The influence of tin and silver as microstructure modifiers on the corrosion rate of Pb-Ca alloys in sulfuric acid solutions

Abstract

The effect of microstructure modifiers, Sn and Ag, on the corrosion rate of commercial Pb–Ca alloy in H2SO4 electrolyte was investigated by the potentiodynamic polarization and by the weight loss corrosion rate measurement at the open circuit potential. The effect of microstructure modification of the Pb–Ca alloy, provoked by the alloying with tin and silver as well as by the proper thermo-mechanical treatment, is recorded by optical microscopy. The weight loss experiments have shown three- to five-fold decreases in the corrosion rate of ternary Pb–Ca–Sn and quaternary Pb–Ca–Sn–Ag alloys, compared to the results for primary Pb–Ca alloy. It is largely in accordance with the results of potentiodynamic polarization measurements that showed comparable decrease in the passive current density of the modified alloys. The obtained results are discussed in terms of the synergetic effect of the addition of modifiers and the thermo-mechanical treatment on to the Pb–Ca alloy microstructure refinement, and accordingly the increase in their corrosion resistance.