A Study on Corrosion of Cast-On-Strap Alloys

The effects of different Sn or Se content on the corrosion behavior of lead-Sn or Pb-Sn_Se alloy in sulfuric acid solutions were investigated by metallurgical microscope, SEM, and weight loss tests. It was found that the addition Sn acts as grain coarser, but Se acts as grain refiner and Pb-Sn-Se alloys feature smaller grains. SEM for the corrosion layer indicated that the intergranular corrosion occurs on the surface of alloys with high Sn content (>1.wt%), but the general corrosion occurs on the surface of Pb-Sn alloys with low Sn content (<1.wt%) and all Pb-Sn-Se alloys. And The structure of corrosion layer and the eroded degree are relative to the height of the strap alloys above the plate. And the I cm strap alloy above the plate was cathodically protected and almost no corrosion problems appeared. The corrosion rate of alloys containing Se is lower than Pb-Sn binary alloys. And the higher of Se content, the lower of corrosion rate. The results demonstrated that Pb-Sn-Se alloys show the potential for application as the negative strap in VRLA batteries.