The Rate of Solution of Metals in Acids as a Function of Overvoltage II. The Solution of Cadmium in Sulfuric Acid

Kimball, George E.; Glassner, Alvin

doi:10.1063/1.1750586

Cited by 5 publications

(11 citation statements)

References 6 publications

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“…Repeat tests with different electrodes (shown by the various points at each potential) show that this difference is statistically significant. This result is parallel to that found for Cu in dilute H2SO~ (11) but is unexpected in light of various other mixed potential systems (5)(6)(7)(8)(9). Other trends from Fig.…”

Section: Resultssupporting

confidence: 78%

“…In order for this superposition approach to function it is necessary that the rate and kinetics of each partial reaction be independent of the other partial reaction(s) at a given potential. This independence of partial processes has been shown for several combinations of reductant (metals or hydrogen) and oxidant (5)(6)(7)(8)(9), and consequently would appear to be quite general. However, independence of the partial processes is not a necessary criteria for charge and mass balance across the electrode-solution interface, as suggested in some previous work (10,12).…”

mentioning

confidence: 87%

“…Monovalent Cd + ions are never observed in sulfate solutions (as the present faradaic dissolution results in N~/H2SO4 reattest) and therefore exist only in the adsorbed state. In N2-saturated solution reactions [3] and [4] are negligible such that the steady-state rate of Cd dissolution is given by i(Cd, N2) ~---{(N2) = il +/2 = 2i2 [5] When O~ is present, reactions [3] and [4] also must be considered, which results in a steady-state electric current, i (O2), of i(O2) = il +/2 --i4 [6] and a Cd dissolution rate, R(Cd, O2) (in moles/seecm 2) , of R(Cd, 02) ~-R3 4-i2/F [7] Here R3 is the rate of step [3] in moles Cd/sec 9 cmz. Each time ii occurs, the resultant Cdad + ion is removed by step [2] or [3].…”

Section: Model To Explain Resltsmentioning

confidence: 99%

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Effects of Oxygen on the Mechanism of Cadmium Dissolution in Sulfate Solutions

Andersen

Ghandehari

Feng

et al. 1977

J. Electrochem. Soc.

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The dissolution rate of cadmium was measured in various nitrogen-and oxygen-saturated acidic sulfate solutions under potentiostatic conditions. At a given potential, the aissolution rate was found to be greater in O2-than in N2-saturated solutions. A dissolution mechanism is proposed which explains this phenomena as well as results from tests in which potential, solution agitation, and solution composition were varied. According to this mechanism Cd + ions are formed as intermediates and are then oxidized to the product Cd +2 ions by a chemical path involving O2 as well as by the conventional electrochemical path.Uniform corrosion of a metal in solution is most frequently explained in terms of the electrochemical polarization curves for the independent processes, i.e., metal oxidation and H + or 02 reduction [e.g., see Ref.(1-4)]. The polarization curves for the part reactions are added to yield that for the over-all system. This type of treatment is useful in explaining corrosion, passivation, and protection phenomena. It also has been recommended as a means for accelerated corrosion testing [e.g., Ref. (2,5)]. In the latter application the Tafel curves for one or both half-reactions (assuming one predominant cathodic and one predominant anodic reaction) are obtained by suppressing the opposite reaction. The Tafel curve is then extrapolated to the measured corrosion (mixed) potential or the two Tafel curves are extrapolated to the point of overlap to yield the corrosion current. The above superposition procedures are a means of replacing lengthy weight-loss or assay-dependent tests with one rapid electrochemical test. In order for this superposition approach to function it is necessary that the rate and kinetics of each partial reaction be independent of the other partial reaction(s) at a given potential. This independence of partial processes has been shown for several combinations of reductant (metals or hydrogen) and oxidant (5-9), and consequently would appear to be quite general. However, independence of the partial processes is not a necessary criteria for charge and mass balance across the electrode-solution interface, as suggested in some previous work (10, 12). Also an experimental attempt to obtain the corrosion rate of copper in oxygenated acid sulfate solutions by extrapolating the anodic copper polarization curve gave a corrosion rate which was erroneously low (11). ~ In the latter work (11) studies were made to determine why the partial processes were not independent when coupled, and a mechanism was proposed to explain the results.The present study was made to investigate other systems for which the partial processes are not independent, as part of an evaluation of the superposition means of accelerated corrosion testing. Cadmium in acidic sulfate solutions was the metal chosen for study because previous work (13) suggests it dissolves as Cd +2 ions via a Cd +1 intermediate; such an intermediate offers a vehicle for interactions between the part reactions. Both H + ions and O2 were studied as oxid...

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Section: Resultssupporting

confidence: 78%

mentioning

confidence: 87%

Section: Model To Explain Resltsmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Oxygen on the Mechanism of Cadmium Dissolution in Sulfate Solutions

Andersen

Ghandehari

Feng

et al. 1977

J. Electrochem. Soc.

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show abstract

“…

The problem of the dissolution of cadmium in various aqueous media has been investigated intermittently over the past two decades (2,3,4,5,7,8,9,10,11,12,13,14 and 15), the chief work being that carried out by Centnerszwer and coworkers. The published data appear to be at variance in several places, and in some cases are of doubtful validity.

…”

mentioning

confidence: 99%

“…Kimball and Glassner (12), when investigating the rate of solution of cadmium in sulfuric acid, found that the rate could best be expressed by a zero-order equation, and showed that this should be the order on a theoretical basis.…”

mentioning

confidence: 99%