Method for forming film on aluminum or aluminum alloy, pretreatment liquid therefor, and product thereof

Abstract

In a method for forming a film on a surface of aluminum or an alloy thereof, first, an anodic oxide film is formed on a surface of aluminum, a pretreatment is performed by immersing the aluminum or the alloy thereof on which the anodic oxide film is formed in a pretreatment liquid, and a sealing treatment using a sealing treatment liquid containing lithium ions is performed on the anodic oxide film on the surface of the aluminum or the alloy thereof subjected to the pretreatment. The pretreatment liquid contains phosphate ions and a reaction-controlling agent and has a pH in a neutral to acidic range. The reaction-controlling agent contains a compound having a carboxy group or a salt thereof or contains a compound capable of forming a hydroxide ion in an aqueous solution. This method makes it possible to uniformly form a sealing product in pores of the film.

What is claimed is: 
     
         1 . A method for forming a film on a surface of aluminum or an aluminum alloy, comprising the steps of:
 forming an anodic oxide film on a surface of aluminum or an aluminum alloy;   performing a pretreatment by immersing, in a pretreatment liquid, the aluminum or the aluminum alloy on which the anodic oxide film is formed; and   performing a sealing treatment using a sealing treatment liquid containing lithium ions on the anodic oxide film present on the surface of the aluminum or the aluminum alloy subjected to the pretreatment,   wherein the pretreatment liquid contains phosphate ions and a reaction-controlling agent and has a pH in a neutral to acidic range, and the reaction-controlling agent contains a compound having a carboxy group or a salt thereof or contains a compound capable of forming a hydroxide ion in an aqueous solution.   
     
     
         2 . The method according to  claim 1 , wherein a concentration of the phosphate ions is 0.1 to 4.0 mol/L. 
     
     
         3 . The method according to  claim 1 , wherein a concentration of the reaction-controlling agent is at least 0.05 mol/L. 
     
     
         4 . The method according to  claim 1 , wherein a temperature of the pretreatment liquid is 10 to 50° C. 
     
     
         5 . The method according to  claim 1 , wherein an immersion time in the pretreatment liquid is at least 1.5 minutes. 
     
     
         6 . The method according to  claim 1 , wherein the compound having a carboxy group is a carboxylic acid or a salt thereof. 
     
     
         7 . The method according to  claim 1 , wherein the compound capable of forming a hydroxide ion in an aqueous solution is a hydroxide. 
     
     
         8 . The method according to  claim 1 , wherein the anodic oxide film has a thickness of 3 to 40 μm. 
     
     
         9 . The method according to  claim 1 , wherein in the sealing treatment step, a sealing product is formed in pores present in a surface of the anodic oxide film, and the sealing product is a lithium-aluminum hydrate containing at least LiH(AlO 2 ) 2 .5H 2 O. 
     
     
         10 . The method according to  claim 1 , wherein the pretreatment liquid is a buffer solution. 
     
     
         11 . A pretreatment liquid used for a pretreatment in a sealing treatment on an anodic oxide film by using a sealing treatment liquid containing lithium ions, the pretreatment liquid comprising:
 phosphate ions; and   a reaction-controlling agent,   wherein the pretreatment liquid has a pH in a neutral to acidic range, and the reaction-controlling agent contains a compound having a carboxy group or a salt thereof or contains a compound capable of forming a hydroxide ion in an aqueous solution.   
     
     
         12 . An aluminum or aluminum alloy product comprising:
 aluminum or an aluminum alloy; and   an anodic oxide film formed on a surface of the aluminum or the aluminum alloy,   wherein pores in a surface of the anodic oxide film formed on the aluminum or the aluminum alloy are sealed with a sealing product, the sealing product contains a lithium-aluminum hydrate, and the lithium-aluminum hydrate is uniformly formed from the surface of the anodic oxide film to pore bottom portions in the pores.