Lead-Silver Anode Degradation during Zinc Electrorecovery Process: Chloride Effect and Localized Damage

Abstract

Using mass-loss, potentiodynamic polarization, and electrochemical impedance measurements under anodic regime, the corrosion behaviour of lead-silver (0.55%) electrode in zinc electrowinning solution containing different concentration of chloride anions was studied. The results revealed that the rate of corrosion does not monotonically increase with concentration. Moreover, the maximum degradation occurs at the concentration where the anodic process (oxygen evolution) proceeds hardly. According to polarization curves, the electrode exhibited obvious electrocatalytic activity (for anode reaction) by forming oxide layer. To scrutinize the localized damage, occurring at the bottom of anode, we also took some scanning electron micrographs with energy dispersive X-ray analyses. The investigations suggested a new mechanism, that is, a complicated migration phenomenon, resulting from an electrodissolution/sedimentation/deposition process.