A closer inspection of a grain boundary immune to intergranular corrosion in a sensitised Al-Mg alloy

The intergranular corrosion of Al-Mg alloys arises from sensitisation due to thermal exposure. Here, a protected low angle (8.7°) grain boundary which hinders the intergranular corrosion propagation in a sensitised (150°/7 d) Al-Mg alloy was studied in detail. Discrete β-phase was observed on this protected boundary, but with a lower continuity compared to the other fully (or partially) dissolved grain boundaries. The results herein seek to unify the relationship between β-phase continuity and grain boundary misorientation angle as critical for intergranular corrosion propagation in the studied alloy.