A series of accelerated corrosion tests were conducted to study the relative rates of corrosion penetration into an adhesive bondline on clad and bare aluminum. Three different adhesive systems were tested. Both standard and corrosion-inhibiting primers were used with two of the adhesives. Aluminum alloys, 2024 bare and clad, 7075 bare and clad, 5052 and 3003 were used. The aluminum surfaces were prepared by chromic acid anodizing and by etching in a solution of sulfuric acid and sodium dichromate (FPL etch). The bonded panels were subjected to 30, 60, and 90 days exposure in a salt-spray cabinet. After exposure, the panels were tested for peel strength and were examined visually for extent of corrosion.
The results of these tests indicate that the rate of bondline corrosion penetration is greater on the clad aluminum alloys and on 3003 than on the bare alloys tested.