Abstract: Environmentally stable bond joints of aluminum metal and aluminum alloys in adhesively joined structures are formed by utilizing a prebonding anodization of the aluminum surfaces in a phosphoric acid electrolyte using an electrolyte bath temperature of 60.degree. to 85.degree. F. The anodized surface is then removed from the electrolyte bath and washed free of electrolyte within from one half to two and one half minutes from cessation of anodizing current, dried and coated with adhesive resin. The anodized aluminum metal surfaces are then juxtaposed with an adhesive resin and bonded together under pressure and heat to cure the adhesive resin. The resulting structure is resistant to failure of the bond joints on exposure to moist atmospheric conditions. The surface preparation provides a porous hydration resistant aluminum oxide surface which minimizes adhesive failure to the oxide-adhesive interface under aqeuous exposure.

Abstract: Environmentally stable bond joints of aluminum metal and aluminum alloys in adhesively joined structures are formed by utilizing a prebonding anodization of the aluminum surfaces in a phosphoric acid electrolyte containing from about 1.5 to about 50% H.sub.3 PO.sub.4 at 1 to 50 volts for a period of 5 to 60 minutes using a bath temperature of 50.degree. to 100.degree. F. The anodized surface is then washed free of electrolyte, dried and coated with an adhesive resin. The aluminum metal segments are then arranged in a composite arrangement and bonded together under pressure and heat to cure the adhesive resin. The resulting structure is resistant to failure of the bond joints on exposure to moist atmospheric conditions. The surface preparation provides a hydration resistant aluminum oxide surface which minimizes adhesive-aluminum separation under aqueous exposure. Alloys containing copper and other alloying constituents may be successfully anodized and bonded by this process.