Electrochemical properties of Pb-Sb, Pb-Ca-Sn and Pb-Co3O4 anodes in copper electrowinning

Three types of anode, Pb-Sb, Pb-Ca-Sn and Pb-Co3O4, for copper electrowinning were investigated. The corrosion resistance, as evaluated by cyclic voltammetric (CV) measurements was higher for Pb-Co3O4 than for Pb-Sb and Pb-Ca-Sn. During prolonged electrowinning under galvanostatic conditions, the anodic reaction on the Pb-Co3O4 anode was depolarized by 0.053 V as compared to Pb-Sb, and by 0.106 V with respect to Pb-Ca-Sn. The composition and structure of the anodic layer were determined by XPS, X-ray and SEM analyses. The surface layer on the three anodes examined was composed mainly of PbSO4, alpha-PbO2 and beta-PbO2. Different structure of the surface layer was observed: loose and highly spread coral-like structure in the case of Pb-Sb; fibrous structure in the case of Pb-Ca-Sn and dense, fine-grained structure in the case of Pb-Co3O4.