Influence of Mn 2+ on the performance of Pb-Ag anodes in fluoride/chloride-containing H 2 SO 4 solutions

In this study, surface morphology, inner structure and phase composition of anodic layers on Pb-Ag anode in fluoride/chloride-containing H 2 SO 4 solutions were investigated in the presence/absence of Mn 2 + . Additionally, corrosion morphology of metallic substrate and anodic potential variation of Pb-Ag anodes were studied as well. The influence of Mn 2 + on the anodic layer property and corrosion behavior of Pb-Ag anodes in fluoride/chloride-containing H 2 SO 4 solutions was then clarified. The results revealed that in the presence of Mn 2 + , anodic layer consisted of an external layer in MnO 2 /PbO 2 -PbSO 4 /MnO 2 structure and an inner layer adhering to the metallic substrate. Due to the coverage of an external layer, the corrosion of metallic substrate was relieved by the presence of Mn 2 + in fluoride/chloride-containing H 2 SO 4 solution. As was demonstrated, Mn 2 + decreased PbO 2 concentration in the inner layer, especially in fluoride-containing solution. In the presence of Mn 2 + , the anodic potential was higher than that in solutions without Mn 2 + due to larger thickness and resistance of anodic layer. In addition, the anodic potential was characterized by oscillation in Mn 2 + -containing solution, indicating low stability of anodic layer. Comparatively, the anodic layer formed in the presence of Mn 2 + and chloride ion was more stable than that in solutions containing Mn 2 + and fluoride ion.