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.