Alloy surface activation by immersion in aqueous acid solution

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.

What is claimed is: 
     
         1 . 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.   
     
     
         2 . The composition according to  claim 1 , wherein the liquid comprises the aqueous acid. 
     
     
         3 . The composition according to  claim 1 , wherein the liquid comprises one or more of the alcohol, the fatty acid, the oil, and the water. 
     
     
         4 . The composition according to  claim 2 , wherein the article is immersed in the liquid. 
     
     
         5 . The composition according to  claim 3 , wherein the article is immersed in the liquid. 
     
     
         6 . The composition according to  claim 1 , wherein the article comprises one or more of stainless steel, a nickel-base alloy, a cobalt-base alloy, and a titanium-base alloy. 
     
     
         7 . The composition according to  claim 6 , wherein the article comprises stainless steel.