In order to assess the effect of preexisting corrosion on the fatigue crack behavior of aircraft aluminum alloys 2024-T3 and 7074-T6 crack initiation and growth data were obtained using fracture mechanics specimens. These specimens incorporated mechanically thinned areas and areas that had been preexposed to environments which produced various degrees of pitting or exfoliation corrosion. The data obtained from these laboratory experiments indicate that specific corrosive environments have a significant effect on the fatigue cracking behavior of aircraft aluminum alloys. The effect of preexisting corrosion was most pronounced in the fatigue crack initiation stage. Based on the results of this study, it was concluded that the effect of preexisting corrosion on the fatigue cracking
behavior of both aluminum alloys 2024-T3 and 7075-T6 is a combination of stress concentrations as a result of material loss, and altered material properties, possibly as a result of hydrogen entfy into the lattice.
Keywords: Preexisting corrosion, fatigue cracking behavior, aluminum alloys 2024-T3 and 7075-T6, aircraft structural integrity and durability, hydrogen, stress corrosion cracking