Chrome free treatment for aluminum

Abstract

A chromate free conversion coating for Al based metals and methods of use. The compositions comprise (a) water soluble fluoacids of Group IVB metals, (b) fluoboric acid, (c) boric acid, (d) gluconic acid and, optionally (e) an aminosilane adhesion promoter or an organophosphonate corrosion inhibitor. In the method, the requisite metal part is contacted by the composition such as by immersion or spraying or the like.

What is claimed is:  
     
         1 . A method of coating an aluminum or aluminum alloy metal surface comprising contacting said surface with an effective amount of a chromate free, acidic aqueous treatment solution comprising a (a) water soluble fluoacid of a Group IVB (CAS) metal or mixtures thereof, (b) fluoboric acid, (c) boric acid, (d) gluconic acid, and, optionally a topping agent (e) wherein said topping agent is selected from the group of (ei) aminosilane adhesion promoter and/or (eii) organophosphonate corrosion inhibitors.  
     
     
         2 . A method as recited in  claim 1  including spraying said treatment solution onto said surface.  
     
     
         3 . A method as recited in  claim 1  including immersing said surface in said treatment solution.  
     
     
         4 . A method as recited in  claim 1  wherein said (ei) is present and comprises an alkoxylated amino silane.  
     
     
         5 . A method as recited in  claim 4  wherein said alkoxylated aminosilane is gamma aminopropyltriethoxysilane.  
     
     
         6 . A method as recited in  claim 1  wherein said (eii) comprises amino tri (methylene phosphoric acid).  
     
     
         7 . A method as recited in  claim 1  wherein said (a) comprises H 2 ZrF 6  and H 2 TiF 6 .  
     
     
         8 . A method as recited in  claim 7  wherein said treatment solution further includes nitric acid and ammonium hydroxide.  
     
     
         9 . Chromate free aqueous conversion coating adapted for contact with an aluminum or aluminum alloy surface, said composition comprising: 
 (a) water soluble fluoacid of a Group IVB (CAS) metal or mixtures of said fluoacids    (b) fluoboric acid    (c) boric acid    (d) gluconic acid and    (e) a topping agent, wherein said topping agent is selected from the group consisting of (ei) aminosilane adhesion promoters and/or (eii) organophosphonate corrosion inhibitors.    
     
     
         10 . Compositions as recited in  claim 9  wherein said (a) comprises H 2 ZrF 6  and H 2 TiF 6 .  
     
     
         11 . Composition as recited in  claim 10  wherein (ei) is present and comprises an alkoxylated aminosilane.  
     
     
         12 . Composition as recited in  claim 11  wherein said (ei) is gamma aminopropyltriethoxysilane.  
     
     
         13 . Composition as recited in  claim 9  wherein (eii) is present and comprises amino tri(methylene phosphonic acid).  
     
     
         14 . Composition as recited in  claim 13  further including nitric acid and ammonium hydroxide and wherein the pH of said aqueous conversion coating composition is about 0.5-5.