Oxygen evolution and corrosion behavior of low-MnO2-content Pb-MnO2 composite anodes for metal electrowinning

In this study, the oxygen evolution and corrosion behavior of Pb-MnO2 composite anodes produced by powder pressing with low MnO2 content (1-7 wt%) were systematically investigated in H2SO4 solution and compared to pure Pb and Pb-Ag (1 wt%) anodes. Galvanostatic polarization, weight loss, and ionic equilibrium techniques were employed to evaluate the electrocatalytic activity and corrosion resistance of the composite anodes. The results demonstrated that Pb-MnO2 composite anodes presented lower potential than that of the Pb-Ag anode during a 72 h polarization period, and the potential of composite anodes decreased as MnO2 fraction increased. The corrosion resistance of composite anodes was higher than that of the Pb-Ag anode. The surface morphology and phase composition of the anodic layer after 72 h polarization were examined with scanning electron microscopy (SEM) and X-ray diffraction (XRD) and the results indicated that anodic layers on Pb-MnO2 composite anodes were both thinner and denser than that of the Pb-Ag anode, confirming excellent corrosion resistance in H2SO4 solution electrolysis. (C) 2015 Elsevier By. All rights reserved.