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 pol arisation curves. With lead-silver anodes, increasing the Mn2+ concentratio n catalyses the oxygen evolution current by stimulating the reaction rate. Impedance data reveal a transient inhibition of the reaction, ascribed to t he adsorption of a silver-salt containing manganese. The addition of Co2+ c atalyses oxygen evolution, mainly on the pure lead anode. For lead-silver a nodes, the small catalytic effect of Co2+ ions implies an increase in the T afel coefficient for the oxygen reaction. The transient inhibiting process suggests the formation of a cobalt-containing adsorbate on the pure lead an ode.