IMPROVED NON-CHROMATED OXIDE COATING FOR ALUMINUM SUBSTRATES

An improved process that is commercially practical for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on an aluminum or aluminum alloy substrate for use in aircraft/aerospace applications (for example, an aluminum or aluminum alloy commercial airplane part), the process comprising the steps of: (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting the following starting materials: (1) a cobalt-II salt; (2) an ammonium salt; (3) one or more inorganic complexing agents selected from a soluble metal carboxylate, a soluble metal nitrite, or ammonia; (4) a water soluble amine; and (5) an oxidizing agent; and (b) contacting the substrate with the aqueous reaction solution for a sufficient amount of time to oxidize the surface of the substrate, whereby the oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to the substrat e. A similar commercially practical process for aluminum or aluminum alloy substrates for use in non-aircraft/aerospace applications (fo r example, an aluminum or aluminum alloy marine hardware part) employs the above steps, but does not include the ammonium salt in the starting materials.