EFFECT OF BISMUTH ON THE CORROSION BEHAVIOR OF LEAD IN SULFURIC-ACID

To determine the maximum tolerable level of bismuth in lead/acid battery grid manufacture, a series of anodic corrosion experiments is carried out under conditions closely simulating those experienced in the positive-plate grid of an operative lead/acid battery. Weight loss is taken as a measure of the corrosive destruction of a series of binary lead-bismuth alloys with bismuth contents up to 2300 ppm. The results reveal the crucial role of both bismuth itself and the metallurgical structure (e.g., grain size) of the alloy. In particular, the alloy composition determines both the mechanism and the kinetics of the corrosion process. Long-term exposure tests show that the resistance to corrosion is significantly reduced at bismuth concentrations above 200 ppm.