The role of electrolyte hydrodynamic properties on the performance of lead-based anodes in electrometallurgical processes

Integrity of lead anodes has always been a major concern for the electrowinning industry. This work investigates the effect of solution hydrodynamics on the degradation of Pb-Sn-Ca and Pb-Ca anodes. Galvanostatic experiments (50 mA/cm²) were performed at 37 ± 0.5°C using 0, 600, and 1000 rpm stirring rates for the durations of 24 and 72 hours. The PbO₂ layer was reduced to PbSO₄ (discharged) and the discharge duration was used in corrosion rate calculations. Weight loss measurements along with the discharge calculations revealed that the degradation rate of lead anodes increased with the solution stirring rate. In addition, the amount of PbO₂ remaining on the surfaces was decreased as a function of solution velocity. Therefore, it was concluded that detachment of the corrosion products from the surface (flaking) affects the degradation rate of lead anodes significantly. Moreover, it was determined that the Pb-Sn-Ca anode performed better than the Pb-Ca anode in terms of both integrity and electrocatalytic properties for oxygen evolution reaction (OER). Surface morphologies of the Pb-Sn-Ca anodes indicated that the roughness decreased as the solution stirring rate increased.