Post-treatment for anodized aluminum

• US 6,511,532 B2
• Filed: 11/06/2001
• Issued: 01/28/2003
• Est. Priority Date: 10/31/2000
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Kane, Michael J., Matzdorf, Craig A., Green, James L. III
• Primary Examiner(s): Green, Anthony J.
• Application Number:
  US10/012,982
• Publication Number:
  US 20020117236A1
• Time in Patent Office: 448 Days
• Field of Search: 106/14.21, 106/14.41, 106/14.44, 148/247, 148/275
• US Class Current: 106/14.44
• CPC Class Codes: C09D 5/084 Inorganic compounds
• CPC Class Codes: C09D 5/12 Wash primers
• CPC Class Codes: C23C 22/34 containing fluorides or complex fluorides
• CPC Class Codes: C23C 22/83 Chemical after-treatment
• CPC Class Codes: C23C 2222/10 Use of solutions containing trivalent chromium but free of hexavalent chromium
• CPC Class Codes: C25D 11/246 for sealing layers

Abstract

Composition for post-treating anodized aluminum and aluminum alloys and the process for using said composition to improve the corrosion-resistance, abrasion, and adhesion bonding properties of the anodized aluminum and its alloys. The composition comprises an acidic aqueous solution having a pH ranging from about 2.5 to 4.5 containing effective amounts of trivalent chromium salts, alkali metal hexafluorozirconates, an alkali metal fluoro-compound e.g. fluoroborates and/or fluorosilicates, and effective amounts of water soluble thickeners and surfactants.

Claims

1. A process for post-treating anodized aluminum and anodized aluminum alloys to improve the corrosion-resistance, abrasion, and adhesion bonding properties which comprises sealing the anodized aluminum and anodized aluminum alloys with an acidic aqueous solution having a pH ranging from about 2.5 to 4.5 comprising, per liter of said solution, from about 0.01 to 22 grams of a water soluble trivalent chromium salt, about 0.01 to 12 grams of an alkali metal hexafluorozirconate, about 0.01 to 12 grams of at least one fluoro-compound selected from the group consisting of an alkali metal tetrafluoroborate, an alkali metal hexafluorosilicate and mixtures thereof, from 0 to 10 grams of at least one water soluble thickener and 0 to 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 room temperature.

3. The process of claim 2 wherein the trivalent chromium salt ranges from about 4 to 6 grams, the hexaflurozirconate ranges from about 6 to 10 grams, and the fluoro-compound ranges from about 0.12 to about 1.2 grams.

4. The process of claim 3 wherein the thickener ranges from about 0.5 to about 1.5 grams.

5. The process of claim 4 wherein the surfactant ranges from about 0.5 to 1.5 grams.

6. A process for post-treating anodized aluminum and anodized aluminum alloys to improve the corrosion-resistance, abrasion, and adhesion bonding properties which comprises treating the anodized aluminum and anodized aluminum alloys with an aqueous solution having a pH ranging from about 3.7 to 4.0 which comprises, per liter of solution, from about 4.0 to 8.0 grams of a water soluble trivalent chromium salt, about 6.0 to 10 grams of an alkali metal hexafluorozirconate, and about 0.12 to 1.2 grams of at least one fluoro-compound selected from the group consisting of an alkali metal tetrafluoroborate, an alkali metal hexafluorosilicate, and mixtures thereof.

7. The process of claim 6 wherein the fluoro-compound is present in the solution in an amount ranging from about 0.24 to 0.36 grams and the post-treated anodized aluminum is subsequently treated with hot water at temperatures ranging up to 200°

F.

8. The process of claim 6 wherein about 0.5 to 1.5 grams of a cellulose thickener is present in the acidic chromate solution.

9. The process of claim 6 wherein the chromium salt is trivalent chromium sulfate.

10. The process of claim 6 wherein the alkali metal zirconate is potassium hexafluorozirconate.

11. A composition for post-treating anodized aluminum and anodized aluminum alloys to improve the corrosion-resistance, abrasion, and abrasion bonding properties which comprises an acidic aqueous solution having a pH ranging from about 2.5 to 4.5, and per liter of said solution, from about 0.01 to 22 grams of a water-soluble trivalent chromium salt, about 0.01 to 12 grams of an alkali metal hexafluorozirconate, about 0.01 to 12 grams of at least one fluoro-compound selected from the group consisting of an alkali metal tetrafluoroborate, an alkali metal hexafluorosilicate, and mixtures thereof, from 0 to 10 grams of at least one water soluble thickener and from 0 to 10 grams of at least one water soluble surfactant.

12. The composition of claim 11 wherein the pH of the aqueous solution ranges from about 3.7 to 4.0.

13. The composition of claim 12 wherein the trivalent chromium salt ranges from about the 4.0 to 8.0 grams, the hexofluorozirconate ranges from about 6.0 to 10 grams, and the fluoro-compound ranges from about 0.12 to 1.2 grams.

14. The composition of claim 13 wherein the thickener ranges from about 0.5 to 1.5 grams.

15. The composition of claim 14 wherein the surfactant ranges from about 0.5 to 1.5 grams.

16. A composition for seal coating anodized aluminum and anodized aluminum alloys to improve the corrosion-resistance, abrasion, and adhesion bonding properties which comprises an acidic aqueous solution having a pH ranging from about 3.7 to 4.0, and per liter of said solution, from about 0.01 to 22 grams of a water soluble trivalent chromium salt, about 0.01 to 12 grams of an alkali metal hexafluorozirconate, about 0.01 to 12 grams of at least one fluoro-compound selected from the group consisting of an alkali metal tetrafluoroborate, an alkali metal hexafluorosilicate and mixtures thereof, from 0 to 2.0 grams of at least one water soluble thickener and from 0 to 2.0 grams of at least one water soluble surfactant.

17. The composition of claim 16 wherein the tetrafluoroborate is present in the chromate solution in an amount ranging from about 0.24 to 0.36 grams per liter.

18. The composition of claim 16 wherein about 0.5 to 1.5 grams of a cellulose thickener is present in the chromate solution.

19. The composition of claim 16 wherein the chromium salt is trivalent chromium sulfate.

20. The composition of claim 16 wherein the alkali metal zirconate is a potassium hexafluorozirconate.