Method For Forming An Oxide Layer On A Brazed Article

Abstract

In a method for treating an aluminum article ( 10 ), flux is applied to an outer surface of the aluminum article ( 10 ). The outer surface of the aluminum article ( 10 ) is brazed. An oxide layer ( 36 ) is formed on the outer surface of the aluminum article ( 10 ) by anodizing the aluminum article ( 10 ), where a portion of the oxide layer ( 36 ) is formed between the flux and the outer surface of the aluminum article ( 10 ).

1 . A method comprising:
 applying flux to an outer surface of an aluminum article;   brazing the outer surface of the aluminum article;   forming an oxide layer on the outer surface of the aluminum article by anodizing the aluminum article, wherein a portion of the oxide layer is formed between a flux residue produced by the brazing and the outer surface of the aluminum article.   
     
     
         2 . The method of  claim 1 , wherein forming an oxide layer comprises:
 contacting a portion of the outer surface of the aluminum article with an electrolyte solution;   applying an electric current through the electrolyte solution, wherein the outer surface of the aluminum article serves as an anode.   
     
     
         3 . The method of  claim 2 , wherein the electrolyte solution comprises an acid selected from the group consisting of sulfuric acid, oxalic acid, boric acid, phosphoric acid, chromic acid and combinations thereof. 
     
     
         4 . The method of  claim 2 , wherein the electric current is pulsed direct current or alternating current. 
     
     
         5 . The method of  claim 2 , wherein the electric current has a current density between about 100 amperes per square meter and about 300 amperes per square meter. 
     
     
         6 . The method of  claim 5 , wherein the electric current forms an electric field having an average voltage less than about 175 volts. 
     
     
         7 . The method of  claim 1 , further comprising:
 removing the flux from the outer surface of the aluminum article after forming the oxide layer on the outer surface.   
     
     
         8 . The method of  claim 1 , further comprising:
 applying a coating to the aluminum article, wherein a portion of the coating is applied over the oxide layer.   
     
     
         9 . The method of  claim 1 , further comprising:
 sealing the outer surface of the aluminum article.   
     
     
         10 . The method of  claim 1 , wherein the oxide layer formed has a thickness between about 1 micron and about 10 microns. 
     
     
         11 . The method of  claim 3 , wherein the oxide layer is formed by reacting aluminum on the outer surface of the aluminum article to form aluminum oxide. 
     
     
         12 . The method of  claim 1 , wherein the electrolyte solution deposits silicate or phosphate compounds in the oxide layer to form a ceramic oxide layer. 
     
     
         13 . The method of  claim 1 , wherein the electrolyte solution contains a titanium oxide, and wherein the titanium oxide deposits metal ions to form the oxide layer. 
     
     
         14 . An aluminum article produced by the process of  claim 1 . 
     
     
         15 . An aluminum article produced by the process of  claim 1 , wherein the aluminum article is a heat exchanger. 
     
     
         16 . A method for treating an aluminum article having residual flux on an outer surface, the method comprising:
 anodizing the aluminum article to form an oxide layer between the residual flux and the outer surface of the aluminum article; and   removing the residual flux from the aluminum article.   
     
     
         17 . The method of  claim 14 , further comprising:
 applying a coating to the aluminum article, wherein a portion of the coating is applied over the oxide layer.   
     
     
         18 . The method of  claim 14 , wherein the oxide layer formed has a thickness between about 1 micron and about 10 microns. 
     
     
         19 . The method of  claim 14 , wherein anodizing the aluminum article comprises:
 contacting a portion of the outer surface of the aluminum article with an electrolyte solution;   applying an electric current through the electrolyte solution, wherein the outer surface of the aluminum article serves as an anode.   
     
     
         20 . The method of  claim 17 , wherein the oxide layer forms by reacting aluminum on the outer surface of the aluminum article to form aluminum oxide. 
     
     
         21 . The method of  claim 17 , wherein the electrolyte solution deposits silicate or phosphate compounds to form a ceramic oxide layer. 
     
     
         22 . The method of  claim 17 , wherein the electrolyte solution contains a titanium oxide, and wherein the titanium oxide deposits metal ions to form the oxide layer.