Corrosion resistance mechanism of a novel porous Ti/Sn-Sb-RuOx/β-PbO2 anode for zinc electrowinning

Sn-SbOx, Sn-Sb-RuOx, and β-PbO2 coatings were successfully deposited on a titanium substrate by using the thermal deposition and electrodeposition methods, and their electrochemical properties were investigated in detail. The Sn-Sb-RuOx interlayer played a very important role in enhancing the stability of the PbO2 coating electrodeposited at a low current density. The scanning electron microscopy results showed that the cracks in the Sn-Sb-RuOx coating were larger than those in the Sn-SbOx coating. Moreover, the Ti/Sn-Sb-RuOx/β-PbO2 coating had many large pits with pore diameters in the range of 50-180 μm and pore depths of <18.4 μm. The electrodeposition mechanism of β-PbO2 was investigated by cyclic voltammetry. Compared to the compact β-PbO2 anode, the porous β-PbO2 anode showed superior electrocatalytic activity and electrochemical stability. A service life of 96 h was achieved for this anode under the accelerated-life-test conditions at a current density of 1 A/cm2 in a solution of 150 g/L H2SO4 and 1 g/L Cl−.