JPH06316787A - Treatment of surface of anodized alminum layer - Google Patents

Abstract

PURPOSE:To clog fine pores in an anodized aluminum layer and to improve the characteristics of the anodized aluminum layer by immersing an Al member having an anodized aluminum film on the surface by anodic oxidation in an alcohol soln. having a specified compsn. contg. alkoxysilane. CONSTITUTION:Power is supplied to an Al or Al alloy member as the anode in an acidic soln., and an anodized aluminum layer as an anodically oxidized film constituted of Al2O3 is formed thereon. Since multistage fine pores are present in the anodized aluminum layer, it is immersed in an alcohol soln. contg. 0.5 to 0.8mol H2 and <0.01mol HCl based on 1mol of the amt. of <=2wt.% alkoxysilane which is expressed by SiXn(OR)4-n {X; H or CH3, R; CH3 or CH2H5 and (n)=0 or 1} expressed in terms of SiO2, and the fine pores in the anodized aluminum layer are packed and clogged by SiO2, and a uniform SiO2 layer is formed on the surface of the anodized aluminum layer, thereby, the Al member having a surface treated layer excellent in corrosion resistance, heat resistance, wear resistance and hardness can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method of alumite for densifying a surface coating of alumite.

[0002]

2. Description of the Related Art Conventionally, an anodic oxidation method has been widely used as a surface treatment technology for aluminum, in which an aluminum anode is electrolyzed in a solution of oxalic acid, sulfuric acid or the like to form a film of aluminum oxide on the surface of aluminum.

This is generally called anodized aluminum and is widely used as a material for household products, building materials, machine parts, vehicle parts, ornaments and the like. This is because it has excellent properties such as corrosion resistance, heat resistance, wear resistance, and hardness as compared with aluminum.

However, the alumite film is porous,
It is known that there are an extremely large number of micropores. In order to prevent the adverse effects of these fine pores, treatments such as hot water treatment and chromic acid treatment are carried out, but they are not always perfect, and highly toxic chemicals must be used. There are drawbacks that are difficult to process.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the above-mentioned drawbacks and further improves various properties of alumite by filling SiO ₂ in the fine pores of the alumite coating to densify the surface coating. That is the purpose.

[0006]

It is known that ions such as OH ⁻ , Al ³⁺ and O ²⁻ are contained in the pore wall, especially the bottom wall of the porous layer of the alumite coating. The present inventors have found that among these ions, OH ⁻ preferentially reacts with the alkoxide condensate to fill the fine pores. The present invention has been made based on this finding.

The present invention uses anodized aluminum
_{SiX n (OR) 4-n} ( where X is H or _CH 3,
R contains CH ₃ or C ₂ H ₅ and at least one kind of alkoxysilane represented by 0 or 1), and 0.5 mol or more and 0.1 mol.
The fine pores of the alumite coating are filled by immersing in an alcohol solution containing 8 mol or less of H ₂ O and 0.01 mol or less of HCl.

[0008] The above-mentioned alcohol solution contains Si when it is assumed that the alkoxysilane is chemically changed to 100% SiO _2.
O ₂ is a solution containing 2% or less by weight.

It is preferable that this solution is left to stand at room temperature for 24 hours or more after preparation to be aged. By this aging, Si—O—Si skeleton molecules having a low degree of condensation are generated, and since these are small molecules, they easily enter even micropores with a diameter of about 5 nm.
Reacts with OH ^{− in the} micropores to increase the degree of condensation and fill the micropores.
Then, it is dried at a temperature of 100 to 150 ° C. and the solvent is removed to form a dense film.

Further, according to the present invention, not only the fine pores can be filled, but also the surface of the alumite can be uniformly covered with the SiO ₂ film. In this case, since the alkoxysilane is condensed, the vapor pressure is low, it does not evaporate during drying, and SiO ₂ is uniformly formed as a strong film on the alumite surface after drying.

The alcohol used in the present invention may be methanol, ethanol or the like. In addition, since the prepared alcohol solution has a sufficiently low degree of condensation of alkoxysilane,
The life of the solution is long.

[0012]

Example A methanol solution containing 1% of Si (OCH ₃ ) ₄ in terms of SiO ₂ , 0.75 mol of H ₂ O and 0.005 mol of HCl was prepared. This solution at room temperature
After standing for 0 hour for aging, an anodized aluminum plate was immersed in this solution.

After the plate was taken out of the solution and dried at 130 ° C. for 1 hour, microscopic observation of micropores on the alumite surface revealed that the micropores were completely and firmly filled. As a result of identifying the filling material, it was found to be SiO ₂ .

[0014]

According to the present invention, the surface coating of alumite can be densified. This densification can further improve the properties of alumite.
Further, the solution prepared according to the present invention has a long life and is characterized in that problems such as pollution do not occur.

Claims (2)

[Claims] 1. Anodized aluminum is added to SiX _n
(OR) _4-n (where X is H or CH ₃ , R is CH
₃ or C ₂ H ₅ , n is at least one of the alkoxysilanes represented by 0 or 1), and is 0.5 mol or more and 0.8 mol with respect to 1 mol of the alkoxysilane.
A surface treatment method for an alumite, which comprises immersing in an alcohol solution containing the following H ₂ O and 0.01 mol or less of HCl. 2. The method for surface treatment of alumite according to claim 1, which is an alcohol solution containing 2% by weight or less of alkoxysilane in terms of SiO ₂ .