SURFACE TREATMENT COMPOSITION FOR TERNARY HOT-DIP GALVANNEALED STEEL SHEET, SURFACE-TREATED TERNARY HOT-DIP GALVANNEALED STEEL SHEET USING SAME, AND PREPARATION METHOD THEREOF

Abstract

The present disclosure is to provide a surface treatment composition that may impart excellent corrosion resistance, blackening resistance, and alkali resistance, and an intrinsic surface color property to a ternary hot-dip galvannealed steel sheet. The present disclosure provides a surface treatment composition containing: based on 100 wt% of a solid content of the composition, 70 to 90 wt% of a resin mixture including a high molecular weight polysilicon-modified polyurethane main resin, a low molecular weight polysilicon-modified polyurethane auxiliary resin, and an acrylic urethane auxiliary resin; 5 to 25 wt% of a melamine-based curing agent; 0.5 to 10 wt% of an inorganic additive; 0.5 to 10 wt% of a silane coupling agent; 0.1 to 2 wt% of an adhesion promoter; 0.1 to 2 wt% of a coloring pigment; and 0.1 to 1 wt% of a pigment stabilizer.

Claims

1. A surface treatment composition comprising: based on 100 wt% of a solid content of the composition, 70 to 90 wt% of a resin mixture including a high molecular weight polysilicon-modified polyurethane main resin, a low molecular weight polysilicon-modified polyurethane auxiliary resin, and an acrylic urethane auxiliary resin; 5 to 25 wt% of a melamine-based curing agent; 0.5 to 10 wt% of an inorganic additive; 0.5 to 10 wt% of a silane coupling agent; 0.1 to 2 wt% of an adhesion promoter; 0.1 to 2 wt% of a coloring pigment; and 0.1 to 1 wt% of a pigment stabilizer.

2. The surface treatment composition of claim 1, wherein the high molecular weight polysilicon-modified polyurethane main resin, the low molecular weight polysilicon-modified polyurethane auxiliary resin, and the acrylic urethane auxiliary resin are mixed at a weight ratio of 1:4.5:4.5 to 9:0.5:0.5.

3. The surface treatment composition of claim 1, wherein the high molecular weight polysilicon-modified polyurethane main resin has a glass transition temperature (Tg) of -20° C. to -10° C. and a weight average molecular weight (Mw) of 100,000 to 200,000.

4. The surface treatment composition of claim 1, wherein the low molecular weight polysilicon-modified polyurethane auxiliary resin has a glass transition temperature (Tg) of -30° C. to -20° C. and a weight average molecular weight (Mw) of 30,000 to 70,000.

5. The surface treatment composition of claim 1, wherein the acrylic urethane auxiliary resin is obtained by copolymerizing an acrylic resin having one or more structural units selected from the group consisting of methyl methacrylate (MMA) and butyl acrylate (BA) and a polycarbonate-based urethane resin.

6. The surface treatment composition of claim 5, wherein the polycarbonate-based urethane resin has a glass transition temperature (Tg) of 50° C. to 70° C. and a weight average molecular weight (Mw) of 80,000 to 120,000.

7. The surface treatment composition of claim 1, wherein the melamine-based curing agent includes one or more functional groups selected from the group consisting of a methoxymethyl group, a methylol group, and an imino group, and the functional group crosslinks a resin containing a carboxyl group.

8. The surface treatment composition of claim 1, wherein the inorganic additive includes one or more selected from the group consisting of silica sol, alumina sol, titania sol, and zirconia sol.

9. The surface treatment composition of claim 1, wherein the silane coupling agent includes one or more selected from the group consisting of vinylmethoxysilane, vinyltrimethoxysilane, vinylepoxysilane, vinyltriepoxysilane, methyltrimethoxysilane, tetraethyl orthosilicate, tetramethyl orthosilicate, 3-aminopropyltriepoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-(triepoxysilane)-1-propanamine, N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltriethoxysilane, and N-[2-(vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilane.

10. The surface treatment composition of claim 9, wherein the silane coupling agent is hydrolyzed by one or more acids selected from the group consisting of formic acid, acetic acid, phosphoric acid, hydrochloric acid, and nitric acid.

11. The surface treatment composition of claim 1, wherein the adhesion promoter is one or more selected from the group consisting of ester phosphate and ammonium phosphate.

12. The surface treatment composition of claim 1, wherein the coloring pigment includes one or more selected from the group consisting of one or more inorganic pigments selected from the group consisting of titanium, lead, iron, copper, and chromium; and an azo-based organic pigment.

13. The surface treatment composition of claim 1, wherein the pigment stabilizer is a carboxylic polymer.

14. The surface treatment composition of claim 1, further comprising a solvent, wherein a solid content of the solvent is 20 to 40 wt% based on a total weight of the surface treatment composition, and the solvent is a balance of a solvent.

15. The surface treatment composition of claim 14, wherein the solvent contains 3 to 10 wt% of alcohol based on a total weight of the solvent and a balance of water.

16. A surface-treated ternary hot-dip galvannealed steel sheet comprising: a steel sheet; a ternary hot-dip galvannealed layer formed on at least one surface of the steel sheet; and a surface-treated coating layer formed on the ternary hot-dip galvannealed layer, wherein the surface-treated coating layer is formed using the surface treatment composition of claim 1.

17. The surface-treated tertiary hot-dip galvannealed steel sheet of claim 16, wherein the ternary hot-dip galvannealed layer includes an Al-rich layer formed at an interface, and an area ratio occupied by the Al-rich layer is 70% to 100%.

18. The surface-treated tertiary hot-dip galvannealed steel sheet of claim 16, wherein the ternary hot-dip galvannealed layer contains 0.2 to 15 wt% of Al, 0.5 to 3.5 wt% of Mg, and a balance of Zn and inevitable impurities.

19. The surface-treated tertiary hot-dip galvannealed steel sheet of claim 16, wherein a thickness of the surface-treated coating layer is 1 .Math.m to 10 .Math.m.

20. A method for manufacturing a surface-treated ternary hot-dip galvannealed steel sheet, the method comprising: coating the surface treatment composition of claim 1 on a ternary hot-dip galvannealed steel sheet in which a ternary hot-dip galvannealed layer is formed; and drying the coated surface treatment composition to form a surface-treated coating layer.

21. (canceled)

Description

MODE FOR INVENTION

Examples

Preparation of Test Specimen

[0067] A ternary hot-dip galvannealed steel sheet (coating weight on one surface: 0.5 to 2.0 g/m.sup.2) including a ternary hot-dip galvannealed layer containing, by wt%, 1.5% of Mg, 1.5% of Al, and a balance of Zn was cut into a size of 7 cm × 15 cm (width × length), oil was removed from the ternary hot-dip galvannealed steel sheet, each of prepared compositions was applied to the ternary hot-dip galvannealed steel sheet using a bar coater. Subsequently, curing was performed under a condition of a peak metal temperature (PMT) of 180 ± 20° C., thereby preparing a test specimen.

Test and Evaluation Method

[0068] The method and criteria for evaluating the physical properties of the surface-treated steel sheet in the present Examples are as follows.

<Flat Sheet Corrosion Resistance>

[0069] The specimen was treated in accordance with the method specified in ASTM B117, and then, a rate of occurrence of white rust in the steel sheet over time was measured. In this case, the evaluation criteria are as follows.

[0070] ⊚: The time taken for white rust to be generated was 144 hours or longer.

[0071] ◯: The time taken for white rust to be generated was 96 hours or longer and shorter than 144 hours.

[0072] Δ: The time taken for white rust to be generated was 55 hours or longer and shorter than 96 hours.

[0073] X: The time taken for white rust to be generated was shorter than 55 hours.

<Processed Part Corrosion Resistance>

[0074] The specimen was pushed up to a height of 6 mm using an Erichsen tester, and a degree of generation of white rust was measured when 24 hours have elapsed. In this case, the evaluation criteria are as follows. [0075] ⊚: Less than 5% of white rust generation area after 48 hours have elapsed [0076] Δ: 5% or more and less than 7% of white rust generation area after 48 hours have elapsed [0077] X: 7% or more of white rust generation area after 48 hours have elapsed

<Blackening Resistance>

[0078] The specimen was left in a thermo-hygrostat maintained at 50° C. and a relative humidity of 95% for 120 hours, and a color change (color difference: ΔE) of the specimen before and after the test was observed. In this case, the evaluation criteria are as follows. [0079] ⊚: ΔE ≤ 2 [0080] ◯: 2 < ΔE ≤ 3 [0081] Δ: 3 < ΔE ≤ 4 [0082] X: ΔE > 4

<Alkali Resistance>

[0083] The specimen was immersed in an alkali degreasing solution at 60° C. for 2 minutes, the immersed specimen was subjected to washing with water, and air blowing, and then a pre-post difference in color (ΔE) was measured. As the alkali degreasing solution, Finecleaner L 4460 A: 20 g/2.4 L + L 4460 B 12 g/2.4 L (pH = 12) manufactured by Parkerizing Co., Ltd. was used. In this case, the evaluation criteria are as follows. [0084] ⊚: ΔE ≤ 2 [0085] ◯: 2 < ΔE ≤ 3 [0086] Δ: 3 < ΔE ≤ 4 [0087] X: ΔE > 4

<Solution Stability>

[0088] The surface treatment composition placed in a container was put into a constant temperature oven at 50° C., and after storage of 7 days, occurrence of precipitates was visually observed, and a change in viscosity was measured. In this case, the evaluation criteria are as follows. [0089] ◯: No generation of precipitates and change in viscosity of less than 1 cP [0090] Δ: No generation of precipitates and change in viscosity of 1 cP or more and less than 5 cP [0091] X: Generation of precipitates or change in viscosity of 5 cP or more

Components of Surface Treatment Composition

[0092] The components of the surface treatment composition used in Examples are as follows: [0093] High molecular weight polysilicon-modified polyurethane main resin: polyurethane resin having weight average molecular weight of 150,000 [0094] Low molecular weight polysilicon-modified polyurethane auxiliary resin (auxiliary resin 1): polyurethane resin having weight average molecular weight of 50,000 [0095] Acrylic urethane auxiliary resin (auxiliary resin 2) : copolymer resin of acrylic resin having methyl methacrylate (MMA) and butyl acrylate (BA) structural units and polycarbonate-based urethane resin having weight average molecular weight of 100,000 [0096] Curing agent: melamine curing agent (CYMEL 303) [0097] Inorganic additive: titania sol compound [0098] Silane coupling agent: silane coupling agent in which vinyltriepoxysilane, methyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane are mixed at weight ratio of 1:1:1 [0099] Adhesion promoter: phosphoric acid ester compound [0100] Coloring pigment: azo-based organic pigment [0101] Pigment stabilizer: carboxylic polymer [0102] Solvent: mixed solvent of water and ethanol.

Example 1: Change in Physical Properties Depending on Content of Resin Mixture

[0103] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 1, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0104] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the specimen were evaluated. The evaluation results are shown in Table 1.

TABLE-US-00001 Classification Composition of composition (wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Solution stability Resin mixture Curing agent Inorganic additive Silane coupling agent Adhesion promoter Coloring pigment Pigment stabilizer Comparative Example 1 65 25 4 4 0.5 1 0.5 x x O x O Inventive Example 1 70 20 4 4 0.5 1 0.5 O ⊚ O O O Inventive Example 2 80 14 2 2 0.5 1 0.5 ⊚ ⊚ ⊚ ⊚ O Inventive Example 3 90 6 1 1 0.5 1 0.5 ⊚ ⊚ ⊚ ⊚ O Comparative Example 2 94 3 1 0.5 0.5 0.5 0.5 x x x O x * The content of the composition is based on 30 wt% of the solid content

[0105] Referring to Table 1, in Inventive Examples 1 to 3 in which the content of the resin mixture satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. However, in Comparative Example 1 in which the amount of the resin mixture contained was too small, the flat sheet corrosion resistance, the processed part corrosion resistance, and the alkali resistance showed poor results, and in Comparative Example 2 in which the amount of the resin mixture contained was too large, the flat sheet corrosion resistance, the processed part corrosion resistance, the blackening resistance, and the solution stability exhibited poor results.

Example 2: Change in Physical Properties Depending on Content Ratio of Main Resin and Auxiliary Resin

[0106] A surface treatment composition containing 80 wt% of a resin mixture including the main resin, the auxiliary resin 1, and the auxiliary resin 2, 10 wt% of a curing agent, 4 wt% of an inorganic additive, 4 wt% of a silane coupling agent, 0.5 wt% of an adhesion promoter, 1 wt% of a coloring pigment, and 0.5 wt% of a pigment stabilizer was prepared. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0107] In the resin mixture, the main resin, the auxiliary resin 1, and the auxiliary resin 2 were mixed at the weight ratio shown in Table 2.

[0108] The surface treatment composition was applied to the test specimen, and the flat sheet corrosion resistance, the processed part corrosion resistance, the blackening resistance, and the alkali resistance of the specimen were evaluated. The evaluation results are shown in Table 2.

TABLE-US-00002 Classification Weight ratio (A:B:C) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Main resin (A) Auxiliary resin 1 (B) Auxiliary resin 2 (C) Comparative Example 3 5 47.5 47.5 X X O X Inventive Example 4 10 45 45 O ⊚ O O Inventive Example 5 50 25 25 ⊚ ⊚ ⊚ ⊚ Inventive Example 6 67 16.5 16.5 ⊚ ⊚ ⊚ ⊚ Inventive Example 7 90 5 5 ⊚ ⊚ ⊚ ⊚ Comparative Example 4 95 2.5 2.5 O X X O * The content of the composition is based on 30 wt% of the solid content

[0109] Referring to Table 2, in Inventive Examples 4 to 7 in which the weight ratio of the main resin to the auxiliary resin satisfied the content ratio suggested by the present disclosure, all the physical properties showed good (o) or higher results. On the other hand, in Comparative Example 3 in which the amount of the water-soluble main resin contained was too small, the flat sheet corrosion resistance, the processed part corrosion resistance, and the alkali resistance showed poor results, and in Comparative Example 4 in which the amount of the auxiliary resin 1 and auxiliary resin 2 contained was too small, the processed part corrosion resistance and the blackening resistance showed poor results.

Example 3: Change in Physical Properties Depending on Content of Curing Agent

[0110] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 3, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0111] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the specimen were evaluated. The evaluation results are shown in Table 3.

TABLE-US-00003 Classification Composition of composition(wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Solution stability Curing agent Resin Inorganic additive Silane coupling agent Adhesion promoter Coloring pigment Pigment stabilizer Comparative Example 5 4 84 5 5 0.5 1 0.5 X X X X O Inventive Example 8 5 84 5 4 0.5 1 0.5 O O O O O Inventive Example 9 15 74 5 4 0.5 1 0.5 ⊚ ⊚ ⊚ ⊚ O Inventive Example 10 25 70 2 1 0.5 1 0.5 ⊚ ⊚ O ⊚ O Comparative Example 6 26 70 1 1 0.5 1 0.5 O O O X X * The content of the composition is based on 30 wt% of the solid content

[0112] Referring to Table 3, in Inventive Examples 8 to 10 in which the content of the melamine curing agent satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. On the other hand, in Comparative Example 5 in which the amount of the melamine curing agent contained was too small, all the physical properties except for the solution stability showed poor results, and in Comparative Example 6 in which the amount of the melamine curing agent contained was too small, the alkali resistance and the solution stability showed poor results.

Example 4: Change in Physical Properties Depending on Content of Organic Additive

[0113] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 4, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0114] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the specimen were evaluated. The evaluation results are shown in Table 4.

TABLE-US-00004 Classification Composition of composition(wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Solution stability Inorganic additive Resin Curing agent Silane coupling agent Adhesion promoter Coloring pigment Pigment stabilizer Comparative Example 7 0.4 84 10 4 0.5 0.6 0.5 X X X O O Inventive Example 11 0.5 84 10 4 0.5 0.5 0.5 O O O O O Inventive Example 12 5 75 14 4 0.5 1 0.5 ⊚ ⊚ O ⊚ O Inventive Example 13 10 70 14 2 0.5 1 0.5 ⊚ ⊚ O ⊚ O Comparative Example 8 11 70 14 3 0.5 1 0.5 X X O O O * The content of the composition is based on 30 wt% of the solid content

[0115] Referring to Table 4, in Inventive Examples 11 to 13 in which the content of the inorganic additive satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. However, in Comparative Example 7 in which the amount of the inorganic additive contained was too small, the flat sheet corrosion resistance, the processed part corrosion resistance, and the blackening resistance showed poor results, and in Comparative Example 8 in which the amount of the inorganic additive contained was too large, the flat sheet corrosion resistance and the processed part corrosion resistance showed poor results.

Example 5: Change in Physical Properties Depending on Content and Type of Silane Coupling Agent

[0116] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 5, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0117] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the specimen were evaluated. The evaluation results are shown in Table 5.

TABLE-US-00005 Classification Composition of composition(wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Solution stability Silane coupling agent Resin Curing agent Inorganic additive Adhesion promoter Coloring pigment Pigment stabilizer Comparative Example 9 0.4 84 10 4 0.5 0.6 0.5 X X X O O Inventive Example 14 0.5 84 10 4 0.5 0.5 0.5 O ⊚ O O O Inventive Example 15 5 75 14 4 0.5 1 0.5 ⊚ ⊚ ⊚ ⊚ O Inventive Example 16 10 70 14 2 0.5 1 0.5 ⊚ ⊚ ⊚ ⊚ O Comparative Example 10 11 70 14 3 0.5 1 0.5 O X X O O * The content of the composition is based on 30 wt% of the solid content

[0118] Referring to Table 5, in Inventive Examples 14 to 16 in which the content of the silane coupling agent satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. On the other hand, in Comparative Example 9 in which the amount of the silane coupling agent contained is too small, the flat sheet corrosion resistance, the corrosion resistance after processing, and the blackening resistance showed poor results, and in Comparative Example 10 in which the amount of the silane coupling agent contained is too large, a hard coating film was formed due to an increase in dryness of the coating film, and thus the processed part corrosion resistance and the blackening resistance showed poor results.

[0119] Meanwhile, a surface treatment composition was prepared by changing the silane coupling agent to the silane coupling agent shown in Table 6 in the surface treatment composition having the composition according to Inventive Example 15, a specimen was prepared in the same manner as described above, and the flat sheet corrosion resistance was evaluated. The results thereof are shown in Table 6.

TABLE-US-00006 Classification A B C D E F G H I J K Flat sheet corrosion resistance Content Content Content Content Content Content Content Content Content Content Content Inventive Example 17 5 0 0 0 0 0 0 0 0 0 0 O Inventive Example 18 0 5 0 0 0 0 0 0 0 0 0 ⊚ Inventive Example 19 0 0 5 0 0 0 0 0 0 0 0 O Inventive Example 20 0 0 0 5 0 0 0 0 0 0 0 ⊚ Inventive Example 21 0 0 0 0 5 0 0 0 0 0 0 O Inventive Example 22 0 0 0 0 0 5 0 0 0 0 0 ⊚ Inventive Example 23 0 0 0 0 0 0 5 0 0 0 0 O Inventive Example 24 0 0 0 0 0 0 0 5 0 0 0 O Inventive Example 25 0 0 0 0 0 0 0 0 5 0 0 O Inventive Example 26 0 0 0 0 0 0 0 0 0 5 0 ⊚ Inventive Example 27 0 0 0 0 0 0 0 0 0 0 5 O Inventive Example 28 2.5 2.5 0 0 0 0 0 0 0 0 0 O Inventive Example 29 2.5 0 0 2.5 0 0 0 0 0 0 0 O Inventive Example 30 0 2.5 0 0 0 2.5 0 0 0 0 0 ⊚ Inventive Example 31 0 0 0 2.5 0 2.5 0 0 0 0 0 O Inventive Example 32 0 0 0 0 2.5 0 2.5 0 0 0 0 O Inventive Example 33 0 0 0 0 0 2.5 0 0 0 2.5 0 ⊚ Inventive Example 34 0 0 2.5 0 0 2.5 0 0 0 0 0 O Inventive Example 35 0 0 0 0 0 0 2.5 0 0 2.5 0 O Inventive Example 36 2.5 0 0 0 0 0 0 0 0 2.5 0 O Inventive Example 37 0 0 0 0 0 0 0 0 0 2.5 2.5 ○ Inventive Example 38 0 0 0 2.5 0 0 0 0 2.5 0 0 ○ Inventive Example 39 0 0 0 0 2.5 0 0 2.5 0 0 0 ○ Inventive Example 40 0 0 0 0 0 0 0 2.5 0 0 2.5 ○ Inventive Example 41 0 2.5 2.5 0 0 0 0 0 0 0 0 ⊚ Inventive Example 42 0 2 2 0 0 0 0 0 0 0 1 ○ Inventive Example 43 0 0 0 1 0 0 2 0 2 0 0 ○ Inventive Example 44 0 0 0 0 2 1 0 0 2 0 0 ○ Inventive Example 45 0 2 0 3.5 0 0 1 0 0 0 2 ○ Inventive Example 46 0 2 0 0 0 0 0 0 0 1 2 ⊚ Inventive Example 47 2 0 2 0 0 0 0 0 0 0 1 ○ Inventive Example 48 0 1 0 0 0 0 0 0 2 2 0 ○ Inventive Example 49 0 2 0 0 1 0 0 0 0 2 0 ○ Inventive Example 50 0 0 0 0 0 0 2 2 0 0 1 ○ A:2-(3,4-Epoxycyclohexyl)-ethyltrimethoxysilane G: N-2-(Aminoethyl)-3-aminopropyltriethoxysilane B: 3- Glycidoxypropyltrimethoxysilane H:3-Aminopropyltrimethoxysilane C: 3-Glycidoxypropylmethyldiethoxysilane I:3-Aminopropyltriethoxysilane D: 3- Glycidoxypropyltriethoxysilane J: Vinyltriepoxysilane E: N-2-(Aminoethyl)-3-aminopropylmethyldimethoxysilane K: Methyltrimethoxysilane F:N-2-(Aminoethyl)-3-aminopropyltrimethoxysilane * The content of the composition is based on 30 wt% of the solid content

[0120] Referring to Table 6, in Inventive Examples 17 to 50, the flat sheet corrosion resistance showed good (o) or excellent (⊚) results. In particular, in Inventive Example 46 in which 3-glycidoxypropyltrimethoxysilane, vinyltriepoxysilane, and methyltrimethoxysilane were used at a weight ratio of 2:1:2, the area of white rust generated after 144 hours or longer was 0%, which showed the best results.

Example 6: Change in Physical Properties Depending on Content of Adhesion Promoter

[0121] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 7, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0122] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the specimen were evaluated. The evaluation results are shown in Table 7.

TABLE-US-00007 Classification Composition of composition (wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Solution stability Adhesion promoter Resin Curing agent Silane coupling agent Inorganic additive Coloring pigment Pigment stabilizer Comparative Example 11 0.05 82 10 3 3.45 1 0.5 X X X ○ ○ Inventive Example 51 0.1 82 10 3 3.4 1 0.5 ○ ○ ○ ○ ○ Inventive Example 52 1 75 14 4 4.5 1 0.5 ⊚ ⊚ ⊚ ⊚ ○ Inventive Example 53 2 75 14 4 3.5 1 0.5 ⊚ ⊚ ○ ⊚ ○ Comparative Example 12 2.5 75 14 3 4 1 0.5 ○ ○ ○ ○ X * The content of the composition is based on 30 wt% of the solid content

[0123] Referring to Table 7, in Inventive Examples 51 to 53 in which the content of the adhesion promoter satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. However, in Comparative Example 11 in which the amount of the adhesion promoter contained was too small, the flat sheet corrosion resistance, the processed part corrosion resistance, and the alkali resistance showed poor results, and in Comparative Example 12 in which the amount of the adhesion promoter contained was too large, the solution stability showed a poor result.

Example 7: Change in Physical Properties Depending On Content of Coloring Pigment

[0124] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 8, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0125] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the specimen were evaluated. The test specimen treated with the surface treatment composition was observed with the naked eye, and the degree of surface color expression was classified into excellent (⊚), good (o), and poor (X). The evaluation results are shown in Table 8.

TABLE-US-00008 Classification Composition of composition(wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Surface color expression Solution stability Coloring pigment Resin Curing agent Inorganic additive Adhesion promoter Silane coupling agent Pigment stabilizer Comparative Example 13 0.05 84 10 4 0.5 0.95 0.5 ○ ⊚ ○ ○ X ○ Inventive Example 54 0.1 84 10 4 0.5 0.9 0.5 ○ ⊚ ○ ○ ○ ○ Inventive Example 55 1 75 14 4 0.5 5 0.5 ⊚ ⊚ ⊚ ⊚ ⊚ ○ Inventive Example 56 2 75 14 4 0.5 4 0.5 ⊚ ⊚ ⊚ ⊚ ⊚ ○ Comparative Example 14 2.5 75 14 3 0.5 4.5 0.5 X X ⊚ ○ ⊚ X * The content of the composition is based on 30 wt% of the solid content

[0126] Referring to Table 8, in Inventive Examples 54 to 56 in which the content of the coloring pigment satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. However, in Comparative Example 13 in which the amount of the coloring pigment contained was too small, the surface color expression showed a poor result, and in Comparative Example 14 in which the amount of the coloring pigment contained was too large, the flat sheet corrosion resistance, the processed part corrosion resistance, and the solution stability showed poor results.

Example 8: Change in Physical Properties Depending on Content of Pigment Stabilizer

[0127] A resin mixture obtained by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at a weight ratio of 1:0.5:0.5, a curing agent, an inorganic additive, a silane coupling agent, an adhesion promoter, a coloring pigment, and a pigment stabilizer were mixed in the contents shown in Table 9, thereby preparing a surface treatment composition. In the surface treatment composition, a mixed solvent of water and ethanol was used as a solvent.

[0128] The solution stability of the prepared surface treatment composition was evaluated. In addition, the surface treatment composition was applied to the test specimen described above, and then flat sheet corrosion resistance, processed part corrosion resistance, blackening resistance, alkali resistance, and gloss of the specimen were evaluated. The gloss of the test specimen treated with the surface treatment composition was measured at an incident angle of 60° using a gloss meter. It was classified as good (o) when the measurement result was 80 or more and as poor (X) when the measurement was less than 80. The evaluation results are shown in Table 9.

TABLE-US-00009 Classification Composition of composition(wt%) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Gloss Alkali resistance Solution stability Pigment stabilizer Resin Curing agent Silane coupling agent Inorganic additive Adhesion promoter Coloring pigment Comparative Example 15 0.05 82 10 3 3.45 0.5 1 ○ ○ ○ ○ ○ X Inventive Example 57 0.1 82 10 3 3.4 0.5 1 ○ ○ ○ ○ ○ ○ Inventive Example 58 0.5 75 14 4 5 0.5 1 ⊚ ⊚ ⊚ ○ ⊚ ○ Inventive Example 59 1 75 14 4 4.5 0.5 1 ⊚ ⊚ ○ ○ ⊚ ○ Comparative Example 16 1.5 75 14 4 4 0.5 1 ○ ○ ○ X ○ ○ * The content of the composition is based on 30 wt% of the solid content

[0129] Referring to Table 9, in Inventive Examples 57 to 59 in which the content of the pigment stabilizer satisfied the content suggested by the present disclosure, all the physical properties showed good (o) or higher results. However, in Comparative Example 15 in which the amount of the pigment stabilizer was too small, the solution stability showed a poor result, and in Comparative Example 16 in which the amount of the pigment stabilizer was too large, the gloss showed a poor result.

Example 9: Change in Physical Properties According to Thickness and Drying Temperature of Coating Film

[0130] The test specimen was bar-coated with the surface treatment composition according to Inventive Example 2 and then was dried with a hot-air drying furnace. However, in the surface treatment composition, a resin mixture was prepared by mixing the main resin, the auxiliary resin 1, and the auxiliary resin 2 at 50:25:25 according to Inventive Example 6, and a mixture obtained by mixing 3-glycidoxypropyltrimethoxysilane, vinyltriepoxysilane, and methyltrimethoxysilane at a weight ratio of 2:1:2 was used as the silane coupling agent according to Inventive Example 46.

[0131] The thickness and the PMT temperature of the coating layer were controlled as shown in Table 10.

TABLE-US-00010 Classification Coating layer thickness (.Math.m) Drying temperature (°C) Flat sheet corrosion resistance Processed part corrosion resistance Blackening resistance Alkali resistance Comparative Example 17 0.5 180 Δ X Δ Δ Inventive Example 60 1 180 ⊚ ⊚ ⊚ ⊚ Inventive Example 61 4 180 ⊚ ⊚ ⊚ ⊚ Inventive Example 62 7 180 ⊚ ⊚ ○ ⊚ Inventive Example 63 10 180 ⊚ ⊚ ○ ⊚ Comparative Example 18 11 180 ⊚ X ○ ⊚ Comparative Example 19 5 50 X X X X Inventive Example 64 5 70 ○ ○ ○ Δ Inventive Example 65 5 100 ⊚ ⊚ ⊚ ⊚ Inventive Example 66 5 250 ⊚ ⊚ ○ ⊚ Comparative Example 20 5 270 ⊚ ⊚ X ⊚

[0132] As shown in Table 10, in Inventive Examples 60 to 63 in which the coating layer having a thickness of 1 to 10 .Math.m was formed, all the physical properties showed good (o) or higher results. On the other hand, in Comparative Example 17 in which the formed coating film was too thin, the flat sheet corrosion resistance, the blackening resistance, and the alkali resistance showed moderate (Δ) results, and the processed part corrosion resistance showed a poor result. Meanwhile, in Comparative Example 18 in which the formed coating film was too thick, the processed part corrosion resistance showed a poor result, and since there were no improved physical properties compared to Inventive Example 63, a coating film thickness having a thickness of more than 10 .Math.m was not required in terms of cost-effectiveness. Meanwhile, as shown in Table 10, in Inventive Examples 64 to 66 in which the coating layer was formed by drying the coating film at 70 to 250° C., all the physical properties showed good (o) or higher results. Meanwhile, in Comparative Example 19 in which the drying temperature was excessively low, the coating film was not sufficiently dried, and thus, all the physical properties showed poor results. Meanwhile, in Comparative Example 20 in which the drying temperature was too high, the blackening resistance showed a poor result due to fume drop on the steel sheet caused by a condensation phenomenon of water vapor generated in the steel sheet during the air cooling process (water cooling). Although exemplary embodiments in the present disclosure have been described in detail above, it will be apparent to those skilled in the art that the scope of the present disclosure is not limited thereto, but modifications and variations could be made without departing from the technical idea of the present disclosure described in the claims.