EFFECT OF SILVER CONTENT IN Pb-Ag ANODES ON THE PERFORMANCE OF THE ANODES DURING ZINC ELECTROWINNING

The efficiency of the electrowinning process of zinc depends on the performance of oxygen evolution reaction, anode quality and corrosion resistance of lead anodes. The original surfaces of rolled commercial lead-silver anodes were examined using conventional polarization methods in acid zinc sulfate electrolyte with MnSO(4) at 38 degrees C. The self-discharge method (potential decay) following 5 hours of polarization at 50 mA.cm(-2) was considered to evaluate electrochemical activity, oxygen overpotential and anode stability. The influence of silver content is compared to that of the microstructure, the fabrication process and the composition of the corrosion products. Polished anode samples have also been examined for microstructural and corrosion performance studies. The experiments show that the duration of the plateau at 1600 mV/SHE, the potential level (active corrosion state/corrosion potential region) and the rate Delta E(corr)/Delta t during the decay could be a good indicator to compare the corrosion rates of the anodes in industrial zinc electrolytes.