Surface treatment composition for galvanized alloy alloy sheet, galvanized alloy alloy

Abstract

The present invention relates to: a surface treatment composition capable of imparting excellent corrosion resistance, fingerprint resistance, and stain discoloration resistance to a zinc-plated alloy steel sheet used as a building material or the like; a zinc-plated alloy steel sheet surface-treated with the composition; and a method for manufacturing the zinc-plated alloy steel sheet.

Description

Technical Field

[0001] The present invention relates to a surface treatment composition for a galvanized alloy steel sheet, a galvanized alloy steel sheet surface-treated with the composition, and a method for manufacturing the same. Background Art

[0002] Generally, compared with a pure galvanized steel sheet, most of the exposed surface of a steel sheet having a galvanized alloy layer, which is a steel excellent in corrosion resistance to red rust (as a representative example, a hot-dip galvanized alloy steel sheet containing magnesium (Mg) and aluminum (Al)), is composed of zinc (Zn) or a zinc alloy (Zn alloy). Therefore, when exposed to a general living environment, or particularly to a humid atmosphere, white rust is likely to occur on the surface. In addition, since magnesium and aluminum contained in the plating layer have a higher oxygen affinity than zinc, blackening is likely to occur when the oxygen combined with zinc is insufficient.

[0003] In addition, compared with a pure galvanized steel sheet, if fingerprint stains and contaminants cannot ensure fingerprint resistance on the surface, the contaminants penetrate the plating layer, resulting in incomplete oxidation, causing black stain discoloration, and thus surface appearance defects occur. Such surface stain discoloration defects tend to occur more frequently particularly when used in a high-temperature and high-humidity environment.

[0004] In the past, as a part of the rust prevention treatment, the metal surface was pretreated with 5 - 100 mg / m 2 of chromate and then an organic film was formed. However, due to heavy metals such as chromium (Cr) contained in the pretreatment agent, additional pretreatment equipment and processes are required, and due to heavy metal wastewater, the safety of workers becomes a problem. In addition, a solution containing hexavalent chromium generated in washing water and wastewater, etc. needs to be treated by a special treatment process, so there is a problem of increased manufacturing cost, and there is a problem of chromium ion elution when the chromate-treated plated steel sheet is used or discarded, so the environmental pollution problem is serious.

[0005] In order to solve such problems while ensuring corrosion resistance, a surface treatment agent such as a chromium-free corrosion-resistant metal coating agent has been developed in the prior art. As an example, Patent Document 1 and Patent Document 2 disclose a technique for forming a film substance by containing aluminum phosphate, or by combining aromatic carboxylic acids such as sodium acetate, sodium borate, and imidazole, and a surfactant, etc. with tannic acid, but they have a problem of poor corrosion resistance. Patent Document 3 discloses a surface treatment agent composed of zirconium carbonate, oxovanadium ions, zirconium compounds, etc. However, although the surface treatment agent has good corrosion resistance, it has a problem of poor blackening resistance.

[0006] In addition, Patent Document 4 discloses a surface treatment agent composed of a titanium-based compound, a zirconium-based compound, a phosphate-based compound, a molybdenum-based compound, etc., but there is a problem that it cannot suppress the blackening phenomenon in galvanized alloy steel sheets containing magnesium (Mg) and aluminum (Al), etc. Patent Document 5 discloses a surface treatment agent composed of ammonium molybdate, a water-dispersed urethane resin, isopropylamine, ammonium zirconium carbonate, an epoxy group silane coupling agent, and silica sol, but there is a problem that it cannot impart sufficient corrosion resistance.

[0007] In recent years, in order to use galvanized alloy steel sheets as building materials, etc., it is necessary to have delicate surface characteristics. Not only does it need to exhibit excellent corrosion resistance in a corrosive environment, but also when the customer processes the galvanized alloy steel sheet, it will not change color when in contact with fingerprint stains or contaminants. Importantly, it is necessary to ensure fingerprint-proof or stain-resistant color change characteristics.

[0008] (Patent Document 1) Japanese Unexamined Patent Publication No. 53-28857

[0009] (Patent Document 2) Japanese Unexamined Patent Publication No. 51-71233

[0010] (Patent Document 3) Japanese Unexamined Patent Publication No. 2002-332574

[0011] (Patent Document 4) Japanese Examined Patent Publication No. 7-096699

[0012] (Patent Document 5) Japanese Unexamined Patent Publication No. 2005-146340 Summary of the Invention

[0013] (I) Technical Problems to be Solved

[0014] An object of one aspect of the present invention is to provide a surface treatment composition that can impart excellent corrosion resistance, fingerprint-proof property, and stain-resistant color change property to galvanized alloy steel sheets used as building materials, etc.

[0015] In particular, an object of the present invention is to provide a surface treatment composition that can impart excellent corrosion resistance and fingerprint-proof color change property to galvanized alloy steel sheets in a high-temperature and high-humidity environment.

[0016] In addition, an object of the present invention is to provide a surface treatment composition that is completely free of heavy metal components such as chromium, which are environmental pollutants, and is therefore harmless to humans and does not cause problems associated with environmental pollution.

[0017] In addition, an object of the present invention is to provide a galvanized alloy steel sheet having excellent corrosion resistance, fingerprint-proof property, and stain-resistant color change property, and a manufacturing method thereof.

[0018] The technical problems of the present invention are not limited to the above content. Additional technical problems of the present invention are described throughout the content of the specification, and those skilled in the art to which the present invention pertains can easily understand the additional technical problems of the present invention based on the content recorded in the specification of the present invention.

[0019] (II) Technical Solution

[0020] One embodiment of the present invention relates to a surface treatment composition, which is a surface treatment composition containing solids and a solvent. Relative to 100% by weight of the solids, the surface treatment composition contains: 70 - 90% by weight of a resin mixture containing a high molecular weight polysilicon-modified polyurethane main resin, a low molecular weight polysilicon-modified polyurethane auxiliary resin, and an epoxy auxiliary resin; 5 - 25% by weight of a melamine-based curing agent; 0.5 - 10% by weight of an anti-oxidation discoloration agent; 0.5 - 10% by weight of a silane compound; 0.5 - 10% by weight of an anti-rust and corrosion-resistant agent; and 0.5 - 5% by weight of an anti-fingerprint property improver.

[0021] The high molecular weight polysilicon-modified polyurethane main resin (A), the low molecular weight polysilicon-modified polyurethane auxiliary resin (B), and the epoxy auxiliary resin (C) can be mixed in a weight ratio of 1:4.5:4.5 to 9:0.5:0.5.

[0022] The glass transition temperature (Tg) of the high molecular weight polysilicon-modified polyurethane main resin (A) can be -20°C to -10°C, and the weight average molecular weight (Mw) can be 100,000 to 200,000.

[0023] The glass transition temperature (Tg) of the low molecular weight polysilicon-modified polyurethane auxiliary resin (B) can be -30°C to -20°C, and the weight average molecular weight (Mw) can be 30,000 to 70,000.

[0024] The epoxide equivalent ratio of the epoxy auxiliary resin (C) can be 450 - 550 g / eq, and the weight average molecular weight (Mw) can be 450 to 4,000.

[0025] The melamine-based curing agent can contain one or more functional groups selected from methoxymethyl functional groups, hydroxymethyl functional groups, and imino functional groups, and these functional groups can crosslink a backbone polymer resin containing carboxyl groups.

[0026] The anti-oxidation discoloration agent can be one or more selected from ammonium molybdate and sodium molybdate.

[0027] The silane compound may include one or more selected from vinylmethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, tetraethyl orthosilicate, tetramethyl orthosilicate, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propylamine, N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltriethoxysilane, and N-[2-(vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilane.

[0028] The silane compound may be hydrolyzed by one or more acids selected from formic acid, acetic acid, phosphoric acid, hydrochloric acid, and nitric acid.

[0029] The rust and corrosion inhibitor may be one or more selected from phosphoric acid-based rust inhibitors, fluorine-based rust inhibitors, vanadium-based rust inhibitors, cerium salt-based rust inhibitors, and selenium salt-based rust inhibitors.

[0030] The anti-fingerprint property improver may be one or more selected from paraffin wax, olefin wax, palm wax, polyester wax, polypropylene wax, polyethylene-tetrafluoroethylene wax, and polytetrafluoroethylene wax.

[0031] Based on the total weight of the surface treatment composition, the content of the solid may be 20-40% by weight, and the balance may be a solvent.

[0032] Based on the total weight of the solvent, the solvent may include 20-40% by weight of N-ethyl-2-pyrrolidone (NEP, N-Ethyl-2-pyrrolidone) and the balance of water.

[0033] Another embodiment of the present invention relates to a surface-treated galvanized alloy steel sheet, which includes: a steel sheet; a galvanized alloy layer formed on at least one surface of the steel sheet; and a surface treatment film layer formed on the galvanized alloy layer, wherein the surface treatment film layer is formed from the surface treatment composition.

[0034] The ternary hot-dip galvanized alloy layer may include an Al-enriched layer formed at the interface, and the occupation area ratio of the Al-enriched layer may be 70% to 100%.

[0035] The ternary hot-dip galvanized alloy layer may contain: Al: 0.2-15% by weight, Mg: 0.5-3.5% by weight, the balance of Zn, and inevitable impurities.

[0036] The thickness of the surface treatment film layer can be 1 μm to 10 μm.

[0037] Another embodiment of the present invention relates to a method for manufacturing a surface-treated galvanized alloy steel sheet, the manufacturing method comprising the steps of: coating the surface treatment composition on a galvanized alloy steel sheet formed with a galvanized alloy layer; and drying the surface treatment composition to form a surface treatment film layer.

[0038] The surface treatment composition can be coated with a thickness of 2.5 μm to 50 μm.

[0039] In the step of forming the surface treatment film layer, the temperature can be raised to 70 - 250°C to dry the surface treatment composition.

[0040] (III) Beneficial effects

[0041] By coating the surface treatment composition according to the present invention on a galvanized alloy steel sheet to form a surface treatment film layer, a galvanized alloy steel sheet having excellent corrosion resistance, fingerprint resistance, and stain discoloration resistance characteristics can be provided.

[0042] In addition, the surface treatment composition according to the present invention is completely free of heavy metal components such as chromium, which are environmental pollutants, and thus is harmless to the human body and does not cause problems caused by environmental pollution.

[0043] Various beneficial advantages and effects of the present invention are not limited to the above content and can be more easily understood during the description of specific embodiments of the present invention. Best mode

[0044] The terms used in this specification are for explaining the present invention and are not for limiting the present invention. In addition, as long as the opposite meaning is not clearly indicated in the relevant definitions, the singular forms used in this specification also include the plural forms.

[0045] The meaning of "comprising" or "including" used in the specification is to embody the components and does not exclude the existence or addition of other components.

[0046] Unless otherwise defined differently, all terms, including technical terms and scientific terms, used in this specification have the same meaning as commonly understood by those skilled in the art. Terms defined in the dictionary should be interpreted as having a meaning consistent with the relevant technical literature and the currently disclosed content.

[0047] The present invention relates to a surface treatment composition for galvanized alloy steel sheets. The surface treatment composition has excellent solution stability. As a preferred example of galvanized alloy steel sheets, when the surface treatment composition is applied to ternary hot-dip galvanized alloy steel sheets, it has excellent flat corrosion resistance, processing part corrosion resistance, fingerprint resistance, and excellent stain-resistant discoloration characteristics. In addition, the present invention relates to a galvanized alloy steel sheet surface-treated with the surface treatment composition and a manufacturing method thereof.

[0048] First, a detailed description will be given of the surface treatment composition as a specific embodiment of the present invention.

[0049] The surface treatment composition is a surface treatment composition containing a solid content and a solvent. With respect to 100% by weight of the solid content, the surface treatment composition may contain: 70 - 90% by weight of a resin mixture containing a high molecular weight polysilicon-modified polyurethane main resin, a low molecular weight polysilicon-modified polyurethane auxiliary resin, and an epoxy auxiliary resin; 5 - 25% by weight of a melamine-based curing agent; 0.5 - 10% by weight of an anti-oxidation discoloration agent; 0.5 - 10% by weight of a silane compound; 0.5 - 10% by weight of an anti-rust and corrosion inhibitor; and 0.5 - 5% by weight of a fingerprint resistance improver.

[0050] Hereinafter, a detailed description will be given of the composition of each composition.

[0051] Resin mixture

[0052] The high molecular weight polysilicon-modified polyurethane main resin is a component that can impart excellent corrosion resistance, water resistance, and solvent resistance to galvanized alloy steel sheets. The high molecular weight polysilicon-modified polyurethane main resin is not limited thereto, but can be synthesized from a silicon polymer and a polycarbonate polyol, and has a self-crosslinking property due to the use of a trimer isocyanate polymer during synthesis.

[0053] The weight average molecular weight (Mw) of the high molecular weight polysilicon-modified polyurethane main resin can be from 100,000 to 200,000. When the weight average molecular weight is less than 100,000, it is difficult to ensure sufficient corrosion resistance. On the other hand, when the weight average molecular weight exceeds 200,000, the solution stability will decrease, and the hardness of the film will increase, so problems such as reduced processability may occur.

[0054] The glass transition temperature (Tg) of the high molecular weight polysilicon-modified polyurethane main resin can be from -20°C to -10°C. When the glass transition temperature is lower than -20°C, it is difficult to ensure sufficient corrosion resistance. On the other hand, when the glass transition temperature exceeds -10°C, the solution stability will decrease, and the hardness of the film will increase, so problems such as reduced processability may occur.

[0055] The low molecular weight polysilicon modified polyurethane auxiliary resin is a component that can improve processability and adhesion by imparting soft characteristics to galvanized alloy steel sheets. The low molecular weight polysilicon modified polyurethane auxiliary resin is not limited thereto, but can be synthesized from a silicon polymer and a polycarbonate polyol. Different from the high molecular weight polysilicon modified polyurethane main resin, the low molecular weight polysilicon modified polyurethane auxiliary resin does not have self-crosslinking characteristics.

[0056] The weight average molecular weight of the low molecular weight polysilicon modified polyurethane auxiliary resin can be from 30,000 to 70,000. When the weight average molecular weight is less than 30,000, it is difficult to ensure sufficient corrosion resistance due to the reduced density of the film. On the other hand, when the weight average molecular weight exceeds 70,000, the effect of imparting soft characteristics to the film is insufficient, so problems such as reduced processability and adhesion may occur.

[0057] The glass transition temperature (Tg) of the low molecular weight polysilicon modified polyurethane auxiliary resin can be from -30°C to -20°C. When the glass transition temperature is lower than -30°C, it is difficult to ensure sufficient corrosion resistance due to the reduced density of the film. On the other hand, when the glass transition temperature exceeds -20°C, the effect of imparting soft characteristics to the film is insufficient, so problems such as reduced processability and adhesion may occur.

[0058] The epoxy auxiliary resin is a component used to form a dense film on galvanized alloy steel sheets and improve the flat corrosion resistance.

[0059] The epoxide equivalent ratio of the epoxy auxiliary resin can be 450 - 550 g / eq. When the epoxide equivalent ratio is less than 450 g / eq, the effect of improving the film density and flat corrosion resistance is insufficient. On the other hand, when the epoxide equivalent ratio exceeds 550 g / eq, the film has excessive hardness, so problems such as reduced processability may occur.

[0060] The weight average molecular weight (Mw) of the epoxy auxiliary resin can be from 450 to 4000. When the weight average molecular weight (Mw) is less than 450, the effect of improving the film density and flat corrosion resistance is insufficient. On the other hand, when the weight average molecular weight (Mw) exceeds 4000, the film has excessive hardness, so problems such as reduced processability may occur.

[0061] The resin mixture can be prepared by mixing a high molecular weight polysilicon-modified polyurethane main resin (A), a low molecular weight polysilicon-modified polyurethane auxiliary resin (B), and an epoxy auxiliary resin (C) in a weight ratio of 1:4.5:4.5 to 9:0.5:0.5. Preferably, it can be mixed in a weight ratio of 1:0.5:0.5 to 9:0.5:0.5. More preferably, it can be mixed in a weight ratio of 2:0.5:0.5 to 9:0.5:0.5. For example, A:B:C can be mixed and used in a weight ratio of 2:0.5:0.5, and more preferably in a weight ratio of 1:0.5:0.5.

[0062] When the content of the high molecular weight polysilicon-modified polyurethane main resin in the resin mixture is too small, the flat corrosion resistance, corrosion resistance of the processed part, and alkali resistance of the steel plate may decrease. On the other hand, when the content of the high molecular weight polysilicon-modified polyurethane main resin in the resin mixture is too large, the corrosion resistance of the processed part and blackening resistance of the steel plate may decrease.

[0063] The content of the resin mixture can be 70 - 90 wt% based on 100 wt% of the solids of the surface treatment composition. Preferably, it can be 70.0 - 90.0 wt%. When the content of the resin mixture is less than 70 wt%, it is difficult to ensure sufficient corrosion resistance and alkali resistance. When the content of the resin mixture exceeds 90 wt%, the content of the additives for improving physical properties in the surface treatment composition relatively decreases, so problems such as a decrease in corrosion resistance and a decrease in solution stability may occur.

[0064] Melamine-based curing agent

[0065] The inclusion of the melamine-based curing agent serves to react with the main resin and auxiliary resin of the surface treatment solution composition for galvanized alloy steel plates to form dense crosslinking bonds and thus form a strong coating film. The melamine-based curing agent contains one or more functional groups selected from methoxymethyl functional groups, hydroxymethyl functional groups, and imino functional groups. A characteristic of these functional groups is to crosslink the backbone polymer resin containing carboxyl groups. For example, it can be composed of at least one selected from methoxymethyl melamine, butoxymethyl melamine, ethoxymethyl melamine, and their combinations.

[0066] Based on 100% by weight of the solids of the surface treatment composition, the content of the melamine-based curing agent is preferably 5-25% by weight. When the content of the melamine-based curing agent is less than 5% by weight, sufficient crosslinking bonds cannot be formed, so an improvement in physical properties cannot be expected. When the content of the melamine-based curing agent exceeds 25% by weight, due to excessive crosslinking bonds, the stability of the solution decreases, and a curing phenomenon may occur over time. Based on 100% by weight of the solids of the surface treatment composition, the content of the melamine-based curing agent is more preferably 5.0-25.0% by weight.

[0067] Anti-oxidation discoloration agent

[0068] The anti-oxidation discoloration agent is a component included to prevent the galvanized alloy steel sheet from discoloring when it comes into contact with contaminants in a high-temperature and high-humidity environment. The anti-oxidation discoloration agent may be one or more compounds selected from ammonium molybdate and sodium molybdate.

[0069] Based on 100% by weight of the solids of the surface treatment composition, the content of the anti-oxidation discoloration agent may be 0.5-10% by weight. When the content of the anti-oxidation discoloration agent is less than 0.5% by weight, ensuring sufficient oxidation discoloration resistance cannot be expected. When the content of the anti-oxidation discoloration agent exceeds 10% by weight, the effect of improving oxidation discoloration resistance is minimal. On the other hand, there may be a problem of reduced corrosion resistance. Based on 100% by weight of the solids of the surface treatment composition, the anti-oxidation discoloration agent is preferably 0.50-10.0% by weight.

[0070] Silane compound

[0071] The silane compound is included to modify the water-soluble organic resin and carry out a coupling reaction to form a strong bond between the water-soluble organic resin and the inorganic additive in the surface treatment composition.

[0072] Based on 100% by weight of the solids of the surface treatment composition, the content of the silane compound is preferably 0.5-10% by weight. When the content of the silane compound is less than 0.5% by weight, the content required for coupling the organic resin and the inorganic additive is insufficient, and it is difficult to ensure corrosion resistance. When the content of the silane compound exceeds 10% by weight, there are unreacted silane compounds after reacting with the organic resin, and there may be a problem of reduced corrosion resistance after processing. Based on 100% by weight of the solids of the surface treatment composition, the silane compound is more preferably 0.50-10.0% by weight.

[0073] The silane hydrolyzate compound may include one or more selected from vinylmethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, tetraethyl orthosilicate, tetramethyl orthosilicate, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propylamine, N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltriethoxysilane, and N-[2-(vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilane, and may be hydrolyzed with a solvent selected from one or more of formic acid, acetic acid, phosphoric acid, hydrochloric acid, and nitric acid.

[0074] Rust and corrosion inhibitor

[0075] The rust and corrosion inhibitor is a component included to improve the corrosion resistance of the galvanized alloy steel sheet, and the rust and corrosion inhibitor may be one or more selected from phosphoric acid-based rust inhibitors, fluorine-based rust inhibitors, vanadium-based rust inhibitors, cerium salt-based rust inhibitors, and selenium salt-based rust inhibitors.

[0076] With respect to 100% by weight of the solids of the surface treatment composition, the content of the rust and corrosion inhibitor may be 0.5 - 10% by weight. When the content of the rust and corrosion inhibitor is less than 0.5% by weight, it may be difficult to ensure blackening resistance and alkali resistance, and when the content of the rust and corrosion inhibitor exceeds 10% by weight, it may be difficult to ensure corrosion resistance. With respect to 100% by weight of the solids of the surface treatment composition, the content of the rust and corrosion inhibitor is preferably 0.50 - 10.0% by weight.

[0077] Fingerprint resistance improver

[0078] The fingerprint resistance improver may preferably be one or two or more selected from paraffin wax, olefin wax, palm wax, polyester wax, polypropylene wax, polyethylene-tetrafluoroethylene wax, and polytetrafluoroethylene wax.

[0079] With respect to 100% by weight of the solids of the surface treatment composition, the content of the fingerprint resistance improver may be 0.5 - 5% by weight. When the content of the fingerprint resistance improver is less than 0.5% by weight, it may be difficult to ensure sufficient fingerprint resistance, and when the content of the fingerprint resistance improver exceeds 5% by weight, it may be difficult to ensure corrosion resistance. With respect to 100% by weight of the solids of the surface treatment composition, the content of the fingerprint resistance improver is preferably 0.50 - 5.0% by weight.

[0080] Solvent

[0081] The surface treatment composition contains water as a solvent to dilute each component, and the water can be deionized water or distilled water. The solvent is included as the balance other than each component of the present invention, and the content of the solvent can be 60-80% by weight. Further, the surface treatment composition according to an embodiment can further contain N-ethyl-2-pyrrolidone (NEP) as a co-solvent to ensure solution stability, and the content of the N-ethyl-2-pyrrolidone in the whole solvent can be 20-40% by weight.

[0082] The galvanized alloy steel sheet surface-treated with the surface treatment composition containing a water-soluble organic resin, an anti-oxidation discoloration agent, and a corrosion-resistant inorganic compound according to an embodiment of the present invention not only has excellent corrosion resistance and stain discoloration resistance, but also has excellent surface color and gloss. In addition, the surface treatment composition according to an embodiment of the present invention does not contain hexavalent chromium, which is harmful to the environment, and contains a water-soluble organic resin and an inorganic compound harmless to the human body as main components, so it has the effect of preventing harm to the human body and environmental pollution problems.

[0083] According to a specific embodiment of the present invention, there is provided a galvanized alloy steel sheet surface-treated with the above surface treatment composition.

[0084] Specifically, the surface-treated galvanized alloy steel sheet can include: a steel sheet; a galvanized alloy layer formed on at least one surface of the steel sheet; and a surface treatment film layer formed on the galvanized alloy layer.

[0085] As an example of the galvanized alloy layer, it can be a ternary hot-dip galvanized alloy layer. As a specific example, it can be a coating containing Al: 0.2-15% by weight, Mg: 0.5-3.5% by weight, the balance of Zn and inevitable impurities.

[0086] In the ternary hot-dip galvanized alloy steel sheet, Mg plays a very important role in improving the corrosion resistance of the ternary hot-dip galvanized alloy steel sheet, and forms a dense zinc hydroxide-based corrosion product on the surface of the coating in a corrosive environment, thereby effectively preventing the corrosion of the ternary hot-dip galvanized alloy steel sheet. To ensure the desired corrosion resistance effect of the present invention, the coating needs to contain more than 0.5% by weight of Mg, and more preferably, contain more than 0.9% by weight of Mg. However, when the content of Mg is too high, the Mg oxidation scum on the surface of the plating bath increases sharply, which will offset the antioxidant effect brought by adding trace elements. To prevent this problem, the coating needs to contain 3.5% by weight or less of Mg, and more preferably, contain 3.2% by weight or less of Mg.

[0087] In addition, in a ternary hot-dip galvanized alloy steel sheet, Al inhibits the formation of Mg oxide scum in the plating bath and reacts with Zn and Mg in the plating bath to form a Zn-Al-Mg-based intermetallic compound, thereby improving the corrosion resistance of the plated steel sheet. To obtain the above effects, the coating needs to contain 0.2 wt% or more of Al, and more preferably, 0.9 wt% or more of Al. However, when the content of Al is excessive, it may cause deterioration in the weldability and phosphate treatability of the plated steel. To prevent this problem, the coating needs to contain 15 wt% or less of Al, and more preferably, 12 wt% or less of Al.

[0088] The ternary hot-dip galvanized alloy steel sheet may include an Al-rich layer formed at the interface between the steel sheet and the ternary hot-dip galvanized alloy layer. The occupation area ratio of the Al-rich layer may be 70-100%, and more preferably, 73-100%. Herein, the occupation area ratio refers to the ratio of the area of the Al-rich layer to the area of the base iron when observed by projecting along the thickness direction of the base iron from the surface of the plated steel sheet and assuming it is a plane without considering three-dimensional bending, etc. When ensuring an occupation area ratio of 70% or more of the Al-rich layer, the Al-rich layer has a morphology in which fine particles are continuously formed, so that the plating property and plating adhesion can be significantly improved.

[0089] Relative to the solid content of 100 wt% of the composition, the surface treatment film layer formed on the galvanized alloy layer may be formed from a surface treatment composition containing: 70-90 wt% of a resin mixture containing a high molecular weight polysilicon-modified polyurethane main resin, a low molecular weight polysilicon-modified polyurethane auxiliary resin, and an epoxy auxiliary resin; 5-25 wt% of a melamine-based curing agent; 0.5-10 wt% of an anti-oxidation discoloration agent; 0.5-10 wt% of a silane compound; 0.5-10 wt% of an anti-rust and corrosion inhibitor; 0.5-5 wt% of an anti-fingerprint improver. The surface treatment composition has the same technical features as described above, so it will not be repeated here.

[0090] The surface treatment film layer is a coating formed by drying the above surface treatment composition and corresponds to the components remaining after all the volatile substances contained in the surface treatment film layer containing an organic resin and an inorganic compound have volatilized. Therefore, the surface treatment film layer containing an organic resin and an inorganic compound does not contain water or N-ethyl-2-pyrrolidone as a solvent, and also does not contain the solvents contained in the surface treatment components containing an organic resin and an inorganic compound. Therefore, the components contained in the surface treatment film layer containing an organic resin and an inorganic compound correspond to the content based on 100 wt% of the total solid content.

[0091] According to a specific embodiment of the present invention, there is provided a method for manufacturing a galvanized alloy steel sheet surface-treated with the above surface treatment composition.

[0092] The manufacturing method includes the following steps: coating the above surface treatment composition on a galvanized alloy steel sheet formed with a hot-dip galvanized alloy layer; and drying the surface treatment composition to form a surface treatment film layer.

[0093] The surface treatment composition can be coated with a thickness of 2.5 - 50 μm. In addition, the coated surface treatment composition is dried to form a dry film layer, and the thickness of the dry film layer can be 1 - 10 μm. When the coating thickness of the surface treatment composition is less than 2.5 μm, the surface treatment composition coated on the peak portion of the steel plate roughness is too thin, resulting in a possible problem of reduced corrosion resistance. When the coating thickness of the surface treatment composition exceeds 50 μm, due to the formation of an overly thick film layer, the processability deteriorates, and economic problems may occur due to the increase in solution treatment costs.

[0094] The coating method of the surface treatment composition is not particularly limited as long as it is a commonly used coating method. However, for example, it is preferably carried out by any one of the coating methods selected from roll coating, spraying, dip coating, jet extrusion, and impregnation extrusion.

[0095] Based on the final reached temperature (PMT) of the base steel plate, the process of drying the surface treatment composition coated on the galvanized alloy steel sheet is preferably carried out at a temperature of 70 - 250°C. Based on the final reached temperature (PMT) of the base steel plate, when the drying temperature is lower than 70°C, the curing reaction of the organic resin cannot be fully carried out, resulting in the inability to form a strong film structure, and the corrosion resistance and alkali resistance may deteriorate. On the other hand, based on the final reached temperature (PMT) of the base steel plate, when the drying temperature exceeds 250°C, water vapor and smoke are generated during the water cooling process, so the operation productivity deteriorates, and the surface quality of the product may deteriorate due to the condensation phenomenon of the evaporated water vapor on the upper part of the drying equipment.

[0096] In addition, the drying process is preferably carried out in a hot air drying furnace or an induction heating furnace. When drying the surface treatment composition using a hot air drying furnace, the internal temperature of the hot air drying furnace is preferably 100 - 300°C. When drying the surface treatment composition using an induction heating furnace, the current applied to the induction heating furnace is preferably 1000 - 5000 A, more preferably 1500 - 3500 A. When the internal temperature of the hot air drying furnace is lower than 100°C or the current applied to the induction heating furnace is less than 1000 A, the curing reaction of the surface treatment composition cannot proceed completely, so the corrosion resistance and alkali resistance may deteriorate. In addition, when the internal temperature of the hot air drying furnace exceeds 300°C or the current applied to the induction heating furnace exceeds 5000 A, water vapor and smoke are generated during the water cooling process, so the operation productivity deteriorates, and due to the dew condensation phenomenon where the evaporated water vapor condenses on the upper part of the drying equipment, the surface quality of the product may deteriorate.

[0097] In addition, after drying the surface treatment composition to form a surface treatment film layer, the surface treatment film layer is water-cooled, so that a surface-treated galvanized alloy steel sheet can be finally provided.

[0098] The manufacturing method of the galvanized alloy steel sheet according to a specific embodiment of the present invention can be carried out by a continuous process, and the speed of the continuous process is preferably 80 - 120 meters per minute (mpm). When the speed of the continuous process is less than 80 meters per minute, problems of reduced productivity may occur. When the speed of the continuous process exceeds 120 meters per minute, the solution will scatter during the process of drying the surface treatment composition, so surface defects may be generated. Detailed Description

[0099] Hereinafter, embodiments of the present invention will be described. It is natural that those skilled in the art can make various modifications to the following embodiments without departing from the scope of the present invention. The following embodiments are used to understand the present invention, and the scope of the rights of the present invention is not limited to the following embodiments, but should be determined by the following claims and their equivalents.

[0100] (Example)

[0101] Fabrication of Test Specimens for Testing

[0102] As the galvanized alloy steel sheet, a ternary hot-dip galvanized alloy steel sheet having a ternary hot-dip galvanized alloy layer (by weight%, the ternary hot-dip galvanized alloy layer consists of 1.5% of Mg, 1.5% of Al, and the balance of Zn) (the single-sided coating amount is 0.5 - 2.0 g / m 2) Cut into a size of 7 cm × 15 cm (width × length), remove the oil content, and then coat each prepared composition on a hot-dip galvanized alloy steel sheet using a bar coater. Next, cure under the condition that the peak metal temperature (PMT, substrate surface temperature) is 180 ± 20 °C to fabricate a test specimen.

[0103] Test and evaluation methods

[0104] The evaluation methods and criteria for the physical properties of the surface-treated steel sheet in this example are as follows.

[0105] <Flat panel corrosion resistance>

[0106] According to the method specified in ASTM B117, after treating the specimen, measure the white rust generation rate of the steel sheet over time. At this time, the evaluation criteria are as follows.

[0107] ◎: The time required to generate white rust is 144 hours or more

[0108] ○: The time required to generate white rust is more than 96 hours and less than 144 hours

[0109] △: The time required to generate white rust is more than 55 hours and less than 96 hours

[0110] ×: The time required to generate white rust is less than 55 hours

[0111] <Corrosion resistance of the processed part>

[0112] Use an Erichsen tester to push the specimen to a height of 6 mm, and then measure the degree of white rust generated after 24 hours. At this time, the evaluation criteria are as follows.

[0113] ◎: The area of white rust generated after 48 hours is less than 5%

[0114] △: The area of white rust generated after 48 hours is 5% or more and less than 7%

[0115] ×: The area of white rust generated after 48 hours is 7% or more

[0116] <Oxidation discoloration resistance>

[0117] Drop 0.05 ml of artificial sweat at five positions on the surface of the test piece at intervals of approximately 10 mm, place it in a thermo-hygrostat at a temperature of 65 °C and a humidity of 90 - 95% for 48 hours, leave it at room temperature for 2 hours, then wash it with tap water, observe the surface visually and evaluate. The artificial sweat solution is prepared by dissolving 8 g of sodium phosphate, 8 g of sodium chloride, and 5 g of acetic acid in distilled water, with a pH of approximately 4.5 (fine-tuned with sodium hydroxide), and making up to 1 liter (liter) for use.

[0118] At this time, the evaluation criteria are as follows.

[0119] ◎: Excellent, no surface discoloration

[0120] ○: Good, fine surface traces

[0121] △: Fair, light gray surface discoloration

[0122] ×: Poor, surface blackening discoloration

[0123] <Alkali resistance>

[0124] At 60 °C, immerse the test piece in an alkaline degreasing solution for 2 minutes, then wash it with water and perform air blowing, and then measure the color difference (ΔE) before and after. The alkaline degreasing solution used is Finecleaner L 4460 A: 20 g / 2.4 L + L 4460 B 12 g / 2.4 L (pH = 12) from Daehan Parkerizing Company. At this time, the evaluation criteria are as follows.

[0125] ◎: ΔE ≤ 2

[0126] ○: 2 < ΔE ≤ 3

[0127] △: 3 < ΔE ≤ 4

[0128] ×: ΔE > 4

[0129] <Fingerprint resistance>

[0130] Thinly and evenly coat the surface of the test piece with vaseline and then wipe it off with gauze, and measure the color difference (ΔE) before and after coating the vaseline and after removing it. At this time, the evaluation criteria are as follows.

[0131] ◎: ΔE ≤ 2

[0132] ○: 2 < ΔE ≤ 3

[0133] △: 3 < ΔE ≤ 4

[0134] ×: ΔE > 4

[0135] <Solution stability>

[0136] Put the surface treatment composition into a container and place it in a constant temperature oven at 50 °C. After storing for 7 days, visually observe whether precipitation occurs and measure the viscosity change. At this time, the evaluation criteria are as follows.

[0137] ○: No precipitation occurs, and the viscosity change is less than 1 cP

[0138] △: No precipitation occurs, and the viscosity change is 1 cP or more and less than 5 cP

[0139] ×: Precipitation occurs, or the viscosity change is 5 cP or more

[0140] <Glossiness>

[0141] Measure the glossiness of the test piece with a glossiness meter at an incident angle of 60°. At this time, the evaluation criteria are as follows.

[0142] ○: Good, the glossiness value is 80 or more

[0143] ×: Poor, the glossiness value is less than 80

[0144] Composition of the surface treatment composition

[0145] The composition of the surface treatment composition used in this example is as follows.

[0146] The composition of the surface treatment composition used in the example is as follows.

[0147] Resin mixture

[0148] - High molecular weight polysilicon modified polyurethane main resin (A): A polyurethane resin with a weight average molecular weight of 150,000

[0149] - Low molecular weight polysilicon modified polyurethane auxiliary resin (auxiliary resin 1, B): A polyurethane resin with a weight average molecular weight of 50,000

[0150] - Epoxy auxiliary resin (auxiliary resin 2, C): An epoxy resin with an equivalent ratio of 500 g / eq and a weight average molecular weight of 2,000

[0151] Melamine-based curing agent: Ethoxymethyl melamine

[0152] Anti-oxidation discoloration agent: Ammonium molybdate

[0153] Silane compound: 3-aminopropyltriethoxysilane

[0154] Rust and corrosion inhibitor: Fluorine-based rust inhibitor

[0155] Anti-fingerprint improver: Polyethylene-polytetrafluoroethylene wax

[0156] Solvent: A mixed solvent of water and N-ethyl-2-pyrrolidone (NEP)

[0157] Example 1: Changes in physical properties according to the content of the resin mixture

[0158] A resin mixture (formed by mixing the above-mentioned main resin, auxiliary resin 1, and auxiliary resin 2 in a weight ratio of 1:0.5:0.5), a curing agent, an anti-oxidation and discoloration agent, a silane compound, a rust and corrosion inhibitor, and an anti-fingerprint improver were mixed in the amounts shown in Table 1 to prepare a surface treatment composition. The surface treatment composition contains a mixed solvent of 49% by weight of water and 21% by weight of N-ethyl-2-pyrrolidone (70% by weight based on the total weight of the composition).

[0159] The solution stability of the prepared surface treatment composition was evaluated. In addition, after coating the surface treatment composition on the above test specimens, the flat corrosion resistance, corrosion resistance of the processed part, oxidation blackening resistance, and alkali resistance of the specimens were evaluated. The evaluation results are shown in Table 1 below.

[0160] [Table 1]

[0161]

[0162] The content of the composition is based on 30% by weight of the solid matter. Refer to Table 1 above.

[0163] Refer to Table 1 above. For Invention Examples 1 to 3 where the content of the resin mixture meets the content proposed in the present invention, all physical properties show good (○) or better results. However, for Comparative Example 1 with too little resin mixture content, the flat corrosion resistance, corrosion resistance of the processed part, and alkali resistance show poor results. For Comparative Example 2 with too much resin mixture content, the flat corrosion resistance, corrosion resistance of the processed part, oxidation blackening resistance, and solution stability show poor results.

[0164] Example 2: Changes in physical properties according to the content ratio of the main resin and the auxiliary resin

[0165] A surface treatment composition was prepared, which contains: 80% by weight of a resin mixture containing the above-mentioned main resin (A), auxiliary resin 1 (B), and auxiliary resin 2 (C), 5% by weight of a curing agent, 5.5% by weight of an anti-oxidation and discoloration agent, 8% by weight of a silane compound, 1% by weight of a rust and corrosion inhibitor, and 0.5% by weight of an anti-fingerprint improver. The surface treatment composition contains a mixed solvent of 49% by weight of water and 21% by weight of N-ethyl-2-pyrrolidone (70% by weight based on the total weight of the composition).

[0166] In the resin mixture, the main resin, auxiliary resin 1, and auxiliary resin 2 are mixed at the weight ratios described in Table 2 below.

[0167] After the surface treatment composition is coated on the above test specimens, the flat corrosion resistance, corrosion resistance of the processed part, oxidation blackening resistance, and alkali resistance of the specimens are evaluated, and the evaluation results are recorded in Table 2 below.

[0168] [Table 2]

[0169]

[0170] The content of the components is based on 30 wt% solids.

[0171] Referring to Table 2, all the physical properties of Invention Examples 4 to 9 show results better than good (○). However, in the case of Invention Examples 5 to 9 where the weight ratio of the main resin to the auxiliary resin satisfies the preferred content ratio proposed by the present invention, more preferred effects can be confirmed in terms of flat corrosion resistance, corrosion resistance of the processed part, oxidation resistance, and alkali resistance.

[0172] Example 3: Variation of Physical Properties According to the Content of the Curing Agent

[0173] A resin mixture (formed by mixing the above main resin, auxiliary resin 1, and auxiliary resin 2 at a weight ratio of 1:0.5:0.5), a curing agent, an anti-oxidation discoloration agent, a silane compound, a rust and corrosion inhibitor, and an anti-fingerprint improver are mixed at the contents described in Table 3 to prepare a surface treatment composition. The surface treatment composition contains a mixed solvent of 49 wt% water and 21 wt% N-ethyl-2-pyrrolidone (70 wt% based on the total weight of the composition).

[0174] The solution stability of the prepared surface treatment composition is evaluated. In addition, the surface treatment composition is coated on the above test specimens, and then the flat corrosion resistance, corrosion resistance of the processed part, oxidation discoloration resistance, and alkali resistance of the specimens are evaluated. The evaluation results are recorded in Table 3 below.

[0175] [Table 3]

[0176]

[0177] The content of the components is based on 30 wt% solids.

[0178] Referring to Table 3 described above, all the physical properties of Invention Examples 10 to 12 where the content of the melamine-based curing agent meets the content proposed by the present invention show good (○) or better results. On the other hand, when the content of the melamine-based curing agent is too low (Comparative Example 3), all physical properties except solution stability show poor results. When the content of the melamine-based curing agent is too high (Comparative Example 4), alkali resistance and solution stability show poor results.

[0179] Example 4: Variation of Physical Properties According to the Content of the Anti-Oxidation and Discoloration Agent

[0180] A resin mixture (formed by mixing the above-mentioned main resin, auxiliary resin 1, and auxiliary resin 2 in a weight ratio of 1:0.5:0.5), a curing agent, an anti-oxidation and discoloration agent, a silane compound, a rust and corrosion inhibitor, and an anti-fingerprint property improver are mixed in the contents shown in Table 4 to prepare a surface treatment composition. The surface treatment composition contains a mixed solvent of 49% by weight of water and 21% by weight of N-ethyl-2-pyrrolidone (70% by weight relative to the total weight of the composition).

[0181] The solution stability of the prepared surface treatment composition is evaluated. In addition, after the surface treatment composition is coated on the above-mentioned test specimens, the flat corrosion resistance, processed part corrosion resistance, oxidation and discoloration resistance, and alkali resistance of the specimens are evaluated. The evaluation results are shown in Table 4 below.

[0182] [Table 4]

[0183]

[0184] The content of the composition is based on 30% by weight of the solid content

[0185] Referring to Table 4 described above, all the physical properties of Invention Examples 13 to 15 where the content of the anti-oxidation and discoloration agent meets the content proposed by the present invention show good (○) or better results. On the other hand, the oxidation and discoloration resistance and alkali resistance of Comparative Example 5 with too low a content of the anti-oxidation and discoloration agent show poor results. The flat corrosion resistance, processed part corrosion resistance, and solution stability of Comparative Example 6 with too high a content of the anti-oxidation and discoloration agent show poor results.

[0186] Example 5: Variation of Physical Properties According to the Content of the Silane Compound

[0187] A resin mixture (formed by mixing the above-mentioned main resin, auxiliary resin 1, and auxiliary resin 2 in a weight ratio of 1:0.5:0.5), a curing agent, an anti-oxidation discoloration agent, a silane compound, a rust and corrosion inhibitor, and an anti-fingerprint improver are mixed in the amounts described in Table 5 to prepare a surface treatment composition. The surface treatment composition contains a mixed solvent of 49% by weight of water and 21% by weight of N-ethyl-2-pyrrolidone (70% by weight relative to the total weight of the composition).

[0188] The solution stability of the prepared surface treatment composition is evaluated. In addition, after the surface treatment composition is coated on the above-mentioned test specimens, the flat corrosion resistance, the corrosion resistance of the processed part, the oxidation discoloration resistance, and the alkali resistance of the specimens are evaluated. The evaluation results are recorded in Table 4 below.

[0189] [Table 5]

[0190]

[0191] The content of the composition is based on 30% by weight of the solid content

[0192] Referring to Table 5, when the content of the silane compound meets the content proposed by the present invention (Examples 16 to 18 of the invention), all physical properties show results better than good.

[0193] On the other hand, when the content of the silane compound is too low (Comparative Example 7), the flat corrosion resistance, the corrosion resistance after processing, and the oxidation discoloration resistance show poor results. When the content of the silane compound is too high (Comparative Example 8), the dryness of the film increases, a hard film is formed, the corrosion resistance of the processed part is poor, and the oxidation discoloration resistance shows poor results.

[0194] The surface treatment solution composition according to Example 17 of the invention is used, but the type of the silane hydrolysis compound is the silane coupling agent described in Table 6 below. Specimens are made as described above using the composition containing the silane coupling agent described in Table 6 below, and the flat corrosion resistance is evaluated, and the results are recorded in Table 6.

[0195] [Table 6]

[0196]

[0197]

[0198] As shown in Table 6 described above, Invention Examples 19 to 52 showed good or excellent results in flat panel corrosion resistance. In particular, in the case of the test piece treated with the surface treatment solution composition prepared according to the composition of Invention Example 48, the area of white rust generated after 144 hours or more was 0%, showing the most excellent results.

[0199] Example 6: Changes in Physical Properties According to the Content of Rust and Corrosion Inhibitor

[0200] A resin mixture (prepared by mixing the above-mentioned main resin, auxiliary resin 1, and auxiliary resin 2 in a weight ratio of 1:0.5:0.5), a curing agent, an anti-oxidation and discoloration agent, a silane compound, a rust and corrosion inhibitor, and an anti-fingerprint property improver were mixed in the amounts shown in Table 7 to prepare a surface treatment composition. The surface treatment composition contains a mixed solvent of 49% by weight of water and 21% by weight of N-ethyl-2-pyrrolidone (70% by weight based on the total weight of the composition).

[0201] The solution stability of the prepared surface treatment composition was evaluated. In addition, after the surface treatment composition was coated on the above-mentioned test pieces, the flat panel corrosion resistance, corrosion resistance of the processed part, oxidation and discoloration resistance, and alkali resistance of the test pieces were evaluated. The evaluation results are shown in Table 7 below.

[0202] [Table 7]

[0203]

[0204] The content of the composition is based on 30% by weight of the solid content

[0205] Referring to Table 7, all the physical properties of Invention Examples 53 to 55 in which the content of the rust and corrosion inhibitor meets the content proposed in the present invention showed results of good (○) or above. However, the flat panel corrosion resistance and the corrosion resistance of the processed part in Comparative Example 9 with too little content of the rust and corrosion inhibitor showed poor results, and the oxidation and discoloration resistance and alkali resistance in Comparative Example 10 with too much content of the rust and corrosion inhibitor showed poor results.

[0206] Example 7: Changes in Physical Properties According to the Content of Anti-Fingerprint Property Improver

[0207] A resin mixture (prepared by mixing the above-mentioned main resin, auxiliary resin 1, and auxiliary resin 2 in a weight ratio of 1:0.5:0.5), a curing agent, an anti-oxidation and discoloration agent, a silane compound, a rust and corrosion inhibitor, and an anti-fingerprint property improver were mixed in the amounts shown in Table 8 to prepare a surface treatment composition. The surface treatment composition contains a mixed solvent of 49% by weight of water and 21% by weight of N-ethyl-2-pyrrolidone (70% by weight based on the total weight of the composition).

[0208] The solution stability of the prepared surface treatment composition was evaluated. In addition, after the surface treatment composition was coated on the above test specimens, the flat corrosion resistance, corrosion resistance of the processed part, oxidation discoloration resistance, alkali resistance, and fingerprint resistance of the specimens were evaluated. The evaluation results are shown in Table 8 below.

[0209] [Table 8]

[0210]

[0211] The content of the composition is based on 30 wt% solids

[0212] Referring to Table 8, for Invention Examples 56 to 58 where the content of the fingerprint resistance improver meets the content proposed by the present invention, all physical properties showed good (○) or better results. However, the fingerprint resistance of Comparative Example 11 with too little content of the fingerprint resistance improver showed poor results, and the flat corrosion resistance, corrosion resistance of the processed part, and solution stability of Comparative Example 12 with too much content of the fingerprint resistance improver showed poor results.

[0213] Example 8: Changes in physical properties according to the thickness and drying temperature of the thin film layer

[0214] The surface treatment composition according to Invention Example 2 was coated on test specimens using a bar coater and dried in a hot air drying oven. The thickness of the thin film layer and the PMT temperature were controlled as shown in Table 9 below, and the flat corrosion resistance, corrosion resistance of the processed part, blackening resistance, and alkali resistance of the specimens were evaluated.

[0215] [Table 9]

[0216]

[0217] As shown in Table 9, for Invention Examples 59 to 65 with a thin film layer having a thickness of 1 - 10 μm, all physical properties showed good (○) or better results. On the other hand, the flat corrosion resistance, blackening resistance, and alkali resistance of Comparative Example 13 with an overly thin formed film showed fair (β) results, and the corrosion resistance of the processed part showed poor results. In addition, the corrosion resistance of the processed part of Comparative Example 14 with an overly thick formed film showed poor results, and compared with Invention Example 62, the physical properties did not improve, so a film thickness exceeding 10 μm is not required in terms of economy.

[0218] In addition, as shown in Table 9 mentioned above, in Invention Examples 62 to 65 where the film was dried at 70 - 250°C to form a film layer, all physical properties showed results better than good (○). On the other hand, in Comparative Example 15 where the drying temperature was too low, the film was not sufficiently dried, so all physical properties showed poor results. In addition, in Comparative Example 16 where the drying temperature was too high, due to the dew condensation phenomenon of water vapor generated on the steel plate during the air cooling process (water cooling), smoke droplets on the steel plate were caused, and the blackening resistance showed poor results.

Claims

1. A surface treatment composition, which is a surface treatment composition containing solids and a solvent, Based on 100% by weight of the solids, the surface treatment composition comprises: 70 - 90% by weight of a resin mixture containing a high molecular weight polysilicon-modified polyurethane main resin, a low molecular weight polysilicon-modified polyurethane auxiliary resin, and an epoxy auxiliary resin; 5 - 25% by weight of a melamine-based curing agent; 0.5 - 10% by weight of an anti-oxidation discoloration agent; 0.5 - 10% by weight of a silane compound; 0.5 - 10% by weight of an anti-rust and corrosion-resistant agent; and 0.5 - 5% by weight of an anti-fingerprint improver.

2. The surface treatment composition according to claim 1, wherein, The high molecular weight polysilicon-modified polyurethane main resin (A), the low molecular weight polysilicon-modified polyurethane auxiliary resin (B), and the epoxy auxiliary resin (C) are mixed in a weight ratio of 1:4.5:4.5 to 9:0.5:0.

5.

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

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

5. The surface treatment composition according to claim 1, wherein, The epoxide equivalent ratio of the epoxy auxiliary resin (C) is 450 - 550 g / eq, and the weight average molecular weight (Mw) is 450 to 4,000.

6. The surface treatment composition according to claim 1, wherein, The melamine-based curing agent contains one or more functional groups selected from methoxymethyl functional groups, hydroxymethyl functional groups, and imino functional groups, and these functional groups crosslink the backbone polymer resin containing carboxyl groups.

7. The surface treatment composition according to claim 1, wherein, The anti-oxidation discoloration agent is one or more selected from ammonium molybdate and sodium molybdate.

8. The surface treatment composition according to claim 1, wherein, The silane compound includes one or more selected from vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, tetraethyl orthosilicate, tetramethyl orthosilicate, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propylamine, N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltriethoxysilane, and N-[2-(vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilane.

9. The surface treatment composition according to claim 1, wherein, the silane compound is hydrolyzed by one or more acids selected from formic acid, acetic acid, phosphoric acid, hydrochloric acid, and nitric acid.

10. The surface treatment composition according to claim 1, wherein, the rust and corrosion inhibitor is one or more selected from phosphoric acid-based rust inhibitors, fluorine-based rust inhibitors, vanadium-based rust inhibitors, cerium salt-based rust inhibitors, and selenium salt-based rust inhibitors.

11. The surface treatment composition according to claim 1, wherein, the fingerprint-proofing improver is one or more selected from paraffin wax, olefin wax, palm wax, polyester wax, polypropylene wax, polyethylene-tetrafluoroethylene wax, and polytetrafluoroethylene wax.

12. The surface treatment composition according to claim 1, characterized in that, based on the total weight of the surface treatment composition, the content of the solid matter is 20-40% by weight, and the balance is the solvent.

13. The surface treatment composition according to claim 12, wherein, based on the total weight of the solvent, the solvent contains 20-40% by weight of N-ethyl-2-pyrrolidone (NEP) and the balance is water.

14. A surface-treated ternary hot-dip galvanized alloy steel sheet, which comprises: a steel sheet; a ternary hot-dip galvanized alloy layer formed on at least one surface of the steel sheet; and a surface treatment film layer formed on the ternary hot-dip galvanized alloy layer, wherein the surface treatment film layer is formed from the surface treatment composition according to any one of claims 1 to 13.

15. The ternary hot-dip galvanized alloy steel sheet according to claim 14, wherein, the ternary hot-dip galvanized alloy layer includes an Al-rich layer formed at the interface, and the occupation area ratio of the Al-rich layer is 70% to 100%.

16. The ternary hot-dip galvanized alloy steel sheet according to claim 14, wherein, the ternary hot-dip galvanized alloy layer contains: Al: 0.2-15% by weight, Mg: 0.5-3.5% by weight, the balance is Zn and inevitable impurities.

17. The ternary hot-dip galvanized alloy steel sheet according to claim 14, wherein, the thickness of the surface treatment film layer is 1 μm to 10 μm.

18. A method for manufacturing a surface-treated ternary hot-dip galvanized alloy steel sheet, which comprises the following steps: Coating the surface-treated composition according to any one of claims 1 to 13 on a ternary hot-dip galvanized alloy steel sheet formed with a ternary hot-dip galvanized alloy layer; and Drying the surface-treated composition to form a surface-treated thin film layer.

19. The method for manufacturing a ternary hot-dip galvanized alloy steel sheet according to claim 18, wherein, The surface-treated composition is coated with a thickness of 2.5 μm to 50 μm.

20. The method for manufacturing a ternary hot-dip galvanized alloy steel sheet according to claim 18, wherein, In the step of forming the surface-treated thin film layer, the temperature is raised to 70 - 250 °C to dry the surface-treated composition.

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