Influence of the surface activation and local pitting susceptibility on the AC-electrograining of aluminium alloys

AC electrograining of aluminium is strongly influenced by the surface microstructure. The mechanical and electrochemical properties of the sub-surface present in aluminium alloys affect the electrochemical reactions that prevail during electrograining. Etching pre-treatment of aluminium removes intermetallics and rolled-in oxides; as a result, the attack on the aluminium substrate starts with the initial cycles of the electrograining process. Local electrochemical investigations show differences in corrosion and passivation properties between rolled-in oxides and clean surfaces. The interface between rolled oxides and aluminium matrix acts as a weak point for pit initiation.

Research highlights► Electrograining is influenced by the deformed sub-surface. ► Etching pre-treatments can alter the electrograining process. ► Removal of intermetallics and rolled oxides favours the pitting of the substrate. ► Pitting originates at the rolled-oxide-bulk interface.