The role of anodic hydrogen evolution in magnesium alloy corrosion: A multiphase phase-field model approach

The hydrogen evolution reaction occurring at the anode (AHE) during magnesium alloy corrosion significantly interferes with the accurate theoretical prediction of the corrosion extent. However, the impact of AHE on corrosion kinetics remains poorly understood and requires further investigation. A multiphase phase-field model is proposed to investigate the electrochemical corrosion behavior of magnesium alloys. This model is based on the incomplete film Mg⁺ mechanism and takes into account the non-uniformity factor caused by grain orientation. The model is capable of depicting the regulation of corrosion by AHE and captures the growth of insoluble corrosion products (ICP) at the metal interface. The findings suggest that during the Mg corrosion reaction, the higher the proportion of anodic hydrogen evolution, the lower the corrosion rate. In addition, the formation of ICP causes corrosion to enter a closed cell state, resulting in fluctuations of the Mg²⁺ cumulative rate at the interface. Moreover, the corrosion rate of Mg decreases significantly, and the grain orientation effect of corrosion weakens as time increases.