Corrosion-induced hydrogen embrittlement of 2024 and 6013 aluminum alloys

The effect of corrosion on the mechanical behavior of the aircraft aluminum alloys 2024 and 6013 has been investigated experimentally. It is shown that corrosion exposure leads to moderate reduction in yield and ultimate tensile stress. Dramatic reduction in elongation to failure and strain energy density are observed even after relatively short exposure times. Mechanical removal of the corroded areas restored the yield and ultimate tensile stress but not the tensile ductility. The latter was stepwise restored to the values for the uncorroded materials after heat treatment of the alloys at temperatures corresponding to thermal desorption of certain hydrogen trapping sites. The findings clearly suggest that corrosion of the above alloys is associated with volumetric hydrogen embrittlement. The corrosion-induced reduction of tensile ductility was associated with the reduction of the residual strength of corroded components. A model, based on a multiscaling concept, was used to relate the reduction of fracture toughness and residual strength to the reduction of the strain energy density obtained from tensile tests for corroded and uncorroded coupons. It has been shown that the strain energy density can be used to reliably predict the residual strength of corroded components.