The electrochemical processes related to the passivation of Pb in 5 M H2SO4 at 25°C, have been investigated combining a rotating ring-disk electrode, linear potential sweep voltammetry and potentiostatic pulse techniques complemented with scanning electron microscopic imaging. The kinetics of PbSO4 anodic layer growth can be explained through the initial formation of a barrier layer acting as an ionic conductor, and the transference of Pb2+ cations from the substrate the conducting layer yielding Pb2+ ion in the solution. These ions further contribute to passivation through the precipitation of a PbSO4 passivating layer.