Electrochemical behavior of mesh and plate oxide coated anodes during zinc electrowinning
(1. School of Metallurgical Engineering, Hunan University of Technology, Zhuzhou 412007, China;
2. Department of Mining, Metallurgy and Material Engineering, Laval University, Ste-Foy, Quebec G1K 7P4, Canada;
3. Hydro-Quebec Research Center, Shawinigan, Quebec G9N 7N5, Canada)
2. Department of Mining, Metallurgy and Material Engineering, Laval University, Ste-Foy, Quebec G1K 7P4, Canada;
3. Hydro-Quebec Research Center, Shawinigan, Quebec G9N 7N5, Canada)
Abstract: The catalytic performance of two oxides coated anodes (OCSs) meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 °C. Their electrochemical behaviors were compared with that of a conventional Pb-0.7%Ag alloy anode. Electrochemical measurements such as cyclic voltammetric, galvanostatic, potentiodynamic, open-circuit potential (OCP) and in situ electrochemical noise measurements were considered. After 2 h of OCP test, the linear polarization shows that the corrosion current density of the Ti/(IrO2-Ta2O5) mesh electrode is the lowest (3.37 μA/cm2) among the three OCAs and shows excellent performance. Additionally, after 24 h of galvanostatic polarization at 50 mA/cm2 and 38 °C, the Ti/MnO2 mesh anode has the highest potential (1.799 V), followed by the Ti/(IrO2-Ta2O5) plate (1.775 V) and Ti/(IrO2-Ta2O5) mesh (1.705 V) anodes. After 24 h of galvanostatic polarization followed by 16 h of decay, the linear polarization method confirms the sequence obtained after 2 h of OCP test, and the Ti/(IrO2-Ta2O5) mesh attains the lowest corrosion current density. The Ti/(IrO2-Ta2O5) mesh anode also shows better performance after 24 h of galvanostatic polarization with the overpotential lower than that of the conventional Pb-Ag anode by about 245 mV.
Key words: oxides coated anode; mesh; plate; electrochemical measurement; electrochemical behavior