Insights into corrosion behavior of Mg alloys containing long-period stacking ordered structure in chloride and sulfate media

Abstract

Micro-galvanic corrosion, driven by potential differences between strengthening phases and the matrix, is a major concern for Mg alloys in NaCl solution. Intriguingly, we find that the micro-galvanic corrosion, dominated by the nobler 18R-LPSO phase, is suppressed in Na₂SO₄ solution, where both the LPSO and Mg matrix are corroded simultaneously. Since the LPSO phase contains more Er/Zn atoms than matrix, higher proportion of Er³⁺/Zn²⁺ could be released in SO₄^2--affected corrosion, eventually forming a more protective corrosion film containing Er₂O₃/ZnO/ZnS. These findings highlight the specific corrosion behavior of Mg alloys in Na₂SO₄ solution, offering valuable insights for corrosion mitigation strategies.