Potentiostatic studies of the influence of temperature on lead-silver anodes during electrowinning and decay period

Abstract

ABSTRACTThe electrochemical behaviour of the Pb-0.7% Ag anode has been investigated in zinc sulphuric acid electrolyte containing 5, 8, 12 g/L Mn2+ by electrochemical measurements at different temperatures of 35°C, 40°C, 45°C. It was observed by cyclic voltammetry before electrolysis that temperature increase from 35°C to 45°C resulted in a decrease in the oxidation peak I (Pb → PbSO4) and an increase in the oxygen evolution peak II (2H2O → O2 + 4H+ + 4e). At 2.01 V/SHE, the current densities of Pb-0.7% Ag anode in sulphuric acid solution containing 8 g/L Mn2+ at 35°C, 40°C and 45°C increased from 26.5 at 35°C to 28.5 and 37.7 mA/cm2 at 40 and 45°C, respectively. In the presence of ZnSO4 addition to the sulphuric acid solution, the anodic current of oxygen evolution at 2.01 V/SHE decreased by ∼ 18% at 40°C. After 2 h of potentiostatic polarisation in the presence of zinc sulphate addition at 2.01 V/SHE, electrochemical Noise Measurements showed that the admittance (corrosion rate) of the Pb-0.7% Ag anode in the zinc electrolyte increased with the increase in temperatures during decay. This tendency was also confirmed by linear polarisation and impedance measurements.