ROLE OF MINOR ALLOYING ELEMENTS ON THE PERFORMANCE OF LEAD-ACID-BATTERY GRIDS .1. CORROSION OF PB-SE ALLOYS

The corrosion behaviour of Pb-Se alloys (Se: 0.00, 0.01, 0.04 and 0.06 %) to be used in the manufacture of grids for pasted lead-acid batteri es, was studied under open circuit, potentiostatic and galvanostatic p olarization in 5.0 M H2SO4 solutions. Selenium was found to shift the corrosion potential to more negative values and increase the sulfation and self-discharge; the extent being dependent on the percentage of s elenium. The potentiostatic E/log i curve was significantly influenced , especially the passivity region from -0.90 to +1.30 V vs Hg/Hg2SO4 ( 1.0 M H2SO4), where the passivity current and the critical current and potential to start the nucleation of PbSO4 decreased in the presence of selenium. Both oxygen and hydrogen evolution overpotentials were fo und to be higher for the alloys containing selenium. In many aspects, the alloy composition Pb-0.04% Se was found to be critical. Factors af fecting the constant current charging; the charging time, temperature and the number of charging-discharging cycles, N, were investigated. G enerally, the corrodability of Pb-Se alloys was relatively higher and increasing N was found to increase corrosion in the order: Pb-0.04% Se > Pb-0.01% Se > Pb-0.06% Se > Pb. As the charging time increased, the rate of corrosion decreased for Pb-Se alloys while it was constant fo r Pb.