THE STUDY OF ELECTROCHEMICAL PROPERTIES OF PBO FILM ON LEAD IN H2SO4

Potentiostatic oxidations and potentiodynamic sweep of lead in H2SO4 were performed in the potential range between -1200 and +600 mV (with respect to the Hg/Hg2SO4 electrode). It has been found that three peaks of cathodic reduction on the cathodic sweep curve appear at -1000, -870, and about -800 mV, respectively. The peak at -800 mV is the reduction peak of tetragonal PbO which is formed at the potential positive to -550 mV. After the electrode is passivated, the oxidation of Pb to tetragonal PbO becomes the main process in the growth of anodic layer. The peak at -870 mV is the reduction peak of basic lead sulfates. This peak and the peak of oxidizing Pb to PbSO4 in the cathodic sweep overlap. The reduction of basic lead sulfates may be performed by a mechanism of the dissolution-deposition.