JP2001152393A - Surface treating method for magnesium alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a decorative surface remarkably improved in corrosion resistance and having metallic luster. SOLUTION: This method comprises the first process in which the surface of a magnesium alloy Mg is subjected to anodic oxidation treatment or chemical conversion treatment to form an oxide layer 1, the second process in which the surface of the oxide layer 1 formed by the first stage is coated with a thermosetting resin coating material to form a sealable resin layer 2, the third process in which the surface of the sealable resin layer 2 formed by the second stage is coated with a conductive coating material to form a conductive resin layer 3 and a fourth stage in which the surface of the conductive resin layer 3 formed by the third stage is subjected to plating treatment to form a plating layer 4.

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 for a magnesium alloy which imparts corrosion resistance and decorativeness with metallic luster to the magnesium alloy.

[0002]

2. Description of the Related Art Light metals such as aluminum alloys are frequently used in precision electronic devices or automobile parts for low energy consumption and high performance. Above all, there is a tendency to use magnesium alloys that can be reduced in weight by 30% or more than aluminum alloys. However, the magnesium alloy is the lightest among practical metal materials, but has poor corrosion resistance, so that a surface treatment for corrosion prevention for improving the corrosion resistance is indispensable. The surface treatment for the purpose of preventing corrosion of the magnesium alloy is specified in JIS.

[0003]

In these methods, a chromium compound such as sodium dichromate is used, which has inherent environmental problems and cannot provide sufficient corrosion resistance. (Surface) is a situation in which one has to rely on painting, and at present it is impossible to obtain the metallic luster possessed by magnesium alloys. For this reason, the prior art has a problem that the range of use of the magnesium alloy is limited.

The present invention has been made for the purpose of solving such problems of the prior art.

[0005]

Means for solving the above problems will be described below with reference to FIG. 1 corresponding to an embodiment.
explain. The present invention provides a first step of forming an oxide layer 1 by anodizing or forming a surface of a magnesium alloy Mg, and applying a thermosetting resin paint on the oxide layer 1 formed in the first step. A second step of forming the sealing resin layer 2 by forming a conductive resin layer 3 by applying a conductive paint on the sealing resin layer 2 formed in the second step. ,
And a fourth step of forming a plating layer 4 by plating on the conductive resin layer 3 formed in the third step.

[0006] In the above-described structure, the magnesium alloy Mg can be given sufficient corrosion resistance, and the outermost surface (surface) of the product can be given a metallic glossy decorative property.

[0007]

FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, Mg is a magnesium alloy, 1 is an oxide layer, 2 is a sealing resin layer, 3 is a conductive resin layer, and 4 is a plating layer.

The oxide layer 1 is formed by subjecting the magnesium alloy Mg surface to anodic oxidation treatment or chemical conversion treatment. Oxide layer 1
Is 0.1 to 40 formed from magnesium oxide or the like.
Micron metal oxide layer. The oxide layer 1 mainly composed of magnesium oxide improves the corrosion resistance of the magnesium alloy Mg and the adhesion to the sealing resin layer 2.

The sealing resin layer 2 is formed by applying a thermosetting resin paint on the oxide layer 1 formed in the first step.
In the oxide layer 1 formed on the magnesium alloy Mg surface,
There are micro pinholes that arise from the properties of magnesium metal. In the prior art, the underlying magnesium alloy Mg is corroded through the pinholes, so that the corrosion resistance has not been sufficiently satisfactory. According to the present invention, a sealing resin layer 2 of a thermosetting resin is formed on the oxide layer 1 in a thickness of 1 to 30 μm. The sealing resin layer 2 performs a kind of sealing action of filling the pinholes in the oxide layer 1 with a thermosetting resin, and prevents corrosion of the magnesium alloy Mg generated through the pinholes.

Further, the formed sealing resin layer 2 exhibits an anticorrosive action because the oxide layer 1 mainly composed of magnesium oxide is cut off from coming into direct contact with the outside air. at the same time,
The oxide layer 1 is provided with further durability and corrosion resistance by the function of the sealing resin layer 2. As the resin forming the sealing resin layer 2, in addition to the thermosetting resin, an ultraviolet curable resin, an electron beam curable resin, and a mixture of these resins can be used.

The conductive resin layer 3 is formed by applying a conductive paint on the sealing resin layer 2 formed in the second step. The conductive paint is obtained by mixing a conductive metal powder such as gold, silver, copper, aluminum, nickel, tin, and zinc with a thermosetting resin paint. The mixing ratio is 50 to 70% by weight of the conductive metal powder. By doing so, the bonding of the conductive metal powder becomes dense, and the conductivity required for the plating process performed in the next step can be obtained. As the thermosetting resin paint to be mixed, the same type as the thermosetting resin paint applied on the oxide layer 1 formed in the first step is used. In this case, delamination hardly occurs between the sealing resin layer 2 and the conductive resin layer 3.

The formation of the conductive resin layer 3 gives the magnesium alloy Mg, which has become an insulator by the coating and formation of the sealing resin layer 2 in the second step, the conductivity required for plating in the next step. can do. Further, the conductive resin layer 3 formed here also provides the magnesium alloy Mg with further corrosion resistance and durability, similarly to the sealing resin layer 2 in the second step.

The thus obtained corrosion resistance and durability show sufficient corrosion resistance and durability even with a plating solution used in the next step, and enable plating. As the resin to be mixed with the conductive metal powder, a thermosetting resin, an ultraviolet curable resin, an electron beam curable resin, and a mixture of these resins can be used.

The plating layer 4 is formed by plating on the conductive resin layer 3 formed in the third step. The metal forming the plating layer 4 is various metals such as copper, nickel, chromium, and zinc. In addition to electroplating, chemical plating, displacement plating, and vacuum plating are also possible.

The plating layer 4 is formed of the conductive resin layer 3 in the third step.
In addition to imparting metallic glossy decorativeness to the magnesium alloy Mg whose metallic luster has been eliminated by coating and forming, the hardening of the surface has the effect of further improving the anticorrosion and abrasion resistance.

Further, after the first-stage plating, a honing treatment (sand blasting) is applied to the plating-treated surface to form a matte surface, and then the surface is subjected to a second-stage plating to obtain a matt-like surface. It is also possible to obtain a metal surface.

[0017]

Next, the specific contents of the present invention will be described based on examples and comparative examples.

Example 1 An AZ31 magnesium alloy (96% magnesium, 3% aluminum, 1% zinc) was anodized to form a 5-micron oxide layer 1 on the surface (first step). A polyester resin was coated on the oxide layer 1 to form a 30-micron sealing resin layer 2 (second step). next,
A 15-micron polyester resin mixed with 60% by weight of silver powder was applied on the sealing resin layer 2 to form a conductive resin layer 3 (third step). Further, a bright nickel plating layer 4 having a thickness of 5 μm was formed on the conductive resin layer 3 (fourth step). The alloy plate sample thus obtained was used as sample 1
I named it.

Example 2 An AZ31 magnesium alloy was subjected to anodizing treatment, and
An oxide layer 1 of 5 microns was formed (first step). An epoxy resin was applied on the oxide layer 1 to form a 20-micron sealing resin layer 2 (second step). Next, an epoxy resin mixed with a copper powder equivalent to 60% by weight was applied on the sealing resin layer 2 by 15 μm to form a conductive resin layer 3 (third step). Further, a bright nickel plating layer 4 having a thickness of 5 μm was formed on the conductive resin layer 3 (fourth step). The alloy plate sample thus obtained was named Sample 2.

Example 3 An AZ31 magnesium alloy was anodized, and 3
An oxide layer 1 of 0 μm was formed (first step). A melamine resin was applied on the oxide layer 1 to form a 15-micron sealing resin layer 2 (second step). next,
A melamine resin mixed with 60% by weight of silver powder was coated on the sealing resin layer 2 by 25 μm to form a conductive resin layer 3 (third step). Further, the conductive resin layer 3
After a copper plating layer 4 having a thickness of 10 μm was formed thereon, a honing treatment (sand blasting treatment) was performed, and a bright nickel plating layer 4 was formed on this surface with a thickness of 5 μm (fourth).
Process). The alloy plate sample thus obtained was named Sample 3.

Next, the evaluation tests shown in Table 1 were performed on the samples 1 to 3 obtained in Examples 1 to 3 above, and as a result, good results could be obtained in any of the tests.

[0022]

[Table 1]

The following experiment was performed as a comparative example.

Comparative Example 1 An AZ31 magnesium alloy was subjected to a chemical conversion treatment to form a 5-micron oxide layer 1 (first step), and a polyester obtained by mixing 60% by weight of copper powder on the oxide layer 1 The resin was applied to a thickness of 20 microns to form a conductive resin layer 3 (third step). Next, a bright nickel plating layer 4 having a thickness of 5 μm was formed on the conductive resin layer 3 (fourth step). The alloy plate sample thus obtained was named Comparative 1.

Comparative Example 2 An AZ31 magnesium alloy was subjected to anodizing treatment to form an oxide layer 1 of 15 microns (first step). An epoxy resin was coated on this oxide layer 1 by 30 μm (second
Process). Next, an attempt was made to form a nickel plating layer on the epoxy resin layer by an electroless plating method, but the epoxy resin layer was violated by the plating solution and the plating layer could not be formed. The alloy plate sample obtained in the epoxy resin coating step was named Comparative 2.

Comparative Example 3 A 30 micron melamine resin was applied on an AZ31 magnesium alloy (second step), and a 20 micron polyester resin mixed with a 60% by weight layer of silver powder was applied thereon. The resin layer 3 was formed (third step). Next, a bright nickel plating layer 4 is formed on the conductive resin layer 3 by 5.
Microns were formed (fourth step). The alloy plate sample thus obtained was named Comparative 3.

Next, with respect to Comparative Examples 1 to 3 obtained in Comparative Examples 1 to 3, evaluation tests shown in Table 2 were carried out. As a result, good results could not be obtained in any of the tests.

[0028]

[Table 2]

In the present invention, the magnesium alloy Mg
AZ31 magnesium alloy (magnesium 96
%, Aluminum 3%, zinc 1%)
It is also applicable to magnesium alloys such as 91 and pure magnesium. As the thermosetting resin, a urea resin, a polyimide resin, or a silicone resin can be used in addition to those shown in the embodiments. Further, not only the thermosetting resin but also an ultraviolet curable resin or an electron beam curable resin can be used. It goes without saying that an alloy other than the metal used in the examples can be used as the conductive metal powder for imparting conductivity.

[0030]

As described above, the present invention provides:
A first step of forming an oxide layer by anodizing or forming a surface of the magnesium alloy, and applying a thermosetting resin paint on the oxide layer formed in the first step to form a sealing resin layer A third step of forming a conductive resin layer by applying a conductive paint on the sealing resin layer formed in the second step; and a conductive resin formed in the third step. And a fourth step of forming a plating layer by plating on the layer. Therefore, not only can the corrosion resistance be significantly improved, but also a decorative surface having metallic luster can be obtained. Therefore, according to the present invention, there is obtained an effect that the range of use of a magnesium alloy can be remarkably expanded as a housing of electronic equipment or an automobile part for which weight reduction is desired in recent years.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

[Explanation of symbols]

 Mg magnesium alloy 1 Oxide layer 2 Sealing resin layer 3 Conductive resin layer 4 Plating layer

[Procedure amendment]

[Submission Date] July 13, 2000 (2007.1)
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

Means for solving the above problems will be described below with reference to FIG. 1 corresponding to an embodiment.
explain. The present invention, first step and, sealing resin by applying a thermosetting resin coating on the oxides layer 1 to form an oxide layer 1 anodization or chemical conversion treatment to the surface of the magnesium alloy Mg A second step of forming the layer 2, and the same type of thermosetting as the thermosetting resin coating on the sealing resin layer 2;
A third step of forming a conductive resin layer 3 by applying a conductive coating material formed by mixing a conductive metal powder sexual resin coating, plating and on the electrically <br/> conductive resin layer 3 And a fourth step of forming the plating layer 4.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

[0030]

As described above, the present invention provides:
A first step of anodizing or chemical conversion treatment to the surface of the magnesium alloy forming the oxide layer, the forming the sealing resin layer by coating a thermosetting resin coating on the oxide layer 2 a step, on the sealing resin layer, the thermosetting resin
Apply conductive metal powder to the same type of thermosetting resin paint as the paint.
It comprises a third step of forming a conductive resin layer by applying a conductive paint formed by mixing, and a fourth step of forming a plating layer by plating on the conductive resin layer. . Therefore, not only can corrosion resistance be significantly improved,
A decorative surface with metallic luster can be obtained. Therefore, according to the present invention, there is obtained an effect that the range of use of a magnesium alloy can be remarkably expanded as a housing of electronic equipment or an automobile part for which weight reduction is desired in recent years.

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Claims (4)

[Claims] A first step of forming an oxide layer by anodizing or forming a surface of the magnesium alloy;
A second step of applying a thermosetting resin coating on the oxide layer formed in the step to form a sealing resin layer, and applying a conductive coating on the sealing resin layer formed in the second step. A third step of forming a conductive resin layer by coating, and a fourth step of forming a plated layer by plating on the conductive resin layer formed in the third step.
Surface treatment method of magnesium alloy comprising the steps 2. The method for treating a surface of a magnesium alloy according to claim 1, wherein the conductive paint is a mixture of a conductive metal powder and a thermosetting resin paint. 3. The method for surface treating a magnesium alloy according to claim 2, wherein the mixing ratio is 50 to 70% by weight of the conductive metal powder. 4. The thermosetting resin coating to be mixed is of the same type as the thermosetting resin coating applied on the oxide layer formed in the first step. Surface treatment method of magnesium alloy