The growth of oxide layers on lead and its alloys at a constant potential in the PbO 2 potential region at different temperatures

Abstract

The growth of dense oxide layers on Pb, PbCa and PbCaSn alloys and a low-Sb (0.85%) alloy is sulphuric acid solutions follows a parabolic rate law at a constant potential in the PbO 2 potential region. This proves that the oxidation rate is controlled by a diffusion process. In the case of antimonial alloys with a higher Sb content the parabolic rate law cannot be applied during the early part of the oxidation, which is probably due to the addition reactions of the PbSb eutectic and the precipitated Sb particles. Compared to pure Pb all the alloying agents studied increase the effective rate constant and decrease the activation energy of the oxidation at a constant potential. These effects may be due to an increase in the concentration of oxygen vacancies in the oxide layer, changes in the electronic conductivity of the layer or an increased contribution of grain boundary corrosion.