KR20150075001A - SURFACE TREATMENT COMPOSITION HAVING EXCELLENT CORROSION RESISTANCE AND BLACKENING RESISTANCE AND METHOD FOR PREPARING SURFACE TREATED Zn-Al-Mg ALLOY PLATED STEEL SHEET USING THE SAME - Google Patents

Abstract

The present invention relates to a surface treatment solution excellent in corrosion resistance and black weather resistance, a Zn-Al-Mg alloy plated steel sheet surface-treated using the same, and a method for manufacturing the same. More specifically, Corrosion resistance and black degeneration, including 5 to 30 g / L of PO ₄ ^{3 -} ), 10 to 50 g / L of nitric acid group (NO ^{3 -} ), 5 to 30 g / L of colloidal silica and 5 to 20 g / An excellent surface treatment solution, a Zn-Al-Mg alloy plated steel sheet surface-treated using the same, and a method of manufacturing the same.
According to the present invention, it is possible to obtain a chromate surface treatment solution having an excellent corrosion resistance and an improved black weathering property in which the film surface does not change to black even in a high temperature and high humidity atmosphere. Such chromate surface treatment solution can be used for post- In the case of producing an Al-Mg alloy-plated steel sheet, even when the chromate adhesion amount is increased, the coating color on the surface of the coated steel sheet is not so deeply colored as yellow, and an excellent surface appearance can be maintained.

Description

TECHNICAL FIELD [0001] The present invention relates to a Zn-Al-Mg alloy coated steel sheet having excellent corrosion resistance and weathering resistance, and a Zn-Al-Mg alloy coated steel sheet using the same. BACKGROUND ART PLATED STEEL SHEET USING THE SAME}

The present invention relates to a surface treatment solution excellent in corrosion resistance and black weather resistance and a method for producing a Zn-Al-Mg alloy plated steel sheet surface-treated using the same. More particularly, the present invention relates to a surface treatment solution having excellent corrosion resistance and high- A surface treatment solution which improves the weathering resistance of the surface of the coating film which does not change to black and the coating color of the surface of the coated steel sheet is not strongly colored even when the chromate deposition amount is increased and maintains a beautiful surface appearance, Zn-Al-Mg alloy coated steel sheet.

Conventionally, zinc-plated steel sheets have been widely used as building materials, home electric appliances, and rustproof steel sheets for automobiles because they have better sacrificial properties than iron (Fe), and zinc-aluminum steel plates such as galvanized steel sheets Has been developed and mass-produced.

On the other hand, as depletion of zinc resources has come to a reality, new high corrosion resistant steel sheets have begun to emerge from the viewpoint of zinc consumption, as the years of zinc mining become shorter. That is, in order to manufacture a coated steel sheet excellent in corrosion resistance with less adhesion amount, a ternary alloy-plated steel sheet to which magnesium (Mg) is added in addition to aluminum (Al) . As a result, the corrosion resistance of the steel sheet is improved and the amount of the steel sheet is reduced.

The chromate treatment is carried out with the concept of chemical treatment for temporary rust prevention after the production of galvanized steel sheet. However, depending on the manufacturing conditions of the steel sheet, the processing or transportation conditions of the customer, and the storage environment of the coil, , Blackness, black spots, and the like. Accordingly, the manufacturers of coated steel sheets produce steel sheets by treating them with a post-treatment solution to prevent surface defects such as white rust and black shavings.

White rust is formed when zinc reacts with moisture and oxygen in the air to form zinc oxide. It is a standard for judging general corrosion resistance, but it can inhibit the occurrence of white rust when chromate treatment is carried out. The black color occurs due to the formation of oxygen-deficient zinc oxide (ZnO _{1 -X} ) under conditions of oxygen deficiency due to high temperature and high humidity environment or stacking of coils. At this time, the non-stoichiometric ZnO _{1 -X} ionic bonds of the formed O ^{2 -} lattice vacancies, such as Al ^{3 +} , P ^{5 +} , Na ⁺ , Cl ^- , F ^- and Cr ^{3 +} The impurity absorption of ZnO _{1 -X} due to the electron defects of odd-numbered ions is superimposed and visible light is absorbed and the surface of the steel sheet appears black.

Technologies and patents related to chromium (Cr) treatment have been known for a long time and have been mainly applied to galvanized steel sheets. A number of patents have been filed for the use of Cr ^{6 +} , Cr ^{3 +} , phosphoric acid, silica, silane, various minerals, and water-soluble or water-dispersible polymeric compounds.

In addition to the aluminum added to improve adhesion or corrosion resistance among the plating bath components, even if magnesium is contained in the plating layer, such blackening phenomenon becomes worse because the oxidation of magnesium is easier than the oxidation of zinc, It is known that magnesium is taken up to promote oxygen deficiency zinc oxide generation.

As No. Republic of Korea Patent Application No. 1994-0006039 for improving the corrosion resistance of the steel sheet, naeheuk modified, the No. 1995-0006281 or the like is disclosed, the contents of the chromic acid, phosphoric acid, non-reduced Cr ^{+ 3,} Si, V, F And the role of the same inorganic compound. However, addition of an additional component to the plating bath component has a problem in that it is difficult to manage the plating bath together with the cost increase.

Accordingly, when the present invention is applied to a surface treatment solution having excellent corrosion resistance and black degeneration and a treatment method thereof without the above-described problems, it is expected to be usefully applied in related fields.

Accordingly, one aspect of the present invention is to provide a chromate surface treatment solution excellent in corrosion resistance and black weather resistance.

Another aspect of the present invention is to provide a method for producing a Zn-Al-Mg alloy plated steel sheet that has been surface-treated to have excellent corrosion resistance and black degeneration using the chromate surface treatment solution of the present invention.

Another aspect of the present invention is to provide a Zn-Al-Mg alloy plated steel sheet which is surface-treated by the above-mentioned method and is excellent in corrosion resistance and black weather resistance.

According to one aspect of the invention, the total chromium of 10 to 50g / L, a phosphate group (PO ₄ ^{3 -)} 5 to 30g / L, nitrate group ^{(NO 3 -) 10 ~ 50g} / L, colloidal silica 5 ~ 30g / L , And a silane coupling agent in an amount of 5 to 20 g / L, is provided.

The reduction ratio (Cr ^{3 +} / total chromium) occupied by the chromium trivalent ions in the total chromium component is preferably 0.5 to 0.9.

The surface treatment solution preferably has a pH of 2 to 4.

It is preferable that the phosphoric acid group (PO ₄ ^3- ) is provided by at least one selected from the group consisting of chromium phosphate, orthophosphoric acid, ammonium primary phosphate and ammonium secondary phosphate.

It is preferable that the nitrate group (NO < ^{3 > -} ) is provided by at least one selected from the group consisting of chromium nitrate, nitric acid, and sodium nitrate.

The silane coupling agent is preferably at least one selected from the group consisting of glyoxylpropylsilane, methacryloxypropyltrimethoxysilane, and glyoxylpropylmethyldimethoxysilane.

According to another aspect of the present invention, there is provided a method of manufacturing a Zn-Al-Mg alloy coated steel sheet, comprising the steps of: And baking at a temperature of 40 to 80 캜, wherein the surface-treated Zn-Al-Mg alloy-plated steel sheet is produced.

The application step is preferably carried out with an adhesion amount of 20 to 100 mg / m < ² >.

According to another aspect of the present invention, there is provided a Zn-Al-Mg alloy coated steel sheet; And a surface treatment layer formed on at least one surface of the Zn-Al-Mg alloy plated steel sheet, wherein the surface treatment layer is a surface-treated Zn-Al-Mg alloy plated steel sheet / RTI >

The surface treatment layer is preferably formed with an adhesion amount of 20 to 100 mg / m ² .

According to the present invention, it is possible to obtain a chromate surface treatment solution having an excellent corrosion resistance and an improved black weathering property in which the film surface does not change to black even in a high temperature and high humidity atmosphere. Such chromate surface treatment solution can be used for post- In the case of producing an Al-Mg alloy-plated steel sheet, even when the chromate adhesion amount is increased, the coating color on the surface of the coated steel sheet is not so deeply colored as yellow, and an excellent surface appearance can be maintained.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

TECHNICAL FIELD The present invention relates to a chromate surface treatment solution which is essential for chromate treatment of a zinc alloy-plated steel sheet, a method for treating the chromate surface treatment solution and a surface-treated steel sheet obtained as a result of the treatment, and more particularly, This technique relates to a surface treatment solution which does not damage the surface appearance of a steel sheet.

According to the present invention, corrosion-resistant and naeheuk degeneration is provided a superior surface treatment solution, more particularly, to total chromium of 10 to 50g / L, a phosphate group (PO ₄ ^{3 -)} 5 to 30g / L, nitrate group (NO ^{3 -)} 10 to 50 g / L, colloidal silica 5 to 30 g / L, and silane coupling agent 5 to 20 g / L.

The total chromium content in the components of the surface treatment solution of the present invention is a major factor affecting the corrosion resistance of the chromate film. When the total chromium is less than 10 g / L, the adhesion amount of the chromate film is too small and the corrosion resistance is insufficient. The coating amount of the coating increases excessively and the color of the coating is colored yellow. As a result, the appearance quality is deteriorated. Therefore, the content of the total chromium component is preferably 10 to 50 g / L.

On the other hand, the reduction ratio (Cr ^{3 +} / total chromium) occupied by the chromium trivalent ions in the total chromium component is preferably 0.5 to 0.9. When the reduction ratio is less than 0.5, the proportion of the chromium 6 compound in the film becomes high, so that it tends to be colored in yellow, and the plated steel sheet is etched by post-treatment to deteriorate the workability. On the other hand, when the reduction ratio exceeds 0.9, the proportion of the chromium-containing compound in the film becomes too low, so that the self-repairing effect of the damaged chromium film is deteriorated and the corrosion resistance becomes insufficient.

The reduction ratio of the surface treatment solution can be determined by adding a reducing agent such as alcohols, polyhydric alcohols, saccharides and the like soluble in water to an aqueous solution of chromic acid anhydride or by adding at least one trivalent chromium compound selected from the group consisting of chromium phosphate, chromium nitrate and chromium fluoride Can be added. However, since the reducing power differs depending on the kind of the reducing agent, the amount of the reducing agent may vary depending on the kind of the reducing agent, but the reducing agent is not decomposed after the reaction and therefore has no effect on the performance of the solution.

If the pH of the surface treatment solution is less than 2, the etching reaction between the surface treatment solution and the plating layer is increased, so that the zinc eluted from the plating layer is likely to accumulate in the solution. Therefore, if the amount of zinc ions is increased, the stability of the surface treatment solution may be impaired or the corrosion resistance of the chromate film may be deteriorated by participating in the film formation. When the pH of the surface treatment solution exceeds 4, the trivalent chromium compound in the surface treatment solution precipitates in the form of the chromium hydroxide, which causes a problem that the solution stability is lowered.

The phosphoric acid group (PO ₄ ^3- ) contained in the surface treatment solution of the present invention is contained in an amount of 5 to 30 g / L and is at least one selected from the group consisting of chromium phosphate, orthophosphoric acid, ammonium phosphate monobasic and ammonium phosphate May be provided by one.

When the amount of the phosphoric acid group (PO ₄ ^3- ) is less than 5 g / L, precipitation or gelation of the surface treatment solution may be induced to impair solution stability. This is because the phosphoric acid component is insufficient, This is because the generated chromium trivalent ions are not present in stable chromium phosphate form. Further, the phosphoric acid component contributes to the corrosion resistance by improving the adhesion between the material and the film, so that when the amount thereof is insufficient, the corrosion resistance may be poor. On the other hand, when the phosphoric acid component exceeds 30 g / L, the coatability of the coat is reduced, the film is not dried sufficiently, and the coat quality can be deteriorated.

The nitrate group (NO ^3-) contained in the surface treatment solution of the present invention is contained in an amount of 10 to 50g / L, it may be provided by at least one selected from the group consisting of chromium nitrate, nitric acid and sodium nitrate .

The nitric acid (NO ^{3 -} ) component, similar to the phosphoric acid component, allows the trivalent chromium ions generated in the solution to exist in stable chromium nitrate form and helps improve the resistance to intumescence. Therefore, when the content of the nitric acid group is less than 10 g / L, the stability and black weather resistance of the solution are insufficient. When the content of the nitric group is more than 50 g / L, I do not.

The surface treatment solution of the present invention preferably contains colloidal silica in an amount of 5 to 30 g / L, and the colloidal silica component increases the degree of crosslinking of the coating through a crosslinking reaction with the chromium compound while the coating is dried, . When the colloidal silica component is less than 5 g / L, the effect of improving the corrosion resistance is insufficient. When the colloidal silica component is more than 30 g / L, the corrosion resistance due to the formation of a dense coating film can be expected to be improved. Is rather undesirable.

Separately from the colloidal silica, a silane coupling agent is used for improving the degree of crosslinking of the chromate film, and the silane coupling agent is preferably contained in the surface treatment solution of the present invention in an amount of 5 to 20 g / L.

The silane coupling agent is preferably at least one selected from the group consisting of glyoxylpropylsilane, methacryloxypropyltrimethoxysilane, and glyoxylpropylmethyldimethoxysilane. When such a silane coupling agent is added, the degree of crosslinking is improved and a firm film can be obtained and the film adhesion can be improved, whereby the chromium elusion property in the film is reduced and the corrosion resistance is improved.

However, when the content of the silane coupling agent is less than 5 g / L, the crosslinking reaction is insufficient to improve the quality. When the content exceeds 20 g / L, curing of the solution is accelerated to gel the solution There is a problem that the solution stability is lowered.

In this case, in a conventional technique using a silane coupling agent in a chromate surface treatment solution, a silane coupling agent is generally applied in a post-process, but in such a case, the alcohol produced through the hydrolysis reaction of the silane coupling agent May act as a reducing agent to cause an additional reduction reaction. Accordingly, the color of the coating film may be changed by increasing the amount of the chromium 3 compound in the initial stage of the surface treatment solution preparation.

Therefore, in the case of the present invention, it is preferable that the addition of the silane coupling agent is not added in the post-process but is introduced into the surface treatment solution containing the silane coupling agent from the beginning in the chromium reduction reaction step .

For example, by introducing a silane coupling agent together with a phosphoric acid group component into an aqueous solution of chromic acid anhydride heated to 80 to 90 ° C, the resulting alcohol is terminated in a short time and used as a primary reducing agent, A surface treatment solution of the present invention can be prepared by adding a reducing agent so that a reduction reaction occurs at a later required reduction ratio.

Further, the surface-treated chromate solution of the present invention, which has been completed, can be neutralized with ammonia water or ammonium bicarbonate, if necessary.

According to another aspect of the present invention, there is provided a method of manufacturing an alloy-plated steel sheet surface-treated using the above-mentioned surface treatment solution. More specifically, the alloy-coated steel sheet of the present invention is a zinc- Mg alloy coated steel sheet.

The surface-treated Zn-Al-Mg alloy plated steel sheet of the present invention can be produced by: applying the above-mentioned surface treatment solution of the present invention onto a Zn-Al-Mg alloy plated steel sheet; Lt; RTI ID = 0.0 > 80 C < / RTI >

In the coating step, the specific coating method may be performed by any method such as a roll coating method, a dipping method, a spraying method, and the like, and is not particularly limited.

On the other hand, after the application is carried out, baking is carried out at 40 to 80 ° C. The surface treatment solution applied by the baking step is dried to form a surface treatment layer. When the temperature is lower than 40 ° C, drying is insufficient and it is difficult to obtain a desired quality. When the drying temperature exceeds 80 ° C Cracks may occur in the coating film formed as the surface treatment layer, or the soluble component may elute and the corrosion resistance may be deteriorated.

Further, it is preferable that the applying step is carried out at an adhesion amount of 20 to 100 mg / m ² . When the chromium adhesion amount is less than 20 mg / m ^2, the corrosion resistance of the coated steel sheet is deteriorated. When the chromium adhesion amount exceeds 100 mg / m ² , excessive coloring of the surface treatment solution causes yellowing, The quality may be deteriorated.

According to still another aspect of the present invention, there is provided a Zn-Al-Mg alloy-plated steel sheet produced and surface-treated by the above-described production method of the present invention.

The surface-treated Zn-Al-Mg alloy plated steel sheet of the present invention is more specifically a Zn-Al-Mg alloy plated steel sheet; And a surface treatment layer formed on at least one surface of the Zn-Al-Mg alloy plated steel sheet, wherein the surface treatment layer can be formed by the above-described components, contents and processes.

The surface treatment layer is preferably formed with an adhesion amount of 20 to 100 mg / m ² as described above. When the chromium adhesion amount is less than 20 mg / m ^2, the corrosion resistance of the coated steel sheet is deteriorated. When the chromium adhesion amount exceeds 100 mg / m ² , excessive coloring of the surface treatment solution causes yellowing, The quality may be deteriorated.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Example  One

Chromium nitrate was added to 500 ml of deionized water so that the nitric acid group (NO ^{3 -} ) component was 20 g, and anhydrous chromic acid was dissolved so that the total chromium component became 20 g. Phosphoric acid was added to the completely dissolved chromium solution so that the phosphoric acid group (PO ₄ ^{3 -} ) component was added to the solution, and 5 g / of glyoxypropyl silane was gradually added thereto. The resulting solution was heated at 80 to 90 캜 for 2 hours, After completion of the reduction reaction according to the decomposition reaction, methanol was added so that the reduction ratio became 0.8, and then the mixture was heated for 1 hour.

After the reaction was completed, the solution was cooled to 40 DEG C or lower, 20 g of colloidal silica was added, and deionized water was further added to make a total volume of 1 liter.

The chromate surface treatment solution prepared above was applied to an alloy coated steel sheet of zinc (Zn) -aluminum (Al) -magnesium (Mg) component. However, before applying the chromate surface treatment solution, an alkali degreasing agent (CL-N364S, Alkali-plated steel sheet was prepared by rinsing with alkaline cleaning using air-blowing (Air blowing).

The chromate surface treatment solution was coated on the surface of the chromium adhering amount and the PMT condition shown in Table 1 using a self-made roll coating type simulator.

Example  2 to 6 and Comparative Example  1 to 7

Chromate Surface treatment The same procedure as in Example 1 was carried out except that the components were added in the amounts shown in the following Table 1 based on the total volume of 1 L and the amounts of chromium and PMT in the amounts shown in Table 1 below were applied. Zn-Al-Mg alloy-plated steel sheet.

However, in the case of Comparative Example 4, the chromate surface treatment solution was prepared in such a manner that the silane coupling agent was added after the reduction reaction.

Total chromium (g / L) Component A Component B Component C Reduction ratio Colloidal silica pH Chrome adhesion PMT PO ₄ NO ₃ Silane coupling agent Example 1 20 A1 (10) B1 (20) C1 (5) 0.8 20 2.5 30 50 Example 2 30 A1 (10) B3 (30) C2 (10) 0.6 15 3 35 60 A2 (10) Example 3 15 A3 (5) B2 (10) C1 (5) 0.65 30 2 20 40 Example 4 40 A1 (5) B1 (10)
B3 (20) C3 (20) 0.85 10 2.5 60 80 A2 (10) A3 (10) Example 5 20 A1 (20) B1 (10) C1 (20) 0.7 30 3 80 50 Example 6 50 A2 (30) B1 (40) C1 (5) 0.9 10 3.5 40 60 Comparative Example 1 30 A1 (5) B3 (10) C1 (5) 0.3 10 2 80 50 Comparative Example 2 50 A1 (2) - C2 (10) 0.8 20 2.5 - - Comparative Example 3 40 A1 (80) B1 (20) C1 (5) 0.7 10 3 50 60 Comparative Example 4 50 A2 (5) B2 (10) C1 (20) * 0.5 10 2 60 80 Comparative Example 5 20 A1 (20) B3 (10) C2 (40) 0.6 30 2.5 40 50 Comparative Example 6 50 A1 (10) B1 (10) C1 (10) 0.5 20 2 150 60 Comparative Example 7 30 A2 (15) B2 (15) C3 (5) 0.8 15 5 30 40

* The silane coupling agent is prepared after completion of the reduction reaction.

Component A: phosphoric acid (A1), chromium phosphate (A2), ammonium phosphate (A3)

Component B: chromium (B1) nitrate, (B2) nitrate, (B3)

Component C: glyoxylpropylsilane (C1), methacryloxypropyltrimethoxysilane (C2), glyoxylpropylmethyldimethoxysilane (C3)

Experimental Example  1: Performance evaluation test

One. Surface appearance (Yellow degree)

The degree of yellowness was measured using a colorimeter, and the judgment was performed according to the following criteria.

⊚: The surface is uniform and beautiful, and the yellow color is 3.0 or less

○: The surface is uniform and beautiful, and the yellow color is 3.5 or less

?: The surface is uniform and beautiful, and the yellow color is 4.0 or less

X: Defects such as surface irregularity and stripes, or yellow color of 4.0 or higher

2. Corrosion resistance

A salt water spray test was conducted for 72 hours in accordance with JIS Z 2371, and the corrosion resistance was evaluated from the area of occurrence of white rust on the entire surface of the test piece according to the following criteria.

◎: white rust occurrence area 0%

○: Less than 5%

Δ: Less than 10% of white rust occurrence area

X: area of white rust occurrence 10% or more

3. Black degeneration

The black shade was stored for 120 hours in a high temperature and high humidity environment with a relative humidity of 90% or more and a temperature of 50 ° C, and then evaluated by using a colorimeter to measure the chromaticity of the surface of the steel sheet. same.

?: Color difference (? E) 3.0 or less

?: Color difference (? E) 3.5 or less

?: Color difference (? E) 4.0 or less

X: color difference (DELTA E) 4.0 or more

4. Solution stability

The surface treatment solution was left to stand at 50 ° C to observe the occurrence of precipitation in the solution, change in viscosity or swelling of the container due to the addition reaction of the solution.

○: No settling, change in viscosity or swelling of container

X: Sedimentation, viscosity change or container swelling occurred

Surface appearance (yellow degree) Corrosion resistance Black degeneration Solution stability Remarks Example 1 ◎ ◎ ◎ ○ Example 2 ◎ ◎ ◎ ○ Example 3 ◎ ◎ ◎ ○ Example 4 ◎ ◎ ◎ ○ Example 5 ◎ ◎ ◎ ○ Example 6 ◎ ◎ ◎ ○ Comparative Example 1 × ◎ △ ○ Yellow colored Comparative Example 2 - - - × Gelling Comparative Example 3 ◎ ◎ × ○ Defective black weathering Comparative Example 4 ◎ ◎ ◎ ○ Yellow color change Comparative Example 5 - - - × Gelling Comparative Example 6 × ○ △ ○ Yellowness Comparative Example 7 - × Gelling

As shown in Table 2, the surface treatment solution of the examples satisfying the composition, content range, and treatment conditions of the present invention was not colored in yellow, so that the surface appearance was not only excellent, but also had excellent corrosion resistance and black weather resistance, And it has excellent quality in terms of solution storage.

On the other hand, Comparative Example 1 was prepared with compositions falling outside the reduction ratio range of the present invention, and the appearance of the coating film was severely yellowed. Also, in Comparative Examples 2, 5, and 7 prepared outside the composition of the present invention, Or there is a problem in stability due to the gelation of the solution after the preparation.

Comparative Examples 3 and 6, which were out of the range of the solution composition or treatment conditions of the present invention, were poor in weathering resistance. Finally, in addition to the silane coupling agent, Comparative Example 4, which was different from the present invention, The yellowing degree of the coating film changed, and a coating film having a uniform appearance could not be formed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

Claims (10)

10 to 50 g / L of total chromium, 5 to 30 g / L of phosphate group (PO ₄ ^{3 -} ), 10 to 50 g / L of nitric acid group (NO ^{3 -} ), 5 to 30 g / L of colloidal silica and 5 to 20 g of silane coupling agent / L, which is excellent in corrosion resistance and black degeneration.
The surface treatment solution according to claim 1, wherein the reduction ratio (Cr ^{3 +} / total chromium) occupied by the chromium trivalent ions in the total chromium component is 0.5 to 0.9, which is excellent in corrosion resistance and black weather resistance.
The surface treatment solution according to claim 1, wherein the surface treatment solution has a pH of 2 to 4, and is excellent in corrosion resistance and black weather resistance.
The surface treatment solution according to claim 1, wherein the phosphoric acid group (PO ₄ ^3- ) is provided by at least one selected from the group consisting of chromium phosphate, orthophosphoric acid, ammonium phosphate monobasic and ammonium diphosphate, .
The surface treatment solution according to claim 1, wherein the nitrate group (NO ^{3 -} ) is provided by at least one selected from the group consisting of chromium nitrate, nitric acid, and sodium nitrate.
The method according to claim 1, wherein the silane coupling agent is at least one selected from the group consisting of glyoxylpropylsilane, methacryloxypropyltrimethoxysilane, and glyoxylpropylmethyldimethoxysilane, solution.
Applying a surface treatment solution according to any one of claims 1 to 6 on a Zn-Al-Mg alloy plated steel sheet; And
Lt; RTI ID = 0.0 > 80 C <
Wherein the surface-treated Zn-Al-Mg alloy-plated steel sheet comprises a surface-treated Zn-Al-Mg alloy plated steel sheet.
The method according to claim 7, wherein the applying step is performed at an adhesion amount of 20 to 100 mg / m ² .
Zn-Al-Mg alloy coated steel sheet; And
And a surface treatment layer formed on at least one surface of the Zn-Al-Mg alloy plated steel sheet,
The surface-treated layer is formed of the surface-treating solution according to any one of claims 1 to 6, and the surface-treated Zn-Al-Mg alloy-coated steel sheet.
The surface-treated Zn-Al-Mg alloy coated steel sheet according to claim 9, wherein the surface treatment layer is formed with an adhesion amount of 20 to 100 mg / m ² .