JPH11236698A - Corrosion-resistant magnesium material product exhibiting luster of metal substrate and method for producing the same - Google Patents

Abstract

(57) Abstract: A magnesium material product exhibiting the luster and color tone of a metal base of a magnesium material, or exhibiting the luster of a metal base with slightly changing color tone of the metal base, and having corrosion resistance; and To provide a manufacturing method thereof. The metal material has an anodized film on the outer surface thereof which does not change the luster of the metal substrate, and has a colorless or colored transparent electrodeposition coating film on the anodized film to exhibit the luster of the metal substrate. A corrosion-resistant magnesium material product, and a magnesium material product immersed in an electrolyte containing phosphate and aluminate, anodizing the surface to form an anodized film, and then colorless by electrodeposition coating Alternatively, a method for producing a corrosion-resistant magnesium material product exhibiting a luster of a metal substrate, forming a colored transparent electrodeposition coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant magnesium material product exhibiting the luster of a metal base made of magnesium or a magnesium alloy (in this specification, both are described as a magnesium material) and a method for producing the same. Specifically, a corrosion-resistant magnesium material product having an anodized film on the outer surface of a magnesium material product, having a colorless or colored transparent electrodeposition coating film thereon, and exhibiting the luster of a metal substrate, and a novel composition Anodizing treatment using an electrolytic solution to form an anodized film, and then form a colorless or colored transparent electrodeposition coating film by electrodeposition coating. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Magnesium material is the lightest and has the highest specific strength among practical metals, and its properties are used to store interior and exterior parts of automobiles and motorcycles, parts of home appliances, bags, suitcases, and the like. Applications to containers, sports equipment, parts of optical equipment, canes, and new fields of the electronics industry such as computers and sound have been tried and put to practical use. However, since the magnesium material is the most active metal material among practical metals, it has been difficult to use the magnesium material as it is in terms of corrosion resistance.

[0003] As a surface treatment method for improving the corrosion resistance of a magnesium material, conventionally, a chemical conversion treatment, an anodization treatment,
Painting, plating, etc. have been implemented. In particular, when a film is formed by anodic oxidation treatment and then sealing treatment is performed, a relatively uniform film is formed, so that it is used as a rust preventive treatment or a base treatment for coating.

[0004]

When a product made of a magnesium material is provided with decorative properties utilizing the luster and color tone of the metal base, the surface cannot be painted. However, since the surface of the magnesium material is easily oxidized, some surface treatment is required to maintain the initial gloss and color tone of the metal substrate.

[0005] A film obtained by a conventional chemical conversion treatment or anodization treatment using chromic acid or dichromate is colored white to brown to black or green. In addition, corrosion resistance can be obtained even with a film obtained by anodic oxidation treatment using neither chromic acid nor dichromate, but in order to achieve the required corrosion resistance, the film thickness becomes several μm or more. It is inevitable that the surface after the oxidation treatment becomes clouded or colored.

[0006] For example, Japanese Patent Application Laid-Open No. 9-176894 discloses an electrolytic solution prepared by adding a film-forming stabilizer to an aqueous solution containing at least one hydroxide, carbonate or bicarbonate of an alkali metal or alkaline earth metal. A surface treatment method for forming an anodic oxide film using a liquid is described. In this surface treatment method, it is described that the color tone of the anodic oxide film may be a base color. However, in the anodic oxide film forming method described in the publication, when a film having a required corrosion resistance is formed, the film is colored.

[0007] As a surface treatment method for maintaining the luster and color tone of a metal base made of a magnesium material, a method of electrodeposition coating an organic clear paint is also known. However, the change in gloss and color tone of the metal substrate due to the formation of the organic coating film is inevitable, and often causes fogging.

The present invention has solved the drawbacks of the conventional anodic oxide coating and the clear coating film, that is, the present invention shows the luster and color tone of the magnesium base metal, or the color tone of the metal base slightly changes. However, it is an object of the present invention to provide a magnesium material product exhibiting the luster of a metal base and having corrosion resistance.

The present invention also relates to a corrosion-resistant magnesium material having a metallic base by forming an anodized film on the surface of a magnesium material product and forming a colorless or colored transparent electrodeposition coating film thereon. It is an object to provide a method for manufacturing a product.

[0010]

Means for Solving the Problems The inventors of the present invention have developed a magnesium material product by using an electrolyte in which a phosphate added as a film-forming stabilizer when anodizing a metal is used in combination with an aluminate. By anodizing, it is possible to obtain a thin and unprecedented colorless and transparent anodic oxide film with high corrosion resistance, and by forming a colorless or colored transparent electrodeposition coating film on this anodic oxide film. The present inventors have found that a magnesium material product having further excellent corrosion resistance can be obtained and completed the present invention.

That is, the corrosion-resistant magnesium material product of the present invention exhibiting a metallic base luster has an anodic oxide film on the outer surface of the magnesium material product which does not change the luster of the metal substrate, and is colorless or colored on the anodic oxide film. It is characterized by having a transparent electrodeposition coating film.

Further, the method of the present invention for producing a corrosion-resistant magnesium material product exhibiting the luster of a metal substrate further comprises a bath stabilizer containing a phosphate and an aluminate and, if desired, an organic compound having a hydroxyl group. The magnesium material product is immersed in the electrolyte solution to be anodized, and the surface is anodized to form an anodic oxide film. A colorless or colored transparent electrodeposition coating film is formed by painting.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The magnesium material product of the present invention may be made of any magnesium material. Such materials include, for example, Mg-Al alloys, Mg-Al-Zn alloys, Mg-Al-Mn alloys, Mg-Zn-Zr alloys, Mg-rare earth element alloys, Mg-Zn- There are magnesium alloys such as rare earth element alloys and magnesium metal. Further, in the present invention, the surface state of the magnesium material product before the anodizing treatment may be in any state, for example, it may be a mirror-finished surface by polishing or a surface as it is die-cast.

When forming an anodized film on a magnesium material product according to the present invention, the pretreated magnesium material product is anodized. This pretreatment can be performed on the surface of the die-cast as it is by various known treatment methods conventionally performed prior to the anodic oxidation treatment of the magnesium material, for example, pyrophosphate treatment, caustic alkali treatment. It can be implemented in processing. In addition, when a surface having a mirror gloss is formed, it is necessary to form a mirror-finished surface by polishing, and then perform a pretreatment that does not dissolve the gloss surface (does not lose gloss). As such a pretreatment, it is preferable to carry out a cleaning by a surfactant treatment, an alkali treatment, or a combination thereof.

In the present invention, the phosphate used for forming the anodic oxide film includes an alkali metal salt of phosphoric acid,
Examples thereof include alkaline earth metal salts and ammonium salts. These phosphates may be added to the electrolyte as phosphates, or phosphoric acid and an alkali metal hydroxide, an alkaline earth metal salt, ammonium hydroxide, or the like may be added to the electrolyte to form an electrolyte. Phosphates may be formed in the solution.

Regarding the concentration of phosphate in the electrolytic solution, if the phosphate concentration is too low, the electrolysis tends to be unstable and the resulting anodic oxide film tends to be clouded, that is, the anodic oxidation The formation of the film tends to be unstable, and if the phosphate concentration is too high, it tends to be difficult to obtain an anodic oxide film having desired characteristics. Therefore, in the present invention, the concentration of the phosphate in the electrolyte is preferably 0.05%.
０．２0.2M.

In the present invention, examples of the aluminate used for forming the anodic oxide film include alkali metal salts, alkaline earth metal salts, and ammonium salts. Regarding the concentration of aluminate in the electrolyte, if the aluminate concentration is too low, the electrolysis tends to be unstable, and the corrosion resistance of the resulting anodic oxide film tends to be insufficient. If the salt concentration is too high, hydrolysis tends to occur and precipitation tends to occur. Therefore, in the present invention, the concentration of the aluminate in the electrolytic solution is preferably 0.2 to 1M.

In the present invention, the bath stabilizer optionally used when forming the anodic oxide film is an organic compound having a hydroxyl group which is known to inhibit the hydrolysis of aluminate, such as glycerin and diethylene glycol. Is preferably used. When a bath stabilizer is used, the concentration of the bath stabilizer in the electrolytic solution is from 1 to 2
0 g / l and based on the weight of aluminate
Preferably it is 50% by weight. The concentration of the bath stabilizer is 1
When the amount is less than 10 g / l or less than 10% by weight based on the weight of the aluminate, the effect of adding the bath stabilizer tends to be insufficient, and the concentration of the bath stabilizer tends to be insufficient. 2
If it exceeds 0 g / l or exceeds 50% by weight based on the weight of the aluminate, the resulting anodic oxide film tends to have a bad influence on the corrosion resistance.

In the present invention, if the pH of the electrolytic solution used for forming the anodic oxide film is less than 12, stable electrolysis tends to be difficult.
It is preferably two or more. Since the pH changes depending on the concentrations of the phosphate and the aluminate, it is preferable to add an alkali substance to the electrolyte as needed to adjust the pH of the electrolyte to 12 or more. On the other hand, if the temperature of the electrolytic solution is too high, the electrolysis tends to be unstable or the resulting anodic oxide film tends to be fogged. Therefore, the temperature of the electrolytic solution is preferably from room temperature to 50 ° C.

In the present invention, any power source such as a DC power source, an AC power source, a PR power source and a pulse power source can be used for forming the anodic oxide film. Use power supply. Regarding those power supply voltages, it is difficult to form an anodic oxide film when the power supply voltage is less than 30 V, and the electrolysis tends to be unstable when the DC power supply exceeds 100 V and the AC power supply exceeds 70 V. Yes, not preferred. The voltage is preferably 90 V or less for a DC power supply, and 65 V or less for an AC power supply.

The coating obtained by the anodic oxidation treatment has a large number of pores. In order to further enhance the corrosion resistance of the anodic oxidation coating, it is preferable to seal these pores. In the present invention, after the anodic oxidation treatment, if desired, it can be immersed in hot water to perform the sealing treatment according to a known treatment method. The hot water is preferably pure water of 85 ° C. or higher, and the treatment time is preferably about 3 to 15 minutes.

With respect to the anodic oxide film obtained by the conventional technique, the film thickness is set to 1 μm to several tens μm in order to obtain a desired corrosion resistance.
m, so that the anodized film was a film colored white to brown to black or green. On the contrary,
Since the anodic oxide film obtained by the above-described method for forming an anodic oxide film is dense, it has good corrosion resistance even if it is extremely thin, for example, even if it has a thickness that does not change the luster and color tone of the metal substrate, it is preferably Even with a thickness of 0.1 μm or less, sufficient corrosion resistance is exhibited. That is, a surface having excellent corrosion resistance can be obtained without substantially changing the gloss and color tone of the surface of the magnesium material.

In the present invention, by forming a colorless and transparent electrodeposition coating film on the above-described anodized film, the luster and color tone of the metal substrate are exhibited, or by forming a colored transparent electrodeposition coating film. Although the color tone of the metal substrate slightly changes, a magnesium material product exhibiting the luster of the metal substrate and having more excellent corrosion resistance can be obtained.

The above-mentioned electrodeposition coating film can be formed by a well-known anion electrodeposition coating method or cationic electrodeposition coating method. When performing such an electrodeposition coating method, the type of the electrodeposition coating tank, the type of the electrodeposition coating, the concentration of the electrodeposition coating liquid,
The temperature, pH, electrodeposition coating voltage, electrodeposition coating time, and the like are known, and in the present invention, such known techniques can be used as they are. For example, there are acrylic, modified maleated oil, modified alkyd, polybutadiene and the like as anionic electrodeposition paints, and epoxy and the like as cationic electrodeposition paints.

The pigment used for forming a colored transparent electrodeposition coating film is an organic pigment which is ionized in water and has a good affinity for the resin component since it is necessary to electrodeposit evenly with the resin component. For example, it is preferable to use azo, phthalocyanine, metal complex, triphenylmethane, quinacridone, perylene, isoindolinone, dioxazine, quinophthalone, vat dye, condensed azo, and the like. These organic pigments are preferably used in the electrodeposition coating solution at a concentration of 0.1 to 15 g / l.

The individual components of the method for producing a corrosion-resistant magnesium material product exhibiting the luster of a metal substrate have been described above. By such a production method, the corrosion-resistant magnesium material product exhibiting the luster of the metal substrate of the present invention can be obtained. When forming a colorless and transparent electrodeposition coating film on the anodic oxide film, the corrosion-resistant magnesium material product of the present invention exhibits the luster and color tone of the metal substrate with little change in the gloss and color tone of the magnesium material substrate, or is colored. When a transparent electrodeposition coating film is formed as described above, the color tone of the magnesium material base slightly changes, but the gloss of the magnesium material base is exhibited. In addition, the corrosion-resistant magnesium material product of the present invention is remarkably superior in terms of corrosion resistance as compared with those directly coated by electrodeposition without performing anodizing treatment, and also in terms of the gloss and color tone of the metal substrate presented. It was excellent.

Specific examples of such magnesium material products include MD recording / reproducing devices known as MD Walkman (registered trademark), cases of digital video cameras, bags, suitcases, automobiles, and motorcycles. There are welfare-related tools such as exterior parts, wheelchairs and canes.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. Example 1 AZ91D die-cast plate (50 mm × 50 mm × 3 m
m) was mirror-finished by mechanical polishing, and the mirror-finished surface was washed with a surfactant and then washed with water. On the other hand, trisodium phosphate dodecahydrate concentration 25 g /
1, a sodium aluminate concentration of 25 g / l, a glycerin concentration of 10 g / l, and a pH of 13.0 were prepared. While the temperature of the electrolyte was maintained at 30 ° C., the above-mentioned washed die-casting plate was immersed. DC electrolysis was performed at a voltage of 65 V for 30 seconds. After rinsing with water, it was further immersed in pure water at 90 ° C. for 5 minutes to perform a sealing treatment, and then dried.
The thickness of the anodized film on the die-cast plate subjected to the anodic oxidation treatment and the sealing treatment was measured by ellipsometry to be 60 nm.

The anodized die-cast plate was electrodeposited under the following electrodeposition conditions. Acrylic anion electrodeposition paint used: Elecoat A
M [trade name of Shimizu Corporation] in half with ion-exchanged water
PH of electrodeposition coating solution: 8.0, bath temperature of electrodeposition coating solution: 25 ° C, electrodeposition coating voltage: 50 V, electrodeposition coating time: 30 seconds, cathode material: SUS304 stainless steel, cathode Bag: cotton flannel, pole ratio: anode / cathode = 1/1, gap: 15 cm, stirring: circulation and stirring by pump.

The die-cast plate coated by electrodeposition under the above-mentioned electrodeposition conditions is washed with water, preliminarily dried at 80 ° C. in an air atmosphere for 10 minutes in a drier, and then dried at 150 ° C. in an air atmosphere in a firing furnace.
For 30 minutes. A die-cast plate that has been subjected to only mirror finishing and cleaning as described above, and further subjected to anodizing treatment as described above, and a die-cast plate that has been subjected to sealing treatment but has not been subjected to electrodeposition coating, as described above. Anodized, sealed, and electrodeposited die-cast plates were compared with the naked eye for gloss and color tone of their surfaces, but found little difference.

The corrosion resistance of the die-cast plate having the above-mentioned anodic oxide film but not electrodeposited was tested by repeating the salt spraying for 8 hours to 16 hours for 2 cycles and evaluated by the rating number method. .
It was 0. On the other hand, the anodizing treatment was performed, the sealing treatment was performed, and the corrosion resistance of the electrodeposited die-casting plate was tested by repeating salt water spraying for 8 hours to 16 hours for 2 cycles and evaluated by the rating number method. , RN = 10.0.

Example 2 The procedure of Example 1 was repeated, except that a pink Elecoat Color (trade name, manufactured by Shimizu Co., Ltd.) was used as the acrylic anion electrodeposition paint. Measured and evaluated. A mirror-finished and cleaned die-cast plate, and further anodized as described above,
The gloss and color of the surface of the die-cast plate that has been subjected to the sealing treatment but not subjected to the electrodeposition coating, and the die-cast plate that has been subjected to the anodic oxidation treatment as described above, has been subjected to the sealing treatment and has been subjected to the electrodeposition coating, and Were compared with the naked eye, and almost no difference was observed in gloss. However, regarding the color tone, the appearance of the electrodeposition-coated die-cast plate was slightly pinkish.

The corrosion resistance of a die cast plate having an anodized film but not electrodeposited was measured by spraying with salt water for 8 hours-1.
The test was repeated for two cycles of standing for 6 hours and evaluated by the rating number method. As a result, RN = 9.0. On the other hand, anodizing treatment, sealing treatment,
The corrosion resistance of the electrodeposited die-cast plate was tested by repeating two cycles of salt spraying for 8 hours to 16 hours,
When evaluated by the rating number method, RN =
10.0.

Comparative Example 1 AZ91D die-cast plate (50 mm × 50 mm × 3 m
m) was mirror-finished by mechanical polishing, and the mirror-finished surface was washed with a surfactant and then washed with water. The die-cast plate treated in this manner was electrodeposited under the same electrodeposition conditions as in Example 1, washed with water, pre-dried in a dryer at 80 ° C. for 10 minutes in air atmosphere, and then in a firing furnace in air atmosphere. It baked at 150 degreeC for 30 minutes.

The gloss and color tone of the surface of the die-cast plate obtained in this way were more cloudy than the gloss and color tone of the surface of the die-cast plate obtained in Example 1. Further, the corrosion resistance of the die-cast plate obtained as described above was tested by repeating the salt water spraying for 8 hours to 16 hours for 2 cycles. As a result, it was found that the die-cast plate corroded and was inferior in corrosion resistance.

[0036]

Industrial Applicability The magnesium material product of the present invention exhibits the luster of a metal substrate with almost no change in the gloss and color tone or luster of the magnesium material substrate, and is extremely excellent in corrosion resistance.

Claims (8)

[Claims] 1. A magnesium or magnesium alloy product having an anodic oxide film on the outer surface thereof which does not change the luster of a metal substrate, and a colorless or colored transparent electrodeposition coating film on the anodic oxide film. Corrosion-resistant magnesium material product that exhibits the luster of a metallic substrate. 2. An anodic oxide film obtained by immersing magnesium or a magnesium alloy in an electrolyte containing phosphate and aluminate and subjecting the surface to anodizing treatment. Claim 1.
A corrosion resistant magnesium material product exhibiting the luster of the described metal substrate. 3. An anodic oxide coating comprising a phosphate, an aluminate,
And an anodic oxide film obtained by immersing magnesium or a magnesium alloy in an electrolytic solution containing a bath stabilizer comprising an organic compound having a hydroxyl group and anodizing the surface thereof. Item 10. A corrosion-resistant magnesium material product exhibiting luster of a metal substrate according to Item 1. 4. A magnesium or magnesium alloy product is immersed in an electrolytic solution containing a phosphate and an aluminate, the surface of which is anodized to form an anodized film. A method for producing a corrosion-resistant magnesium material product exhibiting luster of a metal substrate, wherein a colorless or colored transparent electrodeposition coating film is formed. 5. The metallic substrate according to claim 4, wherein the concentration of the phosphate is 0.05 to 0.2M and the concentration of the aluminate is 0.2 to 1M. Manufacturing method of corrosion resistant magnesium material products. 6. A magnesium or magnesium alloy product is immersed in an electrolytic solution containing a bath stabilizer comprising an organic compound having a phosphate group, an aluminate group and a hydroxyl group, and the surface thereof is anodized. And forming a colorless or colored transparent electrodeposition coating film thereon by electrodeposition coating. A method for producing a corrosion-resistant magnesium material product exhibiting the luster of a metal substrate. 7. The concentration of the phosphate is 0.05 to 0.2 M, the concentration of the aluminate is 0.2 to 1 M, the concentration of the bath stabilizer is 1 to 20 g / l, and the concentration of the aluminate is The method according to claim 6, wherein the content is 10 to 50% by weight based on the weight of the salt. 8. The metal substrate according to claim 4, wherein the anodizing treatment is followed by immersion in hot water to perform a sealing treatment, and thereafter, an electrodeposition coating. A method for producing a glossy corrosion-resistant magnesium material product.