Process for treating aluminum with ferricyanide compound

• US 3,985,585 A
• Filed: 07/24/1975
• Issued: 10/12/1976
• Est. Priority Date: 09/21/1973
• Status: Expired due to Term

• Current Assignee: J N Tuttle Incorporated
• Original Assignee: J N Tuttle Incorporated
• Inventors: Ozolins, Jekabs, Tuttle, Bertha S.
• Primary Examiner(s): Kendall, Ralph S.
• Assistant Examiner(s): Wolfe, Jr., Charles R.
• Application Number:
  US05/598,713
• Time in Patent Office: 446 Days
• Field of Search: 148/6.1, 148/6.27, 252/387
• US Class Current: 148/273
• CPC Class Codes: C23C 22/66 Treatment of aluminium or alloys based thereon

Abstract

The invention is for an improved process for chemically forming a protective, color receptive coating on the surface of aluminum. The aluminum may be aluminum parts or substrates coated with a layer of aluminum. Absent conventional steps such as water rinses and the like, the process comprises cleaning the aluminum surface to the extent necessary, including desmutting, and contacting the part with a spray comprising an aqueous alkaline solution of a ferricyanide compound, with or without added oxygen, for a time sufficient to form the coating. The treatment is believed to be a chemical oxidizing step similar to the formation of an oxide film electrically using a conventional anodizing process.

Claims

1. A process for forming a corrosion and heat resistant, readily dyeable coating on member selected from the group of aluminum, its alloys, and substrates having an aluminum or aluminum alloy surface, said process comprising the step of formation of said coating using chemical means consisting of contacting the surface of said part with a spray comprising an aqueous alkaline solution of a ferricyanide salt having a pH between about 7.5 and 14.0, said ferricyanide salt being present in an amount of at least 0.01 moles per liter of solution.

2. The process of claim 1 where the ferricyanide salt is present in an amount of from 0.1 to 0.5 moles per liter of solution.

3. The process of claim 2 where the pH of the ferricyanide solution varies between about 7.5 and 14.

4. The process of claim 3 where the pH of the ferricyanide solution varies between about 10 and 13.

5. The process of claim 2 including the step of contacting the coated aluminum part with a colorant solution.

6. The process of claim 2 where the temperature of said solution varies between about 2°

F in excess of the freezing point of the solution and the boiling point of the solution.

7. The process of claim 6 where the temperature varies between about 70°

F and 100°

F.

8. The process of claim 2 where the ferricyanide solution contains a pH adjustor in an amount sufficient to provide the required pH which pH adjustor is selected from the group consisting of alkali carbonates, alkali or alkaline earth metal hydroxides, alkali tri-basic phosphates and mixtures thereof.

9. The process of claim 2 where the ferricyanide solution contains an inhibitor for aluminum that prevents darkening of the oxide coating and enhances dyeability.

10. The process of claim 9 where the inhibitor is a tri-basic phosphate contained in solution in an amount at from 0.01 moles per liter of solution to saturation.

11. The process of claim 2 wherein said spray is admixed with a member selected from the group of air and gaseous oxygen.

12. The process of claim 11 where the spray is admixed with gaseous oxygen at some point during the final five minutes of contact of the part with said treatment solution.

13. A process for forming a corrosion and heat resistant readily dyeable coating on a member selected from the group of aluminum, its alloys, and substrates having an aluminum or aluminum alloy surface, said process comprising the steps of formation of said coating using chemical means consisting of contacting the surface of said part with a spray comprising an aqueous alkaline solution of a ferricyanide salt in an amount of from 0.1 to 5 moles per liter, a carbonate salt in an amount of from 0.1 to 5 moles per liter and a trisodium phosphate salt in an amount sufficient to provide an alkaline pH.

14. The process of claim 13 where pH is ajusted to between 10 and 13.

15. The process of claim 13 where the temperature of the solution varies between room temperature and the boiling point of the solution.

16. The process of claim 13 where the spray is admixed with a gas selected from the group of air and oxygen.

17. The process of claim 16 where the volume of the gas is at least 0.001 cubic feet per gallon of solution.

18. The process of claim 17 where the volume of gas exceeds saturation.

19. The process of claim 16 where the gas is oxygen.

20. The process of claim 16 where the gas is mixed at some point during the latter 5 minutes of contact of the part with the treatment solution.