Exfoliation corrosion behaviour of welded high strength aluminium alloys

Abstract

Exfoliation corrosion is experienced in several groups of aluminium alloys, notably the Al–Cu and Al–Zn-Mg alloys used in automotive, aircraft, and aerospace applications andfor ships' superstructures and offshore structures. A study has been made of exfoliation in welded Al–Cu (2017) and Al–Zn–Mg (7015) alloys. The influence of the welding thermal cycle on exfoliation behaviour of T4 and T6 alloys was analysed to determine which initial age hardened condition will produce better resistance to exfoliation in welded constructions. The exfoliation tests were supplemented by corrosion potential determinations and SEM and metallographic analyses of the welded joints. The Al–Zn–Mg alloy wasfound to have the better exfoliation behaviour, although a slight decrease in the characteristics of the heat affected zone brought about by the welding process was observed. The initial age hardened condition appeared to have little influence, although T6 treatment may give slightly better resistance.