Anodic Behavior and Corrosion Resistance of the Pb-MnO2 Composite Anodes for Metal Electrowinning

In this study, integrity and corrosion properties of the Pb-MnO2 composite anodes fabricated through single-action powder pressing were investigated. The effects of the MnO2 content on the properties of the composite anodes were studied and compared with those of the Pb and Pb-Sn-Ca anodes. Galvanostatic experiments (50 mA/cm(2)) were performed in stagnant sulphuric acid solution at 37 degrees C for the durations of 24 and 72 hours. The results indicated that the Pb-MnO2 anodes operated at lower potentials than the Pb-Sn-Ca anode. The electrocatalytic activity of the composite anodes was improved as their MnO2 content increased, however, high MnO2 contents resulted in electrochemically unstable anodes. The composite anodes showed a lower degradation rate and better corrosion resistance compared to the Pb-Sn-Ca anode. Surface morphology and structure of the anodic layer on the anodes were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Barrier properties of the anodic layer on the electrodes were investigated through cyclic voltammetric measurements. Results revealed that formation of the surface anodic layer was enhanced on the Pb-MnO2 anodes. The anodic layers formed on the composite anodes in 72-hour polarization were more compact than that of the Pb-Sn-Ca anode and provided higher levels of protection. (C) 2013 The Electrochemical Society. All rights reserved.