Post-treatment for metal coated substrates

• US 6,663,700 B1
• Filed: 01/23/2003
• Issued: 12/16/2003
• Est. Priority Date: 10/31/2000
• Status: Expired due to Term

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Nickerson, William C. Jr., Matzdorf, Craig A.
• Primary Examiner(s): Green, Anthony J.
• Application Number:
  US10/351,751
• Time in Patent Office: 327 Days
• Field of Search: 106/14.21, 106/14.41, 106/14.44, 148/247, 148/267, 148/275, 428/472, 428/472.1
• US Class Current: 106/14.44
• CPC Class Codes: C09D 5/084 Inorganic compounds
• 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

Aqueous compositions for post-treating metal coated substrates such as cadmium-plated steel, and zinc-nickel coated substrates and the process for using said compositions to provide a color recognizable coating and to improve the corrosion-resistance, abrasion, electrical, and adhesion properties of the coating. The post-treatment composition comprises an acidic aqueous solution having a pH ranging from about 2.5 to 5.5 and contains effective amounts of trivalent chromium compounds, alkali metal hexafluorozirconates, at least one divalent zinc compound, alkali metal fluoro-compounds, and effective amounts of water soluble thickeners, wetting agents or surfactants.

Claims

1. A process for post-treating metal coated substrates to provide color recognition, and improve the corrosion-resistance, abrasion, and adhesion properties which comprises treating the metal coated substrates with an acidic aqueous solution having a pH ranging from about 2.5 to 5.5 comprising, 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 a least one fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, alkali metal hexafluorosilicates and mixtures thereof, from about 0.001 to 10 grams of a divalent zinc compound, 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.

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 ranges from about room temperature to 200°

F.

3. The process of claim 2 wherein the trivalent chromium compound ranges from about 0.01 to 10 grams, the hexafluorozirconate ranges from about 0.01 to 8.0 grams, and the tetrafluoroborate ranges from about 0.01 to 1.2 grams.

4. The process of claim 2 wherein the thickener is a cellulose compound ranging from about 0.5 to 1.5 grams.

5. The process of claim 1 wherein the zinc compound is divalent zinc sulfate.

6. A process for post-treating metal coated substrates to provide color recognition and improve the corrosion-resistance, abrasion, and adhesion properties which comprises treating the metal coated substrates with an aqueous solution having a pH ranging from about 2.5 to 5.5 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 0.001 to 10 grams of a divalent zinc compound and about 0.01 to 1.2 grams of at least one fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, hexafluorosilicates and mixtures thereof.

7. The process of claim 6 wherein the zinc compound is divalent zinc sulfate.

8. The process of claim 6 wherein about 0.5 to 1.5 grams of a cellulose thickener is added to the solution.

9. The process of claim 6 wherein the chromium salt is trivalent chromium sulfate basic and the divalent zinc compound is zinc acetate.

10. The process of claim 6 wherein the alkali metal hexafluorozirconate 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. Composition for post-treating metal coated substrates to provide color recognition, and improve the corrosion-resistance, abrasion, and adhesion properties of the coating which comprises an acidic aqueous solution having a pH ranging from about 2.5 to 5.5, and contains 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 0.001 to 10 grams of a divalent zinc compound, 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, and from 0 to 10 grams of at least one water soluble thickener.

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 compound ranges from about 0.01 to 10 grams, the hexafluorozirconate ranges from about 0.01 to 8.0 grams, and the tetrafluoroborate ranges from about 0.12 to 0.24 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 zinc compound is divalent zinc sulfate and the chromium compound is trivalent chromium sulfate.

18. Composition for post treating metal coated substrates to provide color recognition, and improve the corrosion-resistance, abrasion, and adhesion bonding properties of the coating which comprises an acidic aqueous solution having a pH ranging from about 3.7 to 4.0, and contains per liter of said solution, water soluble compounds, ranging from about 0.01 to 10 grams of a trivalent chromium compound, about 0.01 to 8.0 grams of an alkali metal hexafluorozirconate, from about 0.01 to 5.0 grams of a divalent zinc salt, about 0.01 to 1.2 grams of at least one fluoro-compound selected from the group consisting of alkali metal tetrafluoroborates, alkali metal hexafluorosilicates and mixtures thereof, and from 0.5 to 1.5 grams of at least one water soluble thickener.

19. The composition of claim 18 wherein the tetrafluoroborate is present in the solution in an amount ranging from about 0.12 to 0.24 grams.

20. The composition of claim 19 wherein the zinc salt is divalent zinc sulfate.

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

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

23. Post-treated metal coated substrates having a color recognized coating and improved corrosion-resistance, electrical conductivity, abrasion, and adhesion properties which comprises said metal coated substrates treated with 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.

24. The post-treated metal coated substrates of claim 23 wherein the trivalent chromium compound ranges from about 0.01 to 10 grams, the hexafluorozirconate ranges from about 0.01 to 8.0 grams, and the tetrafluoroborate ranges from about 0.01 to 1.2 grams.

25. The post-treated metal coated substrates of claim 23 wherein the thickener ranges from about 0.5 to 1.5 grams.

26. The post-treated metal coated substrates of claim 23 wherein the zinc compound is divalent zinc acetate.

27. The post-treated metal coated substrates of claim 23 wherein the tetrafluoroborate is present in the solution in an amount ranging from about 0.12 to 0.24 grams.

28. The post-treated metal coated substrates of claim 23 wherein the chromium compound is trivalent chromium sulfate and the zinc compound is divalent zinc sulfate.

29. The post-treated metal coated substrates of claim 23 wherein the alkali metal hexafluorozirconate is potassium hexafluorozirconate.

30. The post-treated metal coated substrates of claim 23 wherein the zinc compound is divalent zinc sulfate and the pH of the acidic aqueous solution ranges from 3.7 to 4.0.