Solution for removing aluminum oxide film and method for surface treatment of aluminum or aluminum alloy

Abstract

A solution for removing an aluminum oxide film from an aluminum or aluminum alloy surface, which includes a salt or oxide of a metal capable of substituting aluminum, a solubilizing agent for ions of the metal, and an alkali, and which has a pH Of 10 to 13.5. The removing solution makes it possible to form a film of the metal derived from the metal salt or oxide contained in the removing solution by dissolving away the oxide film from the aluminum or aluminum alloy surface at a low temperature and a high speed while restraining, as securely as possible, erosion of the aluminum or aluminum alloy surface. Besides, the removing solution ensures that even in the case where the thickness of the aluminum or aluminum alloy basis material is very small, the aluminum or aluminum alloy surface can be activated while assuredly leaving the aluminum or aluminum alloy basis material.

1 . A solution for removing an aluminum oxide film from an aluminum or aluminum alloy surface, comprising a salt or oxide of a metal capable of substituting aluminum, a solubilizing agent for ions of the metal, and an alkali and having a pH of 10 to 13.5. 
   
   
       2 . The solution for removing the aluminum oxide film of  claim 1 , further comprising a surfactant. 
   
   
       3 . A method for surface treatment of aluminum or the aluminum alloy, comprising the steps of:
 immersing a workpiece having aluminum or the aluminum alloy at least at the surface in the solution of  claim 1 , and   forming a substituent metal layer of the metal capable of substituting aluminum and contained in the solution on the aluminum or aluminum alloy surface while removing the aluminum oxide film from the aluminum or the aluminum alloy surface.   
   
   
       4 . The method for surface treatment of aluminum or the aluminum alloy of  claim 3 , wherein the workpiece is a body having the aluminum or aluminum alloy film formed on a surface of a non-aluminum material. 
   
   
       5 . The method for surface treatment of aluminum or the aluminum alloy of  claim 3 , wherein after the substituent metal layer is formed, a plating layer is formed. 
   
   
       6 . The method for surface treatment of aluminum or the aluminum alloy of  claim 3 , wherein after the substituent metal layer is formed, the substituent metal layer is removed by an acidic liquid having an oxidizing behavior. 
   
   
       7 . The method for surface treatment of aluminum or the aluminum alloy of  claim 6 , wherein after the substituent metal layer is removed by the acidic liquid having the oxidizing behavior, the aluminum or aluminum alloy is subjected to a zinc substitution treatment or a palladium treatment and is then plated. 
   
   
       8 . The method for surface treatment of aluminum or the aluminum alloy of  claim 6 , wherein after the substituent metal layer is removed by the acidic liquid having the oxidizing behavior, the aluminum or aluminum alloy is subjected directly to plating.