Surface dyeing process for welded metal articles

Abstract

A surface treatment process for a welded metal article includes following steps. Firstly, a metal article with a weld joint region is provided. Secondly, the metal article is anodized to form an anodic oxide layer on a surface thereof. Thirdly, the surface of the anodized metal article is rinsed. Fourthly, at least the anodized surface of the metal article in the region of the weld joint region is activated in a nitric acid solution. Fifthly, the anodized surface (i.e., the anodic oxide layer) of the metal article is dyed. Sixthly, the anodic oxide layer of the metal article is sealed. Finally, the metal article is rinsed.

1 . A surface treatment process for a metal article, comprising the steps of:
 providing a metal article with a weld joint region;   anodizing the metal article to form an anodic oxide layer on a surface of the metal article, the surface including the weld joint region;   activating at least the anodic oxide layer of the weld joint region of the metal article, the activating being performed in a nitric acid solution; and   dyeing the anodic oxide layer of the metal article.   
     
     
         2 . The surface treatment process as claimed in  claim 1 , wherein the metal article is comprised of at least one of aluminum, magnesium, and titanium. 
     
     
         3 . The surface treatment process as claimed in  claim 1 , further comprising a pretreatment process before the step of anodizing the metal article, the pretreatment process including a step of degreasing the surface of the metal article and a step of polishing the surface of the metal article. 
     
     
         4 . The surface treatment process as claimed in  claim 3 , further comprising a step of dipping the metal article in a chromic acid solution. 
     
     
         5 . The surface treatment process as claimed in  claim 1 , wherein the anodizing of the metal article involves a cleaning step and an electrolysis step, the cleaning step being carried out in an alkaline solution, the electrolysis step being carried out in an electrolyte. 
     
     
         6 . The surface treatment process as claimed in  claim 5 , wherein the electrolyte contains phosphoric acid in an approximate range from 0.2˜1.0 wt. %, using the metal article as an anode. 
     
     
         7 . The surface treatment process as claimed in  claim 6 , wherein during the electrolysis step, the metal article is anodized in the electrolyte at a current density in an approximate range from 10˜50 milliamperes per square centimeter, with a direct current in an approximate range from 20 volts to 60 volts applied thereto. 
     
     
         8 . The surface treatment process as claimed in  claim 5 , wherein the electrolyte contains sulfuric acid at a concentration in an approximate range from 100 g/l to 200 g/l. 
     
     
         9 . The surface treatment process as claimed in  claim 6 , wherein during the electrolysis step, the metal article is anodized in the electrolyte at a current density in an approximate range from 10˜20 milliamperes per square centimeter, at a temperature in an approximate range from 20° C. to 26° C. 
     
     
         10 . The surface treatment process as claimed in  claim 1 , wherein the dyeing of the anodic oxide layer of the metal article is carried out in a dye solution containing an organic dye at a concentration in an approximate range from 1 g/l to 10 g/l. 
     
     
         11 . The surface treatment process as claimed in  claim 1 , further comprising a sealing step performed after the step of dyeing the anodic oxide layer. 
     
     
         12 . The surface treatment process as claimed in  claim 11 , wherein the sealing step is carried out in a nickel salt solution. 
     
     
         13 . The surface treatment process as claimed in  claim 1 , wherein the nitric acid has a concentration in an approximate range from 10 wt. % to 30 wt. %.