Localized corrosion of 6056 T6 aluminium alloy in chloride media

The corrosion behaviour of 6056 T6 aluminium alloy was investigated in 1 M NaCl solution. Fitting and intergranular corrosion were found to be depende nt on each other since intergranular corrosion nucleated on pit walls and s pread from them. Coarse intermetallic Al-Si-Mg-containing particles were fo und to be nucleation sites for pits. Pits first developed within the grains and grew up through microscopic crystallographic tunnels. The intergranula r corrosion mechanism of 6056 T6 alloy appeared to consist of preferential dissolution of the anodic Si and Cu depleted zone along grain boundaries wh ereas Cu-Si-Mg rich intergranular precipitates functioned as local cathodes and stimulated the dissolution of the depleted zone. (C) 1999 Elsevier Sci ence Ltd. Al! rights reserved.