Investigation on characteristics of anodic film formed on PbCaSnCe alloy in sulfuric acid solution

The electrochemical properties of the anodic films formed on PbCaSnCe and PbCaSn alloys at 0.9 V (versus Hg/Hg2SO4 electrode) in 4.5 mol/L sulfuric acid solution were investigated by linear sweeping voltammetry (LSV), ac voltammetry (ACV), electrochemical spectroscopy impedance (EIS), capacitance measurement and X-ray photoelectron spectroscopy (XPS) technology. Based on Mott–Schottky analysis, the effect of cerium on the semiconductor properties of anodic film is discussed as well in this paper. The experimental data shows that cerium can significantly decrease the impedance of the anodic film on PbCaSn alloy, and can improve the corrosion resistance of the alloy. It can be inferred from the capacitance measurement result that the passive film should be an n-type semiconductor. The addition of cerium can decrease the slope of M–S plot, which indicates the increasing of defect density in the film, and this can contribute to improve the conductivity of the anodic film on PbCaSn alloy. XPS results shows that the anodic film formed on PbCaSnCe alloy is consisted of PbO1+x (0 < x < 1) and PbSO4, while for the anodic film formed on PbCaSn alloy, PbO and PbSO4 are the major component. Considering the better conductivity of PbO1+x (0 < x < 1) than that of PbO, it is concluded that PbCaSnCe may serve as the candidate of the new grid material for maintenance-free lead acid battery.