KR20210077527A - CONVERSION COATING COMPOSITION FOR Zn-Al-Mg ALLOY PLATED STEEL SHEET AND Zn-Al-Mg ALLOY PLATED STEEL SHEET - Google Patents

Abstract

An object of the present invention is to provide a chemical conversion treatment composition and a chemical conversion treatment method for preventing surface blackening defects occurring in Zn-Al-Mg alloy plated steel sheets and chromate-treated steel sheets. According to the present invention, provided is a composition for chemical conversion treatment of a Zn-Al-Mg alloy plated steel sheet includes, based on the total weight of the composition for chemical conversion, 0.2 to 20 wt% of an amine salt of phosphoric acid derived from an alkyl phosphate acid and an alkyl amine; 0.1 to 10 wt% of zinc phosphate; 0.1 to 10 wt% of a silicate compound; and the remainder.

Description

Composition for chemical conversion treatment of Zn-Al-Mg alloy coated steel sheet and Zn-Al-Mg alloy coated steel sheet

The present invention relates to a composition for chemical conversion treatment of a Zn-Al-Mg alloy plated steel sheet and a Zn-Al-Mg alloy plated steel sheet.

In general, zinc and zinc-based alloy plating are performed to prevent or reduce corrosion of metals. However, as the amount of zinc used in nature increases, the price of zinc metal rises, and zinc depletion becomes a problem. As a countermeasure against this, a method of reducing the plating amount by performing plating with excellent corrosion resistance by adding alloying elements is being devised. As a part of this, alloy plating in which aluminum and magnesium are added to zinc has been developed and used mainly for construction, but recently it is being used for home appliances and automobiles as well. In particular, in order to protect the surface of Zn-Al-Mg alloy plated steel sheet and to facilitate corrosion resistance and machining of parts, chromate coating treatment with excellent corrosion resistance is often applied.

However, the biggest problem with these alloy-plated steel sheets and chromate-treated steel sheets is the blackening that occurs on the surface of the plating layer during long-term storage at customers, condensation due to temperature difference, or storage in a coiled state or stacked steel sheets in a high-temperature and high-humidity environment. . This blackening phenomenon is a phenomenon that generally occurs in a plating layer containing magnesium metal and is due to the unsafe oxidation of zinc metal by preferential oxidation of magnesium metal concentrated in the surface layer. Blackening is an early stage of corrosion of metals and tends to be easily completely oxidized to white rust when exposed to air. In particular, the chromate treatment solution is a strong acidic aqueous solution with a pH of 1 to 1.5, and the chromate product for building materials mainly has a steel sheet thickness of 1.0 mm or more and cooling is not easy due to latent heat after drying. have. Therefore, in order to solve this problem, a technique for spraying Co(III) salt in the cooling process of the Zn-4.0%Al-0.1%Mg plating layer (ISIJ, 1990, p383-390) is proposed, and recently Zn -The technology of treating an aqueous solution of Mg, Al, and Zn salts on the surface of an Al-Mg alloy plated steel sheet and then treating an aqueous solution of zinc chloride (Korean Patent 10-1638307) is proposed, but it is complicated in terms of equipment and easy to apply There is a problem that it doesn't.

An object of the present invention is to provide a chemical conversion composition and a chemical conversion treatment method for preventing surface blackening defects occurring in Zn-Al-Mg alloy plated steel sheets and chromate-treated steel sheets.

According to one aspect of the present invention, based on the total weight of the chemical conversion composition, 0.2 to 20 wt% of an amine salt of phosphoric acid derived from an alkyl phosphate acid and an alkyl amine; 0.1 to 10% by weight of zinc phosphate; 0.1 to 10% by weight of a silicate compound; And a composition for chemical conversion treatment of a Zn-Al-Mg alloy plated steel sheet containing water is provided.

According to another aspect of the present invention, there is provided a Zn-Al-Mg alloy plated steel sheet and a chemical conversion treatment coating layer on at least one surface of the coated steel sheet, wherein the coating layer is a converted steel sheet formed by the chemical conversion composition. .

The chemical conversion treatment composition according to the present invention is adsorbed on the surface of a Zn-Al-Mg alloy plated steel sheet to prevent blackening due to a high-temperature, high-humidity environment or generation of dew condensation during lamination of coils or steel sheets.

1 shows (a) a structure of a coating film after chemical conversion treatment according to an embodiment of the present invention, and (b) a structure of a coating film treated with chromate on a chemically treated steel sheet.
Figure 2 shows the process of chemical conversion treatment and chromate treatment according to an embodiment of the present invention on a Zn-Al-Mg alloy plated steel sheet.

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

Typically, the chromate coating solution is a strongly acidic solution having a pH of 1.0 to 1.5. Therefore, during immersion, spraying, or roll coating, the surface of the plating layer of the steel sheet is etched and incomplete Cr-oxide or hydroxide is precipitated to form a coating layer. In particular, the coating layer is dried at a temperature of 100° C. or less due to the fact that the drying temperature for curing the coating layer cannot be increased due to the facility restrictions of the hot dip plating line of the steel manufacturer and the cooling of the steel sheet after drying is difficult. Due to this, a problem of surface blackening occurs when coils or laminated steel sheets are stored for a long time. According to previous studies, it is known that blackening is caused by long-term exposure of galvanized steel sheets to high-temperature and high-humidity environments or an atmosphere with poor oxygen supply, or due to surface impurities or mechanical deformation. It is known that such blackening occurs easily in a galvanized layer to which aluminum or magnesium is added, and is accelerated by incomplete oxidation when treated with a phosphoric acid compound or chromate on the surface of the plating layer.

As a method to solve the above problems, as shown in FIG. 1 , when an organic-inorganic corrosion-resistant phosphoric acid amine salt compound is impregnated into the roughness formation part of the plating layer surface, excessive surface etching by a solution with high acidity is prevented, and the roughness part or the plating layer Corrosion can be prevented by preventing the penetration of acid into the grain boundary.

Hereinafter, the present invention will be described in detail.

According to an embodiment of the present invention, there is provided a composition for chemical conversion treatment of a Zn-Al-Mg alloy plated steel sheet comprising an alkyl phosphate acid and an amine salt of phosphoric acid derived from an alkyl amine, zinc phosphate, a silicate compound, and the remainder.

The phosphoric acid amine salt may be a compound in which an alkyl phosphate acid and an alkyl amine form an ionic bond. In the present invention, the phosphoric acid amine salt may be included in an amount of 0.1 to 20% by weight based on the total weight of the composition for chemical conversion. If the content of the phosphoric acid amine salt is less than 0.1% by weight, the blackening resistance effect of the steel sheet is not properly exhibited, and if it exceeds 20% by weight, there is a problem in that chromate coating is difficult in the subsequent chromate coating step.

The alkyl phosphate acid constituting the phosphoric acid amine salt may be a compound represented by the following formula (1).

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently a linear alkyl group having 3 to 15 carbon atoms, a branched alkyl group having 5 to 15 carbon atoms, and R ₁ and R ₂ are each independently a hydroxyl group, an ether group, an ester group Or it may be substituted with an epoxy group.

Preferred alkyl phosphate acids that can be used in the present invention are 2-ethylhexyl phosphate, Iso-nonanol phosphate, Octyl ethoxylate phosphate, decyl ethoxylate phosphate ( Decyl ethoxylate phosphate, 2-ethylhexyl ethoxylate phosphate, Decyl alcohol ethoxylate phosphate, Iso-tridecanol ethoxylate phosphate, Tergitol 15-S-9 phosphate, Cetyl alcohol ethoxylate phosphate, Stearyl alcohol ethoxylate phosphate, Octyl alcohol ethoxylate It may be one or more selected from the group consisting of phosphate (Octyl alcohol ethoxylate phosphate), oleyl alcohol ethoxylate phosphate (Oleyl alcohol ethoxylate phosphate), and alkyl phenol ethoxylate phosphate (Alkyl phenol ethoxylate phosphate), but is not limited thereto.

The alkyl amine constituting the phosphoric acid amine salt may be a compound represented by the following Chemical Formulas 2 to 8.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

In Formulas 2 to 8, R ₃ , R ₄ and R ₅ are each independently hydrogen or methyl, R ₆ is each independently a linear or branched alkyl group having 3 to 5 carbon atoms substituted with a hydroxyl group, and n is 2 or an integer of 3.

Preferred alkyl amines usable in the present invention include bis(N-dimethylaminopropyl)amine, bis(N-dimethylaminoethyl)methylamine, and bis (N-dimethylaminopropyl) methylamine (Bis (N-dimethylaminopropyl) methylamine), bis (N-aminoethyl) methylamine (Bis (N-aminoethyl) methylamine), bis (N-aminopropyl) methylamine (Bis ( N-aminopropyl) methylamine), bis (dimethylaminoethyl) ether (Bis (dimethylaminoethyl) ether), bis (dimethylaminopropyl) ether (Bis (dimethylaminopropyl) ether), bis (aminoethyl) ether (Bis (aminoethyl) ether) , bis (aminopropyl) ether (Bis (aminopropyl) ether), bis (3-dimethylaminopropyl) isopropanolamine (Bis (3-dimethylaminopropyl) isopropanolamine), 3-dimethylaminopropyl diisopropanolamine (3-dimethylaminopropyldiisopropanolamine), 2 -(2-dimethylaminoethoxy)ethanol (2-(2-dimethylaminoethoxy)ethanol), 2-(2-dimethylaminoethoxyethyl)methylaminoethanol (2-(2-dimethylaminoethoxyethyl)methylaminoethanol), 2-(2 -Dimethylporinoethyl)ether (2-(2-dimethylpholinoethyl)ether) and 2-(2-dimethylaminoethyl)methylaminoethanol (2-(2-dimethylaminoethyl)methylaminoethanol) may be at least one selected from the group consisting of It is not limited to this.

The anion of the alkyl phosphate acid and the cation of the alkyl amine form a phosphoric acid amine salt by ionic bonding, and may be included in an amount of 0.1 to 10% by weight, respectively, based on the total weight of the chemical conversion composition.

In the chemical conversion composition according to an embodiment of the present invention, zinc phosphate forms phosphoric acid crystals on the surface of the steel sheet when the composition is applied, thereby providing additional corrosion resistance and blackening resistance. The zinc phosphate may be added in an amount of 0.1 to 10 wt% based on the total weight of the chemical conversion composition. If the content of zinc phosphate is less than 0.1% by weight, the corrosion resistance effect is insignificant, and if it exceeds 10% by weight, there is a problem that the chromate coating layer on the surface is brittle.

In the composition for chemical conversion according to an embodiment of the present invention, the silicate compound is deposited on the fine roughness portion of the surface of the steel sheet when the composition is applied to provide additional corrosion resistance. The higher the content of the silicate compound, the better the corrosion resistance and adhesion of the coating film, but there is a limit in improving the corrosion resistance and adhesion of the coating film even when added in a certain amount or more. Therefore, the silicate compound is preferably added in an amount of 0.1 to 10% by weight based on the total weight of the chemical conversion composition.

Examples of the silicate compound that can be used in the present invention include lithium silicate, sodium silicate, potassium silicate, and the like, and preferably a lithium silicate compound.

In addition, the composition for chemical conversion according to an embodiment of the present invention may further include a phosphoric acid compound to adjust the acidity of the composition. The phosphoric acid compound is added so that the pH of the composition is 3-5.

According to another aspect of the present invention, the chemical conversion-treated Zn-Al-Mg alloy plated steel sheet is dried after alkali degreasing, pickling and washing of the cold-rolled steel sheet, hot-dip plating the zinc alloy and then cooling, chemical conversion treatment and drying It can be prepared through a step of drying, chromate treatment and then drying. At this time, the chemical conversion composition and the chromate composition are sprayed and then treated by squeezing or roll coating process, and drying is performed by hot air, infrared or induction heating curing method.

In the step of hot-dip plating the zinc alloy on the cold-rolled steel sheet, the zinc alloy may be in the form of Zn-xAl-yMg. In this case, it is preferable that x is 0.5 to 15 and y is 0.5 to 10.

In the step of drying after chemical conversion, the chemical composition is preferably applied at 10 to 100 mg/m ² and dried at a temperature of 60 to 120° C.

In addition, in the drying step after the chromate treatment, preferably 10 to 300 mg/m ² based on the weight of the chromium element may be applied and dried at a temperature of 80 to 120° C.

Example

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for the understanding of the present invention, but do not limit the present invention.

1. Examples

(1) Preparation of composition for chemical conversion treatment

Dissolve isononanol phosphate, an amine salt of phosphate made from bis(N-aminoethyl)methylamine, zinc phosphate hydrate (Duksan Chemical) in 1L of pure water, and add a lithium silicate compound and phosphoric acid to prepare a chemical conversion composition having a pH of 3.5 prepared. Each composition of the chemical conversion composition is shown in Table 1 below.

(2) Manufacture of chemically treated steel sheet

The composition for chemical conversion prepared above ^{was applied to a Zn-xAl-yMg plated steel sheet having a coating weight of 50 g/m 2} and x and y values in Table 1 below, and then dried in a hot air heating furnace at 80°C. The chromate (III) composition was applied to the chemically treated steel sheet by roll coating, and then dried in a hot air furnace at 80°C. The chromate (III) composition has a solid content of 12% by weight and is a water-soluble Cr(III) composition (Norcoil Coating Co., Ltd.) composed of chromium phosphate, chromium nitrate, a silane compound, and a small amount of urethane bind and wetting agent, and has a pH of 1.2. .

Zn-xAl-yMg coated steel sheet Composition for chemical conversion treatment (g/L) phosphate amine salt
adhesion amount
(g/m ² ) x y phosphate amine salt zinc phosphate silicate compound Example 1-1 1.5 1.5 5 5 2 10±2 Example 1-2 4 Examples 1-3 10 2 16±2 Examples 1-4 4 Examples 1-5 10 5 2 16±2 Examples 1-6 4 Examples 1-7 10 2 20±2 Examples 1-8 4 Examples 1-9 15 5 2 20±2 Examples 1-10 4 Examples 1-11 10 2 25±2 Examples 1-12 4 Examples 1-13 20 5 2 25±2 Examples 1-14 4 Examples 1-15 10 2 30±2 Examples 1-16 4 Example 2-1 2.8 3.0 5 5 2 10±2 Example 2-2 4 Example 2-3 10 2 16±2 Example 2-4 4 Example 2-5 10 5 2 16±2 Example 2-6 4 Example 2-7 10 2 20±2 Examples 2-8 4 Examples 2-9 15 5 2 20±2 Example 2-10 4 Example 2-11 10 2 25±2 Example 2-12 4 Examples 2-13 20 5 2 25±2 Examples 2-14 4 Examples 2-15 10 2 30±2 Examples 2-16 4 Example 3-1 4.0 1.5 5 5 2 10±2 Example 3-2 4 Example 3-3 10 2 16±2 Example 3-4 4 Example 3-5 10 5 2 16±2 Example 3-6 4 Example 3-7 10 2 20±2 Example 3-8 4 Example 3-9 15 5 2 20±2 Example 3-10 4 Example 3-11 10 2 25±2 Example 3-12 4 Example 3-13 20 5 2 25±2 Example 3-14 4 Example 3-15 10 2 30±2 Examples 3-16 4 Example 4-1 12.0 4.0 5 5 2 10±2 Example 4-2 4 Example 4-3 10 2 16±2 Example 4-4 4 Example 4-5 10 5 2 16±2 Example 4-6 4 Example 4-7 10 2 20±2 Examples 4-8 4 Examples 4-9 15 5 2 20±2 Example 4-10 4 Examples 4-11 10 2 25±2 Example 4-12 4 Examples 4-13 20 5 2 25±2 Examples 4-14 4 Examples 4-15 10 2 30±2 Examples 4-16 4

2. Comparative Example

As shown in Table 2 below, chromate (III) and chromate (VI) compositions were respectively applied by roll coating to a Zn-xAl-yMg plated steel sheet having a coating amount of 50 g/m ^{2 and x and y values of Table 2 below, and then at 80 ° C.} A chromate-treated plated steel sheet was prepared by drying in a hot air heating furnace of

Zn-xAl-yMg coated steel sheet Composition for chemical conversion treatment (g/L) phosphate amine salt
adhesion amount
(g/m ² ) x y phosphate amine salt zinc phosphate silicate compound Comparative Example 1 1.5 1.5 - - - - Comparative Example 2 2.8 3.0 - - - - Comparative Example 3 4.0 1.5 - - - - Comparative Example 4 12.0 4.0 - - - -

3. Evaluation of Zn-Al-Mg alloy coated steel sheet

After evaluating the items of (1) to (5) below, the evaluation results are shown in Table 3.

(1) [Cr] adhesion amount

After dissolving the plating layer by adding 30 ml of a 3% standard hydrochloric acid solution to the surface of the steel sheet, the [Cr] element was measured by ICP quantitative analysis.

(2) blackening resistance

A coated steel sheet was prepared in a size of 70 mm × 70 mm (width × length) and left for 120 hours under constant temperature and humidity (65° C., 95% relative humidity conditions) conditions, and the average color difference (ΔE) was measured compared to the original plate. .

<Evaluation criteria>

◎: When the average color difference (ΔE) is less than 5.0

○: When the average color difference (ΔE) is 5.0 or more and less than 10.0

Δ: When the average color difference (ΔE) is 10.0 or more and less than 15

×: When the average color difference (ΔE) is 15 or more

(3) Corrosion resistance

For corrosion resistance of the flat part, a steel plate is prepared in a size of 70 mm × 150 mm (width × length), and salt water having a salt water concentration of 5% and a temperature of 35° C. is evenly sprayed to ^{the specimen at a spray pressure of 1 kg/cm 2} After that, the time until white rust of 5% area occurred on the surface of the steel sheet was measured.

In addition, the corrosion resistance of the machining part was evaluated in the same manner as above after processing the specimen by 7 mm of Eriksen.

<Evaluation criteria>

◎: In the case of 168 hours or more of the flat plate

○: When the flat part is 120 hours or more and less than 168 hours

△: In the case of 48 hours or more and less than 120 hours of the flat plate

×: When the flat plate is less than 48 hours

(4) alkali resistance

A specimen was prepared in the size of a steel plate of 150 mm × 70 mm (width × length). Dissolve 20 g of DP FC-L4460A and 10 g of DP FC-L4460B in 1 L of strong alkaline degreasing agent (manufacturer, Daehan Parkerizing Co., Ltd.), and then immerse the specimen at a temperature of 60 ° C. for 2 minutes. ) was measured.

<Evaluation criteria>

◎: When the average color difference (ΔE) is less than 1.0

○: When the average color difference (ΔE) is 1.0 or more and less than 1.5

Δ: When the average color difference (ΔE) is 1.5 or more and less than 2.0

×: When the average color difference (ΔE) is 2.0 or more

(5) crude oil invasiveness

The steel sheet was immersed in 10% crude oil for 24 hours, left to stand, and the color difference was measured and evaluated.

<Evaluation criteria>

◎: When the average color difference (ΔE) is less than 0.5

○: When the average color difference (ΔE) is 0.5 or more and less than 1.0

△: When the average color difference (ΔE) is 1.0 or more and less than 1.5

×: When the average color difference (ΔE) is 1.5 or more

[Cr] adhesion amount
(mg/m ² ) quality characteristics blackening resistance corrosion resistance alkali resistance crude oil intrusion Example 1-1 30±2 ◎ ◎ ◎ ◎ Example 1-2 ◎ ◎ ◎ ◎ Examples 1-3 ◎ ◎ ◎ ◎ Examples 1-4 ◎ ◎ ◎ ◎ Examples 1-5 ◎ ◎ ◎ ◎ Examples 1-6 ◎ ◎ ◎ ◎ Examples 1-7 ◎ ◎ ◎ ◎ Examples 1-8 ◎ ◎ ◎ ◎ Examples 1-9 ◎ ◎ ◎ ◎ Examples 1-10 ◎ ◎ ◎ ◎ Examples 1-11 ◎ ◎ ◎ ◎ Examples 1-12 ◎ ◎ ◎ ◎ Examples 1-13 ◎ ◎ ◎ ◎ Examples 1-14 ◎ ◎ ◎ ◎ Examples 1-15 ◎ ◎ ◎ ◎ Examples 1-16 ◎ ◎ ◎ ◎ Example 2-1 ◎ ◎ ◎ ◎ Example 2-2 ◎ ◎ ◎ ◎ Example 2-3 ◎ ◎ ◎ ◎ Example 2-4 ◎ ◎ ◎ ◎ Example 2-5 ◎ ◎ ◎ ◎ Example 2-6 ◎ ◎ ◎ ◎ Example 2-7 ◎ ◎ ◎ ◎ Examples 2-8 ◎ ◎ ◎ ◎ Examples 2-9 ◎ ◎ ◎ ◎ Example 2-10 ◎ ◎ ◎ ◎ Example 2-11 ◎ ◎ ◎ ◎ Example 2-12 ◎ ◎ ◎ ◎ Examples 2-13 ◎ ◎ ◎ ◎ Examples 2-14 ◎ ◎ ◎ ◎ Examples 2-15 ◎ ◎ ◎ ◎ Examples 2-16 ◎ ◎ ◎ ◎ Example 3-1 ◎ ◎ ◎ ◎ Example 3-2 ◎ ◎ ◎ ◎ Example 3-3 ◎ ◎ ◎ ◎ Example 3-4 ◎ ◎ ◎ ◎ Example 3-5 ◎ ◎ ◎ ◎ Example 3-6 ◎ ◎ ◎ ◎ Example 3-7 ◎ ◎ ◎ ◎ Example 3-8 ◎ ◎ ◎ ◎ Example 3-9 ◎ ◎ ◎ ◎ Example 3-10 ◎ ◎ ◎ ◎ Example 3-11 ◎ ◎ ◎ ◎ Example 3-12 ◎ ◎ ◎ ◎ Example 3-13 ◎ ◎ ◎ ◎ Example 3-14 ◎ ◎ ◎ ◎ Example 3-15 ◎ ◎ ◎ ◎ Examples 3-16 ◎ ◎ ◎ ◎ Example 4-1 ◎ ◎ ◎ ◎ Example 4-2 ◎ ◎ ◎ ◎ Example 4-3 ◎ ◎ ◎ ◎ Example 4-4 ◎ ◎ ◎ ◎ Example 4-5 ◎ ◎ ◎ ◎ Example 4-6 ◎ ◎ ◎ ◎ Example 4-7 ◎ ◎ ◎ ◎ Examples 4-8 ◎ ◎ ◎ ◎ Examples 4-9 ◎ ◎ ◎ ◎ Example 4-10 ◎ ◎ ◎ ◎ Examples 4-11 ◎ ◎ ◎ ◎ Example 4-12 ◎ ◎ ◎ ◎ Examples 4-13 ◎ ◎ ◎ ◎ Examples 4-14 ◎ ◎ ◎ ◎ Examples 4-15 ◎ ◎ ◎ ◎ Examples 4-16 ◎ ◎ ◎ ◎ Comparative Example 1 30 △ ◎ ◎ ◎ Comparative Example 2 △ ◎ ◎ ◎ Comparative Example 3 △ ◎ ◎ ◎ Comparative Example 4 △ ◎ ◎ ◎

As in Comparative Examples 1 to 4, it can be seen that the blackening resistance is lowered when the chromate treatment is performed on the plated steel sheet without using the chemical conversion composition.

Claims (9)

Based on the total weight of the chemical conversion composition,
0.2 to 20% by weight of an amine salt of phosphoric acid derived from an alkyl phosphate acid and an alkyl amine;
0.1 to 10% by weight of zinc phosphate;
0.1 to 10% by weight of a silicate compound; and
A composition for chemical conversion treatment of Zn-Al-Mg alloy plated steel sheet containing the remainder.
According to claim 1,
Alkyl phosphate is a compound represented by the following formula (1) Zn-Al-Mg alloy plated steel sheet chemical conversion composition.
[Formula 1]

(In Formula 1, R ₁ and R ₂ are each independently a linear alkyl group having 3 to 15 carbon atoms, a branched alkyl group having 5 to 15 carbon atoms, and R ₁ and R ₂ are each independently a hydroxyl group, an ether group, an ester It may be substituted with a group or an epoxy group.)
According to claim 1,
Alkyl amine is a Zn-Al-Mg alloy plated steel sheet chemical conversion composition which is a compound represented by the following Chemical Formulas 2 to 8.
[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

(In Formulas 2 to 8,
R ₃ , R ₄ and R ₅ are each independently hydrogen or methyl,
R ₆ is each independently a linear or branched alkyl group having 3 to 5 carbon atoms substituted with a hydroxyl group,
n is an integer of 2 or 3.)
According to claim 1,
Alkyl phosphates are 2-ethylhexyl phosphate, iso-nonanol phosphate, octyl ethoxylate phosphate, decyl ethoxylate phosphate, 2- Ethylhexyl ethoxylate phosphate (2-ethylhexyl ethoxylate phosphate), Decyl alcohol ethoxylate phosphate (Decyl alcohol ethoxylate phosphate), Iso-tridecanol ethoxylate phosphate (Iso-tridecanol ethoxylate phosphate), Tergitol 15-S-9 Phosphate (Tergitol 15-S-9 phosphate), Cetyl alcohol ethoxylate phosphate (Stearyl alcohol ethoxylate phosphate), Octyl alcohol ethoxylate phosphate (Octyl alcohol ethoxylate phosphate) , oleyl alcohol ethoxylate phosphate (Oleyl alcohol ethoxylate phosphate) and alkyl phenol ethoxylate phosphate (Alkyl phenol ethoxylate phosphate) at least one selected from the group consisting of Zn-Al-Mg alloy plated steel sheet chemical conversion composition.
According to claim 1,
Alkyl amine is bis(N-dimethylaminopropyl)amine (Bis(N-dimethylaminopropyl)amine), bis(N-dimethylaminoethyl)methylamine (Bis(N-dimethylaminoethyl)methylamine), bis(N-dimethylaminopropyl) Methylamine (Bis (N-dimethylaminopropyl) methylamine), bis (N-aminoethyl) methylamine (Bis (N-aminoethyl) methylamine), bis (N-aminopropyl) methylamine (Bis (N-aminopropyl) methylamine), Bis(dimethylaminoethyl)ether, Bis(dimethylaminopropyl)ether, Bis(aminoethyl)ether, Bis(aminopropyl)ether (Bis (aminopropyl) ether), bis (3-dimethylaminopropyl) isopropanolamine (Bis (3-dimethylaminopropyl) isopropanolamine), 3-dimethylaminopropyl diisopropanolamine (3-dimethylaminopropyldiisopropanolamine), 2- (2-dimethylamino Toxy)ethanol (2-(2-dimethylaminoethoxy)ethanol), 2-(2-dimethylaminoethoxyethyl)methylaminoethanol (2-(2-dimethylaminoethoxyethyl)methylaminoethanol), 2-(2-dimethylporinoethyl)ether Chemical conversion of at least one Zn-Al-Mg alloy coated steel sheet selected from the group consisting of (2-(2-dimethylpholinoethyl)ether) and 2-(2-dimethylaminoethyl)methylaminoethanol (2-(2-dimethylaminoethyl)methylaminoethanol) treatment composition.
According to claim 1,
The silicate compound is at least one selected from the group consisting of lithium silicate, sodium silicate and potassium silicate. A composition for chemical conversion of a Zn-Al-Mg alloy plated steel sheet.
The method of claim 1,
A composition for chemical conversion treatment of a Zn-Al-Mg alloy plated steel sheet further comprising a phosphoric acid compound so that the pH of the composition is 3 to 5.
Zn-Al-Mg alloy plated steel sheet and
Containing a chemical conversion coating layer on at least one surface of the plated steel sheet,
The coating layer is 10 to 100mg / m ^{2 A} chemically treated steel sheet that is attached.
9. The method of claim 8,
A converted steel sheet in which a chromate coating layer is present on a chemical conversion coating layer.

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