Preparation and electrochemical properties of Pb-0.3wt%Ag/Pb-WC composite inert anodes

We prepared Pb-0.3wt%Ag/Pb-WC (WC stands for tungsten carbide, the same below) composite inert anodes by double-pulse electrodeposition on the surface of Pb-0.3wt%Ag substrates, and investigated the electrochemical properties of the composite inert anodes, which were obtained under different forward pulse average current densities from 2 A/dm² to 5 A/dm² and WC concentrations from 0 g/L to 40 g/L in bath. The kinetic parameters of oxygen evolution, corrosion potential and corrosion current of the composite inert anodes were obtained in a synthetic zinc electrowinning electrolyte of 50 g/L Zn²⁺ and 150 g/L H₂SO₄ at 35 °C, by measuring the anodic polarization curves, Tafel polarization curves and cyclic voltammetry curves. The results show that Pb-0.3wt%Ag/Pb-WC composite inert anodes obtained under forward pulse average current density of 3 A/dm² and WC concentration of 30 g/L in an original acid plating bath, possess higher electrocatalytic activity of oxygen evolution, lower overpotential of oxygen evolution, better reversibility of electrode reaction and corrosion resistance in [ZnSO₄+H₂SO₄] solution. The overpotential of oxygen evolution of the composite inert anode is 0.926 V under 500 A/m² in [ZnSO₄+H₂SO₄] solution, and 245 mV lower than that of Pb-1%Ag alloy; the corrosion current of the composite inert anode is 0.95×10^-4 A which is distinctly lower than that of Pb-1%Ag alloy, showing the excellent corrosion resistance.