Corrosion assessment of lead anodes in nickel electrowinning

Due to their insolubility, lead and its alloys have always been candidates for anodes in electrowinning plants. However, corrosion problems associated with lead anodes cost millions of dollars for industries annually. Cast and rolled lead-silver and lead-calcium anodes were tested under typical nickel electrowinning conditions. Effects of sulfuric acid and chloride concentrations on overall corrosion performance of the anode materials were investigated. Moreover, oxygen evolution reaction rate and overpotential were determined for specific electrode materialsolution conditions. Galvanostatic experiments were performed so the actual conditions that the electrodes are exposed to were simulated. Corrosion rates of the electrodes were calculated using the discharge plateau recorded during OCP measurements following the galvanostatic experiments. SEM and XRD were used to study the correlation between the surface morphology of the electrodes, their phase composition and their corrosion rates.