Surface treatment composition for a ternary molten zinc alloy-plated steel sheet, the ternary molten zinc alloy-plated steel sheet surface-treated using the same, and method for producing the same

Abstract

The present invention provides a surface treatment composition that can impart excellent corrosion resistance, blackening resistance, alkali resistance, and unique surface color characteristics to ternary hot-dip zinc alloy-plated steel sheet. The surface treatment composition contains, relative to 100% by weight of the solids content of the composition, 70 to 90% by weight of a resin mixture containing a high-molecular-weight polysilicon-modified polyurethane base resin, a low-molecular-weight polysilicon-modified polyurethane auxiliary resin, and an acrylic-urethane auxiliary resin; 5 to 25% by weight of a melamine-based curing agent; 0.5 to 10% by weight of an inorganic additive; 0.5 to 10% by weight of a silane coupling agent; 0.1 to 2% by weight of an adhesion promoter; 0.1 to 2% by weight of a coloring pigment; and 0.1 to 1% by weight of a pigment stabilizer.

Description

[Technical field]

[0001] The present invention relates to a surface treatment composition for a ternary hot-dip zinc alloy-plated steel sheet, a ternary hot-dip zinc alloy-plated steel sheet surface-treated with the same, and a method for producing the same. [Background technology]

[0002] Generally, steel sheets with hot-dip zinc alloy plating layer containing magnesium (Mg) and aluminum (Al), which is a steel material with superior corrosion resistance against red rust compared to pure galvanized steel sheets, have most of the exposed surface composed of zinc (Zn) or zinc alloy (Zn alloy), and when exposed to general living environments or especially humid atmospheres, the surface develops white rust. In addition, magnesium and aluminum contained in the plating layer have a higher oxygen affinity than zinc, so blackening is likely to occur when there is a shortage of oxygen to bind to zinc.

[0003] Conventionally, metal surfaces have been treated with 5 to 100 mg / m 2 After pre-treating with chromate, an organic film was formed. However, the heavy metals contained in the pre-treatment agent, such as chromium (Cr), necessitated additional pre-treatment equipment and processes, and the safety of workers due to heavy metal wastewater became an issue. In addition, solutions containing hexavalent chromium generated in the washing water and wastewater had to be treated using a special treatment process, which increased manufacturing costs, and chromate-treated plated steel sheets also had the problem of eluting chromium ions during use or disposal, causing serious environmental pollution problems.

[0004] In order to solve these problems while ensuring corrosion resistance, the prior art has developed surface treatment agents such as corrosion-resistant metal coating agents that do not contain chromium. For example, Patent Documents 1 and 2 disclose a technique for forming a coating material by incorporating aluminum biphosphate or by combining tannic acid with sodium acetate, sodium borate, aromatic carboxylic acids such as imidazole, and surfactants, but these have the problem of deteriorating corrosion resistance. Patent Document 3 discloses a surface treatment agent composed of zirconium carbonate, vanadyl ions, and zirconium compounds, but while this has good corrosion resistance, it has the problem of being vulnerable to blackening.

[0005] On the other hand, Patent Document 4 discloses a surface treatment agent composed of titanium-based, zirconium-based, phosphoric acid-based, molybdenum-based compounds, etc., but there is a problem in that the blackening phenomenon cannot be suppressed in hot-dip zinc alloy-plated steel sheets using magnesium (Mg), aluminum (Al), etc. Patent Document 5 discloses a surface treatment agent composed of ammonium molybdate, water-dispersed urethane resin, isopropylamine, ammonium zirconium carbonate, epoxy-based silane coupling agent, and silica sol, but there is a problem in that sufficient corrosion resistance cannot be imparted.

[0006] On the other hand, in order to use steel materials as building materials, the surface properties must be beautiful, and it is necessary to impart a unique hue to the steel materials so that the surface of the steel materials can be distinguished from existing hot-dip galvanized steel materials and hot-dip zinc alloy plated steel materials when customers use the steel materials. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 53-28857 [Patent Document 2] Japanese Patent Publication No. 51-71233 [Patent Document 3] Japanese Patent Publication No. 2002-332574 [Patent Document 4] Japanese Patent Registration No. Hei 7-096699 [Patent Document 5] Japanese Patent Publication No. 2005-146340 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been devised in view of the above-mentioned circumstances, and an object of the present invention is to provide a surface treatment composition which can impart excellent corrosion resistance, blackening resistance, alkali resistance and unique surface color characteristics to ternary hot-dip zinc alloy plated steel sheets used as building materials.

[0009] Another object of the present invention is to provide a surface treatment composition which has excellent pigment dispersion stability, does not cause precipitation or aggregation even when used after long-term storage, and can impart excellent surface gloss to hot-dip zinc alloy-plated steel sheets.

[0010] Another object of the present invention is to provide a surface treatment composition which is completely free of heavy metal components such as chromium, which are environmental pollutants, and is therefore harmless to the human body and does not cause problems due to environmental pollution.

[0011] Another object of the present invention is to provide a hot-dip zinc alloy plated steel sheet having excellent corrosion resistance, blackening resistance, alkali resistance and unique surface color characteristics, and a manufacturing method thereof. [Means for solving the problem]

[0012] According to one embodiment of the present invention, there is provided a surface treatment composition comprising, relative to 100% by weight of the solids content of the composition, 70 to 90% by weight of a resin mixture comprising 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% by weight of a melamine-based hardener; 0.5 to 10% by weight of an inorganic additive; 0.5 to 10% by weight of a silane coupling agent; 0.1 to 2% by weight of an adhesion promoter; 0.1 to 2% by weight of a coloring pigment; and 0.1 to 1% by weight of a pigment stabilizer.

[0013] According to one embodiment of the present invention, there is provided a surface-treated ternary hot-dip zinc alloy plated steel sheet, comprising: a steel sheet; a ternary hot-dip zinc alloy plating layer formed on at least one surface of the steel sheet; and a surface treatment film layer formed on the ternary hot-dip zinc alloy plating layer, the surface treatment film layer being formed from the surface treatment composition.

[0014] According to one embodiment of the present invention, there is provided a method for producing a surface-treated ternary hot-dip zinc alloy-plated steel sheet, the method including: coating the surface treatment composition on a ternary hot-dip zinc alloy-plated steel sheet having a ternary hot-dip zinc alloy plating layer formed thereon; and drying the surface treatment composition to form a surface treatment film layer. Effect of the Invention

[0015] The surface treatment composition according to the present invention is coated on a hot-dip zinc alloy-plated steel sheet to form a surface treatment film layer, thereby providing a hot-dip zinc alloy-plated steel sheet having excellent corrosion resistance, blackening resistance, alkali resistance, and unique surface color characteristics.

[0016] In addition, the surface treatment composition according to the present invention has excellent pigment dispersion stability, does not cause precipitation or aggregation even when used after long-term storage, and can impart excellent surface gloss to hot-dip zinc alloy plated steel sheets.

[0017] Furthermore, since the surface treatment composition according to the present invention does not contain any heavy metal components such as chromium, which are environmental pollutants, it is harmless to the human body and does not cause problems due to environmental pollution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, preferred embodiments of the present invention will be described with reference to various embodiments. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0019] The present invention relates to a surface treatment composition for ternary hot-dip zinc alloy-plated steel sheets, which has excellent solution stability, and when applied to ternary hot-dip zinc alloy-plated steel sheets, has excellent flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, alkali resistance, and excellent surface properties. The present invention also relates to a ternary hot-dip zinc alloy-plated steel sheet surface-treated with the surface treatment composition, and a method for producing the same.

[0020] A surface treatment composition according to one embodiment of the present invention can contain, relative to 100% by weight of the solids content of the composition, 70 to 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 acrylic-urethane auxiliary resin; 5 to 25% by weight of a melamine-based curing agent; 0.5 to 10% by weight of an inorganic additive; 0.5 to 10% by weight of a silane coupling agent; 0.1 to 2% by weight of an adhesion promoter; 0.1 to 2% by weight of a coloring pigment; and 0.1 to 1% by weight of a pigment stabilizer.

[0021] In one embodiment, the high molecular weight polysilicon modified polyurethane base resin is a component that can impart excellent corrosion resistance, water resistance, and solvent resistance to the ternary hot-dip zinc alloy plated steel sheet. The high molecular weight polysilicon modified polyurethane base resin can be synthesized from, but is not limited to, a silicone polymer and a polycarbonate polyol, and has a self-crosslinking property by using a trimer isocyanate polymer during synthesis.

[0022] The weight average molecular weight (Mw) of the high molecular weight polysilicon modified polyurethane base resin can be 100,000 to 200,000. If the weight average molecular weight is less than 100,000, it is difficult to ensure sufficient corrosion resistance, whereas if the weight average molecular weight exceeds 200,000, the solution stability decreases, the hardness of the film increases, and the processability decreases.

[0023] The glass transition temperature (Tg) of the high molecular weight polysilicon modified polyurethane base resin may be -20° C. to -10° C. If the glass transition temperature is less than -20° C., it is difficult to ensure sufficient corrosion resistance, whereas if the glass transition temperature exceeds -10° C., the solution stability decreases, the hardness of the coating increases, and the processability decreases.

[0024] In one embodiment, the low molecular weight polysilicon modified polyurethane auxiliary resin is a component that can impart softness to the ternary hot-dip zinc alloy plated steel sheet to improve processability and adhesion. The low molecular weight polysilicon modified polyurethane auxiliary resin can be synthesized from, but is not limited to, a silicone polymer and a polycarbonate polyol. Unlike the high molecular weight polysilicon modified polyurethane main resin, the low molecular weight polysilicon modified polyurethane auxiliary resin does not have the property of self-crosslinking.

[0025] The weight average molecular weight of the low molecular weight polysilicon modified polyurethane auxiliary resin may be 30,000 to 70,000. If the weight average molecular weight is less than 30,000, it is difficult to ensure sufficient corrosion resistance due to a decrease in density of the coating, whereas if the weight average molecular weight exceeds 70,000, the effect of imparting softness to the coating is insufficient, which may cause problems such as reduced processability and adhesion.

[0026] The glass transition temperature (Tg) of the low molecular weight polysilicon modified polyurethane auxiliary resin may be -30° C. to -20° C. If the glass transition temperature is less than -30° C., it is difficult to ensure sufficient corrosion resistance due to a decrease in density of the coating, whereas if the glass transition temperature exceeds -20° C., the coating is not sufficiently imparted with soft properties, which may cause problems such as reduced processability and adhesion.

[0027] In one embodiment, the acrylic-urethane auxiliary resin is a component for forming a dense film on the ternary hot-dip zinc alloy plated steel sheet and improving heat-resistant adhesion. The acrylic-urethane auxiliary resin may be a copolymer of an acrylic resin and a polycarbonate-based urethane resin. The acrylic resin may include one or more structural units selected from the group consisting of methyl methacrylate (MMA) and butyl acrylate (BA).

[0028] The weight-average molecular weight of the polycarbonate-based urethane resin may be 80,000 to 120,000. If the weight-average molecular weight is less than 80,000, the effect of improving the density and heat-resistant adhesion of the coating is insufficient, whereas if the weight-average molecular weight exceeds 120,000, the coating may be too hard, resulting in a problem of reduced processability.

[0029] The glass transition temperature (Tg) of the polycarbonate-based urethane resin may be 50° C. to 70° C. If the glass transition temperature is less than 50° C., the effect of improving heat-resistant adhesion is insufficient, whereas if the glass transition temperature exceeds 70° C., the coating may be too hard, resulting in reduced processability.

[0030] The resin mixture can be a mixture of high molecular weight polysilicon modified polyurethane main resin: low molecular weight polysilicon modified polyurethane auxiliary resin: acrylic-urethane auxiliary resin in a weight ratio of 1:4.5:4.5 to 9:0.5:0.5, preferably 1:0.5:0.5 to 9:0.5:0.5, more preferably 2:0.5:0.5 to 9:0.5:0.5. For example, high molecular weight polysilicon modified polyurethane main resin: low molecular weight polysilicon modified polyurethane auxiliary resin: acrylic-urethane auxiliary resin can be mixed and used in a weight ratio of 2:0.5:0.5, more preferably 1:0.5:0.5.

[0031] If the content of the high molecular weight polysilicon modified polyurethane base resin in the resin mixture is too low, the flat corrosion resistance, processed part corrosion resistance, and alkali resistance of the steel plate may be reduced. On the other hand, if the content of the high molecular weight polysilicon modified polyurethane base resin in the resin mixture is too high, the processed part corrosion resistance and blackening resistance of the steel plate may be reduced.

[0032] In one embodiment, the content of the resin mixture may be 70 to 90% by weight based on 100% by weight of the solid content of the surface treatment composition. If the content of the resin mixture is less than 70% by weight, it is difficult to ensure sufficient corrosion resistance and alkali resistance, and if the content of the resin mixture exceeds 90% by weight, the content of the curing agent and inorganic compound in the surface treatment composition becomes relatively small, so that problems such as reduced corrosion resistance and reduced solution stability may occur.

[0033] In one embodiment, the melamine-based hardener reacts with the base resin and auxiliary resin of the ternary zinc alloy-plated steel sheet surface treatment composition to form a dense cross-linked bond, thereby forming a strong coating film. The melamine-based hardener may contain at least one functional group selected from the group consisting of a methoxymethyl group, a methylol group, and an imino group, and the functional group may cross-link with the skeleton polymer resin containing a carboxyl group. In this case, the skeleton polymer resin refers to the base resin and auxiliary resin according to one embodiment of the present invention.

[0034] The content of the melamine-based hardener may be 5 to 25% by weight based on 100% by weight of the solid content of the surface treatment composition. If the content of the melamine-based hardener is less than 5% by weight, sufficient cross-linking cannot be formed, and improvement of physical properties cannot be expected, whereas if the content of the melamine-based hardener is more than 25% by weight, the stability of the solution is reduced due to excessive cross-linking, and a phenomenon of solidification over time may occur.

[0035] In one embodiment, the inorganic additive is a ternary hot-dip zinc alloy plating. Steel sheet surface treatment composition It is a component for imparting water resistance and blackening resistance to a ternary hot-dip zinc alloy plated steel sheet that is surface-treated using the inorganic additive. As the inorganic additive, one or more selected from the group consisting of silica sol, alumina sol, titania sol and zirconia sol can be used.

[0036] The content of the inorganic additive may be 0.5 to 10% by weight based on 100% by weight of the solid content of the surface treatment composition. If the content of the inorganic additive is less than 0.5% by weight, sufficient water resistance and blackening resistance cannot be ensured, and if the content of the inorganic additive exceeds 10% by weight, the effect of improving blackening resistance is slight, and problems such as reduced corrosion resistance may occur.

[0037] In one embodiment, the silane coupling agent is a component for modifying the water-soluble organic resin and carrying out a coupling reaction to form a strong bond between the water-soluble organic resin and the inorganic additive of the surface treatment composition. The content of the silane coupling agent may be 0.5 to 10% by weight based on 100% by weight of the solid content of the surface treatment composition. If the content of the silane coupling agent is less than 0.5% by weight, the amount of the silane coupling agent required for coupling bonding between the organic resin and the inorganic additive is insufficient, making it difficult to ensure corrosion resistance. If the content of the silane coupling agent is more than 10% by weight, there is a problem that unreacted silane coupling agent remains after the reaction with the organic resin, resulting in a decrease in corrosion resistance after processing.

[0038] As the silane coupling agent, one or more selected from the group consisting of vinyl methoxysilane, vinyl trimethoxysilane, vinyl epoxy silane, vinyl triepoxy silane, methyl trimethoxysilane, tetraethyl orthosilicate, tetramethyl orthosilicate, 3-aminopropyl triepoxy silane, 3-glycidoxypropyl trimethoxy silane, 3-glycidoxypropyl triethoxy silane, 3-mercaptopropyl trimethoxy silane, N-(1,3 dimethylbutylidene)-3-(triepoxysilane)-1-propanamine, N,N-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N-(β-aminoethyl)-γ-aminopropyl methyl dimethoxy silane, N-(β-aminoethyl)-γ-aminopropyl trimethoxy silane, γ-glycidoxypropyl triethoxy silane, γ-mercaptopropyl triethoxy silane, and N-[2-(vinylbenzylamino)ethyl]-3-aminopropyl trimethoxy silane can be used.

[0039] The silane coupling agent can be hydrolyzed by one or more acids selected from the group consisting of formic acid, acetic acid, phosphoric acid, hydrochloric acid, and nitric acid.

[0040] In one embodiment, the adhesion promoter is a component for improving the adhesion between the steel sheet and the resin to prevent peeling of the coating and to prevent moisture from penetrating into the plating layer in a high humidity environment. As the adhesion promoter, one or more selected from the group consisting of ester phosphate and ammonium phosphate can be used.

[0041] The content of the adhesion promoter may be 0.1 to 2 wt% based on 100 wt% of the solid content of the surface treatment composition. If the content of the adhesion promoter is less than 0.1 wt%, the effect of improving adhesion and preventing moisture penetration is insufficient, and if the content of the adhesion promoter exceeds 2 wt%, there is a problem that the solution stability of the surface treatment composition is reduced.

[0042] In one embodiment, the coloring pigment is a component for imparting a hue to the ternary hot-dip zinc alloy plated steel sheet to impart beautiful surface properties. As the coloring pigment, one or more types selected from the group consisting of one or more inorganic pigments selected from the group consisting of titanium, lead, iron, copper, and chromium; and azo-based organic pigments; can be used.

[0043] The content of the color pigment may be 0.1 to 2% by weight based on 100% by weight of the solid content of the surface treatment composition. If the content of the color pigment is less than 0.1% by weight, it is difficult to express a sufficient hue, and if the content of the color pigment is more than 2% by weight, problems such as reduced solution stability and corrosion resistance may occur.

[0044] In one embodiment, the pigment stabilizer is a component for capping the color pigment to uniformly disperse the color pigment in the coating, thereby improving the gloss of the coating. The pigment stabilizer may be, but is not limited to, a carboxyl-based polymer.

[0045] The content of the pigment stabilizer may be 0.1 to 1 wt% based on 100 wt% of the solid content of the surface treatment composition. If the content of the pigment stabilizer is less than 0.1 wt%, it is difficult to ensure sufficient solution stability, and if the content of the pigment stabilizer exceeds 1 wt%, there may be a problem that the gloss of the film is reduced due to excessive residual components in the film.

[0046] In one embodiment, the surface treatment composition includes water as a solvent for diluting each component, and the water may be deionized water or distilled water. The solvent is included as the balance other than each component of the present invention, and the content thereof may be 60 to 80% by weight. Furthermore, the surface treatment composition according to one embodiment may further include alcohol as an auxiliary solvent to ensure solution stability, and the alcohol may be ethanol or isopropyl alcohol. The alcohol may be included in an amount of 3 to 10% by weight of the total solvent.

[0047] A ternary hot-dip zinc alloy plated steel sheet surface-treated with a surface treatment composition containing a water-soluble organic resin and an inorganic compound according to one embodiment of the present invention has excellent corrosion resistance and blackening resistance as well as excellent surface hue and gloss. In addition, the surface treatment composition according to one embodiment of the present invention does not contain hexavalent chromium, which is a harmful environmental substance, and contains water-soluble organic resin and inorganic compound that are harmless to the human body as main components, thereby preventing damage to the human body and environmental pollution problems.

[0048] According to one embodiment of the present invention, there is provided a ternary hot-dip zinc alloy plated steel sheet which is surface-treated with the above-mentioned surface treatment composition.

[0049] Specifically, the surface-treated ternary hot-dip zinc alloy plated steel sheet may include a steel sheet, a ternary hot-dip zinc alloy plated layer formed on at least one surface of the steel sheet, and a surface treatment coating layer containing an organic resin and an inorganic compound formed on the ternary hot-dip zinc alloy plated layer.

[0050] The base steel sheet and the ternary hot-dip zinc alloy plating layer may include an Al-enriched layer formed at the interface, and the Al-enriched layer may have an area ratio of 70% to 100%. The ternary hot-dip zinc alloy plating layer may include 0.2 to 15% by weight of Al, 0.5 to 3.5% by weight of Mg, and the balance being Zn and inevitable impurities.

[0051] In one embodiment, the ternary hot-dip zinc alloy plated steel sheet includes an Al-enriched layer formed at the interface between the base iron and the Zn-Al-Mg alloy plated layer, and the area ratio of the Al-enriched layer may be 70% to 100%, more preferably 73% to 100%. Here, the area ratio means the ratio of the area of ​​the Al-enriched layer to the area of ​​the base iron when projected from the surface of the plated steel sheet in the thickness direction of the base iron and assuming a flat surface without considering three-dimensional bending, etc. When the area ratio of the Al-enriched layer is ensured to be 70% or more, the Al-enriched layer has a form in which fine particles are continuously formed, and the platability and plating adhesion can be significantly improved.

[0052] In the ternary hot-dip zinc alloy plated steel sheet according to the embodiment of the present invention, Mg plays a very important role in improving the corrosion resistance of the ternary hot-dip zinc alloy plated steel sheet, and effectively prevents the corrosion of the ternary hot-dip zinc alloy plated steel sheet by forming a dense zinc hydroxide-based corrosion product on the surface of the plated layer in a corrosive environment. In the present invention, in order to ensure the intended corrosion resistance effect, the plated layer needs to contain 0.5 wt% or more of Mg, more preferably 0.9 wt% or more. However, if the content is excessive, Mg oxidized dross will rapidly increase on the surface of the plated bath, offsetting the oxidation prevention effect of the addition of trace elements. In order to prevent this, the plated layer needs to contain 3.5 wt% or less of Mg, more preferably 3.2 wt% or less of Mg.

[0053] In a ternary hot-dip zinc alloy plated steel sheet according to one embodiment of the present invention, Al suppresses the formation of Mg oxide dross in the plating bath and reacts with Zn and Mg in the plating bath to form a Zn-Al-Mg intermetallic compound, thereby improving the corrosion resistance of the plated steel sheet. To obtain the above effects, the plating layer needs to contain 0.2 wt% or more of Al, more preferably 0.9 wt% or more. However, if the content is excessive, the weldability and phosphating property of the plated steel may deteriorate. To prevent this, the plating layer needs to contain 15 wt% or less of Al, more preferably 12 wt% or less of Al.

[0054] The surface treatment film layer containing the organic resin and inorganic compound can be formed from a surface treatment composition containing 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 acrylic-urethane auxiliary resin, 5-25% by weight of a melamine-based hardener, 0.5-10% by weight of an inorganic additive, 0.5-10% by weight of a silane coupling agent, 0.1-2% by weight of an adhesion promoter, 0.1-2% by weight of a coloring pigment, and 0.1-1% by weight of a pigment stabilizer, based on 100% by weight of the solid content of the composition. The surface treatment composition has the same technical features as those described above, so a redundant description will not be given.

[0055] In one embodiment, the surface treatment film layer is a coating layer formed by drying the above-mentioned surface treatment composition, and corresponds to the components remaining after all the volatile substances contained in the surface treatment film layer containing the organic resin and the inorganic compound have evaporated. As a result, the surface treatment film layer containing the organic resin and the inorganic compound does not contain water or alcohol as a solvent, and also does not contain the solvent contained in the surface treatment components containing the organic resin and the inorganic compound. Therefore, the components contained in the surface treatment film layer containing the organic resin and the inorganic compound correspond to the content based on 100% by weight of the total solid content.

[0056] According to one embodiment of the present invention, there is provided a method for producing a surface-treated ternary hot-dip zinc alloy-plated steel sheet, the method including: coating the above-mentioned surface treatment composition on a ternary hot-dip zinc alloy-plated steel sheet having a ternary hot-dip zinc alloy plating layer formed thereon; and drying the surface treatment composition to form a surface treatment film layer.

[0057] In one embodiment, the surface treatment composition may be coated to a thickness of 2.5 to 50 μm. The coated surface treatment composition is dried to form a dry coating layer, and the dry coating layer may have a thickness of 1 to 10 μm. If the coating thickness of the surface treatment composition is less than 2.5 μm, the surface treatment composition may be applied too thinly to the acid sites of the steel sheet roughness, resulting in a problem of reduced corrosion resistance. If the thickness exceeds 50 μm, the coating layer may be formed too thick, resulting in poor workability, and an economic problem may occur due to increased costs for solution treatment.

[0058] The method for coating the surface treatment composition is not particularly limited as long as it is a commonly used coating method. For example, it is preferable to coat the surface treatment composition by any one of a roll coating method, a spray method, a dipping method, a spray squeegee method, and a dipping squeegee method.

[0059] The process of drying the surface treatment composition coated on the ternary hot-dip zinc alloy plated steel sheet is preferably carried out at a temperature of 70 to 250°C based on the PMT of the base steel sheet. If the drying temperature is less than 70°C based on the PMT of the base steel sheet, the curing reaction of the organic resin may not be completed, a strong film structure may not be formed, and corrosion resistance and alkali resistance may be deteriorated. On the other hand, if the drying temperature exceeds 250°C based on the PMT of the base steel sheet, work productivity may be reduced due to the generation of water vapor and fumes during the water cooling process, and the surface quality of the product may be deteriorated due to the condensation phenomenon in which evaporated water vapor is condensed on the upper part of the drying equipment.

[0060] Meanwhile, the drying process is preferably carried out in a hot air drying oven or an induction heating oven. When the surface treatment composition is dried using a hot air drying oven, the internal temperature of the hot air drying oven is preferably 100 to 300°C. When the surface treatment composition is dried using an induction heating oven, the current applied to the induction heating oven is preferably 1000 to 5000A, more preferably 1500 to 3500A. When the internal temperature of the hot air drying oven is less than 100°C or the current applied to the induction heating oven is less than 1000A, the curing reaction of the surface treatment composition may not be complete, and the corrosion resistance and alkali resistance may be poor. In addition, when the internal temperature of the hot air drying oven exceeds 300°C or the current applied to the induction heating oven exceeds 5000A, the work productivity may be reduced due to the generation of water vapor and fumes during the water cooling process, and the surface quality of the product may be deteriorated due to the condensation phenomenon in which evaporated water vapor is condensed on the upper part of the drying equipment.

[0061] In addition, the surface treatment composition is dried to form a surface treatment film layer, and then the surface treatment film layer is water-cooled to provide a finally surface-treated ternary hot-dip zinc alloy plated steel sheet.

[0062] The method for producing a ternary hot-dip zinc alloy plated steel sheet according to an embodiment of the present invention may be carried out in a continuous process, and the speed of the continuous process is preferably 80 to 120 mpm. If the speed of the continuous process is less than 80 mpm, a problem of reduced productivity may occur, and if it exceeds 120 mpm, the solution may be scattered during the process of drying the surface treatment composition, causing surface defects. EXAMPLES

[0063] (Example) "Production of test specimens" The ternary hot-dip zinc alloy-coated steel sheet (coating amount per side: 0.5 to 2.0 g / m2) is made of ternary hot-dip zinc alloy coating layer consisting of, by weight, 1.5% Mg, 1.5% Al, and the balance Zn. 2 After cutting the specimens to a size of 7cm x 15cm (horizontal x vertical) and removing the oil, the resulting compositions were applied to hot-dip zinc alloy plated steel sheets using a bar coater. Then, the specimens were cured at a PMT (Peak Metal Temperature) of 180±20℃ to prepare test specimens.

[0064] "Testing and Evaluation Methods" The methods and criteria for evaluating the physical properties of the steel sheets surface-treated in the present examples are as follows. <Reputation for corrosion resistance> After treating the test pieces according to the method specified in ASTM B117, the rate of white rust formation on the steel sheets over time was measured, with the following evaluation criteria: ◎: It took more than 144 hours for white rust to appear ○: Time taken for white rust to appear was 96 hours or more but less than 144 hours △: Time taken for white rust to appear was between 55 and 96 hours. ×: Time required for white rust to appear is less than 55 hours <Corrosion resistance of processed parts> The test piece was pushed up to a height of 6 mm using an Erichsen tester, 48After the time had passed, the degree of white rust generation was measured, and the evaluation criteria were as follows: ◎: After 48 hours, the area where white rust has formed is less than 5% △: After 48 hours, the area of ​​white rust is 5% to less than 7%. ×: After 48 hours, white rust has formed on 7% or more of the area <Blackening resistance> The test piece was left in a thermohygrostat maintained at 50°C and a relative humidity of 95% for 120 hours, and the hue change (color difference: ΔE) of the test piece before and after the test was observed. The evaluation criteria were as follows: ◎: ΔE≦2 ○:2<ΔE≦3 △:3<ΔE≦4 ×:ΔE>4 <Alkaline resistance> The test piece was immersed in an alkaline degreasing solution at 60℃ for 2 minutes, then washed with water and air-blowing, after which the color difference (ΔE) before and after was measured. The alkaline degreasing solution used was Daihan Parkerizing Finecleaner L 4460 A: 20g / 2.4L + L 4460 B 12g / 2.4L (pH=12). The evaluation criteria were as follows: ◎:ΔE≦2 ○:2<ΔE≦3 △:3<ΔE≦4 ×:ΔE>4 <Solution stability> The surface treatment composition was placed in a container and placed in a thermostatic oven at 50° C. for 7 days, after which the presence or absence of precipitation was visually observed and the change in viscosity was measured. The evaluation criteria were as follows: ○: No precipitation, viscosity change less than 1 cP △: No precipitation, viscosity change of 1 cP to less than 5 cP ×: Precipitation or viscosity change of 5 cP or more

[0065] "Components of surface treatment composition" The components of the surface treatment compositions used in the examples are as follows: -High molecular weight polysilicon modified polyurethane base resin: Polyurethane resin with a weight average molecular weight of 150,000 -Low molecular weight polysilicon modified polyurethane auxiliary resin (auxiliary resin 1): Polyurethane resin with a weight average molecular weight of 50,000 - Acrylic-urethane auxiliary resin (auxiliary resin 2): A copolymer resin of an acrylic resin containing structural units of methyl methacrylate (MMA) and butyl acrylate (BA) and a polycarbonate-based urethane resin with a weight-average molecular weight of 100,000. - Hardener: Melamine hardener (CYMEL 303) -Inorganic additive: Titania sol compound -Silane coupling agent: A silane coupling agent made by mixing vinyltriepoxysilane, methyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane in a weight ratio of 1:1:1 -Adhesion promoter: Phosphate ester compound -Color pigment: Azo organic pigment -Pigment stabilizer: Carboxyl polymer -Solvent: A mixture of water and ethanol

[0066] (Example 1: Changes in physical properties depending on the content of resin mixture) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 1. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0067] The solution stability of the surface treatment composition prepared above was evaluated. In addition, after the surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the test specimen were evaluated. The evaluation results are shown in Table 1 below.

[0068] [Table 1]

[0069] Referring to Table 1 above, Examples 1 to 3, in which the resin mixture content satisfies the content proposed by the present invention, showed good (◯) or better results in all physical properties. However, Comparative Example 1, which contained too little resin mixture, showed poor results in flat plate corrosion resistance, processed part corrosion resistance, and alkali resistance, and Comparative Example 2, which contained too much resin mixture, showed poor results in flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and solution stability.

[0070] (Example 2: Changes in physical properties depending on the content ratio of main resin and auxiliary resin) A surface treatment composition was prepared containing 80% by weight of a resin mixture containing the above-mentioned main resin, auxiliary resin 1, and auxiliary resin 2, 10% by weight of a curing agent, 4% by weight of an inorganic additive, 4% by weight of a silane coupling agent, 0.5% by weight of an adhesion promoter, 1% by weight of a coloring pigment, and 0.5% by weight of a pigment stabilizer. The surface treatment composition used a mixed solvent of water and ethanol as the solvent.

[0071] In the above resin mixture, the main resin, auxiliary resin 1, and auxiliary resin 2 were mixed in the weight ratio shown in Table 2 below.

[0072] After the above surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the test specimen were evaluated, and the evaluation results are shown in Table 2 below.

[0073] [Table 2]

[0074] Referring to Table 2, Examples 4 to 7, in which the weight ratio of the main resin to the auxiliary resin satisfies the content ratio proposed by the present invention, showed good (◯) or better results in all physical properties. On the other hand, Comparative Example 3, which contained too little water-soluble main resin, showed poor results in flat plate corrosion resistance, processed part corrosion resistance, and alkali resistance, and Comparative Example 4, which contained too little Auxiliary Resin 1 and Auxiliary Resin 2, showed poor results in processed part corrosion resistance and blackening resistance.

[0075] (Example 3: Changes in physical properties depending on the content of hardener) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 3. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0076] The solution stability of the surface treatment composition prepared above was evaluated. In addition, after the surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the test specimen were evaluated. The evaluation results are shown in Table 3 below.

[0077] [Table 3]

[0078] Referring to Table 3, Examples 8 to 10, which contain the melamine-based hardener as proposed by the present invention, showed good (◯) or better results in all physical properties. On the other hand, Comparative Example 5, which contains too little melamine-based hardener, showed poor results in all physical properties except for solution stability, and Comparative Example 6, which contains too little melamine-based hardener, showed poor results in alkali resistance and solution stability.

[0079] (Example 4: Changes in physical properties depending on the content of inorganic additives) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 4. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0080] The solution stability of the surface treatment composition prepared above was evaluated. In addition, after the surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the test specimen were evaluated. The evaluation results are shown in Table 4 below.

[0081] [Table 4]

[0082] Referring to Table 4 above, Examples 11 to 13 of the present invention, which contain inorganic additives satisfying the content suggested by the present invention, showed good (◯) or better results in all physical properties. On the other hand, Comparative Example 7, which contains too little inorganic additives, showed poor results in flat plate corrosion resistance, processed part corrosion resistance, and blackening resistance, and Comparative Example 8, which contains too much inorganic additives, showed poor results in flat plate corrosion resistance and processed part corrosion resistance.

[0083] (Example 5: Changes in physical properties depending on the content and type of silane coupling agent) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 5. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0084] The solution stability of the surface treatment composition prepared above was evaluated. In addition, after the surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the test specimen were evaluated. The evaluation results are shown in Table 5 below.

[0085] [Table 5]

[0086] Referring to Table 5, inventive examples 14 to 16, in which the content of the silane coupling agent satisfies the content proposed by the present invention, showed good (◯) or better results in all physical properties. On the other hand, comparative example 9, which contained too little silane coupling agent, showed poor results in flat plate corrosion resistance, processed part corrosion resistance, and blackening resistance, and comparative example 10, which contained too much silane coupling agent, showed high dryness of the film, forming a hard film, Corrosion resistance of processed parts However, the coating was brittle and showed poor resistance to blackening.

[0087] On the other hand, a surface treatment composition having the composition according to the above-mentioned Example 15 of the present invention was prepared by changing the silane coupling agent to the silane coupling agent shown in Table 6 below, and a test piece was prepared in the same manner as described above. The flat plate corrosion resistance was evaluated, and the results are shown in Table 6.

[0088] [Table 6] TIFF0007684388000007.tif161158

[0089] Referring to Table 6, inventive examples 17 to 50, the plate corrosion resistance was good (◯) or excellent (◎). In particular, inventive example 46, which used 3-glycidoxypropyltrimethoxysilane, vinyltriepoxysilane and methyltrimethoxysilane in a weight ratio of 2:1:2, the area of ​​white rust generated after 144 hours or more was 0%, which was the best result.

[0090] (Example 6: Changes in physical properties depending on the content of adhesion promoter) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 7. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0091] The solution stability of the surface treatment composition prepared above was evaluated. In addition, after the surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance of the test specimen were evaluated. The evaluation results are shown in Table 7 below.

[0092] [Table 7]

[0093] Referring to Table 7, Examples 51 to 53, which contain the adhesion promoter as proposed by the present invention, showed good (◯) or better results in all physical properties. However, Comparative Example 11, which contains too little adhesion promoter, showed poor results in terms of flat plate corrosion resistance, processed part corrosion resistance, and Resistance to blackening showed poor results, and Comparative Example 12, which contained too much adhesion promoter, showed poor solution stability.

[0094] (Example 7: Changes in physical properties depending on the content of color pigment) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 8. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0095] The solution stability of the surface treatment composition prepared above was evaluated. In addition, the surface treatment composition was applied to the above-mentioned test specimen, and the test specimen was evaluated for flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, and alkali resistance. The degree of surface color expression was evaluated by visually observing the test specimen treated with the surface treatment composition, and the degree of color expression was classified into excellent (◎), good (○), and poor (X). The evaluation results are shown in Table 8 below.

[0096] [Table 8]

[0097] Referring to Table 8 above, Examples 54 to 56, which contain the color pigment as proposed by the present invention, showed good (◯) or better results in all physical properties. However, Comparative Example 13, which contains too little color pigment, showed poor results in the expression of surface hue, and Comparative Example 14, which contains too much color pigment, showed poor results in plate corrosion resistance, processed part corrosion resistance, and solution stability.

[0098] (Example 8: Changes in physical properties depending on the content of pigment stabilizer) A surface treatment composition was 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 inorganic additive, a silane coupling agent, an adhesion promoter, a color pigment, and a pigment stabilizer in the amounts shown in Table 9. The surface treatment composition used a mixed solvent of water and ethanol as a solvent.

[0099] The solution stability of the surface treatment composition produced above was evaluated. In addition, after the surface treatment composition was applied to the above-mentioned test specimen, the flat plate corrosion resistance, processed part corrosion resistance, blackening resistance, alkali resistance, and gloss of the test specimen were evaluated. The gloss was measured using a gloss meter at an incidence angle of 60° on the test specimen treated with the surface treatment composition. If the measurement result was 80 or more, it was considered good (○), and if it was less than 80, it was considered poor (X). The evaluation results are shown in Table 9 below.

[0100] [Table 9]

[0101] Referring to Table 9, Examples 57 to 59, which contain the pigment stabilizer content as proposed by the present invention, showed good (◯) or better results in all physical properties. However, Comparative Example 15, which contains too little pigment stabilizer, showed poor solution stability, and Comparative Example 16, which contains too much pigment stabilizer, showed poor gloss.

[0102] (Example 9: Changes in physical properties depending on the thickness of the coating layer and drying temperature) The surface treatment composition according to Example 2 of the invention was bar-coated on a test specimen and dried in a hot air drying oven. However, in the above surface treatment composition, the resin mixture was prepared by mixing the main resin, auxiliary resin 1, and auxiliary resin 2 according to Example 6 of the invention. 67:16.5:16.5 The silane coupling agent used was a mixture of 3-glycidoxypropyltrimethoxysilane, vinyltriepoxysilane and methyltrimethoxysilane in a weight ratio of 2:1:2 according to Invention Example 46.

[0103] The coating layer thickness and PMT temperature were controlled as listed in Table 10 below.

[0104] [Table 10]

[0105] As shown in Table 10 above, inventive examples 60 to 63 in which a coating layer having a thickness of 1 to 10 μm was formed showed results of good (◯) or better in all physical properties. On the other hand, comparative example 17 in which the coating was too thin showed results of average (△) in flat plate corrosion resistance, blackening resistance, and alkali resistance, and showed a poor result in processed part corrosion resistance. On the other hand, comparative example 18 in which a coating was formed that was too thick showed a poor result in processed part corrosion resistance, and did not have improved physical properties compared to inventive example 63, so from an economical perspective, a coating thickness of more than 10 μm is not required. On the other hand, as shown in Table 10 above, inventive examples 64 to 66 in which a coating layer was formed by drying the coating at 70 to 250° C. showed results of good (◯) or better in all physical properties. On the other hand, comparative example 19 in which the drying temperature was very low showed poor results in all physical properties because the coating was not sufficiently dried. On the other hand, Comparative Example 20, in which the drying temperature was very high, showed poor blackening resistance due to fume drops on the steel sheet caused by condensation of water vapor generated on the steel sheet during the air cooling process (water cooling). Although the examples of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and it is obvious to a person skilled in the art that various modifications and variations are possible within the scope of the technical idea of ​​the present invention described in the claims.

Claims

1. Based on 100% by weight of the solid content of the composition, 70 - 90% by weight of a resin mixture containing a high molecular weight polysilicon - modified polyurethane main resin with a weight - average molecular weight (Mw) of 100,000 - 200,000, a low molecular weight polysilicon - modified polyurethane auxiliary resin with a weight - average molecular weight (Mw) of 30,000 - 70,000, and an acrylic - urethane auxiliary resin; 5 - 25% by weight of a melamine - based curing agent; 0.5 - 10% by weight of an inorganic additive containing one or more selected from the group consisting of silica sol, alumina sol, titania sol, and zirconia sol; 0.5 - 10% by weight of a silane coupling agent; 0.1 - 2% by weight of an adhesion promoter selected from the group consisting of ester phosphate and ammonium phosphate; 0.1 - 2% by weight of a coloring pigment which is an azo - based organic pigment; and 0.1 - 1% by weight of a pigment stabilizer which is a carboxyl - based polymer, 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 in a weight ratio of 1:4.5:4.5 - 9:0.5:0.5, a surface - treatment composition.

2. The high molecular weight polysilicon - modified polyurethane main resin has a glass transition temperature (Tg) of - 20°C to - 10°C, the surface - treatment composition according to Claim 1.

3. The low molecular weight polysilicon - modified polyurethane auxiliary resin has a glass transition temperature (Tg) of - 30°C to - 20°C, the surface - treatment composition according to Claim 1.

4. The acrylic - urethane auxiliary resin is an acrylic resin containing one or more structural units selected from the group consisting of methyl methacrylate (MMA) and butyl acrylate (BA), and a polycarbonate - based urethane resin is copolymerized, the surface - treatment composition according to Claim 1.

5. 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 - 120,000, the surface - treatment composition according to Claim 4.

6. The melamine - based curing agent contains one or more functional groups selected from the group consisting of a methoxymethyl group, a methylol group, and an imino group, The functional group cross - links a resin containing a carboxyl group, the surface - treatment composition according to Claim 1.

7. The silane coupling agent in the surface treatment composition according to claim 1 contains 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.

8. The surface treatment composition according to claim 7, 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.

9. The surface treatment composition further contains a solvent. The surface treatment composition according to any one of claims 1 to 8, wherein the solid content is 20 to 40% by weight based on the total weight of the surface treatment composition, and the balance is the solvent.

10. The surface treatment composition according to claim 9, wherein the solvent contains 3 to 10% by weight of alcohol and the balance of water based on the total weight of the solvent.

11. Steel sheet; A ternary molten zinc alloy plating layer formed on at least one surface of the steel sheet; and A surface treatment coating layer formed on the ternary molten zinc alloy plating layer, The surface treatment coating layer is formed from the surface treatment composition according to any one of claims 1 to 8, and the surface-treated ternary molten zinc alloy plated steel sheet.

12. The ternary molten zinc alloy plating layer contains an Al-enriched layer formed at the interface. The surface-treated ternary molten zinc alloy plated steel sheet according to claim 11, wherein the occupation area ratio of the Al-enriched layer is 70% to 100%.

13. The ternary molten zinc alloy plating layer contains Al: 0.2 to 15% by weight, Mg: 0.5 to 3.5% by weight, the balance being Zn and inevitable impurities, and is the surface-treated ternary molten zinc alloy plating steel sheet according to claim 11.

14. The surface treatment coating layer has a thickness of 1 μm to 10 μm, and is the surface-treated ternary molten zinc alloy plating steel sheet according to claim 11.

15. Coating the surface treatment composition according to any one of claims 1 to 8 on a ternary molten zinc alloy plating steel sheet on which a ternary molten zinc alloy plating layer is formed; and A method for manufacturing a surface-treated ternary molten zinc alloy plating steel sheet, comprising the step of drying the surface treatment composition to form a surface treatment coating layer.

16. The method for manufacturing a surface-treated ternary molten zinc alloy plating steel sheet according to claim 15, wherein the surface treatment composition is coated with a thickness of 2.5 μm to 50 μm.

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