The effect of Cu content on susceptibility to intergranular corrosion of Al-Mg-Si alloy.

Abstract

Electrochemical measurements showed the results as follows. Pitting potential of solution heat treated alloy increased with Cu content. After precipitation heat treatment at 200°C for 60 min and for 180 min, pitting potential of Cu containing alloys decreased to −720~−730 mV (vs. SCE), accompanying intergranular corrosion. Dissolution potential of Mg2Si compound was found to be −730 mV (vs. SCE), which agreed with the pitting potential of precipitation heat treated Al–Mg–Si–Cu alloys. Intergranular corrosion of Al–Mg–Si–Cu alloys was concluded to be caused by preferential dissolution of less noble Mg2Si phase at grain boundary.