The Relationship between Stress Corrosion Cracking and Corrosion Behaviors in 7NO1 Alloy : Studies on Stress Corrosion Cracking in Al-Zn-Mg Alloy (2nd Report)

In the present paper the relationship between stress corrosion cracking (SCC) and corrosion behaviors of Al-Zn-Mg 7NO1 alloy in NaCl solutions was investigated metallurgically and electro chemically. For lower temperature (below 60℃)-and shorter time-aged (ie. cold aged) alloys, the susceptibilities to SCC and intergranular corrosion were in a good correlation, and the values of the observed activation energy of SCC and dissolution were equal approximately. The SCC is essentially caused by active-path corrosion of pre-existed anodic zone along grain boundaries. For higher temperature-and longer time-aged (ie. warm aged) alloys, the contribution of corrosion actions to SCC process was relatively small. The crack growth involved a mechanical rupture process. For high temperature (above 85℃)-and shorter time-aged alloys, the SCC was assisted by easy crack initiation due to highly selective exfoliation corrosion.