Influence of Sn Content on the Corrosion Behavior of Pb–Ca–Sn Alloys in High-Temperature Sulfuric Acid Solution

Abstract

Pb-0.08 mass%Ca–Sn alloys with a wide range of Sn contents were prepared, and then immersed in 4.50 kmol m−3 H2SO4 at 348 K to elucidate the influence of Sn content on their corrosion behavior. Under natural immersion, the corrosion current of the Pb–Ca–Sn alloys is governed by the cathodic reaction, which involves the consumption of dissolved oxygen. The anodic reaction consists mostly of PbSO4 formation and Sn dissolution. For the Pb–Ca–Sn alloys with 0∼0.2 mass%Sn, 99% of the anodic current is used in the former reaction. The formation of the sulfate, which is noticeably fragile and low in strength, can be assumed to be one cause for the serious corrosion damage to the low-Sn alloy grids in high-temperature sulfuric acid solution. On the other hand, the current for the PbSO4 formation decreases linearly with increasing Sn content in the alloys at about 0.3 mass% Sn or more. For the high-Sn alloys such as Pb-0.08 mass%Ca-1.2 mass%Sn, the ratio of PbSO4 formation to the anodic current is lowered by the Sn content, and the mechanical strength may be maintained at a high level to prevent serious corrosion.