Aluminum Treatment Composition

• US 20090242081A1
• Filed: 03/26/2008
• Published: 10/01/2009
• Est. Priority Date: 03/26/2008
• Status: Abandoned Application

• Current Assignee: Macdermid Incorporated (Element Solutions Inc)
• Original Assignee: Macdermid Incorporated (Element Solutions Inc)
• Inventors: Bauer, Richard, Malik, Michael
• Application Number:
  US12/055,539
• Publication Number:
  US 20090242081A1
• Time in Patent Office: Days
• US Class Current: 148/267
• CPC Class Codes: C09D 1/00 Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• CPC Class Codes: C09D 5/103 containing Al
• CPC Class Codes: C23C 22/34 containing fluorides or complex fluorides
• CPC Class Codes: C23C 22/44 containing also 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 conversion coating composition for treating metal substrates such as aluminum, aluminum alloys, zinc, zinc alloys, magnesium, magnesium alloys and steel to provide a conversion coating thereon. The conversion coating composition comprises a) a source of aluminum ions; b) a fluoro compound; c) at least one pH adjuster; d) a source of Group VIB metal ions selected from the group consisting of tungstate ions and trivalent chromium ions; and e) optionally, a preservative. The conversion coating composition provides a corrosion resistant coating on the metal surface and improves the adhesion of subsequently applied layers.

Claims

1. An aqueous conversion coating composition comprising:

(a) a source of aluminum ions;

(b) a fluoro compound;

(c) at least one pH adjuster;

(d) a source of at least one Group VIB metal ion selected from the group consisting of tungstate ions and trivalent chromium ions; and

(e) optionally, a preservative;

wherein the composition has a pH of 0.5 to 6 and the source of aluminum ions is selected from the group consisting of (i) ammonium hexafluoride aluminate, (ii) alkali metal hexafluoride aluminates, and (iii) aluminum powder in combination with hexafluoro titanic acid.

2. The aqueous conversion coating composition according to claim 1, wherein the conversion coating composition does not contain chromium or phosphorus.

3. The aqueous conversion coating composition according to claim 1, wherein:

the fluoro compound comprises hexafluorotitanic acid;

the source of aluminum ions comprises aluminum metal; and

the Group VIB metal ion comprises a source of tungstate ions.

4. The aqueous conversion coating composition according to claim 1, wherein the one or more pH adjusters comprises ammonium bicarbonate or ammonium carbonate.

5. The aqueous conversion coating composition according to claim 1, wherein the Group VIB metal ion is selected from the group consisting of ortho-tungstates, meta-tungstates and para-tungstates, polytungstates, hetero-polytungstates, isopolytungstates, peroxytungstates, and combinations thereof.

6. The aqueous conversion coating composition according to claim 5, wherein the Group VIB metal ion is selected from the group consisting of sodium, potassium, lithium, calcium, cerium, barium, magnesium, strontium, hydrogen and ammonium tungstate salts.

7. The aqueous conversion coating composition according to claim 6, wherein the Group VIB metal ion is selected from the group consisting of ammonium metatungstate, potassium metatungstate, sodium metatungstate, tungstic acid, sodium tungstate, potassium tungstate and ammonium tungstate.

8. The aqueous conversion coating composition according to claim 7, wherein the Group VIB metal ion comprises ammonium metatungstate.

9. The aqueous conversion coating composition according to claim 1, wherein:

the source of aluminum ions and the source of fluoro ions comprises ammonium hexafluoride aluminate;

the composition contains a preservative; and

the group VIB metal ion comprises a source of trivalent chromium ions.

10. The aqueous conversion coating composition according to claim 9, wherein the at least one pH adjuster comprises a material selected from the group consisting of organic acid, and ammonium bicarbonate.

11. The aqueous conversion coating composition according to claim 10, wherein the organic acid comprises benzoic acid.

12. The aqueous conversion coating composition according to claim 9, wherein the preservative comprises hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine.

13. The aqueous conversion coating composition according to claim 9, wherein the source of trivalent chromium ions comprises basic chrome sulfate.

14. A method of treating a metal substrate to form a conversion coating thereon, the method comprising the steps of

(a) contacting the metal substrate with a composition comprising:

i) a source of aluminum ions;

ii) a fluoro compound;

iii) at least one pH adjuster;

iv) a source of at least one Group VIB metal ion selected from the group consisting of tungstate ions and trivalent chromium ions; and

v) optionally, a preservative; and

(b) thereafter drying the treated metal surface;

wherein the composition has a pH of 0.5 to 6 and the source of aluminum ions is selected from the group consisting of (i) ammonium hexafluoride aluminate, (ii) alkali metal hexafluoride aluminates, and (iii) aluminum powder in combination with hexafluoro titanic acid.

15. The method according to claim 14, wherein the metal substrate is selected from the group consisting of aluminum, aluminum alloys, magnesium, magnesium alloys, zinc, zinc alloys, steel, and combinations of one or more of the foregoing.

16. The method according to claim 14, wherein the conversion coating composition does not contain chromium or phosphorus.

17. The method according to claim 16, wherein:

the fluoro compound comprises hexafluorotitanic acid;

the source of aluminum ions comprises aluminum metal; and

the group VIB metal ion comprises a source of tungstate ions.

18. The method according to claim 14, wherein the one or more pH adjusters comprises ammonium bicarbonate or ammonium carbonate.

19. The method according to claim 14, wherein the Group VIB metal ion is selected from the group consisting of ortho-tungstates, meta-tungstates and para-tungstates, polytungstates, hetero-polytungstates, isopolytungstates, peroxytungstates, and combinations thereof.

20. The method according to claim 19, wherein the Group VIB metal ion selected from the group consisting of sodium, potassium, lithium, calcium, cerium, barium, magnesium, strontium, hydrogen and ammonium tungstate salts.

21. The method according to claim 20, wherein the Group VIB metal ion is selected from the group consisting of ammonium metatungstate, potassium metatungstate, sodium metatungstate, tungstic acid, sodium tungstate, potassium tungstate and ammonium tungstate.

22. The method according to claim 21, wherein the Group VIB metal ion comprises ammonium metatungstate.

23. The method according to claim 14, wherein the source of aluminum ions and the source of fluoro ions comprises ammonium hexafluoride aluminate;

the composition contains a preservative; and

the group VIB metal ion comprises a source of trivalent chromium ions.

24. The method according to claim 23, wherein the at least one pH adjuster comprises a material selected from the group consisting of organic acid and, and ammonium bicarbonate.

25. The method according to claim 24, wherein the organic acid comprises benzoic acid.

26. The method according to claim 23, wherein the preservative comprises hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine.

27. The method according to claim 23, wherein the source of trivalent chromium ions comprises basic chrome sulfate.