JP2003301297A - Method for forming anode oxidation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming an anode oxidation film which is a heat-resistant, clear, enamel-like barrier film, holds the gloss of the surface of a base magnesium material, is corrosion-resistant, and can be baked at a high temperature when coated, enabling a coating film excellent in adhesiveness to be formed thereon. <P>SOLUTION: In this method for forming an anode oxidation film, the surface of magnesium or a magnesium alloy is subjected to anode oxidation in an electrolytic solution containing a tertiary amine, water in a content of 5-50 mass%, and an organic solvent; thus, a method is provided for producing a magnesium product or a magnesium alloy product which has a heat-resistant, clear, enamel-like barrier film, holds the gloss of the surface of a base metal, and is corrosion-resistant. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming an anodized film on the surface of magnesium or a magnesium alloy, and more specifically, it is possible to improve heat resistance by anodizing treatment using an electrolytic solution having a novel composition. A magnesium product or magnesium alloy product that has a transparent and transparent enamel-like barrier film, is corrosion resistant, and can be baked at high temperature even when applied to form a film with excellent adhesion Regarding the method.

[0002]

2. Description of the Related Art Magnesium and magnesium alloys (in the following description, when referred to as magnesium materials include both magnesium and magnesium alloys) are the lightest of practical metals and have a large specific strength. Utilizing the characteristics, interior and exterior parts of automobiles and motorcycles, parts of home appliances, bags, storage containers such as suitcases, sports equipment, parts of optical equipment, canes, and even computers, acoustics, etc. Application to the field has also been tried and put into practical use.

However, since the magnesium material is the most active metal material among the practical metals, it is difficult to use the material as it is from the viewpoint of corrosion resistance, and the magnesium material is immediately oxidized in the atmosphere and the surface thereof is oxidized. Since a thin film is formed on the surface, it has a drawback that it is difficult to apply and the adhesion of the coating film is significantly lowered.

As a surface treatment method for improving the corrosion resistance and coating film adhesion of magnesium materials, chemical conversion treatment and anodic oxidation treatment have been conventionally carried out, and an aqueous treatment liquid or electrolytic solution has been used. . In particular, when a film is formed by anodizing treatment and then a sealing treatment is performed, a relatively uniform film is formed, so these treatments are used as a rust preventive treatment or a base treatment for coating.

Further, since the magnesium material has a metallic luster, it is desirable to give the product of the magnesium material a decorative property utilizing the metallic luster, but since the surface of the magnesium material is easily oxidized, its initial stage In order to maintain the decorative properties by utilizing the metallic luster of the above, some kind of surface treatment is required.

The film obtained by the conventional chemical conversion treatment using chromic acid or dichromate or anodizing treatment is colored white to brown to black or green. In addition, it is possible to obtain corrosion resistance with a film obtained by anodizing treatment that does not use chromic acid or dichromate, but in order to obtain corrosion resistance, the film thickness must be several μm or more. It is inevitable that cloudiness will occur on the ground.

As a surface treatment method for maintaining the metallic luster of the surface of the magnesium material and imparting corrosion resistance, a method of applying an organic clear paint is generally used. However,
When an organic coating film is formed on the surface of magnesium material,
Inevitably, the metallic luster changes. In addition, when coating is performed after chemical conversion treatment, the chemical conversion treatment layer may be adversely affected by high temperature baking during coating.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the drawback of the anodized film obtained by the conventional surface treatment method, that is, it has a heat-resistant and transparent enamel-like barrier film and is made of a magnesium material. It is an object of the present invention to provide a method for forming an anodized film capable of forming a coating film that retains the luster of the substrate surface, has corrosion resistance, and that can be baked at high temperature even when coating and has excellent adhesion. I am trying.

Further, the present invention has a heat-resistant and transparent barrier film formed by forming an anodic oxide film on the surface of a magnesium material product by a specific anodic oxidation treatment method to obtain a glossy surface of a magnesium material substrate. It is an object of the present invention to provide a method for producing a magnesium material product that retains the above and has corrosion resistance.

[0010]

Means for Solving the Problems The present inventors have used an organic solvent-water-based electrolytic solution instead of a conventional water-based electrolytic solution to anodize a magnesium material to obtain a heat-resistant and transparent enamel-like material. It was found that an anodized film which is a barrier film of, which is corrosion resistant, can be baked at high temperature even when applied, and can form a film with excellent adhesion is obtained, and the present invention has been completed. did.

That is, the method for forming an anodized film of the present invention is an electrolytic solution containing a tertiary amine, water and an organic solvent, and optionally an additive such as an aluminate. It is characterized in that the surface of magnesium or a magnesium alloy (that is, magnesium material) is anodized in an electrolytic solution whose amount accounts for 5 to 50% by mass of the total electrolytic solution.

The method for producing a magnesium product or a magnesium alloy product of the present invention is characterized by forming an anodized film on the surface of a magnesium product or a magnesium alloy product by the above-mentioned method for forming an anodized film. It is a method for producing a magnesium product or a magnesium alloy product which has a transparent and transparent enamel-like barrier film, retains the luster of the surface of the metal substrate, and is corrosion resistant.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method for forming an anodized film of the present invention can form an anodized film on the surface of any magnesium material. As such a material, in terms of composition, for example, a Mg-Al alloy, a Mg-Zn alloy, a Mg-Mn alloy, a Mg-Zr alloy, and a Mg-Al alloy
-Zn alloy, Mg-Al-Mn alloy, Mg-Zn-
There are magnesium alloys such as Zr-based alloys, Mg-rare earth element-based alloys, Mg-Zn-rare earth element-based alloys, and magnesium metals, and AZ63, AZ91, and AZ are used for the purpose.
92, AM100, ZK51, EZ33, ZE41 and other magnesium alloys for casting, AZ31, AZ61, AZ
There are wrought magnesium alloys such as 80 and ZK60. Further, the anodic oxide film can be formed on the magnesium material having any surface condition. For example, the surface may be a die-cast surface, a plastic-processed surface, or a mirror-polished surface by polishing.

In the method for forming an anodized film of the present invention, generally, the pretreated magnesium material is anodized. This pretreatment can be performed, for example, on the surface of the die-cast as it is by various known treatment methods that have been conventionally performed prior to the anodizing treatment of the magnesium material. It can be carried out by salt treatment or caustic treatment. Further, when forming a surface having gloss, it is necessary to perform a pretreatment that does not dissolve the polished surface (does not lose gloss) after forming a mirror-finished surface by polishing. As such pretreatment, washing with a surfactant treatment, an alkali treatment, or a combination thereof is preferably performed.

Examples of the tertiary amine used in the method for forming an anodized film of the present invention include triethylamine, tripropylamine, tributylamine, triamylamine, trioctylamine and the like. Regarding the concentration of the tertiary amine in the electrolytic solution, some effect can be obtained at any concentration, but if the concentration of the tertiary amine is too low, the effect aimed at by the present invention tends to be insufficient, and
Even if the concentration of the tertiary amine increases, the effect corresponding to the increase cannot be obtained. Therefore, in the present invention, the concentration of the tertiary amine in the electrolytic solution is preferably about 0.05 to 2M.

The content of water in the electrolytic solution used in the method for forming an anodized film of the present invention has an important meaning. When the water content is less than 5% by mass, the anodized film obtained has a partially porous structure, and the appearance of the film tends to be whitish or yellowish and opaque. There is. When the content of water exceeds 50% by mass, dielectric breakdown occurs in the resulting anodized film structure, the appearance of the film becomes light gray, and a stable film cannot be formed. When the content of water is 5 to 50% by mass, preferably 10 to 40% by mass, the obtained anodic oxide film has a transparent enamel-like barrier film structure with corrosion resistance, and the luster of the surface of the base material of the magnesium material. Remains held.

As the organic solvent used in the method for forming an anodized film of the present invention, a solvent having an alcoholic hydroxyl group,
Among them, aliphatic alcohols are preferable, and specific examples thereof include methanol, ethanol, 1-propanol, 2-
Monohydric alcohols such as propanol, 1-butanol, 2-ethyl-1-hexanol, cyclohexanol; ethylene glycol, propylene glycol, butane-
Examples thereof include dihydric alcohols such as 1,4-diol and diethylene glycol; and polyhydric alcohols such as glycerin and pentaerythritol. Further, a solvent having a functional group other than the alcoholic hydroxyl group in the molecule, for example, 2-
It is also possible to use a solvent having an alkoxy group, such as methoxyethanol or diethylene glycol monoethyl ether.

Further, cyclic carboxylic acid esters such as γ-butyrolactone, γ-valerolactone and δ-valerolactone; chain carboxylic acid esters such as methyl acetate and methyl propionate; ethylene carbonate, propylene carbonate, butylene carbonate, Cyclic carbonic acid esters such as vinylene carbonate; dimethyl carbonate,
Chain carbonic acid esters such as ethylmethyl carbonate and diethyl carbonate; N-methylformamide, N-ethylformamide, N, N-dimethylformamide,
Amides such as N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile; It is also possible to use polar solvents such as phosphoric acid esters such as trimethyl phosphate and triethyl phosphate.

Further, a non-polar solvent such as hexane, toluene or silicone oil can be used. One of these solvents may be used alone, or two or more thereof may be used in combination. In the present invention, ethylene glycol alone, propylene glycol alone, or a mixed solvent thereof is particularly preferable.

In the method for forming an anodized film of the present invention, it is preferable that the electrolytic solution additionally contains aluminate and / or ammonium chlorofluoride. The aluminate has the effect of lowering the electrical resistance of the electrolytic solution and also achieves a remarkable effect on the smoothness of the anodized film obtained. Examples of the aluminate used in the method for forming an anodized film of the present invention include alkali metal salts, alkaline earth metal salts, ammonium salts and the like. Regarding the concentration of aluminate in the electrolytic solution, the above effect is insufficient if the concentration of aluminate is too low, and conversely, if the concentration of aluminate is too high, hydrolysis tends to cause precipitation. . Therefore, in the present invention, the concentration of aluminate in the electrolytic solution is preferably about 0.01 to 1.5M. Even when the electrolytic solution additionally contains ammonium fluoride, it has the effect of lowering the electric resistance of the electrolytic solution, but when ammonium fluoride has a high concentration, the corrosion resistance of the obtained anodic oxide film may be adversely affected. There is also.

Since the electrolytic solution used in the method for forming an anodized film of the present invention contains a tertiary amine, the pH of the electrolytic solution is
Is alkaline. Even if the electrolytic solution contains a tertiary amine, if the pH of the electrolytic solution is neutral to acidic due to the presence of an acid or the like, the effect intended by the present invention cannot be obtained.
Further, if the temperature of the electrolytic solution is too high, electrolysis tends to be unstable, and the obtained anodic oxide film tends to become cloudy. Therefore, the temperature of the electrolytic solution is preferably about room temperature to 50 ° C.

Regarding the power source for the anodizing treatment by the method for forming an anodized film of the present invention, there are direct current power source, alternating current power source,
Although any power source such as a PR power source and a pulse power source can be used, a DC power source or an AC power source is generally used. When the power source voltage is less than 10 V, it is difficult to form an anodic oxide film, and the direct current power source is 200
If it exceeds V or exceeds 150 V with an AC power source, electrolysis becomes unstable, and the transparency of the anodized film tends to decrease before it is obtained, which is not preferable. About 150V or less for DC power supply, 1 for AC power supply
It is preferably about 00 V or less.

The anodic oxide film obtained by the conventional technique needs to have a film thickness of 1 μm to several tens of μm in order to obtain desired corrosion resistance, so that the anodic oxide film is a film colored from white to brown to black or green. Met. On the other hand, since the anodic oxide film obtained by the forming method of the present invention is extremely smooth and dense, it has good corrosion resistance even if it is extremely thin. Sufficient corrosion resistance is exhibited even if the thickness can be retained, preferably 0.1 μm or less. That is, it is possible to obtain a surface having excellent corrosion resistance while hardly changing the gloss of the surface of the magnesium material substrate.

Although the method for forming the anodic oxide film has been described above, from another point of view, the present invention provides an anodic oxide film on the surface of a magnesium product or a magnesium alloy product by the above method for forming an anodic oxide film. It can be seen as a method for producing a magnesium product or a magnesium alloy product that has a heat-resistant and transparent enamel-like barrier film that retains the luster of the surface of the metal substrate and is corrosion resistant, which is characterized by being formed. it can. Specific examples of such magnesium products or magnesium alloy products include cases of MD recording / reproducing devices known as MD Walkman (registered trademark), digital video cameras, bags, bags, suitcases, automobiles, and motorcycles. There are welfare equipment such as exterior parts, wheelchairs and canes.

The anodic oxide film obtained by the forming method of the present invention is a film excellent in corrosion resistance with hardly changing the gloss of the surface of the magnesium material base as described above. In order to further increase the corrosion resistance even with a slight sacrifice, it is possible to use the method for forming an anodized film of the present invention as a base treatment and perform clear coating on the anodized film.
For example, when applying a clear acrylic lacquer coating, the adhesion of the coating film is improved by coating on the anodized film obtained by the forming method of the present invention, rather than directly coating on the surface of the magnesium material, Corrosion resistance is also improved. Since the film obtained by the method for forming an anodized film of the present invention is heat resistant, it is possible to perform coating requiring high temperature baking.

[0026]

EXAMPLES The present invention will be specifically described below based on examples. Example As a magnesium material, a magnesium rolled plate of 99.95 mass% Mg (50 mm × 50 mm × 3 mm), 9
Magnesium rolled plate of 9.6 mass% Mg (50 mm × 5
0mm x 3mm), rolled plate of AZ31B (50mm x 5)
0mm x 3mm) or AZ91D die-cast plate (5
(0 mm × 50 mm × 3 mm), their surfaces were degreased with alkali, and then acid washed with sulfuric acid.

On the other hand, the main solvent is ethylene glycol, the concentration of triethylamine is 0.5M or 1M, the content of water is 10, 20, 30 or 40% by mass, and sodium aluminate is contained (concentration Various electrolytes were prepared with or without 0.1 M or 1 M) and with or without ammonium fluoride (concentration 0.1 M or 1 M). While maintaining the temperature of the electrolytic solution at 25 ° C., each of the magnesium material plates washed as described above was dipped therein and subjected to direct current electrolysis at an electrolysis voltage of 60 V for 4 minutes to form an anodized film. , Then dried.

Each magnesium material plate anodized as described above and each corresponding magnesium material plate only subjected to degreasing and acid cleaning were visually compared for their metallic luster and color tone. did. When an electrolytic solution having a water content of 10% by mass and containing no sodium aluminate was used, the metallic luster and color tone of the surface of each of the magnesium materials slightly decreased. However, in other cases, there was almost no difference. That is, each anodic oxide film was excellent in transparency.

When the film thickness of the anodized film on the magnesium material plate anodized as described above was measured by ellipsometry, all were 0.5 μm or less. Table 1 shows the magnesium materials shown in Table 1 to Table 2.
Regarding the corrosion resistance of each magnesium material plate having an anodized film obtained by anodizing treatment in an electrolytic solution having a composition shown in Table 2, Table 1 to Table 1 according to JIS Z2371.
The salt spray test was conducted at the times shown in Table 2 and evaluated by the rating number method. The results are shown in Table 1 ~
It was as shown in Table 2.

Further, each magnesium material plate having an anodic oxide film obtained by anodizing the magnesium materials shown in Tables 3 to 4 in an electrolytic solution having a composition shown in Tables 3 to 4 Regarding the corrosion resistance of the product heat-treated at 200 ° C. for 1 hour, according to JIS Z 2371, Tables 3 to 4
The salt spray test was conducted at the times shown in the table and evaluated by the rating number method. The results are shown in Tables 3 to 4.
It was as shown in the table.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

As is clear from the rating numbers shown in Tables 1 to 4, the magnesium products and magnesium alloy products treated by the method for forming an anodized film of the present invention have excellent corrosion resistance, and As is clear from the comparison between the rating numbers shown in the table and the rating numbers shown in Table 3 and the comparison between the rating numbers shown in Table 2 and the rating numbers shown in Table 4, formation of the anodized film of the present invention The anodized film obtained by the method also has excellent heat resistance.

[0036]

The anodic oxide film obtained by the method for forming an anodic oxide film of the present invention is dense, so that even if it is extremely thin, it has good corrosion resistance, and even if it has a thickness that does not change the gloss of the metal base, it is sufficient. Shows excellent corrosion resistance. That is, it is possible to obtain a surface having excellent corrosion resistance while hardly changing the gloss of the surface of the magnesium material substrate.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ikuhiro Sakai             1-24-2 Nishishinjuku, Shinjuku-ku, Tokyo Kogakuin University             Faculty of Engineering, Department of Applied Chemistry, Laboratory of Inorganic Materials Chemistry (72) Inventor Makoto Dobashi             1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting             Research Institute, Inc. (72) Inventor Masahiro Hyakutake             1333-2 Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting             Research Institute, Inc.

Claims (6)

[Claims] 1. An electrolytic solution containing a tertiary amine, water and an organic solvent, wherein the content of water is 5 to 50% by mass of the total electrolytic solution.
A method for forming an anodic oxide coating, characterized in that the surface of magnesium or a magnesium alloy is subjected to anodizing treatment in an electrolyte solution that occupies the same. 2. The content of water is 10 to 40% by mass of the total electrolytic solution.
The method for forming an anodized film according to claim 1, wherein an electrolytic solution occupying the same is used. 3. The method for forming an anodized film according to claim 1, wherein an electrolytic solution having a tertiary amine concentration of 0.05 to 2 M is used. 4. An organic solvent, such as ethylene glycol, propylene glycol, butane-1,4-diol, diethylene glycol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-ethyl-1-hexanol, cyclo. The method for forming an anodized film according to claim 1, 2 or 3, wherein an electrolytic solution containing an aliphatic alcohol selected from hexanol, glycerin and pentaerythritol is used. 5. The method for forming an anodized film according to claim 1, wherein an electrolytic solution additionally containing an aluminate at a concentration of 0.01 to 1.5 M is used. 6. A heat-resistant and transparent enamel-like barrier film, characterized in that an anodized film is formed on the surface of a magnesium product or a magnesium alloy product by the method according to any one of claims 1 to 5. A method for producing a magnesium product or a magnesium alloy product, which has corrosion resistance and retains the luster of the surface of a metal substrate.