The role of corrosion/oxidation in the failure of aluminum adhesive joints under hot, wet conditions

Wedge tests were performed on a variety of adhesively bonded aluminum joints at two different temperatures. At both temperatures, one specimen was submerged in water and a second specimen, cut from the same panel, was submerged in a dilute sulfite solution. Separate tests indicated that the sulfite solution reduced the free oxygen content to less than 0.5 ppm and reduced the corrosion rate to a third of its value in pure water. In each case, no difference was observed in the amount of apparent adhesive failure over one day. These tests were supplemented by a reflection–absorption infra-red spectroscopy (RAIRS) study of silane-coated and uncoated surfaces aged under similar conditions. The results indicate that corrosion is not the limiting factor in the failure of these bonds. On the very thin air-formed oxides employed, this also suggests that conversion of the oxide to a trihydrate is not cause of the apparent adhesive failure.