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.