KR101551406B1 - Surface treatment method for magnesium or magnesium alloy - Google Patents

Abstract

The present invention is characterized in that magnesium or a magnesium alloy is heat treated in a humidifying atmosphere at a temperature of 75 to 160 캜 at a humidity of 85 to 100% RH at a temperature of 100 캜 or lower and at 50 to 100% RH at a temperature of 100 캜 or higher, Forming a brucite coating on the surface of the magnesium or magnesium alloy, primer coating the surface of the magnesium or magnesium alloy subjected to the humidification heat treatment, and coating the surface of the magnesium or magnesium alloy coated with the primer with aluminum And depositing the magnesium or magnesium alloy on the surface of the magnesium or magnesium alloy.

Description

TECHNICAL FIELD [0001] The present invention relates to a surface treatment method of magnesium or magnesium alloy,

The present invention relates to a method for surface treatment of magnesium or a magnesium alloy, and more particularly, to a method of priming a magnesium or magnesium alloy to improve corrosion resistance, followed by forming an aluminum deposition layer in a vacuum.

Generally, magnesium or magnesium alloy is one of the new materials used in the manufacture of automobile parts and electronic devices such as computers and mobile phones because of its high mechanical strength, high dimensional stability and good mechanical properties.

In addition, magnesium or magnesium alloy can be lightly used, has a high impact resistance, is excellent in vibration absorbing property and electromagnetic wave shielding property, and can be widely used in household electric appliances.

However, such magnesium has a low corrosion resistance because it has a standard electrode potential of -2.363 V for a hydrogen electrode at 25 ° C. and has a disadvantage in that the corrosion rate increases when contacted with other electrically positive elements.

Therefore, many studies have been made to improve the corrosion resistance of magnesium alloys.

As a method for improving the corrosion resistance of a magnesium alloy, there is known a method of improving the corrosion resistance of a magnesium alloy by adding an alloying element or improving a corrosion resistance by performing a surface treatment process.

Examples of methods for improving the corrosion resistance of a magnesium alloy through a surface treatment process include anodizing and chromate treatment.

The anodizing treatment is a surface treatment method of improving the corrosion resistance, abrasion resistance and electrical resistance by forming a magnesium oxide layer on the surface of a material by using an electrochemical method. This method has the advantages of low manufacturing cost, simple process and easy management, but it is disadvantageous in that the process efficiency is not good and it takes time.

The chromate treatment is a method of chemical conversion using a chemical reaction between a treatment liquid and aluminum without using an electrical method, which enables a simple treatment at a relatively low cost, has a good corrosion resistance and uniform appearance. However, since the chromate treatment uses a heavy metal such as chromium, there is a problem that the environment is contaminated.

Another method for surface treatment of magnesium alloys is to mechanically polish the surface of the magnesium alloy or to paint the surface of the alloy by pretreating the coating. However, the surface of the magnesium alloy treated with such a method is always There is a surface layer due to the oxidation of magnesium and the surface layer is not densified and the coating adhesion is low, so there is a limit to improve the corrosion resistance.

Therefore, in order to improve the corrosion resistance, which is an important disadvantage of the magnesium alloy, development of a new surface treatment method such as making the oxide film on the surface of the alloy to be dense is required.

In order to solve the above-mentioned problems, the present invention provides a method of coating a magnesium or magnesium alloy with a primer coating and then depositing a metal such as aluminum on the surface thereof to produce various kinds of magnesium plates, castings, extruded materials, It is possible not only to form a dense corrosion resistant film having high adhesion to the surface of the magnesium alloy but also to control the thickness of the brucite crystal film by controlling the temperature and the humidity and also to control the thickness of the brucite crystal film by the vacuum deposition of aluminum, The present invention provides a surface treatment method of a magnesium or magnesium alloy which enhances corrosion resistance, adhesion to a film, and glossiness of a metal by realizing a mirror-like appearance.

According to one aspect of the present invention, magnesium or a magnesium alloy is heated to a humidity of 85 to 100% RH at a temperature of 100 ° C or lower and a temperature of 50 to 100% RH at a temperature of 100 ° C or higher within a temperature range of 75 to 160 ° C A step of forming a brucite coating on the surface of the magnesium or magnesium alloy, a step of primer coating the surface of the magnesium or magnesium alloy subjected to the humidification heat treatment, and a step of coating the surface of the magnesium or magnesium alloy There is provided a method for surface treatment of a magnesium or magnesium alloy comprising depositing aluminum on a surface thereof.

In this case, the primer is preferably any one of an acrylic primer and a modified silicone primer.

At this time, the thickness of the coating layer coated with the primer is preferably 1 to 5 탆.

It is preferable that the aluminum deposition is deposited by sputtering in an argon gas atmosphere and the thickness of the deposited aluminum coating layer is 1 to 5 탆.

In the humidifying heat treatment, the humidifying heat treatment is performed at a temperature of 100 ° C or less for 1 hour or more and 120 hours or less, and the humidification heat treatment can be performed at a temperature of 100 ° C or more for 2 hours or less.

On the other hand, the magnesium alloy may be at least one selected from AZ31 flame retardant added with AZ31, AZ61, Ca, or AM60.

According to the embodiment of the present invention, corrosion-resistant coating of magnesium and magnesium alloy of three-dimensional structure is possible.

In addition, by controlling the temperature and humidity, the thickness of the film can be adjusted in various ways, and corrosion can be prevented by generating a crack on the surface by X-cut.

In addition, one embodiment of the present invention can produce a magnesium plate which exhibits a beautiful metallic texture and gloss by applying a humidification heat treatment, a primer coating, a aluminum coating, and a transparent coating layer on the magnesium plate, It is possible to apply it directly.

In addition, the surface of the heat-treated magnesium and magnesium alloy can be treated with a primer and then aluminum can be deposited to simultaneously achieve corrosion resistance, film adhesion, and metallic luster.

FIG. 1 is a photograph of a specimen subjected to aluminum deposition only after a humidification heat treatment according to a comparative example of the present invention.
FIG. 2 is a photograph of a specimen in which aluminum is deposited after a humidification heat treatment and a primer treatment on a magnesium alloy according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

In the case of the aluminum alloy according to the embodiment of the present invention, a naturally occurring oxide film is dense and different from magnesium in that the corrosion resistance is maintained, and the magnesium alloy is exposed to a high temperature and high humidity environment, thereby forming a dense oxide film .

In the case of the aluminum alloy according to the embodiment of the present invention, a naturally occurring oxide film is dense and different from magnesium in that the corrosion resistance is maintained, and the magnesium alloy is exposed to a high temperature and high humidity environment, thereby forming a dense oxide film .

Examples according to the present invention are magnesium sheet, magnesium alloy, AZ31, AZ61, magnesium sheet materials including Ca (AZ31 flame retardant added with Ca), AM60 and the like, extruded materials and three-dimensional molded articles (kitchen container, Mg PCB, Various magnesium alloys are used. It is possible to perform humidification heat treatment even in a state where a hot lubricant or the like used for warm molding remains on the surface. Depending on the pickling conditions used in the surface pretreatment of the magnesium alloy, the growth of the coating can be accelerated or hindered. The magnesium alloy thus produced can also maintain corrosion resistance.

Further, according to one embodiment of the present invention, when the magnesium plate is subjected to the humidification heat treatment, the primer coating, and the aluminum is continuously deposited and the transparent paint layer is formed thereon, it can be directly applied to various mobile exterior materials .

Hereinafter, in order to simultaneously realize the coating adhesion and corrosion resistance of the pressurized and humidified heat-treated film made to produce the corrosion-resistant film, and the beautiful texture of the metal, the embodiment according to the present invention implements a humidification heat treatment on the surface of the magnesium alloy, A step of sequentially forming the primer coating and aluminum and then continuously depositing the primer coating and aluminum can be carried out sequentially. This makes it possible to control the thickness of the brucite coating formed on the surface of the magnesium or magnesium alloy in the humidification heat treatment step, to prevent the surface blackening phenomenon, and to treat the surface of the brucite coating so as to have metallic luster.

A method of surface-treating a magnesium alloy according to an embodiment of the present invention will be described.

Hereinafter, the magnesium alloy refers to a magnesium alloy casting pipe or the like including magnesium.

A surface treatment method of a magnesium alloy according to an embodiment of the present invention is a surface treatment method in which a surface of a magnesium alloy is subjected to a humidifying heat treatment and a primer coating and aluminum are deposited thereon.

First, a step of performing a humidifying heat treatment on the surface of the magnesium alloy will be described.

The humidification heat treatment of the magnesium alloy is to heat treatment in a humidifying atmosphere to form a brucite coating of Mg (OH) ₂ on the surface of the magnesium alloy. Such a humidifying heat treatment can form a blackened film having a high corrosion resistance on the surface of the magnesium alloy. At this time, various magnesium alloys such as Pure Mg and AZ31, AZ61, AZ91D, and AM60 have a considerable difference in the thickness of the coating at the same temperature and humidity, but coincide with the point that the blackening proceeds and corrosion resistance appears.

In an embodiment of the present invention, the temperature of the humidification heat treatment is not less than 75 ° C. and not more than 160 ° C., and the humidifying atmosphere is not less than 85 RH% and not more than 100 RH% at a low temperature of 100 ° C. or lower, % Or less. At this time, a humidifying heat treatment should be performed at a temperature of 100 ° C or lower for not less than 1 hour and not more than 120 hours, and a blackening film formed even at a time of not more than 2 hours at a temperature of 100 ° C or higher is stable for at least 48 hours in a salt spray test. The blackening film produced at a low temperature is thin and corrosion resistance is not exhibited, and the blackening film produced at a high temperature of 160 캜 or higher becomes bulky and crumbles.

Next, a primer coating is applied to the magnesium alloy subjected to the humidification heat treatment.

Primer coating generally means undercoating, and paints such as anticorrosive coatings, anticorrosive primers or simply primers can be used. It is preferable that such a primer includes a rust preventive pigment and a primer that is well-coupled with an aluminum deposition layer described later.

Such a primer should be maximally adhered to the surfaces of the aluminum deposition layer and the magnesium alloy to be described later, and also to enhance the adhesion with the aluminum deposition layer described later, and also to have a good resistance to cyan (Corrosion Resistance) .

For this purpose, the primer used in one embodiment of the present invention may be an acrylic primer or a modified silicone primer capable of sufficiently maintaining adhesiveness to the aluminum deposition layer.

When the primer is coated on the surface of the magnesium alloy, it may be formed to a thickness of 1 to 10 탆 so that there is no problem in showing the texture of the metal. Preferably, the primer is formed to a thickness of 1 to 5 탆 so as to maintain the adhesion with the magnesium alloy .

Next, as described above, a primer layer can be coated on the surface of the magnesium alloy, and then an aluminum vapor deposition layer can be formed. The aluminum deposition layer can be formed by thermal evaporation, sputtering, ion beam method, filament method, or the like.

When aluminum is deposited on the surface of the magnesium alloy on which the primer layer is formed, it is preferable to apply the sputtering method. This is because the ion beam method is disadvantageous to the continuous production process because it is an airtight type. However, when a small amount of outer casing for mobile is to be produced, it is also possible to apply the ion beam method, so that the ion beam method is not excluded from the scope of the present invention.

When aluminum is deposited on the magnesium surface by the sputtering method, it is preferable to apply the low temperature plasma method filled with argon gas.

As described above, when aluminum is deposited on the magnesium surface by sputtering in an argon gas atmosphere by a sputtering method, the thickness of the deposition layer is preferably 1 to 5 mu m.

When aluminum is vacuum deposited by sputtering, the degree of vacuum is 2 x 10 < ^-3 > torr, and the applied voltage is 350V to 400V.

In the case of the filament type, the degree of vacuum is 10 ^-5 torr to 10 ^-4 torr, the current is 60 A to 80 A, and the voltage is 1.6 V. At this time, the thickness of the aluminum deposition layer is preferably 1 to 5 mu m.

As described above, when aluminum is deposited on the surface of the magnesium alloy on which the primer layer is formed, the deposited aluminum deposited layer acts as a light reflecting layer, thereby realizing the luster and texture of the metal.

In the above description, aluminum is used as a material to be deposited on the surface of the magnesium alloy, but chromium may be deposited for the same purpose to form a chromium deposition layer.

In an embodiment of the present invention, a primer layer may be coated on the surface of a magnesium alloy, and then an aluminum layer may be deposited. Then, a transparent paint layer may be formed on the aluminum layer to maintain the metal texture while protecting the metal coating layer.

Hereinafter, another embodiment of the present invention will be described in detail.

In the embodiment according to the present invention, blackening can be easily prevented by performing the humidification heat treatment after the degreasing treatment and the pickling treatment of the magnesium alloy. That is, even if only pickling treatment is added before the humidification heat treatment process, blackening growth can be prevented. At this time, the hydrofluoric acid easily reacts with the surface of the magnesium alloy to form the MgF ₂ coating, so that the blackening can be easily prevented by preventing the change to the brucite. This is important when one side benefits heat conduction and the other side benefits heat dissipation.

FIG. 1 is a photograph of a specimen subjected to aluminum deposition only after humidification heat treatment according to a comparative example of the present invention, and FIG. 2 is a photograph of a specimen having aluminum deposited thereon after a humidification heat treatment and a primer treatment on a magnesium alloy according to an embodiment of the present invention. The magnesium alloy used was AZ31 alloy.

As shown in FIG. 1, the magnesium plate was molded into a cell phone shape, and then subjected to humidification heat treatment to form a bustite film, followed immediately by vacuum evaporation of aluminum. It can be seen that under these conditions, the metal does not have a glossy texture.

On the contrary, as shown in FIG. 2, the magnesium plate was formed into a convex circular shape, followed by humidification heat treatment to form a bustite coating, followed by primer coating, followed by aluminum vacuum deposition. It can be seen that under these conditions, the metal has a shiny, glossy texture inherent to the metal.

While the present invention has been described in connection with certain exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (7)

The magnesium or magnesium alloy is heat-treated in a humidifying atmosphere under the conditions of 85 to 100% RH at 100 DEG C or lower and 50 to 100% RH at 100 DEG C or higher within the temperature range of 75 to 160 DEG C, Forming a brucite coating on the surface of the alloy;
Primer coating the surface of the magnesium or magnesium alloy subjected to the humidification heat treatment;
Depositing aluminum on the surface of the primer-coated magnesium or magnesium alloy;
Containing
A method for surface treatment of magnesium or a magnesium alloy. The method according to claim 1,
Wherein the primer is any one of an acrylic primer and a modified silicone primer. 3. The method of claim 2,
Wherein the primer coating is applied to a thickness of 1 to 5 占 퐉. The method of claim 3,
The aluminum deposition
A surface treatment method of a magnesium or magnesium alloy deposited by sputtering in an argon gas atmosphere. 5. The method of claim 4,
Wherein the thickness of the aluminum coating layer deposited on the surface of the magnesium or magnesium alloy is 1 to 5 占 퐉. 6. The method according to any one of claims 1 to 5,
Wherein the humidifying heat treatment is performed at a temperature of 100 ° C or less for 1 hour or more and 120 hours or less and a heat treatment is performed at a temperature of 100 ° C or more for 2 hours or less. The method according to claim 6,
Wherein the magnesium alloy is selected from AZ31 flame retardant having AZ31, AZ61, Ca added thereto, or AM60, or a magnesium or magnesium alloy using the same.

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