Composition for surface treatment of steel sheet

Abstract

To provide a composition for surface treatment capable of imparting flat sheet corrosion resistance, worked part corrosion resistance, pitting corrosion resistance, blackening resistance, pipe making oil infiltration resistance and alkali resistance to a steel sheet and improving foreign matter defects, and to provide a steel sheet using the same.SOLUTION: The surface treatment composition includes a trivalent chromium compound; an adhesion improving agent including a silane compound; an acidity controller including an acid; a cross-linking agent including a silicate compound; a vanadium-based pitting corrosion improving agent; a polymer resin; and a solvent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a surface treatment composition for steel sheets containing a trivalent chromium compound, and to a steel sheet using the same. Regarding. [Background technology]

[0002] High corrosion resistance hot-dip plating materials are zinc (Zn), magnesium (Mg) and aluminum (Al ) and is known to have excellent red rust corrosion resistance.

[0003] However, the exposed surface of the highly corrosion-resistant hot-dip plated material is mostly made of Zn or Zn alloy. Therefore, when exposed to a humid atmosphere, pitting corrosion defects are likely to occur on the surface, resulting in poor appearance. There are some disadvantages.

[0004] In recent years, in the phosphorus processing process, the highly corrosion-resistant hot-dip plated material passes through rolls. However, defects due to plating material components adhering to the roll also occur.

[0005] To solve this problem, conventionally, plated steel sheets were treated with a method that uses hexavalent chromium as the main component. By immersing the material in a solution containing chromate to form a coating, corrosion resistance and blackening resistance are achieved. We have secured this.

[0006] However, hexavalent chromium is now designated as a harmful environmental substance and a carcinogen. Restrictions on the use of valent chromium are being tightened.

[0007] On the other hand, divalent chromium, tetravalent chromium, and pentavalent chromium are relatively unstable, so It is not widely used in surface treatment solution compositions.

[0008] Recently, surface treatment solution compositions containing low toxicity and stable trivalent chromium have been used for steel sheets. The method of coating on the plated steel sheet to ensure corrosion resistance and blackening resistance is applied. do.

[0009] For example, Korean Patent Publication No. 10-2006-0123628 and Korean Patent Publication No. 10 -2005-0052215 and Korean Patent Publication No. 10-2009-0024450, This method involves immersing the steel sheet in a composition containing trivalent chromium to perform chemical conversion treatment, ensuring corrosion resistance and blackening. It is maintained.

[0010] However, the chemical conversion treatment method requires a long immersion time to be applied to the continuous process of steel mills. This causes problems such as a decrease in fingerprint resistance.

[0011] Also, Korean Patent Publication No. 10-2004-0046347 and Japanese Patent Publication No. 2002-06966 In Publication No. 0, a composition containing trivalent chromium is sprayed or roll coated onto a painted steel sheet. By coating with this method, it can be applied to the continuous production line of steel companies and has fingerprint resistance. It has been secured.

[0012] However, since the composition contains porous silica components that have a strong moisture absorbing property, M There is a problem with g, Al, and Zn alloy steel sheets that causes rapid discoloration. Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to improve the flat corrosion resistance, processed part corrosion resistance, pitting corrosion resistance, and foreign matter defect resistance of steel plates. The present invention aims to provide a composition for surface treatment of steel sheets that can improve the surface toughness.

[0014] Another object of the present invention is to improve the blackening resistance, pipe-making oil corrosion resistance, and alkali resistance of steel sheets. The present invention provides a composition for surface treatment of hardened steel sheets.

[0015] Another object of the present invention is to provide a pipe having excellent corrosion resistance, blackening resistance, pipe-making oil corrosion resistance, and alkali resistance, The object of the present invention is to provide a steel sheet with improved foreign matter defects.

[0016] The object of the present invention is not limited to the above-mentioned object, and other object of the present invention not mentioned above. The advantages and merits of the present invention can be understood from the following description and become more apparent from the following examples. The objects and advantages of the present invention can be easily understood by the following claims. It is easy to see what can be achieved by stages and their combinations. [Means for solving the problem]

[0017] The surface treatment composition for steel sheets according to the present invention is an adhesive composition containing a trivalent chromium compound; a silane compound; Properties improver; Acidity regulator containing acid; Crosslinker containing silicate compound; Vanadium-based pitting corrosion improver Polymer resin; and solvent.

[0018] The steel sheet according to the present invention comprises a steel sheet base material; a zinc-plated layer disposed on the steel sheet base material; and a surface treatment layer disposed on the zinc plating layer, the surface treatment layer comprising a trivalent chromium compound, an adhesion improver containing a silane compound, an acidity regulator containing an acid, and a crosslinking agent containing a silicate compound; Contains a vanadium-based pitting corrosion improver and a polymeric resin. [Effects of the Invention]

[0019] The steel plate according to the present invention has improved flat plate corrosion resistance, processed part corrosion resistance, pitting corrosion resistance, and foreign matter defect resistance. It has an improving effect.

[0020] Furthermore, the steel sheet according to the present invention has excellent effects of blackening resistance, corrosion resistance to pipe-making oil, and alkali resistance. do.

[0021] Furthermore, the steel sheet according to the present invention has an improved product life and is therefore suitable for the distribution process, such as phosphorus processing of the steel sheet. This has the effect of improving the problems in the

[0022] The above-mentioned effects and specific effects of the present invention will be apparent from the following detailed description of the preferred embodiments of the present invention. Also describe. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a photograph of a highly corrosion-resistant plated steel sheet (left) on which pitting corrosion has occurred, and a highly corrosion-resistant plated steel sheet (right) coated with the surface treatment composition of the present invention. [Figure 2] 1 is a photograph showing a microstructure of a surface treatment layer (coating layer) of the present invention. [Figure 3] 1 shows the results of EDS component analysis of the surface treatment layer (coating layer) of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The above objects, features and advantages will be described in detail below with reference to the accompanying drawings, whereby A person having ordinary skill in the art to which the present invention pertains can easily understand the technical concept of the present invention. In explaining the present invention, the following will be described in detail with reference to the known art. If it is determined that a specific description would obscure the gist of the present invention, the detailed description may be omitted. Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The same reference numbers in the drawings are used to denote the same or similar components.

[0025] "Top (or bottom)" of the component or "Top (or bottom)" of the component in the following The fact that the above-mentioned configuration is arranged means that any configuration is in contact with the upper surface (or lower surface) of the above-mentioned component. In addition to being arranged on the component, the component and any structure arranged on (or under) the component may be This means that other components may be present between the two components.

[0026] The following describes the surface treatment compositions for steel sheets according to some embodiments of the present invention, and the methods for treating steel sheets using the same. This section explains the steel plate.

[0027] In the present invention, the components of the surface treatment composition to be coated on the surface of the highly corrosion-resistant plated steel sheet are By adjusting the composition ratio, the appearance corrosion resistance of the steel sheet is improved, and the defects of foreign matter are improved, resulting in a high quality product. It not only improves the lifespan of steel plates, but also solves problems in the distribution process, such as phosphorus processing of steel plates. Ta.

[0028] Furthermore, the surface treatment composition of the present invention does not contain hexavalent chromium, which is a harmful environmental substance and a carcinogen. Instead of compounds, it contains a less toxic trivalent chromium compound, which reduces harm to the human body and the environment. This is effective in preventing contamination problems.

[0029] Furthermore, the surface treatment composition for steel sheets of the present invention does not contain a porous silica component, so it is not easily broken down. It is effective in preventing the phenomenon that causes drastic discoloration.

[0030] The surface treatment composition for steel sheets of the present invention contains a trivalent chromium compound and a silane compound, and has adhesion promoting properties. Superplasticizer, acidity regulator containing acid, crosslinking agent containing silicate compound, vanadium-based pitting corrosion improver , a polymer resin, and a solvent.

[0031] The trivalent chromium compound is stable and has low toxicity, and forms mainly an insoluble coating on the surface of the steel sheet. Forms a film and provides corrosion resistance through a barrier effect Take on a role.

[0032] The trivalent chromium compound may be contained in an amount of 0.5 to 17 parts by weight per 100 parts by weight of the solvent. Preferably, the trivalent chromium compound is contained in an amount of 0.8 to 17 parts by weight per 100 parts by weight of the solvent. It can be 1 to 16 parts by weight, 1.1 to 16.9 parts by weight, 1.2 to 16.7 parts by weight, 1. It may contain 2 to 16.5 parts by weight, or 1.3 to 16.1 parts by weight.

[0033] If the amount of the trivalent chromium compound is less than 0.5 parts by weight, it is difficult to form a strong insoluble film. As a result, the water that penetrates the surface of the steel sheet cannot be effectively blocked, resulting in poor corrosion resistance. It may not be possible to secure

[0034] On the other hand, if the amount of trivalent chromium compound exceeds 17 parts by weight, the excessive chromium content can cause foreign matter chipping. Defects may occur.

[0035] Trivalent chromium compounds include chromium sulfate, chromium nitrate, chromium phosphate, chromium fluoride, and salts. The compound may contain one or more chromium compounds.

[0036] The adhesion improver containing the silane compound bonds with the crosslinking agent and resin, and also bonds with the steel sheet. It plays a role in improving the adhesion and corrosion resistance of the surface treatment layer. promotes the drying of the surface treatment layer and provides high corrosion resistance.

[0037] The adhesion improver containing a silane compound is used in an amount of 0.1 to 40 parts by weight per 100 parts by weight of the solvent. Preferably, the adhesion improver is contained in an amount of 0.1 to 38 parts by weight per 100 parts by weight of the solvent. The amount of the hydroxybenzoate may be 0.5 to 37 parts by weight, 1 to 36 parts by weight, or 1.1 It may contain from 1.2 to 35.7 parts by weight, or from 1.2 to 35.9 parts by weight.

[0038] If the amount of the adhesion improver is less than 0.1 parts by weight, sufficient adhesion to the steel sheet cannot be ensured. Therefore, it may not be possible to ensure corrosion resistance, etc.

[0039] On the other hand, if the amount of adhesion improver exceeds 40 parts by weight, a large amount of unreacted silicon dioxide will remain after the coating film is formed. Depending on the run, it may not be possible to ensure corrosion resistance, etc.

[0040] Adhesion improvers containing silane compounds include vinyl methoxy silane and vinyl trimethoxy silane. Vinyl epoxy silane, vinyl triepoxy silane, 3-aminopropyl triepoxy Silane, 3-glycidoxypropyltrimethoxysilane, 3-metaglyoxypropyl Trimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxy Trimethyldimethoxysilane, N-(3-(trimethoxysilyl)propyl)ethylenedi Amine (AEAPTMS), 2-(3,4-epoxycyclohexyl)ethyltrimethoxy Silane, 2-(3,4-epoxycyclohexyl)ethyltriepoxysilane, 3-( 2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propyl Methyldiethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldimethoxy Silane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane Silane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl-3-amino N-(2-aminoethyl-3-aminopropyl)methyldimethoxysilane Trimethoxysilane, Diethylenetriaminopropyltrimethoxysilane, 3-Ureido Propyltrimethoxysilane and N-phenylaminopropyltrimethoxysilane It may contain one or more of these.

[0041] The acidity regulator containing the acid adjusts the pH of the composition, and the components in the surface treatment composition are It exists stably in solution and reacts appropriately under coating conditions to form a stable coating. Do so.

[0042] The acidity regulator containing an acid can be contained in an amount of 0.5 to 11 parts by weight per 100 parts by weight of the solvent. Preferably, the acidity regulator is contained in an amount of 0.8 to 10 parts by weight per 100 parts by weight of the solvent. and the amount of the compound is 1 to 9 parts by weight, 1.1 to 8.8 parts by weight, 1.2 to 8.4 parts by weight, or 1.2 to 8 It may contain 0.1 parts by weight.

[0043] If the amount of the acid-containing acidity regulator is less than 0.5 parts by weight, the pH becomes high and the stability of the solution decreases. Conversely, if the amount of the acidity regulator containing an acid exceeds 11 parts by weight, the corrosion resistance may be reduced due to an excessively low pH. It may not be possible to ensure the quality of the product.

[0044] Acidity regulators containing acids include phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, and ammonium phosphate (( NH4)2HPO4, (NH4)H2PO4), primary phosphate (NaH2PO4), secondary Phosphate (Na2HPO4), phytic acid, glycolic acid, It may contain one or more of lactic acid and acetic acid.

[0045] The crosslinking agent containing the silicate compound reacts with the adhesion promoter and the resin to form the composition. It increases the degree of cross-linking and improves the corrosion resistance of coated steel sheets.

[0046] The crosslinking agent containing a silicate compound is contained in an amount of 2 to 20 parts by weight per 100 parts by weight of the solvent. Preferably, the crosslinking agent can be contained in an amount of 2 to 19 parts by weight per 100 parts by weight of the solvent. 2 to 18 parts by weight, 2.2 to 17.8 parts by weight, 2.4 to 17.6 parts by weight, or 2.5 to It may contain 17.3 parts by weight.

[0047] If the amount of the crosslinking agent containing the silicate compound is less than 2 parts by weight, the degree of crosslinking of the surface treatment layer is sufficiently ensured. Therefore, it may not be possible to ensure corrosion resistance, etc.

[0048] On the other hand, if the amount of the crosslinking agent containing the silicate compound exceeds 20 parts by weight, the amount of the crosslinking agent remaining after the formation of the coating film will be A large amount of unbound silicate may make it impossible to ensure corrosion resistance.

[0049] The crosslinking agent containing a silicate compound is sodium silicate. te), calcium silicate, potassium silicate Potassium silicate, aluminum silicate um silicate), lithium polysilicate icate), tetramethyl orthosilicate silicate, and tetraethyl orthosilicate hosilicate).

[0050] The vanadium-based pitting corrosion improver is a material that exhibits a low temperature crosslinking reaction between the resin, the crosslinking agent, and the adhesion improver. As is done in the case of galvanic corrosion, this lowers the temperature and serves to suppress the formation of micro-pitting corrosion.

[0051] The vanadium-based pitting corrosion improver is used in an amount of 0.1 to 14.3 parts by weight per 100 parts by weight of the solvent. Preferably, the pitting corrosion improver is 2 to 14.0 parts by weight per 100 parts by weight of the solvent. parts by weight, such as 2.8 to 13.9 parts by weight, 2.6 to 13.9 parts by weight, 2.5 to It may contain 13.9 parts by weight.

[0052] If the amount of the vanadium-based pitting corrosion improver is less than 0.1 parts by weight, the degree of crosslinking of the surface treatment layer is insufficient. It may not be possible to ensure the required corrosion resistance.

[0053] Conversely, if the vanadium-based pitting corrosion improver exceeds 14.3 parts by weight, the solids content will be too high. This can reduce the solution stability.

[0054] Vanadium-based pitting corrosion improvers include vanadium pentoxide (V2O5), metavanadate ( HVO3), ammonium metavanadate, potassium metavanadate, metavanadium Sodium phosphate, vanadium oxytrichloride (VOCl3), vanadium trioxide (V2O3 ), vanadium dioxide (VO2), vanadium oxysulfate (VOSO4), oxyoxalate Vanadium oxyacetylacetonate [VO(COO)2], Vanadium oxyacetylacetonate [VO(O C(CH3)=CHCOCH3))2], vanadium acetylacetonate [V(OC( CH3)=CHCOCH3))3], vanadium trichloride (VCl3), vanadium sulfate ( VSO4·8H2O), vanadium dichloride (VCl2), and vanadium oxide (VO It may contain one or more of these.

[0055] The polymer resin acts on the surface of the steel sheet together with the trivalent chromium compound, adhesion promoter, and cross-linking agent to improve rigidity. It is added to form a hard coating layer.

[0056] It is difficult to form a strong coating layer with excellent corrosion resistance using only inorganic components. By adding an organic polymer resin that gives flexibility to the composition of the present invention, precise coating shape can be achieved. It can improve the forming action and improve alkali resistance and oil corrosion resistance of pipes.

[0057] The polymer resin may be contained in an amount of 0.5 to 25 parts by weight per 100 parts by weight of the solvent. For example, the polymer resin may be contained in an amount of 0.7 to 23 parts by weight per 100 parts by weight of the solvent, and 1 to 23 parts by weight of the polymer resin may be contained per 100 parts by weight of the solvent. 20 parts by weight, 1.8 to 18 parts by weight, 1.6 to 16 parts by weight, or 1.4 to 15.8 parts by weight It can include.

[0058] If the polymer resin is less than 0.5 parts by weight, the formation of the coating film is insufficient, and the oil penetration resistance and the resistance to pipe making are poor. On the other hand, if the polymer resin exceeds 25 parts by weight, the relative trivalent The content of chromium compounds is reduced, and corrosion resistance may not be ensured.

[0059] The polymer resin is an emulsion resin, and may be a cationic polyurethane resin, a non-ionic One of ionic polyurethane resin, cationic acrylic resin, and nonionic acrylic resin It may contain more than one species.

[0060] Emulsion resin refers to a mixture of distilled water and a substance that is not compatible with distilled water. It has excellent dispersibility and storage properties, and has the advantage that layer separation does not occur even when left for a long time.

[0061] The cationic polyurethane resin and the cationic acrylic resin are each composed of primary to tertiary amino groups. It may contain cationic functional groups containing one or more of the following groups: .

[0062] For example, the cationic functional group may be an amino group, a methylamino group, an ethylamino group, a dimethylamino group, or a methylamino group. One of the following groups: amino group, diethylamino group, trimethylamino group, and triethylamino group It can include the above.

[0063] Non-ionic polyurethane resins are resins emulsified with non-ionic emulsifiers or The polymerizable composition can be formed using a reactive polyol.

[0064] Nonionic acrylic resins are resins emulsified with nonionic emulsifiers or nonionic acrylic resins. Phenoxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate, Ethoxyethoxyethyl acrylate, phenoxypolyethylene glycol (meth)acrylate Acrylate, Nonylphenol Polyethylene Glycol (Meth)acrylate, Methoxypoly Polyethylene glycol (meth)acrylate, polyethylene glycol mono(meth)acrylate Acrylate, Polypropylene glycol mono(meth)acrylate, Polytetramethylene Lithium mono(meth)acrylate, polyethylene glycol, polytetramethylene glycol Mono(meth)acrylate, and polypropylene glycol polytetramethylene glycol It may contain one or more of the following chol mono(meth)acrylates:

[0065] The solvent contained in the composition for surface treatment of steel sheets of the present invention is used to dilute the components of the composition. The additive may contain one or more of ethanol, distilled water, and deionized water. can.

[0066] On the other hand, the solvent is present in an amount of 100% by weight based on the total weight of the surface treatment composition for steel sheets. It is contained as a part, and it is about 50 to 85% by weight with respect to 100% by weight of the total composition. A solvent may be included.

[0067] In the present invention, solvents, trivalent chromium compounds, adhesion improvers, acidity regulators, crosslinking agents, pitting corrosion inhibitors, The improver and polymer resin can be mixed and stirred to prepare a surface treatment composition for steel sheets. The mixing and stirring temperature may be 24 to 80°C, but is not limited thereto. There is no.

[0068] As described above, the surface treatment composition for steel sheets of the present invention contains a small amount of trivalent chromium compounds, and the surface treatment composition for steel sheets containing a small amount of trivalent chromium compounds and a small amount of trivalent chromium compounds and the surface treatment composition for steel sheets containing ... Contains a large amount of solvent and includes a superplasticizer, acidity regulator, crosslinking agent, pitting corrosion improver, and polymer resin. The composition of the present invention can provide the steel sheet with corrosion resistance and other properties by adjusting the components and composition ratio. By adding this, there is an effect of further improving the defect of foreign matter.

[0069] The steel sheet using the steel sheet surface treatment composition of the present invention is as follows.

[0070] The steel plate comprises a steel plate base material, a zinc-plated layer disposed on the steel plate base material, and a zinc-plated and a surface treatment layer disposed on the layer.

[0071] The steel base material is cold-rolled steel, aluminum-plated steel, aluminum alloy, phosphate-coated steel, Although a galvanized steel sheet or a hot-rolled steel sheet can be used, there is no particular restriction on this. This is not limited to:

[0072] The zinc plating layer can be formed by hot dip galvanizing or electrogalvanizing. .

[0073] Hot dip galvanizing is called hot deep galvanized GI, and is made by heating zinc at high temperatures to melt it. After that, the plated products are placed in the refrigerator and frozen.

[0074] Electrogalvanizing involves placing the plated product in a plating solution containing zinc and then electrolyzing it. This is a plating method.

[0075] The surface treatment layer is a coating formed from a surface treatment composition for steel sheets, and the composition contains The solvent is removed, leaving only the remaining components.

[0076] Specifically, the surface treatment layer is formed by mixing 0.5 to 17 parts by weight of a trivalent chromium compound with 100 parts by weight of a solvent. 0.1 to 40 parts by weight of an adhesion improver containing a silane compound, 0.5 parts by weight of an acidity regulator containing an acid ~11 parts by weight, 2~20 parts by weight of crosslinking agent containing silicate compound, vanadium-based pitting corrosion improvement 0.1 to 14.3 parts by weight of a coating agent and 0.5 to 25 parts by weight of a polymer resin. The composition can be formed from a composition for use.

[0077] As a result, the surface treatment layer contains a trivalent chromium compound, an adhesion improver containing a silane compound, an acidity regulator containing an acid, a crosslinking agent containing a silicate compound, a vanadium-based pitting corrosion improver, and It may contain a polymeric resin.

[0078] The surface treatment layer contains approximately 10 to 70 mg / m of trivalent chromium compound. 2 To form it so that Preferably, about 30 to 60 mg / m 2 It can be formed so that

[0079] The surface treatment layer is approximately 10 to 70 mg / m based on trivalent chromium compounds. 2 By satisfying the It is possible to obtain advantageous advantages in terms of exhibiting excellent physical properties.

[0080] The surface treatment layer can be formed to a thickness of about 0.1 to 50 μm, but is not limited thereto. It is not something that can be done.

[0081] In relation to the physical properties and component analysis of the surface treatment layer (coating layer), FIG. The following Table A and Figure 3 show the EDS component analysis of the surface treatment layer of the present invention. This is the result of the analysis.

[0082] [Table A]

[0083] Referring to Table A, Figures 2 and 3, the cross-sectional shape of the surface treatment layer (coating layer) was observed, and the surface The components constituting the treatment layer were analyzed.

[0084] The results of these analyses showed that the surface treatment layer contained trivalent chromium compounds and silane compounds, which had good adhesion properties. Superplasticizer, acidity regulator containing acid, crosslinking agent containing silicate compound, vanadium-based pitting corrosion improver , polymer resins, etc. can be confirmed to be present.

[0085] The method for producing a steel sheet of the present invention comprises forming a zinc plating layer on a steel sheet base material, and then applying a surface treatment agent to the zinc plating layer. The steps of coating and drying the composition may be included.

[0086] The method for coating the surface treatment composition may be a commonly used coating method. There are no restrictions.

[0087] For example, the coating method may be roll coating, bar coating, spraying, dipping, or spraying. This can be done by either squeezing or immersion squeezing.

[0088] After coating the surface treatment composition, drying is not limited under normal conditions. For example, drying can be carried out at a temperature of about 40 to 200°C.

[0089] The steel sheet using the surface treatment composition of the present invention has a solution stability rating of △V = (Vl - V i) / Vi × 100(%), △V is less than 20(%), but when visually observed, No turbulence phenomenon was observed.

[0090] In addition, the steel plate is a steel plate with a white finish based on ASTM B117, which is an evaluation standard for plate corrosion resistance. When measuring the rust occurrence rate, the time required for white rust to occur is 144 hours or more.

[0091] For example, the white rust occurrence time is 144 to 300 hours, 144 to 250 hours, and 144 to 2 It can show 00 hours.

[0092] In addition, the steel plate is evaluated as not generating white rust or, even if white rust does occur, , occurred very minutely.

[0093] Furthermore, the steel sheet satisfied the evaluation standard of ΔE≦2 for pipe-making oil penetration resistance.

[0094] For example, 0<ΔE≦2 and 0<ΔE≦1.5 can be satisfied.

number

[0095] In the formula, L* is lightness, a* is green, red coordinates, b* is yellow, b The color coordinates are in the Lue system (CIE Lab color space standard).

[0096] Furthermore, the steel sheet satisfied the evaluation criteria for alkali resistance of ΔE≦2. For example, 0<ΔE ≦2, 0<△E≦1.5 can be satisfied.

[0097] In addition, the steel plate is evaluated for pitting corrosion resistance by showing that the number of pitting corrosion defects on the surface is 20 or less. For example, the number of pitting defects was 0 to 20, 0 to 15, 0 to 10, 0 to 7 It may be indicated as 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 39, 31,

[0098] In addition, the steel plate was rubbed according to the evaluation criteria for foreign matter defects, and then the whiteness of the gauze (△L = L be fore -L after ) , △L≦2.5 is satisfied. For example, 0<△L≦2 0.5, 0<△L≦2.0, 0<△L≦1.8, 0<△L≦1.4 can be satisfied .

[0099] Figure 1 shows a highly corrosion-resistant plated steel sheet (left) with pitting corrosion and a surface treatment composition of the present invention. This is a photo of the coated, highly corrosion-resistant plated steel sheet (right).

[0100] Referring to FIG. 1, the surface-treated highly corrosion-resistant plated steel sheet of the present invention does not suffer from pitting corrosion. It can be confirmed that no foreign matter defects have occurred.

[0101] As described above, the specific surface treatment composition for steel sheets and the steel sheets using the same are as follows. Consider the following example.

[0102] 1. Manufacturing of steel sheet surface treatment compositions Examples and Comparative Examples According to the composition ratios in Tables 1 and 2 below, first, an acidity regulator was added to 100 parts by weight of distilled water. of phosphoric acid, and after adding chromium nitrate, a trivalent chromium compound, The mixture was stirred for 0 minutes.

[0103] The same method is used to improve adhesion. Silane, potassium silicate as a cross-linking agent, and pitting corrosion improver Ammonium metavanadate, organic resin, acrylic emulsion were added at 30 minute intervals while stirring to prepare a surface treatment composition.

[0104] [Table 1]

[0105] [Table 2]

[0106] 2. Physical property evaluation method and results To prepare test specimens, the surface treatment composition prepared above was used as follows: Made it.

[0107] Highly corrosion-resistant hot-dip galvanized steel sheet (Zn-Al-Mg) was cut into 7cm x 15cm (width x length) pieces. After degreasing, the coating adhesion amount is approximately 50 mg / m2 based on Cr. 2 Bar-code it so that Then, a test specimen was produced.

[0108] 1) Solution stability Immediately after preparing the coating compositions prepared by the above method, the initial viscosity ( Vi) was measured, stored in a 50°C oven for 120 hours, and then frozen at 25°C. After that, the late viscosity (Vl) at 25°C was measured and then substituted into the following formula 1. The evaluation was carried out according to the following evaluation criteria.

[0109] [Formula 1] △V = (Vl - Vi) / Vi × 100 (%)

[0110] <Evaluation criteria for solution stability> ◯: △V was less than 20(%) or no gelation was observed when visually observed. X: When ΔV was 20% or more, gelation was observed by visual observation.

[0111] 2) Plate corrosion resistance The trivalent chromium surface treatment composition was applied according to the method specified in ASTM B117. After that, the rate of white rust formation on the steel sheets over time was measured.

[0112] <Evaluation criteria for plate corrosion resistance> ○: White rust has occurred for 144 hours or more, △: White rust has occurred for 96 hours or more but less than 144 hours X: Time required for white rust to occur was less than 96 hours.

[0113] 3) Corrosion resistance of processed parts The steel sheet treated with the trivalent chromium surface treatment composition was tested using an Erichsen tester. After pushing the specimen up to a height of 6 mm, the degree of white rust formation was measured after 24 hours.

[0114] <Evaluation criteria for plate corrosion resistance> ○: No white rust has occurred or if white rust has occurred it is very fine, △: Circle If fine white rust has formed and some of it has flowed away but has not flowed outside the circle, mark X: White rust has formed , if it flows outside the circle

[0115] 4) Piping oil invasiveness Steel sheets treated with a trivalent chromium surface treatment composition were immersed in pipe-making oil at room temperature for 24 hours. After immersion, the color difference before and after immersion was measured. 411 was used diluted 10% in water.

[0116] <Evaluation criteria for pipe-making oil abrasion> ○:△E≦2, △:2<△E≦3, X:3<△E

[0117] 5) Alkali resistance Steel sheet treated with trivalent chromium surface treatment composition is immersed in alkaline degreasing solution at 60°C for 2 minutes. After that, the color difference before and after air blowing was measured.

[0118] The alkaline degreasing solution is Finecleaner L 4460 from Daihan Packaging Co., Ltd. A: 20g / 2.4L + L4460B 12g / 2.4L (pH=12) was used.

[0119] <Evaluation criteria for alkali resistance> ○:△E≦2, △:2<△E≦4, X:4<△E

[0120] 6) Pitting corrosion resistance The surface of the steel sheet treated with the trivalent chromium surface treatment composition is sprayed with a sprayer or the like to prevent dew from forming. After that, the two steel plates are butted together and wrapped, then placed in a constant temperature and humidity chamber and heated to a high temperature. 8 cycles of 6 hours at high temperature and humidity (42°C, 95%) and 6 hours at low temperature and humidity (15°C, 60%) After the test, the number of pitting defects on the surface was counted.

[0121] To count the number of corrosion pitting defects, the scanning area of ​​the steel plate was 100 × 50 mm. 2 and , 100 times magnification, the corrosion pitting defect area is 29500μm 2 The number of things that are greater than or equal to I counted them.

[0122] <Evaluation criteria for pitting corrosion resistance> ○: Number of pitting corrosion≦20, △:20<number of pitting corrosion≦40, X:40<number of pitting corrosion

[0123] 7) Foreign matter defects To evaluate the inclusion defects of steel sheets treated with trivalent chromium surface treatment compositions, a surface area of ​​approximately 4cm 2 After covering the probe with white gauze, a 10 kg weight was placed on the probe. After rubbing the gauze back and forth 100 times, the whiteness of the gauze before and after rubbing (△L = L before -L after ) values ​​were measured.

[0124] In order to simulate high humidity conditions, the steel plate and probes were placed in a humidity chamber. The humidity was maintained at 95% or higher using a humidifier, and friction evaluation was performed.

[0125] <Criteria for foreign substance defect evaluation> ○:△L≦2.5, △:2.5<△L≦5, X:5<△L

[0126] The results of measuring the physical properties of the surface-treated steel sheets produced as above are shown in Tables 3 and 4 below.

[0127] [Table 3]

[0128] [Table 4]

[0129] As shown in Table 3 above, in Examples 1 to 15 according to the present invention, the solution stability, plate resistance, Excellent corrosion resistance, corrosion resistance at processed parts, resistance to oil intrusion in pipe manufacturing, resistance to alkalis, pitting corrosion, and foreign matter resistance. It is clear that the defect has been improved.

[0130] However, as shown in Table 4, in the case of Comparative Example 1, the content of trivalent chromium compounds was insufficient, and Corrosion resistance is poor due to the barrier effect, and corrosion resistance of flat plates and processed parts is poor. It can be seen that the corrosion resistance and pitting corrosion resistance are insufficient.

[0131] In the case of Comparative Example 2, the content of trivalent chromium compounds was too high, which caused foreign matter defects. I understand.

[0132] In the case of Comparative Example 3, the content of the adhesion improver was insufficient, and the corrosion resistance of the flat plate, the corrosion resistance of the processed part, and the pitting corrosion It is clear that the corrosion resistance is insufficient and foreign matter defects have occurred.

[0133] In the case of Comparative Example 4, the content of the adhesion promoter was too high, and the processing was affected by the remaining unreacted silane. It can be seen that the surface corrosion resistance and pitting corrosion resistance are insufficient.

[0134] In the case of Comparative Example 5, the content of the acidity regulator was insufficient, resulting in poor solution stability. Even with coating, the corrosion resistance of flat plates, processed parts, and oil penetration resistance of pipes are insufficient. .

[0135] In the case of Comparative Example 6, the content of the acidity regulator was too high, resulting in insufficient corrosion resistance in the processed area and pitting corrosion resistance. It is clear that this is the case.

[0136] In the case of Comparative Example 7, the content of the crosslinking agent is insufficient, and the corrosion resistance of the processed part and the pitting corrosion resistance are insufficient. It can be seen that foreign matter defects have occurred.

[0137] In Comparative Example 8, the content of crosslinker was too high, and the solution stability was insufficient due to unbound silicate. Even after coating, it has excellent corrosion resistance for flat plates, processed parts, oil penetration resistance for pipes, and pitting corrosion resistance. It is clear that corrosion resistance is insufficient.

[0138] In the case of Comparative Example 9, the content of the pitting corrosion improver was insufficient, and it was found that the pitting corrosion resistance was insufficient. Light.

[0139] In the case of Comparative Example 10, the content of the pitting corrosion improver was too high, resulting in insufficient solution stability and coating failure. Even if the steel is polished, the corrosion resistance of flat plates, processed parts, oil penetration resistance in pipe manufacturing, and pitting corrosion resistance may be insufficient. I understand.

[0140] In the case of Comparative Example 11, the content of the organic resin was insufficient, and the coating film was not formed sufficiently. It is clear that the corrosion resistance, resistance to pipe-making oil, and resistance to alkali are insufficient.

[0141] In the case of Comparative Example 12, the content of the organic resin was too high, and the trivalent chromium compound was relatively insufficient. It can be seen that depending on the material, the corrosion resistance of flat plates, corrosion resistance of processed parts, and pitting corrosion resistance are insufficient.

[0142] As described above, the present invention has been described with reference to the exemplary drawings. The present invention is not limited to the embodiments and drawings disclosed herein, but is within the scope of the technical concept of the present invention. It is obvious that various modifications can be made by those skilled in the art. While the embodiments of the present invention have been described above, the effects of the configuration of the present invention have been explicitly described and explained. Even if there is no such effect, it goes without saying that the foreseeable effect of the configuration should also be recognized. do.

Claims

1. trivalent chromium compounds; an adhesion promoter containing a silane compound; acidity regulators containing acids; a crosslinking agent comprising a silicate compound; Vanadium-based pitting corrosion improver; Polymer resin; and, Contains solvents, A composition for surface treatment of steel sheets.

2. The trivalent chromium compounds include chromium sulfate, chromium nitrate, chromium phosphate, chromium fluoride, and and chromium chloride, The surface treatment composition for steel sheets according to claim 1 .

3. The adhesion improver containing the silane compound is preferably vinyl methoxy silane, vinyl trimethoxy silane, vinyl trimethoxy silane, vinyl ... Silane, vinyl epoxy silane, vinyl triepoxy silane, 3-aminopropyl triethoxysilane 3-Glycidoxypropyltrimethoxysilane, 3-Glycidoxypropyltrimethoxysilane, 3-Metaglyoxypropyl Pyrtrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane N-(3-(trimethoxysilyl)propyl)ethyl Benzenediamine (AEAPTMS), 2-(3,4-epoxycyclohexyl)ethyltrimethylsilane Triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriepoxysilane, 3 -(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxy 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propyl propylmethyldiethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldimeth ethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane Silane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl-3- N-(2-aminoethyl-3-aminopropyl)methyldimethoxysilane, diethylenetriaminopropyltrimethoxysilane, 3-urea Idopropyltrimethoxysilane, and N-phenylaminopropyltrimethoxysilane Including one or more of the following: The surface treatment composition for steel sheets according to claim 1 .

4. The acid-containing acidity regulator may be phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, or ammonium phosphate. ((NH ４ ) ２ HPO ４ , (NH ４ ) H ２ P.O. ４ ), monobasic phosphate (NaH ２ P.O. ４ ), Dibasic phosphate (Na ２ HPO ４ ), phytic acid, glycol acid, lactic acid, and acetic acid, The surface treatment composition for steel sheets according to claim 1 .

5. The crosslinking agent containing a silicate compound is sodium silicate (Sodium silicate ate), calcium silicate, potassium silicate Potassium silicate, Aluminum silicate Lithium silicate, Lithium polysilicate olicate), tetramethyl orthosilicate silicate), and tetraethyl orthosilicate thosilicate), The surface treatment composition for steel sheets according to claim 1 .

6. The vanadium-based pitting corrosion improver is vanadium pentoxide (V ２ O ５ ), Metavanadium Acid (HVO ３ ), ammonium metavanadate, potassium metavanadate, metavanadate sodium vanadium oxytrichloride (VOCl ３ ), vanadium trioxide (V ２ O ３ ), vanadium dioxide (VO ２ ), vanadium oxysulfate (VOSO ４ ), Oxygen Vanadium oxalate [VO(COO) ２ ], vanadium oxyacetylacetonate [VO (OC(CH ３ ) = CHCOCH ３ )) ２ ], vanadium acetylacetonate [V(O C(CH ３ ) = CHCOCH ３ )) ３ ], vanadium trichloride (VCl ３ ), vanadium sulfate M (VSO ４ ・8H ２ O), vanadium dichloride (VCl ２ ), and vanadium oxide (VO ) including one or more of The surface treatment composition for steel sheets according to claim 1 .

7. The polymer resin may be a cationic polyurethane resin, a nonionic polyurethane resin, a cat ... ionic acrylic resin and nonionic acrylic resin, The surface treatment composition for steel sheets according to claim 1 .

8. For 100 parts by weight of solvent 0.5 to 17 parts by weight of a trivalent chromium compound; 0.1 to 40 parts by weight of an adhesion improver containing a silane compound; 0.5 to 11 parts by weight of an acidity regulator containing an acid; 2 to 20 parts by weight of a crosslinking agent containing a silicate compound; 0.1 to 14.3 parts by weight of a vanadium-based pitting corrosion improver; and Contains 0.5 to 25 parts by weight of a polymer resin; The surface treatment composition for steel sheets according to claim 1 .

9. Steel plate base material; a zinc plating layer disposed on the steel plate base material; and a surface treatment layer disposed on the zinc plating layer; The surface treatment layer is Trivalent chromium compounds, adhesion improvers containing silane compounds, acidity regulators containing acids, silicates a crosslinking agent containing a compound, a vanadium-based pitting corrosion improver, and a polymer resin; steel plate.

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