The behaviour of lead and lead-silver alloy anodes during oxygen evolution in H2SO4-ZnSO4 or H2SO4-ZnSO4-MnSO4 electrolytes, has been studied by electrochemical impedance spectroscopy. A reaction model of anodic processes is presented, which quantitatively fits the experimental data. It is concluded that the presence of silver in lead modifies both the kinetic parameters of the main reaction of oxygen evolution, and the potential dependence of the oxide layer conductivity. It is also shown that the reaction of oxygen evolution is inhibited by a silver salt adsorbate. The electrode coverage by this adsorbate appears to be increased in the Mn2+-containing electrolyte, thus changing the inhibition into a passivation process.