A critical consideration for the use of Al-cladding for protecting aircraft aluminum alloy 2024 against corrosion

The necessity of involving Al cladding as a means of protecting the aircraft aluminum alloy 2024 against corrosion has been assessed experimentally. Bare as well as Al-clad protected 2024 specimens were pre-corroded and then subjected to mechanical tests. By recognizing the lack on validated concepts for the laboratory simulation of the corrosion damage expected in the service conditions of an aircraft structure, in the present work two different laboratory corrosion tests, namely the immersion of the alloy in a 3.5% NaCl solution, and the exfoliation corrosion test have been employed for pre-corroding the specimens. For the case of the aggressive exfoliation corrosion environment the protective role of Al-cladding is essential for ensuring the good tensile and fatigue behavior of the 2024 alloy. On the other hand, the results have shown that for the case of the mild 3.5% NaCl solution environment, the use of a cladding layer downgrades the fatigue behavior of the material, thus giving raise to doubt on the need of involving cladding. The results demonstrate the need for systematic efforts for the development of concepts which will allow the laboratory simulation of corrosion accumulated in service.