Solution composition for surface treatment of plated steel sheet, plated steel sheet surface-treated with said solution composition, and method for producing same

Abstract

The present invention relates to a surface treatment solution composition capable of improving corrosion resistance, lubricity and the like of a zinc-plated alloy steel sheet, a plated steel sheet surface-treated with the surface treatment solution composition, and a method for manufacturing the plated steel sheet.

Description

Technical Field

[0001] The present invention relates to a surface treatment solution composition capable of improving the lubricity, corrosion resistance, etc. of a plated steel sheet used for building materials and the like, a plated steel sheet surface-treated with the surface treatment solution composition, and a method for manufacturing the plated steel sheet. Background Art

[0002] Plated steel sheets used for building materials and the like are required to have high corrosion resistance. As an example, high-corrosion-resistant hot-dip plated steel sheets formed with a coating layer containing zinc (Zn), magnesium (Mg), and aluminum (Al) are widely used. It is known that such high-corrosion-resistant hot-dip plated steel sheets have excellent red rust corrosion resistance.

[0003] However, most of the exposed surface of such high-corrosion-resistant hot-dip plated steel sheets is composed of zinc or a zinc alloy. Therefore, when exposed to a general environment, especially when exposed to a humid atmosphere, pitting corrosion defects are likely to occur on the surface, and thus there is a disadvantage in that the appearance deteriorates.

[0004] To solve such problems, most plated steel sheets apply a surface treatment solution to the surface to inhibit the formation of white rust caused by corrosion of the coating layer. In the past, hexavalent chromium or chromate treatment was performed on the plated steel sheet to ensure corrosion resistance and blackening resistance. However, since hexavalent chromium is designated as a substance harmful to the environment, the control of the use of hexavalent chromium is currently being strengthened. In addition, when hexavalent chromium is used as a surface treatment agent for plated steel sheets, there are problems such as blackening of the steel sheet surface or generation of black spots.

[0005] Therefore, a method of ensuring the corrosion resistance and blackening resistance of a plated steel sheet by applying a surface treatment solution composition containing trivalent chromium to the plated steel sheet is currently being applied. For example, in Patent Documents 1 to 3, a method of ensuring corrosion resistance and blackening resistance by immersing a steel sheet in a composition containing trivalent chromium for chemical conversion treatment is used. However, in terms of application to the continuous process of a steel company, the immersion time is long, and there are problems such as a decrease in fingerprint resistance in the chemical conversion treatment method.

[0006] In addition, Patent Documents 4 and 5 disclose that a chromium-containing composition is applied to a plated steel sheet by using a spraying or roll coating method, so that it can be applied to the continuous production line of a steel company and fingerprint resistance can be ensured. However, since these compositions contain a porous silica component, they are not suitable for Mg, Al-based alloys that are severely discolored in a humid atmosphere. In addition, porous silica has strong hygroscopic properties, so there is a problem of causing rapid discoloration in Zn-Mg-Al-based alloy steel sheets.

[0007] (Patent Document 1) Korean Patent Publication No. 10-2006-0123628

[0008] (Patent Document 2) Korean Patent Publication No. 10-2005-0052215

[0009] (Patent Document 3) Korean Patent Publication No. 10-2010-0106031

[0010] (Patent Document 4) Korean Patent Publication No. 10-2004-0046347

[0011] (Patent Document 5) Japanese Patent Publication No. 2002-069660 Summary of the Invention

[0012] (I) Technical Problem to be Solved

[0013] An object of one aspect of the present invention is to provide a solution composition, a plated steel sheet surface-treated with the solution composition, and a method for manufacturing the plated steel sheet, wherein, by controlling the composition of the coating solution applied to the surface of the plated steel sheet, preferably the surface of a ternary alloy plated steel sheet, the generation of white rust at the initial stage of corrosion is suppressed, and finally, by sacrificing corrosion prevention, the reduction rate of the coating layer is reduced, and the corrosion rate of the base iron is reduced, thereby improving long-term corrosion resistance.

[0014] The technical problem of the present invention is not limited to the above. The technical problem of the present invention can be understood from the entire content of this specification, and those skilled in the technical field to which the present invention pertains can easily understand additional technical problems of the present invention.

[0015] (II) Technical Solution

[0016] One embodiment of the present invention provides a solution composition for surface treatment, the solution composition for surface treatment comprising: 1-10% by weight of a trivalent chromium compound, 0.1-5% by weight of an acidity regulator, 1-20% by weight of an adhesion improver, 1-20% by weight of a corrosion resistance improver, 0.1-5.0% by weight of a pitting corrosion improver, 1-10% by weight of a long-term corrosion resistance improver, 0.1-3.0% by weight of a lubricant, 1-20% by weight of a co-solvent, and the balance being a solvent.

[0017] The trivalent chromium compound may be one or more selected from chromium sulfate, chromium nitrate, chromium phosphate, chromium fluoride, and mixtures thereof.

[0018] The acidity regulator may be one or more selected from phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, (NH4)H2PO4, (NH4)2HPO4, NaH2PO4, Na2HPO4, phytic acid, glycolic acid, lactic acid, acetic acid, oxalic acid, and mixtures thereof.

[0019] The adhesion improver may be selected from vinylmethoxysilane, vinyltrimethoxysilane (VTMS), vinyltriethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methylglycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxytriethyldimethoxysilane, N-(3-(trimethoxysilyl)propyl)ethylenediamine (AEAPTMS), 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldiethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, 3-(2,(3-Epoxypropoxy)propylmethyldimethoxysilane), 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl-3-aminopropyl)methyldimethoxysilane, N-(2-aminoethyl-3-aminopropyl)trimethoxysilane, diethylenetriaminopropyltrimethoxysilane, 3-ureidopropyltrimethoxysilane, N-phenylaminopropyltrimethoxysilane, (3-glycidyloxypropyl)trimethoxysilane (GPTMS), methyltrimethoxysilane (MTMS), and one or more of their mixtures.,

[0020] The corrosion resistance improver may be one or more selected from vanadyl acetylacetonate, ammonium metavanadate, potassium metavanadate, sodium metavanadate, vanadium trioxide, vanadium acetoacetate, ammonium metavanadate, silicon oxide, and their mixtures.

[0021] The pitting improver may be one or more selected from ethylenediamine, hexamethylenediamine, trimethylamine, methylamine, diphenylamine, ethyleneamine, aniline, toluidine, piperidine, aziridine, pyridine, alanine, propylamine, diisopropylamine, monoisopropylamine, dibutylamine, dipropylamine, and their mixtures.

[0022] The long-term corrosion inhibitor can be one or more selected from anhydrous chromium chloride, chromium chloride pentahydrate, chromium chloride hexahydrate, chromium chloride nonahydrate, and mixtures thereof.

[0023] The lubricant can be one or more selected from polytetrafluoroethylene (PTFE), polyethylene (PE), carnauba wax, and mixtures thereof.

[0024] The cosolvent can be one or more selected from ethanol, isopropanol, methanol, tallow alcohol, 2-butoxyethanol, diethylene glycol monobutyl ether, and mixtures thereof.

[0025] The solvent can be water.

[0026] Another embodiment of the present invention provides a surface-treated plated steel sheet, which includes: a steel sheet; a plating layer formed on at least one surface of the steel sheet; and a surface treatment coating formed on the plating layer, wherein the surface treatment coating is formed from the above solution composition.

[0027] By weight percentage, the plating layer can contain: magnesium (Mg): 4.0 - 7.0%, aluminum (Al): 11.0 - 19.5%, and the balance of Zn and other inevitable impurities.

[0028] The plating layer can satisfy the following relationship 1.

[0029] [Relationship 1]

[0030] 0.26 ≤ I(110) / I(103) ≤ 0.65

[0031] (In relationship 1, I(110) represents the X-ray diffraction integrated intensity of the (110) plane crystal peak of the MgZn2 phase, and I(103) represents the X-ray diffraction integrated intensity of the (103) plane crystal of the MgZn2 phase.)

[0032] The surface treatment coating can have a thickness of 0.1 - 2.0 μm.

[0033] Another embodiment of the present invention provides a method for manufacturing a surface-treated plated steel sheet, the manufacturing method including the following steps: providing a plated steel sheet having a plating layer formed on at least one surface; performing a coating treatment on the plating layer with the above solution composition; and drying the steel sheet subjected to the coating treatment.

[0034] The coating treatment can be carried out by any method selected from bar coating, roll coating, spraying, dipping, jet extrusion, and dip extrusion.

[0035] The drying can be carried out in a temperature range of 40 - 280°C based on the final reached temperature (PMT) of the steel plate.

[0036] (III) Beneficial effects

[0037] According to the present invention, a solution composition for surface treatment can be provided, which slows down the generation of white rust in the initial stage of corrosion by adjusting the composition of the coating solution applied to the surface of a highly corrosion-resistant plated steel sheet, and finally reduces the loss rate of the plating layer by sacrificial anti-corrosion, thereby reducing the corrosion rate of the base iron, and has the effect of improving long-term corrosion resistance.

[0038] In addition, according to the present invention, a highly corrosion-resistant plated steel sheet with excellent flat corrosion resistance, processing corrosion resistance, tube oil erosion resistance, alkali resistance, pitting corrosion resistance, blackening resistance, and long-term corrosion resistance and without generating foreign object defects can be provided.

[0039] The various beneficial advantages and effects of the present invention are not limited to the above content, and the various beneficial advantages and effects of the present invention will be more easily understood during the process of describing the specific implementation embodiments of the present invention. Best mode for carrying out the invention

[0040] The terms used in this specification are for explaining the present invention and are not intended to limit the present invention. In addition, unless the relevant definitions show a clearly opposite meaning, the singular forms used in this specification also include the plural forms.

[0041] The meaning of "comprising" or "including" used in the specification is to specify the composition and does not exclude the existence or addition of other compositions.

[0042] Unless otherwise defined, 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. The terms defined in the dictionary are interpreted to conform to the meaning of the relevant technical literature and the currently disclosed content.

[0043] Hereinafter, the present invention will be described in detail.

[0044] First, a solution composition for surface treatment of a plated steel sheet according to one aspect of the present invention will be specifically described.

[0045] The solution composition according to the present invention may comprise: 1-10% by weight of a trivalent chromium compound, 0.1-5% by weight of an acidity regulator, 1-20% by weight of an adhesion improver, 1-20% by weight of a corrosion resistance improver, 0.1-5.0% by weight of a pitting corrosion improver, 1-10% by weight of a long-term corrosion resistance improver, 0.1-3.0% by weight of a lubricant, 1-20% by weight of a co-solvent, and the balance being a solvent.

[0046] The content of the solution composition of the present invention is based on a total of 100% by weight.

[0047] Specifically described below, the solution composition may form a coating on at least one surface of a substrate of a coatable composition. In the present invention, the substrate may be the plated steel sheet described above, for example, it may be a galvanized steel sheet, and as a non-limiting example, it may be a Zn-Mg-Al ternary alloy plated steel sheet.

[0048] Hereinafter, each component constituting the solution composition will be described in detail.

[0049] 1-10% by weight (hereinafter, %) of a trivalent chromium compound

[0050] The trivalent chromium compound mainly forms an insoluble film on the surface of the steel sheet, thereby improving corrosion resistance through the barrier effect.

[0051] In the solution composition of the present invention, when the content of the trivalent chromium compound is less than 1%, a strong insoluble film cannot be sufficiently formed, so moisture penetrating to the surface of the steel sheet cannot be effectively blocked, and thus corrosion resistance cannot be ensured. On the other hand, when the content of the trivalent chromium compound exceeds 10%, foreign matter defects may occur due to excessive chromium components.

[0052] In the present invention, the type of the trivalent chromium compound is not particularly limited, but preferably it may be at least one selected from chromium sulfate, chromium nitrate, chromium phosphate, chromium fluoride, and mixtures thereof.

[0053] 0.1-5% of an acidity regulator

[0054] The acidity regulator in the solution composition of the present invention adjusts the pH of the solution so that the components in the composition stably exist in the solution and react appropriately under coating conditions, thereby playing a role in stably forming a film.

[0055] When the content of such an acidity regulator is less than 0.1%, the pH of the solution increases, and thus the solution stability may decrease. On the other hand, when the content of such an acidity regulator exceeds 5%, corrosion resistance etc. may not be ensured due to residual acid after drying.

[0056] In the present invention, the type of the acidity regulator is not particularly limited, but preferably it may be one or more selected from phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, (NH4)H2PO4, (NH4)2HPO4, NaH2PO4, Na2HPO4, phytic acid, glycolic acid, lactic acid, acetic acid, oxalic acid, and mixtures thereof.

[0057] 1 - 20% of the adhesion improver

[0058] The adhesion improver in the solution composition of the present invention combines with the trivalent chromium compound, etc., and combines with the steel plate, thereby playing a role in improving the adhesion and corrosion resistance of the coating, etc.

[0059] When the content of this adhesion improver is less than 1%, the adhesion to the steel plate cannot be sufficiently ensured, so foreign matter defects may occur. On the other hand, when the content of this adhesion improver exceeds 20%, the amount remaining after forming the coating film is too much, so corrosion resistance, etc., may not be ensured.

[0060] In the present invention, the type of the adhesion improver is not particularly limited, but preferably it may be one or more selected from vinyl methoxysilane, vinyltrimethoxysilane (VTMS), vinyltriethoxysilane, vinyltriethoxysilane, 3 - aminopropyltriethoxysilane, 3 - glycidoxypropyltrimethoxysilane, 3 - methylglycidoxypropyltrimethoxysilane, γ - glycidoxypropyltriethoxysilane, γ - glycidoxytrimethyldimethoxysilane, N - (3 - (trimethoxysilyl)propyl)ethylenediamine (AEAPTMS), 2 - (3,4 - epoxycyclohexyl)ethyltrimethoxysilane, 2 - (3,4 - epoxycyclohexyl)ethyltriethoxysilane, 3 - (2,3 - epoxypropoxy)propyltrimethoxysilane, 3 - (2,3 - epoxypropoxy)propyltriethoxysilane, 3 - (2,3 - epoxypropoxy)propylmethyldiethoxysilane, 3 - (2,3 - epoxypropoxy)propylmethyldimethoxysilane, 3 - aminopropyltriethoxysilane, 3 - aminopropyltrimethoxysilane, 3 - aminopropylmethyldiethoxysilane, N - (2 - aminoethyl - 3 - aminopropyl)methyldimethoxysilane, N - (2 - aminoethyl - 3 - aminopropyl)trimethoxysilane, diethylenetriaminepropyltrimethoxysilane, 3 - ureidopropyltrimethoxysilane, N - phenylaminopropyltrimethoxysilane, (3 - glycidoxypropyl)trimethoxysilane (GPTMS), methyltrimethoxysilane (MTMS), and mixtures thereof.

[0061] 1 - 20% of the corrosion resistance improver

[0062] The corrosion inhibitor in the solution composition of the present invention fills the possible gaps between the trivalent chromium compound, the adhesion improver, etc., and forms a passivation film, thereby playing a role in suppressing the generation of corrosion.

[0063] When the content of such a corrosion inhibitor is less than 1%, the passivation film cannot be sufficiently formed, so it is difficult to ensure corrosion resistance. On the other hand, when the content of such a corrosion inhibitor exceeds 20%, the solution stability may decrease due to excessive solids.

[0064] In the present invention, the type of the corrosion inhibitor is not particularly limited, but preferably it may be one or more selected from vanadyl acetylacetonate, ammonium metavanadate, potassium metavanadate, sodium metavanadate, vanadium trioxide, vanadium acetoacetate, ammonium metavanadate, silicon oxide, and their mixtures.

[0065] 0.1 - 5.0% pitting improver,

[0066] The pitting improver in the solution composition of the present invention, together with the corrosion inhibitor, prevents the local penetration of corrosion factors, thereby playing a role in minimizing pitting occurring in a punctiform form.

[0067] In the solution composition of the present invention, when the content of the pitting improver is less than 0.1%, the local penetration of corrosion factors cannot be blocked, so there is a problem of pitting occurring. On the other hand, when the content of the pitting improver exceeds 5.0%, the pH of the solution rises excessively, so the solution stability may decrease.

[0068] In the present invention, the type of the pitting improver is not particularly limited, but preferably it may be one or more selected from ethylenediamine, hexamethylenediamine, trimethylamine, methylamine, diphenylamine, ethyleneamine, aniline, toluidine, piperidine, aziridine, pyridine, alanine, propylamine, diisopropylamine, monoisopropylamine, dibutylamine, dipropylamine, and their mixtures.

[0069] 1 - 10% long - term corrosion resistance improver,

[0070] The long - term corrosion resistance improver in the solution composition of the present invention improves the corrosion resistance by combining with the corrosion products of the zinc alloy coating during the corrosion process after coating, activating the formation of so - called simonkolleite, thereby playing a role in improving the long - term corrosion resistance of zinc alloy (as an example, ternary molten zinc alloy) plated steel sheets.

[0071] When the content of the long - term corrosion resistance improver is less than 1%, the long - term corrosion resistance may not be improved due to insufficient contribution to the formation of the simonkolleite. On the other hand, when the content of the long - term corrosion resistance improver exceeds 10%, foreign matter defects may occur due to excessive chromium components.

[0072] In the present invention, the type of the long-term corrosion inhibitor is not particularly limited, but preferably it can be one or more selected from anhydrous chromium chloride, chromium chloride pentahydrate, chromium chloride hexahydrate, chromium chloride nonahydrate, and mixtures thereof.

[0073] 0.1 - 3.0% lubricant

[0074] The lubricant in the solution composition of the present invention improves the slipperiness of the steel plate surface to improve workability and plays a role in suppressing the occurrence of foreign object defects.

[0075] When the content of the lubricant is less than 0.1%, the slipperiness of the steel plate surface is insufficient, and foreign object defects may occur. On the other hand, when the content of the lubricant exceeds 3.0%, due to the excessive content of the lubricant, the solution stability may decrease.

[0076] In the present invention, the type of the lubricant is not particularly limited, but preferably it can be one or more selected from polytetrafluoroethylene (PTFE), polyethylene (PE), carnauba wax, and mixtures thereof.

[0077] 1 - 20% cosolvent

[0078] The cosolvent in the solution composition of the present invention regulates the evaporation rate of the solvent during the drying process of the coating operation, thereby playing a role in suppressing defects on the surface of the dried film.

[0079] When the content of such a cosolvent is less than 1%, the effect of regulating the evaporation rate during the drying process is insufficient. In terms of the evaporation rate of the main solvent, the main solvent boils rapidly at the boiling point, and surface defects called "popping" occur, so there are problems such as a decrease in corrosion resistance. On the other hand, when the content of such a cosolvent exceeds 20%, due to sharp changes in the viscosity and density of the solution, the solution stability may decrease.

[0080] In the present invention, the type of the cosolvent is not particularly limited, but preferably it can be one or more selected from ethanol, isopropanol, methanol, tallow alcohol, 2-butoxyethanol, diethylene glycol monobutyl ether, and mixtures thereof.

[0081] Solvent

[0082] The solution composition of the present invention may contain a solvent as the balance component. In the present invention, water (distilled water, deionized water) can be used as the solvent.

[0083] Next, a surface-treated steel plate that is surface-treated with the above solution composition to include a specified coating according to another aspect of the present invention will be specifically described.

[0084] In the present invention, the composition can be used for surface treatment of plated steel sheets. For example, it can be used for surface treatment of zinc-plated steel sheets, and preferably for surface treatment of Zn-Mg-Al ternary alloy plated steel sheets.

[0085] That is, the surface-treated plated steel sheet of the present invention can include: a steel sheet; a plating layer formed on at least one surface of the steel sheet; and a surface treatment coating formed on the plating layer. Among them, the steel sheet is the base steel sheet for obtaining the plated steel sheet. In particular, as long as it is a steel sheet that can obtain a ternary (Zn-Mg-Al system) hot-dip galvanized steel sheet.

[0086] As an example, by weight%, the composition of the Zn-Mg-Al plating layer can include: magnesium (Mg): 4.0 - 7.0%, aluminum (Al): 11.0 - 19.5%, and the balance of Zn and other inevitable impurities.

[0087] Magnesium (Mg) in the plating layer is an element that plays a role in improving the corrosion resistance of the plated steel sheet. In order to ensure the excellent corrosion resistance desired by the present invention, the content of magnesium is preferably 4.0% or more. However, when the content of Mg is too high, scum may be generated in the plating bath, and too many high-hardness intermetallic compounds are formed in the plating layer, so that the bendability of the steel sheet may deteriorate. Therefore, the upper limit of the content of magnesium can be limited to 7.0%.

[0088] In addition, when the added content of Mg is 4.0% or more, there is a risk of scum generation due to the oxidation of Mg in the plating bath. Therefore, considering this point, the content of aluminum (Al) is preferably 11.0% or more. However, when the content of Al is too high, the melting point of the plating bath becomes high, and the operating temperature becomes too high, which may cause problems caused by high-temperature operations, such as erosion of the plating bath structure and deformation of the steel sheet. Therefore, the content of Al is preferably limited to 19.5% or less.

[0089] The balance of the composition other than Mg and Al is zinc (Zn), and inevitable impurities may be inadvertently mixed in during the process of manufacturing a plated steel sheet with a Zn-Mg-Al plating layer. At this time, it should be noted that those skilled in the art can easily understand the meaning of inevitable impurities.

[0090] The structure of the above Zn-Mg-Al plating layer preferably satisfies the following [Relationship 1].

[0091] [Relationship 1]

[0092] 0.26 ≤ I(110) / I(103) ≤ 0.65

[0093] (In Equation 1, I(110) represents the X-ray diffraction integrated intensity of the (110) plane crystal of the MgZn2 phase, and I(103) represents the X-ray diffraction integrated intensity of the (103) plane crystal of the MgZn2 phase.)

[0094] By controlling the MgZn2 phase of the Zn-Mg-Al based coating with the [Equation 1], the bendability, whiteness, etc. of the coated steel sheet can be ensured.

[0095] When the value defined by the [Equation 1] is less than 0.26, the proportion of the (103) plane crystal of the MgZn2 phase relative to the (110) plane crystal of the MgZn2 phase is too high, so the bendability or whiteness may be insufficient. On the other hand, when the value defined by the [Equation 1] exceeds 0.65, the proportion of the (110) plane crystal of the MgZn2 phase relative to the (103) plane crystal of the MgZn2 phase is too high, and the increase in diffuse reflection cannot be induced, so the problem of insufficient whiteness may occur.

[0096] At this time, the value of the integrated intensity of I(110) can have a range of 120 to 200, and the value of the integrated intensity of I(103) can be in the range of 240 to 300. As described above, it is preferable to satisfy the value of the [Equation 1] within each range.

[0097] The upper part of the above Zn-Mg-Al based coating may include a coating layer, which is formed by coating the composition of the present invention in a solution state. At this time, the coating layer preferably has a thickness of 0.1 - 2.0 μm.

[0098] When the thickness of the coating layer is less than 0.1 μm, the surface treatment solution composition is thinly coated on the peak portions of the roughness existing on the surface of the coated steel sheet, so there is a problem of reduced corrosion resistance. On the other hand, when the thickness of the coating layer exceeds 2.0 μm, due to the formation of a thick film layer (coating layer), the workability deteriorates and the solution treatment cost increases, which is not economical.

[0099] Among them, the thickness refers to the thickness after drying.

[0100] In addition, in the present invention, a method for manufacturing a surface-treated steel sheet using the composition is described.

[0101] More specifically, the method may include the following steps: providing a coated steel sheet with a coating layer formed on at least one side; performing a coating treatment on the coating layer with the above solution composition; and drying the steel sheet subjected to the coating treatment.

[0102] When the composition of the present invention is coated on the steel plate in a solution state, commonly used coating methods can be applied, so there are no particular limitations.

[0103] For example, one of the methods such as bar coating, roll coating, spray coating, dipping, jet extrusion, and dip extrusion can be selected for the coating process.

[0104] The process of drying the steel plate coated with the composition is preferably carried out in a temperature range of 40 - 280 °C based on the final reached temperature (PMT) of the material (steel plate).

[0105] When the temperature of the drying process is lower than 40 °C based on the final reached temperature of the material, the formation of a strong film structure is insufficient, so the corrosion resistance and blackening resistance may deteriorate. On the other hand, when the temperature of the drying process exceeds 280 °C, the hardness of the film increases excessively, resulting in poor corrosion resistance of the processed part, and the surface quality may deteriorate due to overheating, such as yellowing phenomenon, etc.

[0106] The steel plate after the drying process can have a coating with a thickness of 0.1 - 2.0 μm after drying.

[0107] In the present invention, the equipment for the drying process is not particularly limited, but equipment such as an induction oven or a hot air drying furnace can be used, and the conditions of these equipment can be based on conventional conditions. Detailed Description of the Invention

[0108] (Examples)

[0109] Hereinafter, the present invention will be described in more detail through examples. However, the description of these examples is only for illustrating the implementation of the present invention, and the present invention is not limited by these examples. This is because the scope of the rights of the present invention is determined by the content recorded in the claims and the content reasonably deduced therefrom.

[0110] First, in order to measure the physical properties of the solution composition for surface treatment, a solution composition was prepared using the following substances. Phosphoric acid as an acidity regulator was added to distilled water, and chromium nitrate as a trivalent chromium compound and chromium chloride nonahydrate as a long-term corrosion resistance improver were added at about 40 °C, and then stirred for about 30 minutes. In the same manner, GPTMS as an adhesion improver was added, and silicon oxide as a corrosion resistance improver, ethylenediamine as a pitting corrosion improver, ethanol as a co-solvent, and polyethylene (PE) as a lubricant were added every 30 minutes while stirring.

[0111] At this time, the content of each component (weight%, the rest is solvent) is shown in Tables 1 and 2 below.

[0112] [Table 1]

[0113]

[0114] [Table 2]

[0115]

[0116] Using the solution composition for surface treatment manufactured as described above, a ternary hot-dip galvanized alloy steel sheet test piece containing Mg: 4.0 - 7.0 wt%, Al: 11.0 - 19.5 wt%, and the balance Zn and other inevitable impurities is cut into 7 cm × 15 cm (transverse × longitudinal) and degreased, and then bar-coated so that the film adhesion amount based on Cr is about 35 mg / m 2 (at a level of about 0.4 μm in thickness), thereby producing a test piece. At this time, drying is carried out at 50 °C.

[0117] In order to measure the physical properties of the solution composition prepared as described above and the coated steel sheet test piece surface-treated with the solution composition, the solution stability, flat plate corrosion resistance, corrosion resistance of the processed part, pipe-making oil erosion resistance, alkali resistance, pitting corrosion resistance, blackening resistance, foreign object defects, and long-term corrosion resistance are measured according to the following methods and criteria.

[0118] Solution stability

[0119] The initial viscosity (Vi) of the coating composition prepared by the above method is measured immediately after preparation, and after being stored in an oven at 50 °C for 120 hours and then cooled to 25 °C again, the final viscosity (Vl) at 25 °C is measured, and then substituted into the following mathematical formula 1, and its structure is evaluated according to the following evaluation criteria.

[0120] [Mathematical formula 1]

[0121] △V = (Vl - Vi) / Vi × 100 (%)

[0122] <Evaluation criteria for solution stability>

[0123] ○: △V is less than 20 (%), or no gelation phenomenon is observed during visual observation

[0124] ×: △V is 20 (%) or more, or a gelation phenomenon is observed during visual observation

[0125] Flat plate corrosion resistance

[0126] According to the method specified in ASTM B117, the white rust formation rate of the steel plate over time is measured after treating each steel plate (test piece) with the solution composition.

[0127] <Evaluation criteria for flat plate corrosion resistance>

[0128] ○: The time for white rust to form is more than 144 hours

[0129] △: The time for white rust to form is more than 96 hours and less than 144 hours

[0130] ×: The time for white rust to form is less than 96 hours

[0131] Corrosion resistance of processed parts

[0132] The steel plate (test piece) surface-treated as described above was pushed to a height of 6 mm using an Erichsen tester, and the degree of white rust generation was measured after 24 hours.

[0133] <Evaluation Criteria for Corrosion Resistance of Processed Parts>

[0134] ○: No white rust occurs, or even if white rust occurs, it is very fine

[0135] △: White rust has formed inside the circle and has partially flowed out but has not flowed to the outside

[0136] ×: White rust occurs and flows outside the circle

[0137] Pipe making oil corrosiveness

[0138] The steel plate (test piece) treated as above was immersed in pipe oil at room temperature for 24 hours, and then the color difference before and after immersion was measured. At this time, the pipe oil was Korea Panyu BW WELL MP-411 diluted with water to 10% and used.

[0139] <Evaluation Criteria for Corrosiveness of Pipe Making Oil>

[0140] ○: ΔE≤2

[0141] △: 2<ΔE≤3

[0142] ×: 3<ΔE

[0143] Alkali resistance

[0144] The steel plate (test piece) treated as above was immersed in a degreasing solution at 60°C for 2 minutes, then washed with water and blown with air, and the color difference before and after was measured. At this time, the alkaline degreasing solution used was Finecleaner L 4460 A: 20g / 2.4L + L 4460 B: 12g / 2.4L (pH=12) from Parker Seiki.

[0145] <Evaluation Criteria for Alkali Resistance>

[0146] ○: ΔE≤2

[0147] △: 2 < ΔE ≤ 4

[0148] ×: 4 < ΔE

[0149] Pitting corrosion resistance

[0150] Using a sprayer, make the surface of the surface-treated steel sheet (test piece) as described above dew, then wrap two pieces of the spray-treated steel sheets facing each other and place them in a thermo-hygrostat. Take 6 hours at high temperature and high humidity (42 °C, 95%) and 6 hours at low temperature and low humidity (15 °C, 60%) as one cycle, and conduct a total of 8 cycles, then measure the number of pitting defects on the surface. At this time, set the scanning area of the steel sheet to 150 × 50 mm 2 , magnify it 100 times, and only count the number of corrosive pitting defects with an area of 29500 μm 2 or more.

[0151] <Evaluation criteria for pitting corrosion resistance>

[0152] ○: Number of pits ≤ 20

[0153] △: 20 < Number of pits ≤ 40

[0154] ×: 40 < Number of pits

[0155] Blackening resistance

[0156] To evaluate the blackening resistance of the steel sheet, measure the color difference of the steel sheet treated with the trivalent chromium surface treatment composition, then place it in a thermo-hygrostat and keep it at a temperature of 50 °C and a relative humidity of 95% for 120 hours, then take out the steel sheet and measure the color difference.

[0157] <Evaluation criteria for blackening resistance>

[0158] ○: ΔE ≤ 3

[0159] △: 3 < ΔE ≤ 5

[0160] ×: 5 < ΔE

[0161] Foreign matter defects

[0162] To evaluate the foreign matter defects of the steel sheet treated with the surface treatment composition, cover a probe with a surface area of about 4 cm 2 with white gauze, then place a weight of 10 kg on the probe, reciprocally rub it 100 times, and then measure the whiteness (ΔL = L 之前(before) -L 之后(after) ) value of the gauze before and after friction. At this time, to simulate high humidity conditions, put the steel sheet, the probe, etc. into a humidity chamber, use a humidifier, etc. to maintain a humidity of more than 95% and conduct friction evaluation.

[0163] <Evaluation Criteria for Foreign Object Defects>

[0164] ○: ΔL ≤ 2.5

[0165] △: 2.5 < ΔL ≤ 5

[0166] ×: 5 < ΔL

[0167] Long - term Corrosion Resistance

[0168] In order to evaluate the long - term corrosion resistance, the steel plate treated with the said surface treatment composition is subjected to a cyclic corrosion test according to [ISO14993] in the manner of [Salt spray 2 hours (hr) (5% NaCl, 35°C) → Drying 4 hours (25% RH, 60°C) → Humid 2 hours (95% RH, 50°C)], and the red rust occurrence time is measured. At this time, based on the cross - section, the plating adhesion amount of the plated steel plate is 150 g / m 2 .

[0169] <Evaluation Criteria for Long - term Corrosion Resistance>

[0170] ○: 200 days ≤ Red rust occurrence period

[0171] △: 150 days < Red rust occurrence period ≤ 200 days

[0172] ×: Red rust occurrence period < 150 days

[0173] The measurement results of the said physical properties are shown in Tables 3 and 4 below.

[0174] [Table 3]

[0175]

[0176] [Table 4]

[0177]

[0178] In the case of Invention Examples 1 to 16 according to the present invention, it can be seen that the solution stability, flat corrosion resistance, processing part corrosion resistance, pipe - making oil erosion resistance, alkali resistance, pitting corrosion resistance, blackening resistance, long - term corrosion resistance and foreign object defects are very excellent.

[0179] In the case of Comparative Example 1, the content of the trivalent chromium compound is insufficient, and the corrosion resistance brought by the barrier effect becomes poor. Therefore, it can be seen that the flat corrosion resistance, processing part corrosion resistance, pitting corrosion resistance and long - term corrosion resistance are insufficient.

[0180] In the case of Comparative Example 2, the content of the trivalent chromium compound is too high. Therefore, it can be seen that foreign object defects occur.

[0181] In the case of Comparative Example 3, the content of the acidity regulator is insufficient and the solution stability is insufficient. Therefore, it can be seen that the flat plate corrosion resistance, the processing part corrosion resistance, the pitting corrosion resistance, the blackening resistance and the long-term corrosion resistance are poor.

[0182] In the case of Comparative Example 4, the content of the acidity regulator is too high. Due to the residual acid, it can be seen that the flat plate corrosion resistance, the processing part corrosion resistance, the pitting corrosion resistance and the long-term corrosion resistance are insufficient.

[0183] In the case of Comparative Example 5, the content of the adhesion improver is insufficient. Therefore, it can be seen that foreign matter defects occur.

[0184] In the case of Comparative Example 6, the content of the adhesion improver is too high. Due to the residual unreacted silane, it can be seen that the flat plate corrosion resistance, the processing part corrosion resistance, the pitting corrosion resistance and the long-term corrosion resistance are insufficient.

[0185] In the case of Comparative Example 7, the content of the corrosion resistance improver is insufficient. It can be seen that the flat plate corrosion resistance, the processing part corrosion resistance, the pitting corrosion resistance and the long-term corrosion resistance are insufficient.

[0186] In the case of Comparative Example 8, the content of the corrosion resistance improver is too high. Due to the high solid content, the solution stability is insufficient. Therefore, it can be seen that the flat plate corrosion resistance, the processing part corrosion resistance, the pitting corrosion resistance, the blackening resistance and the long-term corrosion resistance are poor.

[0187] In the case of Comparative Example 9, the content of the pitting corrosion improver is insufficient. Therefore, it can be seen that the pitting corrosion resistance is poor.

[0188] In the case of Comparative Example 10, the content of the pitting corrosion improver is too high and the solution stability is insufficient. Therefore, it can be seen that the processing part corrosion resistance, the pipe making oil erosion resistance, the blackening resistance and the long-term corrosion resistance are poor.

[0189] In the case of Comparative Example 11, the content of the long-term corrosion resistance improver is insufficient. Therefore, it can be seen that the long-term corrosion resistance is poor.

[0190] In the case of Comparative Example 12, the content of the long-term corrosion resistance improver is too high. Therefore, it can be seen that foreign matter defects occur.

[0191] In the case of Comparative Example 13, the content of the lubricant is insufficient. Therefore, it can be seen that foreign matter defects occur.

[0192] In the case of Comparative Example 14, the content of the lubricant is too high and the solution stability is insufficient. Therefore, it can be seen that the processing part corrosion resistance and the long-term corrosion resistance are poor.

[0193] In the case of Comparative Example 15, the content of the cosolvent is insufficient and surface defects occur. Therefore, it can be seen that the flat plate corrosion resistance, the processing part corrosion resistance and the long-term corrosion resistance are poor.

[0194] In the case of Comparative Example 16, the content of the co-solvent was too high and the solution stability was insufficient. Therefore, it was found that the corrosion resistance, blackening resistance, and long-term corrosion resistance of the processed part were poor.

Claims

1. A solution composition for surface treatment, comprising: 1 - 10% by weight of a trivalent chromium compound, 0.1 - 5% by weight of an acidity regulator, 1 - 20% by weight of an adhesion improver, 1 - 20% by weight of a corrosion resistance improver, 0.1 - 5.0% by weight of a pitting corrosion improver, 1 - 10% by weight of a long - term corrosion resistance improver, 0.1 - 3.0% by weight of a lubricant, 1 - 20% by weight of a co - solvent, and the balance of a solvent.

2. The solution composition for surface treatment according to claim 1, wherein The trivalent chromium compound is one or more selected from chromium sulfate, chromium nitrate, chromium phosphate, chromium fluoride, and mixtures thereof.

3. The solution composition for surface treatment according to claim 1, wherein, The acidity regulator is one or more selected from phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, (NH4)H2PO4, (NH4)2HPO4, NaH2PO4, Na2HPO4, phytic acid, glycolic acid, lactic acid, acetic acid, oxalic acid, and mixtures thereof.

4. The solution composition for surface treatment according to claim 1, wherein, The adhesion improver is one or more selected from vinyl methoxysilane, vinyltrimethoxysilane (VTMS), vinyl ethoxysilane, vinyltriethoxysilane, 3 - aminopropyltriethoxysilane, 3 - glycidoxypropyltrimethoxysilane, 3 - methylglycidoxypropyltrimethoxysilane, γ - glycidoxypropyltriethoxysilane, γ - glycidoxytrimethyldimethoxysilane, N-(3-(trimethoxysilyl)propyl)ethylenediamine (AEAPTMS), 2-(3,4 - epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4 - epoxycyclohexyl)ethyltriethoxysilane, 3-(2,3 - epoxypropoxy)propyltrimethoxysilane, 3-(2,3 - epoxypropoxy)propyltriethoxysilane, 3-(2,3 - epoxypropoxy)propylmethyldiethoxysilane, 3-(2,3 - epoxypropoxy)propylmethyldimethoxysilane, 3 - aminopropyltriethoxysilane, 3 - aminopropyltrimethoxysilane, 3 - aminopropylmethyldiethoxysilane, N-(2 - aminoethyl - 3 - aminopropyl)methyldimethoxysilane, N-(2 - aminoethyl - 3 - aminopropyl)trimethoxysilane, diethylenetriaminepropyltrimethoxysilane, 3 - ureidopropyltrimethoxysilane, N - phenylaminopropyltrimethoxysilane, (3 - glycidoxypropyl)trimethoxysilane (GPTMS), methyltrimethoxysilane (MTMS), and mixtures thereof.

5. The solution composition for surface treatment according to claim 1, wherein, The corrosion resistance improver is one or more selected from vanadyl acetylacetonate, ammonium metavanadate, potassium metavanadate, sodium metavanadate, vanadium trioxide, vanadium acetylacetate, ammonium metavanadate, silicon oxide, and mixtures thereof.

6. The solution composition for surface treatment according to claim 1, wherein, The pitting corrosion improver is one or more selected from ethylenediamine, hexamethylenediamine, trimethylamine, methylamine, diphenylamine, ethyleneamine, aniline, toluidine, piperidine, aziridine, pyridine, alanine, propylamine, diisopropylamine, monoisopropylamine, dibutylamine, dipropylamine, and mixtures thereof.

7. The solution composition for surface treatment according to claim 1, wherein, The long - term corrosion resistance improver is one or more selected from anhydrous chromium chloride, chromium chloride pentahydrate, chromium chloride hexahydrate, chromium chloride nonahydrate, and mixtures thereof.

8. The solution composition for surface treatment according to claim 1, wherein, The lubricant is one or more selected from polytetrafluoroethylene (PTFE), polyethylene (PE), carnauba wax, and mixtures thereof.

9. The solution composition for surface treatment according to claim 1, wherein, The cosolvent is one or more selected from ethanol, isopropanol, methanol, tallow alcohol, 2-butoxyethanol, diethylene glycol monobutyl ether, and mixtures thereof.

10. A surface-treated coated steel sheet, comprising: a steel sheet; a coating layer formed on at least one surface of the steel sheet; and a surface treatment coating layer formed on the coating layer, wherein the surface treatment coating layer is formed from the solution composition according to any one of claims 1 to 9.

11. The surface-treated plated steel sheet according to claim 10, wherein, By weight %, the coating layer contains: magnesium (Mg): 4.0 - 7.0%, aluminum (Al): 11.0 - 19.5%, and the balance of Zn and other inevitable impurities.

12. The surface-treated plated steel sheet according to claim 11, wherein, The coating layer satisfies the following relationship 1, [Relationship 1] 0.26 ≤ I(110) / I(103) ≤ 0.65 In relationship 1, I(110) represents the X-ray diffraction integrated intensity of the (110) plane crystal peak of the MgZn2 phase, and the I(103) represents the X-ray diffraction integrated intensity of the (103) plane crystal of the MgZn2 phase.

13. The surface-treated plated steel sheet according to claim 10, wherein, The surface treatment coating layer has a thickness of 0.1 - 2.0 μm.

14. A method for manufacturing a surface-treated coated steel sheet, comprising the following steps: providing a galvanized alloy steel sheet having a coating layer formed on at least one surface; performing a coating treatment on the coating layer with the solution composition according to any one of claims 1 to 9; and drying the steel sheet subjected to the coating treatment.

15. The manufacturing method of the surface-treated plated steel sheet according to claim 14, wherein, The coating treatment is performed by any one method selected from bar coating, roll coating, spraying, dipping, jet extrusion, and dip extrusion.

16. The method for manufacturing a surface-treated plated steel sheet according to claim 14, wherein, The drying is performed within a temperature range of 40 - 280 °C based on the final reached temperature (PMT) of the steel sheet.

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