The Contribution of Corrosion to the Stress Corrosion Cracking of Al-Zn-Mg Alloys

Results are reported for measurements of corrosion potentials of aluminium alloys in various heat treatments. The morphology of corrosive attack is studied with the aid of optical microscopy and electron microscopy using direct replicas. The results support the theory that preferential grain boundary attack occurs in aluminium alloys that are susceptible to stress corrosion. It is argued that this need not be the main mechanism of failure, but that it may act in unison with co-planar glide, decohesion of grain boundary precipitates, and hydrogen induced cracking.