Comparing intergranular corrosion in Al-Mg-Si-Cu alloys with and without α-Al(Fe,Mn,Cu)Si particles

Abstract

In this study, a model alloy without Fe and Mn additions, is compared with a commercial AA6005 alloy to further understand how the α-Al(Fe,Mn,Cu)Si particles affect intergranular corrosion (IGC) behaviour. Both alloys were subjected to an accelerated IGC test for durations ranging from 1 to 120 h. Microstructures were studied using scanning and transmission electron microscopy, and electron backscatter diffraction. The presence of α-Al(Fe,Mn,Cu)Si particles yields significantly more uniform IGC attacks and higher corrosion rates. However, the maximum depth of IGC attacks reaches similar values after ~24 h of exposure. This is attributed to the formation of Cu-rich particles along the grain boundaries during the corrosion process, which further catalyses the cathodic reactions.