Anodic behavior and microstructure of Al/Pb-Ag-Co anode during zinc electrowinning

ZHANG Yong-chun(张永春)¹, CHEN Bu-ming(陈步明)¹ , YANG Hai-tao(杨海涛)¹, HUANG Hui(黄惠)¹, GUO Zhong-cheng(郭忠诚)^{1, 2}

(1. Faculty of Metallurgy and Energy Engineering, Kunming University of
Science and Technology, Kunming 650093, China;
2. Kunming Hendera Science and Technology Co. Ltd, Kunming 650106, China)

Abstract:In order to study the anodic behavior and microstructures of Al/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy (SEM) and X-ray diffraction（XRD）analyses, the mechanism of the anodic processes playing on the surface of Al/Pb-0.8%Ag and Al/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured. On the basis of the cyclic voltammograms obtained, information about the corrosion rate of the composite in PbO₂ region has been concluded. The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO₄, but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO₄ concentrated in the certain zones after 24 h of anodic polarization. It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO₂ and PbSO₄ and α, β-PbO₂ penetrated into which, in fact, are the active centers of the oxygen evolution after 24 h of anodic polarization.

Key words:Al/Pb-Ag-Co anode; zinc electrowinning; potentiodynamic investigation; corrosion rate