Investigating the role of Al₂Ca particles in the corrosion behavior of AZX311 Mg alloy in chloride and sulfate electrolytes

The corrosion behavior of hot-rolled AZX311 magnesium (Mg) alloy was studied in sodium chloride and sodium sulfate solutions (0.15 M and 0.25 M concentrations) at 30 °C and 50 °C. Microstructural analysis of the hot-rolled alloy revealed uniformly distributed Al₂Ca precipitates within the α-Mg matrix. Electrochemical tests revealed higher corrosion rates in sodium chloride, attributed to the chloride-induced breakdown of the protective magnesium hydroxide film. Corrosion accelerated with increasing temperature and concentration, with the highest rate (4.14 millimeters per year) observed in 0.25 M sodium chloride at 50 °C, accompanied by severe localized attack in hydrogen evolution analysis. Moreover, the presence of Al₂Ca precipitates contributed to the stabilization of the passive surface film in sulfate-containing solutions. In contrast, these precipitates acted as sites for galvanic coupling with the α-Mg matrix, thereby intensifying localized corrosion processes, particularly under elevated temperatures within chloride-containing environments.