On the Mechanisms of Interaction Between Corrosion and Fatigue Cracking in Aircraft Aluminum Alloys

The possible mechanisms of interaction between preexisting corrosion and fatigue cracking in aircraft aluminum alloys are being reviewed. The information presented in this paper indicates that corrosion sites in aluminum alloy 2024-T3 can be considered equivalent mechanical damage sites and that fracture mechanics can be applied by using an equivalent flaw size to compute the resultant stress concentration and loss in residual strength. Further, evidence was presented indicating that hydrogen produced by the corrosion process, could enter the aluminum alloy 7075-T6 lattice, causing detrimental changes of the alloy properties. Hydrogen transport and embrittlement mechanisms are discussed.