Electrochemical impedance spectroscopy and scanning electron microscopy have been utilized to investigate the mechanism of reactions taking place on Pb and PbAg alloy anodes in acidic zinc sulphate electrolytes, during the formation of PbSO 4 layers in the potential domain (0.9 to 1.1 V/SSE). Independent of the Ag content, the anode behaviour is essentially determined by the electrolysis time. From a comparison of experimental data to a kinetic model for the frsol| Pb/ PbO n / PbSO 4 electrode, it is shown that the layer growth is first controlled by the solid state diffusion of SO 2− 4ions, and then by a chemical step associated with a change in charge carriers, from O 2+ v vacancies in the PbO n sublayer into Pb 2+ions in the PbSO 4 layer. In Mn 2+-containing electrolytes, the additional formation of MnO 2 occurs under diffusion control of the Mn 2+ oxidation, and it modifies both the layer properties and the kinetics of reactions.