Intergranular and Exfoliation Corrosion Behaviour of High Strength Al-Zn-Cu-Mg-Zr Alloy Containing Sc

Intergranular and exfoliation corrosion behaviors of Al-Zn-Cu-Mg-Zr alloy containing Sc were investigated.This over-aged alloy has the lowest intergranular and exfoliation corrosion sensitivity which decreased with the aging time and accorded with the results of polarization tests in EXCO solution.intergranular and exfoliation corrosion are closely attributed to η′,S′ and their distributions.With the aging time prolonging,η′ and S′ phases precipitated and transformed into equilibrium η′ and S′ phases.The coarsed η′ and S′ phases not only decreased the anodic tunnels of intergranular corrosion but also reduced the open circuit potentials between the precipitated phases and Al matrix which minimized the intergranular and exfoliation corrosion rate in Al-Zn-Cu-Mg-Zr alloy containing Sc.