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

Authors: SAID SALIH, AHMED GAD-ALLAH, ASHRAF ABD EL-WAHAB, HAMID ABD ELRAHMAN

Abstract: 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 H_2SO_4 in the absence and presence of 0.4 M H_3BO_3 was studied. Both impurities and H_3BO_3 were found to reduce the corrosion rate. Cyclic voltammetry revealed that the presence of impurities or H_3BO_3 significantly retarded the formation of large crystal PbSO_4. H_3BO_3 increased the rates of oxygen and hydrogen evolution reactions for all alloys. Impedance measurement was used to quantify the amounts of PbSO_4 and PbO in the initial stage of the oxidation. H_3BO_3 decreased the positive grid corrosion of all alloys, while impurities increased it. Although impurities increased the self-discharge during constant current discharge, H_3BO_3 was found to decrease it, except for the alloy containing the 3 impurities and the Cu-containing alloy. Under open-circuit conditions, H_3BO_3 increased significantly the self-discharge rate, but impurities were found to suppress it.

Keywords: Pb--Ca--Sn alloys, lead-acid batteries, recycled lead, boric acid

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