STUDY OF ANODES IN ELECTROLYSIS OF COPPER LEACHING SOLUTIONS CONTAINING CHLORIDES BY LOUIS F. STUEBE THESIS FOR THE DEGREE OF BACHELOR OF SCIENCE IN CHEMICAL ENGINEERING COLLEGE OF LIBERAL ARTS AND SCIENCES UNIVERSITY OF ILLINOIS 1922 Digitized by the Internet Archive in 2015 https://archive.org/details/studyofanodesineOOstue ACKNOWLEDGMSITT I acknowledge man’r suggestions and muoh aid in this work to the directions of , Dr, W. S. Putnam STUDY ANODES IN ELECTROLYSIS OP COPPER LEACHING SOLUTIONS CONTAINING CHLORIDES Part I Introduotioii This work is interested in the study of the corrosive effects of copper leaching solutions containing chlorides upon the anode during electrolysis. Many copper ores are more economically leached and electrolyzed directly from the leaching solution than by roasting, smelting, and subsequent electrolysis. In fact there is reason to believe that in the future almost all ores that show this advantage will be eleotrolyged, there- by eliminating the great outlay in smelting plant and the great cost of fuel. Moreover the whole process will be entirely under the control of the mine operator, who will not have to ship his matte to the refineries and depend upon them for the speed of his turnover. The requirements of a plant for the electrolysis of copper leachings would be a choice of the various leach- ing processes of which there are now several rather high- ly developed, and a dependable scource of electrical current which is easily obtained in our mountains from hydro-electric stations. The other requirement, which is the primary one and has thus far probably been the chief cause for the reluctance of operators to establish it, is the electrolysis process itself; which means the study of the character of the leac^^ing solution, the control of the ty f i *: * r ( I / I s ( t I > b'j i t * :.'( \ I. I' tff. f iC ^ ^■ 'f> w X X ( X J- i J..' ». ( k ■ i t I w. %..:• .A - 2 - current, and the type of anode. This problem is primarily ooncerned with the study of the anode when the analysis shows the presence of chlorides. In this thesis the work has been carried to the study of iron alloy oxides only as the author was unexpectly halted in his work. However as the preliminary study has covered the field of all types of anodes in general and their probable development to obtain the desired non-corrosive anode for copper chloride solutions, and to assist any who may continue this study, he has included in the history and conclusion such information as he has considered of value in the continuation of this study. ^t>r * i/ ’ f '■” ' 7’ - -l~'- ■'^ '» fft ?!.*• *k: 3 a 9 H« y-. ■:l^y '' / » ■■•,‘:f -■ ■^■rf-v,. ■ A'^i ■.; i-'>'- ■ ■ r i &ir>r ' » *(|^;U‘iV«5i*y ^ "■ '?* 'll .. 1 \|'»V*' *'f 4 ,.*»V 1 »»*Ii»VT '*'1 •to ’,, i'A'vf Li. •. ‘-'“.'^‘V,.' ?►■ u ;-'i>,iHlK • ’ •; . ' _ « ■ _ . ' * ' I W '’ • ^ ', ■ * ; . - ’^urtTa * oo tdtttHa itA»^ fidi' leJ-I'-S< \I-n(j(T. t-M •vwC'itti iHi." wf- l;.> i','}Ol M-Vl >;B^'IS "’*>=5 C* ^*Wt J,«l'. Sifl at* ?Vj VA *:■ ; , T’f(» ■ W '■ "? . ■ 7 > ■> •> vim'J, /■ 'U^fliji-.. ^ 6 ,- •■ '^ '■ .11.= •. > - ■- 1 '•; 'r^’V tiv;,'0‘t':r?r“i'.r.ii hp^l^’A- nUrpi^i;OCjyiwm ^ilactgric: uv'..’ ^^n^.'vr rj* 'fpi#. * o^/iioldo' ;XA^' ■*-« I* t i*' tiv-^ 'o L? \£iLf«itiAc.' tiit fr. ■ ■ ■ . '..• ‘ •' t« W , » • , *H.rt 4 feiPrvi it. 3 ^^,.. ,'y •*' ' ■' ■' '■■■'. ■ ' ' . ' ■' i . i. sf‘,/ *3 ..!■! ii. I V ivi». }i_ > ,fiPi ■ ■' „..' ^ ^ 1 * ■ni ''M w \' B J ■' » - I * i -' '■ ' ■ '• •- '% j'jf)! rM,^ .' ’V, 'wx • •'*.. '\ Ji*- » f?--l f ?M- ^ V ; V .. x>\^ ' A!¥< ,' '•■ ■' '^ ‘ *' ' ” ■■' '* ':’• ' '’.;^ !l^,» -Ilf-* ^ V ■ /'■- -ni- ' ■* it*: *L‘ • " J , .■•r\ '»", ■' ' '•! t r, 3 Part II History I'he oorrosion of all anodes in oopper electrolysis is imown to be an unavoidable loss. I’o be sure the ideal anode would be an absolutely non-corrosive one. However among anodes there is a big difference in the degree of solubility of the same in their electrolytes, consequent- ly when an anode shows little corrosion, as lead in copper sulPhate solution, it is termed as non-corrosive. Again an anode may be non-corrosive in one electrolyte and be quite corrosive in an electrolyte of slightly different composition. In addition the efficiency of the process depends upon the character and temperature of the electro- lyte, the current density, and the voltage; all of which must be considered along with cost of anodes in determining the economical value of a given process, These are the conditions which contribute to the complications involved in the study of anodes in electroly- sis of copper leachings. The industrial electrolysis of copper leaching solu- tions is in general this; The copper ore composed of ohalcocite, azurite, malachite, along with other minerals, is first crushed fine 1 . in rolls and roasted as in the Laszczynshi process. Then it is leached with dilute sulphuric acid, or with dilute sulphuric acid and ferric sulphate solution as in the 2 Siemens-Halske process. Consequently the leachings contain copper sulphate, ferrous sulphate, ferric sulphate, acid. • ^ * O I •JP- r ;; riofljv u C T .ii ,f---:!t £ t?A. r •■.! cr- |. :.• ,i).» 'vi- f«V.tu0‘‘U<'*. - t,' I.'.. ••• U r •! • ' ■ - f . i 1 w *■ ’ ■ ^ • , ■ ij '.'JJ-M, r'i* -'..Ci I •' ^ ■"•- L . . ux; vK^, tj&'ci. '. ' I- M ' ■ - ■'^ . ' •■ "c 'X i ' X J t - :• i. '■ ■*• I--.- .1.' -1,. . . j^■. ', . I, V ' ^ . 'tf j.' ' •' iiX . - •• • - i’ i-^.U ii'. ••• . •• ■ - <■■ -tC • If; ; I ; 'L: ■ •*-' v*'»'i»Cg6ti ; ,j t * ''■'"'"ki -- ^ r> . ' - 0 • ;ci- ' , ( '. ■. t‘- a ‘,-.v { i jCCTj^c.c 1 i.f .! V !'■. ' • - ! } .'f* ‘..c. ^ a'i.L I’v V., ‘ ‘'•'.-f k'.r t t XC;-Uf . - ■ (V,4. . iC‘ '. • - <>{ :c n.fi. 'Tr'i ' v> f a - „ ~ ; ii'- . t'X '‘ av ■ •', iifc] ' ' ' T./^ • /.' <•• n j, ' ^ * * ’ Vw-lw V t Ji .'. M 1 . f : t ' A V • ' r:rii;iA.....;,i.o!'’ . i'-iw?'. r-jJ 'A's ij.y.i l.'r{ ,;y .. >W9X * *!■. ' 4 and other impurities. The copper leaohings are then introduced into wooden vats, many of which are lined with pitch or asphalt. These vats vary in design and capacity, but an average may be taken as 4-|- feet deep, 3 ^ feet wide, and 6 feet long. The leaohings are run in by a circulation method, that is, the solution runs from vat to vat by gravity, varying in concentration, or it is electrolyzed in one vat until de- pleted of copper. After this the liquor is sent back to act as new leaching solution. Generally in either case some means of maintaining circulation is employed. This is occasionally done mechanically, by flow of electrolyte, or by bubbling gas through the solution as is done in the 5 Carmichael process, in which SOg is passed through not only for stirring but also to furnish fresh sulphuric acid and assist at depolarization. The cathodes are copper sheets about l/32 inch thick and by 3 feet with a heavy cross-bar across the top as contact arms. They are generally given a thin coat of glue or engine oil before being started in order to give a uniform and well adhering plate. The anodes are of various material and measure the same as the cathodes except that they have varying thicimesses. They also have a strong contact bar across the top. Along the upper edge of each of the two long sides the vats have heavy copper bus-bars to make contact with the cross contact bars of the cathode and anode. One •.v.; I ■ i It ■ ■ i- >-‘i • V , j -'r .’C'a fjiU 'I ij.; -'loo m‘ ■' ' ,xC‘i^t I r*'» -1 ^ i: '- <■ ‘-C.*' j A 'i ’; f iOhl ' I ’ '’• ^ ^ , _ t' ' • J .'.X >.,( ‘ ' 'iS. L w' . o'jid :. I , ii''' i. . .‘J f.^r.., , *.i : - ’il:. . ni ;U. - , >1 I-'.. ■ ->i , .. tS'7, ' ' , * .'.’it :i ' i .I'i’; oj ov:i . , 0 ■•• ' i ■ J - t. ' -U*‘- ' 3 'iU ' - ; liyp^ic .;:uilwP' ',d uo'i . ;..,t - / -.• .■■',• Ol' i- ?• '' iVr ■'1 ••■ ■. ,. *u iti, '-L i'..i '.j'.'ij AXf -I'/J-Ij 'So -£•- , iii. i:;‘ZO! ’ •i> a ,.i . i’^rv '10 t.'l" wi*?" >. .. -• ..c ^ ,’f .■. . ' »1'a' ' i'/'r : ' • '’f ‘. ■>/ Otl'Xu : ■•. ..'• 'f'.' Lk "JIJ .M r;-,0',U •• ■ • .Jr'-'' ■ ;'!7^ . -M - 5 - is positive and the other negative, and are so arranged that the positive makes oontaot with the anode, and the negative with the cathode. 2he ordinary voltage for simple sulphate leach- ing solution is 2.2b to 2.b0 volts, and the current densi- 4 ty is 18 to 20 amperes per square foot of cathode surface. The corrosion of anodes in general is quite well understood in the electrolysis of copper sulphate solutions 1 2 as used in the Laszczynski or Sieman-Halske processes. In fact the process is very simple when no iron is present, in which case lead anodes are used to the greatest advantage. However in the presence of iron sulphate some handi- caps arises from the polarization of the ferrous and ferric ionS. i’or best results, control of the ferric sulphate concentration is essential as this impurity reduces current efficiency, causes poorer deposition of copper, and when the copper concentration becomes low in the presence of iron 6 sulphate, an additional decrease in effioi^^oy observed. The lowering of efficiency is due to the solvent action of 7 ferric sulphate upon the deposited copper. regener- ated sulphuric acid or ferric sulphate solution is used over and over again, the ferric sulphate becomes so concentrated 7 that soon all the copper is redissolved. Thus ordinary resolution at the cathode is 2 %; but when ferric sulphate reaches the concentration of 2b>, it will corrode cathode copper to such an extend that 8 amperes will be required a to merely replace. The formation of ferric sulphate is prevented by inclosing the anode in porous material to ri, . . ’ ^ 1' C ? i. < I t. ' f, *- * * C. f ^ ^ . ■^■. ^ i i, ' t ■* ' ^ .. ■ ..{ #V- i->- - ■•■ •■ '■ .'-ot-'t' > ; : •..w'. *iV . .1- -C w ’.' ^ ^ t t ; .•*. .-.•ivCi.'f. '0-‘ if i. • :. . ;i • ■ .: .iJ 4. r .. ■ i :.. . . .r’ i- ct) .'i - lul '(.f ' ’ -t i^'O* ■ i. ’, .' j ...i c..r ri. , t.i i o ', 'v' of tvivl ■ 7>*VO • • ■ .. - .a •- r ■ . -V * * a ^ fJ i-* V ' , . a,Ji. 'L^c aU -- i ...linjiclar- t '' -i t ; oi:-?;.. .' i ’ ' r ” ".’*7 y.r ' ;2,jt wt w.- . ;. , ■> . \L.'~ , '■’•t' ! 0 , -V . ' ■ ‘ ; . _i. . ■ ■ i* ' ' - >■■ • ‘ O^J IWv' " i-i ' :> 0 '' b&i I .. ,rU 'H. I - o - 8 prevent transference of ferric ions; thus tight fitting bags are frequently used, the thicioaess of the cloth varying 7 inversely as the strength of the current. This illustrates the disadvantages of iron in the elec- trolyte, a metal which is present in all copper leachings. Nevertheless lead anodes are used the same as in simple copper sulphate solution, the lead anode merely peroxidizes and sulphatizes slowly as it is slightly attacked by the free a oxygen and the sulphate radicle. But when chlorides are present, lead will no longer serve as anode as corrosion is too rapid. Chlorides have a corrosive effect which is little understood electrochem — ically or otherwise, and as valuable copper leaching solu- yions are known that contain chlorides in considerable amount which can not be removed to any advantage, it be- hooves the metallurgist of plants having such leachings to find a non-corrosive anode which is econoijdioal enough to put this copper on a competitive market with copper from copper sulphate leachings. As an examination of the literature shows that chlo- rides in copper leaching solutions are considered as merely to be avoided, and no strictly theoretical explanation has been made for the apparent cause why these solutions be- have so much different from sulphate solutions, the author has had reference only to such practical work as has been experimentally undertaken from time to time to solve this problem. ^ ! \ ' •> 1 '■ ' 1 I : ■< ;uv*'i . ''•ver;:^ ‘"h -yc •{• .;,'TM t-'S-ln '■ . .' Ji^'rvi’r*'? ^ ^ c. w'lfv i’ .'►-. 'j. I .,‘.C / ', ». . 0 . ■ • ■ ^ ..' li '. u ■ -,.J J ' \ I r 4 * L > &•# ■■;.'• . j . .. ' , -JV* <, ;vv .'>r^v 1 V 'V^,' ; i ■ f :{ 1 f . .A’-'* fj u; i; -aii.f. r ^ ' V ’ >>./*'■ ' ti.'' i • r^,-.. . t I >v’ ' ♦ • • •)■*."• *>T ’ - ■ •' •' ..-v .. , ' . '• t \ vj :;'/&{ 'I'icr i ■' . i .. V ? ■ '■ ' di> ■ - ; i iL.-'-iti' ■■: ' C ' ' ■' r»,' QXt •?■ .•• Xf'- ^ f ^ . r t/U CJ -0 .' ' ■ ■• . • ■••. 0;-OlV ’^••.'.v 0;.;* f fc rOViH; ;’.l,t O'i V V ji>6 1.: i>' '.r J.tj ' V.i I'j j : ■ .. ..: r •!•<:'. X, ■.1/t’^vj "VVC bsiJri f •■• r I'V •r.X ■.:o'yX nr/;»;jX.V ' ' • ' -v' , Vi . ':i\ < , ■ , ■' a*» t w y fc» ik"^ 'ti t. - 7 - 9 2he Hoepfner process using leachings containing cuprous chloride has been developed. It uses two coropart- ments, anode and cathode, each containing the leachings, and for an anode uses carbon. The two compartments are separated by a permeable diaphragm. However it has been found unsuccessful on account of the short life of the diaphragm and the corrosion of the carbon anodes. When leaching solutions contain chlorides, fused magnetite or ferro-alloys, generally ferro-silicon, is now used* Where an efficient depolarizer is employed, besides 3 the materials mentioned above carbon may be used, however depolarization must be complete. 10 The Chile ]jlzploration Co. used fused magnetite anodes in their South American plant in a leaching and chlorination process until no more could be purchased from Germany. In their research department at Perth Amboy, IT. J. they found th© best substitute to be Ibyi ferro-silicon or ’’duciron”. This is not as good as magnetite, as found by use in their 10,000 ton plant, as it required Ibfi more energy and raised the temperature too high for the asphalt insulation that 11 was used in the vats. Later Colin G. Pink, now director of the Chile Exploration Co., said that 13‘4 ferro-silicon has been found superior to lead and magnetite as an insol- vent anode in electrolytes containing not only sulphuric acid, but also nitric. Although no mention is made of chlorides, the statement of being successful in nitric acid may be taken as meaning hydrochloric as well. He goes on to say that next to ferro-silicon, the ferro-chromes are r I . . o ' j !^ ■ ' • \ f f ** ^ i t f f .1 r *■ t r ( ? 8 - industrially important as non-corrosive alloys. However, although chemically corrosion proof, they are not very electrolytically corrosion proof. He says that 60>i chrom- ium and iron is the best, and in addition that niciel- chrome alloys are becoming popular. However a recent letter received in the spring of 1922 from the U. S, Hureau of Mines by the Division of Applied Chemistry of the University of Illinois, stated that although f erro-silicon alloys have been found the most satisfactory anodes in the electrolysis of copper ores containing chlor- ides, yet the results were far from being successful, and said that research in this direction should be encouraged. Consequently the author started this work under the directions of Asst. Prof. Putnam, .. . ...V t^X/'j-finoiVo V' .*- “'•t ' /.!• »■ » JJ 'rn • : > -ri L / . V4 .( , • i t>t^V L. ■ M - I ■V ..i; v7T*f-’JU'' A-’-^ 'i -i. .T. .' ■>.> ^ 4 \ , -.. b-iliy i , ,.'t, i;T ‘•.^■■v* .•■'.{■ t.V 0 'a. 1* / i i V ' ■' tit;;, ! vi .'. , , . ■ .Tr i^ } < - ' [k . . - 1 v *l.' '.. -i r; ? ' ■■ •'■iUl',, • i X, 1 I'..' ' .-r-fiei , 5: [(■•. f' 1 • . ''■ ' ■ C f'J'‘ .*T‘ ‘ 1’, r- . 't . • l.Cif (IT. jr , i - ,. . , ; .*• ,ll *£« ■•."•:»•: .' ”4.. i! ff.' k ■ >;v •'■ ^ '*-V' r,v<‘a' '**»- 5 ' k * 4 .W*fc^ I r ' - A • V ; ;ar- i- rv' >:.;; . v,(. oO? ; .. t-u , (. V i ■ «■ i ;■' -j MjLi'' : j /i- y ■ i-- «•• • .••> ^ ST , .ui it'Ci'XS 110?!?^ ‘. .., ‘ i. ..o*AXr^ f .'.i>. Xc'v^ ,j i. j|:{Xr-‘Ci^' 'J w j3j»/lj;'' : \ fiv « ' : od^ : i L ' • / ' 0 ,‘t, .<» .' •. ..i •■.X.I.-.T'i-' ■iiV ’■J'lii.. . ' cvl'ti ■ j .’*11 * ’’ .'U“ 1 ' -o '- \ ■’• ' •■•■•' ' tl*. ! ut -r.,;', ‘.■-.,.v- . 1 ? -r.i i C' 'iV‘ vd , # ilL « 4 -f *' .U'ju. 'Md f. . o: ••: oO*'‘4-‘,o t , » 1 ‘ ' :) ' V ' ..■- : . ; ; ■", '.Caj ^ ,J I' I ■ ' >; '^‘7 C-J-. ■ •' •v.rt ‘'■'i f.'X/iV ,i.V ;:t v*iCV . ^ 1 , - r ', Tnd ''0 I 11 degree ol resistance of the anode surfaces, 'fhe solution was not circulated or replenished, but was run to a fair exhaustion of the copper. Temperature was room temperature. }ixperiment fl Solution -jtl 5% Hi-steel, oxidized 3 min. Voltage maintained at three volts. Amperage as shown in Tab. I , and figurell, pp. 12 and 13 respectively. Exp • #2 Solution #1 Hi- steel, oxidized 10 min. Voltage maintained at 2.b volts. Amperage as shown in Tab. I, and fig. I. Exp. #3 Solution fl 5/i Hi-steel, oxidized 10 min. Voltage maintained at 2.0 volts. Amperage as shown in Tab. I, and fig. I. Erom the tables and graph it is seen that the IQ minute oxidation made it possible to have the same amperage at a lower voltage, 2.b volts, as compared to 3 volts for the 3 minute oxidation. Also the flatter curve shows it to be more constant and able to maintain itself better. The 10 minute oxide at 2 volts and 2.1 ampere shows the best result on this alloy and its observations are noted in the tables. Corrosion of the anode in each case was quite Uniform and deep beyond the point to classify them as non-corrosive . one encouragement was the lov; voltage at which a r ♦ •'<. ‘ 1 ' I • ■ ■/■jt« -#.h ^ v‘»vu; '.ti 12 Tables I S/4h Ui-steel Solution fl Constant Voltages Time ]?jxp. jfl ij;xp. if-2 3 volts 2^ volt current in ii:xp. f3 s 2 volts amperes Observations on ijjxp, f3 0 .30 .30 .21 Ho gas evolved at anode. 15 .35 .30 .25 30 .37 .30 .28 46 .37 .31 .30 Cu begins to deposit on 60 .39 .33 .32 anode. 75 .43 .37 . 36 Scales begin to form on 90 .49 .42 .41 anode. 105 .62 .47 .43 120 .74 .52 .43 135 .79 .55 .43 cu on oathode deposits 150 ,85 .58 .47 rapidly. Cu on oathode becoming 165 .93 ,60 .48 spongy. Oas begining to come off 180 1.00 .63 .48 cathode . 195 1.03 .68 .49 210 1,06 .75 .50 spongy cu on cathode 225 1.07 .76 .50 forming very rapidly. 240 1.06 .77 .57 considerable gas being 2oO 1.05 .77 . . .58 evolved at catihode. XI i 'j V'J V ).utT -•i r. o. 1 . I* 13 li’igure I 14 strong flow of current may be maintained, thereby showing an improvement over lead or ferro-silicon, as well as magnetite anodes in efficiency. Oonsequently 30‘> ITi-steel was experimented upon. !I!hese specimens were about one-half the size of the lli-steel, and the oxidation was done thus; Sxp, j ^ 6 7 8 y 10 11 IS Time 8-8 7-7 6-6 5-5 18 15 IS The double numbers indicate that the anode was oxi dized for two periods each of the length of time given. The amperage variations for all of the double oxida- tions, or Sxp, f6, 7, 8, and 9, are given in Tab. II, page 15, and on fig. II, page 17, Experiment 8 gave the best results, and observations for it are noted in Tab, II. It will be noted that by double oxidation it was possible to maintain a current density of one ampere for some time. with two volts. The corrosion was quite pronoumced, but for the much smaller area the results were much better than with 5fg Ni-steel, The most noteworthy result was that the oxide surface showed pronounced evidence of protecting the lower area in sections, incidentally it should be mentioned that it was ob- served when drilling the holes for the contact, that the highest oxidized specimens were soft on the surface and very hard in the center. This was probably due to the heat treatment of the metal during oxidation. ( t T 5' C M r 30;i Ni- ■steel - 15 - Tables II Solution #1 Constant Volts, 2 v. Time Exp. #6 Bxp.#7 Exp. #8 Exp. #9 min. Current in amperes Observations on Exp. #8. oO .10 .10 .10 .10 Slight evolution of gas at 2 .10 .10 .10 .10 anode • 4 .10 .10 .10 .10 6 .10 .10 .10 .10 8 .10 .10 .10 .10 10 .12 .10 .10 .10 12 .16 .10 .10 .10 14 .19 .10 .10 .10 16 .20 .10 .10 .10 18 .21 .10 .10 .10 20 .21 e O .10 .10 22 .22 .10 .10 .10 24 .24 oil .10 .10 26 .26 .12 .10 .10 Evolution of gas decreases. 28 • 26 .13 .11 .10 30 .27 .14 .11 .10 32 .28 .15 .12 .12 Gras evoluti on stopped. 34 .28 .16 .12 .13 36 .29 .13 .14 38 .30 .17 .13 .16 40 .34 .18 .14 .17 42 .36 .18 .14 .18 44 .37 .19 .15 .18 46 • 39 ol9 ol5 .18 - 16 - Tables II Time #6 #8 #y Observations on Bxp, jfSm 48 • 40 .20 .15 .19 50 .40 .20 .15 .19 55 .42 .22 .16 .22 60 .43 .23 ol7 .24 65 .44 o25 .18 .26 70 • 45 .27 .20 .29 Flaking on anode begins. 85 .44 .31 .25 .35 100 .44 .35 .28 .40 Ou begins to j^eposit on anode 115 .44 . 36 .30 .41 ■^130 o44 .37 .31 .40 145 .43 .37 .32 .40 160 .43 .37 .32 .39 Ou dep. on cathode becoming crystaline. 175 .43 .36 .32 .38 Gu dep. on anode becoming crystal ine . lyo .42 .36 .32 .37 2q5 .41 .35 o32 .37 220 .40 .35 .36 235 O o .35 .32 250 .40 .34 o35 265 .39 .33 .30 OU dep. becoming spongy. 280 .39 .33 .33 295 .39 .32 .27 310 .39 .32 .32 325 .38 .32 .26 340 .38 .31 .30 355 .38 .25 370 .37 .31 .28 17 Figure II T//ne E/apsed-^ Minutes 18 From the durves it will be seen that there is a reduction in amperage down to the 6-6 minute anode when the results a- gain show the tendency to a higher current. Thus it may be concluded that for 30^* ITi-steel, and double oxidation, that two 6 minutes of oxidation is the best , For the single oxidation, that is for Exp. #10, 11, and 12, the results are given in Tab. Ill, page 19, and fig. Ill, page 21. Here the amperage was double as compared to Exp. #6, 7, 8, and 9 for the same voltage, showing much less resistance in the oxide oaating. Again there is observed a minimmn amperage when oxidized for one 15 minute period. As Exp. #11 showed the best results, the observations noted in Tab. Ill are upon this anode. * r.“ 19 Tables III 3Of0 Ni-steel Solution jpl Constant Voltages 2 v. Time Sxp.flO Bxp ••#11 Exp. #12 min • Current in amperes Observations on Exp. #11 0 .20 .20 .20 ITo evolution of gas. 2 .22 .22 ,22 4 .23 .24 .24 6 .24 .26 .26 8 .24 .26 .28 10 .25 .27 .29 12 * OD .27 o30 14 .32 .28 .31 16 .35 .28 .31 Flaking of anode surface begins. 18 .37 .28 .32 20 .38 .29 .33 22 .40 o30 .33 24 .41 .32 .36 26 .42 .33 .36 28 .42 .34 .37 Cu begins to dep. on anode 30 .43 .34 o38 32 .43 .35 .38 34 .43 .35 .39 36 .44 .36 .40 38 .44 .35 .40 40 •44 .36 .40 46 .44 .37 .40 50 .43 .38 .40 65 .43 .38 .41 ft - 20 - Tables Ill Time #10 #11 #12 Observations on Exp. #11. 60 .43 .38 o41 Cu on anode becomes cryst. 70 .43 .39 .41 80 .42 .39 .41 90 .42 o39 .42 100 .42 .39 .42 110 o41 .38 .43 120 .41 .38 .43 Ou on cathode becomes cryst 130 .40 .38 140 .39 o37 .43 160 .39 .37 160 .39 .36 .43 170 .39 .36 180 .40 .35 .42 190 .40 .34 .42 200 .40 .34 .42 I 4 Figure III T/me £ lapsed '^m/tri/tes 80 /zo uo zrao 22 Part IV Conolusions As will be seen the results were not suocessful as to producing a new anode. However they are conclusive in the study of the oxide, effect of time and method of oxidation, and effect of voltage and current density. Thus these results may be used in the further study of the anode especially in terms of oxide coatings. It was observed that the higher Ni-steel alloy showed less corrosion and a greater adaptibility to take on a protective coating of oxide as shown by lower amperage and corrosion of anode. That double oxidation gives better coatings than single oxidation as shown between the amperages in Tab. II' and' III. That a minimum amperage may be obtained for a given alloy by oxidizing for a certain length of time, either for double oxidation or single oxidation as shown by curves on fig. II and III. .J »; , „y.. 1.1,. . I ...•;» .', :• c:>- *-■’ 1. , ..v»clv * .V'-H • V Joo" ■;« ■ 2:-,, , ’■ Xf‘u, t;i'£ ;lr7 ai,- ,^ - ' .O^ ' .{. '. , ‘ I'' 1” " ■ j ■j ' .' <. t. . tsj* ' ’1/ -tMiU’ t’W>* i:,. . <1.. * '■■- lCl • ■' f: L'l f\ i "Jv^ <‘f' 'Ml . ; 1 *j I i • *i »I'.i ; : I 'J.‘> . '. t. 1 <, v^trl fif'. '-To '* Oifcv t'.i.T. • ■?> ' i' f ) C' *1% i ' ' 'm» s -,J .', < ,r . '.0.: ■ , . ...M • nj. iV . A.'i'*vO '1,1) . t'l '. « Z i)i' rU' r,‘i 1 ■ H j" • r Ca - 23 - Part V Suggestions Better results may be obtained by hammering the anode as it is withdrawn at the red heat from the niter bath, then after sufficient treatment in this way it should be given a final bath without hamraering. The theory is to get the oxide ooating as dense as possible. Another attempt would be the fusion of the oxide coating if possible by heating to the fusion point of the oxide. This would tend to approach the quality of fused magnetite mixed with nicxolous oxide* Also similar tests should be run on ferro-chrome and ferro— silicon alloi^® with oxide coating. The study of aluminium alloys seems plausuble due to the low position of aluminium in the electromotive scale. Also, if available, experiment should be made on a 13 nevi/ alloy developed in Italy, imown as biaAmetal. The approximate composition is this Metal Kange Average Copper 35-44% 40% Iron 1.6-4.76 3 Tungsten 3-6 3 Nickel 60.6-46.25 54 Acid resisting qualities are these: Sulphuric any strength under 100 degrees Cent. Hydrochloric ” ” ” any temperature. Acetic ” " '* " " Citric ” 24 Tannio any strength, any temperature Cold nitrio up to 1.40 SP. gr. 25 Part VI Bibliography 1. Hoffman, Metallurgy of copper, 1915 HcL., p.414 2. ” , " p.430 3. Lawrenoe Addicts, Chem, & Met,, Vol.23, p.llO 4. ” ’’ , ” ” ” ., Vol.23, p.275 6, Hoffman, Metallurgy of Copper, 1915 Bd., p,415 6. iSdw. p, Kern, Chem. & Met., Vol.18, p.507 7. Hoffman, Metallurgy of Copper, 1915 Ed., p.415 B. P. L. Antisell, Chem. & Met., Vol.18, p.423 9. Hoffman, Met. of Copper, 1915 Ed., p,434 10. E. A. Cappelen Smith, Chem. & Met., Vol.16, p.l62 11. Colin (j. rink, Chem. & Met., Vol.23, p.471 12. Sidney Cornell, Chem. & Met., Vol.24, p301 13. Arrigo Tedesoo, Cheiji. & Met., Vol 23, p.847 26 Part YII Index iJibliography p . 25 Oonolusions 22 Experimental 9 Pigure I 13 Figure II 17 Figure III 21 History 3 Introduction 1 Suggestions 23 tables I 12 tables II 15 Tables III 19