The oxidation processes of lead sulphate in the anodic films on lead and Pb-5wt% Sb alloy, which were formed by the reduction at 0.9V (vs. Hg/Hg~2SO~4, the same reference electrode below) for 5min of the anodic films grown in a 4.5mol·dm^-^3 H~2SO~4 solution (30℃) at 1.3V for 20min, have been studied using potential step and a.c. impedance methods respectively. The experimental results show that the lead sulphate, which is formed by reducing lead dioxide, can be reoxidized to lead dioxide within 1min at 1.4V. This is due to the fact that this kind of lead sulphate is at the surface layers of the lead sulphate grains in the anodic film. The oxidation process of lead sulphate in the inner part of the grain, which is formed directly by anodizing lead, is much slower. The antimony in the lead alloy inhibits significantly the nucleation and growth of lead dioxide crystals.

Key words: LEAD, LEAD ANTIMONY ALLOYS, ANODIC OXIDATION, LEAD OXIDE, ANODIC FILM, LEAD SULFATE