CORROSION RESISTANT ALUMINUM ALLOY SUBSTRATES AND METHODS OF PRODUCING THE SAME

• US 20090061216A1
• Filed: 08/28/2007
• Published: 03/05/2009
• Est. Priority Date: 08/28/2007
• Status: Active Grant

• Current Assignee: Howmet Aerospace, Inc.
• Original Assignee: Alcoa Incorporated (Howmet Aerospace, Inc.)
• Inventors: Vega, Luis Fanor, Zediak, Clinton, Levendusky, Thomas L., Robare, Kevin M., Guthrie, Joseph D., Askin, Albert
• Granted Patent: US 7,732,068 B2
• Time in Patent Office: Days
• US Class Current: 428/336
• CPC Class Codes: C23C 18/122 Inorganic polymers, e.g. silanes, polysilazanes, polysiloxanes
• CPC Class Codes: C25D 11/08 containing inorganic acids
• CPC Class Codes: C25D 11/16 Pretreatment , e.g. desmutting
• CPC Class Codes: C25D 11/24 Chemical after-treatment
• CPC Class Codes: Y10T 428/12569 Synthetic resin
• CPC Class Codes: Y10T 428/249953 Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/264 Up to 3 mils
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

Aluminum alloy products comprising an aluminum alloy base and a sulfate-phosphate oxide zone integral therewith are disclosed. Methods of making the same are also disclosed.

Claims

1. A method comprising:

producing a sulfate-phosphate oxide zone in an aluminum alloy base, wherein the producing step comprises electrochemically oxidizing a surface of the aluminum alloy base via an electrolyte comprising both phosphoric acid and sulfuric acid; and

forming a silicon-containing polymer zone integral with at least a portion of the sulfate-phosphate oxide zone, wherein the aluminum alloy base, the sulfate-phosphate oxide zone and the silicon-containing polymer zone at least partially define a corrosion resistant aluminum alloy substrate.

2. The method of claim 1, wherein the corrosion resistant aluminum alloy substrate is capable of passing a copper-accelerated acetic acid salt spray test, as defined by ASTM B368-97 (2003)e1.

3. The method of claim 1, wherein the electrochemically oxidizing step comprises applying current to the aluminum alloy base at a current density of at least about 12 amps per square foot.

4. The method of claim 1, wherein the electrochemically oxidizing step comprises applying current to the aluminum alloy base at a current density of at least about 18 amps per square foot.

5. The method of claim 1, wherein the electrolyte comprises at least about 0.1 wt % phosphoric acid.

6. The method of claim 7, wherein the electrolyte comprises not greater than about 5 wt % phosphoric acid.

7. The method of claim 1, wherein the electrochemically oxidizing step comprising heating the electrolyte to a temperature of at least about 75°

F.

8. The method of claim 1, wherein the electrochemically oxidizing step comprising heating the electrolyte to a temperature of at least about 90°

F.

9. The method of claim 1, further comprising:

prior to the forming a sulfate-phosphate oxide zone step, pretreating a surface of the aluminum alloy base with a pretreating agent.

10. The method of claim 9, wherein the pretreating agent comprises a chemical brightening composition that includes at least one of nitric acid, phosphoric acid and sulfuric acid.

11. The method of claim 9, wherein the pretreating agent comprises an alkaline cleaner.

12. The method of claim 9, further comprising:

prior to the forming a silicon-containing polymer zone step, applying at least one of a dye and a nickel acetate solution to at least a portion of the sulfate-phosphate oxide zone.

13. The method of claim 1, wherein the silicon-containing polymer zone comprises at least one of polysiloxane and polysilazane.

14. The method of claim 13, wherein the forming a silicon-containing polymer zone step comprises

depositing a colloid on at least a portion of the sulfate-phosphate oxide zone;

and

curing the colloid to form a gel comprising the silicon-containing polymer coating on the surface of the aluminum alloy base.

15. The method of claim 14, wherein the depositing step comprises:

applying a sufficient amount of the sol to both (a) fill pores of the sulfate-phosphate oxide zone and (b) form a coating comprising the silicon-containing polymer coating.

16. An aluminum alloy product comprising:

an aluminum alloy base; and

a sulfate-phosphate oxide zone integral with the base.

17. The aluminum alloy product of claim 16, wherein the sulfate-phosphate oxide zone comprises pores, and wherein the pores have an average pore size of at least about 10 nm.

18. The aluminum alloy product of claim 17, wherein the pores of the sulfate-phosphate oxide zone have an average pore size of not greater than at least about 15 nm.

19. The aluminum alloy product of claim 16, wherein the sulfate-phosphate oxide zone has a thickness of at least about 0.0002 inch.

20. The aluminum alloy product of claim 19, wherein the sulfate-phosphate oxide zone has a thickness of not greater than about 0.001 inch.

21. The aluminum alloy product of claim 16, wherein the aluminum alloy is a 6061 series alloy.

22. The aluminum alloy product of claim 21, wherein the aluminum alloy product is a forged product.

23. The aluminum alloy product of claim 22, wherein the aluminum alloy product is a wheel product.

24. The aluminum alloy product of claim 16, further comprising:

a silicon-containing polymer zone at least partially overlapping the sulfate-phosphate oxide zone, wherein the silicon-containing polymer zone comprises a coating portion on a surface of the aluminum alloy base.

25. The aluminum alloy product of claim 24, wherein the aluminum alloy product is capable of passing a copper-accelerated acetic acid salt spray test (CASS), as defined by ASTM B368-97 (2003)e1.

26. The aluminum alloy product of claim 24, wherein the coating portion of the silicon-containing polymer zone has a thickness of at least about 5 micron.

27. The aluminum alloy product of claim 24, wherein the coating portion of the silicon-containing polymer zone has a thickness of at least about 8 micron.

28. The aluminum alloy product of claim 24, wherein the coating portion of the silicon-containing polymer zone has a thickness of at least about 35 micron.

29. The aluminum alloy product of claim 28, wherein the coating portion of the silicon-containing polymer is substantially crack-free.

30. The aluminum alloy product of claim 29, wherein the silicon-containing polymer is polysilazane.