Process for sealing phosphoric acid anodized aluminums

Abstract

Process of seal coating phosphoric acid anodized aluminum and aluminum alloys to improve the corrosion resistance and maintain the adhesive bonding properties. The process comprises post-treating phosphoric acid anodized aluminum and its alloys with an acidic aqueous solution comprising, per liter of acidic solution, from about 0.01 to 22 grams of a water soluble trivalent chromium compound, about 0.01 to 12 grams of an alkali metal hexafluorozirconate, about 0.0 to 12 grams of at least one alkali metal tetrafluorosilicate and/or an alkali metal hexafluoroborate, from about 0.001 to 10 grams of at least one water soluble divalent zinc compound and from 0.0 to 10 grams of a water soluble thickener and/or water soluble surfactant.

1 . Process for sealing phosphoric acid anodized aluminum and aluminum alloys to improve the corrosion resistance and maintain the adhesive bonding strength which comprises treating the anodized aluminum and its alloys with an acidic aqueous solution having a pH ranging from about 2.5 to 5.5; said acidic aqueous solution comprising, per liter of solution, from about 0.01 to 22 grams of a trivalent chromium compound, about 0.01 to 12 grams of an alkali metal hexafluorozirconate, about 0.0 to 12 grams of at least one fluorocompound selected from the group consisting of an alkali metal tetrafluoroborate, an alkali metal hexafluorosilicate and mixtures thereof, from about 0.001 to 10 grams of at least one divalent zinc compound, from 0.0 to about 10 grams of at least one water soluble thickener and from 0.0 to about 10 grams of at least one water-soluble surfactant.  
   
   
       2 . The process of  claim 1  wherein the pH of the aqueous solution ranges from about 3.7 to 4.0 and the temperature of the aqueous solution ranges from about ambient to 200° F.  
   
   
       3 . The process of  claim 2  wherein the trivalent chromium is a water soluble compound ranging from about 4.0 to 8.0 grams, the hexafluorozirconate is a water soluble compound ranging from about 6.0 to 10 grams, and the fluorocompounds are water soluble compounds ranging from about 0.12 to about 1.2 grams.  
   
   
       4 . The process of  claim 3  wherein the thickener ranges from about 0.5 to 1.5 grams and the surfactant ranges from about 0.5 to 1.5 grams.  
   
   
       5 . Process for sealing phosphoric acid anodized aluminum and aluminum alloys to improve the corrosion resistance and maintain the adhesive bonding strength which comprises treating the anodized aluminum and its alloys with an acidic aqueous solution having a pH ranging from about 3.7 to 4.0; said acidic aqueous solution comprising, per liter of solution, from about 4.0 to 8.0 grams of a trivalent chromium salt, about 6.0 to 10 grams of an alkali metal hexafluorozirconate, about 0.001 to 12 grams of at least one fluorocompound selected from the group consisting of an alkali metal tetrafluoroborate, an alkali metal hexafluorosilicate and mixtures thereof, from about 0.001 to 10 grams of at least one divalent zinc compound, from 0.0 to about 10 grams of at least one water soluble thickener and from 0.0 to about 10 grams of at least one water soluble surfactant.  
   
   
       6 . The process of  claim 5  wherein the fluorocompound is present in the solution in an amount ranging from about 0.24 to 0.36 grams and the treated anodized aluminum is subsequently washed with water at temperatures ranging up to 200° F.  
   
   
       7 . The process of  claim 5  wherein the thickener is a cellulose compound present in the acidic solution in amounts ranging from about 0.5 to 1.5 grams per liter.  
   
   
       8 . The process of  claim 5  wherein the chromium salt is trivalent chromium sulfate.  
   
   
       9 . The process of  claim 5  wherein the alkali metal zirconate is potassium hexafluorozirconate.  
   
   
       10 . The process of  claim 5  wherein the trivalent chromium salt is chromium sulfate ranging from about 4.0 to 8.0 grams, the hexafluorozirconate is potassium hexafluorozirconate ranging from about 6.0 to 10 grams, and the tetrafluoroborate or hexafluorosilicate ranges from about 0.24 to 0.36 grams.  
   
   
       11 . The process of  claim 10  wherein the thickener is a cellulose compound ranging from about 0.5 to 1.5 grams.  
   
   
       12 . The process of  claim 5  wherein the zinc compound is zinc acetate.  
   
   
       13 . The process of  claim 11  wherein the chromium salt is trivalent chromium sulfate and the divalent zinc compound is zinc sulfate.  
   
   
       14 . The process of  claim 11  wherein the water soluble surfactant is selected from the group consisting of water soluble non-ionic, anionic and cationic surfactants.  
   
   
       15 . The process of  claim 14  wherein the zinc compound is a divalent zinc sulfate.  
   
   
       16 . The process of  claim 15  wherein the zinc sulfate is present in the aqueous solution in an amount ranging from about 0.1 to 5.0 grams.  
   
   
       17 . The process of  claim 5  wherein the chromium salt is chromium sulfate present in the aqueous solution in an amount ranging from 4.0 to 8.0 grams, the mixture of alkali metal tetrafluoroborate and hexafluorosilicate are present in the aqueous solution in an amount ranging from about 0.001 to 12 grams.  
   
   
       18 . The process of  claim 17  wherein the zinc compound is zinc sulfate present in the aqueous solution in an amount ranging from about 0.1 to 5.0 grams.  
   
   
       19 . The seal-coated phosphoric acid anodized aluminum and aluminum alloys of  claim 1 .  
   
   
       20 . The seal-coated phosphoric acid anodized aluminum and aluminum alloys of  claim 5.