*
i
.
| OF 1
ORNL P
862
'-
More
i
.
.:-
U
.
*
i
:
.!
the
..
* ..,.
.
SO!
:1
M
OS
bull
113.6
rif
01.25 1.1.4 16
MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS – 1963
This paper was submitted for publication
in the open literature at least 6 months
prior to the issuance date of this Micro-
card. Since the U.S.A.E.C. has no evi-
dence that it has been published, the pa-
per is being distributed in Microcard
form as a preprint.
!--
-
*
i
.
a
-,.
.
.
.
.
.
.
i
-
,
tome
...
.
.:. ..
.--
LEGAL NOTICE
This report was prepared as an account of
Government sponsored work. Neither the
United States, nor the Commission, nor any
person acting on behalf of the Commission:
A. Makes any warranty or representa-
tion, expressed cr implied, with respect to
the accuracy, completeness, or usefulness
of the information contained in this report,
or that the use of any information, appa-
ratus, method, or process disclosed in this
report may not infringe privately owned
rights; or
B. Assumes any liabilities with respect
to the use of, or for damages resulting from
the use of any information, apparatus,
method, or process disclosed in this report.
As used in the above, “person acting on
behalf of the Commission” includes any em-
ployee or contractor of the Commission, or
employee of such contractor, to the extent
that such employee or contractor of the
Commission, or employee of such contractor
prepares, disseminates, or provides access
to, any information pursuant to his employ-
ment or contract with the Commission, or
his employment with such contractor.
r
Y
:
-
-
-.
.
.-
.
-
:
.
.
.
ORNU -B-862
-
LOTIES
JAN 2 1965 CONF-150502-).
ROTATING DISK STUDY OF THE DISSOLUTION OF ZIRCONIUM IN HF-H,SO,
R. E. Meyer and Sandra Zetti
Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
Bano
* Research sponsored by the U. S. Atomic Energy Commission under con-
tract with the Union Carbide Corporation.
The dissolution of' crystal bar zirconium in mixtures of hydro-
fluoric acid and sulfuric acid has been investigated by use of a rotat-
ing disk electrode system. The presence of the sulfuric acid in rela-
tively large amounts considerably reduces the rates as compared to
solutions of hydrofluoric acid and nitric acid. In addition, the re-
action, which is normally first order, changes to second order in the
presence of large amounts of sulfuric acid. A kinetic equation which
accounts for these results can be derived if it is assumed that both
the hydrofluoric acid and the sultate ion are adsorbed.
.

This paper was submitted for publication
in the open literature at least s months
prior to the ideuance date of this Micro-
card. Since the U.S.A.E.C. has no evi-
dence that it has been publisher, the pa-
per is being distributed in Microcard
form as a preprint.
STISTRYONET E
non
ne time or comment Of I nterest
vader PROCEDURES ON FIE IN AESemme
montgeneem.mom

APPROVED FOR PUBLIC RELEASE
LEGAL NOTICE
TW, report no progurad u Ha account of Covenant spoord work, Nellber the Vallad
sut, vor the commissdoo, DoT any perro scuing on behal' of the Cralulon:
A. Makes my nrrualy or reprenautoa, expressed or impued, mw roupect to the accu-
ry, capiendo., or wolumen of the laforma uon contained a wis report, or what we we
of may tabornuallon, oppuritos, method, or rinisdikcloud laws report may bol lalring.
rinlely oned rou; or
2. Anm uy Habillues mu nopect to the son of, or for de mero reruung Iron ubo
w o un baloration, apuntwe, matbod, or proceu deloond la ws report.
Au du the above, "pornoo schoo l of the Commisslon" wcludes by @.
ploys or coulrector ol de Coanloom, or employ of such contriclor, to the oneat that
wch mal vyro or coatrator of the Cowalsstors, or employme of red contractor preparoi,
Mountates, on portar amato, uy l'oreuuou part bo vo sployant or contract
..t Vouwindler, or No aploganat nu euca contractor.


ROTATING DISK STUDY OF THE DISSOLUTION OF ZIRCONIUM IN HF-H SOL
R. E. Meyer and Sandra Zetti
Chemistry Division, Oak Ridge Netional Laboratory, Oak Ridge, Tennessee
ni
* Research sponsored by the U. S. Atomic Energy Commission under con-
tract with the Union Carbide Corporation
The dissolution of crystal-bar zirconium in mixtures of hydrofluoric
acid and sulfuric acid has been investigated by use of a rotating disk
electrode system. With normal methods of stirring, the rate of the reac-
tion is completely under mass transfer control, and the rate therefore
depends solely upon the concentration of undissociated hydrofluoric acid
in the solution. The use of the rotating disk allows the kinetic rate of
the surface reaction to be determined as a function of the potential and
the solution variables.
A previous investigation in which the rotating disk was used
showed that the surface reaction in solutions containing hydrofluoric and
nitric acids was first order with respect to undissociated HF and almost
independent of the potential. These results and other observations led
to the conclusion that the reaction involved the attack of the surface of
a film by the HF molecule and that the potential variations in the system
were entirely across the film.
The presence of the sulfuric acid in concentrations above about 0.1 M
considerably reduces the rate as compared to the experiments in the nitric
acid solutions. . In addition, the reaction order with respect to HF is
changed from unity to a value slightly below two. When the concentration
of the sulfuric acid is reduced to values below 0.1 M, then the rates of
the reaction and the order are essentially identical to those in mixtures
of HF and HNO3 of comparable concentrations.
the capacities of the electrodes were also determined as a function
of rotational velocity and potential as the electrode was immersed in the
various solutions. These measurements showed that the capacities had
values ranging irom about 3 to 15 UF/cm. These capacities were inter-
preted as meaning that a film was present on the surface of the electrode.
The relative thicknesses of the films were campared for various solutions
and the thickness was found to increase as the potential became more anodic
and as the concentration of HF was reduced. These trends were just what
would be expected if the dissolution proceeded by the continuous formation
and dissolution of a film.
A kinetic equation which accounts for these results can be derived
if it is assumed that both the Hi and the IL SOL are adsorbed on the sur-
face of the film. At high concentrations of H2SO4, the coverage by the
sulfate is large and tends to inhibit the coverage by HF. It can further
be shown that, if the attack by HF proceeds through an intermediate ad-
sorption step, then the reaction will change from first to second order
as the concentration of the sulfate is increased.
(1) R. E. Meyer, "Rotating Disk Study of the Dissoluüion of Zirconium in
HF-HNO2," submitted to the Journal of the Electrochemicel Society.
,
,*
-.
END
DATE FILMED
9/9/65
***;!
Tra.
.
..
-
-
A
S