Aluminum-material anodization method

Abstract

Provided is an anodic oxidation treatment method for an aluminum material including aluminum or an aluminum alloy capable of forming a porous anodic oxide film of a porous type at a treatment voltage of 10 V or more while suppressing manifestation of a crystal grain pattern to the extent possible. Specifically, provided is an anodic oxidation treatment method for an aluminum material for subjecting an aluminum material to anodic oxidation treatment in a treatment bath of a polybasic acid aqueous solution under a treatment condition of a target voltage of 10 V or more, to form an anodic oxide film on a surface of the aluminum material, the method including, as pre-treatment of the anodic oxidation treatment, subjecting the aluminum material to anodic oxidation treatment in a treatment bath of a polybasic acid aqueous solution under a treatment condition of a voltage of 6 V or less until an electrical quantity reaches 0.05 C/cm 2 or more, to form a pre-film on the surface of the aluminum material.

1 . An anodic oxidation treatment method for an aluminum material for subjecting an aluminum material comprising aluminum or an aluminum alloy to anodic oxidation treatment in a treatment bath of a polybasic acid aqueous solution under a treatment condition of a target voltage of 10 V or more, to form a porous anodic oxide film on a surface of the aluminum material,
 the method comprising, as pre-treatment of the anodic oxidation treatment, subjecting the aluminum material to anodic oxidation treatment in a treatment bath of a polybasic acid aqueous solution under a treatment condition of a voltage of 6 V or less until an electrical quantity reaches 0.05 C/cm 2  or more, to form a porous pre-film on the surface of the aluminum material.   
     
     
         2 . An anodic oxidation treatment method for an aluminum material according to  claim 1 , wherein a crystal grain in the aluminum material has a size of 100 μm or more. 
     
     
         3 . An anodic oxidation treatment method for an aluminum material according to  claim 1  or  2 , wherein the aluminum material has a surface subjected to mirror treatment. 
     
     
         4 . An anodic oxidation treatment method for an aluminum material according to  claim 3 , wherein the mirror treatment is performed by any mirror processing selected from buff polishing, electropolishing, cutting processing, and chemical polishing. 
     
     
         5 . An anodic oxidation treatment method for an aluminum material according to  claim 1 , wherein the treatment bath to be used in the pre-treatment and the treatment bath to be used in the anodic oxidation treatment comprise aqueous solutions of the same polybasic acid. 
     
     
         6 . An anodic oxidation treatment method for an aluminum material according to  claim 1 , wherein the treatment bath to be used in the pre-treatment and the treatment bath to be used in the anodic oxidation treatment comprise aqueous solutions of different polybasic acids. 
     
     
         7 . An anodic oxidation treatment method for an aluminum material according to  claim 1 , the method further comprising, when performing the anodic oxidation treatment of the aluminum material, performing pre-film removal treatment for removing the porous pre-film formed in the pre-treatment. 
     
     
         8 . An anodic oxidation treatment method for an aluminum material according to  claim 7 , wherein the pre-film removal treatment is performed during or after the anodic oxidation treatment. 
     
     
         9 . An anodic oxidation treatment method for an aluminum material according to  claim 8 , wherein the pre-film removal treatment during the anodic oxidation treatment comprises, when performing the anodic oxidation treatment of the aluminum material after the pre-treatment, performing the anodic oxidation treatment with an electrical quantity 50 times or more as large as the electrical quantity applied in the pre-treatment, to dissolve the porous pre-film formed in the pre-treatment in the treatment bath of the anodic oxidation treatment to thereby remove the porous pre-film. 
     
     
         10 . An anodic oxidation treatment method for an aluminum material according to  claim 8 , wherein the pre-film removal treatment after the anodic oxidation treatment comprises immersing the aluminum material after the anodic oxidation treatment in an acid or alkaline aqueous solution, to chemically dissolve the porous pre-film remaining on a surface after the anodic oxidation treatment to thereby remove the porous pre-film. 
     
     
         11 . An anodic oxidation treatment method for an aluminum material according to  claim 1 , the method further comprising, when performing the anodic oxidation treatment of the aluminum material after the pre-treatment, performing pre-film partial dissolution treatment for dissolving the porous pre-film formed on the aluminum material after the pre-treatment under treatment conditions in which 10% or more of a wall thickness of the porous pre-film remains. 
     
     
         12 . An anodic oxidation treatment method for an aluminum material according to  claim 11 , wherein the partial dissolution treatment of the porous pre-film comprises treating the aluminum material after the pre-treatment under treatment conditions preliminarily determined by preparing a test sample which is substantially the same as the aluminum material after the pre-treatment, and determining treatment conditions in which 10% or more of a wall thickness between pores of the pre-film remains through use of the test sample.