Electrochemical studies of the performance of different Pb-Ag anodes during and after zinc electrowinning

One Pb-0.25%Ag-0.1%Ca alloy anode and three commercial Pb-0.6%Ag, Pb-0.58%Ag and Pb-0.69%Ag alloys anodes have been studied by conventional electrochemical methods and electrochemical impedance spectroscopy (EIS) in acid zinc sulphate electrolyte with and without MnSO₄ additions to evaluate their activity and corrosion behaviour. At a current density of 50 m Acm⁻² and 38 °C, the polished surface of the anode Pb-0.69%Ag alloy had the lowest overpotential, followed closely by that of anodes Pb-0.6%Ag and Pb-0.58%Ag alloys and then anode Pb-0.25%Ag-0.1%Ca alloy in a bath with and without MnSO₄ additions. Also, during potential decay period after 5 h electrolysis, the polished surfaces showed that anode Pb-0.69%Ag alloy had the lowest corrosion current among the four examined anodes, followed by anodes Pb-0.6%Ag, Pb-0.25%Ag-0.1%Ca alloys and Pb-0.58%Ag alloy.