Abstract
The methode based on the conductance measurement of the metallic film electrode, called the resistmetry, was applied to the galvanostatic oxidation and reduction of Zn and Sn in a neutral borate buffer solution of pH 8.39. An analysis was made on the conductance- and potential-coulomb diagrams. The results are summarized as follows:
The anodic oxide film on Zn was ascertained as Zn(OH)2, which was formed by anodic oxidation and reduced to metallic Zn by cathodic reduction both with 100% current efficiency. The potential arrests of the anodic and cathodic chronopotentiogram, which corresponds to the reaction
(This article is not displayable. Please see full text pdf.)
\
oindentdepended on the current density following to the Tafel relation. It was found from the results that the equilibrium potential of the reaction is −1.16 V at which the apparent exchange current density is 10 μA/cm2. By anodic oxidation, Sn was covered with the SnO film at first, and, when the thickness of the film reached a certain value, it started to dissolve as Sn (IV) ion. During the anodic dissolution, the SnO layer was kept at a constant thickness. SnO was cathodically reduced to metal completly. The current efficiencies of both the anodic oxidation and the cathodic reduction were found to be close to 100%. It was proved that the resistmetry could be successfully used as an in-situ methode for investigating anodic oxide films by combining with the coulometry.
