Effect of boric acid on corrosion and electrochemical performance of Pb-0.08% Ca-1.1% Sn alloys containing Cu, As, and Sb impurities for manufacture of grids of lead-acid batteries

The electrochemical performance of lead-acid batteries made of Pb–Ca–Sn alloys with and without 0.1% of each of Cu, As, and Sb individually and combined in 4.0 M H2SO4 in the absence and presence of 0.4 M H3BO3 was studied. Both impurities and H3BO3 were found to reduce the corrosion rate. Cyclic voltammetry revealed that the presence of impurities or H3BO3 significantly retarded the formation of large crystal PbSO4. H3BO3 increased the rates of oxygen and hydrogen evolution reactions for all alloys. Impedance measurement was used to quantify the amounts of PbSO4 and PbO in the initial stage of the oxidation. H3BO3 decreased the positive grid corrosion of all alloys, while impurities increased it. Although impurities increased the self-discharge during constant current discharge, H3BO3 was found to decrease it, except for the alloy containing the 3 impurities and the Cu-containing alloy. Under open-circuit conditions, H 3BO3 increased significantly the self-discharge rate, but impurities were found to suppress it.