KR101440555B1 - A Surface Treatment Method of Aluminum Materials Having Superior Corrosion Resistance and of Aluminum Materials Which are Surface Treated Thereby - Google Patents

Abstract

The present invention relates to a surface treatment method of a magnesium material that exhibits excellent corrosion resistance by forming a silicon coating layer mediated by a magnesium oxide film, and a magnesium material surface-treated thereby. According to the present invention, there is provided a method for manufacturing a magnesium alloy, comprising the steps of: degreasing a magnesium material with an alkali solution or ammonia water; Forming a silicone coating layer on the degreased magnesium material with a silicon precursor sol gel composition comprising a silicon precursor, an alcohol and an acid catalyst; And drying the surface of the magnesium material; And a surface treated magnesium material comprising a magnesium material, a magnesium oxide film on at least one surface of the magnesium material, and a silicon coating layer on the magnesium oxide film. The magnesium material having the silicone coating layer formed by mediating the magnesium oxide film by the magnesium material surface treatment method according to the present invention exhibits improved corrosion resistance. Also, if necessary, the pigment may be added to the silicon coating layer to impart color to the magnesium material to give a sense of beauty. The magnesium material that has been subjected to the surface treatment by the method of the present invention and has been imparted with improved corrosion resistance is not limited thereto. For example, it can be applied to computers, mobile phones, automobile parts, precision electronic parts and home appliances.

Description

TECHNICAL FIELD [0001] The present invention relates to a surface treatment method of a magnesium material that provides excellent corrosion resistance, and a surface treated magnesium material,

The present invention relates to a surface treatment method of a magnesium material that gives excellent corrosion resistance and a surface treated magnesium material having excellent corrosion resistance obtained thereby. More particularly, the present invention relates to a magnesium material having excellent corrosion resistance by forming a silicon coating layer mediated by a magnesium oxide film A surface treatment method and a surface-treated magnesium material having excellent corrosion resistance obtained by the method.

The magnesium or magnesium alloy (hereinafter referred to as "magnesium material") has a density of about 1.8 g / cm ³ , which is about two-thirds of that of the aluminum alloy. Therefore, the magnesium or magnesium alloy has the lowest density among the commercially available structural alloys and has excellent non- It is excellent in castability, machinability and dimensional stability. Also, it is excellent in absorbability against vibration and impact, has excellent electric and thermal conductivity, workability, fatigue at high temperature, impact property, and has an electromagnetic wave shielding property that can efficiently shield electromagnetic waves generated in various electric device parts. Such magnesium materials have recently been widely applied to lightweight products such as computers, mobile phones, automobile parts, precision electronic device parts, and home appliances.

However, since the magnesium material exhibits a very large electrochemically active property, it exhibits a characteristic of being rapidly corroded in the atmosphere or in the solution when the surface treatment is not performed. Therefore, in order to put the magnesium product into practical use, a surface treatment method which improves corrosion resistance by chemical, electrochemical or physical treatment of the surface of the product is required.

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Surface treatment techniques to improve the corrosion resistance of magnesium materials include anodic oxidation, electroplating, electroless plating, painting, anodic oxidation, painting, and protective coating. Specifically, Korean Patent Application No. 2005-30369 proposes a magnesium surface treatment method for improving corrosion resistance and conductivity by improving a series of magnesium surface treatment processes of conventional chemical polishing, surface adjustment, chemical treatment and sealing treatment, And does not improve the post-treatment and environmental friendliness of the solution having the surface treatment process. Korean Patent Application No. 2003-83747 also discloses a method for converting an electrolyte containing chromium and manganese into an environmentally friendly electrolyte by adding a trivalent sodium electrolytic solution to an electrolyte containing chromium and manganese used in the conventional anodic oxidation method and by using the spark anodizing process, Thereby improving the abrasion resistance and the paintability. Korean Patent Application No. 2006-15360 proposes a surface treatment method for forming a solid oxide ceramic film on the surface of a magnesium alloy by generating an underwater plasma discharge on the surface of the magnesium alloy using an alkaline electrolytic solution. However, the method using the discharge in the electrolyte solution has a disadvantage of high power consumption. Therefore, there is a need for a method for surface treatment of magnesium materials that can achieve not only corrosion resistance but also good surface appearance properties at the same time.

Accordingly, an embodiment of the present invention provides a method for surface treatment of a magnesium material that exhibits excellent corrosion resistance using an oxide film formation property of magnesium.

Another embodiment of the present invention is to provide a magnesium material having excellent corrosion resistance.

According to one aspect of the present invention,

Degreasing the magnesium material with an alkali solution or ammonia water;

Forming a silicone coating layer on the degreased magnesium material with a silicon precursor sol gel composition comprising a silicon precursor, an alcohol and an acid catalyst; And

And drying the surface of the magnesium material.

According to another aspect of the present invention,

Magnesium material; There is provided a surface-treated magnesium material comprising a magnesium oxide film on at least one surface of a magnesium material and a silicon coating layer on the magnesium oxide film.

The magnesium material having the silicon coating layer formed by mediating the magnesium oxide film by the magnesium material surface treatment method according to an embodiment of the present invention exhibits improved corrosion resistance. Also, if necessary, a pigment may be added to the silicon coating layer to impart color to the magnesium material to give a sense of beauty. The magnesium material to which the surface treatment by the method according to the present invention is imparted with improved corrosion resistance is not limited to this, but has recently been applied to lightweight products such as computers, mobile phones, automobile parts, precision electronic parts, and household appliances .

1A is a photograph of a surface of a magnesium material used in the surface treatment of Example 1 before the corrosion resistance test.
1B is a photograph of the surface of a magnesium material used in the surface treatment of Example 1 after 24-hour salt spray test.
2A is a surface photograph of the magnesium material of Example 1 surface-treated with the Sol gel solution of Inventive Example 1 before the corrosion resistance test.
FIG. 2B is a photograph of the surface of the magnesium material of Example 1, which was surface-treated with a Sol gel solution of Inventive Example 1 after 24-hour salt spray test.
3A is a surface photograph of the magnesium material of Example 1 surface-treated with the Sol gel solution of Inventive Example 2 before the corrosion resistance test.
FIG. 3B is a photograph of the surface of the magnesium material of Example 1, which was surface-treated with a Sol gel solution of Inventive Example 2 after 24-hour salt spray test.
4A is a surface photograph of the magnesium material of Example 1 surface-treated with the Sol gel solution of Inventive Example 3 before the corrosion resistance test.
FIG. 4B is a photograph of the surface of the magnesium material of Example 1 surface-treated with a Sol gel solution of Inventive Example 3 after 24-hour salt spray test.

Magnesium is a metal with a low surface potential, so it is easily oxidized in the atmosphere and exhibits a weak corrosion resistance. Thus, the magnesium oxide formed on the surface of the magnesium material is passivated into a stable and dense magnesium oxide film containing MgO and (Mg) OH ₂ by degreasing treatment. The present invention is based on the fact that the stable magnesium oxide passivation film contributes to the improvement of the corrosion resistance of the finally surface-treated magnesium material. That is, it has been found that the corrosion resistance of magnesium is remarkably improved by forming a silicon film on the magnesium oxide film without removing the magnesium oxide film on the magnesium surface. The term "magnesium oxide film" as used herein means a passivated film comprising MgO and (Mg) OH ₂ .

The surface treatment method of a magnesium material according to the present invention can be applied to both magnesium and magnesium alloy materials as described above. In this specification, magnesium and magnesium alloys are referred to as "magnesium materials ". The magnesium alloy is not particularly limited, and the method according to the present invention can be applied to any magnesium alloy generally known in this technical field. Examples of the magnesium alloy include, but are not limited to, alloys including elements such as zinc and aluminum.

Before the silicon layer is formed, the magnesium material is first degreased with alkali or ammonia water as a pretreatment step. By degreasing, foreign substances such as oil and dust are removed from the magnesium material surface, and the magnesium oxide film on the surface becomes a stable and dense passivated magnesium oxide film. The degreasing of the magnesium material can be performed using any method and materials generally known in the art. For example, but not by way of limitation, the degreasing may be carried out with at least one degreasing solution selected from the group consisting of NaOH, KOH, and ammonia. The degreasing solution is preferably used at a pH of from 11 to 12 so that a stable and dense magnesium oxide film is formed. Although it is not limited thereto, it is preferable that the magnesium oxide on the magnesium oxide is sufficiently passivated to be formed into a solid magnesium oxide film at room temperature (25 캜) to 120 캜 for 3 seconds to 60 seconds. The degreasing condition may be suitably selected within the above range depending on the type of the magnesium material.

The degreased magnesium material forms a silicon coating layer on the magnesium oxide film using a silicon precursor sol gel composition (hereinafter referred to as "sol gel composition"). The sol-gel composition includes a silicon precursor, an alcohol, and an acid catalyst. In the sol-gel composition, the silicon precursor and the alcohol preferably include a silicon precursor: alcohol in a volume ratio of 3: 2 to 2: 1 in consideration of the dehydration condensation reactivity and the degree of reaction at the time of forming the silicon layer. Alcohol is used at the volume ratio of 99.5 wt% alcohol. When the concentration of the alcohol is changed, the amount to be used can be appropriately controlled according to the content of the hydroxyl group related to the dehydration condensation reaction in the alcohol, depending on the correlation between the concentration and the volume.

The acid catalyst may be added to the sol-gel composition so that the pH of the composition is 3 to 4 so as not to damage or deteriorate the surfaces of the magnesium material and the magnesium oxide film during the sol-gel coating.

Examples of such silicon precursors include, but are not limited to, tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrakis (2-methoxy Methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldiethoxysilane, gamma -butyldiethoxysilane, gamma -butyroxyethoxysilane, -Isocyanatepropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane,? -Chloropropyltrimethoxysilane,? -Mercaptopropyltrimethoxysilane,? -Aminopropyltriethoxysilane, or? - (2-aminoethyl) propyltrimethoxysilane), alkoxysilanes such as tetraisopropenyloxysilane, phenyltriisopropenyloxysilane, gamma -isocyanate propyltriiso A phenyloxy silane, γ- methacryloxypropyltrimethoxysilane captive peel triisostearate propenyloxy silane, γ- mercaptopropyl triisostearate propenyloxy silane or tetra-butenyl oxy silane and alkenyloxy silanes such as; Acyloxysilanes such as tetraacetoxysilane, methyltriacetoxysilane, gamma-mercaptopropyltriacetoxysilane, tetrapropionyloxysilane, phenyltripropionyloxysilane, or vinyltriacetoxysilane; (Dimethyliminooxy) silane, methyltris (dimethyliminooxy) silane, tetrakis (methyl-ethyl) silane, tetrachlorosilane, phenyltrichlorosilane, tetrabromosilane or benzyltribromosilane, Methoxypropyltris (dimethyloxy) silane, and? -Methacryloxypropyltris (dimethyliminooxy) silane.

Such alcohols include, but are not limited to, for example, ethanol and / or isopropyl alcohol. From the viewpoint of storage stability after preparation of the sol-gel composition, it is preferable to use isopropyl alcohol having a low water content. The sol gel composition is preferably stored at 25 占 폚 or lower in terms of storage stability, in particular, deterioration prevention.

The acid catalysts include, but are not limited to, for example, hydrofluoric acid (HF) and / or nitric acid. Particularly, since the magnesium oxide film is relatively stable to hydrofluoric acid, it is preferable to use hydrofluoric acid so as to contribute to enhancement of corrosion resistance of the magnesium that is finally treated without removing and / or damaging the magnesium oxide film under the silicon layer.

Further, a dye may be further added to the silicon precursor sol gel composition. By forming a silicone coating layer with a sol-gel composition containing a dye, various colors can be applied to magnesium to give aesthetics. As the dyes, inorganic dyes and / or organic dyes can be used. For example, the inorganic dye may be at least one selected from the group consisting of iron nitrate (Fe (NO ₃ ) ₃ ), ferric chloride (FeCl ₃ ), and cobalt nitrate (Co (NO ₃ ) ₂ ) Or more can be used. When the inorganic dye is used, the treated magnesium can be implemented in a brownish color.

Also, organic dyes include, but are not limited to, Rhodamine. When rhodamine is used, the treated magnesium can be realized in a pink-based color.

The hue can be realized in a variety of colors by adjusting the concentration of the added dye. If the dye is added excessively to the silicon precursor sol gel composition, the sol gel composition may be deteriorated. Accordingly, it is preferable that the inorganic dye is blended to 30% by weight or less based on the total weight of the sol-gel composition and 2% or less by weight of the organic dye. The dye is any additional component, and the lower limit addition amount is not particularly limited. The inorganic dyes and / or organic dyes may be used alone or in combination of two or more.

The sol-gel composition may be applied to the magnesium surface by any coating method generally known in the art. Although not limited thereto, the sol-gel composition can be applied by a method such as roll deposition, spray coating and the like. The sol gel composition may be applied such that the thickness of the dried silicone coating layer is 10 nm to 3 m. When the thickness of the coating layer is thinner than 10 nm, it is difficult to secure good corrosion resistance due to penetration of chlorine ions. When the thickness of the coating layer exceeds 3 탆, the coating layer may easily peel off and cracks may be generated in the coating layer.

After applying the Sol gel composition, it is dried to form a silicone coating layer. The drying may be performed at a temperature of 150 ° C to 200 ° C for a time during which the sol-gel composition is completely dried. Depending on the kind of the sol gel composition and the thickness of the coating layer, it can be completely dried by drying for about 30 minutes to 2 hours. If the drying temperature is less than 150 캜, the crosslinking reaction and dehydration by dehydration condensation of the silicon precursor are insufficient. When the temperature exceeds 200 ° C, the organics constituting the sol-gel composition can be burned.

On the other hand, if necessary, the silicon coating layer may be formed of a plurality of layers of two or more layers. When the silicon coating layer is formed of a plurality of layers, the uppermost silicon coating layer is dried for 30 minutes to 2 hours at a temperature of 150 to 200 캜, depending on the kind of the sol-gel composition and the thickness of the coating layer. However, the silicon coating layer other than the uppermost silicon coating layer is dried for 10 minutes to 30 minutes at a temperature of 150 ° C to 200 ° C for a time shorter than the uppermost layer drying time, specifically depending on the type of the sol gel composition and the thickness of the coating layer, . This is to ensure adhesion of the silicone coating layer to the silicone coating layer by preventing the silicone coating layer from being completely dried. When the silicon coating layer is made of a plurality of layers, it is possible to realize better corrosion resistance and functionality at the same time. Further, the uppermost layer may be a transparent layer containing no pigment.

By applying the Sol gel composition and heat-treating it during drying, the crosslinking reaction proceeds by dehydration condensation of the silicon precursor to form a firm and dense silica coating layer, which exhibits excellent corrosion resistance.

The surface treatment of the magnesium material by the method of the present invention is performed on the final product after the treatment. This is because the magnesium coating material is damaged after the surface treatment according to the present invention and the corrosion resistance is not exhibited.

According to the surface treatment method of the magnesium material according to the present invention, the magnesium material; There is provided a magnesium material including a magnesium oxide film on at least one surface of a magnesium material and a silicon coating layer on the magnesium oxide film. The surface treatment according to the present invention may be performed on one side or both sides of the magnesium material, if necessary.

The magnesium material to which the surface treatment is applied by the method of the present invention and is provided with improved corrosion resistance is not limited thereto. For example, magnesium materials that are widely applied to lightweight products such as computers, mobile phones, automobile parts, precision electronic parts, .

Hereinafter, the present invention will be described in detail with reference to Examples. The following examples illustrate the invention and are not intended to limit the invention.

Example 1: Surface treatment of magnesium material according to the present invention

The magnesium material (AZ31 plate) was degreased by immersing in ammonia water of pH 11 at room temperature for 3 minutes. On the other hand, a silicon precursor sol gel composition was prepared as shown in Table 1 below. Tetraethoxysilane (TEOS), and methyltriethoxysilane (MTES) and isopropyl alcohol were thoroughly mixed in a volume ratio of 2: 1: 2 in a sol-gel solution of Inventive Examples 1 to 3 and mixed with HF The acid catalyst was added so that the pH of the solution was 3-4. Then, as shown in the following Table 1, 1.3 mass% of rhodamine, 20 mass% Fe (NO ₃ ) ₃ , 20 mass% Fe (NO ₃ ) ₃ and 10 mass% Co (NO ₃ ) ₂ Of pigment were added.

Silicon precursor Alcohol Acid catalyst dyes Inventory 1 TEOS and MTES 99.5 wt% isopropyl alcohol HF Rhodamine 1.3 mass%, Inventory 2 TEOS and MTES 99.5 wt% isopropyl alcohol HF Fe (NO ₃ ) ₃ 20 mass% Inventory 3 TEOS and MTES 99.5 wt% isopropyl alcohol HF _{Fe (NO 3) 3 20 mass} % , and _{Co (NO 3) 2 10 mass} %

The degreased magnesium material was sprayed using a silicon precursor sol gel composition of Inventive Examples 1 to 3 to a dry film thickness of 1 mu m. Thereafter, the silicon precursor sol gel composition was heated and dried at 200 DEG C for 2 hours to form a silicone coating layer.

Example 2: Corrosion resistance test

The corrosion resistance test of the magnesium material (AZ31 plate) used in the surface treatment of Example 1 and the magnesium material surface-treated with the Sol gel solution of Inventive Examples 1 to 3 was carried out. The surface of the magnesium alloy before and after the 24- The photographs are compared and shown in Figs. 1 to 4.

The salt spray test was carried out by spraying a 5 wt% NaCl salt aqueous solution continuously for 24 hours in accordance with JIS Z 2371. As can be seen from FIGS. 1 to 4, it was confirmed that the surface of the magnesium plate (FIG. 1) which was not subjected to the surface treatment was strongly corroded. In contrast, it was confirmed that the magnesium material surface-treated by the method of the present invention (Figs. 2 to 4) was significantly less corrosion-resistant than the magnesium material after the 24-hour salt spray test.

In addition, it was confirmed that a color can be imparted to the magnesium material by adding the dye as shown in Table 1 to the sol gel solution to give a sense of beauty.

Claims (9)

Degreasing the magnesium material with an alkali solution or ammonia water;
A silicon precursor on the degreased magnesium material; Alcohol; Acid catalyst; And a silicon precursor sol gel composition comprising at least one dye selected from the group consisting of iron nitrate (Fe (NO ₃ ) ₃ ), ferric chloride (FeCl ₃ ), cobalt nitrate (Co (NO ₃ ) ₂ ) Forming a silicon coating layer; And
And drying the surface of the magnesium material.
The method of claim 1 wherein the silicon precursor sol gel composition comprises a silicon precursor, an alcohol and an acid catalyst, wherein the silicon precursor is selected from the group consisting of tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, Tetramethoxysilane, tetramethoxysilane, tetrabutoxysilane, tetrakis (2-methoxyethoxy) silane, tetrabenzyloxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane , Dimethyldiethoxysilane, diphenyldiethoxysilane,? -Isocyanatepropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane,? -Chloropropyltrimethoxysilane,? -Mercaptopropyltrimethoxy Silane,? -Aminopropyltriethoxysilane, or? - (2-aminoethyl) propyltrimethoxysilane), tetraisopropenyloxysilane, phenyltriisophene, Alkenyl such as phenyloxysilane,? -Isocyanate propyltriisopropenyloxysilane,? -Methacryloxypropyl triisopropenyloxysilane,? -Mercaptopropyltriisopropenyloxysilane or tetrabutenyloxysilane Oxysilanes; Acyloxysilanes such as tetraacetoxysilane, methyltriacetoxysilane, gamma-mercaptopropyltriacetoxysilane, tetrapropionyloxysilane, phenyltripropionyloxysilane, or vinyltriacetoxysilane; And tetrachlorosilane, phenyltrichlorosilane, tetrabromosilane or benzyltribromosilane, tetrakis (dimethyliminooxy) silane, methyltris (dimethyliminooxy) silane, tetrakis (Meth) acryloxypropyltris (iminooxy) silane, and? -Methacryloxypropyltris (dimethyliminooxy) silane.
The magnesium material surface treatment method according to claim 1, wherein the alcohol is at least one selected from the group consisting of ethanol and isopropyl alcohol.
The magnesium material surface treatment method according to claim 1, wherein the acid catalyst is at least one selected from the group consisting of hydrofluoric acid (HF) and nitric acid.
The method of claim 1, wherein the silicon precursor and the alcohol are mixed in a volume ratio of 3: 2 to 2: 1.
The magnesium material surface treatment method according to claim 1, wherein the acid catalyst is formulated so that the sol gel composition has a pH of 3 to 4.
delete The magnesium material surface treatment method according to claim 1, wherein the step of forming the silicon coating layer is repeated twice or more to form two or more silicon coating layers.
Magnesium material; A magnesium oxide film on at least one side of the magnesium material and a silicon coating layer on the magnesium oxide film,
Wherein the silicon coating layer is a surface treatment comprising at least one dye selected from the group consisting of iron nitrate (Fe (NO ₃ ) ₃ ), ferric chloride (FeCl ₃ ), cobalt nitrate (Co (NO ₃ ) ₂ ) Magnesium ash.

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