PRETREATMENT FOR ALUMINUM AND ALUMINUM ALLOYS

• US 20030230215A1
• Filed: 01/23/2003
• Published: 12/18/2003
• Est. Priority Date: 10/31/2000
• Status: Active Grant

• Current Assignee: Chief of Naval Research
• Original Assignee: Chief of Naval Research
• Inventors: Nickerson, William C. Jr., Matzdorf, Craig A.
• Granted Patent: US 6,669,764 B1
• Time in Patent Office: Days
• 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

Abstract

Pretreated aluminum and aluminum alloys and the process and composition for pretreating said aluminum and its alloys to provide a coating with color recognition for identification purposes and to improved the corrosion-resistance, electrical conductivity, and adhesion properties which comprises pretreating said aluminum and its alloys with an effective amount of an acidic aqueous solution having a pH ranging from about 2.5 to 5.5 comprising water soluble trivalent chromium compounds, alkali metal hexafluorozirconates, divalent zinc compounds, alkali metal fluoro-compounds, and effective amounts of water soluble thickeners, surfactants or wetting agents.

Claims

1. A process for pretreating aluminum and alloys of aluminum to provide a coating having color recognition, and improved corrosion-resistance, electrical conductivity, and adhesion properties which comprises treating said aluminum and alloys of aluminum with an effective amount of an acidic aqueous solution having a pH ranging from about 2.5 to 5.5 and comprises, per liter of said 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 water soluble fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, alkali metal hexafluorosilicates and mixtures thereof, about 0.001 to 10 grams of at least one water soluble zinc compound, and from 0 to 10 grams of at least one water soluble thickener.

3. 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 to about 200°

F.

4. The process of claim 3 wherein the trivalent chromium compound ranges from about 5.0 to 7.0 grams, the hexafluorozirconate ranges from about 6.0 to 8.0 grams, and the tetrafluoroborate ranges from about 0.01 to 1.2 grams.

5. The process of claim 1 wherein the thickener is a cellulose compound ranging from 0.5 to 1.5 grams.

9. The process of claim 1 wherein the alkali metal zirconate is potassium hexafluorozirconate.

2. A process for pretreating aluminum and alloys of aluminum to provide a coating having color recognition, and improved corrosion-resistance, electrical conductivity, and adhesion properties which comprises treating said aluminum and alloys of aluminum at about room temperature with an effective amount of an aqueous solution having a pH ranging from about 3.7 to 4.0 and comprises per liter of solution from about 0.01 to 10 grams of a water soluble trivalent chromium salt, about 0.01 to 8.0 grams of an alkali metal hexafluorozirconate, about 0.0 to 12 grams of at least one fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, alkali metal hexafluorosilicates and mixtures thereof, and about 0.001 to 10 grams of at least one water soluble divalent zinc salt.

6. The process of claim 2 wherein the tetrafluoroborate is present in the solution in an amount ranging from about 0.12 to 0.24 grams.

7. The process of claim 2 wherein about 0.5 to 1.5 grams of a cellulose thickener is added to the pretreatment solution.

8. The process of claim 2 wherein the chromium salt is trivalent chromium sulfate.

10. The process of claim 2 wherein the zinc compound is divalent zinc sulfate ranging in an amount from about 0.01 to 5.0 grams per liter.

11. Pretreated aluminum and alloys of aluminum having a color recognized coating and improved corrosion-resistance, electrical conductivity, and adhesion properties comprising said aluminum and alloys of aluminum treated with an effective amount of an acidic aqueous solution having a pH ranging from about 2.5 to 5.5 and comprising per liter of said solution from about 0.01 to 22 grams of a water-soluble trivalent chromium compound, from about 0.01 to 12 grams of an alkali metal hexafluorozirconate, about 0.0 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, about 0.001 to 10 grams of at least one water soluble zinc compound and from 0 to 10 grams of at least one water soluble thickener.

13. The pretreated aluminum of claim 11 wherein the thickener ranges from about 0.5 to 1.5 grams.

14. The pretreated aluminum of claim 11 wherein the zinc compound is divalent zinc sulfate and the hexafluorosilicate is present in an amount ranging from about 0.01 to 1.2 grams.

15. The pretreated aluminum of claim 11 wherein the tetrafluoroborate is present in the solution in an amount ranging from about 0.01 to 1.2 grams.

16. The pretreated aluminum of Claim 11 wherein about 0.5 to 1.5 grams of a cellulose thickener is present in the solution.

17. The pretreated aluminum of claim 11 wherein the chromium compound is trivalent chromium sulfate.

18. The pretreated aluminum of claim 11 wherein the alkali metal zirconate is potassium hexafluorozirconate.

12. Pretreated aluminum and alloys of aluminum having a color recognized coating and improved corrosion-resistance, electrical conductivity, and adhesion properties comprising said aluminum and alloys of aluminum treated with an effective amount of an acidic aqueous solution having a pH ranging from about 3.7 to 4.0, and comprising per liter of said solution from about 0.01 to 10 grams of a water soluble trivalent chromium salt, about 0.01 to 8.0 grams of an alkali metal hexafluorozirconate, about 0.0 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, 0.01 to 10 grams of at least one water soluble divalent zinc salt and from 0 to 10 grams of at least one water soluble thickener.

19. The pretreated aluminum of claim 12 wherein the zinc salt is divalent zinc sulfate.

20. The pretreated aluminum of claim 12 wherein the zinc salt is zinc acetate.

21. A composition for pretreating aluminum and alloys of aluminum to provide a color recognizable coating and to improved the corrosion-resistance, electrical conductivity and adhesion properties of the coated aluminum which comprises an aqueous solution having a pH ranging from about 2.5 to 5.5 and per liter of 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 water soluble fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, alkali metal hexfluorosilicates and mixtures thereof, about 0.001 to 10 grams of at least one water soluble zinc compound and from 0 to 10 grams of at least one water soluble thickener.

22. The composition of claim 21 wherein the pH ranges from about 3.7 to 4.0.

23. The composition of claim 21 wherein the trivalent chromium compound is trivalent chromium sulfate basic.

24. The composition of claim 21 wherein the zinc compound is divalent zinc sulfate.

25. The composition of claim 21 wherein the zinc compound is divalent zinc acetate.