Quantification of Corrosion in 7075-T6 Aluminum Alloy

In aging aircraft the synergetic interaction between corrosion and fatigue has been shown to impact the life expectancy of aluminum alloys. The objective of this study was to quantify the effects of corrosion, in terms of mass loss, on the static strength and fatigue life of 7075-T6-aluminum alloy. This was an experimental study conducted on samples with laboratory-controlled corrosion of varying mass loss levels at their mid-surface on one side. The specimens were covered with special masking material to allow corrosion only in the desired area. Both fatigue life and the ultimate tensile strength of the specimens were observed to drop significantly with small amounts of mass loss (less than 5%). After the initial decrease the UTS was observed to decrease linearly with additional mass-loss. The fatigue life of the specimens decreased significantly with additional mass loss. The topology of the pits, and the related subsurface damage hinted at existence of areas of high stress concentration resulting in the immediate reduction of UTS and fatigue life of the specimens.