KR101543790B1 - Composition for Magnesium Alloy Surface Treatment and Magnesium Alloy Surface Treating Method using the Same - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a composition for metal surface treatment and a surface treatment method using the same. And at least one inorganic compound selected from the group consisting of a cerium compound, a vanadium compound, a fluorine compound, and a zirconium compound, and a surface treatment method for coating the surface of a magnesium alloy plate using the composition.

According to the present invention, there can be provided a composition for surface treatment of an inorganic metal in an amorphous form having excellent rust resistance and high temperature lubrication and a surface treatment method using the same.

Phosphoric acid compounds, silane compounds, titanium compounds, zirconium compounds, vanadium compounds, cerium compounds, fluorine compounds, rustproofing, high temperature lubricity, corrosion resistance

Description

TECHNICAL FIELD [0001] The present invention relates to a composition for surface treatment of a magnesium alloy, and a surface treatment method of a magnesium alloy using the same. BACKGROUND ART [0002]

The present invention relates to a composition for surface treatment of a magnesium alloy and a method for treating a surface of a magnesium alloy using the same.

Metal materials such as steel, aluminum, magnesium alloy or stainless steel plated with zinc in general are widely used for metal materials for home appliances as well as building materials and automotive steel sheets.

However, since these metals are easily corroded or contaminated, the metal material is subjected to a certain coating treatment on the surface of the metal material in order to prevent it, thereby imparting improved corrosion resistance or lubrication performance to the metal material.

Conventionally, a chromate treatment, a lubrication treatment or an inner fingerprint resin treatment has been used as a surface treatment method of metallic materials. Among them, the chromate treatment gives a steel sheet excellent surface corrosion resistance and paintability at a low treatment cost It has been widely used.

However, since chromium used in the chromate treatment is a typical pollutant, there has been a problem that it seriously damages the human body and the environment. Accordingly, measures are being taken to regulate the use of chromium in the world, .

Therefore, there have been proposed a number of development and methods for chrome-free surface treatment, lubrication treatment, or fingerprint processing as an environmentally friendly surface treatment method that excludes chromium. However, such a method is more resistant to corrosion than metal surface treatment without chromium And there is a problem that the lubricity is inferior.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a composition for metal surface treatment having excellent rust resistance and high temperature lubricity.

Another object of the present invention is to provide a metal material having a surface coated with a composition for metal surface treatment having the above-mentioned excellent rust-inhibiting properties and high-temperature lubricity.

It is still another object of the present invention to provide a method for surface treatment of a metal material using the composition for metal surface treatment having such excellent rust resistance and high temperature lubricity.

The present invention provides, as means for solving the above problems, a phosphoric acid compound; And at least one inorganic compound selected from the group consisting of a cerium compound, a vanadium compound, a fluorine compound and a zirconium compound.

Further, the present invention provides, as another means for solving the above problems, a metal steel plate; And a coating layer formed on one or both surfaces of the metal sheet and containing a composition for metal surface treatment according to the present invention.

The present invention further provides a method for coating a metal surface, comprising the step of applying the composition for metal surface treatment to a steel sheet at a dry coating amount of 10 to 1000 g / m < 2 > To a surface of the metal material.

The metal surface treatment composition of the present invention as described above exhibits excellent lubricity at high temperatures and has excellent rust resistance, so that it can be usefully coated on the surface of a metal material such as a magnesium alloy or an aluminum alloy.

The present invention relates to a phosphoric acid compound; And at least one inorganic compound selected from the group consisting of a cerium compound, a vanadium compound, a fluorine compound and a zirconium compound.

Hereinafter, the composition for metal surface treatment of the present invention will be described in more detail.

As described above, the metal surface treatment composition of the present invention comprises a phosphoric acid compound; And at least one inorganic compound selected from the group consisting of a cerium compound, a vanadium compound, a fluorine compound and a zirconium compound.

Here, the phosphoric acid compound is a compound capable of being treated with a phosphate, and plays a role in improving corrosion resistance and lubricity in the metal surface treatment composition.

The phosphoric acid compound is not particularly limited as long as it is a phosphoric acid compound capable of improving lubricity and corrosion resistance, and more preferably includes nitric acid, manganese or nickel.

Specific examples of the phosphoric acid compound may include at least one member selected from the group consisting of polyphosphoric acid, phosphoric acid, zinc phosphate, manganese phosphate, phosphoric acid derivative and phosphorous acid, more preferably zinc phosphate solution or manganese phosphate solution have.

Further, it is preferable that the phosphoric acid in the phosphoric acid-soluble phosphate compound is contained at a concentration of 10 to 50 g / l based on PO ₄ .

When the amount of phosphoric acid is less than 10 g / l based on PO ₄ , the amount of amorphous phosphoric acid coating is too small to cause deterioration of lubricity and corrosion resistance. When the amount of phosphoric acid exceeds 50 g / l, scratches, There is a possibility that defects appear.

Also, nitric acid may be contained at a concentration of 1 to 10 g / l based on NO ₃ , manganese may be contained at a concentration of 1 to 15 g / l, and nickel may be contained at a concentration of 0.01 to 0.5 g / l.

That is, in the composition for metal surface treatment according to the present invention, the phosphoric acid compound may contain 10 to 20 parts by weight of the nitric acid component, 10 to 40 parts by weight of the manganese component and 0.1 to 5 parts by weight of the nickel component per 100 parts by weight of the phosphoric acid component have.

If the amount of the nitric acid component is out of the above-defined range, it may be difficult to form a smooth phosphate film. If the content of the manganese component and the nickel component is less than the above range, the corrosion resistance may not be sufficient. If the content exceeds the above range, there is a problem that efficiency is not improved because there is no further improvement in corrosion resistance in proportion to the addition amount.

However, the content of the nitric acid component, the manganese component, or the nickel component is not limited to the above-described numerical range, but may be variously modified within the range capable of forming an amorphous phosphate film in accordance with the object of the present invention .

Meanwhile, the composition for metal surface treatment according to the present invention includes at least one inorganic compound selected from the group consisting of a cerium compound, a vanadium compound, a fluorine compound, and a zirconium compound for improving rust resistance or corrosion resistance.

Here, the composition for metal surface treatment according to the present invention may contain 200 to 1300 parts by weight of an inorganic compound per 100 parts by weight of the phosphoric acid compound. However, as described above, the phosphoric acid compound may be mixed and used in a complementary manner to the extent that the lubricity and corrosion resistance of the composition for metal surface treatment according to the present invention do not deteriorate.

In the case where the inorganic compound is contained in an amount of less than 1 part by weight in the composition for metal surface treatment according to the present invention, there is a problem that the corrosion resistance is promoted by non-uniform treatment, There is a problem in that the efficiency is lowered because the lubricating property and the corrosion resistance are not improved as compared with the addition amount.

Here, the cerium compound may be any one selected from the group consisting of a trivalent cerium compound, a tetravalent cerium compound, and a mixture thereof. The mixture of the trivalent cerium compound and the tetravalent cerium compound is a mixture of trivalent cerium and tetravalent cerium It is preferable that the ratio of cerium is 0.3 to 0.7.

Examples of the trivalent cerium compound include cerium acetate III, ammonium cerium nitrate III, cerium carbonate III, cerium chloride III, cerium fluoride III, cerium nitrate III, ), Cerium bromide (III), cerium iodide (III), cerium oxalate (III), cerium perchlorate (III), cerium sulfide (III) and their hydrates. The tetravalent cerium compound is cerium hexanitrate (IV) salt, ammonium cerium sulfate and cerium sulfate.

In addition, the cerium compound preferably contains 200 to 700 ppm, more preferably 250 to 600 ppm, based on the cerium metal component.

Specifically, for example, a trivalent cerium compound in which a cerium nitrate salt (Ce (NO ₃ ) ₂ .6H ₂ O) is subjected to an aqueous solution is used, or the ratio of cerium and tetravalent cerium Of cerium compounds mixed at 3 to 5: 5 to 7, respectively.

Here, the vanadium compound is used for improving the corrosion resistance. The vanadium compound used in the present invention is one kind selected from the group consisting of sodium vanadate, ammonium vanadate, vanadium nitride and vanadium oxide Or more.

However, the vanadium compounds used in the present invention are not limited to those exemplified above, and various vanadium compounds may be included according to the purpose of the present invention.

The vanadium oxide is preferably a compound represented by the following formula (1).

VxOy

Here, x may be any one of 1 to 4, and y may be 3, 4, 5, or 7.

The vanadium compound preferably contains 30 to 300 ppm, more preferably 30 to 200 ppm, based on the vanadium metal component.

The zirconium compound used in the present invention is meant to include both a zirconium compound and a fluorine-containing zirconium fluoride compound, and specific examples thereof include nitrate zirconium Zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, zirconium fluoride, and the like.

However, the zirconium compound used in the present invention is not limited to those illustrated above, and various zirconium compounds and fluorine-containing zirconium fluoride compounds may be included according to the purpose of the present invention.

The zirconium compound may include 100 to 700 ppm, more preferably 100 to 650 ppm, based on the zirconium metal component, and may include 300 to 2000 ppm, more preferably 350 to 1900 ppm, based on the zirconium fluoride (ZrFx) .

Specific examples of the fluorine compound include fluorine compounds such as hydrofluoric acid, hexafluorophosphoric acid (HPF ₆ ), fluorophosphoric acid (H ₂ PO ₃ F), fluorosilicic acid (H ₂ SiF ₆ ) and sodium hexafluoro titanate (Na ₂ TiF ₆ ), but the present invention is not limited thereto.

The fluorine compound preferably contains 1000 to 2500 ppm based on the fluorine component.

Meanwhile, the pH of the composition for metal surface treatment according to the present invention is preferably 1.5 to 3.5.

When the pH of the composition is less than 1.5, it may be difficult to produce an effective passivation film on the upper layer due to excessive etching reaction, thereby failing to exhibit corrosion resistance and lubrication characteristics properly. When the pH exceeds 3.5, The etching reaction may not be sufficient and defects may be formed which can not form an effective passive film on the upper layer, which may lower the corrosion resistance.

Therefore, an additive may be added to adjust the pH of the composition for metal surface treatment according to the present invention to the above-mentioned numerical range. Specific examples of the additive for lowering the pH of the composition include phosphoric acid, ammonium monophosphate, An inorganic acid, an organic acid such as acetic acid or citric acid, or the like can be used.

In addition, the composition for metal surface treatment according to the present invention preferably further comprises 0.1 to 5 parts by weight of a coupling agent selected from a silane compound or a titanium compound.

Further, when the coupling agent is contained in an amount less than 0.1 part by weight, it is difficult to exhibit sufficient corrosion resistance. When the coupling agent exceeds 5 parts by weight, further improvement in physical properties can not be expected in proportion to the addition amount. There is a problem that efficiency is low.

The coupling agent may be added to the metal surface treatment composition to be coated together with the metal material to improve the adhesion and corrosion resistance with the material by coupling an inorganic material such as the phosphate compound, After the treatment composition is coated on the metal material, a thin film may be formed and coated on the coated metal surface treatment composition.

Here, the silane compound may be at least one selected from the group consisting of an amino silane, an epoxy silane, an acrylic silane, a mercapto silane, a vinyl silane, and a mixture thereof.

Specific examples of the silane compound include 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 1,2-bis-triethoxysilylethane, 3-methaglyoxypropyltrimethoxy Silane, N- (? -Aminoethyl) -? - aminopropylmethyldimethoxysilane, N- (? -Aminoethyl) -? - aminopropyltrimethoxysilane,? -Glycidoxypropyltriethoxysilane,? - glycidoxypropylmethyldimethoxysilane, and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.

Further, it is more preferable that the silane compound is a mixture of a silane compound having a functional group capable of reacting with the end-stage organics and a silane compound having no functional group.

As a specific example, an amine-based silane compound or a glycidyl-based silane compound can be used as a silane compound having a functional group capable of reacting with an organic substance, and as the silane compound having no organic functional group capable of reacting with an organic substance, , 2-bistriethoxysilylethane, and the like can be used. However, the silane compound according to the present invention is not limited to the above exemplified materials.

In addition, the titanium compound is preferably at least one selected from the group consisting of titanium nitrate, titanyl sulfate and titanium lactate. However, the titanium compound according to the present invention is not limited to the above exemplified materials.

The coupling agent may be an acidic aqueous solution prepared by adding acetic acid or phosphoric acid or the like so that the pH of the coupling agent is 2.0 to 3.5 to facilitate the hydrolysis of the methoxy or ethoxy moiety at the terminal, or adding ammonia water or triethylamine to adjust the pH to 8.5 To 10.5. ≪ / RTI >

The composition for metal surface treatment may have the composition as described above, and may be mixed with a solvent such as water.

The present invention also relates to a metal plate, And a coating layer formed on one or both surfaces of the metal sheet and containing a composition for metal surface treatment according to the present invention.

Here, the metal steel sheet refers to a metal used for automobile materials, household appliances, building materials and the like, specifically a metal such as an iron plate, and any steel sheet commonly used in the art can be used for this purpose , Preferably a cold-rolled steel plate; Galvanized electroplated steel sheets such as galvanized steel sheets, zinc-nickel-plated steel sheets, zinc-iron-plated steel sheets, zinc-titanium-coated steel sheets, zinc-magnesium coated steel sheets, zinc manganese-coated steel sheets and zinc- Hot - dip galvanized steel; Aluminum-plated steel sheet; A plating steel sheet containing a different metal or an impurity such as cobalt, molybdenum, tungsten, nickel, titanium, aluminum, manganese, iron, magnesium, tin or copper in these plating layers; A coated steel sheet in which inorganic substances such as silica and alumina are dispersed in these plating layers; Or an aluminum alloy plate to which silicon, copper, magnesium, iron, manganese, titanium, zinc or the like is added; Or zinc phosphate coated with phosphate; Or a hot-rolled steel sheet may be used, and if necessary, a multi-layered plated sheet obtained by sequentially treating two or more kinds of the above-mentioned platings may be used.

In addition, the metal sheet is preferably zinc-plated steel, a magnesium alloy, an aluminum alloy or stainless steel, and more preferably a magnesium alloy or an aluminum alloy.

In the coating layer containing the metal surface treatment composition, the metal surface treatment composition is preferably applied at a dry film amount of 10 to 1000 mg / m ² , more preferably 30 to 500 mg / m ² can do.

If the dry coating amount of the coating layer containing the composition is less than 10 mg / m 2, the corrosion resistance and processability may be reduced. If the coating amount exceeds 1000 mg / m 2, the weldability and lubricity may decrease.

As described above, since the metal material including the coating layer containing the metal surface treatment composition according to the present invention contains no chromate, it is harmless to the human body and can reduce the risk of environmental pollution, and also has excellent high temperature lubrication and corrosion resistance And thus can be usefully used in various industrial fields.

In addition, the present invention relates to a method for treating a surface of a metal material, comprising the step of applying the above composition for metal surface treatment to a steel sheet at a dry coating amount of 10 to 1000 mg / m < 2 >

The surface treatment method of the metal material will be briefly described. First, the object to be treated is immersed in the metal surface treatment composition for a predetermined time, or the composition for metal surface treatment is sprayed on the object to be treated, It is possible to induce a passivation reaction.

In this case, the immersion time is preferably 5 to 90 seconds.

If the immersion time is less than 5 seconds, there is a problem that the reaction may not sufficiently occur. If the immersion time exceeds 90 seconds, excessive etching reaction may occur, resulting in a decrease in the passive film formation of an effective component or an excessively thick oxidized layer. There is a possibility that corrosion resistance and lubricity are lowered.

The reaction step of the surface treatment method of a metal material according to the present invention will be described in more detail. And a metal solution containing at least one inorganic compound selected from the group consisting of a zirconium compound, a cerium compound, a vanadium compound mule and a fluorine compound is dipped in the acid solution for a predetermined time, or the acid solution is sprayed on the metal plate, Wash thoroughly and dry naturally or at a temperature below 80 ° C.

However, the drying temperature of the metal sheet is not limited to the above-mentioned range, and various temperature conditions for drying the metal sheet can be applied in various ways.

The chemically treated steel sheet may be immersed in a solution containing the coupling agent or the solution containing the coupling agent may be coated on the chemically treated steel sheet by a method such as spraying or roll coating.

The coating amount of the metal surface treatment composition may be varied depending on the concentration of the coupling agent and the coating method. If the coating conditions are set based on the thickness of the coating after drying, It is preferable to apply the coating amount to the steel sheet. After coating the coupling agent, drying may be performed at 80 to 300 ° C, preferably at 80 to 280 ° C, and most preferably at 80 to 250 ° C. have.

If the drying temperature is lower than 80 캜, defects due to uncured curing may occur and friction coefficient may increase sharply upon rubbing with the mold, resulting in a significant deterioration in processability. If the drying temperature exceeds 300 캜, It is difficult to expect a further improvement in the physical properties, resulting in a disadvantage that the efficiency is low.

As a method of applying the metal surface treatment composition to a metal material, a conventional method such as a roll coating method, a shower squeeze method, a deposition method, and a spray method can be used.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the following examples.

[Examples 1 to 16]

PF-M1AM phosphate solution of Parkerizing Co., Ltd. was used as a phosphoric acid compound in the magnesium alloy sheet having a plate thickness of 0.6 mm, and other composition components were subjected to metal surface treatment with the composition shown in the following Table 1 Was prepared.

The coating solution as shown in the following Table 1 was immersed for 10 to 20 seconds to form a passive film, and then the silane compound was coated with a bar coater 3 to adjust the amount to a predetermined dry film amount. Lt; RTI ID = 0.0 > C, < / RTI > to prepare a post-treated magnesium alloy coated sheet.

[Comparative Examples 1 and 2]

A magnesium alloy coated plate was prepared in the same manner as in the above examples except that a coating solution having the composition shown in Table 1 was used.

water
Phosphate (pH = 3.0) Cerium compound Vanadium compound Fluorine compound Zirconium compound
pH Silane compound _{Ce (NO 3) 3 (Ⅲ} ) _{Ce (NO 3) 3 (Ⅲ} / Ⅳ) NaO ₃ V HF HPF ₆ H ₂ PO ₃ F H ₂ SiF ₆ Na ₂ TiF ₆ ZrO · XH ₂ O H ₂ ZrF ₆ BTSE GPS diluent PO ₄ : 22 g / L 0.05 mol 0.05 mol 0.1 mol 2 mol 0.25 mol 0.5 mol 0.2 mol 0.08 mol 0.1 mol 0.5 mol Example 1 1500 30 - - 30 30 - - - - - - 2.5 2 One 2 1500 22.5 - - 60 30 - - - - - - 2.85 1.5 1.5 3 1500 22.5 15 52.5 - 24 - 6 12 - - 6 2.61 2 One 4 1500 22.5 15 105 - 30 - - 12 - - 6 2.9 2 One 5 1500 22.5 15 52.5 30 15 12 - 12 - - 6 2.72 2 One 6 1500 22.5 - - - 15 6 12 - - - 15 2.83 2 One 7 1500 22.5 - - - 15 6 6 - - - 30 2.98 2 One 8 1500 22.5 - - - 15 - - 30 - - 9 2.88 2 One 9 1500 22.5 - - 15 15 - - 30 22.5 - 6 2.88 0.5 0.5 10 1500 22.5 - - - - - - 12 45 - 15 2.71 2 One 11 1500 22.5 - 75 15 15 6 9 30 9 - 2.71 One One 12 1500 18 - 75 21 24 6 6 48 9 - 3.00 2 One 13 1500 30 15 75 - 45 - - 24 - 4 2.72 3 2 14 1500 30 15 75 - 80 - - 18 - 8 2.63 2 One 15 1500 18 15 75 - 60 8 12 - - 16 2.74 2 One 16 1500 30 - 52.5 - - 12 9 18 - 24 2.80 0.3 0.2 Comparative Example 1 1500 22.5 - - - - - - - - - 3.4 2 One 2 1500 - - - 30 120 - - - - - 3.64 2 One

[Experimental Example]

The corrosion resistance, lubricity and the like of the surface-treated plate according to the examples and comparative examples were measured, and the results are shown in Table 2 below.

1. High temperature lubricity test

Specimens were prepared by spraying silicone oil (domestic commercially available silicone release material, general purpose) used for warm forming at about 250 ° C on the surface-treated plate according to the above Examples and Comparative Examples, The friction coefficient was measured after performing a simple friction test on the specimen at the temperature of.

Here, the value measured after applying the silicone oil to the reference uncoated steel sheet was 0.127 to 0.129, and the following values were evaluated based on the above values.

?: Friction coefficient of 0.110 or less,?: 0.111 to 0.125,?: 0.126 to 0.130, X: 0.131 or more

2. Warm formability test

Using a specimen specimen designed to heat molds and punches, a specimen of 200 x 200 mm was used to measure the limit dome height (LDH) at a temperature of 250 ° C without additional heating, Respectively. In the case of the uncoated steel sheet as a standard, the LDH was 29 to 30 mm.

?: 34 or more,?: 31 to 33,?: 29 to 30, 占: 28 or less

3. Rustproofness test.

The specimens coated with the chemical treatment and the coupling agent were cut into 75 × 150 mm, and each of the cut portions was wrapped with a 3M tape so as to have a thickness of 5 mm.

Then, after then has a salt water of 5%, holding the specimen in at a temperature of 35 ℃, 1kgf / a spray amount of cm ² as a fog on the specimen salt spray tester salt spray (JIS 2371) with 15 ° angle 24 hours The extent of rusting in all specimens was measured and evaluated as follows.

?: 0 to 5%,?: 6 to 10%,?: 11 to 30%, X: more than 30%

division High temperature coefficient of friction Warm Moldability Rustproofing Example 1 ○ ◎ ○ Example 2 ○ ○ ◎ Example 3 ○ ◎ ○ Example 4 ◎ ○ ○ Example 5 ◎ ◎ ◎ Example 6 ◎ ○ ◎ Example 7 ○ ○ ○ Example 8 ○ ○ ○ Example 9 ○ ○ ◎ Example 10 ◎ ○ ◎ Example 11 ○ ○ ◎ Example 12 ◎ ◎ ◎ Example 13 ◎ ◎ ◎ Example 14 ◎ ◎ ◎ Example 15 ◎ ○ ○ Example 16 ◎ ◎ ○ Comparative Example 1 ○ △ × Comparative Example 2 × △ ×

Claims (15)

TECHNICAL FIELD The present invention relates to a composition for surface treatment of magnesium alloy, The composition, based on 1500 parts by weight of water, 18 to 30 parts by weight of a phosphoric acid compound; 67.5 to 90 parts by weight of a cerium compound; 39 to 98 parts by weight of a fluorine compound; And 21 to 30 parts by weight of a vanadium compound, and 6 to 8 parts by weight of a zirconium compound; Wherein the magnesium alloy is at least one selected from the group consisting of magnesium and magnesium. The method according to claim 1, Wherein the phosphoric acid compound is at least one selected from the group consisting of polyphosphoric acid, phosphoric acid, zinc phosphate, manganese phosphate, phosphoric acid derivative and phosphorous acid. The method according to claim 1, Wherein the cerium compound is a trivalent cerium compound, a tetravalent cerium compound, or a mixture thereof. The method of claim 3, Wherein the mixture has a ratio of trivalent cerium to tetravalent cerium of from 0.3 to 0.7. The method according to claim 1, Wherein the vanadium compound is at least one selected from the group consisting of vanadium sodium, vanadium ammonium, vanadium nitride, and vanadium oxide. The method according to claim 1, Wherein the fluorine compound is at least one selected from the group consisting of hydrofluoric acid, hexafluorophosphoric acid, fluorophosphoric acid, fluorosilicic acid, and sodium hexafluorotitanate. The method according to claim 1, The zirconium compound is at least one selected from the group consisting of zirconyl nitrate, zirconyl acetate, zirconyl ammonium carbonate, zirconium acetylacetonate, zirconium fluoride zirconium, zirconium oxide, zirconium hydrofluoric acid, zirconium ammonium fluoride, and zirconium fluoride hydroxide By weight based on the total weight of the magnesium alloy. The method according to claim 1, Based on 100 parts by weight of the phosphoric acid compound, Wherein at least one compound selected from the group consisting of a cerium compound, a fluorine compound, a vanadium compound and a zirconium compound is contained in an amount of 200 to 1300 parts by weight. The method according to claim 1, wherein the pH of the composition is 1.5 to 3.5. The method according to claim 1, Wherein the coupling agent further comprises 0.1 to 5 parts by weight of a coupling agent selected from silane compounds or titanium compounds. 11. The method of claim 10, Wherein the silane compound is at least one selected from the group consisting of an amino-based silane, an epoxy-based silane, an acrylic-based silane, a mercapto silane, a vinyl-based silane and a mixture thereof. 11. The method of claim 10, Wherein the titanium compound is at least one member selected from the group consisting of titanium nitrate, titanyl sulfate and titanium lactate. Magnesium alloy; And A metal material comprising a coating layer formed on one or both sides of the magnesium alloy and containing the composition according to any one of claims 1 to 12. A method for surface treatment of a metal material, comprising applying the composition according to any one of claims 1 to 12 to a magnesium alloy at a dry coating amount of 10 to 1000 mg / m < 2 >, followed by drying at 80 to 300 deg. delete