THE BEHAVIOR OF LEAD ELECTRODES IN SULPHURIC ACID SOLUTIONS

Abstract

Lead electrodes were anodically etched in NH2SO3H. Immersion potentials, self-passivation potentials, passivation times, PbO2/O2 potential, and the potential of the first discharge plateau were determined in H2SO4 solutions ranging from 0.5 to 20.0 N and were found to be concentration-dependent. Interruption of the anodizing current had no detectable influence on passivation time. Data obtained with the anodizing current turned on fall into three categories; those obtained with (1) short-immersion anodes, (2) anodes which had reached a hydrogen-like potential, and (3) anodes which were self-passivated before the current was switched on. An inflection in the relation between potential and time during charging was investigated. Its length was dependent upon acid concentration and current density, while its potential was +300 ± 30 mv, and seemed to correspond to the self-passivation potential. The lengths of the first and second discharge plateaus increased with the number of coulombs passed and were dependent upon acid concentration, but were identical for electrodes treated by four different methods. The hydrogen-like potential appeared to be due to the presence of PbO•PbSO4. The self-passivation potential seemed to be caused by formation of PbO.