- WATER ROLLING, TUMBLING AND SAND BLASTING 65 actor of this muriatic acid dip may be varied, we use ordinarily a solution composed of one-half acid and one-half water, liquid measure. Some galvanizers add 1 pound of sal ammoniac to a gallon of the mixture, but, in inour opinion, the advantage gained does not warrant the expense. Tank C, Fig. 3, is for containing this mixture. Drying the Work From tank C, Fig. 3, or, in other words, from the muriatic acid, the work is taken to the place provided for drying it. The position of this drying arrangement is designated E in Fig. 3. A drying arrangement for a limited amount of work may be the plates covering the fires that heat the kettle. If the work to be handled only amounts to a few hundred pounds per day, it can be dried in this way. If, however, the amount of work necessitates keeping the kettle in constant operation, a drying arrangement such as shown in Figs. 18 to 23 should be provided. Sheets and pipe should be dried in an oven. The location of this drying arrangement is a mere matter of choice. In Fig. 3 we show it located at one end of the kettle. The castings or other work to be dried prior to galvanizing are placed, while still wet with muriatic acid, on the heavy cast iron top plates of this dryer directly over the fire box, where they are allowed to remain until thoroughly dry, when they should be passed to the end of the dryer farthest from the fire to stay until needed. If allowed to remain on the hottest part of the plate for too long a time, the work will become too hot and the acid burned off, which will necessitate re-dipping them in the muriatic acid before they can be galvanized satisfactorily. When properly dried, the salts formed by the muriatic acid should show on the surface of the work in the form, of a white powder. Work that has been prepared for dipping and dried should not be allowed to get cold; and if more material has been prepared for dipping than can be finished, it should not be allowed to remain on the dried over night, but returned to the water tank. It should be remembered that rusting is merely oxidation; and freshly cleaned surfaces readily attract free oxygen from the air. While moisture assists rapid oxidation, a total immersion in water is an admirable preventative of rust- ing. It should, of course, be re-dipped in the muriatic solution and dried again before putting it into the galvanizing kettle. CHAPTER Vn Hot Process of Galvanizing Filling a New Kettle WHEN the galvanizing kettle has been properly bricked in ready for use considerable care must be exercised in filling it with spelter to prevent the kettle from being ruined when the fires are started. In the first place, a suffi- cient quantity of lead should be put in the kettle to insure a depth of not less than 6 inches when molten. If the kettle is more than 30 inches deep, lead should be introduced to insure a depth of at least 8 inches. When dross forms in the process of galvanizing this lead serves as a "cushion'^ for it to rest upon. Lead and spelter do not mix under these conditions, the lead being of a greater specific gravity, remains at the bottom of the kettle, and no amount of stirring can cause any considerable quantity to be permanently mixed with the spelter. As a matter of fact, if lead is present in the spelter itself, as it sometimes is, most of it settles to the bottom of the kettle when the sj)elter becomes melted. The lead not only serves as a cushion for the zinc dross to rest upon as it forms, but greatly facilitates the removal of the dross when necessary. It is also a protection for the bottom of the kettle and keeps the spelter and dross even or slightly above the fire line, as it should be. In filling the kettle with the slabs of spelter, place them on edge in such a way that their flat surface will lie as closely as possible to the sides of the kettle. By exercising a little ingenuity the slabs can be placed so as to practically cover the sides of the kettle. This method of packing the slabs will materially lessen the danger of burning the kettle at the first firing, as there is cold zinc against all the heated surface. These slabs should also be so arranged that, as the outside ones melt, those next to them will be forced outward against the sides of the kettle. To the inexperienced this may seem an unimportant matter, but we can assure the reader that many kettles have been ruined at the first firing through failure to give proper attention to these details. 66 HOT PROCESS OF GALVANIZING G7 When a galvanizing ])lant has an equipment of more than one kettle it is a good plan to bail molten metal from a kettle already in use into the one that is being put into operation for the first time, after the slabs have been properly arranged, and before starting the fires. EefiU the kettle in operation with new metal, replacing what has thus been taken out. Firing a New Kettle In heating up a kettle for the first time great care should be exercised that the work is not hurried. Under no circumstances attempt to melt out a kettle for the first time in less than 36 hours. Until the spelter commences to melt the fuel should not be allowed to attain a depth of more than 12 or 15 inches in the fire boxes, and the slides that close the draft holes should be so regulated that the fires will not burn too strongly. We repeat that plenty of time should be taken to melt the metal in a new kettle the first time; otherwise, one may be put to heavy expense for replacing a burned out kettle, to say nothing of the loss result- ing from over-heating the zinc. As the metal melts the depth of fuel may be increased, but it should never be more than 3 or 4 inches above the molten metal in the kettle. Of course, it is rather difficult to determine just the depth of the molten metal, but it is easy to be on the safe side even if a longer time is taken for the "melting out" operation than is actually necessary. The Temperature of the Zinc The question of the temperature of the zinc is the most difficult to learn; for the reason that different kinds of work demand that different temperatures be maintained. A kettle of zinc at the proper heat for wire or wire cloth would be much too hot for galvanizing castings of either gray or malleable iron, while with the metal at the proper heat or heavy work, it would be impossible to coat small work properly, even if the material was the same. Large pieces demand that the galvanizing bath be maintained at a low temperature. Small work that is strung on wires for dipping in the galvanizing bath demands a higher heat than heavy pieces. Work that is galvanized in baskets often requires a still higher heat than work that is strung on wires, as hereafter described. We shall give the degrees of heat that a pyrometer should indi- cate when different kinds of work are being done, basing the rules 68 GALVANIZING AND TINNING given on the supposition that Avhen the metal is barely melted — that is, at a temperature that would just keep it in a liquid state, the pyrometer indicates 750 degrees of heat. We shall also give the best rules possible for determining the proper temperature by the appearance of the metal and by other signs. Large gray iron castings require that the metal be at the lowest temperature possible and still have it liquid. At about this tem- perature it will be silver white in color, will burn sal ammoniac slowly when thrown on its surface, and when a skimmer is passed over its surface the oxide will be slow in appearing. With the metal in this condition the pyrometer should indicate about 800 degrees of heat. This temperature is also suitable for galvanizing very thin castings that are intended to be "spangled" or to have a crystallized appearance — for example, sinks and like work. For work that is drawn through the clear metal the pyrometer should indicate not less than 850 degrees. At this temperature the metal should have a slightly bluish cast, burn sal ammoniac moderately quick and show the oxide in a few seconds after the skimmer has been passed over its surface. This temperature is about right for galvanizing wrought iron pipe, the cheaper grades of sheet iron and goods made from it, such as coal hods, ash cans and chamber pails. Heavy malleable iron castings will also coat nicely at this heat. For small work, such as nails, and in fact, almost any work that is done in baskets or strung on wires and drawn through flux, the pyrometer should indicate not less than 900 and not more than 925 degrees F. The metal at this heat should burn sal ammoniac quickly and oxidize quickly, and will be quite blue in color. This temperature is about right for sheet steel and articles made from it, as well as steel pipe. We wish to impress upon the reader that these rules for tem- perature are based on the supposition that the galvanizing bath is composed of strictly Prime Western Spelter that has not been subjected to overheating, and that the bath is practically fresh by reason of recent starting or recent drossing and re-filling with new metal. If "Eemelt" spelter is used exclusively, or even par- tially, the proper degrees of heat can onl}^ be determined by ob- servation and experience. Therefore, we repeat that no hard and fast rules for operating the bath exclusively by the pyrometer can be given. HOT PROCESS OF GALVANIZING 60 Dipping the Work in the Molten Zinc We will describe the manner oL' handling several different ar- ticles as a general guide for dipping all kinds of work. Consider- able skill is required to bring work out of the molten metal and cool it in such a manner that the surface will be smooth, free from blisters and without lumps of surplus metal attached. Before commencing to dip the work, cover part of the surface of the molten zinc witli a sal ammoniac flux to keep the oxidized metal from adhering to the material. To prepare this flux, sprinkle a few'handfuls of sal ammoniac on the surface of the bath, and as soon as it is melted add a few drops of glycerine. This will cause the flux to thicken somewhat and will prevent it, in a measure, from covering the entire surface of the metal. The glycerine also causes the flux to remain stationary, so that when the operator is ready to draw work from the bath the flux will not cover the space he has cleared with his skimmer for so doing. The tool desig- nated E in Fig. 25 is a skimmer used for clearing the surface of the metal before drawing work from the bath. The flux not only prevents the zinc from oxidizing, but also as- sists the metal in adhering quickly and evenly to the work. Keep the flux fresh by adding more sal ammoniac from time to time as required. We will suppose an article to be dipped is a cast iron sink or some similar thin casting, in which case have the metal at the temperature first described under the heading "The Temperature of the Zinc." After satisfying himself that the casting has been heated until it is perfectly dry, the operator catches the article with a pair of tongs and plunges or drops it as quickly as possible, without causing the metal to spatter, through the flux into the molten zinc. He must keep the article beneath the surface until it becomes as hot as the zinc itself. After the article has been in the bath a few minutes it should be rinsed or washed around in the metal in such a way that the flux will come in contact with all parts of it. AVhen the article is thoroughly coated clear a space on the surface of the molten zinc with the skimmer, sprinkle on a little dry white sal ammoniac, and draw the article slowly from the metal. In performing this operation catch the article with the tongs in such a way that the part they grasp will be the last to leave 70 GALVANIZING AND TINNING the zinc. Do not lift tlie article clear of the metal with the tongs you use in the hath, lait provide a second pair to complete its removal and to handle it until cooled. Hold the article in such a position as to cause the surplus metal to flow to one point, and just as the drop starts to harden remove it with a stiff hrush or an old file. Expose the article to the air until crystals appear, and then Ijrush it lightly with a brush wet in clear water. Do not dip the article in water, especially if it is a very thin casting, as that would be quite likely to l)reak it, and the coating would not be as bright as if left to cool gradually after l)rushing with the wet brush. Thick, heavy castings may be dipped in water at once on removing them from the molten metal. Coal hods and similar goods of sheet steel or iron only need be left, in the bath a few seconds. The flux through wliich they pass should be confined at one end of the kettle ])y a piece of sheet iron long enough to go across the kettle from side to side. This is called a "flux guard," and it should enter tlie metal about 2 inches, with the upper edge as high or a little higher than the sides of the kettle. In galvanizing sheet metal ware the flux should be made to foam up nearly to the top of the kettle l)y using glycerine. The goods should be passed through the flux under the guard to the end of the kettle that is kept clean. In passing the article under the flux guard, keep the opening up so that none of the flux will be carried along with it. Eemove the article from the metal in the way described for sinks and similar articles, but do not sprinkle the clear surface of the zinc with sal ammoniac. Allow the work to cool in the air. If any particles of flux have adhered to the work while drawing it from tlie molten metal, remove them with a wet brush while the article is still hot. Some articles can be galvanized to best advantage by stringing them on stout wires about 2 feet long. When this method is em- ployed, string on a number of the pieces and then bring both ends of the wire together and clinch them securely. For suspending work in the metal whicli is strung this way, use a hook, shaped in the form sliown by Fig. 25 and designated G. Provide several of these hooks, so that a batch may always be ready for removal from the kettle when the previous one has been removed. A piece of f-incli round iron, bent in the shape of the letter S, may be used to remove the strings of castings from the hooks, and also foi handling them until they are cooled. The wires C and D, Fig. 25, HOT PROCESS OP CALVANIZINO 71 are also intended for stringijig small articles for the purpose of dij)ping them in the molten metal. In handling small articles on any of these wires after they are drawn from the metal, use a shaking motion that will free them of surplus metal, and also prevent their sticking to each other when plunged in the water. Some practice will be necessary before this can be done properly. It is a good plan to warm the cooling water slightly for cooling some articles, and to have a thin film of oil on the surface. Small articles strung on wires may be drawn from the clear metal after sprinkling on a small quantity of powdered sal ammoniac, or may be drawn through a clean, thin flux of sal ammoniac, to which a few extra drops of glycerine have been added. If the latter method is used, as it should be if the articles are such as are liable to rub and stick together, oil should not be used on the cooling water. Small work that cannot be strung on wires may be galvanized in a wire or sheet iron basket. We have already described these, and they are designated in Fig. 25 as A and B. When baskets are employed, the flux should be of such con- sistency that it will flow freely among the work. A block of iron should be placed on the brickwork beside the kettle in such a position that the operator can rest the handle of his basket across the block with the basket hanging over the kettle. Using this block as a rest, the operator should shake the basket up and down sharply for several seconds after if has been drawn from the bath to free the work of surplus metal, and when this is accomplished he should dump them into the water to cool, after which, dry them off by dip- ping in boiling water and throwing them into dry sawdust. Nails or tacks may be shaken out of the basket onto an iron plate, placed at an angle, over a tub of water to separate them. The plate should be inclined sufficiently for the work to slide into the water readily. Considerable difficulty is experienced in removing the surplus zinc from small articles, such as nails, tacks, bolts, nuts, washers, rivets, screw eyes, screws and sheet metal or wire specialties when hot galvanizing them imless mechanical means for accomplishing this purpose can be employed. This fact has been responsible for the invention of several different machines and devices intended to remove the surplus metal after the articles have been taken from the molten zinc. Notable among these is the "Porter Ma- 72 GALVANIZING AND TINNING chine/' which, according to the inventor, will handle anything from a small tack to a 60-penny nail at the rate of from 2000 to 3000 pounds per hour. This machine removes all unnecessary surplus metal by means of beaters or fans, cools the articles with- out their coming into contact with water, and automatically de- livers them into kegs or boxes ready for shipment. As this ma- chine occupies considerable space and has a large capacity it is best adapted to the large producer and has been used by such con- cerns for some time past. Another means of accomplishing the same result is found in the "Watrous Machine," which utilizes the action of centrifugal force for throwing off the surplus metal while it is still molten. This machine is claimed by the inventor to have been in successful operation for some time by several manu- facturers. Various other machines designed for the same purpose are claimed by their enthusiastic inventors to attain remarkable re- sults, but the prospective purchaser of any such device or machine should thoroughly investigate the matter before making a decision, as any of them may have limitations or objectionable features which can best be learned from some one other than the inventor who has had actual experience with the device. Eemoving surplus zinc is not always the only consideration when galvanizing small articles, though many inventors seem to lose sight of the fact. For this reason, the cost of production (when considering the merits of a machine or process) should always be given considerable attention, and cost figures, obtained under actual working conditions and not made in round figures from estimates or unconfirmed reports, should be secured for careful consideration. CHAPTER VIII Galvanizing Sheets SHEET iron, wire, wire cloth and poultry netting are gal- vanized by being passed through the zincing' bath mechani- cally, and as the mechanical means employed are so varied and complicated we shall not attempt to illustrate them. The galvanizing of these materials is carried on principally by large manufacturers who produce the finished article from the raw material, and the galvanizing is simply one process of manu- facture. As a brief description of galvanizing sheets by hand may be useful to some, we will describe the old hand method in use before the introduction of mechanical methods. The hand galvanizing of sheet iron requires the use of a kettle long enough to accommodate the sheet and deep enough to permit of its being dipped in the bath without interfering with the dross in the bottom of the kettle : consequently, a kettle for sheets must of necessity be not less than 8 feet 6 inches long by 4 feet deep, and it should not be less than 18 inches in width, and a better width is 2 feet. As it is necessary to pass the sheet into the molten metal through a flux of sal ammoniac what is known as a "flux guard'^ is employed. This flux guard should be made of T-iron, to which an iron plate can be riveted so that when the arrangement is placed in the bath the guard eft'ects a longitudinal division of the metal. This flux guard should be wide enough to go under the metal 2 or 3 inches when the metal is at its lowest working height. After a sheet has become thoroughly coated it is pushed to the side of the kettle that has not been covered with a sal ammoniac flux and withdrawn from the metal with the aid of properly shaped tongs attached to a light single block and fall. If the pickling and inspection of the sheet has been properly done the coating takes place without the usual rinsing or washing through the sal ammoniac flux floating on the surface of the molten bath; but unless this has been properly done, it will be necessary to wash the sheet through the flux until a perfect coat- ing has been obtained. 73 74 GALVANIZING AND TINNING In the hand dipping method of galvanizing sheets, a simple arrangement was used that permitted the ojierator to transfer the sheet from the side of the l^ettle where it entered the hath to the opposite side where it was withdrawn, and also permitted the edge of the sheet being lifted, semi-automatically, just high enough out of the metal to permit of its being readily seized with the tongs used for withdrawing it from the bath. It was the practice in some plants to allow the coated sheet to form crystals by cooling in the air, after which the sheet was plunged into a bath of cold water and dried oil in sawdust. When it was desired to have a bright plate without the crystals the sheet was plunged into the water immediately after it had been drawn from the molten metal. This prevented the formation of crystals and, as stated, produced what was known as bright galvanized sheets. Among the old English galvanizers it was the practice to carry a clean flux of sal ammoniac on the opposite side of the flux guard from which the sheet entered. This prevented oxidation and was the means of producing a somewhat thinner coating. It was also the practice of some operators to cover the metal on the side of the flux guard from which the sheet was drawn with foundry sand or coke dust. Mr. James Davies, an English authority on galvanizing sheets, describes in his book, entitled "Galvanized Iron, Its Manufacture and Uses," a very practicable and simple mechanical device for the galvanizing of sheets. His device consists of a strong square iron frame in which two rollers work. The rolls are made of hammered forgings and turned. He gives the usual size as 3 feet 6 inches long by 9 or 10 inches diameter. The frame and rolls are suspended from l)ars placed in the bath at such a depth that the rolls are completely immersed in the metal, with the center of the rolls from 14 to 15 inches below the surface. The rolls have a hammered wrought iron pinion on the end of one and two wrought iron pinions at the other end, and are driven by another wrought iron cog wheel. The driving shaft should have a four- cone pulley with a corresponding cone pulley overhead for vary- ing the speed according to the thickness of the sheets, as a thin sheet takes less time to coat than a thick one. With this arrange- ment what is known as a flux box is placed on the entrance side of the bath and one on the exit side of the bath. Erom these flux boxes guides are arranged which are removed when the day's GALVANIZING SHEETS 75 work is finished. Tlie sheet goes into the flux box in the wet state and as it emerges from the flux box on the other side it is seized by the operator with a pair of self-acting tongs which are attached to a rope running over a pulley. The action of the rolls in the bath keep up a constant circulation of the metal, which, in a measure, prevents the dross from solidifying. In addition to this comparatively simple method of galvanizing sheets automatically, we have what is kno-\vn as the "Heathfield's Patent Process/' the advantages of which are best described in the patentee's own language, which is, in part, as follows: "One man and one boy are sufficient to run the machine, and their combined labor will turn out far more galvanized sheets per day than a much larger number of men can do by any other process. "The machine will turn out with sufficient lal^or 12 tons or more of galvanized sheets assorted, 14 to 30 gauge or thinner, per turn of 10^ hours, and with a good dipper will sometimes do as much as 11 or 12 tons per turn of sheets assorted 26 to 30 gauge; while 8 English tons is a very moderate average in a turn of 10^ hours for sheets of these latter thicknesses. "The machine will do any thickness from 14 to 30 gauge or thinner, any width up to 4 feet (or wider if a large enough ma- chine is su23plied) and any required length. "As the pot is only 2 feet 8 inches deep, and holds only about 12 tons of spelter (^inc), the very large output, compared to the quantity of spelter in a molten state, reduces the dross made per ton of sheet below that made by any other plan ; the pot, of course, being pushed to its maximum, and worked night and day. "No oxide is made while the machine is at work. "The quantity of muriate of ammonia used per ton of sheets is very small. Fourteen pounds, or less, will suffice to galvanize one ton of sheets, 28 gauge thick, while stronger sheets take propor- tionately less. "The coke bill is small. If the pot is kept fully at work, six tons of ordinary gas coke of fair quality will keep the pot at work a week, including firing it on Sundays. "The quantity of spelter used per ton of galvanized sheets made is greatly reduced, while the appearance of the sheets is much im- proved, and they leave the machine ready for use, without any subsequent brushing, washing or drying. 76 GALVANIZING AND TINNING "The following are the approximate quantities of spelter de- posited on the sheets, in the manufacture of one ton of galvanized iron by the Heathiield patent machine; the various gauges being calculated at the number of galvanized sheets per ton, which it is usual to supply in England: 16 18 20 24 26 28 30 gauge 120 140 195 245 325 350 420 pounds "In the very light gauges it is possible to use sheets a gauge stronger than can be used in the ordinary process, and yet pro- duce the same number of galvanized sheets i^ev ton as is customary by the old plan. "This saves considerably the cost of black sheets on 28, 29 and 30 gauge galvanized." In addition to the Heathfield process we have the Bayliss patent process. The patentee makes the following claims for his process : "The patentee claims that this method dispenses with a con- siderable amount of manual labor. The patentee passes the sheets, after being pickled, through a pair of cold rolls upon which a stream of water is continually flowing. The object of this is to impart a fine smooth surface to the .sheets which have been roughened by the pickling process. From the cold rolls the sheet passes onwards towards the bath which it en- ters through a pair of rolls fixed on the brickwork of the gal- vanizing bath. It then passes through a guide fixed below the surface of the metal, and finally emerges through a layer of sand on the surface. The sheet is then seized by a pair of rolls having studs inserted at intervals which meet and grip the sheet. The sheet then passes on by means of an endless chain band to a set of revolving brushes which brush off any adhering particles of sand.^^ CHAPTER IX Galvanizing Wire, Netting and Tubes WIRE, wire cloth and poultry netting are galvanized prac- tically automatically. In galvanizing wire cloth and poultry netting it is necessary to divide the molten metal longitudinally with a flux guard of the character descrihed for gal- vanizing sheets. The side of the hath where the material enters should he covered with a heavy flux or sal ammoniac, and the side where it leaves the metal should he covered with coke dust to a Fig. 35 — Automatic Wire Galvanizing Machine depth of several inches. The coke dust must he constantly sprinkled with water while the material is passing through it. The best means to accomplish this is to have a perforated water pipe of the required size constantly discharging water in sufficient quan- tities to keep the coke dust on the surface of the metal well moist- ened. The operation of drawing the work through the molten metal is performed by a revolving drum so constructed as to per- mit of the ready removal of the roll of wire cloth or poultry net- ting after it is galvanized. Where wire is being galvanized, several strands are passed through simultaneously, and the speed varies according to the gauge of wire being handled. A description of a device that is claimed to be an improvement 77 78 GALVANIZING AND TINNING for galvanizing wire cloth recently appeared in The Brass World, as follows, and it is illustrated by Fig. 35. An Improvement in Galvanizing Wire Cloth "An improvement in galvanizing wire cloth has been patented by George M. Wright. The cloth is drawn from a reel down through the bath of molten zinc, contained in an iron kettle. At the bottom of the kettle are roller guides, as shown in the illustra- tion. The cloth then passes through a mass of charcoal 9. At the same time a lateral motion is given the cloth by a device shown. The charcoal removes the surplus zinc from the top and sides of the wires of the cloth, but on the l^ottom of the meshes it fails to brush it off. By giving the cloth a lateral motion, however, this surplus zinc on the Ijottom of the mesh wires is scraped oft'." The Influence of Galvanizing on the Strength of Wire As there are enormous quantities of galvanized wire used, the effect of hot galvanizing on the strength of wire may be of interest to some, and we cite the folloAving from Tlie Iron Age. "At the International Congress of Metallurgy, held at Dussel- dorf recently. Dr. Heinrich Winter of Bochum read an elaborate paper on tiie above su1)ject. Particularly in mine installations is it important to protect the hoisting ropes l)y a suitable rustproof covering. Coating with zinc has been found to answer the pur- pose admirably, for the protection afforded depends upon the for- mation of a couplet in which the zinc of the galvanized iron forms the electro positive element and the iron the electro negative, when the material is immersed in water or other fluids. The zinc takes up oxygen, gradually forming a zinc oxide, while on account of the evolution of hydrogen the iron remains inert even if the con- tinuity of the zinc coating is slightly broken. "In the process of hot galvanizing there is no question, how- ever, but that the strength and particularly the resistance to bend- ing and torsion are considerably affected, and the purpose of the paper in question was to determine the degree of this action. Many theories are given regarding the loss of tensile strength. Poor material is cited, but tests have shown that even the best of mate- rial suffers loss. Again, the steel is supposed to have been 'over- drawn,' but microscopic tests do not show signs of this in mate- rials losing 38 per cent, of resistance to torsion effects. Finally, GALVANIZING WIRE, NETTING AND TUBES 79 irregularity in the coating of zinc is supposed to change the re- sistance to torsion, by obstructing the power applied, in varying degree in the test piece. This also will not explain the situation, for many wires with uneven coats of zinc showed practically no deterioration in this regard. How Tests Were Made "To study the matter carefully, the first thing was to note whatever changes might be produced by the drawing down of the billet to wire. Twelve test pieces were therefore cut from the material from the original billet down to the actual wire, pickled and galvanized, but not annealed. These sections represented the various stages through which the material went, and were etched by immersion in a copper-ammonium-chloride solution (1:12) for one minute each, the copper deposited being carefully wiped off with absorbent cotton while under water. The lighter outer zone as distinguished from the darker inner zone, showing segrega- tion, could be followed plainly through the whole series made from this billet. Further etching with an alcoholic solution of picric acid (1: 25) for 15 minutes indicated that the grain of the inner higher phosphorus zone was larger than the outer one with lower phosphorus. The results of the physical tests on the material showed the usual phenomena, an increased ultimate strength, with brittleness to a point to almost wipe out the power to twist it in the final wire before further heat treatment. "In order to not disturb the zinc layer in making sections for polishing, the wire was first cleaned carefully Avith alcohol and ether, placed in a solution of copper potassium cyanide, and a weak current applied to coat it with copper. It was then washed with alcohol and ether, and finally melted into Eose's alloy, which on account of its low melting point gave a perfect protection for the galvanizing coat, and yet did not alter the miscrostructure of the material. Finishing up the polished sections with a very little rouge on parchment paper with a 2 per cent, solution of ammonium nitrate for five minutes, thus etching them, gave excellent results. With 125 diameters enlargement the makeup of the section is plainly shown. A dark band for the zinc, light for copper and black for the Eose metal, with lighter color for the steel. A sepa- rate band may be distinguished between the iron and the zinc coat. 80 GALVANIZING AND TINNING Absorbed Hydrogen Gas Does Damage "This material^ it should be remembered, was pickled before gah^auizing. Hence many investigators brought back the brittle- ness of galvanized steels to an absorbed hydrogen from the acid bath. This absorbed gas can, therefore, do considerable damage. Further investigations, however, have shown that heating the steel up to 250 degrees F. for four hours removes this effect entirely. Hence, inasmuch as the microscope does not show any indications of an iron hydroxide either there remains only the theory that between the zinc and the iron there is a layer of an iron-zinc alloy, formed either because the wire was left in the zinc bath too long in contact with the zinc, or that the bath was too highly over- heated. That such an alloy exists is well known, every galvanizer being worried by large amounts of 'dross,' which contains 3 to 5 per cent, iron, and is a very brittle material. On the other hand, in order to get the zinc coat to stick to the iron, it is necessary that such an alloy be made with the iron, the composition varying from high zinc at the contact to no zinc a little distance into the iron, as was clearly shown by Sherard Cowper-Coles. "A study of the structure of the material before galvanizing shows that where this is large grained and easily to be penetrated, much zinc gets in. Even where the microscope does not show the layer of the zinc-iron alloy, it is undoubtedly there as a very fine one, and depending upon the extent of this layer will be found the phenomenon of loss in power to bend and twist when taken in coimection with the change in structure through the heat treat- ment. It is well known that with soft steels the elasticity is changed with temperatures ss low as 750 degrees F., but it also takes some time to do this. Hard drawn steel would consequently become softer by remaining in the bath longer, but this gain will quickly be offset by the formation of a heavier layer of iron-zinc alloy. "The conclusion of the paper is that the wire industry is per- fectly capal)le of furnishing galvanized wire which has not suf- fered seriously as to its physical j^ropcrties, this being a question of proper practice in regard to removal of damage done by pick- ling, and proper bath temperature and time of the wire remaining in it. It is, therefore, necessary to treat the wire before galvanizing to remove the hydrogen absorbed and to regulate the temperature of the zinc bath between close limits. The latter is not easy, as GALVANIZING WIRE, NETTING AND TUBES 81 there are difFiciiltics in pyroinetry and also in the proper firing where many wires are passed through constantly with consequent irregular lowering of the temperature." The Automatic Galvanizing of Tubes Iron and steel pipe and tubes are hot galvanized in large quan- tities annually, and large tube manufacturers have, of course, adopted mechanical means as far as possible for handling their product through the galvanizing process. Many ingenious de- vices have been invented and many of them are patented. Such a device was illustrated and described in The Iron Age recently as follows : "An arrangement that has been in successful operation for the last three years at Laurahiitte, Upper Silesia, for the hot galvaniz- ing of tubes, is described I)y Engineer G. Buchert of Laurahiitte. Fig. 36 shows the details. The tube a is drawn out at one end of the zinc bath & and passed through the arrangement c for remov- ing the excess spelter from the outside and smoothing the surface. It is gripped in tongs attached to a specially built transverse piece and by means of the two endless chains d is carried up the incline e and along the upper track /. After the lower end of the tube has passed through the cleaning arrangement it falls on the clean- ing grate g, and automatically cleans itself by striking against the bars of the grate, so that all the excess spelter on the inside of the tube falls down and- collects in the space h underneath the grate. "After the tube has reached the end of the grate it comes on to the inclined bench I. The position of this bench when at rest is horizontal, slightly higher than the Avater bosh m. (See end view.) The falling of the bench to the inclined position is brought about by the wire cable n. This is fastened to the traveling piece o, which is carried along the upper track by the tongs (holding the tube) to the automatic release p. The moment the tongs are opened the bench I carrying the tube takes its original horizontal position. By means of levers, the bench is inclined and the tube rolls of itself into the water bosh m. It is raised from here by the revolving shaft q with its star-like arms r, and rolls down the skids into a car, properly galvanized and cooled. The tongs and cross piece fall down the incline s on a traveling belt t, and are carried back to the starting place, where a new tube is taken, gripped and started on its way by hand. 82 GALVANIZING AND TINNING Pm OALVANTZIXG WIRE, NETTING AND TUBES 83 "As oompared with hand galvanizing, the apparatus has shown a saving in wages of 33^ per cent, and in spelter of 0.8 per cent, of the total weight of tubes to be treated. Under German conditions this amounts to $1.48 per metric ton of finished tubes. A special crane for holding and agitating the tubes during pickling is also briefly described, which lias proved very successful." CHAPTER X By-Products of the Hot Galvanizing Process THREE by-produets are produced in the process of hot gal- vanizing. They are known by the trade terms of "Hard Zinc Dross," "Sal Ammoniac Skimmings" and "Zinc Ashes," sometimes called "Dry Zinc Skimmings," and a brief de- scription of each is given in order. These materials are bought by all the principal scrap metal deal- ers, who, as a rule, can be depended upon for fair business deal- ings. There are exceptions, however, and for this reason sellers should never dispose of galvanizing by-j^roducts by sample nor allow the word sample, or reference to any particular grade of quality, to be used in the terms of sale. The buyer may be per- mitted to take samples of the materials from the bulk as he chooses, but only at his own risk. Each lot should be sold on its merits as it stands without any representations as to quality and absolutely without recourse, except in the matter of weights, which, of course, should be as unquestionably accurate as possible. We have learned through exj^erience that failure to take these pre- cautions may lead to a great deal of trouble and expense. Prices vary with the price of Prime AVestern Spelter, and the quotations made are usually based on the price of this metal, and the terms of payment in the sale of these materials are nearly always cash. Workmen cannot be too careful in the removal of by-products from the galvanizing bath, as every pound of good zinc removed unnecessarily represents a direct loss, and it is a fact that gal- vanizing employees as a rule are inclined to be careless with and slow to appreciate the value of materials which they use. By- products are valuable, and should be treated and stored accord- ingly. It is economy to place a thoroughly competent and con- scientious man in charge of a galvanizing plant even at what might seem a high price. The man who is satisfied with the small- est salary is not necessarily the cheapest man, and the fact should not be lost sight of that a few dollars saved on the pay-roll may 84 BY-PRODUCTS OF THE HOT GALVANIZING PROCESS 8i> easily he more than offset hy losses due to iiieoiiipeteney and waste- ful carelessness of a foreman or those workinti,- under liim. The question often arises as to wlietlier it is advisable for the individual galvanizer to attempt the recovery of his own by- products. The reclaiming and utilization of these so-called waste products has received the attention of scientific men in recent years, and as previously stated, have, through scientific investiga- tions and experiments, heen made to yield high values. Commercially practical methods for the economical treatment and use of drosses and skimmings on a large scale have heen de- veloped with the result that galvanizers can now secure high prices for materials which were formerly consigned to the dump as waste products, and it is douhtful if they can realize as great returns by the treatment of their own by-products as by selling them at prevailing prices to the large buyers who make a specialty of handling these materials. Zinc Dross Zinc in a molten state wall alloy with iron so that iron sub- merged in it will begin to dissolve as soon as it becomes as hot as the zinc bath. The addition of only a small percentage (as little as 3 or 4%) of iron to the bath will form an alloy of zinc and iron called zinc dross, that is of greater specific gravity than zinc itself. This dross in galvanizing is formed principally by the con- tinued washing away of the articles which are being galvanized, although a consideral)le amount is formed by the action of the zinc on the inside of the kettle, as evidenced by the gradual eat- ing away of galvanizing kettles from the inside nntil they are eaten completely through, necessitating the installation of a new kettle, and if by accident or design the kettle is run at a high heat, dross will form very fast. As the dross forms it settles to the bottom of the kettle and becomes hard. When the accumula- tion has reached a point where it interferes with the work it must be removed. This is easily done with the use of a proper tool made for that purpose and called a dross scoop. The handle of the scoop should be about twice the length of the kettle unless the kettle is of a size requiring the use of tackle in drossing it. The scoop should be well perforated with holes not less than V' in diameter to allow the clear metal to flow back into the kettle, and 86 GALVANIZING AND TINNING care should be taken to keep these perforations always open and unobstructed. Before commencing to dross the kettle, i.e., to remove the dross, skim all the flux from the surface of the metal with a perforated skimmer, and if it is in good condition save it for future use. If this flux is broken up when cold and placed carefully back on the surface of the zinc it will soon melt to its former consistency. A perforated skimmer for removing sal ammoniac flux and zinc ashes is shown in Fig. 25 and is designated F. When drossing do not stir or roll the bath unnecessarily in forc- ing the scoop into the hardened mass. Force the scoop gently into the dross and when satisfied that it is full raise it out of the metal by resting the handle on the end of the kettle to get a leverage. Let the scoop remain supported on a bar over the kettle until all the liquid metal has drained back. Dross hardens very rapidly when exposed to the air, and no more time than necessary to allow as much good metal as possible to drip back into the kettle should be consumed before getting the dross into the dross pans. If the handle of the scoop is jarred l)y blows from a hammer or bar of iron more of the clear metal will separate from the dross than if this was not done, and the mass of dross will also drain much more freely if cut down through several times with a flat iron shovel. As soon as clear metal ceases to drip, dump the dross while still in a semi-fluid state into cast iron pans or molds made for the purpose and about 2" deep, 15" long and 9" wide inside. The dross, while still hot, should be worked or molded into the pans and smoothed off on top with a shovel. When the dross hardens in the molds dump them and you have the commercial Hard Zinc Dross. If there should be a large amount of dross in the kettle at a time when it is desired to allow the fires to go completely out it should be removed. If allowed to cool with a large amount of dross lying in the bottom the result will most likely be a burst kettle. The loss caused by the formation of dross is quite large even with an experieiiced man in charge of a kettle, but the amount of dross made is greatly increased by failure in keeping the metal at a temperature which will not injure it; also by allowing work to be lost in the kettle or by immersing work in the bath that has not been properly prepared. BY-PRODUCTS OF THE HOT GALVANIZING PROCESS 87 Running Over or "Sweating" Zinc Dross We are often asked whether it will pay the small galvanizer to try to recover the good zinc from his dross, and if so, how best to accomplish the desired results. It formerly was the practice of most concerns doing galvanizing to rmi over, or, as it is termed, "sweat" their dross, but conditions which formerly made this profit- able have changed materially in the last few years. At the time of the first issue of "Galvanizing and Tinning" the very best zinc dross could be bought at from 25 to 35% of the price of spelter. To-day the most inferior grades readily bring from 50 to 60%, and some of the better grades as high as 80% of the price of the best quality of zinc. Fig. 37 — Dross Sweating Fuknace Without entering into any further discussion regarding the ad- visability of attempting the recovery of zinc dross, we reproduce the illustrations of apparatus for "sweating" dross that appeared in the first issue of "Galvanizing and Tinning." In Fig. 37 we give a perspective view of the kettle and brick work. Fig. 38 is a top view. Fig. 39 is a vertical section of Fig. 38 at A A, and Fig. 40 is a horizontal section of Fig. 39 at the grate line B B. The kettle and casting details for bricking in are shown in Fig. 41. This arrangement is so simple that we do not think it necessary to describe it in detail. 8^ GALVANIZING AND TINNINC A kettle 30" in diameter and 20" deep will answer the purpose very well, and should be made of cast iron, with bottom about 1^" thick. -A Fig. 38 — Plan of Furnace Fig. 39 — Vertical Section of Furnace at A-A Fig. 38 ■Sect/on B-B Fig. 40 — Plan of Furnace at Grate Line To separate the good metal from the dross, first melt up about 6 or 8 inches of lead in the bottom of the kettle and then put in the dross. Bring the dross to a temperature that will cause it to have rather a dark blue color, or to a point where the pyrometer will register about 1050 degrees. When this is accomplished stir the mass with a long-handled ladle for about one-half hour, and then allow it to settle. When the mass has settled the lead will BY-PRODUCTS OF THE HOT GALVANIZING PROCESS m be at tlio liottom, tiip dross will lie on thi' load and iho clear metal will 1)0 at tlio top, where it can be l)ailed out into pans. The stir- ring may l)c repeated once or twice after each bailing operation. After all the clear metal availal)le has been extracted, remove the dross and \n\t it into pans or molds as when first taken from the galvanizino- kettle. Fig. 41 — Castings for Dross Sweating Furnace Sal Ammoniac Skimmings This is the trade term for the sal ammoniac flux used, on the top of the galvanizing kettle when its usefulness as such has l^assed. The thick dirty portion of the flux must be removed from time to time as necessary and should be placed in sheet iron pans of convenient size to cool, when it will be the commercial Sal Ammoniac Skimmings, and should be stored in a dry place. In a plant ojoerated for small castings, forgings and similar work this skimming is usually done twice daily, once the first thing in the morning and once before starting m the afternoon. Too much care cannot be used, in skimming the spent flux from the galvanizing bath, as a considerable amount of zinc can be carried o£E in the flux by carelessness without its being noticed or suspected, and may be the means of quite a loss. A perforated skimmer, shown in Fig. 25 and designated P. should always be used, and it should be kept clean. The perforations should be sufficiently large to permit free exit of metal, about ^" diameter, and the handle of the skimmer should be tapped on the edge of the 90 GALVANIZING AND TINNING kettle while filled with hot flux to shake out as much of the fre6 metal as jDossible. Sal Ammoniac Skimmings should never be mixed with Zinc Ashes, as the value of both will be considerably reduced by so doing. Each should be skimmed from the bath into a separate receptacle, stored separately and plainly marked when packed for shipment. While several methods of treatment for reclaiming the wastes of Sal Ammoniac Skimmings have been developed, we do not con- sider it economical for tlie individual galvanizer to attempt their recovery on a necessarily small scale for reasons previously stated. In a 23lant having several kettles in operation considerable zinc can be recovered from Sal Ammoniac Skimmings with little ex- pense by remelting them in a large mass. This can best be done after dressing when the surface of the zinc is low down in the kettle. Put several days' accumulation of skimmings, which have been kept in a dry j)lace, ijito the kettle at once, which, when melted, should be several inches deep on the top of the metal. Stir this mass well with a poker or skinmier and then skim it off into flux pans, taking first the lighter top portions, and being care- ful to dip the skimmer through into the molten zinc no more than necessary. Large lots of Sal Amnionic Skimmings are often shipped loose in bulk, while small consignments are usually forwarded in casks or barrels. Zinc Ashes The name Zinc Ashes is the trade term for what is really zinc oxide, and which in the galvanizing process accumulates on the bare surface of the molten zinc. Zinc Ashes are formed by con- tinually skimming the surface of the liath clean for the withdrawal of work and by the melting up of new spelter after drossing. It also collects when the bath is lying idle if it is in a molten state, as on Sundays and holidays. Before removing Zinc Ashes from the kettle a little white sal ammoniac should be sprinkled over and well stirred into them with a poker or skimmer. This will be found of great assistance in re- ducing the particles of metallic zinc to a molten state. Plenty of time and care should be used in skimming, as small drops of zinc remaining suspended in the hot ashes are very hard to shake out, and carelessness will greatly increase the losses. BY-PRODUCTS OF THE HOT GALVANIZING PROCESS 01 It is good practice to screen Zinc Ashes through a No. 6 or No. 8 mesh riddle, either by hand or machine, before packing them for the market, throwing out all foreign material. A surprising amount of zinc can be recovered in this way, which can be easily remelted in the galvanizing bath. Any attempt at reclaiming the fine ashes does not pay, as the reduction of zinc oxide is not at present commercially practical for the small operator. These ashes or oxides are largely used by paint manufacturers, however, and they find a ready sale in the scrap metal market. Zinc ashes are usually packed for shipment in bags or barrels, and should always be stored in a dry place. CHAPTER XI Replacing Old Galvanizing Kettles GALVANIZING kettles are good for service until they begin to leak badly or have become so warped or distorted that they cannot be operated satisfactorily. The life of a kettle ranges from a few days or weeks to several yearS;, depending on the class of work handled, and whether it has had careful and intelli- gent operation. Comparatively new kettles sometimes develop a leak through some defect in the steel sheet from which they are made. If such kettles are in good condition otherwise it may pay to bail the molten zinc out to a j^oint below the leak and repair it, either by rivetting on a patch or by welding with electricity, oxy acetylene gas or other method that seems most advisable or economical. If an old kettle which seems to be generally thin and worn starts to leak it is usually economy to tear it out and replace at once Avith a new one. If a successful attempt is made to stop a leak in an old kettle of this kind it will more than likely start to leak in other places within a very short time and your trouljle and ex- pense will be of little avail. When a kettle, whether old or new, starts to leak no time should be lost in bailing the molten metal out to a point below the leak, always removing as much dross as possible before taking out the clear metal. At this point it can l)e decided whether or not to try and repair the kettle and if not, continue the l^ailing operation until the kettle is empty, always removing the dross first. When bailing out an old kettle do not let the fires cool off too much, thereby allowing the zinc or dross to congeal on the sides, as you may have consideral)le difficulty in removing it. When an old kettle, especially a large one, suddenly starts to leak badly it is often advisal:)le to secure considerable extra help in order to remove the dross and metal quickly, thus preventing the molten zinc from running into ash pits or elsewhere and cool- ing in such a Avay that it cannot be easily recovered or handled for re-melting. A little extra expense in the matter of labor employed at such a time can easily result in a substantial saving later on. 92 REPLACING OLD GALVANIZING KETTLES 93 An ordinary iron muldcr's ladle with an iroii handle makes an excellent tool for hailing out a galvanizing kettle, and several should he kept on hand ready for use if they are liahle to he re- quired in sueli an emergency. After an old kettle has been hailed out as clean as possihle draw the fires and wet it down with water to hasten the cooling ofE process if necessary, after which remove carefully all holts, nuts, castings and other iron work for use again. The brick work can then be torn down to the foundation and the old kettle removed, after which the new kettle may be set up on the same foundation, filled with zinc and heated up the same as any new kettle, instruc- tions for which are given on pages 20 to 26 and 66 and 67. CHAPTER XII The Schoop Metal Spray Process ONE of the great metallurgical problems of the day has been to produce a non-corrosive surface on iron and steel, the indispensable but vulnerable materials of engineering con- struction, without affecting the physical properties of these metals or the shape or usefulness of the object treated. There are demands in the arts for a method which will take the process to the work or to any part of it, and will secure the quick deposition on any coherent object, whether metallic or not, of any desired metal or alloy in any quantity, however minute. This is the ideal metal coating process. Inventors have labored over the problem for many years but commercial results have not been developed until recently because of the lack of economy in the earlier forms of apparatus. The overlaying of iron and steel for temporary effect with non- metallic substances, such as paints, enamel, japan, and varnish, has been the mechanical method necessarily followed hitherto for the great bulk of metal objects and structures and the renewal and maintenance of such protections involves enormous outlays. It is the object of this chapter to describe the latest mechanical process for depositing electro-positive metals, such as tin and zinc, on iron and steel. Incidentally, the method permits of depositing many other metals and alloys on coherent bodies whether metallic or not. The Process takes its name from M. U. Schoop, an engineer of Zurich, who, in collaboration with other inventors, made the metal spray an effective coating agent. In the Schoop Process, the United States patents for which have just been issued, the coating metal adheres to the object chiefly by mechanical union. The metal is discharged in hot impalpable particles moving with high velocity, and these when directed upon a prepared object penetrate the pores of the latter while the spray is still plastic. The coating metal thus dovetails itself into the superficial pores of the object and does so in the presence of reducing gas, which prevents oxi- dation at the junction of the metals. The progress of invention on metal spraying has been chiefly 94 THE SCHOOP METAL SPRAY PROCESS 95 directed toward making the metallic particles as small and as hot as possihle and to avoiding oxidation. In 1902 Thurston, United States No. 706,701, was granted a patent for impacting, with unignited gas, metal in the form of dust upon a metallic base. His apparatus was not practical and no commercial results were obtained. Within the past year four United States patents have been issued which embrace all the important steps since Thurston's invention. Schoop, United States No. 1,128,058, invented a process for pro- ducing a fine spray from either molten or solid metal and also for producing separable metallic coatings or copies of the objects sprayed upon ; this was known as the liquid metal spraying process. Schoop, United States No. 1,128,059, later invented a process for projecting finely divided unmolten metal particles on to a surface, using an ignited gas and metal in the form of dust like Thurston. This was known as the metal dust spraying process. Very soon afterward Morf, United States No. 1,128,175, in- vented a process for melting, atomizing and projecting, practically simultaneously, solid metal and particularly metal in the form of wire. This was known as the metal wire spraying process. At the same time Morf, United States No. 1,100,602, invented a successful apparatus (known as a "Pistol"), for effecting this process. These inventions above outlined form the basis of the Schoop Metal Spray Process_ as it is now operated in the United States. The present chapter is wholly concerned with the apparatus used for tinning and galvanizing by this method and with the applica- tions possible. The evolution of the apparatus has been interesting. The liquid metal process involved a large non-portable reservoir of hot metal weighing with the auxiliary parts over a ton; the metal dust ap- paratus weighed over a hundred pounds, while the "Pistol" of to-day weighs less than four pounds. Figures A, B, and C show the three forms through which the apparatus has passed. In the apparatus represented by Fig. A, a melted metal is allowed to run continuously from the reservoir "R" through a broad noz- zle "N," where it is broken up and swept away by a violent cur- rent of heated gas "G," issuing under regulated pressure from containers "C" and reheated in its passage at "H." The expansion 96 GALVANIZING AND TINNING of the gas chills the molten particles and forms a rapidly moving spray or fog of metal which impacts n|)on any ol)ject placed in its path and plates it. Any metal fusible imder the conditions of the apparatus can be used and owing to the low temperature of the fog, it is possible to plate very delicate or easily comljustible objects, as well as metal articles. Fig. a — First Type of IMetal Spray Apparatus Aluminum plating, which could not be obtained by fusion or electrolysis on account of its ready oxidation, was easily obtained by the Schooj) Process. The obvious objections to such an apparatus were lack of por- tability and the expense of melting and keeping fluid most of the metals in the unavoidable intervals of spraying. The result was that only the more fusible metals, zinc and tin, were used where spraying on a continuous scale was possible and the liquid metal apparatus was never reduced to economical practice. It was ob- served with this apparatus, however, that the particles were not actually molten at the moment of impact and this suggested the next step. Fig, B represents the second form of apparatus in which -porta- bility was secured and the metal particles to be sprayed were pre- pared in advance. Powdered metals in a very fine state of division have many of the characteristics of a liquid. Their fine particles mix with one another like drops, they spread with facility and unite under the influence of very little force. The metal powder in the container "C" is entrained in an air THE SCHOOP METAL SPRAY PROCESS 97 Fig. B — Second Type, Portable Metal Spray Apparatus 98 GALVANIZING AND TINNING blast "A," heated in the flame of a blast pipe "B" and projected with high velocity. The gas is burned at "A" and the supply of air is regulated at "S" to obtain complete combustion. Fig. C — Third Type or Metal Spray Pistol It was found that the anticipations from the use of the first apparatus were correct and that metal particles projected in a Fig. D — Detail of Metal Spray Pistol Nozzle pasty condition produced plating as before. Metal powders, how- ever, are very costly. Most of them tend to oxidize rapidly and the use of this apparatus was practically restricted to zinc on that THE SCHOOP METAL SPRAY PROCESS 99 account. The zinc is a by-product of Zinc Smelteries and is readily applied by the simple apparatus known as the "Cyclone/' which has just been described. It is still the most economical method of producing a Schoop coating of zinc. Inventors set themselves to overcome both the chemical and Mixed Gas .Passage of Burner ! Inner Nozzle fhctf guides wire Wire Guide Connecfion for Plixed Gases ' Fig. E — Section Showing Detail of Constkuction of Pistol economic difficulties with other metals including tin, viz, : to dis- pense with mass melting and dust preparation and to secure in- stant and simultaneous melting, and pulverization, and control with a handy, economical appliance. The result was the ingenious instrument known as the "Pistol," which is shown in Fig. C. The principle (Fig. D) consists in feeding a fine wire "W" of any metal into a reducing flame zone "Z" at such a constant speed that the end of the wire "E" remains stationary, its melting rate being exactly equal to the rate of feed. Under such conditions the wire end melts a drop at a time and each drop at the instant of formation is struck a violent blow by an air blast "A." The resulting fog or spray of fine particles into which the drops 100 GALVANIZING AND TINNING are divided takes the form of a diverging cone "C" with a core of reducing gas "G" in which the particles are entrained, and a surrounding sheath of air ''A," which is rapidly expanding and cooling. Any suitably prepared object placed in the path of this metallic spray is plated through impact without undue elevation of temperature. Pig. E is a section of the commercial spraying pistol now in use. The principal parts of the pistol consist of an outer casing "A," cast of aluminum, with a central downward projecting tube form- ing a handle, a wire feed mechanism mounted entirely upon the cover "B," of the turbine chamber, the turbine "C," actuating the wire feed mechanism, gas, air and wire nozzles mounted upon the outer casing held in position by a hand nut "D," and a removable cover "P," which completes the enclosure of the outer casing. Gas and air ducts are drilled in the outer casing, the flow con- trolled by the tapered valve "¥" provided with a handle "G." The wire feed mechanism is actuated by a turbine "C" mounted on a vertical shaft running in ball bearings; a worm is cut in the upper end of the vertical shaft and drives by worm wheels the horizontal shafts "W and "0", which are provided with worms in turn driving the worm wheels "P" and "Q." The worms "P" and "Q" are provided with slots to engage the projecting lugs of the lower feed wheel "E." The upper feed wheel "S" mounted in the pivoted frame "T" is provided with shrouds controlling the position of the lower feed wheel "E." The lower feed wheel can be engaged in either work "P" or "Q" by raising a clip "I" shifting laterally in either direction and locked in by the opposite clip. The shift can be readily made by allowing the mechanism to run slowly by a slight opening of the starting valve. Pressure is applied to the feed wheels through the pivoted frame "T" by a coiled spring, and controlled by the operator by means of the release lever "K." The final adjustment of the wire feed is controlled by the needle valve "M." The turbine and shaft complete is assembled in the outer case and properly adjusted independently of other mecha- nism. The wire feed is entirely assembled on the turbine cover "D'* and when properly adjusted, secured in position. The wire nozzle THE SCHOOP METAL SPRAY PROCESS 101 base ''U" provides an adjustment for position of wire and gas no;^- zles, and is seeured in position by a headless set screw. The upper end of the stem of the turbine cover is provided with an annular groove, which is engsiged by the spring loop "Y" and secures the removable cover "E" of the case. Loop "V" provides a means for hanging the pistol on a conveniently located hook. The Operation of the Pistol The. gas and l)last nozzle faces, "B" and "C," are securely clamped to form gas tight joints by tightening the hand nut "D." The end of the central or wire nozzle is then .015" inside the gas nozzle and the stationary melting point of the wire is .03" inside the air blast nozzle. The wire diameter used is from .0319" to .0375", except zinc and tin, which are used in larger sizes, owing to their rapidity of melting. The feed gears having been set in mesh at the approximate speed required for the wire selected, the air alone is turned on and the speed tested with a short length of wire. Adjustment, if neces- sary, is made by the needle valve, which modifies the speed two feet per minute plus or minus. The end of the wire reel is then threaded through the stock receiving tube, . between the gripping feed rolls and into the cen- tral wire nozzle and the fuel gas pressures from the containers are adjusted l3y the reducing valves and gauges thereon to the tabular requirements for the metal to l)e sprayed. The pressures of the fuel gases seldom -rise above one atmosphere and hydrogen or Blau gas are the reducing gases usually emploj'ed. This gas is now admitted by slightly opening the starting valve and when ignited with a match burns quietly as a pilot light. The starting valve is then opened up full and oxygen is admitted gradually till the flame zone is established. All 1mck-firing is avoided by keeping the reducing gas always in excess of the oxy- gen, the ratio l)eing three or four to one. The above movcment:- are made in rapid succession on a light instrument which can be held in one, hand and the spray is started up the moment the con- stant melting position of the wire is reached. The spray so established is essentially a metal plating air- brush of which the diameter 5" from the pistol end is ab.out 2". Objects to be plated are operated upon by pointing the pistol nor- mally to the surface to be coated at any moment at about five (5) 102 GALVANIZING AND TINNING inches distance and traversing the pistol across tlie surface with a regular motion. A single coating is al30ut .001" thick. The operator's vision easily guides him in distinguishing between the coated and un- coated portions and also between a first and second coat. Two thousandths of an inch well impacted upon a surface are just as effective as a much greater thickness and of course unneces- sary sprayed metal increases the cost, as the latter is directly pro- portional to the thickness. Not only on the score of economy but also to preserve tough- ness the coating should l^e of minimum tliickness, for the anvil action of the metallic spray on a solid metal object is lost above a few thousandths of an inch thickness and a process of cold working follows which produces a brittle scale readily de- tacliable. In i^ractice this matter is easily regulated. Fig. C shows the pistol held in the hand ready for action Avith the wire thread in position. Fig. P shoAvs the pistol applied to coat a wooden pattern for protection with tin. Gas bombs with fittings and air at 40 pounds 23ressure are tlie only requisites besides the "Pistol" and its hose connections for plating non-metallic objects such as wood, stone, paper, cement, cloth, etc. All metallic surfaces should have tlie scale cleaned off and their ^^ores opened by preliminary sand-blasting. It will be seen from the taljles appended that .001" thickness, one square foot in area, of the common metals can l)e sprayed for a small sum. The total cost is five cents per square foot for tin and tAvo cents per square foot for zinc. Various theories have been offered to account for the plating properties of the Metal Spray, but it is believed by those putting it to practical use that, except in the fcAV cases where the impacted metals have a chemical afPmity, the action of the spray is jourely mechanical and restricted to superficial pores of the object. Metal Spraying is essentially a kinetic energy process and the "Pistol" is practically a rapid fire gun which manufactures its own ammunition automatically from a reel of wire and discharges an infinite number of projectiles which im|)act themselves in the ex- posed pores of any object five inches aAvay. In the zinc dust "Cyclone" apparatus the size of the projected particle is predeter- mined, but the action at the object is identical Avith that of the THE SCHOOP METAL SPRAY PROCESS 103 'Tistol." In either case with proper preparation of clean, open surfaces a durahle, adherent, protective coating is attained. In general, the applications of the Metal Spray Process may he divided into five groups, namely, protective coatings; honding or Fig. F — Method of Using Pistol in Spraying junction coatings; electrical coatings; decorative coatings; and de- tachable coatings or copies of the objects. Protective coatings on steel or iron may be either original coat- ings of the whole of an object or structure, or they may be confined to any part of it, or they may be merely local applications with the 104 GALVANIZING AND TINNING "Pistor" or '^'Cyclone"' apparatus to repair damage or wear to a coating of tin or zinc made by another process. The repair of the troublesome defects found on many galvanized and tinned sheets, and leading to their rejection, is an application of this process which is made only through the possibility of applying tin or zinc to any area, however small, and confining it to that area. An- other application for the same cause is the filling up of pin holes in expensive machine castings, such as printing rolls, etc., which would otherwise be a complete loss. Many engineering structures used in the arts, such as steel and iron tanks, bridges, girders, and machinery of all descriptions, cor- rode rapidly, jDarticularly at joints, especially if exposed to atmos- phere or liquids. It is not possible to plate such structures by any other coating method than the Schoop Process. In such cases tin or zinc may be applied from dust or wire form on all seams and joints or all over the structure, surfaces having been previously cleaned by a light sand-blasting. This treatment can be made on the parts of individual memljers at the shops or in the field by jDortable cyclone and compressor outfits wherever the nozzle of the apparatus can be pointed normally to any surface. Proper initial treatment of this kind or in the field during erection dispenses with all need for repeated painting. Laundry machinery, milking machinery, dairy utensils, water heaters, and similar appliances subject to corrosion can be pro- tected against decay due to electrolysis by sprayed deposits of zinc suitably located. The Schoop coatings do not compete in cost with, the ordinary tinning or galvanizing applied to tonnage goods and purely temporary in its efi^ects. From the table appended, how- ever, showing the data of gas consumption and total cost of spray- ing a square foot .001" thick of all the commoner metals, it will be seen that tin and zinc can be applied effectively for 21/4 cents per square foot ; where zinc dust is applied by the "cyclone" appa- ratus it can be done for II/2 cents per square foot. THE SCHOOP METAL SPRAY PROCESS 105 o o S c ' o j; o <-< iXi CO — ' I^ 00 -— 1 CO -f (M "O t^ Ol O O CO (M OI Ol Ol ^-< CO CC O OOOOOOO-H CO lO (N lO '^^ CO •^ CO (M (M O -— I CO ^ -^ CO to O t^ O-l O ^ ,-H ^ ^ ,_; ■ c^i CO ^ CO lO (M lO O cococo-+i-*cooio CO CO -^_ to -*_ (N o ^ m ' ' ' " '-^ CO --H -* oococ5oO(Moocoo OOOOCOOCiO T-H ,—(,_( ^H fH oooooooo CM(M(N(M(NC<1(M(M €© OOOOOOOO cocococococococo o O CO CO C/D ^ O O O O^ of^ 5 2 -^ t; 0; •- «S »o cO'^TjH'^cooooo lO CO »0 CO (N (N Cq (M O CO . 00 t^ 00 o (M (M CM i c^i -TlH O to CO i— I CM CM CM CM O GO >0 to r— ll— Ir-Hl— It— IT— (CMCM to CM Ol C^l CM t^ CO CO CO CO CO O O o o o to t^ CO ^ CO t^ CO o o o a; m s a ^M C ^ ^ o Oh -i O ^ 13 e « to 'O to CM Ol Ol to t^ Ol t^ CO to O -fi to CO I^ COCOt^t^-t^tO-— it^ O 05 '-'"S-S ?=. to »0 to CM CM CM t^OC-liOt^COOO '-I'— iCMCMCOCO^-Ht^ to t^ CM O I> CO T— I l^ C^l CO t^ lOTtitotOOCMOO COOOGOOOGOrtlC-l'^ CM CM CM CM '* ^ CMCMCMCMOOOtOtO T— It— li— It— It— Ir-lCMCM OO-fOT-ICOOtO n'tO'^^COCOCOtOO CO CO CO CO r^ CM T— I COt— It— ItOOCO-^^CO aDt^-^-tfi^ot^co CMCMCOCOt— It— iCMO oooooooo CO ^ T— I to CM to to t^r^oo-tT— i^nr^ OOT-ir-tO— iCMCO oooooooo (X) ^ -* 00 T— iO-*-+iCMCOCOOO CM CM Ol C^l ^ O O O oooooooo O to — i^T-icO^^O-lCM oooooooo OOOOOOOO o c o ^ o M OOOOOOiOO T— It— It— It— l-^COCMCO ^ ' — ^ '"' ' — ^ ' — ^ 1 1 1 1 Speed of Wiie per Minute CMCMCMCMcOOOtOtO T— It — ^T — It — It— It — ICMCM .2"S f=5 CM CM CM CM CO CM CO CO CO CO t^ CO o o o o o o cc a o ^ a3^ i^ -a OC:QhClO<:csUH CHAPTER XIII Tinning Malleable Iron Castings, Wrought Iron and Steel TO SIMPLY give articles of malleable and wrought iron a coating of tin is a comparatively easy process to master, but the tinning of certain classes of hardware has reached a high state of perfection, and to tin saddlery hardware and table cutlery requires considerable skill. The methods employed to do the work vary greatly in different establishments, and the degree of perfection attained is equally varied. Work that is tinned in an indifferent and slovenly manner is not necessarily done cheaply, as the metal wasted on an article that is roughly and imperfectly coated may be of more value than the slight saving in labor cost obtained by rushing the work through without giving proper at- tention to the applying of a light and even coating. The high price of pig tin makes the material cost of tinning much more than the labor cost. The use of care in bringing the finished ar- ticles out free from surplus tin not only adds greatly to the com- mercial appearance ol: the goods, but materially decreases the cost of the work. Tha most economical result is obtained by careful attention to tbe h?at of the tinning bath and to the skillful hand- ling of the articles duriiig their removal from it and before they are cooled. If the tin is not hot enough the articles will be heavily coated, and it will cool on the work bunchy and wavy. Tin when heated above a certain limit also causes a rough and uneven appear- ance of the Avork, injures its color and destroys the luster. The use of a good pyrometer in a tinning bath is a great help to the operator in maintaining a proper and uniform heat of the tin. Care in keeping the tin free from dross or slag is an important point in obtaining perfect work and will be referred to in its proper place. Plant and Equipment When installing a tinning plant convenient arrangement for handling the work should be given all the consideration possible, and the operator will find it a great help toward making his work 106 TINNING MALLEABLE IRON CASTINGS, WROUGHT IRON 107 easy, as well as efficient, if he will study to improve methods and tools employed in handling the various articles that come to him for tinning. While it is our purpose to treat the subject of tinning in a man- ner that will enable a novice to make a successful beginning, the best results (;an, of course, only be reached by actual experience. With the principles and requisites necessary to perfect results well understood no trouble should be experienced by one of average mechanical ability in mastering the business. To make the different ojjerations of preparing and tinning ar- ticles of malleable iron, wrought iron and steel easily understood, we shall treat each operation separately. While the illustrations we give will serve as a general guide in equipping a plant, it docs not follow that they cannot be changed to suit local conditions. It would be impossible to illustrate here the exact plan best to follow iji each individual case, and those undertaking the installation of a plant must be governed to a great extent by their requirements as they see them. It should be kept in mind when deciding what part of the factory can best be devoted to the tinning department that more or less gases and fumes prevail while the work is carried on. These gases and fumes are not only disagreeable to inhale, but are de- structive to fine machinery, tools and finished work. That the work may not become a source of annoj'ance to those who are not immediately engaged in it or destructive to machinery and stock, the tinning plant should be located if possible in a building by itself, taking care to provide good ventilation and drainage. A room devoted to this work should not be less than 10 feet in height, and it is a good plan to provide the kettles and acid tanks with hoods connected with ventilators to carry off the fumes. The hoods should, of course, be high enough to prevent interference with the work of the operators. The illustrations show tanks of cypress or pine for containing the different solutions used in preparing and finishing the work, but oil barrels sawed in half may be employed for the purpose if they are properly cleaned inside, either by burning or washing in a hot, strong solution of soda ash and water. For heating the tin hard coal is best, as it gives the most uniform heat and is most easily controlled. Soft coal, coke, natural gas and even wood can, however, be employed for the purpose. 108 GALVANIZING AND TINNING Plan of a Tinning Plant We show in Fig. 42 a ground plan of a tinning plant intended for general work, except the tinning of common cast iron. In this illustration A is the roughing kettle — that is, the kettle used to give the work its first coating of tin; B is the finishing kettle; C is the tank containing muriate of zinc; D is what is termed in Fig. 42 — Arrangement of Equipment in a Tinning Plant the trade the "wjiipping box/' and is simply an arrangement to prevent the drops of molten tin being thrown promiscuously around the room when the operator is shaking or swinging his work to free it from surplus metal; E is a tank made of sheet iron for containing the kerosene oil used to cool the work in, the intent being to have this tank surrounded by cold running water to keep the oil cool, the water l)eing contained in the companion tank F ; G is a tank provided with a steam coil, the intent being to keep the tank filled with clean, hot water, in which to rinse the finished work before drying it off in the sawdust, which is con- tained in the box H; I and are water tanks used for storing the work after it has been cleaned in the acid; K is a tank con- taining muriatic or sulphuric acid; L and ]\I are acid tanks, the use of which will be explained in the proper place; N is a tank for containing a hot alkali solution, and it should be provided with TINNINC MALLEABLE IRON CASTINGS, WROUGHT IRON 109 a steam coil; E denotes a drain through the center of the room for carrying off the waste water. A sectional plan of this floor is given in Fig. 43. H / / y / W^ Fig. 43 — Details of Floor Construction, Showing Drain Tools and Kettles The tools employed in handling the work are very simple in con- struction. They consist of wires formed into various shapes, ladles or baskets made from perfoi'ated sheet iron or wire cloth, and tongs with jaws formed to hold the various articles to be handled with them. Those illustrated l\y Fig. 25 in chapter on galvanizing will be found useful and all that will be required in many cases. The ingenuity of the operator will readily suggest what tools are re- quired for the work in hand. The number of tinning kettles necessary depends altogether on the class of goods to be tinned. The most common kinds of hard- ware specialties can be tinned very satisfactorily in a single kettle, while the better class of tinning, such as saddlery hardware, iron spoons, etc., require two kettles for best results, and even three may sometimes be employed to good advantage. Where a plant is fitted up for a fine grade of tinning, the kettle used to give the castings their first coating is called a "roughing" kettle, and the other kettle or kettles the "finishing." When a roughing kettle is used no particular care is taken to have the articles come from it smoothly coated or free from surplus tin, as 110 GALVANIZING AND TINNING the unevenness of the coating will be removed by their treatment in finishing. The object of the roughing kettle is to give the iron a thorough coating of tin, as rapidly as it is prepared for receiv- ing it, to prevent rusting. After the iron receives a thorough roughing coat it may be stored away until required for finishing. For those having only a small amount of tinning to do it would not pay to invest in an expensive outfit of wet rolling barrels, and very good results can be olitained without them. In fact, only a few of the larger concerns engaged in tinning are so fitted, and their work is of a nature that requires the best results possible to obtain in the way of smoothness and brightness of finish. CHAPTER XIV Preparing the Work for Tinning ORDINAIiILY the common grades of tinned articles are made ready for tinning by simply removing the sand, scale or rust by pickling in commercial sulphuric, muri- atic or hydrofluoric acid, but the finer grades of work are pre- pared for tinning by careful and lengthy treatment in the water rolling barrel. Removing Scale and Rust with Sulphuric Acid Before steel and wrought iron will take a coating of tin all scale and rust must be removed. This is best accomplished with a pickle composed of 1 part sulphuric acid to about 30 to 40 of water, bringing the solution to a temperature of about 150 de- grees F. If the articles are of such shape that they will pack closely to- gether they must be stirred at intervals while pickling so the acid will have free action on all parts alike, otherwise the scale or rust will not be removed on the parts that come in contact with each other, the result being that the acid will burn the material ex- posed to the action of the pickle before the scale could possibly be removed from the parts in contact. In pickling sheets they must be placed in racks that will prevent one sheet lying against another. Sheets should be carefully in- spected, and any spots that the acid has not touched must be re- moved with the aid of a sharp-pointed steel tool. The shank of an old file ground to a point and hardened answers the purpose very well. If the articles are small, and it is desired to give them a fine surface, roll them in gravel and water after removing the scale and rust with the acid solution, and to further improve their sur- face give them a second rolling in scraps of leather. The effect of rolling is to give the articles a smooth surface, and the smoother the surface obtained iu preparing, the smoother and brighter will be the goods after tinning. We do not wish it to be understood that the rolling operation is 111 112 GALVANIZING AND TINNING absolutely necessary to obtain a complete coating of the goods, as they will take the tin perfectly if that operation is omitted, pro- vided they are properly cleaned, but their appearance is greatly improved by rolling, and when it is desired to obtain the best finish possible the rolling barrel must be employed. When the removal of scale and rust has been accomplished and the material is perfectly clean it should be stored in tanks contain- ing clear water, there to remain until the operator is ready to put it through the subsequent operations. Do not allow the work to remain in running water, as it will soon rust or oxidize. The operator must not fail to examine the work frequently while it remains in the hot pickle to determine when the desired result has been obtained. If it is allowed to remain too long a time after the scale and rust have been removed the acid will attack the surface of the material and leave it rougb and seamed. Imper- fections caused by overpickling cannot be eliminated by the coating of tin, and the commercial appearance of the goods will be injured. Cleaning Sandy Castings with Sulphuric Acid Castings that have sand on tliem must be subjected to a treat- ment that will effectually remove it, as a perfect coating cannot be obtained if sand remains. The removal of sand can be ac- complished by placing the castings on an inclined platform and keeping tbem wet with a cold pickle composed of 1 part sulphuric acid to 6 of water, until the sand is loosened enough to be washed off by a stream of water. From 10 to 20 hours is required to accomplish its removal, and then a casting brush must often be employed to remove all the small particles that are burned in where there are sharp angles. Kollnig- with plenty of sharp scratches or stars is the only sure way to obtain a perfectly smooth, clean casting, and we should never attempt to tin malleable castings in any considerable quan- tity without the aid of a rolling barrel. As in the case of steel or wrought iron articles, the wet rolling barrel supplemented by the dry rolling in leather scraps fits the castings to take a beautiful coating of tin with a bright luster. The platform on which castings are placed for pickling with sulphuric acid should have a tank placed under one end at its lowest point to catch the acid as it flows from the castings after each bailing operation. PREPARING THE WORK FOR TINNING 113 Cleaning with Muriatic Acid The removal of scale and rust from wrought iron and steel can be accomplislied by a pickle composed of 1 part muriatic acid to 15 to 20 parts of water, but the cost is greater and the result obtained no better. It is not advisable to use this acid for the purpose unless the amount of work to be treated is very limited and the sulphuric acid pickle is not available. In Fig. 42 K represents a tank to be used for the sulphuric or muriatic pickle, and I indicates the storage tank for the prepared work. Cleaning Sandy Castings with Hydrofluoric Acid We have given the course to be followed for cleaning sandy castings with sulphuric acid, because it may not always be pos- sible to obtain hydrofluoric acid. Where it is possible to substi- tute this powerful acid for sulphuric it should be employed, as its action is much more rapid and certain, and less destructive to the castings. In employing hydrofluoric acid to remove sand make a solution for slow pickling in the proportion of 1 part acid to 30 of water. For quick pickling make the proportion 1 of acid to 20 of water. Immerse the castings until the sand is dissolved, M^hich will be in from 15 minutes to 3 hours, depending on the strength and tem- perature of the solution and the tenaciousness of the sand. A good arrangement for doing this work is made by two or more small tanks for containing the castings elevated by a bench or stand a few inches above a larger tank containing the pickling solution. The castings are covered by solution bailed from the lower tank, which is easily drawn off after the castings are pickled by removing plugs fitted to holes in the bottoms of the smaller tanks. In this way the pickling solution can be used over and over again, while the castings can be easily removed for subse- quent treatments. Water Rolling This method of preparation not only effectually removes all im- pediments to a perfect coating, but gives the articles a perfectly smooth surface on which to deposit the tin, the degree of per- fection obtained being determined by the time and care expended in the rolling operation. Further information on the rolling and 114 GALVANIZING AND TINNING tumbling of cast, wrought and malleable iron to be tinned is given in Chapter VI, pages 51 to 65. Removing Paint or Grease If the work has grease or paint on it, it must be removed and the sand blast will be found of great value for this work, although a hot solution of caustic soda or soda ash will often times accom- plish the desired result. Make the ' solution very hot and strong, and immerse the work in it until free from all such matter, after which rinse it thoroughly in clean water. This operation should precede pickling when necessary to perform it. The tanks for this purpose are designated in Fig. 42 as N and 0; N being the caustic soda tank and the rinsing tank. CHAPTER XV Applying the Coating of Tin AS ALREADY stated, very good results can be obtained by simply using one kettle of tin when the commercial ap- pearance of the work is of secondary importance. AVhere only a single kettle is employed the tin should be maintained at a temperature of about 500 degrees F., and the work may be cooled in hot water and dried off in sawdust. The operations preliminary to dipping the work in the tinning bath are precisely what they would be if more than one kettle was used. As these operations will be explained in connection with those for using two kettles, we will not give them here. Fig. 44 — Front Elevation Fig. 45 — Side Elevation Details of Tinning Kettle Where only a single kettle is employed more or less trouble will be experienced in keeping the dross or slag which rises to tlie sur- face of the tin from adhering to the work, and in keeping the tin at a uniform temperature. The dross or slag must be removed from the tin frequently with a perforated skimmer, and when the black flux that forms on the surface of the tin from the muriate of zinc, in which the castings are dipped previous to immersing 115 116 GALVANIZING AND TINNING them in the molten tin, becomes present in sufficient quantities to interfere with drawing the worlv, it must also be removed in part. A small amount aids in the work, but when it accumulates in a sufficient quantity to catch on the work as it is drawn out it is apt to stain the work and leave white streaks wherever it touches. The cooling water should also be kept clean and free from acid. If it is not, the work is liable to be discol- ored and rust. In Figs. 44, 45 and 46 we show manner of bricking in a single kettle, the casting details being shown in Fig. 47. Fig. 46 — Plan at Grate Line i I L I B=i. "^ a. Fig. 47 — Castings Required for Tinning Kettle Tinning with Two or More Kettles of Tin When the work has been made perfectly clean and free from sand, scale, rust, grease or paint by some one of the treatments described, it is ready for the final operations. If the work is of a kind that will admit of its being strung on wires, use such wires as seem best adapted to the work in hand. For many kinds of work a piece of wire bent in the shape of a croquet wicket, but larger, will be just the thing. Good stiff wires should be used, and they should be long enough to allow plenty of room for the operator Applying the coating of tin ii? to grasp the ends withoiit being burned. That is to say, if you have 10 inches of tin in the kettle, make the end of the wire 20 inches long, which will allow 10 inches of wire out of the tin where the operator can grasp it when he is ready to draw the work from the kettle. Provide plenty of these wires so that the hand- ling of the work may be facilitated. String on wires as much of the work as you think you can handle comfortably, and put them, several strings at a time, into the alkali solution. The work may be allowed to remain in this solution for several minutes, or while the operator is filling more wires. From the alkali solution the work is to be passed into the rinsing tank, where care should be taken that all traces of the alkali are removed. When this is accomplished the work is to be given a few minutes' immersion in a solution of muriatic acid and water. This mix- ture should be in the proportion of 1 of acid to 4 or 5 of water in cold weather, while in warm weather 8 or 10 of water to 1 of acid will do the required work. The object of this dip is to remove any trace of rust that may have formed on the work. The tank for this purpose is designated as K in Fig. 42, and for many kinds of work, such as castings that have been cleaned by dry rolling, and goods made of material that has no scale, all that is necessary is to give it a few minutes' immersion in this solution. After this last dip of muriatic acid and water, which by the way should never be omitted, the work is to be dipped in muriate of zinc, which is the last dip previous to immersing it in the molten tin. Tank C, Fig. 42, is used to contain the muriate of zinc, which solution is made by dissolving scraps of zinc in clear muri- atic acid. Passing the Work Through the Tinning Kettle If two kettles of tin are in use, as shown in Fig. 42 by A and B, take a wire full of work to be dipped and plunge it while wet with muriate of zinc into the tin in the roughing kettle, desig- nated in Fig. 42 as A. Put several strings of work into the kettle at once and allow them to remain until the work is as hot as the tin, which, in this kettle, should be maintained at a heat of about 500 degrees F. After the work has remamed in the roughing kettle for the re- quired time take a wire full in the left hand, and with a skimmer 118 GALVANIZING AND TINNING in the right hand clear a space on the surface of the tin larg6 enough to permit the wire full of work being removed without any of the dross or flux adhering to it. Eemove the wire full of work and pass it directly to the second kettle. It is not necessary to shake of? the surplus tin when removing work from the first ket- tle, but it is necessary to use care that none of the flux or slag is carried over to the second kettle on the work. While retaining hold of the wire the operator allows the work to remain in the second kettle for a fraction of a minute until the heat of the work attained in the first kettle is reduced to about the temperature of tlie tin in the second kettle, which for most purposes should be about 400 degrees F. Very small articles may require that the tin in the second kettle attain a temperature of 450 de- grees P. A little higher heat will cause the tallow, which is on the surface of the second kettle, to a depth of ^ to 1 inch, to ignite. When the Avork has about reached the heat of the metal draw it quickly from the tin, and after a few ra|)id swinging mo- tions to free it of surplus metal plunge it into the tank of kerosene oil, using motions calculated to keep the articles from sticking to- gether. A little practice will soon determine what motion is best for keeping the articles separated and preventing lumps of tin from forming on the work. D in Fig. 42 denotes the position of the box provided to catch the drops of surplus tin that are thrown from the work as the operator swings it to and fro. E denotes the tank for containing kerosene used for cooling, as already explained, and this tank should be surrounded by running water to prevent the oil "heating to a point where it would ignite. The work should be allowed to remain in the oil long enough to set the coating of tin, and should then be dipped in hot water and thrown into fine dry sawdust to dry it and remove the oil. If the articles are very heavy it may be necessary to plunge them into cold water after the oil. If small work cannot be strung on wires a "basket" may be used for dipping it. The basket may be made of sheet iron, in which case it should be well perforated to allow the tin to escape, or it may be made of wire cloth of a mesh sufficiently small to prevent the work falling through. Fig. 25 illustrates the shape of these baskets, which are designated as A and B. Nails, tacks, rivets and' all similar small articles are tinned by means of these baskets. APPLYING THE COATING OF TIN 11& Tongs are used for handling heavy articles, but those used in the tin should not be used for cooling the work, as they would mark it. The tongs used for cooling should not be put into the molten tin. The shape of tongs should be made to suit the form of the article to be handled. Tinning Wire in Coils In large' manufacturing establishments machinery is employed with which several strands of wire are passed through the tinning kettle simultaneously. To do the work on a small scale, provide reels that will accommodate a coil of wire. Place one of the reels in a position where the black wire will pass, as it is uncoiled, through a tank containing muriate of zinc through the kettle of tin. The other reel should be placed in a position where it will coil up the wire as it is drawn out of the tin. The reel used to draw the wire through the kettle must, of course, be provided with an ar- rangement for revolving it, and a device to hold the wire under the muriate of zinc and also under the tin as it passes through must be employed. As the necessary arrangement will readily suggest itself we do not think it necessary to illustrate it. At the point where the wire leaves the molten tin a piece of tow is twisted around the strand, sufficiently tight to wipe off the surplus metal, which flows back into the kettle. If the wire is very heavy it must pass through water after it leaves the tin, the water tank being placed where the wire will not enter it until it has passed through the bunch of tow used for wining off the sur- plus metal. If the wire is covered with a heavy scale or rust it must be cleaned in sulphuric acid the same as any other wrought iron or steel. If it is bright wire all that is necessary is to immerse it in a solution of muriatic acid and water, 1 part acid to 6 of water. If wire is to be tinned in large quantities a long, shallow kettle is best adapted to the purpose. Tinning Steel Spoons and Similar Articles For tliis purpose provide a good sized kettle for "roughing" the work — that is, for giving the first coating. For finishing the work use small kettles. A kettle 15 inches long, 8 inches wide and G inches deep is amply large for finishing work of this kind. We refer to a plant fitted especially for this business. The work can 120 GALVANIZING AND TINNING be done in an outfit such as we illustrate by Fig. 42, but large finishing kettles are not as well adapted to this business as small ones, as the tin in a large kettle is apt to become dull in color by constant use, while in a small kettle the tin is renewed more often, which allows it to hold its color much better. In preparing the articles they should be rolled in tumbling bar- rels with scraps of leather and then carefully cleaned in an alkali solution. After rinsing off the alkali they should be immersed in quite a strong solution of muriatic acid and water for five or ten minutes, and then dipj)ed in the roughing kettle by means of a Avire basket, first dipping the work in a solution of muriate of zinc. As soon as they are thoroughly coated shake them out of the basket in such a way as to insure the separation of as many as possible. It makes no difference whether they come smooth or not so long as they are tlioroughly coated. The smoothness will come in the finishing operation. To finish the goods take one piece at a time in a pair of tongs adapted to holding them and immerse them in the finishing kettle, the tin in which is covered with beef tallow to the depth of about J inch. As soon as the article reaches the same heat as the tin remove it and allow it to cool until the tin will not run, after which wipe off the goods in flour. CHAPTER XVI Re-Tinning THE term re-tinning refers to the re-coating of pressed or stamped ware with tin. In the process of manufacturing tinware from tin plate by stamping or pressing, the origi- nal coating on the sheets is partly destroyed; hence, it becomes necessary to "re-tin" them; i.e., give them another coat of tin. It requires no little amount of skill to operate a re-tinning plant successfully, and satisfactory results are only obtained after long practice. For this reason, we omitted any extended mention of the art of re-tinning in the first issue of "Galvanizing and Tin- ning." Since the book was published, however, we have had so many communications from parties seeking information on the subject that we have decided to try and explain the process to the best of our ability. While perhaps our explanation will not enable the unskilled to successfully operate a re-tinning plant, it is hoped that what we have to say on the subject will not only prove of assistance to the novice, but to those already engaged in the business. Plant and Equipment The illustrations show the construction of a re-tinning stack Avithout going into dimensions, as the dimensions of the various kettles can only be determined by the class of work that it is desired to handle. We might say, however, that our illustrations of the kettles and brickwork of a re-tinning stack were made from a plant in operation on re-tinning ordinary kitchen ware, such as pressed dish pans, wash basins, etc., etc.; the actual dimensions of the kettles designated as A and C in Fig. 48 being 30" square. The dimensions of the kettle shown in the same Figure as B are 24:" wide, 30" long and 2V deep, while the small kettle desig- nated as D, known as the "listing" kettle, is 6" wide, 12" long and from 3" to 4" deep. As indicated by Figs. 48 and 49 the outfit for a re-tinning plant consists of four kettles, A is what is known as the "soaking" kettle, and is used to contain molten beef tallow. B contains the 121 laa GALVANIZING AND TINNING molten tin and is known as the "tinning" kettle. C contains beef tallow and is known as the '-finishing" kettle, while D contains molten tin and is known as the "listing" kettle. The soaking kettle A contains beef tallow. In this kettle are immersed in rotation articles to be re-tinned. When the goods are received in the re-tinning room from the stamping room for vv7/y//X/////yy ^m re-tinning, they are covered with various substances that have been used in the stamping room to facilitate the stamping opera- tion. This foreign substance usually consists of a solution of grease and soap, which must \)Q. removed before the articles are in proper condition for re-tinning. The soaking kettle is required not only for the removal of all foreign substance that has accum- ulated on the articles in the process of stamping, but to bring them to the proper heat for immersing in the tinning kettle B. In order to have the work proceed uniformly and systematically the soaking kettle A is provided with a rack or container, the general construction of which we illustrate by Fig. 50. The in- tent of these racks or containers is to prevent the articles from "nesting" together in the soaking kettle, thus retarding or entirely RE-TINNING 123 defeating the object for whieh this kettle is used. Ilcnce, it is obvious that these racks or containers must be made with a view to the proper accommodation of the articles to be handled. For instance, what is known to the trade as a six-quart pan would require a rack or container of a different size than would be used for a pan or article twice its size. The rack or container Fig. 49 — Plan of Re-tinning Furnace has another use; viz., that of preventing articles touching the sides of the kettle itself or sinking to the bottom and coming in contact with the refuse matter that has been removed from them in the process of "soaking." In this connection we will explain that whatever foreign substance is removed from articles sub- jected to the "soaking" process settles to the bottom of the kettle and in time becomes so hard that it is necessary to use consid- erable force to remove it. It often requires the use of a sharp bar to detach it from the kettle. The removal of this sediment is something that must be done at intervals of probably two or three weeks, although it may be found necessary on rare occasions to effect its removal at more frequent intervals. There are certain classes of stamped ware that do not require being held apart in the soaking kettle by a device such as we illustrate by Fig. 50, for the reason that their construction effec- tually prevents them from "nesting" together tightly or in such 124 GALVANIZING AND TINNING a way that the hot tallow in the soaking kettle could not readily effect the removal of whatever foreign matter has accumulated in the "stamping" or "spinning" process. The operator will readily understand that dishes with handles could not, owing to their construction, "nest" closely together. In such cases it is only necessary to use a rack or container that will effectually prevent the ar- ticles from settling to the bottom of the kettle or com- ing in contact with its sides. If the articles being treated do come in contact Vfith the sides of the kettle they are apt to be burned, which might effectually prevent their taking the tin, or they ■ci cr> T> ^ o T^7 might become badly fouled Fig. 50 — Rack for Tinning Small Work *=> -^ with the sediment by touch- ing the bottom of the kettle. Where division racks in the con- tainer are not necessary, a wire basket of suitable size can be used. It is, of course, necessary to construct this wire basket or container in a way to obviate danger from the conditions just described. We have described the intent and use of the soaking kettle at considerable length for the reason that on its proper use, or, per- haps we should say, upon the proper preparation of the articles in the soaking kettle, depends almost entirely the success of sub- sequent operations. As the soaking process proceeds the supply of tallow in the kettle decreases; hence, it is necessary to add fresh tallow from time to time as the work goes on, or as fast as it is lost by evaporation, or burned, it often being ignited from over-heating. It also often happens that the tallow will ignite when the racks are removed at the end of the day's work, and, owing to this constant danger of fire, the several kettles must be provided with tight covers, which constitute the most practicable way by which the flames can be smothered. Where articles are being treated that require the use of racks or containers, a sufficient number should be used to insure constant and rapid operation. As from four to five minutes' immersion in RE-TINNING 125 the soaking kettle is required on work stamped from heavy sheets, a suthcient quantity of containing racks should be provided to insure uninterrupted operation ; viz., enough so that the operator will always have a pan in the soaking kettle in proper condition for immersion in the tinning kettle. It, of course, necessarily fol- lows that after the container is once filled the operator replaces articles as fast as removed with others. The kettle designated us B is for containing the molten tin in which the work is immersed after it has been prepared in the soaking kettle A, The method commonly used is to have the man operating the soaking kettle pass the articles as fast as they are prepared over to the operator at the tinning kettle; using for the purpose a pair of tongs of proper construction, or, perhaps we should say, of proper shape, meaning of a shape fitted to the article and one that will not have a tendency to bruise or break it. When the operator on the soaking kettle has removed an article from his kettle he immediately immerses it in the tin con- tained in the kettle B, drawing it up and leaving it on the sur- face of the tin to be handled by the tinner, who grasps it with suitable tongs and again immerses it in the tin, manipulating it rapidly and in such a way as to prevent, so far as possible, any dross or, as it is termed by tinners, "scruff" from attaching itself to the article being handled. At this point the skill and experi- ence of the operator is exercised in keeping the tallow, which has been carried over from the soaking kettle, from attaching itself to the article being handled. AVe cannot very well describe the motions necessary to accomplish this object, as they can only be learned by experience. We wish to make it plain, however, that under no conditions must any of the grease from kettle A or B be allowed to be carried over into kettle C, as, in such a case, the contents of kettle C would be so badly contaminated that it would be impossible to produce good and satisfactory work. After the tinner who operates kettle B has accomplished the act of prop- erly removing the article in hand from the tin kettle B he places it in kettle C, which has been provided with racks for the holding of such articles as racks are necessary for in kettle A. Even the proper transferring of articles from kettle B to kettle C requires no little amount of ingenuity and experience. The im- mersion of articles from kettle B into kettle C must be accom- plished v/ithout rippling or disturbing the finishing tallow in ket- 126 GALVANIZING AND TINNING tie C more than necessary, and the removal of articles from the finishing grease in kettle C must be accomplished in the same careful manner ; viz., so as not to disturb or agitate the hot grease. While it is essential that the tallow in the finishing kettle be kept clean and maintained at a uniformly proper heat, the best results are obtained after the tallow has been used for a time. In fact, satisfactory results cannot be obtained if the grease in this kettle contains too great a percentage of new tallow, or, as the operator would say, is too "sharp/' meaning that if the tallow is too fresh and new the finished work will either be streaked or have the coating removed in places. As the o1)ject of this ket- tle is to remove all surplus tin possible, it will readily be seen that it is necessary to bail out the tin which accumulates in the bottom of the kettle at frequent intervals. In large plants this is usually done at the end of the day's work, at which time all the tallow in the kettles A and C is removed, principally to obviate the danger of its igniting through the night, at which time the fires are usually in charge of the watchman. As each article is removed from kettle C the operator holds it in a position that will permit of what little surplus tin is left running to a given point, so as to permit its removal. This is accomplished by using a short rod of iron that is kept constantly immersed in the listing kettle. As soon as the drop has formed, and before it has time to harden, the operator takes the rod from the listing kettle in his left hand and draws it quickly and evenly over the place where the drop of tin has formed, much in the same way that a tinsmith would remove solder with his soldering cop- per. This explains the use of the listing kettle D. It is simply used for containing sufficient tin in a molten state for immersing the end of the listing rod, so that it will always be handy and in proper condition for removing the drops of tin as they form on the finished work. The proper degrees of heat for the contents of the different kettles can only be determined by experience and practice. The tallow in the soaking kettle A must be maintained at very close to the heat of the molten tin in the tinning kettle B, and it is obvious that the tallow in the finishing kettle C must also be maintained at approximately the same temperature. No more than two articles should be immersed in the finishing kettle at one time. If there are, one is almost sure to be spoiled. RE-TINNING 127 As wo have explained, this finishing kettle C is used for remov- ing tiie surplus tin, and for this reason is called by tinners the "skinning" kettle. In handling very large work the racks or containers are left out of the soaking kettle, and in their place a sheet of tin is dropped into the bottom of the kettle so as to keep the articles off the bottom. This sheet should be taken out at night. As fast as the work receives the finishing touches from the man operating the finishing kettle, it is placed on racks and allowed to remain there until it is cool enough to be handled by the operators who give it the final finish. The finishing force for a re-tinning stack usually consists of three girls. For their use a long bench, E, Fig. 4:9, is provided. The first operator gives the work a thorough rubbing in dry soft sawdust contained in box F. The second goes through the same operation with SAvadust, mixed with what is known as "middlings" or wheat bran, and contained in .box G, while the third performs the same operation with a cheap grade of flour, contained in box H. From there it is finished at the wiping bench J. We will say, in a general way, that it is not necessary to im- merse articles that are to be re-tinned in acid unless, by chance, they have become rusty through carelessness in some operation or by letting them stand too long after leaving the stamping ma- chines. When it is necessary to remove rust by the use of acid, the articles must afterward be thoroughly rinsed in clean water, after which they should be dipped into boiling hot water and carefully and thoroughly dried liy the use of saAvdust. In providing tongs for handling the work through the various kettles, only those made of steel should be used, and they should be carefully cleaned and coated with tin before being used. Care should be taken to select tongs suited to the variety of shapes being handled. As dross forms in the tinning kettle very rapidly, it is neces- sary to take measures to prevent its interfering with the work. This is done by an operacion known as "boiling" the tin, and is accomplished by forcing a large block of green wood, preferably white pine, to the bottom of the tinning kettle and causing it to remain there the desired time by some simple device adapted to the purpose, usually by means of a rod of iron inserted in a hole bored in the l)lock. These blocks of green wood should be previ- 128 GALVANIZING AND TINNING ously dipped in hot tallow ; otherwise, they would cause the molten tin to spatter in all directions when the blocks were immersed. In order to facilitate the removal of the kettles from the brick work when it is necessary to replace them for any purpose, and also to assist in the removal of the containers in the several kettles when it is desirable to remove them, a strong bar of iron should be built into the stack high enough to permit the use of a chain hoist. A few bars or rods of iron should also be built into the stack above the kettles, on which sheet iron can be laid to pre- vent the soot that gathers in the stack from falling into the ket- tles and thus spoiling the contents. Fig. 48 is a sectional elevation of a re-tinning stack, and, as shown by Fig. 49, the kettles are fired on the opposite side from where the workmen stand when operating the kettles. In order to have easy access to the fires and to facilitate the removal of ashes, a pit is provided which should be large enough to attain its object. The depth of the pit is governed entirely by the depth of the kettles. It will be observed by referring to Fig. 48 that the kettles are heated on the sides, as well as on the bottoms, which is accom- plished by means of spiral flues designated as K : these spiral flues having an outlet into the large flue L, shown in Fig. 49, and which is a separate flue from the one designed to carry off the fumes and smoke rising from the kettles. CHAPTER XVII Tinning Gray Iron Castings ONLY a few years ago all articles used in the preparation of food which were made of gray iron were zinc coated or galvanized, as they could not be tinned satisfactorily. This fact, and the fact that tin was a much more desirable metal than zinc for coating articles used for culinary purposes, was largely responsible for a method of tinning gray iron which was perfected by the author. To-day it is almost impossible to sell zinc-coated articles used in the preparation of food, as such articles made of gray iron are now tinned extensively. For example, ice cream freezers, lemon squeezers, meat cutters, bread and cake mixers, egg beaters, fruit stoners, vegetable cutters, etc., made wholly or in part of gray iron and tinned are now sold imiversally. In addition to the uses to which tinned gray iron is put by the manufacturers of kitchen and other hardware specialties, it has been found of great advantage to give articles of cast iron that are to be copper or brass plated a coating of tin previous to plating them. The advantages come from the lessened quantity of material necessary to use in electroplating, the preventing of "leaking" or "sweating," so common where the plating is deposited directly on the bare casting, and also from giving the articles the appearance of spelter or brass castings. By this process gray iron castings are prepared for tinning by rolling them in a solution of muriatic acid, sal ammoniac and water, the rolling barrel being constructed to retain, under pres- sure, the gas formed by the chemicals used. The use of this bar- rel makes it desirable to locate the tinning plant in a building by itself, as the gas generated is constantly escaping, carrying with it quantities of the solution. At the best the rolling room for gray iron tinning is a wet, dirty place, and the entire operation re- quires the use of considerable water. Plant and Equipment In erecting a building for this purpose particular attention should be paid to ventilation and drainage. A plan for constructing a 129 130 GALVANIZING AND TINNING floor, with a view to perfect drainage, is shown by Fig. 43. Two or more kettles (depending on the nature of the work), set after the plan illustrated by Figs. 52, 53 and 54 and various tanks built after Fig. 24, complete the outfit. The arrangement of the outfit Fig. 51 — Arrangement of Tinning Plant •is shown by Fig. 51, in which A is the rolling barrel for preparing the castings for tinning. B is a tank to receive the castings after they have been treated in the rolling barrel A. This tank should be provided with trucks, and a track should be laid so that the tank can be run under the rolling barrel to receive the prepared work. C is a water tank for storing the prepared castings after rolling, as hereafter described; D, E, F and G are divisions of one common tank; D is to contain an alkali solu- tion, and should be provided with a steam coil, as shown, to heat the solu- tion; E is a compartment for contain- ing water for rinsing; F is to contain an acid solution; G is for the muriate IS tne rougning kettle of tin; K is the fiin- ishing kettle; L is the kerosene for cooling: the work. The Fig. 52 — Front Elevation of zinc; H is the roughing arrangement of this tank was explained in the chapter on TINNING GRAY IRON CASTINGS 131 general tinning; M is a wooden tank large enough to ac- commodate the iron tank L and allow it to 1)C surrounded with water: N is a tank for containing hot water, in which the Fig. 53 — Side Elevation of Tinning Furnace tinned work is dipped to remove any traces of oil or acid, and is provided with a steam coil, as showai; is a box to contain sawdust for drying oil the work when it comes from the hot water Fig. 54 — Plan of Tinning Furnace at Grate Line contained in the tank N ; E E is a drain for carrying off the waste water, and S S are the tracks for moving the tanks B and C; T is a tank for containing a solution of hydrofluoric acid, used as hereafter described, and U is a storage tank. It is perhaps 132 GALVANIZING AND TINNING needless to say that tlie ground plan may be changed to suit local conditions. Only the most simple tools are required, which may be varied Ijv the ingenuity of the operator to suit existing conditions of work. We give a sketch showing the most common in Fig. 35. CHAPTER XVIII Preparing Gray Iron Castings for Tinning IN PREPARING gray iron castings to take a coating of tin there are several essential things to be taken into considera- tion ; viz., the quality of the iron, the form of the castings, their condition when they come to the tinner and, if cored, the nature of the cores used. Hard iron requires longer preparation than soft iron and a longer immersion in the molten tin. Castings made from patterns not designed with a view of avoiding sharp angles, and in which molding sand can easily find lodgment, are much more difficult to prepare than those made from patterns free from such hindrances. It is, of course, not always possible to do away with sharp angles in making patterns for castings that are designed to be tinned, but whenever possible they should be avoided in the interest of easy cleaning and perfect coating of the work. Castings that have been freed from sand by the use of sulphuric acid require a special preparation before they will take a perfect coating of tin, and the use of this acid for this purpose should be avoided if possible. Cored castings made with cores in which rosin has been used must be treated differently from those made with an oil or glue core. For the intelligent understanding of the different conditions we give the specific course to be followed in each case. The perfect coating of gray iron requires the use of two tin- ning kettles, and where castings are to be tinned previous to elec- troplating three kettles of tin should be used to insure the smooth- est coating and the brightest luster. Removing Sand from the Castings The first operation in preparing the castings for tinning is to free them from sand. This is best accomplished by the use of the ordinary tumbling barrel, which gives the castings a smooth, clean surface while removing the sand. "Where the castings are of a nature which prevents their perfect cleaning by tumbling, the sand should be removed by a solution of hydrofluoric acid and 133 134 GALVANIZING AND TINNING water. Sulplmric acid will do the Avork, but in a much inferior manner and to the detriment of the castings as regards their easy and perfect coating in the tin. The reason for this is easily under- stood. Hydrofluoric acid acts directly on the sand, dissolving it rapidly without attacking the iron to any great extent. The action of suljDhuric acid is just the reverse, the iron being dissolved on the surface of the casting, causing the sand to fall off, the sand itself not being affected. Freeing Gray Iron Castings from Sand by Hydrofluoric Acid While this operation is about the same as given for cleaning malleable iron by the use of this acid, we wish to impress the operator with the fact that in treating gray iron with acid of any kind, in preparing it for tinning, much more care must be exer- cised in the operation than with malleable iron, as the over- pickling of gray iron leaves the surface soft and gummy, in which condition it will not take a coating of tin and it is no easy matter to put it in a condition where it will. For quick cleaning of sandy castings by the use of hydrofluoric acid the preparation should be 1 of acid to 20 of water. For slow cleaning, which is necessary on castings having sharp angles into which the molding sand has burned, use the acid in the proportion of 1 of acid to 30 of water. The castings may remain in this solution until the sand is dissolved, after which, provided they have not been made with rosin cores, they are ready to be placed in the tuml)ling barrel used to prepare them for tinning. If rosin cores have been used the castings are to be treated in a special way, which will l)e explained in its turn. A good arrangement for cleaning sandy castings with hydro- fluoric acid is to have two tanks (oil barrels sawed in half will answer), one elevated alcove the other by means of a stand or bench, so that the top of the lower tank will be 3 or 4 inches below the bottom of the elevated tank. Bore a hole in the side of the upper tank close to the bottom and provide a plug. Place the castings in the upper tank and cover them with the hydrofluoric solution, which is contained in the tank below. When the cast- ings have been completely freed from sand remove the plug and allow the solution to escape into the tank below, where it remains until required for use again. No specific rules can be given as to the time required to clean castings, and it is not necessary, as PREPARING GRAY IRON CASTINGS FOR TINNING 135 an examination of the work from time to time wliile under treat- ment will determine wlien they are clean. Castini^s on which a light deposit of sand is attached may be clean after 15 minutes' im- mersion in the solution, while castings having a heavy coating of sand, or on which the sand has burned, may require 3 or 4 hours. If the nature of the sand on the castings makes it seem prob- able that they will require a longer immersion in the acid, weaken the solution by the addition of water to a point where there can be no possible danger of the castings being affected in the way mentioned in the beginning of this subject. Cleaning Sandy Castings with Sulphuric Acid If sulphuric acid is used to free the castings from sand, place them on an inclined, raised, platform, which platform should be of a size to accommodate the intended production and arranged to allow the solution to flow back into a tank placed at the lowest point to receive it. Make the solution in the proportion of 1 of acid to 6 of water, and keep the castings wet with this solution until the sand can readily be removed by a stream of water. Gray iron castings cleaned in this way will have a soft, gummy surface, and will not take as perfect a coating of tin as castings cleaned by dry tumljling or by the use of hydrofluoric acid. They must be given a special treatment before tinning, which will be described in connection with the treatment of castings made with rosin cores and hard or greasy castings. Cleaning Castings with the Sand Blast In addition to the methods already described for preparing gray iron castings for tinning, the reader should not lose sight of the fact that the sand blast is a valuable agent for this pur- pose, and we strongly advise those who have sufficient work to warrant the installation of a sand blast plant to carefully inves- tigate its possibilities. ' Special attention is given to this subject in Chapter VI, pages 51 to 65. The Use of a Hot Alkali Bath in Certain Cases After the castings have been freed from sand in some one of the ways described, provided they have not been over-pickled, or made with rosin cores, or greasy, and have not been faced with black lead facing, or picked with sulphuric acid, they are ready for tumblino: in the solution of muriatic acid, sal ammoniac and 136 GALVANIZING AND TINNING water. If any of these conditions should prevail, the castings must be given a treatment in a bath of hot caustic soda or soda ash. If castings have been over-pickled — that is, left in the pickle until the surface has become covered with a soft, gummy sub- stance — or if rosin cores have been used in making the castings or black lead facing used to give a smooth surface, or if grease or paint is present, they must be immersed for several minutes in a boiling solution of caustic soda or soda ash. Make the solu- tion very strong, and see that the strength is maintained by adding fresh material as needed. After this treatment the castings must be thoroughly washed with clean water before they are placed in the rolling Ijarrel used to prepare them for tinning. D in Fig. 30 designates the tank to be used for the hot alkali solution and E, in the same illus- tration, is the tank used for rinsing. Tumbling Special care is required in preparing cast iron for tinning, in the tumbling barrel and a very comprehensive treatment of the subject is given in Chapter VI, pages 51 to 65. This material covers the construction, location, charging and operation of the barrel. The important point to keep in mind in preparing cast iron for tinning is that the surface of the iron must be made perfectly clean. Not only free from sand and rust, but from every foreign substance. It may seem to the reader that we are dwelling on this point unnecessarily, but only by the most careful attention to the proper preparation of the castings, and in the keeping of them in the same clean condition until they receive the first coat of tin, can perfectly satisfactory Avork be obtained. If the iron is allowed to roll in the solution too long a time the surface Ijecomes soft from the action of the acid and tlie tin will not take. The same trouble will be experienced if the solu- tion in the rolling barrel is too strong, or if the castings are allowed to remain in the solution too long after they are rolled. Water Rolling Where castings are tinned for the purpose of electroplating them, it is desirable, if an extra smooth surface is desired, to give them a rolling in gravel and water in the ordinary wet PREPARING GRAY IRON CASTINGS FOR TINNING 137 rolling barrel, although tliis treatment is not necessary in order to prepare tliem to take a coating of tin. In treating castings in this way use a coarse hard gravel, and some castings may be rolled 20 to 30 honrs to good advantage if the barrel is properly loaded. CHAPTER XIX Coating Gray Iron Castings with Tin THE tin ill the kettles being at the proper heat for the work in hand, as specified later on, the operator takes a small quantity of the castings from the storage tank C, Fig. 51, and places them in the wire basket designated A in Fig. 35, tak- ing care to place those having concave sides, holes or depres- sions so that none of the various solutions, through which they are now to pass, will be retained. The castings contained in the basket must now be immersed in the solution of caustic soda or potash, which is contained in tank D, Fig. 51. This solution must be kept at the boiling point, and from 1 to 2 minutes is svfficient time to leave the castings in. The best plan for heat- ing this solution is to have a steam coil in the bottom of the tank, as shown in the illustration, and to allow the exhaust steam to pass into the rinsing tank, which is placed beside it, as shown in the ground plan. The rinsing tank is designated E in Fig. 51. After the basket of castings has stood in the alkali bath con- tained in tank D for the desired time it is placed in the rinsing tank E until all traces of that solution are removed. This will take but a fraction of a minute, provided a stream of clean water is kept flowing into the tank, as it should be , In rinsing the cast- ings in tank E do not allow them to remain in the tank for any great length of time if water is flowing in, as iron will soon rust in running water. The next move is to immerse the basket of castings in a very weak solution of muriatic acid and water, 1 part acid to 40 of water. The tank for containing this solution is designated F in Fig. 51, and the castings must not be allowed to remain in it more than 2 or 3 seconds. The solution should be made up fresh after 2 or 3 tons of iron have passed through it. Next, place the basket of castings in the tank G, Fig. 51, which contains muriate of zinc, to which has been added 5 pounds of gray granulated sal ammoniac for every gallon of the liquid. Muriate of zinc is made by dissolving zinc in muriatic acid, allow- 138 COATING GRAY IRON CASTINGS WITH TIN 139 ing the acid to dissolve all the zinc it will. An earthen crock or a cleaned oil barrel can be u^■ed to make this cut acid in. This solution should be deep enough to cover the castings contained in the wire basket used for immersing them in the roughing kettle, and should be kept in good condition — that is, care should be taken to prevent its being weakened to any great extent by pass- ing the solution in tank F into it with the work. The tank for containmg this muriate of zinc should be lead lined, and an inner lining of wood used to protect the lead. The basket of castings is now ready to be immersed in the molten tin contained in the first, or roughing, kettle, and shown in Fig 51 at H The tin in this kettle should attain a heat of 500 degrees F., and this heat should be maintained during the time the kettle is in use. Before immersing the castings in this kettle the surface of the tin should be covered by a flux, made by boiling a quantity of the muriate of zmc on top of the molten tin, and adding quickly to the boiling mass a quantity of white granulated sal ammoniac. The sal ammoniac must be added by sprinkling it on before the acid is evaporated by the heat of the tin It will take a little time and experience before the proper consistency of this flux can be attained The proper making of this flux is one of the most essential points in the successful coating of cast iron in this first kettle of tin. If the flux is allowed to become hard and dry, as it soon will by continued use unless careful and constant atten- tion is given to it, the flux will adhere to the castings as they pass through it into the tin below, and thereby prevent them from coating. When it is found that the flux is becoming thick and lumpy, add a sufficient quantity of muriate of zinc and powdered sal am- moniac to cause the flux to boil up to a depth of ^ inch or more. When this result is obtained take a perforated iron skimmer and carefully remove any hard lumps and congealed matter remain- ing in the flux, allowing such as readily pass through the skim- mer to remain in the kettle. The purpose of this flux is to pre- vent the surface of the tin from becoming oxidized by exposure to the air, and also to prevent the hot metal from spattering and burning the operator when the wet castings come in contact with the tm. Bear carefully in mind that this flux must at all times be kept in a thin liquid condition, otherwise the succeeding opera- 140 GALVANIZING AND TINNING tions through which the castings are to pass before they are com- pleted will be unsuccessful. In forcing the castings into the roughing kettle, care should be taken to get them immersed as soon as possible. If they are allowed to float on the surface of the tin the muriate of zinc, with which they are wet (for the purpose of causmg the tin to adhere), will dry off, and the tm will not adhere to the part of the casting thus exposed The castmgs must be kept below the surface of the tin until they have become as hot as the tin itself, and until the tin has ceased to bubble or to be agitated by the castings that are immersed. This boiling or agitation will cease when the air and moisture is expelled from the iron and the flux, that adhered to it as it passed through, has risen to the surface of the tin. The proper way to immerse the work in this first kettle of tin is to rest the handle of the basket containing it on a block of iron placed on the edge of the tin kettle, elevating the basket at an angle that will prevent it touching the molten tin until the operator is ready to have it. Cant the basket so that one of the lower edges will enter the tin first; in other words, do not allow the flat bottom of the basket to come directly onto the surface of the tin, as the effect of having as much wet metal as the bottom of the basket presents coming in contact with the molten tin will be an explosion, resulting, perhaps, in the serious injury of the operator or some one standing near. When the basket is in the described position, lower it carefully until 1 inch or 2 inches of the bottom and one side is immersed in the tin, then lower rapidly, but steadily, until the basket and its contents are completely immersed. At this point turn the basket completely over, bottom up, and, using the edge of the tin kettle as a rest for the handle, lift the basket from the tin when it is free. Turn it bottom down and use it in that position to keep the castings it contained below the surface of the tin until they reach the heat of the metal. Fill the kettle with as many castings as it will hold and allow them to be completely immersed. Several of the wire baskets may be employed to insure having a batch always ready to immerse when a previous one has been disposed of. It sometimes happens that the operator carelessly omits dip- ping the work in the cut acid contained in tank G, Fig. 51; that COATING GRAY IRON CASTINGS WITH TIN 141 is, he may attempt to immerse the work in the molten tin directly from tank D, E or F. Such neglect is dangerous and likely to be attended with serious results to the operator, due to spattering of the hot metal. There are many kinds of castings that may be strung on wires and handled through the different stages without the use of wire baskets. When wires are used the shape may be varied to suit conditions. While we show the most common in Fig. 25, the ingenuity of the operator mu3t ho employed in selecting and de- vising those best adapted to his wants. The kettle being filled, as described, the castings must now remain where they are for from 5 to 15 minutes, or until they have taken a perfect coating of tin. If, in this time, they are not properly coated, some error has been made in the previous operations and the work must l)e re-rolled. What dross or slag forms in a tin kettle rises to the surface. A considerable part of this objectionable matter will be found in the first kettle, and must be removed before the work can be car- ried to the finishing kettle or kettles. To accomplish the removal of this dross, or slag, floating on the surface of the tin, use a perforated, concaved iron skimmer. The holes in the skimmer should be large enough to allow the clear tin to flow through freely, and care should be taken not to waste the flux in skim- ming out the dross. If the skimmer is canted edgewise the dross will adhere to the skimmer, while the flux and clear tin will flow back into the kettle. When all the dross has been removed from the kettle, grasp one of the castings with a pair of tongs and remove it with a quick motion from the tin. If wires have been employed for stringing the work, take one or more wires and remove in the same way to the next kettle, taking care that no flux or dross is carried along with the work. The temperature of the tin in the first kettle is much too high for finishing work, and when the castings taken from it are exposed to the air they will turn more or less yellow, depending on the heat of the tin. A bright yellow or golden color indicates too high a heat and must be avoided. A slight yellowish tinge indicates the proper heat. The tin in the second kettle, which is designated in Fig. 51 as K, and which, in most cases, is the finishing kettle, must be main- tained at a temperature of about 400 degrees F., and the surface 142 GALVANIZING AND TINNING must be kept covered to the depth of from ^ to 1 inch with pure beef tallow. Palm oil may be introduced into the tallow with good results, using about 10% palm oil. The operator keeps the cast- ings held by the tongs or wires immersed in this second kettle 1 or 2 seconds and then, with the tongs held in the left hand, he removes the piece from the tin. As soon as the piece is clear of the tin the operator grasps it with another pair of tongs held in the right hand and, after a few rapid swinging motions to free the article from surplus tin, plunges it into the tank containing kerosene oil. If wires are being used he swings the work to and fro rapidly to free it from the surplus tin, and when plung- ing it into the oil he must give the work a motion calculated to prevent the articles in contact from adhering to each other. The tank, which is designated in Pig. 51 as L, should be of sheet iron and placed in the companion tank ]\I with the idea of having running water surrounding it to keep the kerosene from becoming over-heated, as it soon would be from having hot cast- ings continually immersed in it. The work must be immersed in this oil long enough to set the tin and then immersed in the cold water contained in the companion tank M. If the tin in the finishing kettle is at the right temperature the work will be white and have a nice luster after it is cooled. If the work is rough and lumpy it indicates that the tin in the finishing kettle was not hot enough or that the work was kept in the air too long a time before dipping it in tlie kerosene. The tin in the finishing kettle requires very little fire to be maintained, as there will be nearly enough heat in the castings brought from the first kettle to keep the tin in the second at a proper heat. If the work is yellow after cooling in the oil it may indicate too high a heat in the finishing kettle, or it may indicate that the casting was not kept in the finishing kettle long enough to bring the heat that the casting attained in the first kettle down to a point where the tin would not turn yellow. Work can be taken from the finishing kettle smoothly and brightly coated even Avhen the temperature of that kettle is so low that if a piece of cold iron be put into it the tin would adhere to the iron in a thick mass. The heat the castings attain in the first kettle makes it possible to run the finishing kettle at a very low temperature, and it is advisable to do so on very heavy castings. Light castings require that a much higher heat be (()Aiix(; (;ray iron castings with tin 143 maintained in tlio iinishing kettle than is necessary for heavy castings. The reason is apparent: All castings must be exposed to the air a few seconds while the operator is switching off the surplus tin. If the castings are light and the tin is cold they will not hold the heat long enough to allow the surplus tin to be shaken off without leaving rough, ragged edges. A great deal of ingenuity can be displayed by the operator in the handling of castings of various shapes in such a way that no lumps or bunches of tin will remain on the work after it is cooled. For example, care should be used to ascertain what part of a casting is best adapted to Ije taken hold of by the cooling tongs without leaving marks of the tongs after the article is cooled. The tongs used for cooling should never be put into the tin kettle, as the heat of the casting would cause it to adhere to the tongs if they were tinned. After shaking off the surplus tin, change the position of the casting so that the drop of tin, which will naturally collect at the lowest point, will flow back into the coating on the casting, and dip it in the oil at once when this is accomplished. A "switching box" should be employed, when "strung" work is being handled, to catch the tin that is thrown from the work in the operation of "switching" it to throw off the surplus metal. This box is a very simple affair. Its position, when in use, is designated D, Fig. 33. Cover the interior of the box with heavy paper, as the hot tin will stick to the wood unless paper is used. The tin thus collected may be thrown into the kettle with the paper when the tin is needed for use. When the castings have l^een cooled, as already described, they should be immersed in a tank of boiling water to free them from oil and also to remove any trace of acid that may be on them. This final rinsing tank is designated N in Fig. 51. The water must be kept clean and at tlie boiling point at all times when in use. An ordinary foundry riddle, with upright handles long enough to allow the operator to set the riddle containing the work to be rinsed into the tank without scalding his hands, may be employed. The castings should be dried oft' in clean dry sawdust, and that made from pine or some soft wood is best, as hard wood sawdust will scratch the tinned surface. The drying box is shown at in Fie-. 51. 144 GALVANIZING AND TINNING When three kettles of tin are employed, as they may be to good advantage in tinning work that is designed to be plated, the second kettle must be run at a temperature of 450 degrees F. The surface of the tin in this kettle must be kept covered with an acid and sal ammoniac flux the same as the first kettle. The castings in the first kettle are passed in quantities to the second kettle, there to remain until the first kettle is refilled. As when using two kettles, care must be taken to prevent any of the slag or flux that accumulates on the first kettle from passing with the work into the second kettle, and the tin in the second kettle must be kept free from slag. The tin in the third or finishing kettle should be maintained at a temperature of 400 degrees F., and the depth of the tallow increased to 3 or 4 inches. If three kettles are employed they should be square or round, and arranged to fire from one side instead of from the ends. As it is almost impossible to satisfactorily tin castings which have been imperfectly coated at the first attempt, the operator should give careful attention to details. It is comparatively easy, with practice, to keep the tin at a proper heat, but the beginner will find more difficulty in doing this than any other one thing in the entire operation. That the proper heat be maintained is very essential, for if it is not all previous care in preparing the work will have been in vain. If too hot the flux on the roughing kettle will evaporate or burn off, and the tin will not coat the iron. If too high a heat is reached on the finishing kettle the tallow will be set on fire. As a help to the novice and, in fact, to the experienced man, we recommend the use of pyrometers; one for each kettle. The expense of pro- viding them is not to be considered in comparison with the ad- vantages obtained by their use. The kettles for containing the tin usually are made of cast iron, although fire box steel is often emj)loyed to make oblong kettles. A fioor space of 20 x 40 feet will accommodate a tinning plant having two rolling barrels. If possible, the plant should be lo- cated handy to power and with a view to obtaining easy and per- fect drainage. If necessity compels locating the plant in a fac- tory building above the ground floor, as is sometimes the case, the COATING GRAY IRON CASTINGS WITH TIN 145 floor of the. tinning and rolling rooms must be so constructed that leakag-e into the room or rooms below will be impossible. The dross or slag formed in the kettles should be stored away until a sufficient amount lias accumulated to make profitable the remolting of it to reclaim what pure tin is in it. For the pur- pose of remelting this dross the pure tin can be removed from the kettle II, Fig. 51, and the dross melted up in it. When the entire mass is in a molten state, and at a temperature of about 550 degrees F., l^ail off the good tin into cast iron pans provided for the pui'posc, and the dross which remains into separate pans. This tin dross has a market value of from 40 to 50% of the price of pig tin. With the addition of tanks for containing cleaning acids, a plant built to tin cast iron is adapted to all descriptions of tinning, excej)t re-tinning of tinware and the tinning of sheets. CHAPTER XX Cleaning Old Galvanized and Tinned Work GALVANIZED material becomes dark or discolored from age or exposure and from various other causes. Gal- vanized sheet iron is often found to be covered with a white deposit, which discolors them even when the stock has been kept under cover, and it is almost sure to be found if it has been subjected to changes of temperature which have caused mois- ture to gather on the sheets. On galvanized castings the discolora- tion is seen in the form of a white powder which forms on their surface, or, if they have been stored in a room not subjected to marked variations of temperature, their surface simply turns dark. While it is practically impossible to prevent this discoloration, and while it is not particularly detrimental to the wearing qual- ities of the coating, it is often detrimental to the sale of the mate- rial, as few care to buy goods that have a "shop-worn" appearance. The appearance of discolored material may be materially improved, however, and sometimes made to look like new, by dipping it in a cold solution of one part sulphuric acid to ten parts water. The material should not be left in the acid dip more than two minutes at the most, and as much less as possible, and accomplish the desired result. Neither should the material be subjected to fre- quent dippings, as it will become permanently stained by so doing. As soon as the material has been removed from the acid solution, it should be immediately rinsed thoroughly in clean, cold water, after which it should be immersed in a bath of boil- ing hot water, and carefully dried off in dry sawdust. Cleaning Old Tinned Work Tinned work that has been subjected to considerable handling, or that has been machined, will invariably lose its luster. While the original luster cannot be completely restored, the appearance can be improved by dipping the material in a hot solution of sal- soda. Make the solution rather weak; a pound of sal-soda to a gallon of water will usually be found strong enough for ordinary 146 CLEANING OLD GALVANIZED AND TINNED WORK 147 purposes, and a weaker solution should be used if it will accom- plish the desired result. As soon as the work is removed from the sal-soda solution it should be carefully and thoroughly rinsed in clean, cold water, and then immersed in clean, boiling water, after which it should be dried ofE and rubbed in dry pine saw- dust, to which a little flour has been added. If dry sawdust is not available ordinary bran will answer the purpose very well, provided all moisture on the work has been allowed to evaporate before the bran is used. CHAPTER XXI Electro-Galvanizing Plant and Equipment THE art of electro-galvanizing and its industry is not the result of an invention, but was simjDly created within the last twenty years by force of necessity in protecting such articles like springs, small wire netting, screws, bolts, nuts, etc., which could not up to that day be satisfactorily galvanized by the hot process, and this shows clearly that the creation of the electro- galvanizing industry was not a matter of cost. The cold galvanizing has its advantages, being suitable for treat- ing a large number of different articles, especially goods that have been hardened and tempered and all kinds of machine parts with perforations and threads ; also in the continuous processes for band iron, wire and the galvanizing of small articles, such as tacks, nails, etc., in bulk form. The hot galvanizing cannot compete in the satisfactory produc- tion of these articles, and, on the contrary, the electro-galvanizing never will compete with the hot galvanizing on such articles as tanks, boilers, architectural iron and building material, etc. One of the earliest records of electro-galvanizing is an English patent taken out by Charles Cleophas Person, on April 27, 1854, and reads as follows: Coating with Zinc by Galvanization. "The zincing is effected by electro-deposition from a bath con- taining salts of zinc and alumina. The solution may be prepared by dissolving precipitated alumina in a solution of sulphate of zinc, but the inventor prefers to dissolve oxide of zinc in a solu- tion of crystalized alum. The zinc may be deposited from such a solution on all metals, viz. : iron, copj^er, platine, etc., and the adhesion is complete : if care is taken previously to make the sur- face of the article bright." It is only within the past decade that any marked advance in the commercial use of electro-deposited zinc has been noted, and it is in the United States that the deposition of this metal, by means of a low-tension current, has reached its highest commercial development. While the knowledge that zinc could be readily 148 ELECTRO-GALVANIZING PLANT AND EQUIPMENT Un deposited has existed Tor a lono; nunilxT of years, ilic ])i'0('ess was never taken u}) in a praetieal commercial way niitil al)oiit li)00. At tliat time attention was directed to the subject thron*>-h experi- ments made by the governments of England, Germany and the United States, which demonstrated the efficiency of the electro deposit for certain classes of work. In line witli the experiments M'liich liad been made, the United States Government established tests and installed small electro-galvanizing jdants at various arsenals and shij^yards throughout the country. Manufacturers of electro-plating materials availed themselves of the information ))rought to their attention, and during the past ten to twelve years the growth of this industry has been rapid and electro zincing or galvanizing is now being applied to many iron and steel articles which could not as readily be treated in any other way. Equipment for Electro-Galvanizing Plant An electro-galvanizing plant may be subdivided into two im- portant departments — the cleaning department and the galvaniz- ing department proper. In the cleaning department the equip- ment consists of: 1. Suitable tanks, a. For sulphuric or hydrofluoric pickle, b. For hot potash, c. For electro-cleaning. d. For washing and scrubbing. 2. Tumbling barrels or sand blasting apparatus for cleaning small material. The galvaniziiig equipment comprises : 1. Suital)le tanks or automatic devices, including rinsing and drying apparatus. 2. Necessary galvanizing solution. 3. Copper conductors. 4. Anodes. 5. Low-voltage generator. 6. Switchboard consisting of voltmeter, ammeter and rheostat. 7. Hot-water tank. This is the complete unit for a galvanizing plant with still tanks, and such equipment can be found in the plants of large 150 GALVANIZING AND TINNING metal maimfaeturcrs and maker.s of specialties througliout tlie country. Such a plant does not require any further explanation. A rough layout is shown in Fig. 55. Galvanizing is accomplished as an accessory to other' electro- plating activities or whole j^lants are devoted to galvanizing ex- clusively. Illustrations of the latter type are shown in Figs. 56 and m^m^>y. Fig. 55. Floor Plan of Electko-Galvanizixg Plant 57. Fig. 56 shows one of the most up-to-date electro-galvanizing departments in tlie world, j^ossessing jjerfect light and ^■cnti]ation and ample room for the oioerators to discharge tlioir duties. The plant shoAvn is that of the Spirella Company, Niagara Falls, jST. Y., and is devoted to the protection of the wires of the Spirella Corset products. Fig. 57 shows a remarkahle electrical installation, with 22 units supplying the current for the tanks shown in Fig. 56. At no point is the lead from the generator to the tank longer than' 10 feet. A special feature in this plant is the covering of the cyanide tanks with sliding hoods, as shown on the right in the foreground of Fig. 56. The fumes from these tanks are taken away from under the hood hy an exhaust blower. ELECTRO-GALVANIZING PLANT ANi:) EQUIPMENT I'A 152 GALVANIZINC4 AND TINNING ELECTRO-GALVANIZING ]>LANT AND l^C^UIPMENT 153 Mechanical Galvanizing and Patented Devices The foregoing pai-ag-raphs have dealt in general with electro- galvanizing, and, as the mechanical electro-galvanizing, in other words, the zinc deposition in bullv quantities, has so much merit, it is worthy of special mention. The increasing use of mechanical devices for electro-deposition aifords ample reason for an extended study of this juncture of the j)rinciples involved. In the mechanical electrical deposition of zinc, there is a higher voltage and amperage used, and through this in a shorter length of time more zinc is deposited than in still open tanks. Still open tanks can also ha made partly mechanical by agitating either the electrolyte or the goods to be plated. Some firms make it a practice to move the bus bar either horizontally or perpendicu- larly, or the electrolyte is agitated by blowing air through per- forated lead or ruljber tuljes from the bottom of the tanks, or ])y agitating the solution through a floating-tank system or by the means of a propeller. The above refers to all kinds of articles, especially such work which cannot be successfully plated in tumbling machinery and which has to be specially suspended on wires, hooks or racks. Also for this class of work various kinds of new machines and devices have been adopted to reduce the labor cost and shorten the time of plating. The Miller Chain Conveyer Machine Illustration 58 shows such an apparatus, patented by C. Gr. Miller, of the Meaker Company of Chicago. This machine carries the goods by means of a chain conveyer through the electrolyte. The chain conveyer is adjusted in a jDerpendicular position and as soon as one article is ready and thoroughly plated another one is suspended on the same hook, making the process a continuous one. A indicates a tank conveniently constructed of Avood, though, obviously, it may be lined with any suitable material. As shown, at the rear or discharge end of said tank is provided an upright frame composed of posts a — a', two on each side, and which may be transversely connected in any suitable manner to afford rigidity and strength, and journaled upon the uprights a', which are at the rear end of the tank, is a shaft B, provided on its outer end with a worm gear 6, adapted to be driven by means of a worm 154 GALVANIZING AND TINNING b^, on a sliaft h', provided witli tight and loose-belt pulleys ¥ — &■*, as is usual. Journaled upon a standard C, at the forward end of the tank, is a transverse shaft C^ provided centrally with a sprocket wheel c thereon. Journaled on adjustable pulley blocks D, of any suitable kind, secured on the rear end of the tank on each, side thereof is a shaft D\ corresponding with the shaft C^, and parallel thereto Fig. 58. Vertical Section of the Miller Chain Conveyer Machine and provided with a sprocket d centrally thereon and in alignment with the sprocket wheel c on the shaft C^ A corresponding sprocket wheel ¥' is provided on the shaft B, above the shaft D\ and trained about said sprocket wheels is a sprocket or link-belt chain E, of any suitable kind or construction, adapted to be run on said s|)rocket wheels. As shown, the diameter of the sprocket wheels c — d is such that the lower run of the sprocket chain E is parallel with the top of the tank, and, of course, with the electrolyte in the tank, and secured transversely on said chain at short intervals apart are metal- lic bars e, which are engaged to the appropriate links of said chain near the middle of each bar. Engaged near each end of each of ELECTRO-GALVANIZING PLANT AND EQUIPMENT 155 said bars is a downwardly directed hooked wire or rod e', the lower end of which is directed laterally and outwardly toward the wall of the tank, and serve as hooks to support the articles to be plated or coated. Extending longitudinally the tank near each of the side walls and at the middle of the same are conductors / — /^ — -p^ which, as shown, are round metallic rods connected with one of the leads /^, from the generator F, on which are susijended the anodes F^, which hang downwardly in the electrolyte in parallel relation with each other and, of course, may be of any desired number, and afford a sufficient surface for the purpose required. Said con- ductors are connected by a cable /* with each other at one end of the tank. As shown, the central, parallel bus bars /^ are pro- vided on each side the central conductor F'-, and, as shown, are flat bars of' metal, which are supported upon the top of the tank and projecting above the same, and on which the flat bars e on the chain slide, and which thus serve to support the lower run of the chain and its load during the platnig operation. Said bus bars are connected with the other lead ./*' of the generator. As shown, the shaft D^, with its sprocket wheel d thereon, is arranged forwardly of the upper shaft B, and its sprocket wheel, thus inclining the upward run of the chain outwardly over the discharge end of the tank and, as shown, an inclined chute Ijoard Gr, is supiDorted upon suital)le brackets on the discharge end of the tank, and its upper end projects to near the extended ends of the hooks e^, as they rise from the electrolyte, and is adapted to receive the articles discharged from said hooks to direct the same from the tank. Means are provided for jarring the chain to shake the articles more or less during the plating or coating operation, and also to remove the coated articles from the hooks. For this purpose, as shown, a short shaft is journaled in suitable Ijearings on the inner face of each of the uprights a^ and the ends li — h^ of which are directed opj^ositely to i^rovide arms. The arm It, is curved to provide a cam, as shown more clearly in Fig. 58, and is adapted to be engaged by the end of each bar e, to adjust the other arm h^, to engage within the liook e^. Said arm h'^ is j^rovided with a hooked end /;-, and a spring li^ is secured at its ends to the arm and bar and acts to throw the hook h- outwardly when the bar e passes the cam /(, thcreliy removing the articles from the hooks e^. 156 GALVANIZING AND TINNING Operation of the Miller Machine The operation is as follows : An operator stands at the receiving end Y of the tank and, as the chain travels downwardly toward the tank the current passes therethrough into the bus bars, thus hooks. This is, of course, easily accomplished if the articles are apertured. If not, wire loops may be provided whereby the article may be engaged upon the hook. The chain is thus loaded progres- sively, and as the articles are submerged in the electrolyte within the tank the current passes there through into the bus bars, thus completing the circuit. Obviously, a very large surface of the metal to l^e plated is exposed l^etween the anodes supported ver- tically in the tank, and as the articles to be plated travel longitu- dinally in the tank between the same the thickness of the coating may be regulated l)y the rate of travel and, of course, the current. Having passed through the tank, said articles are raised from the electrolyte upon the upward run of the chain and as the same approach the hooked jar arms h — //^ these, as the successive bars e engage the arm It, the arms li^ swing inwardly, after which the springs retract the arms h'^ for, their hooked ends to remove the articles from the carrying hooks, adapting the articles to fall upon the chute G. Owing to the quick retraction caused by the spring, the arm h of the jar mechanism is throAvn inwardly to engage the succeeding bar e, wliich jars the supporting mechanism and par- ticularly the lower run of the chain gently, thus tending to con- stantly shift the contact surface on the hook of the article being coated. In this manner, uniformity of the coating is assured. In use, the outer end of the supporting hook becomes slightly enlarged by the deposition thereon of the plating metal. This as- sists in holding the articles (while coating) on said hooks, and, in consequence, there is little or no tendency of the same to fall there- from to the 1)ottom of the tank. Of course, other means may l)e provided for releasing the plated or coated articles from the supporting hooks, the jar arms, how- ever, acting simultaneously and oppositely, are very effective and are automatic in operation. Obviously, the lower run of the chain is at all times supported in horizontal position whatsoever the load thereon, by means of the bus Imrs. If the chain should at any time become slack, the ad- justment may be quickly made by means of the adjustable bearings D for the shaft D\ ELECTRO-GALVANIZING PLANT AND EQUIPMENT ir, 158 GALVANIZING AND TINNING Daniels Screw Conveyer Machine Figs. 59, 60 and 61 show a similar construction by which the goods should be first suspended on wires, hooks or racks and then Fig. 60. Top Plan View of Daniels Screw Conveyer Machine Fig. 61. Side Elevation of Daniels Screw Conveyer Machine hung on a screw conveyer, fixed in a horizontal position within the tank above the solution. ' This device has been patented by the Hanson & Van Winkle Company of Newark, N. J. ELECTRO-GALVANIZING PLANT AND EQUIPMENT 159 In apparatus lierein shown 10 indicates the vat for containing tlie hath, and 11 tlie lonuitiidinal anode rods inter-connected by transvei'se conductors 12 and 13. In the present embodiment of the invention 3 anode rods 11, comprising two outer and one inter- mediate, are shown. The anodes 14 are hung on the anode rods 11, thereby sul)dividing the entire bath into two longitudinally ex- tending lanes or spaces, through wliich successively it is de- signed to convey the articles to be phited. The numljer of lanes or spaces thus formed may of course be varied to suit require- ments, by corresponding variations in the construction of the ai)paratus, but the construction and arrangement herein shown will be sufficient to illustrate the invention. For conveying the articles through the spaces to either side of the inner line of anode rods conveyer screws 15 are provided. These extend longitudinally of the vat and are disposed above the level of the bath, one on either side of the intermediate line of anode plates. The conveyer screws 15 may be constructed in any desired manner, but as shown lierein they are constructed of rods or shafts, on which are disposed conveyer coils. The con- veyer screws are journaled at one end in suitable bearings 16, and at the other end on a stationary curved rod IT, as will be clearly shown. Intermediate of their two ends the rods are supported at suitable intervals by the intermediate supports or bearings 18, which as illustrated in Figs. 60 and 61 are bifurcated to permit the passage of the cathode hangers 19, as clearly shown. To drive the two^conveyer screws in opposite directions power is applied to belt pulley 20 fixed on shaft 21 suitably journaled in bearings 22 and carrying worm sections 23 and 21 of opposite pitch, which mesh with worm gears 25 and 26, respectively, of the two conveyer screws. A Avorm section 27 is also provided on shaft 21 which op)erates a worm gear 28 fixed on longitudinal shaft 29 journaled in bearing 30. The other end of shaft 29 carries a bevel gear 31, which meshes with the bevel bear 32 fixed on a vertical shaft 33, which is journaled in a bearing 31 suitably mounted on the framework of the ajjparatus. Vertical shaft 33 has secured to it, as illustrated more clearly in Fig. 61, a transfer disk or AAdieel 35, which runs on roller bearings 3!) mounted in a supporting arm 37 of the framework. The sup- porting arm 37 provides a Ijearing or guide for the lower end of 160 GALVANIZING AND TINNING vertical shaft 33 as shown. The transfer disk or wheel 35 is herein shown as ha^ang its periphery formed with an annular con- cave surface, conforming in radius with the stationary curved rod 17 above referred to, v;hereby the curved rod receives support. The curved rod serves as a transfer rod or support while, the cathode hangers are being transferred from one conveyer screw to another, as Avill be shown. The two ends of the transfer rod thus constituted are reduced and provided with annular peripheral grooves 38, forming ball races for ball bearings 39, and a pin race for iJie key pin 40. The adjacent ends of the conveyer screws 15 are bored to fit over the reduced ends of the transfer rod 17, as clearly shown in Fig. 61, so as to bear on the ball bearings 39. The key pin 40 al)ove referred to is inserted through a perforation near the end of the conveyer screw, wherel)y the transfer rod is retained in position upon the transfer disk 35. Transfer disk 35 carries a series of radial fingers 41 which project outwardly from its periphery in a plane beneath the plane of the coils of the conveyer screws, which coils terminate within the vertical circumferential plane of fingers 41, but not in the path of the fingers. Operation of Daniel's Screw Conveyer Machine The operation of the apparatus will now be apparent. The cathode hangers bearing the articles to be plated are hung upon the conveyer screws 15 at suitable intervals while the screws are rotating, and the hanger thus progresses on one of the conveyer screws toward the transfer rod 17, passes freely through the open- ing at the bottom of the intermediate supporting bearings 18, and when it arrives at the termination of the coil on the con- veyer screw, it is engaged by one of the transfer fingers 41 of the rotary transfer disk 35. The hanger is thereby carried from the end of one conveyer screw onto the transfer rod 17 and finally delivered to the end of the other conveyer screw at a point where it will be engaged by the coil of the conveyer screw and started on its return through the bath. The negative terminal of the current is connected with the conveyer screws 15, so that the articles carried by the cathode hangers 19 become the cathode in the bath and are plated. The articles to be plated may be of such weight as to tend to distort the conveyer screws, but by the ELECTRO-GALVANIZING PLANT AND EQUIPMENT 101 provision of the intermediate supporting Ijeariiigs such tendency is rendered inelfoctive. In the ap[)aratus shown and descril:»ed the articles to be plated are introduced and removed from the same end of the vat and in order to maintain the cathode surface area substantially uni- form in the electroplating operation, it is advisable to avoid variations in the number of the articles being plated. By the arrangement shown the maintenanc^e of uniformity in this respect is facilitated as the operator standing at one end of the vat in- troduces a new article for each plated article withdrawn. The rheostat can, therefore, be adjusted in starting up operations to suit the particular requirements, but after the number of articles in the vat has reached full capacity no further regulation of the rheostat is necessary. The plating thus conducted is of highly uniform character and is independent of the Judgment of the operator, as the conditions determining the character of the plat- ing are mechanically controlled. The Fleischer Cable or Chain Conveyer Machine Figs. 62 to 65 show a cable or chain conveyer traveling over numerous rollers and so placed that goods suspended on knobs fastened to the cable will travel in a continuous motion from one tanlv into the other. First, cleaning; second, rinsing; third, plat- ing, and, fourth, drying. This apparatus is patented by Herman & Charles Fleischer and assigned to the Stanley Works of New Britain, Conn. 1 is a water-tight tank of usual form, open at the top. The tank 1 receives and holds the plating solution. 2, 2 are anodes. 3, 3 are articles to be plated, which will hereinafter l)e termed the "cathodes." In the preferred form of our invention both the anodes and cathodes are mechanically conveyed into, through and out of said plating solution; but it is not absolutely essential to certain fundamental features of the invention that the cathodes themselves be moved through said solution. 4, 4 are bars, which we term "anodcrcarriers," the same being formed of suitable conducting material. Both ends of each of the anode-carriers 4 are connected to drive chains or belts 5, 5, ar- ranged to traverse on opposite sides of the tank, each chain 5 traversing over a series of independent guide-sprockets arranged on opposite sides of the machine. 162 GALVANIZING AND TINNING 6, 6 are cathode-carriers, from which are suspended the cathodes 3, 3. Both ends of each cathode-carrier are attached to chains 7, 7, which are arranged to traverse the opposite sides of the tank and are guided by suitable independent sprockets, also located on oj)po- site sides of the machine. -^ TOf)kiiiifiuuiiumi J 'd i A ^ 7" ■ ' in Fig. 62. Side Elevation of Fleischer Machine Fig. 63, View of Fleischer's Ma- chine Showing Carrier and Conveyeb Chain Fig. 64. Cross Sec- tion OF Tank of Fleischer Chain Conveyer Machine Fig. 65. Enlarged Detail View of Tank Showing Anodes in Position The chains 5 and 7 are driven at a corresponding rate of speed. Any suitable driving means may be provided. For example, the guide-sprockets 8, 8 may be mounted upon a shaft 8% so that when rotary motion is imparted to one of said sj)rockets it will be trans- mitted through one shaft to the other sprocket. One of the sprockets 9, traversed by chain 7, may act as the drive-sprocket for one of the chains 7. The corresponding guide-sprocket on the other side of the machine (not shown) may be mounted on a shaft with the guide-sprocket 9, so that when one turns the other will turn. The driving-sprockets 8, 9 may be connected by means of a chain 8*", so that power applied to either of the sprockets 8 or 9 will be transmitted to the other. In the preferred construction the ELECTRO-GALVANIZING PLANT AND EQUIPMENT 103 sprockets 8, 9 are rotated intermittently by means of a ratchet 10, pawl 11 and rocking arm 13. The anode-carriers 4 are spaced apart at equal intervals, and the eatliode-carriers are s])aced apart at like intervals. When the anodes and the cathodes are being conveyed through the solution in the tank 1 it is preferred that said anodes and cathodes be spaced apart alternately and at equal intervals. 13, 13 are tracks along the upper opposite edges of the tank 1 and arranged to support the anode-carriers 4 while the anodes are immersed in the solution in tank 1. 14, 14 are tracks also ar- ranged along the edges of the tank 1, their function being to sup- port the cathode-carriers 6 when the cathodes are immersed in the solution. To prevent interference, tlie tracks 14, 14 are prefer- ably spaced apart a less width and are at a loAver elevation than the tracks 13. The length of the cathode-carriers G is corre- spondingly less than the length of the anode-carriers 4. One or both of the tracks 13 constitutes electrical contact for the carrier 4. The same is true of one or both of the tracks 14, the same being an electrical contact for the cathode-carrier 6. The signs plus (-|-) and minus ( — ) represent the respective electrical connections. The track 13, being the anode connection, is positive, while the track 14, being the cathode connection, is negative. The chains 5 and 7 are preferably insulated from the carriers 4 and 6. 15 is a bushing of insulating material provided at each end of the carriers. Pins 5", carried by the chain 5, project into these insulating-bushings 15. The guide-sprockets over which the anode-chains 5 run are so arranged that the anodes will be lowered into the plating solution at one end of the tank, whereupon the anode-carrier will make elec- trical connection with the track 13. The anodes are then con- veyed through the solution and removed from the other end of the tank. The guide-sprockets over which the cathode-chains 7 run are so arranged that the cathodes will be lowered into the solution alternately with the anodes, whereupon the cathode-carriers will make an electrical connection with the track 14. The cathodes are then conveyed through the plating solution and removed from the other end of the tank. While in the solution the cathodes and anodes are preferably spaced apart at equal intervals. While in the jDlating solution the surfaces of the anodes will l^ecome fouled 164 GALVANIZING AND TINNING by a scum-like deposit, which if allowed to accumulate will impair the free plating action and dissolution of the metal. By making the anodes automatically removable they may be readily cleaned — for example, by causing them to )}e immersed in an anode-cleansing bath, which may be provided in tank 15. The guide-sprockets 16, 16, 17 are so arranged that each anode will be lifted up over the edges of the tank 15 and immersed for a short time in the cleansing solution therein. There are many advantages in keep- ing the anodes clean, among which are rapidity of dissolution of the metal, relatively rapid speed and uniformity of deposit, saving in electric current and chemicals. The balance of "the guide- sprockets for the anode-chain not already numbered are indicated at 18, 18. Obviously the particular arrangement of the guide- sprockets and the method of supporting them is entirely immaterial. The movement of the chains 5, 7 is so comparatively slow that an operator standing at either end of the tank may remove the plated articles from the cathode-carriers 6 and substitute unplated articles which in due course will be conveyed through the plating solution, as previously described. By causing the articles to be passed through the solution alter- nately with the anodes, each line of articles suspended from a cathode-carrier is moving into a sphere of solution which has been enriched by the dissolution of the anode immediately in front of it, the said anode practically recharging the solution which has been partially impoverished by the cathode immediately preceding said anode. While to those features of the invention already descril)ed it is not essential that the apparatus shall have the capacity of pre- paring the articles to receive the plating deposit, a further de- velopment of the invention contemplates the continuation of the cathode-chains 7, 7 so that they will cause the cathode-carriers 6, 6 and articles suspended therefrom to traverse a washing-tank 19, in which tank various baths may be provided in separate compart- ments, into which the articles to be plated may l)e successively immersed in order to prepare the surfaces thereof to receive the plating solution. We have found that great economies are at- tained by this arrangement. Kot only is the danger of possible contamination of the surface of the article rendered practically impossible, because the articles are not manually handled after being cleaned and until they are plated, but a decided saving in ELECTRO dALVAKTTZTNG PLANT AND EQUIPMENT 16r, chemicals results. Tlio cliains 7 traverse in the direction of tiie arrows, so that an oj)erator standing at the lel't-luind end of tlie tank may attach to the carriers mounted on the chain 7 the articles to be plated. These articles are conveyed into the several prepara- tory baths successively, and the movement is so comparatively slow that ample opportunity is given for the chemicals to drip from the articles into the baths from which they are removed before being immersed in another bath which may be, for example, of a different chemical nature. This drip occurs directly over the bath from which the article is removed, and hence the particular chemicals therein are saved. The danger of injury to operatives by contact with the chemicals, incidental to the cleansing of the articles, is entirely eliminated. 20 is a final washing-tank at the opposite end of the plating- tank into which the plated articles are immersed after being re- moved from the plating solution. 21, 21 represent the sprockets for the chain 7 whereby said chain is moved in such a course that the cathode-carriers supported by said chain will be conveyed in such a direction as to move the articles to be plated over each of the partitions in the tanks 19 and 20, so that the said articles will be washed or immersed in the aforesaid baths. The particular arrangement of these sprockets 21 is, of course, immaterial so long as they permit of the use of endless bands or belts 7. These foregoing illustrations show the different ways and means which can be adopted to improve the plating of larger articles in open-tank work. The Daniels Plating Barrel Pigs. 66 to 69 show a plating barrel suspended on a shaft with a special connection carrier. The barrel is of the perforated type and is immersed entirely in the solution. Curved anodes have to be used to secure a better current conductively all around the barrel. The center shaft within the barrel is provided with chains to connect the work with the negative current of the dynamo. By loading and unloading the goods to be plated in this barrel, the barrel must be lifted from the solution and connections by means of a lifting device. This machine is patented by the Hanson & Van Winkle Company of Newark, N. J, Fig, 68 is a longitudinal vertical section of one form of electro- 166 . GALVANIZING AND TINNING plating apparatus, and one form of revoluble container, clrnm or cylinder, mounted upon a shaft or spindle, said view illustrating in elevation, a number of flexible contacts or cathode-elements em- ))odjing the principles of this invention. 1 is the tank, comprising base 2, sides 3 and ends 4. 5 is one of tlie two usual and similar anode bars from wliicli the anodes 5' are suspended on cither side of the drum or contaiiu'r 8. These bars 5 are secured to tlic tank bv fasteners, as C). and are con- FiG. 66. Hand Wheel Lifting Device fok Daniels Barkel nected by means of the connector 7 with the wire 7', which connects with the positive terminal of an electric generator. The mass of articles 8' is placed within drum 8, which is rigidly mounted on shaft 9, rotatable in bearings 11 of removable suspen- sion frame 10 having members 12 removably engaging Avith and supported by rods 13 secured to and extending across tank 1, and through connector 13' and wire 13" connected with the negative terminal of an electric generator. Shaft 9 is driven from a shaft member 14 by any convenient power, a separate connection between said shaft and member being made, in this instance. ELKCTRO-GALVANrZTNG TLANT AND EQUIPMENT 167 The nov(-'l cathotlc members, or elements, are Icxjsely and movalily coml)iiu'(l with and su})ported by shaft i), from wliich tliey (k'[)('iid. Tlu'y coiuitiisi', in tliis instance, a weight or sinker-])ortion 11), a Fig. 07. Lkveu Lifting Jjevick h\i. Da.mels Barrel J^7^ '^ Fig. 68. Vertical Section of Daniels Plating Barrel coupling portion comprising ring, or eye, 16 loosely encircling shaft 9, and an intermediate flexible portion, in this instance a section of chain i8, the upper link of which is connected with an eye or 168 GALVANIZING AND TINNING hook-shaped part 17 of a stem or rod 15, therehy loosely con- necting 15 with 19 as shown. During the rotation of the drum the articles to be electroplated are tumbled about within said drum, constantly exposing new sur- faces, and making efficient contact Avith the weight or sinker-portion 19 of the cathode-meml)er. Fig. 69. Transverse SECTIO^- of Daniels Plating Barrel The Potthoff Automatic Galvanizing Barrel Figs. 70 and 71 show an apparatus patented by Louis Potthoff, of the United States Electro Galvanizing Co. of Brooklyn, N. Y. Fig. 70 shows that the plating barrel is resting in bearings and center shaft on top of a plating tank, immersing the plat- ing barrel only about one-third into the solution. It also is pro- vided with inside anodes supported through a center shaft and special anodes supports to prevent the articles from coming in con- tact with the anodes. After the articles have been plated the spring- door is set and the goods will be discharged little l)y little into Hie washing drum and carried from here in a screw conveyer into the drying drum and then finally into a tray. The tumbling barrel 1 is mounted on a shaft supported on the solution tank 2 by bearings 3. Tumbling barrel 1 is rotated by means of sprocket 4 and chain 5. On the opposite side of barrel 1 is a sprocket 6 with driving chain 7, which actuates the sprocket 8 on one end of shaft 9, shaft 9 being journaled in bearing 10, sup- ported on tank 2. Shaft 9 is provided with bevel bear 11, meshing KUXTIIOCAIA'AXIZIXO PLANT AND EQUIPMENT IC!) witli ,u"(':ir I'i |)i)sili()ii('(l at (nic end of sliai't 13. Slial't l^) is ])!■()- vi(k'etween the rollers F F. The speed of the endless traveling skeleton fiame carrying the articles is regulated to cause a compl(,'te plating of the articles on the entire outer surface during the jjassage of the article through the electrolyte in the tank A. If it is desired to plate small articles, then the same are pla/ed in a metallic perforate tray or liasket IT, set on the contact-points D'^' of the upper run of the skeleton frame or fastened thereto, so that the articles are passed through the electrolyte B and between the anode-plates C and C", the same as tlie articles ab>ove de- scribed, and directly fastened to the upper run of the skeleton frame. It is understood that in practice the large articles or the basket containing the small articles are placed in position on the upper run of the skeleton frame at the roller E and taken off the skeleton frame at the roller E^ By moving the articles to l)e plated through the electrolyte the hydrogen is continually removed from the surface of the articles to insure the formation of a l)right plating deposit on the articles. It will also l)e seen that l)y the arrangement described the electro- lyte is kept in motion by the moving cathode to allow of using a very high current, thus finishing the plating in a comparatively short time. Electrical Equipment A dynamo driven ])y a revolving belt or motor, directly con- nected, will supply the necessary amperes and volts required to deposit the zinc metal from the electrolyte onto the cathode (goods to be plated) and dissolve at the same time an equivalent amount ELECTRO-GALVANIZINU PLANT AND ECiUIPMENT 207 of zinc from the zijie anodes. A voltmeter and an ammeter, as well as a rheostat, are required to control and regulate the volts and amperes for the different loads and classes of work. The generator supplying the current is usually placed within 40 or 50 ft. of the galvanizing hath, although this distance may be increased provided the conductors are also increased in size. A safe ruling for every 30 ft. added double the size of the conductor. First, 80 1"; second, 30 2"; third, 30 4"; fourth, 30 8". Great ad\ance has been made in the United States in the manufacture of dynamos for deposition and it is now possible to procure low- voltage generators up to 10,000 amperes capacity. Such generators can handle 1.000 sq. ft. of work in a galvanizing bath at one time or approximately 16,000 sq. ft. of work in a day of 10 hours. This is l)ased on using a current of 10 amperes per sq. ft. and allowing a 30-minute (le})osit and the necessary time for filling empty tanks. In no other form of electro-deposition has the demand lieen greater for generators of low tensions and high ampere capacity than in the electro-ga 1 \ a 1 1 i z i ug ind ustr3^ Opinions differ as to amount of voltage required. It is agreed that low voltage gives softer and tougher deposit, Avhile when very heavy deposits are required ^w voltage is alisolutcly necessary. Some galvanizers use 2 Aolts for light Avork, while others use 6 volts on the same class of work. The latter saves time, but does ]iot give as smooth a coating. On big Avork it is necessary to have higher voltage, becaiise of size of tank and distance from anode, Avhich increa'ses resistance. Copper conductors should be made of solid, flat, round or tulni- lar copper of size sufficient to carry required amperage. 1 sq. in. of copper will carry 1,000 amperes, and 1 sq. ft. of material sur- face exposed in galvanizing solution Avill require from 5 to 20 amperes ; depending on voltage used and conductivity of solution and anodes. Anodes The anode or positive element from which the metal is taken is an im])ortant item in the electro-galvanizing process, its purity determining to a great measure the quality of the work and the proper maintenance of the solution. A cast anode is to be pre- ferred, in shape elliptical, round or flat. In a cast anode the structure is more open and crystalline than in the plate form, and 208 GALVANIZING AND TINNING this metal is readily disintegrated under the action of the current. The anode surface exjoosed should Ijc one-third greater than the cathode surface. Cost of Installation The much slower rate at which the zinc is deposited electrically makes the size of the plant larger than for the dipping process, and the first cost is, therefore, greater. It should be noted, how- ever, that the cost of one cubic foot of tlie electrolyte bath is but a fraction of that of the galvanizing bath. The solution tanks are usually made of cypress, 3" or 4" stock Avith a lining of a mixture of asphalt and pitch, to which, before it is set, a coating of hot white l^each sand is applied, making a hard, serviceable lining. Tanks for pickling are usually made of wood witli a lead lining and tiie tanks for caustics or electro-clean- ing are of iron or steel, arranged with steam coils. CHAPTER XXII Preparing Work for Electro-Galvanizing MATEKIAL to be electro-galvanized is cleaned, preparatory to immersion in the electrolyte, in much the same manner as it is handled for dipping in the hot ijroccss. A com- ])i'chensive treatment of these methods is given in Chapters V and VI of this book. While it has frequently been stated that special attention is required and considerably more caution is necessary in cleaning materials to be cold galvanized, this idea undoubtedly has orig- inated from the fact that material which has not l)een thoroughly cleaned can be hot galvanized; while the electrolyte process will not act on a surface that has not been entirely freed from foreign matter, such as oil, scale, sand, etc. AVhile it is true that the hot process of galvanizing will largely coat or bridge over such unclean surfaces, material which is treated without being properly cleaned will not resist corrosion so effectively as carefully pre- pared material, because the impurities set up a corrosive action between the basic metal and the zinc coating. In some cases it has been found that the zinc coating would not adhere to the basic metal and the least shock would loosen it. Knowledge of the effect of acids and pickles on various forms of iron and steel is necessary in arranging the cleaning and pick- ling baths. Cold-rolled and malleable iron are readily treated, requiring but mild pickling. Hot-rolled steel is usually covered with a hard scale which must be jDickled or otherwise treated. Cast iron is perhaps the most difficult to treat successfully in the electro-galvanizing bath. The foundry turns out so many kinds of castings ; the quality depending upon the mixture ; the char- acter of the facing used; the temperature at which tlie metal is poured : the burning of the sand into the casting ; the porosity. All of these are factors which make it practically impossible to treat all iron castings similarly. In some instances dry tumblers are used with jacks, the dust exhausted by a blower keeping the castings clean; water tumblers are used with other kinds of work. If the castings have received the proper attention in the foundry, 209 210 GALVANIZING AND TINNING tumbling will prepare the work so that only a mild pickle need be used. Removing Sand from Castings It must be remembered that while hydrofluoric acid will remove sand and scale, great care is required in its use and the strength of the acid should be modified. The solution given below will cause the least danger to the work if not left in the pickle too long. Hydrofluoric acid, 30 per cent 2 parts Sulphuric acid, 66 per cent 1 part Water 8 to 10 parts A hot pickle of 140 to 160 deg. will work much faster than a cold one. It is always best to use the pickle as weak as will give the desired results in a limited time. A pickle that will not properly treat the castings in two or three hours is a dan- gerous one to use. During the process of pickling, quantities of magnetic oxide and scale become detached and, if allowed to remain in the pickle, to l)e further acted upon by the pickle, will form a serious source of loss. A form of electromagnet has been devised to remove this oxide from the bath. Removing Oil or Grease If the material to be electro-galvanized is of an oily nature, that is, if oil or grease has been used in the process of manu- facture, the first operation consists in removing this foreign mat- ter by immersion before pickling in a bath, preferably hot, of caustic soda or a like solution that will have for its effect the dissolving of the oil or grease. The strength of the solution and the time required to remove the oil or grease depends some- what on the condition of the material. If a hot, caustic-soda .solu- tion is used, i to i lb. per gallon will be found to answer gen- eral requirements. Material should be allowed to remain in the bath for a period of 5 to 20 minutes. It should then be removed and rinsed in cold water before being placed in the pickling solu- tion, as the caustic soda has a tendency to neutralize the acid. Removing Mill Scale The removal of mill scale from iron or steel is generally accom- plished by pickling the material in a bath of sulphuric acid, muri- t»REPARING WORK FOR ELECTRO-GALVANTZING 211 atic acid (hydrochloric acid) or one of the numerous composi- tions for the purpose on the market. The strength of the solu- tion used, it will he understood, depends on the thickness of the scale to he removed and the time in which such pickling is to he done. One method recommended is to place the iron in a solu- tion of one part hydrochloric or sulphuric acid to ten parts of water for a period varying from ^ hour to 5 hours, this depending upon tlie thickness of the scale. If a sulphuric-acid Imth is used, a -i-per-cent.-by-weight solution of commercial acid will be found to answer general requirements. It should be used hot, although a cold solution will answer equally well if the time for pickling is sufficient. On some classes of work, like chain grips for tires, it is neces- sary to remove scale, etc., by first hanging in hot caustic soda to remove oil and, after rinsing, to pass quickly through a dip of -iO deg. nitric acid, rinse again and dip work in a 10-per-cent. muriatic-acid solution. After being rinsed again the work is ready for the gal- vanizing bath and will readily cover in the deepest recesses. Scratch-Brushing When a heav}^ pickle is used, or the work is left too long in the acid, the surface of the work shows a residue which must be removed before the work is placed in the electro-galvanizing bath. This means hand work or scrubbing, which adds largely to the cost of preparing the work. Heavy pieces of material or of a large surface, such as plates, should also be scratch-brushed after pickling, in order to remove the scum or residue and obtain a thoroughly clean surface. In many instances this can also be accomplished easily and satis- factorily by placing the material in an electro-cleaning solution made up for the purpose in place of scratch -brushing. This solu- tion is usually made from a mild caustic (about 5 per cent, free caustic) solution 6 deg. B. Copper Flashing The use of a copper cyanide strike as a preliminary to the deposit of zinc has been largely advocated. Some discussion has arisen as to the value of the copper as a resistant to corrosion. It has been claimed that as zinc is electropositive to both copper and iron, it affords protection to each metal. The oxidizing effect of the 212 GALVANIZING AND TINNING atmosphere will in time affect the zinc coating and change it to a zinc oxide. Whenever galvanic or electrochemical action is set up l)y the contact of iron and zinc and zinc in the presence of moisture, it is the zinc that is attacked and not the iron. It is claimed by some that there is no galvanic action per se in iron coated with zinc and during disintegration the zinc affords pro- tection to the intermediate coating of copper, which, in turn, pro- tects the basic metal. Others claim that the use of a copper flash is 1)ad practice because copper is electro negative to both iron and zinc and will, therefore, lead to more rapid destruction of both these metals when it is brought in contact with them in the pres- ence of tlie corroding medium. It further adds consideral)le to the cost. A dip copper has been used with some success previous to gal- vanizing and is made as follows: Water 1 aal. Sulphuric acid 1 oz. Sulphate of copper 1 oz. The work, after being thoroughly cleaned, is immersed for a few seconds in this dip and rinsed quickly. When the copper cyanide bath is used, the action is similar to that of an electrocleaner. Gas is released from tho surface of the work by the action of the current and this has a tendency to throw off the carbon residue which has remained on the work, and in its 23lace on the iron there is deposited a thin film of copper which the zinc readily covers. When the copper begins to show red, then you know the work is clean. Small material, such as bolts, nuts, washers, rivets, etc., is handled in practically the same manner, except that no scrubbing of the material is required after leaving the pickling bath, the same results being accomplished by tumbling it in revolving barrels. Castings, according to size, are handled in a like manner, ex- cept that cold hydrofluoric acid is used for pickling. In some instances slight heating has been found to be an advantage, and a bath of hydrofluoric acid of 2 per cent, in weight answers gen- eral requirements. Sometimes it is scarcely possible to remove the scale from steel without the work remaining so long in the tkEPARTNG WORK FOR ELECTRO (lyU.V AN IZ1N(! 2i;i jiickle tliat tlie softer or more porous parts oi' the iiiclal will he over-pick led. Tumbling and Sand Blasting The removing of oil, grease, oxide and scale from small articles in quantities is done by the means of tumbling tb( ni for sc\ci';il hours in cast-iron or heavy wooden tumbling barrels, nniniiig with a speed of approximately twenty to forty revolutions ])cr minute. The articles are charged into the drums and mixed with sawdust. The sawdust will remove and absorb the grease, and the rattling and tumbling of all the articles against each other for a continuous length of time will remove the scale and oxide and produce at the same time a smooth and bright finish to the articles. It is a general practice to fill the drum about one-third wMth small articles and one-third with sawdust, and this sawdust is discharged at the completion of the process by sim])1y loosening the cover of the drum a little and the sawdust will escape through the opening in the revolution of the drum. After the sawdust is removed entirely, a few shovels of new and clean sawdust are placed into the drum again, and the process repeated to remove the balance of the grease, if any. Castings are freed from scale and sand preferably by the use of a horizontal sand-blast tumbling barrel. It is considered good practice to wet roll stamped steel with grit or emery until clean. Wire work can usually be cleaned l:y dry rolling with sawdust to absorb the oil, then rolling with leather chips until bright and clean. The work is then strung on wires or racks and hung in lire electro-cleaner for a short time. The use of sand blast is recommended where the nature of the material and quantity make the operation practicable. Its use elim- inates the necessity of the regular pickling process, although some- times moderate subsequent treatment is necessary before the mate- rial is placed in the galvanizing solution. This process is also extensively used for cleaning conduit pipe previous to electro- galvanizing. Oils and greases should be removed previous to being sand blasted, to permit the sand or crushed steel employed to be used again. Schulte Grinding and Scouring Machine The object of the machine illustrated in detail in Fig. 98 ij to provide a new and improved machine for grinding. 214 GALVANIZING AND TINNING scouring, scratch-brushing, bufSng, and sand-buffing sheet metal, band-iron, wire, and like metal articles and arranged to simul- taneou;?ly treat both faces of the article in a comparatively short time without requiring skilled labor. Fig. !)S. Front Side Elevation of Schulte Grinding and Scouring Machine Suitable grinding material — such as water, sand, pumice-stone, and the like — is fed onto the top and Ijottom of the article to be treated immediately previous to the article passing between the rollers B and B\ and for this purpose a number of nozzles N and are employed, connected with the lower end of a tank N^, sup- ported on the top of the frame A and containing the grinding material referred to. Now as the article moves forward between the rollers B and B^ the grinding material discharged onto both faces of the article is carried along l)y the latter, and consequently the rotating and transversely shifting rollers B and B^ grind, rub, and scour both surfaces of the article. In order to keep the mate- rial in tlie tank N^ properly mixed, a stir-up and transversely ex- tending screw N- is arranged in the l3ottom of the said tank, and on the outer end of the shaft N^ of the said screw is secured a pulley N^, connected by a belt N'^' with a pulley N'^, secured to the shaft D^ for tlie upper feed roller D, so that when the latter is rotated the screw N- in the tank N^ is rotated to agitate and keep the ingredients of the grinding material properly mixed. It is understood that instead of the screw N^ other suitable means may be employed. Water is discharged on the upper and lower faces of the article to be treated previous to the article passing between the second pair of rollers C and C^, and for this purpose nozzles 0- and 0^ PRl'^PARTNG WORK FOR ELECTROaALVANIZING 215 a-.' pro-ided, comiocii'd with a wai('v-sii])|)ly pipe ()■*, Icadini^; from a suitable source of water sup^Dly. Now l)y the article passing l)etween the rollers C and C^ while the latter are rotated and shifted bodily and water is discharged onto the plate at both faces, it is evident that the article receives a final scruljbing, so that the article finally passes in a ground and scoured condition to the delivery-rollers E and E^ and the transporting-rollers F^ for carry- ing the finished article off the machine. The grinding material used, as well as the water, drips and flows into a trough P, arranged in the lower portion of the main frame A below the rollers B^ and C^, and this trough P is con- nected with the suction end of a pump Q, having its discharge- pipe Q^ leading into the overhead tank N% so that the grinding material and water is returned to the said tank N^ to be again discharged to the nozzles N onto both faces of the next article to be treated, thus allowing reuse of the grinding material. The shaft Q- of the pump Q is provided with a pulley Q^, connected by a belt Q:* with a pulley Q;"' on the shaft B' of the roller B^ so that when the latter is rotated the rotary pump Q is set in motion to ^Dump the material from the trough P into the over- head tank IST^. It is understood that when the machine is in operation both faces of the article are ground and scoured by the use of the grinding material discharged onto both faces of the article previous to its passage bet\veen the rollers B and B'. The pairs of rollers B B' and C C are made of wood or other suitable material or covered with a fa1)ric, according to the nature of the material under treatment and according to the particular finish to be given to the article — that is, whether the same is to receive a scratch-brushing, Imffing, sand-buffing, or the like. By passing the article in an inclined position through the pairs of rollers the grinding material and water readily flow back on the article and finally into the trough. Electro Cleaning Cleaning work by a low current of electricit}^ is largely prac- ticed in the electro-plating industry. Usually an alkaline solu- tion is used, costing but a few cents per gallon. Steel or iron con- tainers are used for the bath, which is heated to the boiling point by means of steam coils. The tank itself is made the positive by 216 GALVANIZING AND TINNII^G being connected with the positive pole of the generator; the work in the bath is attached to the negative pole of the dynamo and an e. m. f. of 6-8 volts is used, the work being left under the influence of the current for several minutes. Gas is thrown off freely from tlie work and the surface is cleaned by the action of this gas, particles of oxide and grease heing removed. CHAPTER XXII r Electro -Galvanizing Solutions and Their Application S(,)ME of the earliest experiments in electro galvanizing were made by the French scientists, and present users are indebted to this source, as well as to German and English authorities, for some practical information regarding the action of the various salts of zinc. A number of Ijaths have been patented both in this country and al^roacl, but the most effective and simplest bath is that made from the sulphate of zinc, in combination with alu- minum, zinc chloride or some similar salt, and it has been deter- mined that a bath showing an acid reaction is to be preferred. It is unnecessary that .'solutions be used of a composition of poisonous ingredients or those throwing off fumes while in opera- tion, nor is it necessary to operate them at more than the usual room temperature. Their composition should be such as to give the highest electrical conductivity; for the thickness of the zinc deposit and the length of time required for the coating depends on the conductivity to a large extent. Their nature should be such as to decompose and deposit the zinc with a minimum libera- tion of hydrogen, or the deposit is likely to be found, on exam- ination, to be iDorous and of a granular and spongy nature. Ob- servance of these' conditions will result in deposits uniformly smooth, homogeneous, flexible with perfect adhesion, and in an absolute union between the basic metal and coating. The upkeep or maintenance of the solution is equally impor- tant, and satisfactory results cannot be oljtained continuously un- less the solutions are at all times working at their highest efficiency. The cause of unsatisfactory work with the electro-galvanizing process is frequently attributed to improper cleaning of the mate- rial, but the fault sometimes lies with the electro-galvanizing solu- tion or electrolyte. While experience in pickling or preparation of surfaces previous to galvanizing affords many little short-cuts which will result in the most satisfactory and quickest results, it does not require the services of an expert or a man of more than average intelligence to master it in a comparatively short time. Atten- tion to details and close observance of results under varying con- 217 218 GALVANIZING AND TINNING ditions will enable any one to master this part of the electro- galvanizing process. The electrolyte or zinc solution can be made up from sulphate of zinc (white vitriol) or from chloride of zinc, or from a com- bination of the two. An addition of conducting salts, such as sulphate of sodium, sulphate of aluminum, chloride of ammonia, etc., can be used to increase the conductivity of zinc solutions. There are also a number of organic and inorganic chemicals rec- ommended and patented for the purpose of producing a more dense and brighter deposit. The majority of these chemicals (of which we will speak more fully later on) act as a colloid through tlje electric current. The following solution has been worked with success in an open still tank. Formula 1 Zinc sulphate 200 lbs. Sulphate of sodium (crystals) 20 lbs. Sulphate of aluminum 10 lbs. Boric acid 3 lbs. Water to make 100 gallons. An addition of a few pounds of zinc chloride, or instead a pint of hydrochloric acid, will improve the solution to some extent; also an addition of grape sugar will improve a sulphate of zinc solution and produce a smoother and more uniform finish, at the same time preventing the formation of spongy deposits. The above solution can be successfully used for all kinds of articles, including wire, liand iron, sheets and wire cloth, and will produce l>y three volts and about twenty amperes per square foot a white, smooth deposit in thirty minutes which will stand three one-minute copper tests, of which we will speak later on. Chloride of zinc solutions can also be used to better advantage in open tank work, as well as in mechanical plating machines. A good solution is comj)osed of the following: Formula 2 Zinc chloride 100 to 150 lbs. Chloride of ammonia 50 to 75 lbs. Grape sugar 10 lbs. Water to make 100 gallons. ELECTRO-GALVANIZING SOLUTIONS 219 111 the open bath a low e. m. f. is used, al)out 3 volts being required with a current of 13 to 15 amperes per square foot of work surface, the density of the solution Ijeiiig about 20 deg. Baume, although a higher voltage can be used if it is desired to shorten the time of deposit. For mechanical apparatus, where the revolving container is used, the solution is brought to a density of 25 to 30 deg. Baume and 8 to 10 volts are used with a corre- sponding increase in current. The following zinc solutions have also been used satisfactorily on different classes of work and under varying condition. They are given here so the user of the book may have a basis on which to work in experimenting to find the solutions best suited to his apparatus and work: Formula 3 Zinc suljihate -ii lbs. Pure crystallized sodium sulphate 8.8 ll)s. Chemically pure zinc rliloride 2.2 lljs. Crystallized boric acid 1.1 11)S. AVater 25 gals. Formula -i Zinc sulphate 50 lbs. Ammonium chloride 3.1 11)S. Aluminum sulphate G . 2 lbs. Water ._,.... 25 gals. Formula 5 Cold galvanizing solution for castings: Zinc sulphate 1^ lbs. Ammonium cliloride 3 oz. Sulphuric acid 1 oz. Water 1 gal. Formula 6 Cold .galvanizing solution for barrel plating : Zinc sulphate 2,^ lbs. Ammonium chloride 6 oz. Sulphuric acid 4 oz. Water 1 gal. 220 GALVANIZING AND TINNING Formula 7 Another for regular work: Zinc sulphate 1^. lbs. Epsom salts '. 8 oz. Boric acid -i oz. Ammonium chloride 4: oz. Water 1 gal. Formula 8 This solution will gi\e a soft deposit that will stand bending and forming: Zinc sulphate 2 ll)s. Ammonium chloride 2 oz. Sulphuric acid ^ oz. Water 1 gal. Formula 9 Sulphate of zinc 1| lbs. Epsom salts 5 oz. Sulphuric acid 1/10 oz. Water 1 gal. Formula 10 Zinc sulphate 2 lbs. Sodium sulphate 4 oz. Zinc chloride 2 oz. Boric acid 1 oz. AVater 1 gal. Dextrine 4 oz. Formula 11 Zinc sulphate 1 lb. Ammonium cliloride 4 oz. Sodium suljjhate 3 oz. Sulphuric acid 2 oz. A¥ater 1 gal. Formula 12 Zinc sulphate 2 lbs. Aluminum sulphate 2 oz. Glycerine ^ oz. Dextrine 2 oz. Water 1 gal. ELECTRO-GALVANIZING SOLUTIONS 221 Formula 13 Zinc sulphate 2 lbs. Sulphuric acid 1 oz. Gum tragacantli 1 oz. Water 1 gal. Formula l-t Sodium citrate (crystals ) 5.5 lbs. Zinc chloride 8 . 8 lbs. Ammonium chloride G . (5 11 )s. Water 25 gals. Forniula 15 Zinc chloride 2 lbs. Sal ammoniac 10 oz. Common salt 3 oz. Tartaric acid 3 oz. Water 1 gal. Formula 16 Zinc chloride 1 lb. Sodium aluminum chloride 5 oz. Common salt 4 oz. Grape sugar 5 oz. Formula 17 Zinc sulphate '. , 2 lbs. Iron sulphate 2 oz. Aluminum sulphate ^ oz. Sodium acetate -| oz. Formula 18 Zinc sulphate H lbs. Sal ammoniac 1: oz. Sulphate of soda 2 oz. Sulphuric acid 1 oz. Water 1 gal. Formula 1!) Zinc chloride 2 lbs. Sal ammoniac 10 oz. Tartaric acid 3 oz. Sodium chloride 3 oz. Water 1 gal. 222 GALVANIZING AND TINNING Formula 20 Sul2:)hate of zinc 2 lbs. Sulphate of aluminum 4 oz. Sal ammoniac 2 oz. Sodium sulphate 3 oz. Water 1 gal. Agents for Improving Solutions The following additional agents are used to improve either the sulphate or chloride solutions, and will cause them to plate brighter and prevent the formation of large crystals. A majority of these additional agents are embodied in numerous patented formulas: Gelatine, dextrine, glue, alum, powdered licorice, gum traga- canth and tannic acid. These are called "colloids," and when used as additional agents form colloidal solutions or suspensions. They cause the solutions to deposit a smaller crystal, making a close-grained, smooth, bright coating. Glucose, molasses, l^enzoic acid, alcohol, sugar and pyrogallol are strong reducing agents, and when used in from three to five per cent, additions produce a smooth deposit with great adherence. Applying the Coating After the articles have been freed of all oxides and scales, which means the completion of the pickling ]3rocess, the goods are then suspended on wires, hooks or racks and thoroughly rinsed in run- ning water and after this ojDcration without any delay are sus- pended in the zinc electrolyte from a rod lietween two zinc anodes. The anodes also being suspended on rods opposite to the work- ing rod. The working rod is connected with the negative pole of the dynamo and the two anode rods are connected to the posi- tive pole of the dynamo, marked with "-j-" sign. If the tumbling of the smaller goods has been accomplished sat- isfactorily, there is no further operation necessary and the articles can be transferred from the tumbling machinery directly into the mechanical plating device, in which they remain from thirty min- utes to one and one-half hours, according to the quantity of goods to be plated at one time, also according to the different types of machine in use, but chiefly according to thickness of coating required. There are quite a number of plating machines on the market ELECTRO-GALVANIZING SOLUTIONS 223 to-cla}^ particularly adapted for the plating of small articles in large quantities, by the means of revolving barrels, having nega- tive connections ; connecting with the goods to be plated and mix- ing same thoroughly within the barrel, and thus each and every article receives an equal, uniform plating. These mechanical platers differ from each other more or less in their construction, also in the arrangement of their anodes ; some are used outside of the barrel and some within the drum only. These have been fully described and their operation explained in Chapter XXI. Work witli deep depressions cannot be coated satisfactorily with- out using anodes shaped to fit the depressions. Increasing the voltage to malce it throw in would not make it cover, but would result in the outer points becoming granular or burnt. Spongy deposits are caused by a too neutral condition of the bath, and this can be rectified by testing the solution Math blue litmus paper. This test should show a deep red at once if the solution is in proper condition, but there should not be enough free acid to blue Congo paper. If the bath becomes neutral, a tcn-per-cent. solution of sulphuric acid and Avater should l)e added until l)lue litmus paper shows a 25ro23er reaction. Such articles as castings, fittings^ stampings, etc., that have recesses and depressions, should have some previous treatment. The method of procedure is that the fixed time of electro-gal- vanizing be cut in two. A strike or preliminary zinc coating is deposited from a specially prepared zinc solution and is of a dull gray or matt finish. It is advisable then to finish the mate- rial in the regular or finish solution, which will then readily coat over the entire surface and leave the treated material of a bright silvery appearance. Its Milue can be appreciated from the fact that it is productive of a quality of work not possible by any other means, reduces the time of coating and results in an out- put of more than double that possible with the same size equip- ment containing only the ordinary electro-galvanizing solution or electrolyte. A zinc coating of 25 to 35 minutes, depending on the nature of the material, dej)osited in this manner is ample and will be found to answer all requirements. It is possilile to make a heavier deposit by electro-galvanizing l^rocesses by leaving in the solution for a long period. Cast-iron rolls have been electro galvanized with coating heavy enough to 224 GALVANIZING AND TINNING stand turning in lathe. This required about ten hours in the regular solutions. Cost of Operation The cost of labor and power are the main items of expense in electro galvanizing. Exact figures as to the cost of power cannot be given. A larger firm producing their own steam and electric power as a l)y-product, figure the cost per kilowatt hour as less than one cent; while a small consumer supplied with electricity by a local power and light company has to j)ay from four to eleven cents per kilowatt hour, while in comjDarison the cost of fuel for a hot galvanizing process does not differ to such an extent. The labor cost in electro galvanizing and in hot galvanizing is about the same, wliile the zinc wasted in the hot process in the form of dross seems to be greater than the zinc wasted 1)y the cold process in rinsing the Avork from the solution. After a length of time, however, if the possil^lc leakage of tanks and the renewing of the solution is taken into consideration, the cost of waste in comparing the two processes v/ill average al:)Out the same. AVhile more time and chemicals have to be applied for the electric process than for a hot process, the hot" process will use a larger amount of zinc metal by one dip, and this leads to the main argu- ment as to whether cold galvanizing is cheaper and better or whether the hot galvanized articles are superior and cheaper than the others. While the unskilled workman in a hot galvanizing plant cannot prevent the giving of the iron articles to be coated a sufficiently heavy zinc coating, the skilled workman in an electro-galvanizing plant is sometimes forced, through local conditions, to give the cus- tomer an inferior galvanized article. Therefore, aside from the above facts^, it can be easily determined in any galvanizing plant using the two processes that, if an equal amount of metal is required on sheets, for example, by the liot process, as well as by the cold process, the cost of operating and materials for the cold process will exceed that of the hot process. However, small work in bulk quantities plated in up-to-date mechanical plating machines is less expensive than the hot process. Numerous arguments have arisen to set forth tliat a dense and bright coherent electro-galvanized deposit does not require so much zinc deposit as a zinc coating produced by the hot process. This problem is still open for discussion^, but practical natural tests ELECTRO-GALVANIZING SOLUTIONS 225 for a niim))er of years, under the same conditions, have proved that the amount of zinc applied to iron will guarantee the length of time tlie iron is protected from corrosion. For example, large pieces of iron sheets galvanized hy the hot process and large pieces of iron sheets galvanized by the cold process were nailed on top of a roof and additional pieces nailed against the chimney of a factory, and in each instance, where there was less zinc on the cold galvanized sheets, the galvanizing broke down before the hot galvanized sheets. This refers especially to such articles where the electro galvanizing does not enter so easily into the deeper parts of profiled articles, and consequently the dif- ference between hot and cold galvanizing will be much earlier shown. That this point has been thoroughly recognized and practiced is evidenced by the process of plating employed at the electro- galvanizing plant of the Spirella Company, Niagara Falls, N. Y., illustrations of which are given in Figs. 56 and 57. The problem of supplying corset wires which would effectively resist corrosive at- tack, due to atmospheric moisture and perspiration, was a serious one. Numerous experiments for several years resulted in the following coatings being applied. The wires are placed for 45 minutes in a copper cyanide bath, 45 minutes in an acid copper solu- tion, 20 minutes in a nickel solution and 90 minutes in a gal- vanizing solution. This is an exceptional case and is interesting as probably representing the limit of practice in plating for pro- tection, about five- pounds of metal being deposited for every one hundred pounds of corset wire. The argument about the special test is also a delicate one. The Preece test adopted by the United States Government is the most reliable and quickest of all tests, and every electro-galvanizing plant should use it, if only for the purpose of determining or controling the deposition of zinc from the different solutions every day. The saline or salt-water test, by the means of spraying contin- uously a 10-per-cent. salt solution for a period of from 14 to 20 days all over the galvanized articles, is also adopted by some con- cerns. Galvanizing which breaks down before 14 days have elapsed is rejected as inferior. Another test is to hang the galvanized articles in a pure-water bath in which a continuous stream of air is flowing. There is also the cinder test and sometimes diluted sulphuric acid is used to test galvanized articles against quick corrosion. 226 GALVANIZING AND TINNING Test for Thickness of Zinc Coating on Armored Cable Strip as Provided by Underwriters' Laboratories, in Effect September i, 19 13 The following test is^ in some degree, a measure of the thickness of the zinc coating and should be made on at least two samples (about 4 in. long) of the finished product going through at the time of each visit. Each sample shall be washed in running water and then dipped up and down in a vessel containing either carbon tetrachloride or ether and allowed to dry before being put into the copper sulphate solution. This solution is a saturated solu- tion of C. P. sulphate of copper, using distilled water. About 100 cubic centimeters of the solution shall be poured into a glass vessel about two inches in diameter. The same sample of solution shall be used for all dips of any one sample, but a new supply of solution shall be used for each new sample. Solu- tion, after use, shall be thrown away and in no case put back into the supply bottle. The portion of solution used for each test shall be brought to a temperature of approximately 65 deg. Fahrenheit before the test is made. This shall be accomplished by setting the beaker containing the solution in a larger vessel containing the warmer or colder water and stirring the solution with a glass thermometer until the proper temperature is obtained. The sample prepared, as above, shall be stood on end in the solution for one minute. The solution shall not be stirred or the sample moved during the immersion. At the end of one minute the sample is to be removed from the solution and rinsed in running water and then wiped lightly, both inside and out, with cheesecloth until dry. Care should be taken to avoid violent rubbing of the sample and the contact of the surface with the hand or anything else than the white cloth used for drying. The sample must be thoroughly dried before each dip. Each sample shall be subjected to at least three dips and the dips should generally be continued until the entire immersed sur- face of the sample is coated with a fixed copper deposit. The coating will be considered satisfactory, so far as this test is concerned, if the fixed copper deposit (i.e., that which cannot be wiped off) does not show before the second dip and also does not appear on more than 25 per cent, of the surface tested before the third dip and wiping process. CHAPTER XXIV The Art of Sherardizing SHERARDIZING, or dry galvanizing, is a process whereby articles of iron and steel are rendered rust proof by applying a coating of zinc dust. The coating produced by this process is first an alloy with the underlying metal. After this alloying- action is completed the outer layer of zinc is deposited, the zinc jsenetratiug into every crevice and cavity radically different from any other method of zinc coating. Briefly stated, this coating is not a pure layer of zinc, but a zinc-iron alloy. Dry Galvanizing in Prehistoric Times A process practically identical to this was known in prehistoric times, although used for another pur]30se. At that time it was known that if certain copper tools and vessels were placed in the ground in certain localities and kept hot for a time by building hres over the place, then, on removal, it was seen that the copper had assumed a light yellow color and had become harder and more duraljle. They practically secured dry galvanizing, although it was not known that another metal was being alloyed with the copper. Also, in Greek History, according to Aristotle, the "bleaching of copper" was done by the same method. The Sherardizing process was discovered by accident. Com- mander H. V. Simpson, of the English navy, was detailed to work out a method of case hardening armor plate for battleships that would not infringe on the Harvey patents which were being used by nearly all governments for rendering armor plate shell proof. These experiments were being tried out in the laboratory of Sherard Cowper-Cowles, of London, a noted English metallurgist. A pack- age of zinc dust had been forwarded Mr. Cowper-Cowles to de- termine whether it could be used in making an electrolyte for zinc plating. In the course of their experiments they placed a piece of steel in this zinc dust in a case hardening oven and heated it up to see if it would have any hardening effect on metal. When taken out it was covered with a silvery coating of zinc and on examining 227 228 • GALVANIZING AND TINNING under the microscope they found it had penetrated and alloyed the zinc witli the body of the metal. Theory of Sherardizing Sherardizing may be defined as a process of sublimation, occlu- sion and adhesion, when considered in connection with the theory Fig. 99. Section of Sheeaedized Steel Magnified 100 Times of ions. The process of passing directly from the solid to the gaseous state and from the gaseous direct to the solid state, in both cases stepping over the liquid state, is called sublimation. The theory of sublimation and the ^'triple point" in connection with sublimation is fully defined and described in many elements of physics. It is a very well known fact that solids sublime. This is easily shown, for example, in the evaporation of ice when it is kept below its melting j^oiut. In the case of most solid substances this process is so slow at ordinary temperature that it cannot be detected. At ordinary temperature and pressure camphor, arsenic and many less familiar substances sublime. Solid carbon dioxide will volatilize at — 79 deg. C. at atmospheric pressure without passing through the liquid state. Zinc as a solid may change into vapor without passing into the liquid state. For an exact definition of the physical condition of a body a knowledge of the values of all its variable 23i"operties is required. The three most important of these are temperature, pressure and volume occupied by unit mass of the substance. These are not independent of each other but are connected by a definite relation called the equation of state, which^ Till'] ART OF SIIKRAlIDIZlNa 220 ill the simple state of ])erfect <2:ases, takes the form of the gas law, which is the law of Boyle and Charles. It is a well known fact that common metals are extremely porous. This is visible under a hiah power magnifying glass, as well as readily demonstrated by certain j)hysical experiments. Thus, if an iron wire be placed in a vacuum tube and then heated to incan- FiG. 100. Section of Cold Rolled Sherardized Steel Mag- nified 1300 Times. Note Zinc-Iron Alloy descence,' as, for instance, by passing a current through the wire, the pressure within the tube rises materially and gas is evolved for a very considerable time, indicating that iron (and practically all other metals) contain large volumes of gases. The condition of the metal may be graphically described as resembling a sponge soaked with water. The two photomicrographs reproduced in Figs. 99 and 100 show pieces of Sherardized steel magnified so as to show the zinc and iron alloy after Sherardizing. How Precipitation of a Vapor on Metal Occurs When a porous solid is easily permeated by a gas and condensa- tion on the surface of the pores of the solid takes place, it is called occlusion. An example of this can be seen in the absorption of 90 volumes of ammonia in one volume of charcoal. Spongy p.lati- num will absorb about 250 times its own volume of oxygen. Pa- ladium will absorb about 1000 times its own volume of hydrogen 230 GALVANIZING AND TINNING and will increase one-tenth of its volume. To produce such a condensation alone would require a pressure of many thousand pounds per square inch. Nearly all metals absorb gases and, being heated, will allow them to pass through readily. An example of this is the fact that hydrogen will readily pass through heated iron. When a gas is in contact with a solid, there are molecular forces drawing the particles together, and this produces a surface con- densation of gas on the solid. An example of this is the difficulty in removing the last traces of air from a vacuum bull) due to the adhesion of the air on the surface. Another example is the frost- ing of window panes in irregular figures. There also appears to be an electrical condition accompanying the evolution of gases from a metal inasmuch as the evolved gases usually contain a number of free ions. This is particularly the case if the temperature of the metal is high at the time the gases are given off. Naturally the exposed surface of the metal is the only portion which actively takes part in evolving gases, so that the larger the area of surface exposed the greater the evolution of gas, other conditions l^eing equal. A further fact, which is well established, is that the presence of free ions has a marked effect in producing a precipitation of a vapor or suspended matter in a gas It follows, therefore, that if a metal be heated in the presence of a vapor under such condi- tions that the gases or vapors contained within the metal are in part liberated; then, as the liberated gases or vapors contain some free ions, they will cause the precipitation within the pores of the metal and on the surface layer of a portion of the external vapor in which the metal is heated. Now it is a well known fact that all materials have a definite vapor tension, dejDcnding mainly on the nature of the material, the nature of the surrounding materials, the temperature and the pressure. It therefore follows that under all conditions all sub- stances are surrounded by a certain amount of their own vapor. The vapor can be increased in amount by increasing the tempera- ture and decreasing the pressure. Methods of Producing Zinc Vapor Zinc vapor can be produced in several ways from zinc. If molten zinc is boiled in a reducing atmosphere, vapor is given off rapidly and if heated iron is brought in contact with this vapor Sherardiz- THE ART OF SHERARDIZING 231 ing would take place. This method, however, is neither convenient nor economical because of the waste of zinc. The most practical and economical method is to use zinc dust, which is obtained as a by-product of a zinc smelter. This dust is practically amor- phous and each particle consists of a small inner particle of more or less pure zinc surrounded by a thin coating of zinc oxide. According to a well known fact, the vapor tension is higher for small particles than for large. It is thus desirable that the zinc be in a very finely divided condition, for the extent or degree of penetration of the zinc vapor in the iron depends upon its vapor tension. It is also desirable that there be as little impurity in the zinc as possible, for not only the zinc, but also the impurities, such as lead, cadmium, etc., will give off vapors, and the combined vapor tension of the mixture would generally be less than that for pure zinc. As said l)efore, the zinc particles are surrounded by a coating of zinc oxide. This oxide is very inert compared to metallic zinc and has a high melting point. It therefore is ver}^ advantageous in the process because it not only keeps the particles of zinc separated, but allows the spheres of vapor surrounding them to act independ- ently with a high vajDor tension and permits the temperature to be raised beyond the melting point of zinc without its becoming molten. Therefore, the percentage of inert material in the zinc dust pla3's an important part in the process. Since the process of Sherardizing is being carried on all over the country under different conditions and for different purposes, it is impossible to give any specific rules for Sherardizing. The follow- ing suggestions, however, can be applied in general to all plants using this ]3rocess. The process of Sherardizing can be divided into the following steps or stages, each of which has a definite relation to the whole : 1. Inspection. 2. Equipment. 3. Zinc dust. 4. Cleaning or preparing of surface. 5. Temperature and Time. As said before, the articles to be Sherardized cannot be selected without increasing their cost, but this does not mean that every- thing can be Sherardized. If the article is excessively corroded or covered by inburned slag (sometimes found with malleable iron) 232 GALVANIZING AND TINNING to such an extent that ordinary methods of cleaning will not re- move it, it will not be advisable to attempt Sherardizing. In this case such articles should be removed on inspection. Many people were of the opinion when taking up this process that anything would Sherardize regardless of the condition of the surface, and this is the prime cause of the dissatisfaction at the introduction of the process. Just as in the electro galvanizing and the hot galvanizing proc- esses, so in Sherardizing, the surfaces must be thoroughly cleaned. A hot galvanizer or an electroplater would not think of galvanizing an article that was not free from scale, rust, grease, dirt or other impurities, and it is also important that this is done in Sherard- izing, if satisfactory results are desired. CHAPTER XXV Location and Equipment of the Sherardizing Plant WHILE the Sherardizing business can be carried on in ahnost any kind of a building, the floors should l^e of cenieiit or brick as a safeguard against the excessive heat of the Sherardizing cylinders or drums. Outbuildings of one story are preferable, as it is entirel}- practicable to combine the pickling and cleaning with the Sherardizing. AVhile the space required for a complete Sherardizing plajit ^•aries according to the demands and volume of work to be handled, a plant of a daily capacity of one ton for treating miscellaneous articles, such as Ijolts, screws, nails, chain, stampings, etc., can be carried on very comfortably in a floor space of GOO square feet. Little can be said in regard to equipment unless the articles to be Sherardized are determined. If there are bolts, nuts, washers, stampings, forgings or articles of malleable cast iron, the equip- ment would be very different than in the case where large railroad material, structural iron, etc., are treated, or where continuous Sherardizing is applicable, as with wire, woven wire cloth, nails, sheet metal, chains, etc. Fig. 101 is a typical layout of a floor plan showing positions of an actual Sherardizing plant. The general equipment of an ordinary Sherardizing plant consists of a furnace, drums, transfer trucks, R. R. track, cooling frame, pyrometer, dust screening machine, ash cans for holding zinc, loading frame, "I" beam, carriage and hoist, drum pulling machine, pickling tubs, tumbling barrels and sand blasting outfit. The old pickling tanks which are now used almost exclusively for galvanizing work coiisist of four large wooden tanks set end to end and one iron tank. Each taidv has a water and steam inlet and a drain pipe. The new pickling tanks are used for Sherardizing work and consist of eight small tanks set in a row in groups of two. The first tank contains potash, the second hot water, the third hydrofluoric acid, the fourth hot water, the fifth sulphuric acid, the sixth hot water, the seventh lime water and the eighth hot water. Each tank is equipped Avith a steam and water inlet 233 234 GALVANIZING AND TINNING and a drain while tlie liot water tanks also have overflow pipes. An electric hoist rinining on a Clolmrn track runs over the pi(.'kling tanks and is used to lift the ))askets of material from one tank to another. A sand tumbler is also used to clean the material to be Sherardized. I'lO. ]01. Floor Pt.an- of Shekakdizing Pi-ant The Sherardizing Furnace or Oven There are several different st3des of Sherardizing ovens or fur- naces in use,whicli will hold one or more drums, according to the capacity required. Coke Burning Furnace Figs. 102 to 106 show the type of a coke Imrning furnace designed by A. F. Schoen of tlie New Haven Sherardizing Go. This furnace is especially valuable in suburban districts where no other fuel is available. The furnace is built of {)" fire brick walls reinforced with steel jalates; has individual damjDer controls so that the heat, which passes between two arching bridges, can be directed to either the front or the rear of the furnace. It is built on the down draft principle, the heat passnig directly over and on top of the drams. A baffle plate is dropped about 6" below the inlet and uni- formly distributed in the furnace. The surplus heat is then taken off underneath the floor and passes out under the furnace diagon- ally, making a super-heating furnace. Owing to the fact that the LOCATION AND EQUIPMENT OF SHERARDIZING PLANT 235 I'iG. 102. View of Coke Burning Fuknace of Three-Drum Capacity -9'3l"- d Fig. 104. Front Elevation of Three-Drum Coke Burning Furnace 236 GALVANIZING AND TINNING Fig. 103. Anotheu View of Same Furnace, Showing Operating Devices Fig. 105. Side Elevation of Tiieee-Drum Coke Burning Furnace LOCATION AND EQUIPMENT OF SHERARDIZING PLANT 237 heat strikes the drums on the upper side, it has l^een found that the work must rotate more constantly than is necessary in a gas and oil hurning furnace. Under these conditions it is necessary to have an automatic rotating device. ■-=1 r Fig. 106. Section of Thkee-Duvm Coke Burning Furnace Taken Above Firebox The details of construction are clearly shown in the elevations aud sectional drawings given in Figs. 104, 105 and 106, Single Drum Coke Burning Furnace Fig. 107 illustrates a single drum coke burning furnace also built by Mr. Schoen. It is reinforced on three sides with steel plate, with an inner lining of 9 inches of firebrick and single arch. A feature of this furnace is that it can be grouted so as to bring the door proper in line with floor, which obviates the necessity of a transfer car. This also applies to furnace in Fig. 102. The grouting can only be done on the ground floor. The details of construction and general operation are clearly shown on the floor plans and elevations given in Figs. 108, 109 and 110. This fur- nace can be lengthened to eight feet long and operated uniformly from a three-foot firebox. 238 GALVANIZING AND TINNING Note the drum turning device through furnace door. This was necessary through lack of room in rear of furnace at which point all rotating devices are generall}^ attached. Controlling Heat of Single Arching Furnace Unlike the double arching furnace, which forms a pocket from which the flame and heat are uniformly forced into the furnace, Fig. 107. Single-Drum Coke Burning Furnace in a single arch furnace it comes directly over the inner wall as shown in Fig. 109, and the flame therefore has a tendency to go to the rear of the furnace even though the exhausts are at the front. LOCATION AND EQUIP:\IENT OF RHERARDIZING PLANT 239 This is overcome l)y tapcriii,i( the outlet or haffling the brick at various points. A baffle pUite is attached to the arch directly over the drum to brake the flame and direct the heat so it will Ijc uni- formly distributed around the drum or receptacle. Gas and Oil Burning Furnaces Fig, 111 illustrates a small self-containing furnace built of struc- tural iron and brick, with the cover attaclicd l>y hinges, lined Avith -i>l<- — ,— ^'2!'- Fig. 108. Fkont Elevation of Single-Drum Coke Buening Furnace Fig. 109. Side Elevation of Single-Drum Coke Burning Furnace 240 GALVANIZING AND TINNING fire brick and fire clay on the inside for gas or oil burning. The material Sherardized in this oven would probably be bolts, nuts, washers, small malleable cast-iron articles, small Fig. 110. Section of Single-Druji Coke Burning Furnace Fig. 111. A Self-Contaimld Gas, ±i ukxaue and Drum castings and forgings and all small or medium sized iron or steel pieces that would pass through an opening 10 x 3G in. A special feature of a furnace of this kind is tliat it can be placed LOCATION AND EQUIPMENT OF SHERARDIZING PLANT 241 anywliere in the factory and operated at very little expense, re- quiriiio- no elaborate equipment in luiiidlini>', and is very convenient e\on ill tiie factories where lar^e Shcrardi/in^- plants are in opera- tion, due to the fact that small sjDecial work, which could not be Fig. 112. Gas Burning Furnace Used by New Haven Sherardizing Co. run in furnaces where two and three cylinders were operating at one time, can be taken care of. Fig. 112 illustrates the type of gas burning furnace used. This style of furnace is also operating successfully with natural gas, producer oil and fuel oil. Figs. 113 to 114 are detailed sectional views of gas and oil burn- ing furnaces. You will note that the only difference between the two furnaces is that the combustion chaml3er for the oil is more thoroughly reinforced at the floor lines, the combustion taking 242 GALVANIZING AND TINNING 2)lace between the floor and the upper baffle bricks and coming out at the sides. The gas burning is an open flame directly against the drums, taking air from underneath the furnace, the air fol- lowing along the burners. This applies where no pressure is used. In cases where gas is used under pressure then use the same equip- Door Hoist ■7-T~T> — T' f^s ,,- Angle Iron for Gas Burning only ^ -^ .■4"Tlrons-, JL 4"^4"^m_^. :' , 4"Tile for Oil ■ /' Burning only I ', Gas ,;^g Q.-Burners- s; s: 2" space befwee i ■' Baffles Brick r^--Peef Pier g^ Holes T*7= l-'^ Hi: a X u. k-A;. -2" Pipe -----7'6"'k 7 Baffle Brick for Oil Burners Fig. 113. Section of Furnace Showing Difference in Reinforcing of Combustion Chamber foe Gas and Oil T B x_ Wall or ■vh- II l' iS 3^ .-- Baffle Tile \/n3 Sections -AirMix.er Gas Cocks Fig, 114, Plan of Furnace Showing Arrangement of Combustion Chamber for Gas and Oil Location and equipment of sherardizing plant ^4S 244 GALVANIZING AND TINNING ment as for oil, allowing more relief from the combustion chamber or a slight baffle which will distribute the fiame uniformly. As shown in Fig. 113, an angle iron is to be used for gas burning at that point only; for fuel oil, which gives off great heat and back jjressure at intake, would quickly warp any metal parts and render it useless as a frame support. A tie rod at the floor line well pro- tected with bricks is recommended. Fig. 115 shows a furnace in the plant of the American Tap Fig. 116. Two COMPABTMENTS OF THE FUENACE SHOWN IN FiG. 115 READY TO Receive the Drums Brush Co., of Detroit, Mich., which has a capacity of twenty tons per day. The drums are 5' long, 18" in diameter, and the furnace is so built with separate chamljers that, if the treatment of longer material was required, they would simply have to couple the drums together to any desired length. This plant would be a valuable I^lant to any one doing jobljing work and having a variety of ma- terial to be treated in different lengths. Fig. 116 shows two comj)artments of the furnace ready to receive an 11% ft- drum. It also shows the method of turning the drums and the combustion chamber. lOQATION AND EQUIPMENT OF SPIERARDIZING PLANT 245 Fig. 117. A Fuel Oil Burning Fuknace of Four-Dkum Capacity Fig. 118. Type of Oil Burning Furnace 246 GALVANIZING AND TINNING LOCATION AND EQUIPMENT OF SHERARDIZING PLANT 247 248 GALVANIZING AND TINNING Fig. 117 is a view of the John Finn Metal Co.'s plant, in San Francisco. This is a fuel oil burning furnace of four drum ca- pacity. The drums are rotated by a reciprocating movement of the carriage from one end of the furnace to the other. Consider- able space could have been saved in this furnace by installing a pivot motion. The pivot motion is shown in Fig. 118, which illustrates the type of furnace used ]>y the Westinghouse Electric and Mfg. Company and the Union Switch and Signal Company. This furnace was installed for oil fuel, but there is no reason why it may not be used for gas, producer gas or natural gas. All that is necessary is to change the inside floor plans to provide the desired combustions. Figs. 119 and 120 show the loading and cooling platforms of a furnace operated by the National Metal Molding Co., of Pittsburg, for treating conduit pipe and conduit fit- tings, and has a capacity of about thirty-five tons per day. This type of furnace is also recommended for water pipe and tubing. The drums'are automatically taken into the furnace on very heavy chains and are automatically rotated with a sprocket attached to the center of the drum, the chain passing beneath with a continu- ous movement and protected from the flame. Fig. 121. Series of Electric Heated Sherardizing Machines Electrically Heated Furnaces or Drums A new departure in the Sherardizing field is the special type of electrical heated apparatus designed for the General Electric Co. This company coats considerable malleable iron and they are now LOCATION AND EQUIPMENT OF SHERARDIZING PLANT 249 Fig. 122. 24" x 24" x 40" Electric Heated Sherardizing Machine IN Operation m eso yoLTS L/fi/e coveff u/\nr "1 n n ri n n I I I ' I I I I I I .1111 I I I I I I I I I I 3^ n r-j fT [T r] r-| n r" I I I I I I I I i I 1 I I I M I I I I I I Lj lj lj lj lj lJ lj S/D£' t/A//T n f-i n n r I rn n ' I I Mill I I I I La LJ LJ LJ LJ LJ L. SlO£ i/A// r Fig. 123. Layout foe Wiring of Electric Heated Sherardizing Machine 250 GALVANIZING AND TINNING using two sizes of machine; one 10" x 10" x 17" inside dimensions and requiring 15 kw. to bring up to the desired temperature and 5 kw. to hold correct temperature, and a larger one 24" x 3 i" x 40" inside dimensions requiring CO kw. to heat up and 15 to hold at that temperature. The former is illustrated in Fig. 121 and the latter is shown with connections for heating in Fig. 122. It will be noted that the machines are rectangular in shape and are revolved ])y a driving motor mounted on one of the pedestals and geared to the drum through a reduction worm gear. The heating elements are placed on each of the four sides and both ends of the machine, and the current is supplied to them through three collector rings at one end of the machine. Wiring Diagram The connections are such that the drum can be operated on a three-wire 250/125 volt D.C. circuit or a three-phase A.C. circuit. The only change necessary for a three-phase A.C. circuit is to leave off the wire leading to the bottom middle clip of the T.P. D.T. switch. The general scheme of inside and outside wiring for the two drums may be seen in Fig. 123. This layout is for a 250/125 volt D.C. circuit. Drums The requisite number of drums or containers can be made in either cylinder, square or flat, suitable for material to be treated. For instance, .-mall articles that can be handled readily with a shovel or chain in bundles it is best to treat in a round cylinder, averaging from 15" to 20" in diameter and up to 6' long. It is not necessary to make these drums out of heavier than i/^" boiler plate, as there is no actual wear in the low degree of heat main- tained. It has been known that drums in daily use up to eight years show practically no wear and are as good as new. A square drum is used a great many times for light material, and a top opening cover is recommended instead of an opening at the ends. This will allow perfect packing, so that when the articles are taken out they will not be bent or warped. It is, however, recommended that drums not over 20" square be used on such light material to insure uniform penetration. In the case of flat stock for panel work, etc., a flat drum of not over 16" in depth is recommended, as the stock, being flat, will lie very closely and it LOCATION AND EQUIPMENT OF SHERARDIZING PLANT 251 would be impossible to get a i)erfeet, uniform coating if the diameter was increased. The length and width make no difference. Fig. 12-i illustrates a cylinder drum 15" to 20" in diameter, made of Vi" boiler plate, welded. The liange and liead are cast or mallealile iron and are machined to make a dust proof fit. There is one feature that deserves special attention. It is the use of slotted parts instead of holes for fastening on the heads. Ordi- narily the bolt will expand with the lieat to such an extent that it is impossible to remove the nut, but with the above arrangement the bolt can be removed without injury, or where the nut will not come off it will loosen sufficiently to work out of the slot. Fig. 124. A Cylinder Drum Dust Separating Machine Fig. 135 gives a sectional view of a dust separating ma- chine. This screener, which is known as a cylinder screener, is made of structural angle iron, 2i/^" x i/4", and matched boards, thoroughly reinforced, and the screen is made of per- forated metal. The work is received at one end, the dust dropping through into a receiving box and the material com- ing through at the other end free from dust. It has been found, in a good many instances, that on flat stock or cup-shaped material the dust is not all relie\ed at the first screening, in which case a conveyer is made of two pieces of 5" x 5" angle iron and a carrying belt is placed on the receiving end of the screen and conveyed to another screening machine of the same type, which will relieve such zinc as has passed through the first screener. A conveyer of 252 GALVANIZING AND TINNING this type is very easily constructed and inexpensive, and saves a lot of shoveling and handling. The gear pattern is so arranged that it can l^e operated with worm drives. Fig. 125 illustrates the style and make of dust separating machine used. This screen can be placed anywhere on the floor, no pits or conveying device necessary. The machine will hold about three thousand pounds of zinc at one screening. Fig. 125. Dust Separating Machine Mr. tSchoen of the New Haven Sherardizing Co. has spent a numVer of years perfecting this machine, and l^elieves that a ma- chine of this type should be part of the equipment of every plant, for it is inexj)ensive and turns out clean work. An exhaust hood should be attached to carry all zinc residue to the reclaiming box. Fig. 136 shows this same screener in operation, receiving the work from the drum ; also a hood placed in such a position that the light zinc dust, which is bound to fly, is taken care of under a slight suc- tion. The drum is conveyed by means of an overhead trolley. The head is removed from, one end of the drum and the material is LOCATION AND IXiUlPMENT OF SHERARDIZING PLANT 2.13 clumpt'd into the ho])i)er. The screen revolves al)out forty revolu- tions i)er minute, the dust droppiiig through into the receiving hox below and the material coming out at the other end. A hood is Fig. 12G. Dusx .Sckeener in Operation placed over the receiving hopper at the end where the material comes out ; an exhaust is attached with enough suction to take care of whatever dust may escape. This is exhausted into a canvas- covered box and saved. The Transfer Car The transfer car is not of any special make. It is merely used for transferring drums from one place to another and can be easily built from structural iron with a few cast-iron wheels and bearings, thoroughly reinforced. Generally speaking, these are specially manufactured to meet the requirements of different plants. Fig. 127 shows one type of truck used. The "T"' l)eam is standard, generally using the very lightest, as the weight ordinarily carried in one of these drums is not over one ton, 254 GALVANIZING AND TINNING Fig. 127 also shows three drums placed in position and secured by a locking- frame, which l> ^ / ^ *« '^nn k C.UU / N »v. ■-v 1 / ton / ' 1 1 f n - — 1 50 40 I 20 10 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 Id 19 Hours Run Chart II. Temperature and Power Curve of Electric-Heated Sher- ARDiziNG Machine 24" x 24" x 40" deposit, and then the low heat is thrown on to hold it at that tem- perature for the required period (2^ to 3 hours) to give the de- posit. After this current is thrown off and drum allowed to cool to 180 deg. C, which is a safe temperature to open drum. This should apply to Grasselli zinc only, as blue dust Avill fuse more 272 GALVANIZING AND TINNING rapidly. Charts I and II provide interesting records of the power, temperature and deposit. Sherardizing with Zinc Under Vacuum After reading the above it is clear that to do Sherardizing we should have the zinc vapors at their greatest tension and have Sher- ardized iron in condition to give off the maximum gases. Zinc boils under ordinary pressure at 913 deg. C, and the boiling point under vacuum is reduced to 548 deg. C. Iron on being heated from 500 to 600 deg. C. in vacuum gives off gases readily. Therefore, it is quite clear that in vacuum the conditions are best for Sherardizing, and the writer was able to produce condensation of zinc on iron in a very short time. Some of the results were obtained under these conditions in minutes, where with ordinary. pressure under the same conditions it required hours. This process and the machine for treating material by this method have been covered by patents. The process is not necessarily dependent on having the substances supplying the vapor in the form of a powder, although a substance in this form may often be raised to a temperature above the melting point without fusing the articles together. The elevated tempera- ture which can thus be secured is of material assistance in securing a rich vapor, which naturally hastens the process and therefore is an advantage in many cases. A further advantage of using the material supplying the vapor in the powdered form is the .enor- mously increased surface which can thus be secured, thus giving a richer vapor, since the amount of material vaporized at a given temperature and pressure increases with increased evaporating sur- face. This is particularly of value when the boiling point of the vapor-giving material is above the temperature at which the deposi- tion occurs. Time an Important Factor Just as temperature, so time is an important factor in the process of Sherardizing. Since articles of different size, shape and char- acter are treated, if each were given its ideal condition of tempera- ture and quality of zinc dust, the time of treatment of all would be alike, but this is not practical, for it is easier to vary the time of the process than the other factors. It is possible to obtain almost instantaneous Sherardizing in the case of wire heated to a high temperature and allowed to pass TEMPERATURE AND DURATION OF HEAT 273 through zinc dust at normal temperature. In the case of many articles to be Sherardized tliis method is impractical and so longer periods of time are required. Not only the time of heating the article during the process should be considered but also the time of cooling, for this j)rocess is not confined to any one particular tem- perature, but takes place over a wide range of temperature. If the articles being treated have not become saturated during the heating period, the process will still continue upon cooling, until the tem- perature falls below its minimum point. There are two reasons for slowly cooling: First, to prevent loss from exposing hot zinc dust to the atmosphere (the metallic zinc particles would quickly oxi- dize) ; second, to prevent the articles being chilled too quickly. Motion During Sherardizing The general iDublic has been given to understand that this is a tumbling process, and that the zinc will not deposit unless the drums are continuously rotating. If the articles are thoroughly mixed with the dust, it is not necessary to have the drums continu- ously rotating to insure uniform deposit, providing that the drums are not over 20 in. in diameter. An occasional turn of once in 15 minutes is ami^le to insure good results; too much rotating under heat pressure will make the articles appear dark and dusty. Sherardizing can be and is being done where the articles to be treated are placed in the zinc dust, heat applied, but no motion given to either the dust or the articles during the process. This method is used in the case where large pieces, plates and sheets are being treated. If the transmission of heat through zinc dust were perfect and if the deterioration of the zinc particles were negligible, the motion of the articles during treatment would be unnecessary. Such, however, is not the case, for zinc dust is a poor conductor of heat and the deterioration of the zmc particles in intimate contact with the article treated requires a replacement of the same by new particles. Since this process continues during the cooling period, until it reaches its critical point, where it ceases, the motion will produce the same efl-'ect then as during the heating period. Zinc dust, which is commonly called blue powder, is a flue dust and therefore a by-product of the zinc smelting furnace known as the Belgian furnace. It contains, as a rule, from 75 per cent, to 90 per cent, pure zinc. The supply is ample at a price a fraction above that of spelter, and it can be procured in any quantities that 274 GALVANIZING AND TINNING may be required. The nature of the zinc, which is given off at a temperature of 1,000 deg. C. or more at the inception of distilla- tion, comes into contact with the comparatively cold atmosphere of the flue and the sudden chill causes a rapid condensation of the vapor, so rapid, indeed, that it skips the liquid state and drops into the shape of perfectly spherical articles, of which about 30,000,000 can be crowded into a cube measuring 1/16" in every direction. This impalpable powder, notwithstanding its high specific gravity, for it is only about 10 per cent, lighter than pure zinc, can be blown about like lycopodium. It is used very extensively by textile manufacturers for dye work, and by paint manufacturers, and is sold packed in barrels holding about 1,500 pounds. It cannot be melted into slabs on account of its rapid oxidation at a very low temperature. The peculiar properties of zinc dust have been ascribed by some to the presence of cadium which, being of more volatile metal, is distilled first from ore and then condensed into flues. One observer finds quantities ranging from 0.283 to 0.794 per cent, in flue dust after two hours of furnace operation. Others have claimed that these properties are due to the presence of zinc oxide or other impurities. Most of the zinc is purchased in Belgium or Silesia. Silesian zinc has been found the best adapted for Sher- ardizing, due to the fact that it has less moisture. A sample of an analysis showed the following : Metallic zinc 88.95% Cadium 0.62% Zinc oxide 6.88% Sulphur 0.055% Lead 3.45% Iron 0.04%, A fact that is undoubtedly responsible in a great measure for the mystery attaching to the action of zinc dust is its readiness to oxidize. It is only when oxidation is put out of its power, as in the closed Sherardizing drum, that heat will produce sufficient over- strain to cause the jiarticle to burst into vaporized gas. This gas, so suddenly released, will condense instantly on the coolest spaces it can find. In Sherardizing, the coolest spaces are on the articles in the drum. It is an established fact that in Sherardizing the presence of zinc oxide is necessary. We might suppose, therefore, that a mole- cule of oxide is reduced to voltaic action when it comes into con- tact with the iron. The zinc attaches itself to the iron, which acts, therefore^ as a cathode in electrolysis, £ind the oxygen travels in the TEMPERATURE AND DURATION OF HEAT 275 opposite direction, comhinos with a free molecule of zinc to form a molecule of oxide, ami i^oes through the same performance as before. Zinc dust appears to break down into vapor at al)0ut 150 to 200 deg. C, although it nn(loul)tedly begins to disintegrate at a lower heat. As the pressure increases it takes a greater amount of heat to cause the breakdown. As the vapor condenses the pressure is relieved and the hotter articles of dust are vaporized and re- establish an equilibrium. Being a gas, the zinc vapor can force itself into the pores of the metal and form a deposit to a dejDth which will increase with the duration of the treatment. Bapid cooling will cause the zinc to condense as crystals, the ad- herence of which to the iron is, however, inversely proportional to their size. Normal cooling would seem to yield in all cases a fine, glossy surface of what can be appropriately termed ferrozinc. General Operation There are three factors to contend with in the process of Sher- ardizing, viz., zinc dust, temperature, and the length of time the heat is run. For example, take a standard size cylinder or drum 15" to 20" in diameter, i/j^" wall, new zinc dust at 90 per cent, metallic, tem- perature 750 deg. to 950 cleg. F. outside of drum, with pyrometer stem showing at the bottom of the drums and protected from the flame by a baffle plate, the furnace started cold and allowing two hours to bring the temperature up to the required number of degrees and held at that point for three hours, should give good results. If, however, the deposit should not be sufficient, then the temperature should be slightly increased, say 25 deg. or the time of operation extended; but rules generally followed to compare with the ordinary ten hour per day time is to increase the temperature, which applies to ordinary material only. In cases where high tempered steel or spring stock is treated the time of operation should be extended and the temperature reduced to about 650 deg. F. for a 15" drum and 700 deg. F. for a 20" drum. The drums are then taken out and allowed to cool (under no circum- stances should the drums be opened while hot, as the zinc dust will fuse and burn). The time generally allowed for heats on ordinary material is 276 GALVANIZINa AND TINNING five and a half hours for the first heat, started from a cold furnace, and four and a half hours for the second heat, which allows one- half hour for making the change. Fig. 132. Unloading into Rotaky Dust Separator After loading, the drums are sealed and rolled into the Sher- ardizing furnace, as shown in Fig. 119 or 128. Here they remain for 5 to 6 hours, according to the tonnage that they contain, in an evenly maintained temperature of 780 deg. F. Cooling and Unloading Upon removal from t]ie Sherardizing furnace the drums are rolled out on the cooling platform, as shown in Fig. 120 or 128, and allowed to cool out, as it is called, for 12 to 16 hours before TEMPERATURE AND DURATION OF HEAT 27? tliey are unsealed, as the introduction of oxygen to the zinc while in a superheated state would, of course, destroy it. The annealing in- cident to the slow heating and slower cooling through which articles pass in the process makes Sherardizing doubly valuable as a finish for steel products which, like electrical conduits, must be bent during installation, and for many cast-iron articles which would otherwise require a separate operation for the purpose. After "cooling out" the contents of the drums are dumped into large hoppers, as shown in Fig. 132, and the surplus zinc dust rocked out, leaving, in addition to the zinc-iron alloy, an exterior coating of zinc. CHAPTER XXIX Don'ts in Sherardizing Practice THE following account of the inspection and reorganization of a Sherardizing plant is included so the users of this hook may profit hy the experience of others and use the many valuable suggestions it contains in their own practice. The plant was installed for the purpose of Sherardizing ma- terial for their own product. The material included bolts, nuts, malleable iron castings and line material. When the plant was in- stalled the men in charge of the plant knew practically nothing about the process. Sherardizing was done in the same room with pickling and hot galvanizing. The steam and acid fumes from the large pickling tanks (used for pickling large castings preparatory to painting) not only had a deleterious effect upon the Sherardiz- ing process, but also in connection with the zinc dust in the air, made working conditions almost intolerable. Whenever articles were pickled in large quantities they were first placed in an empty acid tank and the acid and water poured over them until covered. When, on inspection, the pickling process was completed, the acid was allowed to run into the sewer. Before all of these pickled articles could l)e washed off most of them had acquired a thin coating of rust which necessitated another dip in the acid before being Sherardized. No unloading pit liad been provided, the dust being dumped upon the floor to be trampled under foot and, on sev- eral occasions, to be flooded by water. Tlie ovens, too, were not suita1»le for the work. The clutches wliich connected the drums with the driving mechanism were crude and clumsy so that they could not be applied from outside. Tliis necessitated cooling of the ovens to allow a workman to enter the oven to attach a clutch. Considerable trouble had been encountered by the dust caking and balling in the drums. This became so bad at times that nearly a whole drum of work would be scrapped and much dust wasted. This condition was practically eliminated by confining the dust in a bin away from all water or acid vapors, as well as keeping the temperature within the limits for the particular dust used. The large pickling tanks and paint tank were removed from the build- 278 DON'TS IN" SHERARDIZING PRACTICE 279 ing, giving more room, improving working conditions consi(leral)ly and especially reducing the amount of acid fumes coming in con- tact with the zinc dust. Eliminating Black Spots on Finished Work One of the principal difficulties was the elimination of black spots on the finished work. At times this became very excessive, not only detracting from the appearance of the work but also re- ducing the number of dips the material would stand under test. Two principal causes were found for this fault. The first was the presence of "Tjurnt in" slag in the corners or crevices of the ma- terial which it was almost impossible to remove by pickling in some instances. This was corrected by more intelligent inspection of the material, both before and after pickling. In connection with inspection, it was found that the material received practically no inspection before treatment. Whenever slaggy material reached the Skerardizing department, the inspector was notified and it was often found that the material had been removed from the foundry more than two years before. An entirely new system of inspection has since been adopted, which has taken care of the black spots from this cause. The second cause was the presence of acid in the spongy or por- ous parts of a casting which was not thoroughly washed out or neutralized. It was difficult to obtain castings without some por- ous parts or corners that were filled with fine cracks, but by careful attention to pickling and neutralizing the black spots were re- duced to a minimum. Obviating Non-Uniformity of Coating Another fault was the non-uniformity of coating even with the same kind of material in the same drum as shown by testing some of the material from difl'erent parts of the drum. A heat analysis of the furnaces showed a variation of temperature. This affected the uniformity of coating considerably, notwithstanding the drums were rotated through the run. This fault was corrected by putting new baffles in the furnace, additional heat insulation on the doors, and new burners, which gave more uniform distribution of heat. New clutches were also included in the general overhauling of the furnaces, which allowed the driving mechanism to be connected to the drums from outside the furnaces. 280 ■ GALVANIZING AND TINNING In order to save the excessive waste of acid eight small pickling tanks were installed, together with sufficient baskets for liandling the material. An electric hoist was installed for handling the baskets of material from one tank to another. By this betterment the quality of pickling was improved as well as reducing the amount of supervision required because of systematizing the process. By handling the material in smaller quantities during pickling it was found that better insjDection was possible. Some difficulty was encountered in the case of one particular malleable iron article, or cap, which was swedged on the end of a wooden rod. In this case the Sherardizing must be done before the iron cap was formed on the rod. Whenever the Sherardizing was heavy this forming process would cause the cracking or peeling of the coating. By increasing the temperature and decreasing the time of the process (using blue dust) the quality of the coating was much impi'oved. In this way the Sherardized articles would stand the same number of dips test with a much thinner coating and would retain their coating through the forming |)rocess. Improving Psychological Condition of Men In this connection the improvement in the psychological condi- tion of the men cannot he overlooked. Under the adverse condi- tions the men, including those in charge, were very skeptical of the process. By explaining the process to them and investigating each part of the process with their co-operation it was found that much could be accomplished. This was done by improving the unbear- able working conditions, as well as those having a direct bearing upon the process. Since these improvements were made this plant has been doing as good work as any others, while still further im- provements would probably increase the convenience and lessen the cost of the process. This is an example of what has been done in one case to improve a plant aud may be a means of helping others to overcome their difficulties, who have had the same or similar conditions to contend with. It must be understood that zinc penetrating the metal is bound to bring to the surface all impurities and, while it does not inter- fere with the rust proofing qualities of the article, it makes it objectionable in appearance. The claim has been made that articles coming direct from the machine, covered with oil, can be Sherard- ized without cleaning. This is true where no fats are used with the DON'TS IN SHKRARDIZING PRACTICE 281 oil. In case of fats where tlie zinc will al)sorl) it, it will redeposit these fats on tlie surface in the form of oxides, which lias heen mis- taken in some instances for rust, as the appearances are very nearly alike. The two main fats used in oil for cutting down threads are ])ean oil and cotton seed oil. In case of clean oil, free from fats, with the zinc of sufficient strength to force its way through and ahsorh the oil, no special cleaning is required, l)ut experiment- ing along these lines brings out the work dark. This also is an objectionable feature and tlierefore has not been found practicable when considering the small cost of cleaning. Caution Careful attention must be given to see that the dimensions of the l:)olts and nuts shall be such as to allow for enough clearance for the various kinds of zinc coating. These dimensions, where in normal cases the test is from 6 to 8 dips, should have an allowance for 8 to 9 mils. Don'ts DON'T de|)osit or 8 pounds of zinc to make the article rust proof. Four pounds is sufficient, as too heavy a deposit will render the coating brittle and it will flake. DON'T take it for granted that just because you have a nice, bright color it is rust proof. Test it and find out, as colors are very deceiving. DON'T luix your floor sweepings in with your zinc. Save it and sell it, as the zinc dust in continuous contact with iron will gather dirt quickly enough. DON'T leave sawdust and excelsior on the work to mix with the zinc as it will oxidize and darken the zinc and the material. DON'T let 3^our zinc dust stand around in open boxes or barrels as it will absorb moisture. Keep it in galvanized cans and covered. DON'T throw water on zinc in case of fire as same will produce gas. Smother it with a blanket or sand. DON'T get scared if you should look into the furnace and see fire around the cracks of your drums. It will stop as soon as the gas obtained from the moisture is burnt out. DON'T open the drums until they are cold, or at least 150 deg. F. DON'T expect Sherardizing to fill an uncalked seam. It is not a solder. CHAPTER XXX Coloring and Finishing Sherardized Articles BY BUFFING the surface on a fine polishing wheel and afterwards placing it on a cloth wheel for color, a finish can be obtained which is more brilliant than nickel plating, comparing very favorably with silver plating, and which will not tarnish. The article Sherardized is a frac- tion darker and more velvety in appearance, due to the zinc coating, where nickel is a white coating. When cutting down for this finish the impression generally carried is that all the zinc is being ground off and relieved from the surface. This is not the case, due to zinc alloy, and if closely inspected a fine zinc coat- ing will show, even through the most brilliant finish, and there is perfect rust protection, so long as this veining is visible to the naked eye. Further, the friction from a wheel caused in burnish- ing ap the surface has a tendency to increase the crystal hardness of this coating so that it further resists weather action. By taking a piece of cold rolled steel and Sherardizing it to a thickness of .001i/i>", and passing it through the rolls cold and breaking it down twice its length, it will still show the same resist- ance against copper sulphate tests as before this reduction was made. This goes to prove that the more friction that is brought to bear, as previously stated, the more resistance against corrosion. It has also been found that material can l)e top finished in nickel, brass, copper and bronze, also can be readily japanned, enameled, and painted. In the case of copper and 1)ronze, after plating, the material should be set aside and let stand for forty-eight to seventy-two hours, for action between zinc and copper or l)ronze. This action makes the surface appear very dark ])ut, after this action ceases, the work is then placed on a buffing wheel for coloring and no further action takes place. In the case of japanned coating it is recommended that the first dip be made in a solution of about 50 per cent, benzine and 50 per cent, japan. This thin coating insures a perfect body. This is baked on very hard and the second dip should be a heavier coating. 282 COLORING AND FINISHING SHERARDIZED ARTICLES 283 For lacquer finish no special operation is necessary, as it will de- posit as readily as on the plain material. If a smooth surface is required simply buff the article on a cloth Avheel or scratch Inrush before finishing. This ap]ilies to large articles which cannot be tum1)led. To ob- tain tlio smooth surface on small articles for plating or for other purposes, they are placed in a tumbling barrel. For dry tuml)ling use leather meal or leather chips, operation extending anywhere from two to ten hours. For wet tumbling use shot on light ma- tciial only. CHAPTER XXXI Cost of Sherardizing Material per Ton with Different Fuels A GAS burning furnace does not require the heavy re- inforcement that an oil burning or a coke furnace ■ requires because it is not under as much pressure. It has further been found that gas burning furnaces are easier to operate but more expensive. Fuel oil and coke are the cheapest known fuels in the East. Where natural gas is available, this by far is the cheapest fuel. The ordinary wear and tear on these furnaces is very small, due to the fact that less than 1000 deg. F. is required. It should be understood that as little structural iron should be used on the inner part of the furnace as possible, to keep from warping. A coke burning furnace requires about 3000 more brick than the ordinary oil and gas furnace, due to the fact that the fire box must be thoroughly reinforced for high pressure heating and retaining of heat, but with this equipment there are no extra installations such as producer gas machines and fuel oil machines necessitate. Sherardizing is like annealing in that it requires a small amount of labor, and that unskilled labor, placed under proper supervision, can operate the plant as successfully as a high priced laborer: Cost for Fuel Oil Burning Per ton Fuel oil, one gallon per hour per burner, 3 burners per fur- nace, 30 gals, per day of 10 hours, at 5c per gal $1.50 Zinc dust, average deposit 4 lbs. per 100 lbs. of material treated, 80 lbs. per ton, at $5.75 per 100 lbs., average market price 4.60 Labor, two men at 15c per hour, which includes the labor for cleaning, pickling, packing, etc 3.00 Total $9.10 284 COST OF SHERARDIZING MATERIAL PER TON 285 Producer Gas Per ton riynn & Dreft'ein's guarantee, cost averaged at the rate of 80 lbs. Pea Coal, equivalent to 1,000 feet of illuminating gas, at 75c per 1,000; consumption of furnace 4,000 ft. per day would ho 320 11 .s. of coal, at $4.50 per ton $0.72 Zinc dust, average deposit 4 1I)S. per 100 ll)s. of material treated, 80 lbs. per ton at $5.75 per 100 lbs 4.60 Labor, 2 men at 15c per liour, wliiuh includes labor for clean- "ing and pickling, per ton 3.00 Total $8.32 Coke Per ton ColiCj 8 bu. per day at 10c per bu $0.80 Per ton Zinc dust, average deposit 1 lbs. per 100 llis. of material treated, 80 lbs. per ton, at $5.75 per 100 lbs 4.60 Labor, 2 men at 15c per liour, which includes laljor for clean- ing and pickling 3.00 Total $8.40 Illuminating Gas Per ton Gas, 4,000 ft. at 75c per 1,000 $3.00 Zinc dust, average deposit 4 lbs. per 100 lbs. of material treated, 80 lbs. per ton, at $5.75 per 100 lbs 4.60 Labor, 2 men at 15c per hour, which includes labor for clean- ing and pickling 3.00 Total $10.60 This being a patented process a royalty of $2.50 per ton must be added for the cost for every ton of material treated. With a large capacity plant the above cost would be less, due to saving both in fuel and labor. Disposal of Used Zinc or Zinc Residue When sufficient amount of zinc oxide has accumulated with the zinc to warrant disposal, discontinue the adding of new zinc, and 286 GALVANIZING AND TINNING by extending the time of the operation or increasing the tempera- ture, same will be reduced very rapidly until about 20 per cent, metallic, at which time it should be disposed of. There is always a market for this material, providing no sands, flint or other ma- terials are mixed with the zinc for coloring purposes. This has been one of the objectionable features in the process, and very de- ceiving to the public in giving color and not zinc simply for appearance. CHAPTER XXXII Galvanizing Specifications and Tests THE following specifications applied to the galvanized over- head construction material purchased by the Pennsylvania Eailroad for the Philadelphia electrification, and all gal- vanized material used by the New York, New Haven & Hartford Railroad in their electrification improvements was required to meet these specifications before being accepted. Specifications for Hot and Electro -Galvanizing This specification shall apply to all galvanized iron or steel ex- cept that coated with zinc by the Sherardizing process. Coating The galvanizing shall consist of a continuous coating of pure zinc of uniform thickness, and so applied that it adheres firmly to the metal. The finished product shall be smooth. Cleaning The samples shall be cleaned before testing, first with carbona, benzine or turpentine, and cotton waste (not with a brush), and then thoroughly rinsed in clean water and Mdped dry with clean cotton waste. Solution for Testing Coating The standard solution of copper sulphate to be used in testing shall consist of commercial copper sulphate crystals dissolved in cold water, about in the proportion of thirty-six parts, by weight, of crystals to 100 parts, by weight, of water. The solution shall be neutralized by the addition of an excess of chemically pure cupric oxide (CuO). The presence of an excess of cupric oxide will be shown l)y the sediment of this reagent at the bottom of the containing vessel. The neutralized solution shall be filtered before using by pass- ing through filter paper. The filtered solution shall have a specific gravity of 1.186 at 65 deg. Fahr. (reading the scale at the level of 287 288 GALVANIZING AND TINNING the solution) at the beginning of each test. In case the filtered solution is high in specific gravity, clean water shall be added to reduce the specific gravity to 1.186 at 65 deg. Fahr. In case the filtered solution is low in specific gravity, filtered solution of a higher specific gravity shall be added to make the specific gravity 1.186 at 65 deg. Fahr. As soon as the stronger solution is taken from the vessel con- taining the unfiltered neutralized stock solution, additional crys- tals and water must be added to the stock solution. An excess of cupric oxide shall always be kept in the unfiltered stock solution. Quantity of Solution Wire samples shall be tested in a glass jar of at least two inches (2 in.) inside diameter. The jar without the wire samples shall be filled with standard solution to a depth of at least four inches (4 in.). Hardware samples shall be tested in a glass or earthen- ware jar containing at least one-half (i/^) pint of standard solu- tion for each hardware sample. Solution shall not be used for more than one series of four im- mersions. Samples Not more than seven wires shall be simultaneously immersed, and not more than one sample of galvanized material other than wire shall be immersed in the specified quantity of solution. The samples shall not be grouped or twisted together, but shall be well separated so as to permit the action of the solution to be uniform upon all immersed portions of the samples. Tests Clean and dry samples shall be immersed in the required quan- tity of standard solution in accordance with the following cycle of immersions. The temperature of the solution shall be maintained between 63 and 68 deg. Fahr. at all times during the following te!st : First. Immerse for one minute, wash and wipe dry. Second. Immerse for one minute, wash and wipe dry. Third. Immerse for one minute, wash and wipe dry. Fourth. Immerse for one minute, wash and wipe dry. After each immersion the samples shall be immediately washed GALVANIZING SPECIFICATIONS AND TESTS 289 in clean water having a temperature between 62 and G8 deg. Fahr., and wiped dry with cotton waste. In the case of No. 14 galvanized iron or steel wire, the time of the fourth immersion sliall be reduced to one-half minute. Results of Tests^ After the tests described in "Tests" alcove, no bright metallic copper deposit shall show on the samples. In case the article is threaded, the thread shall be clean and true after galvanizing and shall stand at least one immersion in the test solution. The rest of the article shall stand the specified four immersions. The threads of nuts, except those galvanized by the electrolytic process, shall be cut after galvanizing, and the threads shall not be required to pass the tests. Copper deposits on zinc, or Avithin one inch of a cut end, shall not be considered causes for rejection. In case of failure of only one wire in a group of seven wires immersed together, or if there is a reasonable doubt as to the copper deposit, two check tests shall be made on these seven wires and the lot reported in accordance with the majority of the sets of tests. Failure to Meet Requirements Any shipment or part of a shipment, the samples from which fail to pass the above requirements, may be rejected. Testing Galvanized Products Obviously the only final durability test of a zinc coating is the test of time while in use under actual conditions of exposure. This method however takes too long for commercial purposes and some other means of making comparative tests Avhich will give prompt results must be adopted. Several such tests are in general use, and the following information taken from a booklet entitled "The History and Development of the Galvanizing Industry" and reprinted in Metal Indusfrij covers the subject in an interesting manner : Tlie outward appearance of any galvanized article is not neces- sarily an indication of its excellence. This statement may be taken as a general rule applying to articles coated by either of the galvanizing processes mentioned herein. 290 GALVANIZING AND TINNING For over forty years prior to 1880 the hot galvanizing process, Avhich was practically the only galvanizing process in commercial use prior to that time, was believed to produce uniform results. It was, therefore, not deemed necessary to test such coatings by any other means than that of durability under actual weather con- ditions. Observations made by Sir W. H. Preece, chief of the British Post Office Telegraphs, led him to see the necessity of a test for zinc coatings on telegraph wires. Preece, or Copper Sulphate Test Between 1880 and 1890 Preece devised what is known as the "copper sulphate test" for galvanized articles, and this test has until recently been accepted as the final word regarding the quant- ity of any galvanized product. This test has been modified and standardized in the United States^ notably by the chief engineer of the Western Union Telegraph Company, and has been quite generally adopted by producers and consumers of galvanized prod- ucts, such as wire, sheets, line material, etc. The original Preece test consisted in the immersion of the gal- vanized article in a saturated solution of coj^per sulphate for a period of one minute, removing, rinsing in water, wiping and again immersing in the copper sulphate solution. The number of immersions which the article could withstand before showing bright copper on the underlying steel or iron was taken as an indication of the excellence of the zinc coating. Temperature Important As at present standardized careful preparation of the copper sulphate solution is necessary. The solution is brought to a den- sity of 1.186 specific gravity at a temperature of 65 clegs. Fahr. This solution is usually treated with a small portion of cupric oxide to neutralize any free acid which might exist in the copper sulphate crystals. Galvanized articles are first to be cleaned of dirt and grease by immersion in gasoline or benzine, then rinsed in water and wiped dry. After this preparatory treatment the articles are given succes- sive one-minute immersions in the standard copper sulphate liquor, held at a temperature of from 65 to 70 degs. Fahr., rinsed thor- oughly in water and wiped dry after each immersion. The samples are to be carefully scrutinized after each immersion, and if spots GALVANIZING SPECIFICATIONS AND TESTS 291 of a clear copper color are observed, the coating is said to have failed. The number of successive immersions which the article will withstand without sliowing indications of clear copper is taken as an indication of the quality of the coating. A new por- tion of solution is to be taken for testing each article. Limitations of Copper Sulphate Test It will be noted that the Preece, or copper sulphate test, de- termines onlv^ the thickness of the zinc coating at its thinnest por- tion. It is, therefore, not in any sense a determination of how much or how little zinc is deposited on the article under test. It is well known that the copper sulphate test is unsuitable for test- ing Sherardized articles, and it is a fact, however not generally known, that the copper sulphate does not attack zinc coatings deposited electrically, and by hot galvanizing methods at equal rates. It has been further demonstrated that the different tem- peratures of the molten l)ath and different methods of cooling articles galvanized in molten zinc show entirely unreliable results when subjected to the copper sulphate test. From these remarks it will be seen that it is unfair to test competitively zinc coatings applied by Sherardizing, hot galvanizing and electro-galvanizing methods. Lead Acetate Test Owing to the unsatisfactory results secured by means of the copper sulphate test, in a measure pointed out in the preceding paragraphs, an accurate quantitative test for galvanized ^^roducts has been devised. The lead acetate test, as it is known, was re- cently originated by Prof. W. H. Walker, of the Massachusetts Institute of Technology, Boston. The test is designed to show the weight of actual coating cov- ering products galvanized by any of the well-known methods. It takes into consideration the impurities residing in the coating and the main impurity usually found, i. e., iron, may be determined if desired. In practice, however, it is seldom carried out to this extent. The solution employed removes from the articles both the zinc and zinc-iron alloys present. The accurate weight before and after testing furnishes the basis for computing the quantitative value of the coating. It is unnecessary to take the time of sample immersion accurately, in which respect the lead acetate test differs 292 GALVANIZING AND TINNING from the coiDper sulphate test ; hoAvever, the weighings, which must be accurate to one milligram, require considerable time and care. The lead acetate solution is prepared as follows: Dissolve 3 pounds of commercial lead acetate crystals (Pb (C2H302)3-|-3H„0) in one gallon of distilled water and add 1 oz. litharge (PbO). After complete solution of the lead acetate, tJie mixture should l)e stirred vigorously and any undissolved resi- due allowed to settle. The clear liquor is then poured off and the solution is ready for use. It is unnecessary to maintain any ac- curate temperature of solution as is required in the copper sulphate test, and the solution may be used for several tests without renewal, until such time as the action becomes too slow. Samples of galvanized product are first to be thoroughly cleaned of oil and dirt by rinsing in benzine or in gasoline, then rinsing in cold water and dried with clean cotton waste. The sample should next be weighed to an accuracy of one milligram, and the weight noted. The samj^le is then ready for immersion in the lead acetate solution. The length of time during which the sample is under treatment is usually aljout three minutes, althougli it may be left in for a longer jjeriod without affecting the result. These immersions should be repeated until all of the coating has been removed and the sample exhibits the clean steel underneath. A short experience will enable the operator to tell with certainty when all of the coating has been removed. After each immersion in the lead acetate solu- tion, the fiocculent or loose coating of spongy lead which is de- posited must be carefully removed ; for this purpose it is usual to employ a small, soft l)ristle brush, care being taken that no lead is 'H^urnished" over the zinc coating. If any spots of lead are noted, which the solution does not remove, the careful use of a sharp knife is necessary. When the coating is all removed, the sample is then dried by immersion in alcohol and ignition, or by placing over a small steam coil. Final weight of the sample is then taken and noted. If it is desired to estimate the amount of iron in the coating, the samples must be rinsed in clean water contained in a beaker, care being taken that all lead acetate and solution washings are saved. The lead acetate and the wash solutions may be put to- gether and filtered, and slightly acidified with sulphuric acid ; a few particles of granulated zinc should then be added, when the GALVANIZING SPECIFICATIONS AND TESTS 293 amount of iron is ascertained l)y titrating the solution with a standard solution of pota.ssiuni-pernianganate. The lead may be hailed and squeezed with the fingers, and saved if desired. The lead may be weighed and the amount of zinc coating re- moved may be calculated from the weight of the lead, the preferable manner of determining the amount of coating on the sample under test is as follows: Deduct the final Aveight of sample after treat- ment in the lead acetate solution from the original weight of the galvanized piece. Divide tlie net weight of coating so obtained by the weight of the bare or uncoated sample, whence the per cent, of loss in weight is ascertained nearly eiiough for all practical pur- poses. Apply the per cent, loss figure to 2,000 lbs. representing a ton of the articles in question. This will give the pounds of coat- ing per ton of product. Next, ascertain by close measurement or estimation how many sq. ft. of surface there are in a ton of 2,000 lbs. of the articles under examination, reducing the lbs. coating per ton found by the application of the percentage figure, to ounces by multiplying by 16. Having the ounces of coating per ton and tlie numl^er of sq. ft. of surface per ton, divide the former figure by the latter, and find the ounces per sq. ft. ; this is usually a decimal figure. The ounces of coating per sq. ft. gives a unit which may be used for the purpose of comparing the values of coating on different styles and kinds of galvanized product. Samples of galvanized articles which are to be given the lead acetate test must he above all things smoothly galvanized, without adJiering lumps or drops of spelter, since these imperfections would lead to erroneous conclusions by adding to the net weight of coating particles of metal not evenly distributed, wherefore the resultant ounces per sq. ft. would be too high ; it should be carefully observed that all portions of the galvanized article are coated, unless the un- coated areas are left out of the area figure per ton. Caustic Soda Test Prof. Walker has rendered further service to those interested in testing galvanized materials by supplying a test which will show the presence or absence of pores or cracks in zinc coatings. A strong solution of caustic soda in water is heated to a tempera- ture of about 210 degs. Fahr., and the galvanized article suspended in this solution by a string or other non-metallic suspension. If 294 GALVANIZING AND TINNING pin holes or cracks exist in the coating, bubbles or hydrogen will be ol}served to come from the surface of the article at these points, while if there are no pores or cracks in the coating, no action will be observed. The caustic soda test will show whether or not the coating has cracked when the galvanized article is bent after gal- vanizing. In a recent issue of The Iron Age Mr. Samuel Trood has also given special consideration to the use of the various texts from the standpoint of an expert on Sherardizing. The Preece Test The solution is made up by dissolving 36 parts by weight of commercial copper sulphate crystals in 100 parts of water and then neutralizing by the addition of excess of chemically pure cupric oxide. The presence of excess oxide is indicated by the undissolved part settling to the bottom of the vessel. It is difficult and takes much time to get the copper sulphate into solution at room temperature, even if the solution is agitated by blowing air tlirough it, or if the crystals are suspended in a basket near the top of the solution. Heating will greatly accelerate the rate of solution, and in this way a solution can be prepared a little stronger than that desired, the final exact adjustment being after- ward made by diluting with water. To do this accurately and rap- idly, add a certain number of cubic centimeters of water to about 5 liters of solution, and note how many thousandths change this pro- duces in the specific gravity. One or two further additions will then suffice to get an accurate adjustment of the strength. It was noted that, after the finished solution has been filtered olf from the copper oxide, CuO, in the bottom of the stock bottle, there is separated out, sometimes a reddish or sometimes a bulky pale green precipitate, after the solution has stood for a consider- able time, due to some impurity, or it may be to some basic salt of copper. It probably does not affect the strength or neutrality of the solution appreciabty, since the quantity is not great. How- ever, for very accurate work it might be desirable to determine the effect of this change, and whether it is desirable to always use a solution recently filtered off from CuO sediment. The descriptions of the test specify that the strength of the solu- tion shall be 1.186 at 65 deg. Fahr. It would be desirable to know the permissible variation from this, that is, the error due to having GALVANIZING SPECIFICATIONS AND TESTS 20^. the streno-tli 1.181 or 1.188, for example; furtlier, it would simplif}' tlie operation ol' making up the solution, if only an occasional one is made up and means for getting the temperature exactly adjusted are not convenient, to know what specific gravity to aim for if the temperature is 70 deg. or 80 deg. Fahr. After the strength has once been adjusted, the temperature at which the solution is used has an effect upon the accuracy of the test. This will be taken up in an- other paragraph. Manipulation of the Test There does not seem to be published information on the one point that determines whether or not the 023erator will have suc- cess when he attempts to apply the Preece test to Sherardized and alloy-coated articles. This is that the specimen must be brushed instead of wiped, in removing the loose copper after each dip. The copper wliich replaces the zinc on a galvanized coating is in such a loose non-adherent form that it can be easily wiped off with cotton w^aste, but that which forms on Sherardized coatings is more adherent, probably due to the slower rate at which zinc-iron alloy precipitates copper from the solution as compared with zinc itself. FurtJier, the Sherardized surface is rough so that, if the specimen is wiped with waste, the copper, instead of being removed, is rubbed into the hollows of the surface. This copper then protects the still remaining underlying alloy from further action of the solution and the test is .spoiled. The further solution of the protected alloy is retarded so that, if the dips are continued, the specimen will appear to stand more dips than correspond to the thickness of coating present or even may stand an indefinite number of dips. On the other hand, if the operator has not had some experience, he may interpret this premature appearance of copper as a failure, since after several burnishings by waste, the copper on alloy may take a polish that resembles closely the appearance of copper formed on the iron. By removing the cop^Der after each dip by vigorous brush- ing with plenty of water, as under a faucet, the risk of rubbing it into the hollows is practically eliminated. In a Sherardized specimen the portion of the coating next to the iron shows a lighter color during the Preece test than that nearer the surface. For this reason, then, after brushing and dry- ing, a light patch shows up on a darker background, it indicates that the coating is thin at that point and failure is to be expected. 296 GALVANIZING AND TINNING Sometimes, due to imperfect brushing, copper will form on the surface of the coating, as mentioned, but this copper can be dis- tinguished from the copper formed on the iron at the point of failure in several ways. The copper at the failure is lighter in color than that due to improper brushing, it is surrounded by an area of light colored coating and it forms in the hollows or "valleys" of the coating, while the other forms on the higher por- tions or "hill tops." This last difference is always noticeable under a magnifying glass, but it can be distinguished by the eye after a little practice. The regular Preece test was made on some No. 16 gauge wire which had been given a Sherardized coat in such a manner that it was very smooth. It was noticed that the copper which formed could be wiped off with waste and that the test would give the same results whether the wiping was done by waste or by brush. In order to determine whetlier the character of the coat affected this, similar tests were made on Sherardized sheet. One sheet had a rough coat while the other was smooth. Both were dipped at the same time in the same solution and both were wiped with waste. After the fourth dip the copper which had deposited on the rough specimen was rubbed into the crevices of the surface and gave a copperish color to the specimen. Large patches of this copper were burnished to a metallic polish. The copper which had deposited on the smooth piece showed practically no tendency to remain, as there were, few cracks or hollows in which it could form. A specimen of Sherardized sheet "Zy^^i in., with a very thick Sherardized coating, was dipped info a solution 2 inches. One-half of the tested part was brushed after each dip and the other half was wiped with waste. After the third dip line copper began to collect on the wiped half in the crevices of the coat and the amount increased after each dip. The brushed side kept a uniform dark color through the entire test showing no deposition of copper. The copper formed on the wiped half became thicker after each dip. The Sherardized coating where it was not protected by this layer of copper became thinner and eventually failed. The appearance of the coating on the brushed half was uniform and showed no in- dication of failure. The elevated deposit of copper on the wiped half could be flaked off. The premature failure of the wiped half was due to the accelerating action of the heavy elevated deposit of copper; that is to say, the burnished copper on the alloy protects GALVANIZING SPECIFICATIONS AND TESTS 297 only tlie alloy (lii'octly lioiicatli it, l)ut acecloratcs tlic solution of immediately adjoin iiii;- areas of alloy. The elevated copper had a nodular rough surface wliile that deposited on the iron at the failure was smooth and bright. Temperature of the Solution The American Steel & Wire Company specifies that in carrying out the dip test the temperature of the solution must be between 05 and 70 deg. Fahr., while the American Telephone & Telegraph Company specifies 02 to 68 deg. Falir. It is of interest to know the percentage of error due to temperature variations, especially when only an occasional test has to be made, since it may then take much more time to arrange to get the right temperature than to run the tests. Results ol)tained with solution at different temperatures, 75 c.c. of solution being used, are : Average loss, Tempoiature gr. per sq. in. 55 deg. F 0.0291 65 deg. F 0.03185 75 deg. F 0.0345 85 deg. F 0.0397 These figures show that if a specimen is very close to the point of rejection a difference of 10 degrees may easily mean rejection or acceptance for the same actual thickness of coating. Consideration of Objections to Preece Test The accuracy of the Preece test has been called into question by Patrick and Walker (Journal of Industrial and Engineering Chem- istry, April, 1911), for the reason that the rate at which CuSO^ solution dissolves zinc is different from the rate of solution for 7inc-iron alloy. The rate of solution is slower for the zinc-iron alloy because of its lower potential as compared with zinc. But this lower potential would seem to indicate a correspondingly slower corrosion by atmospheric influence, so that the number of dips in a corrosive solution tliat a specimen will stand is a fairer indica- tion of its resistance to corrosion, and tlierefore the usefulness of the coating, than the actual weight of the zinc present. It is a determined fact that less weight of zinc in the form of Sherardized coat will afford protection equal to a greater amount of zinc in the form of a hot or electrogalvanized coating. Determinations have been made of the relative rate of solution 298 GALVANIZING AND TINNING of several kinds of coating in tlie standard CuSO^ solution with the following- results : Loss, gr. per Specimen sq. in. per dip Hot galvanized wire 0.0135 Alloy coated nail (Sherardized) 0.0082 Sherard-jct 0.0109 Gaivaduct 0.0131 It is evident that the Sherardized coat dissolves materially more slowly. In comparing one specimen of hot galvanized material with an- other, there may be a slight discrepancy in the relation between the number of dips and the actual weight of coating. This is due to the fact that in different specimens of hot galvanizing the ratio between alloy and pure zinc present may vary from something like 1 of alloy to 4 of zinc, to 1 of alloy to 10 of zinc. Again, it may be fairly assumed that the important thing to know is the number of dips the specimen will stand rather than the weight of material present. If, however, some buyer or manufacturer should consider weight the only factor of importance, it is evident that a difference of rate, as indicated in the above table, is not so serious when it is borne in mind that it affects only 14 to 1/10 of the coating; further, when the Preece test is used as a regular commercial con- trol by some buyer or manufacturer, the articles compared from day to day are probably usually so made that the variation in the proportion of alloy present is not a maximum one. In the same article, Patrick and Walker assert that the end point is unreliable. x\s far as Sherardized articles are concerned, prac- tically all of this uncertainty as to the end point arises from the fact that the specimen is not brushed properly. The importance of this has been discussed under "Manipulation of the Test." It is true, however, that it takes more practice and more careful dis- crimination to" use the Preece test for Sherardized articles than for hot or electrogalvanized objects. In order to get additional proof that really adherent copper de- posits only upon iron and not upon alloy, specimens were prepared and examined under the microscope. It was noted that the only bright copper oil the brushed specimen was on the iron, Avhile the thin alloy surrounding the place of failure showed none whatever. Be- fore brushing there was copper on this alloy. Sellers of hot galvanized ware have raised objection to permitting GALVANIZING SPECIFICATIONS AND TESTS 299 the brushing- of samples of Sherardized ware, in carrying out the Preece test. As long as there is any coating left the brushing can certainly do notliing that would make the Sherardized article show up better than it should ; if anything it would, remove some of the coating and hasten the failure, to which the sellers of galvanized ware would certainly not object. The only possible contentions of the hot galvanized ware sellers would then be that the brushing might remove copper that is de- posited upon iron. According to observations made on this point, only the most violent brushing will do this and there is not the slightest difficulty in avoiding it. The use of the stiffest brush that could be bought in a local drug store did not bring about the removal of this copper, and a much softer brush is perfectly suffi- cient to give the samples all the brushing they need, if only a burnishing effect is avoided. Probably the only way in which there is danger of removing copper from iron is a bending back and forth or other considerable distortion of the specimen; or, after the coating has been removed and the next dip would deposit copper and iron, to get the specimen dirty or greasy by using a greasy or soapy brush or handling with the hands. If the sample is laid upon a board, in brushing, as may be desirable with light flexible objects, in order not to scale off any copper, the board should of course be free from soap, grease, dirt or chemicals. The Lead Acetate Test In preparing the solution used, difficulty was found in getting the prepared quantity of lead acetate into solution. It is true that by heating this solution would be indicated. One difficulty en- countered in working the test was due to the deposition of adherent lead on Sherardized samples immediately on immersing, particularly those coated by dust. This adherent lead cannot be wiped off and protects the underlying coating from going into solution. The area of adherent lead on some specimens was over 90 per cent, of the total surface. Before the remedy for obviating the formation of adherent lead had been found, it was attempted to determine the loss of weight per dip. Instead of a loss, a gain in weight was found, showing con- clusively that adherent lead was formed. Test pieces consisting of Sherardized nails with the points cut off were used. These were 300 GALVANIZING AND TINNING immersed each time to constant depth. The area of the surface ex- posed was therefore constant in each dip. The nails were cleaned in gasoline, washed and dried; one-minute dips; brushed lightly and dried after each dij). During Nail No. 1, Nail No. 2, dip No. gain in grams gain in grams 1 0.0011 0.0014 2 0.0024 0.0020 3 0.0028 0.0014 4 0.0010 0.0003 A similar nail was dipped into the solution and only adherent lead formed. The nail was removed and a knife blade scraped lightly across the surface and replaced. Loose, Idack crystalline lead immediately formed on the scratched portion, while none formed on the other parts of the nail. Two nails similar to those previously mentioned were dipped in the same manner after they had been l)rushed with a dry brush and wiped with, a dry towel. The deposition of loose lead in this case took place in spots, but covering the lesser part of the surface. These spots grew sloAvly during the dip. The brushing after each dip was done lightly. During Nail No. 1, Nail No. 2, dip No. loss in grams loss in grams 1 0.0008 0.0036 2 0.0018 0.0029 3 0.0017 0.0051 As will 1)0 seen from the next determination, these are not normal results. ^Several other devices were tried to bring about the proper action of the solution. The specimens were thoroughly moistened, a hot solution was tried, the specimens were moved around in the solution, but no results were obtained. In the next test the sample was treated before dipping with about 20 per cent, acetic acid for al)out 20 seconds, or until a distinct evolution of gas took place over its entire surface. After washing and drying it was dipped and weighed as in the previous test. The deposition of loose lead took place over the entire surface im- mediately after immersion. Nail No. 3, During Nail No. 3, Loss grams dip No. Loss in grams per sq. in. 1 0.0201 0.0199 2 0.0163 0.0161 3 0.0138 0.0137 4 0.0141 0.0140 GALVANIZING SPECIFICATIONS AND TESTS 301 A similar test witli a larger nail, dipped in acetic acid before putting into the lead acetate solution, gave the following results: , Nail No. 4 , During Loss grams dip No. Loss in grams per sq. in. 1 0.0120 0.02.35 2 0.0084 0.016.5 ;^ 0.008.') 0.0167 4 0.0002 0.0180 5 0.0089 0.0174 6 0.0086 0.0169 Instead of dilute acetic acid, very dilute hydrochloric acid can also be used, about 10 per cent., and the specimen immersed in this about 10 seconds. It is probable that the reason that the lead acetate solution does not act properly at the start is that there is some zinc or iron oxide on the surface of the object. Patrick and Walker do not approve of a "dip" method of testing the thickness of a coating, no matter Avhat solution is used, but believe that the veight of the coating should be determined, either by weighing the kad deposit or by noting the loss of weight of the specimen. Either of these methods takes more time than that of counting dips, and the method of collecting, drying and weighing the lead seems especially cumbersome for a routine works test. The calculation of the results will take time also, unless there are a great numl^er of samples of the same shape and size to l)e tested. Preece and Acetate Methods Compared 1. For commercial testing the Preece method can be satisfac- torily used for Sherardized as well as for hot dip and electrogalvan- ized articles, if the specimens are brushed properly. It takes more practice to detect the end point for testing Sherardized goods. 2. When used as a dip method the lead acetate test has the ad- vantage of showing the end point with less practice on the part of the operator. It is troublesome for Sherardized articles since the samples must be dipped in acid, as described, in order that the test can be worked. 3. The lead acetate solution removes about 1.6 times as much coating per dip as the copper sulphate solution. It would be de- sirable, in order to prevent confusion, to adjust the solution, if possible, so that a dip removes the same quantity in both cases. If a weaker solution is used in order to reduce the rate of solution 302 GALVANIZING AND TINNING for tlie lead acetate solution there may be more trouble with the formation of adherent lead. 4. As a testing method for scientific investigations to determine the exact weight of coating the lead acetate determination has the advantage that it removes the coating without depositing anything on the iron, resulting in an accurate determination. However the error due to the small amount of copper replacing iron cannot be material if it is desired to use the copper sulphate solution in order to determine the loss of weight of the specimen. 5. The lead acetate method affords a means of determining the percentage of iron in the coating. This is not essential for routine factory testing, and in fact the iron determination would be too troublesome for regular works control. 6. If it does not seem possible or desirable to overcome the ob- jections of the sellers of hot galvanized ware to brushing Sher- ardized samples during the Preece test, the lead acetate method may be a useful substitute or at any rate a good check method to show that l)riishing does not result in too favorable indications for Sherardized goods when tested by the Preece method. 7. It does not seem justifial)le to concur in Patrick and Walk- er's recommendation to substitute a weighing method for the dip method for commercial purposes, or to substitute the lead acetate dip method for the copper sulphate method. Electrolytic Methods Some experimental work was carried on which showed that by removing a Sherardized coating by electrolysis in a solution of potassium nitrate the ampere-minutes of current passed would indi- cate the weight of the coating. At this time the tests were all carried to the point of total removal of the coating. If this method were modified, so that a constant amperage were used, and the specimen removed from the solution from time to time, say every half minute, and the test stopped when failure was first noted, the thickness of coating would be indicated by ampere minutes, which in this case could be readily noted since the am- perage has been kept constant. In order to insure a uniform rate of solution for all parts of the sample, all parts of the specimen should be equally distant from the cathode. If the shape of the object prevents this, the distance should be made great enough, by using a large vessel, so as to make the variations insignificant. GALVANIZING SPECIFICATIONS AND TESTS 303 Care must l)e taken to use a voltage lower than the decomposition voltage of water. As regards the Shcrardizcd coating, the disadvantage of this method would be that the same or greater weight of coating would go into solution per ampere minute as for hot galvanized. As pointed out, this is not the ease with the Preece test. However, the test might at times ))e useful for a laljoratory test for the use of the Northern Chemical Engineering Laboratories, or as a check method, without making any effort to bring about its general adop- tion as a commercial control method. Caustic Soda Test Another test for a zinc coating is the caustic soda test as supplied by Professor Walker. This test will show the presence or absence of pores or cracks in zinc coatings. The galvanized article is sus- jiended by a string or other non-metallic suspension in a strong solution of caustic soda in water, heated to a temperature of 210 dgs. Fahr. If pin holes or cracks exist in the surface, bubbles of hydrogen Avill be observed to come from the surface of the article at these points, while if no pores exist no hydrogen will be evolved. After considering all the possible methods of testing protective coatings, Avhich is the best method for testing Sherardized material ? The best one is that which can be successfully used on a commercial scale by a $13 a week apprentice Government Galvanizing Test In using this test, take distilled water and sulphate of copper, C.P., sufficient to make a saturated solution leaving some sulphate undissolved. Solutions to be used at a temperature of 60 deg Fahr. Test calls for one minute immersion of galvanized work, after which the work is rinsed in cold water and dried, and again immersed in a new testing solution for one minute and again washed and dried out and so on until the requisite number of one-minute dips have l)een made. When the zinc coating breaks down and shows a deposit of bright coppery red the test is finished. A slight appear- ance of copper does not necessarily mean that the zinc; coating is entirely broken down, but, a bright red deposit must show. For some characters of work two one-minute tests are required without the galvanized coating l^reaking down, in others four are required. Professor Burgess, of the University of AVisconsin, who has com- 304 GALVANIZING AND TINNING piled very interesting data, some of which has been quoted, has found that this test is not always suitable for judging the thickness and quality of electro-zincing. For testing the power of resistance of the coating Professor Burgess -has made use of diluted sulphuric acid and has found that an electrically deposited coating one-third the weight of that produced by the hot galvanizing processes has the same power of resistance to corrosion as the latter and that for a coatmg of equal thickness the proportion of resisting power is as 10 :1, ' A table showing the time of deposit, current used in number of amperes and the resistance to successive one-minute immersions as indicated in government test is appended. Amperes used 1 st test 2nd test 2rd test 4tli test per sq. ft. Ve oz. 1/3 oz. 1/2 oz. % oz. surface per sq. ft. per sq. ft. per sq. ft. per sq. ft. Minutes Minutes Minutes Minutes 100 2% 5 7% 10 90 2% 5% 8 11 80 3 6 9 12 70 3% 7 101/3 14 60 4 8 12 16 50 5 10 15 20 45 51/2 11 16% 22 40 6 121/2 19 25 35 7 14 21 28 30 8 I6V2 25 33 25 10 20 30 40 20 121/0 25 37% 50 15 101/2 33 50 66 10 25 50 75 100 Salt Spray Test for Sherardizing Another test which is claimed to be jjarticularly well adapted to making comparisons of the durability of metallic coatings applied by processes of different character is described in a paper read by Mr. J. A. Capp, of tlie General Electric Company, at the seven- teenth annual meeting of the American Society for Testing Ma- terials. There are several processes commercially used for covering the surfaces of metals easily corroded or rusted, such as iron in its several forms, with other metals less easily corroded, or with metallic oxides. These may well be called "metallic" protective coatings in distinction from the types of coating which are in the nature of paints or their equivalent. The object of the application of these metallic protective coatings GALVANIZING SPECIFICATIONS AND TESTS 305 is to enable the coated articles to resist atmospheric exposure with- out rusting for a longer time than they could withstand such ex- posure without protection. Obviously, then^ the only final test of the efficiency of a given type of coating is actual exposure to the same sort of influences that the material is supposed to resist in service. If the coating is at all efficient, this takes so long a time that more rapid methods of determining relative efficiencies be- come a necessity. The most commonly used methods 'of testing such metallic protective coatings are those of chemical attack, which in effect measure either the thickness or the weight per square unit of the protective coating. Such methods of chemical attack permit the comparison of results obtained from tests upon the same sort of coating, but difficulty is encountered when attempt is made to compare the results obtained by such tests on one sort of coating with those obtained on another character of coating. For instance, the well-known Preece test yields excellent comparative results on galvanized coatings. When, however, it is used for coatings ap- plied by the Sherardizing process, the results are not at all com- parable. ISTeither is the Preece test applicable to coatings of tin or of lead. In the case of Sherardized articles, it has been suggested that the coat, Avhich is a combined structure of zinc and zinc oxide, together with some zinc-iron alloy, be removed m strong alkalies which will not attack the iron beneath. This would enable one to determine the weight of coating per unit of surface calculated to metallic zinc, but experience has shown that the results do not necessarily indicate the efficiency of the coat, and that it is not easy to determine the relative proportions of zinc and zinc oxide. Furthermore, comparison of the efficiency of a Sherardized coating with ordinary galvanizing is not possible when the Sherardized coating is tested by solution in a caustic alkali, while the galvanized coating is subjected to the Preece test. Some years ago, when testing electrical insulation such as is used for overhead line construction, we found that material which stood fairly well when immersed in water failed badly when ex- posed to the weather, especially if exposed during a hard rain. This led us to produce a rain in the laboratory by sending a stream of water through an ordinary rosette such as is used with a garden- er's watering can. The results were encouraging, but too severe, because the individual streams played steadily on one spot and produced erosion. Then we tried an atomizing nozzle, projecting 306 GALVANIZING AND TINNING a cloud of moisture into a chamber in which the test specimens were exposed; the results were better, but there was still a possibility of some wear if the article was directly in the path of the stream and near to the nozzle. The problem seemed to be solved when care was taken in placing the articles to keep them out of the direct path of the jet issuing from the atomizing nozzle. As ex- perience was gained with this type of test, as applied to insulating material, it was found that what seemed to be the essential re- quirement was the maintaining of an atmosphere substantially saturated with moisture; and this saturated-atmosphere exposure has been one of the tests regularly applied to all insulating ma- terials intended for outdoor use since it was first worked out some fifteen years ago. It has been found to give reliable indications of the alulity of insulation to resist weather, except, of course, as such ability is afl'ected by extremes of heat and cold, erosion from the wind carrying dust particles, etc. The problem of determining the resistance of protective coatings to weather corrosion is very similar to that of testing insulations for their weathering qualities. The conditions of exposure are the same, and hence there seemed to be no essential reason why the saturated-atmosphere test would not apply equally well to pro- tective coatings as to insulation. Tests were begun several years ago to try out the method, and the only fault found with it was th.at it was somewhat slow. Good coatings did not show any signs of breaking down after several weeks of continuous exposure to the fog; yet there was encouragement in the fact that bare metal l^egan rusting in a few hours, and rust spots began developing on poorly protected surfaces in from a few days to a week. The fact that more troul^le is experienced with trolley-line sus- pensions along the seashore than with the same devices inland, led immediately to the trial of an atmosphere saturated with salt water, . with astonishingly satisfactory results. As* now used, the test consists in exposing the Sherardized ar- ticles in a copper-lined box, such as is illustrated in Figs. 133 and 134, into which there is projected by compressed air an atomized spray of 2| per cent, solution of NaCl in water. Care is taken to avoid placing the test specimens directly in the path of the jet. To insure constant saturation, an excess of salt is kept in the water at the bottom of the chamber. The spray is produced by a jet of compressed air lifting the water to the nozzle, whence it is pro- CALVANIZING SPECIFICATIONS AND TESTS 307 joeted as a cIoikI. Tliis apparatus is of tlio comnioii atomizer typo. The ehaiuber is necessarily not tightly sealed, but is open sudieiently to permit "breathing"; when used with an air jet, there is a slight pressure which is relieved through the Ijreathing openings. If desired, the test may be modified by the use of a line steam jet to raise the temperature of the atmosphere in the c-hamber. The specific gravity of the water is kept at 1.036 and 1.03 at 60 deg. F. There is also the possibility of render- ing the test atmosphere slightly acid or alkaline by suitable addi- tions to the Avater in substitution for the salt. For use with plain water, the closet generally used for cement testing does very well, provided care is taken that it is so arranged as to maintain the air practically at 100 per cent, relative humidity. When using salt solutions, recourse must be had to the atomizing jet to insure the development of the salt fog. OuncBs per Square Foot of Surface 33 CO <3 tc! CD I \ \ \ ' rv) Chl L lips Prd ece Tesi 03 Cu. CO SCk <5 ^ K5 ^ \ \ V \ V^ v^ ^, ^ ^^ L^ ■J. ^ ^>. "Sr ^ ^c i^n s ^ k ■TO V. "^ j^i^j ^ ^ >r^- ^ v^ .^__ ' (^ ^ ^. V" ^ ^ter/or of 60* arid cOk'ers copper /tried ana a// jo/r}ts ^o/dsred Coirer removed Airpipe Spray Atoiz/e 36' «-1 Fig. 134. Details of Construction of Salt Spray Testing Box The method of making the test is very similar to that outlined for galvanized sheets, except that the wire is first cleaned with carbon tetrachloride or gasoline, and after being carefully weighed is placed in a tall glass cylinder containing hydrochloric acid (sp. gr. 1.20), to which has been added from 2 to 3 c.c. of antimony- (^hloride solution of the same strength as used on galvanized sheets. The reason for using one-half the amount of antimony chloride 312 GALVANIZING AND TINNING in the case of wire is on account of taking one-half the area. As previously stated, the coating on galvanized sheets is expressed in ounces per square foot, considering one side only, when in reality this amount of coating represents 2 sq. ft. of surface. After im- mersing the entire length of wire for 1 min. it will be found con- venient to pour the acid solution into another tall cylinder in order to facilitate removing the wire. The wire is then scrubbed under running water, wiped, thoroughly dried in a warm place for a few seconds and again weighed. Each gram lost corresponds to 1 oz. of coating per square foot. For direct comparison with the weight of coating as expressed on galvanized sheets, this figure should be doubled. INDEX Acetate, Sodium, in Elec.-Galv. solution 221 Acid consumption in pickling.. 46 Hydrofluoric 43 Hydrofluoric pickle 212 in porous castings effect in Sher 279 Muriatic 43 Muriatic, pickle 211 Nitric, pickle 211 Preventing waste of 280 Sulphuric in Elec.-Galv. solu- Sulphuric in Elec.-Galv. solu- tion 219. 220, 221 Sulphuric, pickle 211 tanks, Construction of 30 Tartaric, in Elec.-Galv. t-olu- tion 22J Action of gas in metal. 229 Agents for improving Elec.- Galv. solutions 22>i Agitatioa of solution Elec.- Galv 153 Air pressure in Schoop process 102 trapped in tubes, Prevention of 194 Alcohoi, Its effect on Elec.-Galv. bath 222 Alum, Effect on Elec.-Galv. bath 222 Aluminum 43 Chloride, Sodium in Elec.- Galv. solution 221 coating by Schoop process.. .. 96 improves appearance of work 43 Sulphate of, in Elec.-Galv. solution 218, 220, 221, 222 Ammonia absorbed by charcoal 229 Ammonium chloride in Elec.- Galv. solution 218, 219, 220, 221 chloride, Zinc, Substitute for sal ammoniac 42 Amperage for Elec.-Galv. 1.53, 218, 219 required under different con- ditions 207 Analysis of zinc dust 274 Anchors, Ashler Hot Galvanized 11 cleaned by sand blast 59 Angles,. Casting's with sharp angles, require special pre- paration 133 Annealing' action in Sher. furnace 277 Anodes 149, 189, 199, 203, 222 Automatic removal of 164 Choice of 207 Cleaning scum from 164 Special shapes for depi-es- sions 223 Wrapping, to galv. inside of tubes without contact 193 Antimony chloride and hydro- chloric acid test 308 Apperance of work improved by aluminum 43 Applying zinc coating by Elec- Galv. process 222 Ash can for zinc dust 233 cans. Temp, for Hot Galv. of 68 pit - 17, 25 Ashler anchors, Hot Galv 11 Ashes, Zinc, How formed 90 Asphalt lined tanks 208 Asphaltum, Use of, in tank con- struction 31 B Band iron. Formula for Elec.- Galv. of 218 Schulte machine for Elec.- Galv 204 Bars for Potthoff machine, Elec.-Galv 191 Barrel, Dry tumbling, Loading of 52 Unit for Elec.-Galv. a modi- fied form 181 Unit for Elec.-Galv., Opera- tion 181 Barrels, Elec.-Galv. Cleaning, rinsing and plating unit 177 Daniel's hand and lever 165 Ele-Kem automatic 174 Potthcff's automatic 168 Schulte's mechancial 172 Unloading automatically..l68-173 Barrels, Sand blast Details of construction 63 Operation of 61 Barrels, Tumbling Charging of 54, 213 Construction of 53 Detailed plan of 53 314 INDEX Barrels, Tumbling Elevation of 53 Loading of 54 Basins Catch under acid and water tanks 15 Baskets .-31, 118 for tinning small articles, Construction of 118 Bath, Hot alkali, for cleaning gray iron castings for tinning 135 showing acid reaction the best217 Baths, Cleaning and pickling..210 Bayliss process for Hot Galv- sheets - 76 Beams, Steel grillage, Hot Galv -- 10 Benzoic acid, its effect on Elec- Galv. bath 222 Black pickling 46 spots, Eliminating, from fin- ished work - - 279 spots on Sher. articles, Cause of 279 Blue dust. Advantages of 257 Metallic content 267 Takes longer to cool 257 "Blue powder" — zinc dust.... 256 Boiling out kettles. Tools for 93 "Boiling" the tin in re-tinn- ing 127 Bolts, Allowance for thickness of coating in Sher 268 Equipment for Sherardizing 233 Boric acid in Elec.-Galv. solu- tion 218, 219, 220 Box, Testing, for salt spray 309, 311 Boyles and Charles, Law of.... 229 Bricking in a small galv. kettle 20 Brickwork on galvanizing kettle without grates and having one draft hole 26 Bronze, Depositing on Sher. articles 282 Brushing, Objection to, in test- ing Sher 298 Scratch - 211 surplus zinc from article.... 70 Buffing Sher. articles 282 Burnishing barrel, Ele-Kem.... 175 Sher. articles 282 By-products of Hot Galv. pro- cess .-• - 84 ©f Hot Galv. process, Ke- covery 85 C Cable or chain conveyer ma- chine, Fleischer's 161 strip, armored, Test for thickness of zinc coating.. 226 Car, Transfer, Construction of 253 Cartridge steel, Elec.-Galv. of 194 Casing for draft holes 24 Castings, Avoid sharp angles 133 Cast-iron, Preparing for tum- bling 54 Cleaning 210 Drying, Arrangement for.... 26 Elec.-Galv. solution for 219 for grate fired Galv. kettle.. 23 for small Galv. kettle 21, 22 for tinning kettle 116 Gray iron, Cleaning with hot alkali bath 135 Gray iron, Heat required in tinning — 142 Gray iron, Preparing for tin- ning 133 Gray iron, Eemoving sand from 133 Gray iron, Removing sand with hydrofluoric acid 134 Gray iron. Time required to tin 141 Gray iron. Tinned for electro plating 136 Gray iron, Tinning of 129 Handling delicate ones in roll- ing barrel 57 Malleable and gray iron, Pickling of 263 Method of immersing in roughing kettle 140 Over-pickled, Remedy for ....135 Sandy, Cleaning with hydro- fluoric acid 113 Sandy, Cleaning with sul- phuric acid 49, 112 Sandy gray iron. Cleaning with sand blast 135 Sandy gray iron. Cleaning with sulphuric acid for tin- ning 135 Solution for finishing when work is not thoroughly cleaned 55 Storing after tumbling 57 Testing to see if they are properly cleaned 55 Time required to clean in tumbling barrel and sand blast 55, 59 Time and speed required to clean in tumbling barrel 55 Cast iron, Preparing for tin- ning 54, 133 Catch basins under acid and water tanks 15 Caustic-soda solution 210 Caustic-soda test 293, 303 Ceiling, High, for plants 14 INDEX 315 Cement floor, Advantage of 233 Chain or cable conveyer ma- chine, Fleischer's 161 conveyer machine, Miller's, Construction of 153 conveyer machine, Miller's .. 156 Equipment for Sherarclizing 233 Grips, Removing scale from 211 Cleaning, in dry tumbling barrel 53 Chamber pails, Temp, for Hot Galv. of 68 Charcoal, Absorption of am- monia 229 Charging of tumbling barrel 54, 213 Charles and Boyles, Law of.— 229 Chart, Deposit and temp, in Sher 270 Chilled shot used instead of sand in sand blasting 64 Chimney construction for Hot Galv. plant 17 Chloride, Ammonium, in Elec- Galv. solution, 218, 219, 220, 221 of ammonia in Elec.-Galv. solution 218, 219, 220, 221 Sodium, Aluminum in Elec.- Galv. solution 221 of zinc in Elec.-Galv. solu- tion 218, 219, 220, 221 Cinder test for Galv. coating 225 Citrate, Sodium, in Elec. Galv. solution 221 Cleaning barrel 51, 174, 177 castings with sulphuric or hydrofluoric acid 49 Electro 215 equipment 149 most essential step in Sher- ardizing 232 old galvanized work 146 old tinned work 146 Potash solution for 196 Einsing and plating units, 168, 172, 177 Rinsing and plating barrel unit, A modified form 182 scum from anodes 164 Sher, articles 280 Spec, for ; 287 Tanks 208 work for Elec.-Galv 209 Cloth, Wire, Formula for Elec.- Galv. of 218 King's machine for Elec.- Galv 194 Root's machine for Elec.- Galv 202 Coal hods. Temp for Hot Galv. 68 Time required to Hot Galv. 70 Coal, Pea, Cost of, in Sher. one ton 285 Coating, Spelter of Sheets, Determining 310 Zinc, Applying in Elec.-Galv. Process 222 Zinc, Locating cracks in 294 Zinc, Non-uniformity in Sher. Remedy for 279 Coke 43 Burning, Sher. furnaces 234-240 Cost of in Sher., one ton.... 285 Dust, Use of, in Hot Galv. wire, etc 77 Foundry unsatisfactory 43 Gas gives best results 43 Cold or Elec.-Galv 148, 226 Colloids 222 Coloring and finishing Sher. articles - 282 Combination formula for clean- ing and plating 216 Combustion chambers in gas and oil burning furnaces 241 in Goke burning Sher. fur- nace 234 in Sher. furnace 238 Conductors, Copper 149 Rule for figuring size of 207 Construction of three drum coke burning Sher. furnace 234 Cooling and unloading drums 276 Drums 271 Frame 233, 255 Hot Galv. work 70 Out 276 platform .....247, 248 Rapid, Eifect of 275 Slow, better than fast in Sher 273 Coping plates 25 Copper acid solution 225 Bath 198 Cyanide bath 225 Cyanide bath, action of 212 Cyanide strike 211 Depositing, on Sher. article 282 Dip. Formula for 212 Flashing 211 Sulphate or Preece test 290, 294, 301 Correct position of pyrometer in kettle 35 Corrosion of iron and steel. Prevention of 9 Theory of 11 Corset steel Elec.-Galv. of, 194, 225 Cost of Elec- and Hot Galv.. 224 of coating with zinc by Schoop process 102 316 INDEX Cost of coke in Sher. one ton 285 of elec. current 224 of Elec.-Galv 208, 224 of illuminating gas in Sher.. 285 of metal spraying with "pis- tol" 105 of oil 284 of producer gas in Sher. one ton 285 of production (all processes) 72 of Sher. per ton 284 of zinc dust 284 Cowper-Cowles Sherard, In- ventor of Sherardizing pro- cess 227 Cracks, Locating in zinc coating294 Cyanide, Copper bath 225 fumes. Removal of 150 Cyclone metal spraying device. Operation of 98 D Dairy utensils, Coating, by Schoop process 104 Daniel's Elec.-Galv. barrel 165 Screw conveyer machine 158 Davies' method of Galv. sheets 74 Defective coating frequently due to poor cleaning 209 Density of Elec.-Galv. solutions 219 Deposit, Heavy in Sher 275 Deposition, Double 223 Dextrine in Elec.-Galv. solu- tion 220 Effect of, on Elec.-Galv. bath 222 Dip, Formula for copper 212 Dipping gray iron castings in tin 138 in molten zinc. Time requir- ed 69 Preparing cleaned work for 64 work in molten zinc 69 Dont's in Sher. practice 278 Double deposition 223 Drainage of Hot Galv. plant 15 of tinning plant 109, 130 Drier, Front section of 27 grate and firebox. Detail of 30 Operation of 65 Placing work in it to keep hot without burning acid off.... 65 Plan and details of construc- tion 28 Plan and elevation of 29 Plates covering fires will do for small lots of work.... 65 Proper location of 65 Dross, Hard zinc 84 Kept from coming in direct contact with bottom of kettle by 6 or 8 in. layer of lead 66 on re-tinned article, Method of preventing 125 Remelting 145 Removal of, from tinning kettle 141 scoop. Construction of 33 Storage of 145 Value of 145 Zinc, How formed 85 Zinc, Method of recovering.. 85 Zinc, sweating. Temperature and operation 88 Drums, Cooling 271 Cooling and unloading 276 Loading 261, 263, 266 Loading into furnace 254 Rotation of, in Sher. furnace 237, 267, 273 Sherardizing 233, 250, 251 Sherardizing, Construction of250 Sher. Cylinder, fastening heads on 251 Sher., Square 250 Dry Galv. or Sherardizing 227-286 tumbling 52, 209 Tumbling of wire work 213 Drying apparatus 27, 65, 200 Barrel Ele-Kem 176 Castings, Arrangement for.. 26 Hot Galv. work 71 plate 17 work after tumbling and sand blasting 65 of heats in Sher 267 Duration of Elec.-Galv 225 Dust screening machine 233, 251, 276 Dynamo 206 E "Edis Compound," A substitute for sulphuric acid in dry cakes 48 Egg beaters, Tinning of 129 Electric current. Chart for Sher - 271 Hoist for Sherardizing plant 234 Electrical condition accompany- ing evolution of gases 230 equipment 206 installation 150 Electrically heated Sher. fur- nace 248 Electro-cleaner, Action of 212 Electro-cleaning 215 Cleaning solution 211 Elec.-Galv., Advantages of.... 148 Barrel Unit with Cleaning and Rinsing tanks 177 INDEX 317 Elec.-Galv. Apparatus Daniel's Screw conveyer 158 Fleischer's Cable or Chain Conveyer 161 Hanson & Van Winkle's Pipe and Tube 189 King-'s Continuous Wire Cloth 194 Meaker Continuous type 184 Miller's Chain Conveyer 153 Potthoflf's Tube 191 Eoot's Wire Cloth 202 Schulte's Wire 204 Elec.-Galv. Barrels Cleaning, rinsing and plat- ing unit 177-182 Daniel's hand and lever 165 Ele-Kem automatic 174 Potthoff' s automatic 168 Schulte's mechanical 172 Elec.-Galv. or cold process. .148-22G Cost of 208, 224 Duration of 225 Earliest record of 148 Heavy deposit 223 Elec.-Galv of corset steels 225 Open tank work 153-165 Plant, Layout of 150 Plant, Eemoving fumes 150 Preparing work for 209 Solution for castings 219 Solution for soft deposit 220 Solution for testing 287 Solutions 217-222 Solutions, Agents for improv- ing 222 Solutions for barrel plating 219 Spongy deposit 223 Tests, Table of 304 Time required, 218, 219, 222, 223 vs. Hot Galv. comparative costs 224 Electro plating. Gray iron cast- ings tinned for 136 Electrolytic test 302 Elec.-Galv. barrel saw-toothed construction 174 Elevation of re-tinning plant containing four kettles.... 122 "Embalming," or protecting iron from rust 9 Emery, Use of in tumbling.... 218 Epsom salts in Elec.-Galv. bath 220 Equipment and plant for Hot Galvanizing 14, 17 Electrical 206 for Elec.-Galv. plant 149 and location of Sher. plant 233 Erlenmeyer flask. Use of 258 Exhaust for dust screener 252 F Fats will redeposit in Sher 281 Filling a new kettle 66 Finishing and coloring Sher. articles 282 of re-tinned work 127 Firing a new kettle 67 Flaking, Cause of in Sher 281 Flashing Copper 211 Flat stock. Loading in Sher. drum 265 Fleischer's Cable or Chain con- veyer Machine 161 Floor Cement, Advantage of 233 Floor space required for Sher. plant of one ton capacity 233 Flues, Arrangement of 28 Underground 17 Flux boxes on Hot Galv. Ma- chines 74 Exercise care in removing.... 89 formed by sal ammoniac 42 for tinning kettle in coating cast iron 139 "Flux guard" 70 in kettle 73 prevents zinc from oxidizing 69 Thick or lumpy, To remedy 139 Food choppers, Time required for sand blasting 59 Forgings, Pickling 48 Formula for cleaning and plat- ing 216 for copper dip 212 for Elec.-Galv. solutions .... 218 Foundation washer, Cast iron 25 Frames, Cooling 233, 255 Loading 233 Fuel for tinning 107 Proper depth in firebox 67 Fumes 217 carried off by exhaust sys- tem 150 a menace to machinei-y 14 Furnace, Gas, single drum 240 Sherardizing 233 Sher. Coke burning, Elev. and details of single drum 238 Sher. Coke burning, Elev. and details of three drum 235 Sher. electrically heated 248 Sher. Elec. heated, Opera- tion of 271 Sher. for long job work 244 Sher. Gas and oil burning 239, 248 Sher., Loading drums into 254 G Galvanic action taken up by zinc , 12 318 INDEX Galvanized work, old, Cleaning of 146 Galvanizing, kettles allowed to cool off not economical 13 Sheets, Construction of ma- chines for 74, 75 Sheets, Heathfield method.... 75 Sheets, Three process de- scribed 12 Specifications 287 Test, Government 303 Gas, Action of, in metals 229 Gas and oil burning Sher. fur- naces 239-243 Bubbles in Elec.-Galv. Pre- vention of 203 Contents of metals 228 Illuminating, Cost of, in Sher 285 Pressure of in Schoop pistol 101 Producer, Cost of in Sher.... 285 Gelatine, Use of in Elec.-Galv 222 Generator, Location of 207 Low voltage 149 Girders, Coating by Schoop process 104 Glucose, Effect on Elec.-Galv. bath 222 Glue, Effect on Elec.-Galv. bath 222 Glycerine 43 Action of, in kettle 69 in Elec.-Galv. solution 220 Use of in making flux foam up 70 Grape sugar in Elec.-Galv. solu- tion 218, 221 Grasselli dust 256 Dust, Advantages of 257 Dust, Metallic content „... 267 Grate and firebox for drier. De- tails of 30 and firebox for tinning kettle 131 bars, Method of setting in tinning kettle 116 fired galvanizing kettle, De- tails of construction 23 Grates 24, 25 Gray iron and malleable cast- ings. Pickling of 263 iron castings, Preparing for tinning 133 iron castings, Proper tem- perature for Hot Galvan- izing 68 iron castings, Removing sand from 133 iron castings. Removing sand with hydrofluoric acid. 134 Grease or oil. Removal of........ 210 ' Grease or oil, Removal of from stamped ware 122 Removing from work to be tinned 114 Grillage beams, steel, Hot Galv 10 Grinding and scouring machine 213 Grit, Diamond, Advantage of 64 LTse of in wet tumbling 213 used instead of sand in sand blasting 64 Gum tragacanth in Elec.-Galv. solution 221 H Handling pickled work 48 Hanson & Van Winkle Pipe and Tube Galv. Machine.. 189 Hardware Saddlery, Time re- quired to clean by sand blast 59 Saddlery, Tinning of 109 Testing samples 288 Heathfield's method for Galv. sheets 75 Heathfield Process, Zinc de- posited on sheets by 76 Heat Controlling in Sher. fur- nace 238 Heating kettles 147 Heats, Duration of in Sher.... 267 Heavy deposit in Elec.-Galv. process 223 Hoist, Electric 280 Electric, for Sherardizing plant 234 Hood, Exhaust, for dust sep- arating machine 252 Hoods for kettles and tanks, size of 15 for kettles. Movable 14 Hoop iron, Elec.-Galv. of 194 Hot Galv. automatically 74, 76, 77 Dipping the work 69 Equipment 17 Laws of physics applying to 18 Plant and equipment 14 Plant, Floor plan of 15, 16 Plant, small 17 Plant, steam required 15 Plant, Ventilation of 14 Plants, Drainage of 15 Room fittings 14 Solution for testing 287 Tools, Construction of 32 Tools for 31 Work, Cooling after dipping 70 Hot rolled steel. Cleaning 209 Hydrochloric acid and antimony test 308 INDEX 319 Hydrofluoric acid 43 best for removing sand from gray iron castings 134 Cleaning sandy castings with 113 Pickle 212 Pickle, Test of 263 Tanks for 16 Use of in cleaning castings 49 Hydrogen absorbed by pladium 229 Hydrogen gas causes damage 80 Remedying damage caused by 80 I Ice cream freezers, Tinning of 129 Impurities lower melting point 36 Inspection of material before Sher 279 Ions, Free, Effect on precipit- ation of vapor 230 Iron and steel, Comparative value for making Galv. kettles - 20 Corrosion, Prevention of 9 Iron Band, Elec.-Galv. of 204 Formula for Elec.-Galv. of 218 Iron, Cast, Preparing for tin- ning 54, 133 Iron, Determining amount of in Galv. coating 292 Malleable and gray, Pickling of 263 Proper grade for making Hot Galv. kettles 18 Sulphate in Elec.Galv. Solu- tion 221 Wrought and steel, soluble value of 18 Zinc Alloy 227 Japanning, Sher. articles 282 K Kettles, boiling out, Tools for 93 Burst by allowing them to cool with quantity of zinc dross in them 86 Filling new 66 for molten zinc 16 for recovering zinc dross. Construction of 87 for refinishing old galvanized and tinned work 147 for retinning 121 for tinning 109 for tinning gray iron cast- ings. Arrangement of grate bars and ash pits 131 for tinning gray iron cast- tings, Elevation of— 131 Kettles for tinning gray iron castings. Size and shape 144 for tinning spoons, etc., Size of 119 for tinning wire 119 Galvanizing, allowed to cool off not economical 13 Galvanizing, Bricking in 20 Galvanizing, Castings for.... 21 Galvanizing, grate fired, cast- ings for 23 Galvanizing, grate fired. Con- struction of 23 Galvanizing, grate, fired, plan and elevation 22 Galvanizing, One piece 25 Galvanizing, Selection of 20 Galvanizing, Setting small, without ash pit 20 Galvanizing without grates, one drafthole, Plan and elevations 26 Galvanizing, Heating sides and bottoms of 147 Galvanizing, Leaks in new or old 92 Galvanizing, Life of 92 Galvanizing Listing, Use of 126 Galvanizing, New, Firing .... 67 Galvanizing, New often ruined by improper filling 66 Galvanizing, New, Packing slabs of spelter in 6Q Galvanizing, Preparing, be- fore starting to dip 69 Galvanizing, Replacing old.. 92 Re-tinning, Replacing 128 Roughing 140 Galvanizing, Selection of best material for making 18 "Skinning" for removing sur- plus tin in re-tinning 127 Soaking 121 Tinning, Castings for. 116 Tinning, Materials used in constructing 144 Tinning, Plan and elevation of 115 King Continuous Wire Cloth Machine 194 "Kleanrite," a substitute for sulphuric acid in powdered form 48 Labor cost in Sher 284 in Sher. Improving 280 Skilled more reliable than py- rometer on miscellaneous work 34 i 320 INDEX Labor, Unskilled expensive in Hot Galv 13 Lacquer finish on Sher. articles 283 Laundry machinery, Coating by Schoop process 104 Law of Boyles and Charles 229 Lead Acetate and Preece Tests Compared 301 Lead acetate test 291, 299 acetate Test, Advantages of 301 Lead as cushion for dross 66 lined tank 208 lining in Tanks 31 not electro positive 12 Pig 42 Leaking prevented in articles by tinning before plating 129 Leaks in kettles, Repairing.... 92 Licorice, Its effect on Elec- Galv. bath 222 Lime solution to neutralize acid 262 Lining tanks with sheet lead.. 31 Listing kettle. Use of 126 Loading drums 261, 263, 266 Frame 233 Platform 246 wet tumbling barrel 54 Location and equipment of Sher. plant 233 M Machinery Used in Hot Galv., Composition of 18 Magnetic oxide. Removal of from bath 210 Malleable iron castings. Tem- perature for Hot Galv.... 68 iron casting. Tinning of 106 Materials used in Hot Galv.... 41 used in Sher. 256 Vapor tension of 230 Mealcer Continuous Machine, Operation of 188 Continuous Type Elec.-Galv. Machine 184 Mechancial Elec.-Galv. appar- atus 153 "Melting out" 67 Melting point lowered by im- purities 36 Melting point of zinc 35 Metal, Action of gas in 229 Powdered, Use of in metal spraying 96 Metallic method of rust preven- tion 9 Metallic zinc in zinc dust. Meth- ods for determining 258 Metals are extremely porous 229 Gas contents of 228 Metals, Spraying, Position of apparatus in applying coat- ing 103 Spray Process, Schoop 94 Methods of producing zinc vapor 230 Miller Chain Conveyer Ma- chine, Construction of 153 Chain Conveyer Machine, Op- eration of 156 Mill scale. Removal of 210 Moist air test 226 Molasses, Its effect on Elec.- Galv. bath 222 Morf patent for spraying pistol 95 Motion during Sher 273 Muriatic acid 43 A "safe" pickle 49 Dip for a flux 64 Formula for a quick pickle 50 Mixture for cleaning castings in tumbling barrel 55 Pickle 211 Removing scale or rust with 48, 113 N Nails, Equipment for Sher 233 Sher. test of 298 Temperature for Hot Galv. of 68 "Nesting" of articles prevented 122 Netting, Wire, Hot Galv. of.. 77 Nickel solution 225 Nitric acid pickle 211 Non-metallic method of rust prevention 9 Nuts, Testing coating of 289 O Oil 43 and gas burning Sher. fur- naces 239, 248 Fuel, Cost of in Sher 284 Mineral lard, best 43 or Grease, Removal of 210 Removing in Sher 281 Old work quickly cleaned by sand blast 59 One piece galvanizing kettle.. 25 Open tank Elec.-Galv 153, 165 Operating costs in Elec.-Galv. 224 Operation of chain conveyer plating machine 156 of elec. heated Sher. furnace 271 of Meaker continuous type Elec.-Galv. machine 188 of King's wire cloth machine 196 of plating barrel unit 181 of screw conveyer plating machine 160 INDEX 321 Overheatinj? destroys kettle 37 in tinning?, Effect of 144 Over pickling 45, 47, 212 Remedy for 135 Oxide, Magnetic Removal of from bath 210 of Zinc, Value of in Sher.... 231 Oxygen absorbed by spongy platinum 229 P Packing Elec. heated Sher. fur- nace 266 Paint, Old, Removal of by tum- bling 53 Removing from w^ork to be tinned 114 Paints, Non-corrosive 10 Paladium Hydrogen absorbed by 229 Palm oil used vv^ith beef tallow gives good results 142 Parson's patent for Elec.-Galv. 148 Patents covering Schoop pro- cess 95 Phvsics, Laws of, as applied to ■ Hot Galv 18 Pickle, Hot better than cold.. 210 Hydrofluoric acid 212, 263 Muriatic acid, A "safe" 49 Nitric acid 211 "Quick," Formula for 50 Sulphuric acid. Test of 262 Time required 210 Pickled work. Handling 48 Pickling 44 Acid, Consumption in 46 Best mechanical method 46 Black 46 Cold better than hot 50 Foundry 49 Fumes, Effect of in Sher.... 278 machine, Automatic 45 malleable and gray iron cast- ings 263 Mechanical 44 Over 45-47 Over, Remedy for 135 Securing uniform action with acids 44 Sheets .....44-46, 111 Solutions, Length of time they may be used satis- factorily 50 Solutions, Temp, of 262 Steel 261 Tanks 233 Temperature in using Hy- drofluoric acid 49 Under 45 White 46 Wrought iron and steel 48 Pin Holes filled by Schoop pro- cess 104 Pipe and tube Galv. machine, Hanson and Van Winkle.. 189 Cleaning conduit with sand blast 213 Water Furnace for Sher 248 Pipes, Galvanized 11 Pistol, Distance it should be held from work in spraying 103 for metal spraying, construc- tion details 99 for metal spraying, Opera- tion of 101 for Schoop Metal Spray Pro- cess 98 Table of operating costs for one hr. 105 Pitch lined tanks 208 Plans for Hot. Galv. plant.. 15, 16 Plans of Elec.-Galv. plant 150 of small galvanizing kettle.. 21 showing brickwork of galvan- izing kettle 22 Plant, Elec.-Galv 150 and equipment for Elec.- Galv 149 and equipment for Hot Galv. 14 and equipment for tinning.. 106 and equipment for tinning gray iron 129 Plate Drying 17 Plates 24 Coping 25 Platform Cooling 247, 248 Loading 246, 248 Plating and cleaning in combin- ation 216 Platinum, Spongy, Oxygen ab- sorbed by 229 Porous condition of metals 229 Porter machine for removing surplus zinc 71 Position and location of pickl- ing and cleaning tanks 233 Potash solution for Elec.-Galv. 196 Potthoff's Elec.-Galv. barrel.... 168 Potthoff Tube Galv. Machine.. 191 Powdered metals, Use of in metal spraying 96 Precipitation of Vapor, How it occurs on metal 229 Preece Test 290, 294 Test, Limitations of 291 Test, Objections to 297 Test, Operation of 290, 294 and lead acetate tests com- pared 301 Preparing cleaned work for dipping in hot zinc 64 322 INDEX Preparing gray iron castings for tinning 133 material for Sher 261 work for Elec.Galv 209 Prevention of corrosion 9 Producer gas, Cost of in Sher. 285 Protecting pyrometer from action of molten zinc 34 Protection of iron from rust.... 9 Pumice stone, Use of in clean- ing work 214 Pure water test for Galv. coat- ing 225 Pyrogallol, Its effect on Elec.- Galv. bath 222 Pyrometer 233, 255 important as temperature regulator 35 in proper position 35 of advantage on sheets, wire and other straight work.. 34 Protecting stem from action of zinc 34 Selecting a reliable one im- portant 37 Stupakoff's paper on 35 Use of in Hot Galv. kettle.. 34 R Rack for re-tinning small articles 124 Re-charging tumbling barrel- 55 Reducing agents for Elec.-Galv. solutions 222 Refinishing old galvanized and tinned work 146 Regulation of zinc deposit 223 of zinc deposit in Elec.-Galv. 223 Remelt spelter vs. Prime western Calorific value of 68 Removing oil or grease 210 sand from casting 210 Re-tinned work. Finishing 127 Re-tinning kettles, Replacing.. 128 Method of handling work 125 plant and equipment — . 121 plant containing four kettles. Elevation of 122 plant with four kettles, Plan of 123 Rack to prevent "nesting" of small articles 124 stamped ware 121 Rheostat, Adjustment of 161 Rolling barrel for tinning gray iron castings _- 129 improves appearance of tin coating 112 water. Removing scale by 51, 113, 136 Wet and dry 51, 213 Root Wir^ Cloth Machine 202 Rotation of drums in Sher. 237, 267, 273 Roughing — ..' 119 Rust preventative. Zinc, best.. 11 prevention. Metallic method 9 prevention. Non-metallic me- thod_ 9 Removing 16 Removing from castings with sulphuric acid Ill S Saddlery, hardware, Tinning of 109 Sal ammoniac 42 Action of, in kettle 69 Dip for a flux 65 Gray granulated forms flux 42 in Elec.-Galv. solution....221, 222 mixture for cleaning castings in tumbling barrel 55 Skimmings 84 Skimmings, Method of recov- ering 90 Skimmings often shipped in bulk 90 Skimmings, Storage of 89 Saline or salt spray test.. ..225, 304 Salts, Epsom in Elec.-Galv. solution 220 Spray test 225, 304 Spray testing box, Details of 311 Samples for testing... .288, 292, 309 Sand, Condition of, for sand blasting 64 Removing from castings 210 Removing from gray iron castings 133 Removing from gray iron castings for tinning 135 Sand blast barrel, Details of construction 63 barrel. Operation of 61 Rolling barrel 61 Use of makes tinning of castings simple 58 valuable in cleaning sandy gray iron castings 135 Sand Blasting 58, 135, 213, 261 Air pressures required 60 and tumbling 51-65, 213 Apparatus, Operation of 59 Food choppers, Time requir- ed for 59 Machine, Automatic rotary type - 61 Machine, Single hose type.... 60 Machine, Two hose type 59 Protection of Operator in.... 62 INDEX 323 Sand blasting quickly cleans "old" work.... 59 Rev. per Min. in barrel 61 Roof, Construction and ven- tilation of 62 Saddlery hardware 59 Superior on light and deli- cate castings 61 Use of grit and shot instead of sand 64 Value of, in Elec.-Galv. and Sher 59 Sawdust in zinc, Effect of 281 Use of in tumbling 213 Scale, Removal of. Time requir- ed for 47 Removing 16 Removing by sand blast 58-65, 213 Removing by water rolling 51 113, 136 Removing from wire - 119 Removing with muriatic acid 48, 113 Removing with sulphuric acid 47, 111 Schoop Metal Coating Process Coating with aluminum by 96 Schoop Metal Spray Process.- 94 Detail of old stationary type 96 Details of first portable appa- ratus 97 Details of pistol 99 Evolution of apparatus used 95 Method of holding "pistol" 103 of applying the coating 101 Operation of first portable type of apparatus 96 Operation of old stationary type 95 Operation of the cyclone ap- paratus 98 Pistol, Gas pressure required 101 Pistol type of apparatus 98 will fill pinholes and defects in sheets or coatings 104 Schulte's Elec.-Galv. barrel 172 Grinding and scouring ma- chine 213 Wire Galv. machine 204 Scoop, Dross, Construction of.. 33 Scouring and grinding machine 213 Scratch brushing 211 Screener dust 276 Screening machine, Dust. .233, 251 Screw conveyer machine, Daniel's - 158 Screws, Allowance for thick- ness of coating in Sher.... 268 Equipment for Sher 233 "Scruff" or dross, Method of handling work to prevent the attachment ox 125 Setting small galvanizing kettle without ash pit 20 Sheet steel. Temp, for Hot Galv. of 68 Sheets, Bright Galv 74 Determining spelter coating 310 Formula for Elec.-Galv. of 218 Hot Galv., by Bayliss pro- cess 76 Hot Galv., by hand 73 Hot Galv., Construction of machine for 74 Hot Galv. of 73 Material required to Hot Galv 75 Pickling 44, 46, 111 Schulte machine for Elec. Galv 204 Sher. test of 296 Tests of durability 225 Sherard Cowper-Cowles, Inven- tor of dry Galv. process.... 227 Sherardized steel magnified 100 times 228 Steel magnified 1300 times.. 229 Sherardizing articles which cannot be successfully coat- ed 231 Art of 227 Cause of black spots in 279 Cause of unsatisfactory 232 Cleaning most important op- eration in , 232 Cleaning very essential 280 Coloring and finishing 282 Cost per ton 284 Cutting down screws and threads 267 Definition of 228 Depositing copper or bronze after 282 Discovery of 227 Dont's in practice 278 Drums 233 Drums, Life of 250 Fats will redeposit in 281 Flaked work cause of 281 Furnace 233 Fui-naces, Coke burning-234-240 Furnaces, Controlling heat of 238 Furnaces, Electrically heated 248 Furnaces Elec. heated, Op- eration of 271 Furnaces, Elec. heated, Pack- ing 266 Furnaces, Gas and oil burn- ing 229-248 General operation 275 324 INDEX Sherardizing Heavy deposit 275 in prehistoric times 227 Inspection of material before 279 Japanning after 282 Lacquering over 283 Materials used in 256 Motion during 273 Must not be done in same room as pickling 278 Nickling over 282 Non-uniformity of coating remedied 279 Not a solder 281 or dry Galv 227-286 Plant, Floor space required for daily capacity of one ton 233 Plant, Location and equip- ment of 233 Plant, Typical floor plan 233, 234 Preece test for 294 Preparing material for 261 Pure zinc gives best results 231 Temp, and deposit chart 270 Temp, in 256, 257, 262, 267, 270, 275, 279 Temp. Uneven effect of 279 Test, Salt spray 225, 304, 311 Testing by electrolytic meth- ods 302 Theory of 228 Time required for..257, 272, 275 Value of zinc oxide in 231 Various stages of 231 with Zinc under vacuum 272 Shot used instead of sand in sand blasting 64 Sinks, Temp, suitable for Galv 68 Size of conductors. Figuring.. 207 Skimmer, Use of 89 Skimmers 32 Skimming kettle for rem_oving surplus tin in re-tinning.. 127 Skimmings, Dry zinc 84 Sal ammoniac 84 Sal ammoniac, Recovering.. 90 Sal ammoniac, Storage of.. 89 Slabs of spelter, Arrangement of in kettle 67 Slag burnt in, Efl'ect on Sher..279 Slag, Removal of from tinning kettle 141 Smooth coating, Agents which produce 222 .secured by using grape sugar 218 "Soaking'' kettle 121 Soda, Caustic, Test 293, 303 Sodium acetate in Elec.-Galv. solution 221 Aluminum, Chloride in Elec.- Galv. solution 221 Citrate in Elec.-Galv. solu- tion 221 Sulphate of in Elec.-Galv. solution 218, 219, 220, 222 Solution, Caustic soda 210 for testing Elec- and Hot Galv 287 Lime, to neutralize acid 262 Solutions for Elec.-Galv 217-222 for Elec.-Galv. in open tanks 218 Pickling, Temp, of 262 Spangled, Preparing work to be 68 Spraying pistol, Details of construction 99 Specifications, Galv 287 Spelter, Coating of sheets. De- termining 310 Coating of wire,Determining 310 Packing slabs in new kettle 66 Prime Western, vs. Remelt, Calorific value 68 Selecting best for the pur- pose - 42 Slab zins 41 Spirella Go's Elec.-Galv. plant 150 Spongy deposits, Cause of 223 Spoons, Iron, Tinning of 109 Steel Tinning of 119 Stamped steel, Wet tumbling of 213 ware, Retinning of 121 Steel, Elasticity changed by temp, and length of dip.. 80 and wrought iron, soluble value of 18 Hot and cold rolled clean- ing of 209 Pickling 48, 261 Pipe, Temr). for Hot Galv. of 68 Proper grade for making Hot Galv. kettles 18 Sher. magnified 228, 229 Stamped, Wet tumbling of.. 213 Tinning of 106 Sticking together of work, How prevented 71 Storage tanks 48, 57 Storing castings after tumbling 57 Strength of wire influenced by Hot Galv 78 Strike zinc - 223 Stringing work for Hot Galv. 70 Stupakoff", S.H., Paper on py- rometers ^5 Sublimation 228 Sugar grape in Elec.-Galv. bath 218, 221 INDEX 325 Sulphate Iron in Elec.-Galv. bath 221 of aluminum in Elec. Galv. solution 218, 220, 221, 222 of copper test 226 of sodium in Elec.-Galv. so- lution 218, 219, 220, 222 of Zinc Elec.-Galv. solutions 218, 219, 220, 221, 222 Sulphuric acid 43 Cleaning sandy castings..49, 112 for cleaning sandy gray iron castings 135 in Elec.-Galv. solution 219, 220, 221 pickle 49, 211 Pickle, Test of 262 Removing scale with... Ill Substitutes for 48 Tanks for 16 Test for Galv. coating.. 225 Use in cleaning sandy cast- ings 49 Use of in removing scale 47 Surplus Tin, Method of remov- ing 118 Removal of in "skimming" kettle 127 Removing from wire tinned in coils 119 Surplus Zinc, Removal by me- chanical means 71 Removal of from wire cloth 77 Removing from castings by brushing 70 Removing from work dip- ped in baskets 71 "Sweating" prevented in plat- ing by tinning first 129 Sweating zinc dross 87 Sweepings from Sher. plant.. 281 Switchboard 149 Switching box. Construction and use of 143 Tallow in re-tinning kettle. Condition of - 123 Tank for kerosene 118 Tanks, coating by Schoop pro- cess 104 for acid and water 30 for caustic soda 114 for cleaning sandy castings with Hydrofluoric acid.... 13 4 for copper bath in Elec.- Galv 198 for elec. cleaner 149, 215 for Elec.-Galv. Construction of 208 for tinning 107 Tanks, Hydrofluoric 16 Lining with sheet leads 31 Pickling 208, 233 Pickling and cleaning. Loca- tion 233 Oil, Construction of 142 Rinsing 114 Sulphuric acid 16 Washing 165 Water 16, 108 Wooden, Construction of 31 Tannic acid, Its eff'ect on Elec.- Galv. bath 222 Tartaric acid in Elec.-Galv. solution 221 Tea kettles cleaned in tumbling barrel 54 Temperature caustic Soda test 293 303 in Hot Galv 20, 36, 67, 68 in Preece test.. 290, 294, 297 in Sherardizing 256, 257, 262, 267, 270, 275, 279 in Sher. chart 270, 271 in tinning 115, 117, 118 of hydrofluoric acid pickle.. 49 of molten zinc. Effect of at- mospheric conditions on.... 39 of tin for coating on 39 of tin for coating gray iron castings 117, 141, 142, 144 Methods of calculating num- ber of degrees drop per hr. in molten zinc while cool- ing 38 Natural actions in tank en- abling experts to accurate- ly judge 37 of zinc required to secure un- iform coatings by hot pro- cess 35 Regulating by pyrometer 34 Too much heat destroys kettle 37 Variation aff"ect tests 297 Temperatures determined by color of zinc, etc 68 Test, Caustic soda 293, 303 Cinder for Galv. coating 225 Copper sulphate or Preece, 290, 294, 301 for neutral Elec.-Galv bath 223 for thickness of zinc coating on armored cable strip.... 226 Government 303 Hydrochloric acid and anti- 'mony 308 Lead acetate 291, 299 Lead acetate, Advantages of 301 Moist air - 226 of hydrofluoric acid pickle.... 263 326 INDEX Test, Preece 290, 294, 301 Pure water for Galv. coat- ing 225 Salt spray 225, 304 Sulphate of copper. 226 Sulphuric acid for Galv. coat- ing 225 Zinc coating 226, 287, 312 Testing box. Salt spray 309 Salt spray, Details of 311 Material for mfr. of Hot Galv. kettles 19 Zinc dust for metallic con- tent 258 Tests, Galvanizing 288 Comparative 225, 304-307 Percentage of error due to temp, variations 297 Preece and lead acetate compared 301 Used to determine strength of wire 79 Theory of Corrosion 11 Thermometer, Method of using 39 Time required for testing 292 required for Sher...257, 272, 275 required for tumbling 55-57 required in Hot. Galv 69 required in Elec.-Galv. 218, 219, 223 required to clean sandy gray iron castings 135 Tin, "Boiling" to prevent dross from interfering with workl27 Coating applied in a molten spray 94 Dipping gray iron castings in 138 not electro positive 12 Proper temp, of 117 Surplus, Method of remov- ing 118 Surplus, Removal of in "skin- ning" kettle 127 Surplus, Removing from wire tinned in coils 119 Temp, of 106, 115, 118 Tinned work. Old refinishing- 146 Tinning, Applying the coating 115 castings Math three kettles of tin 144 Fuel for 107 gray iron. Plant and equip- ment for - 129 gray iron castings 129, 138 gray iron castings, Flux for 138 Gray iron castings must be absolutely clean for 136 gray iron castings. Prepar- ing work for 133 Tinning, gray iron castings, Proper heat for... .138, 141, 144 gray iron castings. Time re- quired 138, 141 iron spoons 109 kettle. Flux for 139 kettles. Materials used in con- structing 144 malleable iron castings 106 Passing work through kettle 117 Plant and equipment 106, 130, 144 Plant, Drainage of 109, 130 Plant for gray iron castings 130 Preparing work for Ill Steel 106 Steel spoons 119 Time to prepare castings for 59 Tools and kettles for 109, 116 Wire in coils 119 with two kettles 116 Wrought iron 106 Tongs 31 for re-tinning. Construction of 127 Proper use of 70 Self-acting, on Hot Galv. ma- chine 75 Use of in Hot Galv. sheets.... 73 for Hot Galv 31 for tinning 109-116, 119, 142, 143 Tragacanth, Gum, in Elec.- Galv 221 Its effect on Elec.-Galv. bath 222 Transfer car, Construction of 253 Trucks, Transfer 233 Tube and Pipe Galv. Machine, Hanson and Van Winkle.. 189 Galv. Machine, Potthoff 191 Tubes, Automatic Galv. of 81 Comparison of cost of Galv. by hand vs. machine 83 Handling of to prevent trap- ping of air while Elec.- Galv 194 Hot Galv. of - 77 Machine for Hot Galv 82 (Tubing Furnace for Sher 248 Tumbling 51, 113, 136, 213 and sand blasting 149, 213 Tumbling Barrel, Charging 213 Construction of ._.... 53 Leaving work in it over night 56 Loading of 54 New cleaning preparatory to using 57 Operation of 54, 136 Recharging of 55 Rev. per Min 61 Solution for cleaning cast- ings 55, 57 INDEX 327 Tumbling; Barrel Speed for cleaning castings 55, 57, 60 Time required to clean work in 55 Tumbling Dry 52, 209, 213, 283 Dry, of wire work 213 Gray iron castings 133 Time required for 55, 57 U Under pickling 45 Unloading and cooling drums 276 Elec.-Galv. barrel 168, 173 Unskilled labor in Hot Galv... 13 V Vacuum, Slier, with zinc under 272 Vapor, Effect of free ions on precipitation 230 Precipitation of 229 Tension 230, 231, 270 Zinc, Methods of producing.. 230 Vegetable cutters, Tinning of 129 Ventilation of Hot Galv. plant 14 of sand blasting room 62 Voltage 193, 223 differences 153 for Elec. Cleaner 216 for Elec.-Galv 218 Proportioning of 207 W Washer foundation. Cast iron 25 Washing tank 165 Water heater, Coating by Schoop process 104 Rolling 51, 61, 113, 136 Rolling gives better finish.. 58 Tanks, Construction of 30 tanks for tinning plant 108 Watrous machine 72 Wet rolling barrel gives better appearance to work 58 Whipping box for tinning 108 White pickling 46 Winter, Dr. Heinrich, Paper on strength of wire 78 Wire Cloth Elec.-Galv. Ma- chine King's 194 Formula for Elec.-Galv. of 218 Machine for Hot Galv 77 Machine, Root's 202 Hot Galv. of.- 77 Influence of Galv.on strength 78 Wire Netting, Elec.-Galv of.... 194 Hot Galv. of 77 Wire, Schulte machine for Elec. Galv 204 Sher. test of 296 Test 308, 310 Testing samples 288 Wire, Tinning in coils 119 work. Dry tumbling of 213 Wiring diagram, for Elec. heated Sher. furnace..249, 250 Wrought iron pickling 48 pipe. Temperature for Hot Galv 68 Tinning of 106 Zinc, ammonium, chloride better than sal ammoniac 42 Zinc ashes 84 Method of recovering 90 Recovery of fine not profit- able 91 Screening of a good practice 91 Storage of 90, 91 Zinc best rust preventive 11 Boiling point of 272 Chloride in Elec.-Galv. solu- tion 218, 219, 220, 221 Zinc coating applied in a molten spray 94 by Elec.-Galv. process 148 Cost of by Schoop process.... 102 Schoop metal spraying pistol 90 Spec, for 287 Table of tests on Elec.-Galv. 304 Thickness of 267 Thickness of in Schoop pro- cess 102 Zinc colors indicate tempera- tures 68 Corrosion saves the iron 12 Deposit on sheets by Health- field process 76 Zinc dross 256 cooling in kettle bursts it.... 86 Hard 84 Kettle for recovering 87 Method of recovery 85 sweating or running over.... 88 sweating 87 Zinc dust 256 Analysis of 274 Color no proof of coating.... 281 Cost per ton of Sher. ma- terial 284 Drying out 257 Fire in. How to put out 281 Freeing it from iron 257 Metallic content 267 Determining metallic zinc... 258 Oxidation of 274 Oxidizes when sawdust or excelsior is mixed in 281 Properties of 274 Receptacle for 233 Saving of 281 Storage of 266 328 INDEX Zinc Dust, Used, Disposal 285 Zinc electro positive to iron.... 11 Iron alloy 227 Melting point 35 Melting point, Schoop process 99 Overheating, Loss from 67 Oxide Value of in Sher 231 Oxidizing prevented to flux 69 Pure, gives best Sher, re- sults - 231 Residue, Disposal of 285 Skimmings, Dry 84 Slab or spelter 41 Strike 223 Sulphate in Elec.-Galv. solu- tion _ 218, 219, 220, 221, 222 Zinc Surplus, Removal of 70-71 Removal of by Porter ma- chine 71 .Removal by Watrous machine 72 Removal of from wire cloth 77 Zinc, Temp, of 67 Under vacuum, Sher. with.... 272 Vapor, Methods of produc- ing 230 267 90 ^..** » « % ' "^ A** *A€b,^A*« Oi^ ^ A"^ ' " " " ^^ ,^ \;^P*y^ "v'^V^"^ \/^V^. HECKMAN ji|l ^-^"^"^ /^^'- \f^ "'^%''- "^rl.^ ^^M BINDERY INC. 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