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. [ABSTRACT FROM AUTHOR]