Effect of Mn2+ on the anodic film and corrosion behavior of Pb-Ca-Sn alloy anode in copper electrowinning

Abstract

In this paper, the effect of Mn2+ (≤160 mg/L) on the anodic film properties and corrosion behavior of Pb-0.07%Ca-1.25%Sn anodes in acidic CuSO4 electrolyte is clarified. The anode was polarized in an electrolyte containing different concentrations of Mn2+ ions for 48 h to obtain a stable oxide film on the surface. The phase composition and morphology of the oxide layer formed on the Pb-0.07%Ca-1.25%Sn anode after polarization were characterized by the XRD, SEM, and EDS techniques. The influence of Mn2+ (≤160 mg/L) on the electrochemical behavior of the Pb-0.07%Ca-1.25%Sn anode was investigated in 45 g/L Cu2+ and 180 g/L H2SO4 solution via cyclic voltammetry, galvanostatic polarization, Tafel, and EIS measurements. In addition, the anodic weight loss, film formation, and corrosion mechanism of the anode are also proposed. The results reveal that the film formed on the Pb-0.07%Ca-1.25%Sn anode exhibited a gradient Pb|PbSO4|α-PbO2|α-PbO2-β-MnO2 layer in the Mn2+-containing electrolytes. Then, during the oxygen evolution reaction (OER), the gradient layer was oxidized to MnO2, which was irregularly attached to the surface of the substrate and increased the roughness of the film. The presence of Mn2+ accelerated the corrosion of the anode in the electrolyte and reduced the anodic oxygen evolution potential. When the concentration of Mn2+ ions reached 160 mg/L, the corrosion rate was increased by 62.3% despite the anode potential decreasing by 30 mV.