The positive difference effect and anomalous hydrogen evolution on the anodically polarized Mg surface in alkaline NH4+ containing solutions

The difference effect and hydrogen evolution behavior of pure Mg in alkaline NH4+ containing solutions are systematically investigated. The Mg electrode exhibits a positive difference effect, rather the traditional negative difference effect, with the anomalous hydrogen evolution in the alkaline 0.1 M (NH4)2SO4, 0.1 M NH4HCO3 and 0.05 M (NH4)2CO3 solutions. This is primarily attributed to the corrosion product film dissolution effect of NH4+ and the formation of the black corrosion products. The hydrogen evolution kinetics with the difference effects are deduced and explained by the prevailing incomplete film Mg+ mechanism and enhanced catalytic activity mechanism.