Effect of quenching after solidification on hardness and electrochemical behavior of a Pb-0.09%Ca-1.23%Sn alloy

This work studies the effect of water spraying process as a quenching method on hardenability and initial electrochemical properties of a Pb-0.09%Ca-1.23%Sn positive grid alloy through a statistical approach. The nozzle diameter, quenching temperature and aging time are considered to have an impact on the alloy hardness whereas two first factors are believed to account for electrochemical behavior. Response surface method (RSM) is used to design the experiments and analyze the data. The results show that the quenched specimen acquires an acceptable hardness at initial aging time so that its hardness is higher than the air-cooled sample after a 4-day aging at room temperature. From statistically analyzing the data, it has been found that aging time increases the hardness although the water temperature and the nozzle diameter in the studied range have no considerable effect. In addition, no significant change in PbSO4/PbO2 and oxygen evolution potential of the alloy is observed with water spraying, however, a decrease in passivity current density is pronounced as a consequence of lowering water temperature.