✍ Scribed by D. Pavlov; T. Rogachev
No coin nor oath required. For personal study only.
When a Pb electrode, immersed in HzSO, solution, is polarized anodically in the PbO2 potential range the Pb/PbO~Z_,,lHz0/02/HIS01 electrode system is established. Oxygen is evolved at the oxidesolution interface The oxygen atoms formed as intermediates diffuse into the anodic layer and oxidize the metal. Through a solid-state reaction, the metal is oxidized first to ret-PbO and then to Pb02. By studying the changes in the rate-potential relations of the above reactions, as well as the phase and chemical composition of the anodic layer, it was possible to elucidate the effect of Ag and As on these processes. The additives were introduced into the electrode system either by alloying with lead or by dissolving them in the HISOI solution. When added to the solution, both Ag and As lower the overvoltage of the oxygen evolution reaction. They have practically no effect on the corrosion reaction under galvanostatic polarization conditions. If alloyed in the metal, Ag reduces the oxidation rate of Pb significantly, while As enhances it. Both additives lower the stoichiometric number of the anodic oxide layer, k they retard the oxidation of PbO to PbOl. The results of these investigations were used to develop further the model of the mechanism of the reactions proceeding during the anodic oxidation of lead in H,SO, solutions.
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