Effect of Mn2+ ions on the electrodeposition of zinc from acidic sulphate solutions

The effect of Mn2+ ions on current efficiency (CE), deposit morphology and polarization behaviour during electrodeposition of zinc from acidic sulphate solutions was investigated. In the conditions studied, Mn2+ ions had no significant effect on CE over the concentration range of 1–10 g dm− 3. However, a decrease in CE of more than 35% was obtained at 50 g dm− 3. The cathodic polarization curves and the corresponding kinetics analysis demonstrated that this decrease in CE at higher concentrations of Mn2+ ions was due to the strong depolarizing effect of MnO4− ions and other oxidized products of manganese. Moreover, the kinetics analysis of anodic polarization suggested that the presence of Mn2+ ions catalyzed the oxygen evolution reaction. The addition of Mn2+ ions was also observed to change the surface morphology and deposit quality of the electrodeposited zinc, affecting the crystallographic orientation by significantly inhibiting the growth of (002) and (100) planes.