Corrosion-Fatigue Crack Nucleation in the Alclad Layer of 2024-T3 Commercial Aircraft Skin

Abstract The sheet material used for commercial aircraft skin is often a composite consisting of a core of 2024-T3 aluminum alloy that is clad with pure aluminum and coated with paint on the exterior surface and a corrosion inhibitor on the interior surface. The present investigation is aimed at clarifying the role of the cladding in the early stages of corrosion-fatigue crack formation. Experimental findings show that crack nucleation sites are associated with pit colonies, but not in a way that would suggest that pit size or shape are critical to crack nucleation. Rather, pitting appears to produce a region of local embrittlement that facilitates local crack nucleation. The possible role of hydrogen in developing corrosion-induced embrittlement is discussed.