Long-term atmospheric corrosion behaviour of aluminium alloys 2024 and 7075 in urban, coastal and industrial environments

Atmospheric corrosion of alclad and extruded 2024 and 7075 were investigated by weight loss, loss in mechanical properties and depth of pitting over 20 years. The results demonstrated the inner cladding layer on alclad ones had higher corrosion resistance. After 20 years exposure, the cladding had not been penetrated by pitting and those alclads retained their mechanical properties well. Exfoliation occurred on extruded ones in coastal and industrial atmospheres. Especially in coastal atmosphere extruded 2024 suffered severe exfoliation and experienced rapid deterioration of mechanical properties. Furthermore, morphology and chemical compositions of corrosion products were analysed by SEM, XRD and EDS.