Influence of Co2+ and Mn2+ ions on the kinetics of lead anodes for zinc electrowinning

The influence of Co2+ and Mn2+ ions on the kinetics of lead and lead–silver alloy anodes is analysed using impedance spectroscopy and steady-state polarisation curves. With lead–silver anodes, increasing the Mn2+ concentration catalyses the oxygen evolution current by stimulating the reaction rate. Impedance data reveal a transient inhibition of the reaction, ascribed to the adsorption of a silver-salt containing manganese. The addition of Co2+ catalyses oxygen evolution, mainly on the pure lead anode. For lead–silver anodes, the small catalytic effect of Co2+ ions implies an increase in the Tafel coefficient for the oxygen reaction. The transient inhibiting process suggests the formation of a cobalt-containing adsorbate on the pure lead anode.