ALLOY SURFACE ACTIVATION BY IMMERSION IN AQUEOUS ACID SOLUTION

• US 20170081767A1
• Filed: 05/06/2015
• Published: 03/23/2017
• Est. Priority Date: 05/06/2014
• Status: Active Grant

• Current Assignee: Case Western Reserve University
• Original Assignee: Case Western Reserve University
• Inventors: Li, Zhen, Ernst, Frank, Kahn, Harold, Heuer, Arthur
• Granted Patent: US 10,450,658 B2
• Time in Patent Office: Days
• CPC Class Codes: C23C 22/02 using non-aqueous solutions
• CPC Class Codes: C23C 22/06 using aqueous acidic solutions with pH less than 6
• CPC Class Codes: C23C 22/50 Treatment of iron or alloys based thereon
• CPC Class Codes: C23C 22/78 Pretreatment of the material to be coated
• CPC Class Codes: C23C 8/02 Pretreatment of the material to be coated C23C8/04 takes precedence
• CPC Class Codes: C23G 1/02 with acid solutions
• CPC Class Codes: C23G 1/08 Iron or steel
• CPC Class Codes: C25D 5/48 After-treatment of electroplated surfaces
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

A process for surface activation or depassivation of an article, in particular an alloy, by immersion of the alloy in an aqueous acid solution. The surface activation methods of the present invention can be performed during a relatively short period of time and achieve reductions in production costs and provide environmental friendliness as compared to prior art processes. In a further embodiment, after surface activation, the article is immersed in a second liquid that prevents re-formation of a passivating oxide layer on the surface of the article. In a further embodiment the surface-activated alloys are subjected to surface engineering by a process that infuses carbon or nitrogen through the surface at a temperature sufficiently low to suppress precipitation of carbides or nitrides.

Claims

1. A process for preventing oxidation of a surface of an alloy article, comprising the steps of:

activating at least one surface portion of an alloy article; and

contacting the at least one surface portion of the article with a liquid comprising one or more of an alcohol, an aqueous acid, a fatty acid, an oil, and water prior to formation of a passivating layer on the at least one surface portion.

2. The process according to claim 1, wherein the activating step takes place outside of a CSS processing furnace.

3. The process according to claim 2, further including the step of transferring the article contacted with the liquid to a processing furnace and evaporating the liquid from the at least one surface portion of the alloy article.

4. The process according to claim 3, wherein the activating step is performed with an aqueous acid solution.

5. The process of claim 4, wherein the alloy article comprises one or more of stainless steel, a nickel-base alloy, a cobalt-base alloy, and a titanium-base alloy.

6. A process for activating a surface of an alloy article, comprising the steps of:

obtaining an article comprising an alloy; and

activating at least one surface of the article with an aqueous acid solution.

7. The process according to claim 6, wherein the aqueous acid solution comprises one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid and sulfuric acid.

8. The process according to claim 7, wherein the article comprises one or more of stainless steel, a nickel-base alloy, a cobalt-base alloy, and a titanium-base alloy.

9. The process according to claim 7, wherein acid pH value of the solution ranges from about +4 to about −

1.

10. The process according to claim 6, further including the step of moving the article from the aqueous acid solution and placing the article in a liquid that prevents oxidation of the at least one surface of the article.

11. The process according to claim 10, wherein the liquid comprises one or more of an alcohol, a fatty acid, an oil, and water.

12. The process according to claim 6, wherein the activating step takes place outside of a CSS processing furnace.

13. The process according to claim 12, further including the step of transferring the article to the processing furnace and evaporating the aqueous acid solution from the at least one surface of the article.

14. A surface activated article-containing composition, comprising:

an article having at least one portion of its surface activated; and

a liquid covering the at least one portion for temporarily preventing the formation of a passivating layer on the at least one activated portion, the liquid comprising one or more of an aqueous acid, a fatty acid, an alcohol, water, and oil.

15. The composition according to claim 14, wherein the liquid comprises the aqueous acid.

16. The composition according to claim 14, wherein the liquid comprises one or more of the alcohol, the fatty acid, the oil, and the water.

17. The composition according to claim 15, wherein the article is immersed in the liquid.

18. The composition according to claim 16, wherein the article is immersed in the liquid.

19. The composition according to claim 14, wherein the article comprises one or more of stainless steel, a nickel-base alloy, a cobalt-base alloy, and a titanium-base alloy.

20. The composition according to claim 19, wherein the article comprises stainless steel.