Post-treatment for metal coated substrates

• US 6,527,841 B2
• Filed: 11/06/2001
• Issued: 03/04/2003
• 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:
  US10/012,981
• Publication Number:
  US 20020053301A1
• Time in Patent Office: 483 Days
• Field of Search: 106/14.44, 106/14.21, 106/14.41, 148/247
• US Class Current: 106/14.44
• CPC Class Codes: B05D 3/10 by other chemical means
• CPC Class Codes: B05D 7/14 to metal, e.g. car bodies involving a chemical reaction between the metal and the coating C23
• 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

An aqueous composition for post-treating metal coated substrates such as cadmium-plated steel or zinc-nickel coated substrates and the process for using said composition to improve the corrosion-resistance, abrasion, and adhesion bonding properties of the metal coatings. The composition comprising an acidic aqueous solution having a pH ranging from about 2.5 to 4.5 containing effective amounts of trivalent chromium salts, an alkali metal hexafluorozirconate, at least one alkali metal fluoro-compound, and effective amounts of water soluble thickeners and/or surfactants.

Claims

1. A process for post-treating metal coated substrates to improve the corrosion-resistance, abrasion, and adhesion bonding properties which comprises treating the metal coated substrates 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 a least one fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, 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 solution is about room temperature.

3. The process of claim 2 wherein the trivalent chromium salt ranges from about 4 to 8 grams, the hexafluorozirconate ranges from about 6 to 10 grams, and the tetrafluoroborate ranges from about 0.12 to 1.2 grams.

4. The process of claim 3 wherein the thickener is a cellulose compound ranging from about 0.5 to 1.5 grams.

5. The process of claim 4 wherein the surfactant is a nonionic surfactant ranging from about 0.5 to 1.5 grams.

6. A process for post-treating metal coated substrates to improve the corrosion-resistance, abrasion, and adhesion bonding properties which comprises treating the metal coated substrates 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 tetrafluoroborate, hexafluorosilicate and mixtures thereof.

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

F.

8. The process of claim 6 wherein about 0.5 to 1.5 grams of a cellulose thickener is added to the acidic 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. The process of claim 6 wherein the metal coated substrate is a cadmium-plated steel.

12. The process of claim 6 wherein the metal coated substrate is a zinc-nickel alloy coated substrate.

13. A composition for post-treating metal coated substrates to improve the corrosion-resistance, abrasion, and adhesion bonding properties which comprises an acidic aqueous solution having a pH ranging from about 2.5 to 4.5, and containing 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.

14. The composition of claim 13 wherein the pH of the aqueous solution ranges from about 3.7 to 4.0.

15. The composition of claim 14 wherein the trivalent chromium salt ranges from about 4.0 to 8.0 grams, the hexafluorozirconate ranges from about 6.0 to 10 grams, and the tetrafluoroborate ranges from about 0.12 to 1.2 grams.

16. The composition of claim 15 wherein the thickener ranges from about 0.5 to 1.5 grams.

17. The composition of claim 16 wherein the surfactant ranges from about 0.5 to 1.5 grams.

18. A composition for post-treating metal coated substrates to improve the corrosion-resistance, abrasion, and adhesion bonding properties which consists essentially of an acidic aqueous solution having a pH ranging from about 3.7 to 4.0, and containing per liter of said solution, from about 4.0 to 8 grams of a water soluble trivalent chromium salt, about 6.0 to 10 grams of an alkali metal hexafluorozirconate, about 0.01 to 12 grams of at least one fluoro-compound selected from the group consisting of tetrafluoroborate, 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 a least one water soluble surfactant.

19. The composition of claim 18 wherein the tetrafluoroborate is present in the solution in an amount ranging from about 0.24 to 0.36 grams.

20. The composition of claim 19 wherein about 0.5 to 1.5 grams of a cellulose thickener is added to the solution.

21. The composition of claim 20 wherein the chromium salt is trivalent chromium sulfate.

22. The composition of claim 21 wherein the alkali metal zirconate is potassium hexafluorozirconate.