KR20200076511A - Surface treatment process for magnesium parts and magnesium parts treated by using the same - Google Patents

Abstract

The present invention relates to a surface treatment method of a magnesium member and the magnesium member treated by using the same. More specifically, the present invention is to provide the surface treatment method of the magnesium member having a dense surface structure, and the magnesium member having the surface structure, which is treated by using the method. The surface treatment method of the magnesium member according to one embodiment of the present invention includes the following steps of: forming a porous aluminum oxide layer on a metal material by etching the surface of a magnesium metal material containing aluminum with an acid; and forming a coating layer by coating a polymer substance on the aluminum oxide layer.

Description

Method of surface treatment of magnesium member and magnesium member treated using the same {SURFACE TREATMENT PROCESS FOR MAGNESIUM PARTS AND MAGNESIUM PARTS TREATED BY USING THE SAME}

The present invention relates to a method for treating a surface of a magnesium member and a magnesium member treated using the same. More specifically, the present invention relates to a method for treating a magnesium member having a dense surface tissue and a magnesium member having a dense surface tissue treated using the same.

Magnesium is the 8th abundant material on earth, has a low specific gravity and is harmless to the human body, and has the advantage of being lightweight, and has the potential to be applied as interior and exterior materials of various products. In addition, the magnesium alloy not only has light weight, but also has excellent characteristics such as high vibration damping ability, excellent absorption against vibration and shock, excellent electromagnetic shielding properties, light weight, and high specific strength. However, the magnesium alloy has a disadvantage of not being processed at room temperature, and rolling or molding is a material that requires a temperature of 200°C or higher, and there is always a surface layer due to oxidation of magnesium on the surface of the magnesium alloy. Has many limitations.

Magnesium corrodes at most pHs, as shown in FIG. 1. Since it is excellent in oxidizing property and corrosion occurs a lot, defects occur in the chemical treatment process. In the surface treatment of magnesium alloys, defects such as defects in the process (appearance defects such as surface unevenness, defects such as chemical treatment or plating process) or defects such as adhesion to coating film or salt resistance after coating are characterized by density of the oxide or hydroxide film, which is the surface structure of magnesium. In most cases, it is caused by the low and low mechanical properties. This is the reason why researchers have been researching magnesium alloys with a dense surface structure and methods for manufacturing them.

In the case of a magnesium alloy, an oxidized film of about 10 nm exists and the composition of this layer is composed of magnesium oxide, magnesium hydroxide, and magnesium carbonate. When the surface layer of the magnesium alloy exposed in the air is immersed in water, the thickness changes to about 20 to 30 nm. And when the surface polishing process using water in the production process proceeds, the pH of the water used during the process changes to alkali and reaches to approximately pH 11, in which case the surface layer grows to approximately 50 nm. That is, the surface layer of the magnesium alloy includes MgO, Mg(OH) ₂ and MgCO ₃ , and when a buffing process using water is included, Mg(OH) ₂ is mainly present in the surface layer rather than MgO.

In general, during the surface treatment of magnesium alloy, it prevents defects such as appearance defects during the process, chemical conversion treatment or plating process, defects in coating film adhesion or salt resistance after coating, and ensures adhesion stability of the surface treatment layer to ensure mechanical properties. A magnesium alloy having a dense surface structure and a method for treating the surface were provided, but the coating thickness is very thin at 50 nm, and a sufficient reaction is not achieved. .

The present invention is to provide a method for treating a surface of a magnesium member and a magnesium member treated using the same. More specifically, it is intended to provide a surface treatment method of a magnesium member having a dense surface tissue and a magnesium member having a dense surface tissue treated using the same.

A method of treating a surface of a magnesium member according to an embodiment of the present invention includes the steps of etching a surface of a magnesium metal material containing aluminum with an acid to form a porous aluminum oxide layer on the metal material; And coating a polymer material on the aluminum oxide layer to form a coating layer.

In the step of forming an aluminum oxide layer; In the aluminum oxide layer includes a plurality of aluminum oxide, the size of the aluminum oxide may be 1 to 3 μm.

In the step of forming a coating layer; In the polymer material may be to include a silane-based.

Forming a coating layer; afterwards, coating the coating layer; may further include.

The painting may be either electrodeposition painting or spray painting.

Magnesium member according to an embodiment of the present invention, a magnesium metal material containing aluminum; A porous aluminum oxide layer on the metal material and including aluminum oxide; And a coating layer comprising a polymer material on the porous aluminum oxide layer. The magnesium metal material includes 1 to 50% by weight of aluminum and 50 to 99% by weight of magnesium with respect to 100% by weight.

The size of the aluminum oxide may be 1 to 3 μm.

The polymer material may include a silane-based material.

The thickness of the coating layer may be 1 to 3 μm.

A coating layer may be further included on the coating layer.

In the surface treatment method according to an embodiment of the present invention, magnesium hydroxide is controlled by acid etching, so that there is almost no generation of bubble defects in electrodeposition coating.

In the surface treatment method according to an embodiment of the present invention, aluminum oxide is concentrated by acid etching, which is excellent in maintaining corrosion resistance of the magnesium plate material.

In the surface treatment method according to an embodiment of the present invention, a silane-based polymer is coated on a sponge-form aluminum oxide, which is excellent in securing adhesion.

The surface treatment method according to an embodiment of the present invention has a very high price competitiveness compared to Plasma electrolytic oxidation for forming a chemical conversion film.

The magnesium member according to an embodiment of the present invention can be used for automobile exterior materials, automobile parts, household appliances, electronic products, or IT products.

1 is a Pourbaix diagram of magnesium.
2 is a schematic surface treatment process diagram of a conventional magnesium alloy.
3 is a schematic view of a surface-treated magnesium member according to an embodiment of the present invention.
4 is a cross-sectional photograph after nitric acid etching of an AZ31 plate material according to an embodiment of the present invention.
5 is a diagram showing the results of analyzing the components of the region 2 in FIG.
Figure 6 is a cross-sectional photograph after coating the silane-based material after nitric acid etching the AZ31 plate material according to an embodiment of the present invention.
FIG. 7 is a photograph in which an AZ31 plate material according to an embodiment of the present invention is etched in nitric acid and then coated with a silane-based material, followed by electrodeposition coating, to complete a water tightness test.
Figure 8 is a photograph of the AZ31 plate material according to an embodiment of the present invention after nitric acid etching, coating the silane-based material, electrodeposition coating, and then completing the salt spray test.

In this specification, terms such as first, second, and third are used to describe various parts, components, regions, layers, and/or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

In this specification, parts not related to the description are omitted in order to clearly describe the present invention, and the same reference numerals are assigned to the same or similar elements throughout the specification.

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated.

In this specification, the terminology used is only for referring to a specific embodiment, and is not intended to limit the present invention. The singular forms used herein also include plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” embodies a particular property, region, integer, step, action, element, and/or component, and the presence or presence of another property, region, integer, step, action, element, and/or component. It does not exclude addition.

In the present specification, the term "combination of these" included in the expression of the marki form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the marki form, the components It means to include one or more selected from the group consisting of.

In this specification, when it is said that a part is "on" or "on" another part, it may be directly on or on another part, or another part may be involved therebetween. In contrast, if one part is said to be "just above" another part, no other part is interposed therebetween.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are additionally interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted as ideal or very formal meanings unless defined.

In addition, unless otherwise specified,% means weight%, and 1 ppm is 0.0001% by weight.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and are conventional in the art to which the present invention pertains. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

Thus, in some embodiments, well-known techniques are not specifically described to avoid obscuring the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains.

2 is a surface treatment process diagram of a conventional magnesium alloy. In particular, the surface treatment of the magnesium alloy for use in automotive exterior materials, as can be seen in FIG. 2, requires electrodeposition coating, and thus there is a problem that securing performance after electrodeposition coating is essential for expanding demand.

In addition, in the case of the conventional invention related to a magnesium alloy having a dense surface structure and a method for treating the surface, there is a problem in that the film thickness of the chemical conversion treatment is very thin, and thus a bubble defect occurs during electrodeposition coating.

The inventors of the present invention have devised the present invention to solve this.

A method of treating a surface of a magnesium member according to an embodiment of the present invention includes the steps of etching a surface of a magnesium metal material containing aluminum with an acid to form a porous aluminum oxide layer on the metal material; And coating a polymer material on the aluminum oxide layer to form a coating layer.

Each step will be described below.

First, a surface of the magnesium metal material containing aluminum is etched with an acid to form a porous aluminum oxide layer on the metal material.

When a magnesium alloy containing aluminum is added to the acid, aluminum relatively strong to the acid remains, and only magnesium is etched. Using this, the surface is cleaned and the aluminum oxide is concentrated to form an aluminum oxide layer.

In this case, the cleaning of the magnesium surface is caused by the acid, and at the same time, corrosion resistance due to the concentration of aluminum is secured, and the oxide is controlled so that defects in the electrodeposition coating are rarely seen later. It is known that most of the bubble defects in the electrodeposition coating appear while evaporating moisture in the curing process, and according to this step, since the magnesium hydroxide is controlled, there are almost no bubble defects in the electrodeposition coating later.

In this case, the magnesium metal material containing aluminum may be a magnesium alloy containing aluminum, and more specifically, may be an AZ-based magnesium alloy.

In addition, the porous aluminum oxide layer may include a plurality of aluminum oxides, and the porous aluminum oxide layer may be a sponge-like nanostructure. The size of the aluminum oxide may be 1 to 3 μm.

Further, the acid may be a strong acid such as nitric acid, hydrochloric acid or sulfuric acid.

More specifically, the acid may be a solution containing 15 to 60 ml of 70% nitric acid in 500 ml to 1 liter of water.

In addition, the step of forming a porous aluminum oxide layer on the metal material by etching the surface of the magnesium metal material containing aluminum with acid may occur at room temperature for 15 to 60 seconds. More specifically, it may occur for 20 to 40 seconds.

Next, a polymer layer is coated on the aluminum oxide layer to form a coating layer.

When the sponge-formed aluminum oxide layer formed by acid etching is coated with a polymer such as a silane-based polymer, it is possible to make a chemical conversion treatment film having excellent adhesion and a high chemical conversion film thickness.

At this time, since the aluminum oxide layer is porous in the form of a sponge, a polymer permeates between pores during polymer coating, and as the polymer is coated thereon, the aluminum oxide layer and the polymer coating layer may be formed as a composite layer.

At this time, the polymer material may include a silane-based material. More specifically, in the case of a silane-based polymer, it may be a TEOS silane-based polymer.

In addition, the thickness of the polymer coating layer formed in this step may be 1 to 3 μm. More specifically, it may be 1 to 2 μm.

In addition, the step of forming a coating layer by coating a polymer material on the aluminum oxide layer may occur under an alkali solution. More specifically, it may be under 1 to 10% of an alkali solution of NaOH or KOH.

In addition, under such an alkaline solution, 500 ml to 1 L of water may be coated with a polymer containing 20 ml to 60 ml of a polymer material.

In addition, the step of forming a coating layer by coating a polymer material on the aluminum oxide layer may occur for 1 to 10 minutes at a temperature of 40 to 80 ℃. More specifically, it may occur at a temperature of 50 to 70°C for 1 minute to 5 minutes.

Next, forming a coating layer; thereafter, coating the coating layer; may further include.

The painting may be either electrodeposition painting or spray painting.

As mentioned above, when the surface of the magnesium metal material containing aluminum is etched with acid to form a porous aluminum oxide layer on the metal material, bubble defects do not occur even through electrodeposition coating, and are used for automobile exterior materials, etc. Corrosion resistance of the surface-treated magnesium member can be secured.

Magnesium member according to an embodiment of the present invention, a magnesium metal material containing aluminum; A porous aluminum oxide layer on the metal material and including aluminum oxide; And a coating layer comprising a polymer material on the porous aluminum oxide layer. The magnesium metal material includes 1 to 50% by weight of aluminum and 50 to 99% by weight of magnesium with respect to 100% by weight. More specifically, aluminum may be 1 to 30% by weight, more specifically 2 to 10% by weight, and more specifically 2 to 5% by weight.

Figure 3 shows a schematic diagram of the surface-treated magnesium member according to an embodiment of the present invention.

First, the magnesium metal material containing aluminum may be a magnesium alloy containing aluminum, and more specifically, may be an AZ-based magnesium alloy.

Meanwhile, in the porous aluminum oxide layer including aluminum oxide, the size of the aluminum oxide may be 1 to 3 μm.

On the other hand, in the coating layer containing a polymer material, the polymer material may be one containing a silane system. In the case of a silane-based polymer material, it may be a TEOS-based silicone polymer material.

At this time, since the aluminum oxide layer is porous in the form of a sponge, a polymer permeates between pores during polymer coating, and a polymer is coated thereon, and the aluminum oxide layer and the polymer coating layer may be a composite layer.

Further, the thickness of the coating layer may be 1 to 3 μm. More specifically, it may be 1 to 2 μm.

In addition, a coating layer may be further included on the coating layer.

The magnesium member may be for automobile exterior materials, automobile parts, household appliances, electronic products, or IT products.

Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are only intended to illustrate the present invention in more detail and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the items described in the claims and the items reasonably inferred therefrom.

Example

The AZ31 plate was etched with 18 ml of 70% nitric acid (HNO ₃ ) and 500 ml of DI for 30 seconds at room temperature.

Fig. 4 shows a cross section after nitric acid etching of the AZ31 plate material. In FIG. 4, the white portion represents pores. FIG. 5 shows the results of analyzing the components of site 2 in FIG. 4.

4 and 5, Mg is dissolved by nitric acid, Al remains, and a porous Al oxide is produced. The Al oxide layer at this time is in the form of a sponge.

Thereafter, to maximize adhesion, the silane-based polymer material is coated under an alkaline solution, and the conditions are coated with 20 ml TEOS / DI 1000 ml containing 1% KOH at 60° C. for 1 minute to 5 minutes.

6 shows a cross-section after nitric acid etching of the AZ31 plate material and coating the silane-based material. As can be seen in FIG. 6, when the polymer material is coated, it can be seen that a silane-based material is included in a porous position in the cross section as shown in FIG. 4, and the film thickness is thickened to about 2 μm.

Thereafter, electrodeposition painting was performed.

result

1. Water tightness test

Nitrate etching-Silane-based polymer coating-Electrodeposition coating of the AZ31 plate was tested for water tightness. The water tightness test was conducted by cross cutting test after 480 hours of immersion in water at 40°C for water tightness.

The results are shown in the specimen of FIG. 7. 7 is a photograph of the AZ31 plate material of the embodiment, after nitric acid etching, coating the silane-based material, electrodeposition coating, and then completing the water tightness test.

As can be seen in FIG. 7, since the film thickness became thick, the bubble defect of the electrodeposition coating disappeared, thereby maximizing performance.

2. Salt spray test

Nitrate etching-Silane-based polymer coating-Electrodeposition coating of the AZ31 plate material was tested by salt spray. The salt spray test was conducted by spraying the salt water and standing for 720 hours.

The results are shown in various pictures of FIG. 8. 8 is a photograph of the AZ31 plate material of the embodiment, after nitric acid etching, coating the silane-based material, electrodeposition coating, and then completing the salt spray test. In other words, this is a photograph of corrosion resistance after scribing various shapes of specimens.

As can be seen in Figure 8, it can be seen that the surface-treated magnesium member according to an embodiment of the present invention has excellent corrosion resistance.

The present invention is not limited to the above embodiments, but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains have other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that can be carried out. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (10)

Forming a porous aluminum oxide layer on the metal material by etching the surface of the magnesium metal material containing aluminum with acid; And
Coating a polymer material on the aluminum oxide layer to form a coating layer; Surface treatment method of a magnesium member comprising a.
According to claim 1,
In the step of forming the aluminum oxide layer; In,
The aluminum oxide layer includes a plurality of aluminum oxide,
The size of the aluminum oxide is 1 to 3 μm surface treatment method of the magnesium member.
According to claim 1,
In the step of forming the coating layer; In,
The polymer material is a method of treating a surface of a magnesium member containing a silane-based.
According to claim 1,
Forming the coating layer; afterwards,
Coating the coating layer; Surface treatment method of the magnesium member further comprising.
According to claim 4,
The coating,
Method of surface treatment of magnesium member which is either electrodeposition coating or spray coating.
Magnesium metal material containing aluminum;
A porous aluminum oxide layer on the metal material and including aluminum oxide; And
Located on the porous aluminum oxide layer, a coating layer comprising a polymer material; includes,
The magnesium metal material is a magnesium member containing 1 to 50% by weight of aluminum and 50 to 99% by weight of magnesium with respect to 100% by weight.
In claim 6,
The size of the aluminum oxide is 1 to 3 μm magnesium member.
The method of claim 6,
The polymer material is a magnesium member containing a silane-based.
The method of claim 6,
The thickness of the coating layer is 1 to 3 μm magnesium member.
The method of claim 6,
Magnesium member further comprising a coating layer on the coating layer.

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