Discovery of novel phenomenon and mechanism revelation of an Al-Zn-Mg-Cu alloy without intergranular corrosion

This study identified an unreported phenomenon where the Al-8.8Zn-2Mg-2Cu alloy exhibit no intergranular corrosion in 5.7% NaCl+0.3% H 2 O 2 solution, which could be attributed to the formation of dispersive MgZn 2 phase along grain boundaries. Compared with the Mg 2 Al 4 Zn 3 grain boundary precipitates in Al-6.6Zn-2Mg-2Cu alloy, MgZn 2 demonstrates a stronger electron localization tendency, indicating superior bonding capability and structural stability. The lower density of states value near Fermi energy level suggests reduced susceptibility to electron transfer of MgZn 2 compared with Mg 2 Al 4 Zn 3 . Combined with adsorption energy, corrosive solution tends to accumulate preferentially on Al phase in Al-8.8Zn-2Mg-2Cu alloy, while it distributes relatively uniformly across both Mg 2 Al 4 Zn 3 and Al phases in Al-6.6Zn-2Mg-2Cu alloy. Thus, corrosion propagates along Mg 2 Al 4 Zn 3 phases at grain boundaries, leading to severe intergranular corrosion. Conversely, MgZn 2 exhibits corrosion resistance similar to Al, and corrosive medium accumulation on MgZn 2 is less favored, which suppresses the initiation of intergranular corrosion at source.