The anodic film studied was formed on Pb + 9 at. % Bi at 0.9 V (vs. Ag/Hg2SO4) in 4.5 M H2SO4 solution (25 degrees C). The change of the phase composition of the anodic film during reduction at -0.91 V (vs. Hg/Hg2SO4) (slightly more positive than that of the reduction potential of PbSO4) was determined by X-ray diffraction (XRD). The experimental results show that the crystals of PbO.PbSO4 and t-PbO in the anodic film can be reduced, but Bi2O3 crystals cannot. However, Bi2O3 crystals can be reduced when PbSO4 crystals are cathodically reduced. The existence of bismuth in alloy increases the corrosion rate of lead. The current-time transient shows that the process of reduction is limited by three-dimensional growth of circular cones with progressive nucleation when the potential is stepped from 0.9 to -0.91 V for the anodic film on Pb + 9 at. % Bi, but for a thicker film it is also controlled by ion transport through the film. The PbSO4 film formed on Pb is denser than that on Pb + 9 at. % Bi. The reduction process of the anodic film on Pb cannot be described by a simple nucleation and growth mechanism.