Electron microscopy analysis of grain boundaries and intergranular corrosion in aged Al-Mg-Si alloy doped with 0.05 wt% Cu

The microstructure and intergranular corrosion have been studied in an extruded and aged Al-Mg-Si alloy doped with 0.05 wt% Cu after immersing the material in an acidified salt solution. Intergranular corrosion takes place in this alloy despite the low Cu content. Electron microscopy analysis of the surface exposed to the corrosive environment does not reveal any significant difference in the fraction of corroded random and coincident site lattice high angle boundaries. Low angle boundaries with misorientations below 10° are found to be consistently more resistant to intergranular corrosion than any other boundary type. • Cu film is detected along grain boundaries in AA6082-T6 alloy with 0.05 wt%Cu. • Boundaries with very low misorientations are unlikely to contain β and Q particles. • Distinct PFZs are seen near random and CSL high angle boundaries (HABs). • Random and CSL HABs are highly susceptible to intergranular corrosion.