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 NH 4 + 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 (NH 4 ) 2 SO 4 , 0.1 M NH 4 HCO 3 and 0.05 M (NH 4 ) 2 CO 3 solutions. This is primarily attributed to the corrosion product film dissolution effect of NH 4 + 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. Graphical abstract