The effect of cooling rate after casting on the electrochemical and mechanical properties of Pb-Sn-Ca alloys used as positive grids in lead–acid batteries
Many attempts have been made to modify the manufacture and chemical composition of grid alloys used in lead–acid batteries. The main objective is a grid with decreased weight, higher corrosion resistance and lower-cost that will support longer battery lifetime. This campaign led to the development of Pb-Ca-Sn grid alloys. These alloys have improved mechanical properties due to the presence of tin of the alloy and are also considerably resistant to corrosion at elevated temperature. On the other hand, whereas decreasing the calcium content has been found to enhance significantly the corrosion resistance and reduce water consumption, it deteriorates the mechanical properties with consequent softening the grid and a decline in production efficiency. This presentation reports the findings of a study to achieve two outcomes ― corrosion resistance and high production efficiency ― through the influence of a quenching process using water sprayed on a Pb-0.08% Ca-1.2% Sn alloy. The nozzle diameter, quenching environment temperature and ageing time were believed to affect hardness, while two first factors were considered to account for corrosion resistance. A response surface method (RSM) was employed to design and monitor the experiments. The ranges of the nozzle diameter, cooling temperature and ageing time were 2 –4 mm, 15–25 °C and 0–4 days, respectively. The Brinell hardness value was measured for samples produced under various conditions. Cyclic voltammetry and potentiostatic polarization techniques were used to evaluate the corrosion resistance and water consumption properties of the alloys. The resulting data were analyzed using Design Expert software and then compared with that obtained for an air-cooled sample. It was found that water spraying promotes the ageing process of Pb-Ca-Sn alloy and thereby a higher hardness value can be obtained in a short aging time with respect to the air-cooled sample. Whereas water quenching has no effect on the formation potential of PbO2, it slightly increases the water oxidation potential and improves the corrosion resistance when quenching at low temperature with large nozzle diameter.
Ali AsgharAlagheband Hosseini holds a BSc and a MSc from Iranian institutions. Between 2006 and 2018, he was the Director of the Process Engineering Department at the Nirougostaran Khorasan Company, the largest SLI battery manufacturer East of Iran. He is currently the Technical Manager of the Sarv Sanat Toos Co.