Tolerable corrosion damage on aircraft aluminum structures: Local cladding patterns

A concept for tolerating corrosion damage on aircraft aluminum structures is outlined. The proposed concept is based on experimental observations. Observed has been that local cladding patterns are sufficient to keep reductions of both, tensile and fatigue properties of the bare 2024 aircraft aluminum alloy during the exposure of the alloy to a 3.5% NaCl solution up to 300 h limited; it leads to the suggestion that corrosion damage might be tolerable. Metallographic investigations of corrosion damage were performed to support this observation. Quantification of corrosion damage is made through macroscopic stress concentration factors which account for the reduction of tensile and fatigue properties caused by corrosion damage. The stress concentration factors used are functions of the microstructural corrosion damage features pitting depth, shape and density; their values increase with progressing corrosion damage during the corrosion exposure of the alloy.