STUDIES ON THE ANODIC AND CATHODIC POLARIZATION OF LEAD IN SODIUM-SULFATE SOLUTION

Galvanostatic polarization of lead has been studied in 0.1 M Na2SO4 so lutions at various current densities. It was found that, at relatively low current densities, the anodic polarization curve does not reach t he oxygen evolution potential. This indicates that the anodic dissolut ion of lead could continue indefinitely at these rates. At high curren t densities, the anodic polarization curve is characterized by four di stinct arrests corresponding to the formation of PbSO4, PbO, PbOn and PbO2, respectively, followed by transformation of PbSO4 to PbO2 on the electrode surface before the evolution of oxygen. The cathodic reduct ion curve shows three distinct plateaux corresponding to the transform ation of PbO2 to PbSO4, PbO2 to PbO and the latter with PbSO4 to spong y lead, successively, followed finally by the formation of PbH2. The c orrelation between the current, i, and the passivation time, t, for le ad in 0.1 M Na2SO4 solution was found to follow the relation: log t = A - nlog i, where A and n are constants. The diffusion and migration o f the SO42- and Pb2+ ions through the micropores of the anodic film be come the controlling step. (C) 1998 Elsevier Science S.A. All rights r eserved.