JPS6270600A - Molding of magnesium or alloy thereof having colored film and its production - Google Patents

Abstract

PURPOSE:To produce a molding made of an Mg metal having excellent corrosion resistance and ornamentality and metallic gloss by anodizing the molding of Mg or Mg alloy to form a film having excellent corrosion resistance and light transmittability thereon, then coloring the film with a dye for coloring alumite. CONSTITUTION:The molding of the Mg or Mg alloy is anodized to form the light transmittable anodized film contg. >=1 kinds of compds. selected from MgO, MgO.Al2O3, MgO.SiO2, Mg(OH)2 and MgF2 on the surface thereof. The film is formed to at least >=0.2mum thickness in order to maintain the corrosion resistance and to <=2mum, more particularly <=1.6mum to avoid losing the light transmittability. The molding is them immersed in a coloring bath contg. >=1 kinds of dyes selected from an acidic dye, alloy metallic complex salt dye or acidic mordant dye to color the anodized film. The molding of the Mg or Mg alloy having the surface which excels in the metallic gloss, corrosion resistance and ornamentality is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a molded body of magnesium or its alloy having a colored film on its surface, and a method for producing the same. More specifically, the present invention provides magnesium or an alloy thereof (hereinafter sometimes referred to as Mg or Mg alloy) that has a highly corrosion-resistant colored anodic oxide film on its surface and exhibits metallic luster.
The present invention relates to a molded article and a method for producing the same.

[Background of the Invention] Mg molded bodies and Mg alloy molded bodies are used in various products, especially as lightweight structural materials, but they are usually subjected to various surface treatments to compensate for the drawback that Mg is easily corroded. has been done. Among the various surface treatment methods known so far, the following methods are known to improve decorativeness as well as corrosion resistance (for example, actively coloring the surface). There is a way.

For example, a method is known in which a surface treatment (chemical conversion treatment, anodic oxidation treatment, etc.) is performed and then painting is applied to improve decorativeness. This method makes it possible to obtain any colored surface by changing the type of paint. However, since the surface becomes a paint film, the metallic texture of the underlying magnesium or magnesium alloy is lost, which is undesirable.Also, metal powder is blended into this paint to give the paint film a metallic look. It is also possible, but
Even in this case, the appearance still has the feel of a paint film, which is not desirable.

There is also a method of using plating to give a metallic feel to the surface of the molded body. However, with this method, it is necessary to replace the surface of Mg or Mg alloy with zinc before plating (chromium plating, nickel plating, etc.) on the target metal molded body, which makes the process complicated and economical. This is disadvantageous. Furthermore, there are also problems such as difficulty in obtaining a desired color tone by plating.

Furthermore, the Dow 21 method (ferric nitrate treatment) is also known. The treated surface obtained by this method forms a satin finish and exhibits a silvery white luster, so it has the advantage of being beautiful. However, in this case, since the corrosion resistance is poor, it is necessary to apply a clear coat, but there are problems such as poor adhesion of the paint.

JP-A-55-76094 discloses that after a molded body of Mg or Mg alloy is anodized using a phosphate-based treatment liquid, the surface of this body is treated with an aluminum dye (alumite coloring dye). There is a description that it can be colored golden yellow. However, in this case, it is stated that it is necessary to decolorize the dye adhering to the surface after the coloring treatment, which is not only difficult to adhere to, but also makes the treatment process complicated and economically disadvantageous. There's a problem.

JP-A-55-16997 states that when a Mg or Mg alloy molded body is anodized in a treatment solution containing a coloring component, a colored oxide film is generated accompanied by spark discharge. has a smooth, glass-like colored surface that has lost its metallic luster, making it undesirable from a decorative point of view.

JP-A-60-39198 discloses that anodic oxidation is performed in an alkaline processing solution to form an oxide film, and then this oxide film is colored using an alumite coloring dye to obtain various hues. It is stated that. However, what is specifically described there is a white oxide film, which is opaque. Therefore, even if an excellent hue can be obtained by coloring a white oxide film, it is difficult to obtain metallic luster because the film prevents light from passing through to the inner metal surface.

As a result, there has been no known method for producing a colored film with good corrosion resistance that exhibits metallic luster on a molded body formed on Mg or an Mg alloy.

[Object of the Invention] The main object of the present invention is to provide a molded body of magnesium or its alloy that is excellent in both corrosion resistance and decorativeness, and a method for producing the same.

In particular, it is an object of the present invention to provide a molded body of magnesium or its alloy that has a highly corrosion-resistant colored anodic oxide film on its surface and exhibits excellent metallic luster, and a method for producing the same.

[Summary of the Invention] The present invention comprises a molded body of magnesium or an alloy thereof, which is characterized by having a colored anodic oxide film exhibiting translucency on its surface.

The thickness of the above-mentioned transparent colored anodic oxide film is preferably 24 m or less, particularly preferably 1.6 μm or less, and preferably 0.27 mm or more. Better λ.

The molded body of magnesium or its alloy having a colored anodic oxide film exhibiting translucency on its surface can be obtained by anodizing the molded body of magnesium or its alloy to form a translucent anodized film (preferably , a film having a thickness of 2 pm or less) and then coloring this anodic oxide film using an alumite coloring dye.

[Detailed Description of the Invention] The molded body of magnesium or its alloy having a transparent colored anodic oxide film on its surface according to the present invention can be advantageously produced by the method described below.

First of all, a first step is performed in which a molded body of Mg or Mg alloy is anodized to form a translucent anodic oxide film having a thickness of preferably 2 Bm or less. The film thickness is particularly preferably 1.6 μm or less in order to further improve translucency, and from the viewpoint of corrosion resistance, it is preferably 0.2 μm or more.

The above-mentioned anodic oxidation treatment can be carried out, for example, by
The treatment can be carried out using a treatment bath as described in Japanese Patent No. 39198 and according to known treatment methods such as treatment using alternating current, direct current, or alternating current and superimposed alternating current. However, in order to obtain an oxide film having the translucency required in the present invention, it is necessary to change the processing conditions, such as shortening the processing time.

The composition of the oxide film obtained by anodic oxidation varies depending on the type of treatment solution, but powder X-ray diffraction results show that it is empty and this *
and MgO, MgO-An 203 .

Compounds such as MgO@5i02, Mg(OH)2, MgF2, and glassy (amorphous) versions thereof have been identified.

The anodic oxide film in the present invention is preferably made of a product containing an aluminum component, considering the stainability of the dye when coloring with the following alumite coloring dye. Therefore, it is preferable that the anodizing treatment operation be carried out using a treatment bath containing an aluminum component.

Next, a second step is carried out in which the light-transmitting anodic oxide film is colored with a dye for coloring alumite (acidic dyes, acidic alloy metal complex dyes, acidic mordant dyes, etc. are preferable).

A method of coloring an anodic oxide film formed on the surface of a molded body of magnesium, its alloy, etc. with a dye for coloring alumite is also described in the above-mentioned Japanese Patent Application Laid-Open No. 60-39198, and is well known. For example, the anodic oxide film can be colored by immersing the above-mentioned translucent anodic oxide film in a coloring bath containing a dye for coloring alumite.

For information on how to color oxide films, please refer to the Metal Surface Technology Association line "
It is also described in "Metal Surface Technology Handbook" page 581 (published in Nikkan Kogyo Shimbun in 1976).

In addition, in order to further increase the corrosion resistance of the colored surface and to make the gloss more noticeable and improve its decorative properties, the colored film with metallic luster may be coated with a clear coating or the pores may be sealed with water glass. This is an effective method.

[Effects of the Invention] The colored oxide film formed on the surface of the magnesium or magnesium alloy molded product of the present invention not only has excellent corrosion resistance but also has translucency, so that the surface of the magnesium or magnesium alloy inside the film is transparent. The metallic luster is clearly observed from the outside, and therefore a beautiful metallic luster appears on the colored surface. Therefore, the magnesium or magnesium alloy molded body of the present invention can be widely used as a lightweight product that is not only durable but also has excellent decorative properties, for example, as a lightweight structural material.

Next, in Examples and Comparative Examples of the present invention, the presence or absence of metallic luster on the treated surface was determined visually. Corrosion resistance is determined according to JIS-Z-2371 [salt spray test method]
The weight change before and after the test was determined and expressed as corrosion weight loss (Cg/rn').

[Example 1] Degreasing φ of magnesium alloy plate (AZ31 equivalent product)
After pickling, KOH: 100g/! Q, Anodic oxidation treatment was performed at 55 V AC for 10 minutes using a treatment solution consisting of 30 g/liter of A (OH) 3, 25 g/liter of KF, and 20 g/L of (COOK) 2. . The obtained oxide film has a film thickness of 0.5 to 0.
．． 8pm, and the generated components are MgO and MgO・A. It was confirmed that it was Oko.

Next, the above oxide film was coated with Aluminum Ora G, a dye for alumite coloring.
ngeG, manufactured by Sandoz) + 0.5 g/m at 80°C
It was immersed in a coloring bath for 10 minutes for coloring treatment.

The surface of the obtained magnesium alloy plate had a slightly brownish golden color and had a beautiful metallic luster.

The results of the corrosion resistance test are shown in Table 1.

[Example 2] When a clear lacquer paint was sprayed on the surface of the colored film of the magnesium alloy plate with the colored film obtained in Example 1 (coating film thickness = 15 to 20 JLm), the surface was as shown in Example 1.
It was almost as beautiful as it was.

The results of the corrosion resistance test and the gridlock test are shown in Table 1.

[Example 3] An anodized product with a film thickness of 0.8 to 1.2 pm, obtained in the same manner as in Example 1 except that the anodization treatment time was 20 minutes, was coated with an alumite coloring dye sand.・Blue G
(Sanodal Blue G, manufactured by Sandoz): 2
It was colored by immersing it in a coloring bath at a concentration of g/u at 60° C. for 10 minutes.

The obtained magnesium alloy plate had a beautiful blue color with a metallic luster on its surface.

The corrosion resistance test results are shown in Table 1.

[Example 4] Degreasing and degreasing of a magnesium alloy plate (AZ31 equivalent)
After pickling, anodizing was performed using an anodizing solution containing 40 g of NaOH at AC 40 V for 20 minutes to form a MgO film with a thickness of 0.8 to 1.5.
An oxide film having a light transmittance of 1.0 m was obtained.

Next, the above oxide film was coated with aluminum green RL W (Alu+siniumG), a dye for alumite coloring.
reen RLW (manufactured by Sandoz Co.): Coloring treatment was performed by immersing the sample in a coloring bath at 0° C. at a concentration of 1 g/Jl for 10 minutes.

By the above operation, a beautiful green colored product with metallic luster was obtained.

The corrosion resistance test results are shown in Table 1.

[Example 5] Magnesium die-casting product (AZ91) was degreased, pickled, and treated with a treatment solution containing 100 g/or NHaFHF under conditions of 100 AC and 2 minutes of treatment time.
A translucent oxide film made of MgF2 with a thickness of ~1.5 μm was obtained.

Next, the above oxide film was coated with aluminum black 777.
(Aluminum Black 7??, manufactured by Kaname Co., Ltd.): Colored by immersing in a coloring bath at 50° C. with a concentration of 14 g/u for 5 minutes.

As a result, a beautiful magnesium die-cast product having a black-gray colored surface with metallic luster was obtained.

[Comparative Example 1] Regarding magnesium alloy plate (AZ31 equivalent product), Cr
O3: 180g/u, Fe (NO3)3.9H20
The sample was immersed for 30 seconds in a treatment solution at 25° C. containing: 40 g/fL and KF: 4 g/fL to obtain a beautiful treated surface exhibiting a satin-like silvery white luster.

Table 1 shows the results of the corrosion resistance test of the obtained magnesium alloy plate.

[Comparative Example 2] The treated magnesium alloy plate obtained in Comparative Example 1 was immersed in the same coloring bath as in Example 1 and colored under the same conditions, but no colored surface was obtained. .

[Comparative Example 3] A clear lacquer was sprayed on the treated magnesium alloy plate obtained in Comparative Example 1 (film thickness: 15 to 20 JLm).
), a painted product with a beautiful silvery white metallic luster was obtained.

Table 1 shows the results of the cross-cut test for this coated product.

[Comparative Example 4] After degreasing and pickling a magnesium alloy plate (equivalent to AZ31), Na2Cr20. e2H20:t80g/J
A so-called chromate treatment was carried out by immersing the sample at room temperature for 30 seconds using a treatment solution containing 70% HNOx: 190 ml/liter.

The corrosion resistance test results are shown in Table 1.

Table 1: Salt water spray i1 [After 1 hour, corrosion loss (g/m”) Test results 1
5.0 --2 0 , 0
100 /1003 3.0
--4 20.0 --Comparative example 1 80.2 --4 4
5, 0 -- [Evaluation results] As for corrosion resistance, as can be seen from the corrosion loss in Table 1,
Compared with the numerical values of Comparative Example 1 and Comparative Example 4, the values of the colored films having metallic luster according to the present invention (Examples 1 to 4) are significantly smaller, which is preferred. By the way, the corrosion weight loss of magnesium alloy plate (untreated product) is 155 g/rr.
It was f.

Furthermore, it was confirmed that the colored film according to the present invention was clearly superior in the cross-cut test showing the adhesion of the coating film.

Claims (1)

[Scope of Claims] 1. A molded body of magnesium or its alloy, characterized by having a colored anodic oxide film exhibiting translucency on its surface. 2. The molded body of magnesium or its alloy according to claim 1, wherein the transparent colored anodic oxide film has a thickness of 2 μm or less. 3. The thickness of the transparent colored anodic oxide film is 1.6 μm.
A molded article of magnesium or its alloy according to claim 2, which is as follows. 4. The thickness of the transparent colored anodic oxide film is 0.2 μm.
The molded body of magnesium or its alloy according to claim 1 or 2, which is as follows. 5. A molded article of magnesium or its alloy according to claim 1 or 2, wherein the molded article is colored with a dye for coloring alumite. 6. The anodic oxide film is MgO, MgO・Al_2O_3
, MgO・SiO_2, Mg(OH)_2, and Mg
The molded article of magnesium or its alloy according to claim 1 or 2, characterized in that it contains one or more compounds selected from the group consisting of F_2. 7. Anodizing a molded body of magnesium or its alloy to produce a translucent anodic oxide film on its surface;
A method for producing a molded body of magnesium or its alloy having a translucent colored anodic oxide film on its surface, the method comprising: then coloring this anodic oxide film using an alumite coloring dye. 8. The method for producing a molded body of magnesium or its alloy according to claim 7, wherein the transparent colored anodic oxide film has a thickness of 2 μm or less. 9. Colored anodic oxide film with transparency and film thickness of 0.2 μm
A method for producing a molded body of magnesium or an alloy thereof according to claim 8, characterized in that the above is performed. 10. Claim 7, characterized in that the dye for coloring alumite is one or more dyes selected from the group consisting of acid dyes, alloy metal complex dyes, and acid mordant dyes.
A method for producing a molded body of magnesium or an alloy thereof according to item 8 or item 8.