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https://hdl.handle.net/2142/25697
Description
Title
The anodic oxidation of metals
Author(s)
DeSmet, Donald John
Issue Date
1967
Doctoral Committee Chair(s)
Bartlett, J.H.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
anodic oxiation
passive iron electrodes
overpotential parameters
neutral electrolyte
Language
en
Abstract
"OptiGa~ mefislH;oementl;i 01; anoMc oxide su:r~ace layers on
passive i;ronelectJ;'Qc;les hav~ been made anQ are cqmpared with electrica1
mealill,ll:eJ;llent;s qf 'One q~paci\:anQ~ and other overpqteQ.tia1
parameters ~ Re.su1ts of t:hes~ st1,ldies snow that the surface layer on
the electrQde may be t""egarqed as ~onsistil1g of more than one part.
Specifically in a neutral e~ect:rQlyce there is a thin conducting
layer oJ constant thic~ness present on the electrode surface in
addition to the electrically limiting layer of variable thickness~
while in acid electrqlyte there is a layer located outside the electrical1y
limibing layer which grows at a constant rate to large
thicknesS when the ehctr()de h held, in the ""steady state"" in the
~assive region. This thick layer can be removed by holding the
electrode at a potential sl~ghtly below the passive region. Changes
in the thickness of the electrically limiting layer, determined opti~
cally are consisten~ with a field dependent conduction mechanism.
Optical and electical measurements during the anodic oxidation of nickel have also been made: The results of these measurements indicate that the behavior of passive nickel is more complicated
than that of passive iron. Electrical results show that the form of
the equation relating the current to the potential is of the same
form as it is for passive iron, however for nickel the behavior of
the parameters in this equation is found to differ significantly from
that of iron at higher passivaring potentials. Optical measurements
indicate that a layer or layers form on the nickel electrode surface
when it is made passive, however the optical parameters do not behave
in as simple a manner as they do for iron and it is impossible to
analyze the data uniquely.
The anodic oxidation of tantilum was studied by analyzing
open· circuit transients applied at intervals along galvanostatic
oxidation transients, The dependence of the c4rrent density, i, on
the overpotential, V, is expressed in an equation of the form i =
io exp(V/vo), and values are given for io and Vo' Under galvanostatic
conditions the parameter Vo varies linearly with the potential of the
electrode, while 10 is found to depend on the oxidation current
density. These results show strong similarities to results obtained
by others for the anodic oxidation of iron in a neutral electrolyte."
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