JP4983078B2 - Surface treatment agent for galvanized steel and surface-treated galvanized steel sheet - Google Patents

Description

  The present invention relates to a chromium-free surface treatment agent capable of imparting excellent corrosion resistance to a zinc-based plated steel material, and a surface-treated zinc-based plated steel plate treated with this surface treatment agent.

  Zinc-based plated steel sheets are widely used in various applications such as building materials, automobiles, home appliances, and office equipment. In particular, surface-treated steel sheets obtained by subjecting zinc-based plated steel sheets to chromate treatment have been widely used in automobiles, home appliances, office equipment and motor products used therein that require corrosion resistance. Chromate has the effect of improving the corrosion resistance of the galvanized steel sheet by its self-healing action. However, in order to perform the chromate treatment, a special waste water treatment specified in the Water Pollution Control Law is required, which causes an increase in manufacturing cost. For this reason, the surface treatment technique which can ensure the corrosion resistance of a zinc-plated steel plate without using chromium or a chromium compound is calculated | required.

  In recent years, office equipment such as personal computers and copiers, home appliances such as air conditioners, and parts such as motors used therein have good corrosion resistance without containing chromium in the coating, and surface electric There is a demand for a surface-treated steel sheet with low resistance. This is because a steel plate having a low surface electrical resistance, that is, a steel plate having good conductivity, has an effect of preventing noise leakage due to electromagnetic waves. Therefore, in such an application, it is important to make the corrosion resistance and conductivity of the surface-treated steel sheet compatible.

From this point of view, many surface treatment techniques that do not use chromium or chromium compounds (chromium-free) have been proposed.
For example, Patent Document 1 discloses (a) an anionic component (for example, fluorotitanic acid represented by TiF ₆ ^2- ) composed of at least four fluorine atoms and an element such as titanium or zirconium, and (b) cobalt. Surface treatment technology using a composition containing a cationic component such as magnesium, (c) a free acid for pH adjustment, and (d) an organic resin has been proposed.
Patent Document 2 describes (a) Al phosphate compound, (b) one or more of Mn, Mg, Ca and Sr compounds, (c) SiO ₂ sol, and (d) water-based organic resin emulsion. Containing surface treatment compositions have been proposed.

Patent Document 3 includes (a) a resin having a polyhydroxy ether segment and a copolymer segment of an unsaturated monomer, (b) phosphoric acid, and (c) calcium, cobalt, iron, manganese, zinc, and the like. Surface treatment compositions containing metal phosphates have been proposed.
Patent Document 4 includes (a) Al (C ₅ H ₇ O ₂ ) ₃ , V (C ₅ H ₇ O ₂ ) ₃ , VO (C ₅ H ₇ O ₂ ) ₂ , Zn (C ₅ H ₇ O _2). ) ₂ , Zr (C ₅ H ₇ O ₂ ) ₂ containing one or more metal acetylacetonates, (b) water-soluble inorganic titanium compounds, water-soluble inorganic zirconium compounds containing one or more compounds Surface treatment liquids have been proposed.

  According to these proposals, when a sufficient amount of surface treatment agent (coating agent, coating agent) is coated on the metal plate, that is, when a sufficiently thick film is formed, the corrosion resistance is reasonable. Is obtained. However, when a film that exposes a part of the convex portion of the metal plate is formed or the film thickness is too thin, the corrosion resistance is extremely insufficient. That is, corrosion resistance is exhibited only when the coverage of the surface treatment agent on the metal plate is 100%, but sufficient corrosion resistance cannot be obtained when the coverage is less than 100%. In addition, since these surface treatment agents do not contain a conductive substance, there is a disadvantage in that the conductivity is reduced when the surface treatment agent is coated over the entire surface. On the other hand, if the film thickness is reduced in order to increase the conductivity, the corrosion resistance is deteriorated.

  Patent Document 5 discloses a coating agent containing a specific aqueous organic resin, wherein (a) a thiocarbonyl group-containing compound, (b) phosphate ion, (c) water-dispersible silica, (d) a silane coupling agent. Alternatively, a method of coating a zinc-coated steel with an aqueous rust-proof coating agent containing the hydrolysis condensate has been proposed. Sulfides such as thiocarbonyl group-containing compounds used in this method have the property of easily adsorbing on the surface of metals such as zinc, and their tautomeric thiol group ions are synergistic with phosphate ions. Thus, it is adsorbed on the active zinc surface site during coating and exhibits a rust prevention effect. The zinc-based plated steel sheet obtained by this surface treatment method has high corrosion resistance when the surface is coated with a layer having -NCS and -OCS groups, but this layer has a problem that it is not conductive. In addition, when the film thickness is reduced in order to ensure conductivity, a portion not covered with the thiocarbonyl group-containing compound appears, which causes rusting. That is, it is difficult to achieve both corrosion resistance and conductivity even with this method.

  In addition, the above-described five conventional techniques are all based on the idea that the metal surface and the film formed by the surface treatment agent are firmly attached (adhered) at the interface between them. However, when viewed microscopically, the metal surface and the film cannot be completely adhered, so there is a limit to improving the adhesion. In the chromium-free surface treatment technology for galvanized steel sheets, it is thought that the improvement in the denseness of the film, not the adhesion of the surface treatment film, is important for improving the corrosion resistance. The point is not considered at all.

  In addition, if the treatment liquid for surface treatment, including chromate treatment liquid, contains phosphoric acid or the like and has a low pH, and if coating treatment by roll coating or dipping is performed continuously, sludge is contained in the treatment liquid. Will occur. This sludge adheres to the surface of the steel sheet and causes a poor appearance of the steel sheet, and further becomes a microscopically discontinuous film, so that the primary rust resistance is also reduced. In particular, in the case of the roll coating method, the sludge adheres to the coating roll, so that the appearance of the steel sheet and the performance are liable to occur. As a measure to prevent sludge generation, it is conceivable to lower the pH of the solution in order to increase the solubility limit of Zn in the treatment solution. However, if the solution pH is lowered, the etching rate of Zn increases and sludge is generated instead. Will increase the amount. In addition, due to the presence of hydrogen bubbles generated when Zn dissolves during film formation, the continuity of the film may be reduced, and various characteristics such as primary rust resistance may be reduced.

JP-A-5-195244 Japanese Patent Laid-Open No. 11-350157 Japanese Patent Laid-Open No. 11-5010 JP 2000-199077 A JP 2001-164182 A

Therefore, the object of the present invention is to enable stable surface treatment of galvanized steel sheets without generating sludge even when continuously treated, and excellent corrosion resistance comparable to that of general purpose chromate-treated galvanized steel sheets. An object of the present invention is to provide a surface treatment agent capable of obtaining a chromium-free surface-treated galvanized steel sheet having flat plate portion corrosion resistance and post-processing corrosion resistance, conductivity and workability.
Another object of the present invention is to provide a chromium-free surface-treated galvanized steel sheet that has been treated with such a surface treatment agent and has excellent corrosion resistance (corrosion resistance after plate processing, post-processing corrosion resistance), conductivity and workability. There is.

As a result of intensive studies to solve the above problems, the inventors of the present invention contain a specific metal ion, a phosphate ion, an organic resin and a specific chelating agent, and have a pH and free acidity adjusted. The present inventors have found that the above-mentioned problems can be solved by treating a zinc-based plated steel sheet with this surface treating agent, and have completed the present invention.
That is, the gist of the present invention is as follows.
[1] An aqueous solution containing the following components (a) to (d) having a pH of 1 to 4 and a free acidity of 3 to 20 in terms of 0.1 N sodium hydroxide: Surface treatment agent for galvanized steel.
(A) One or more metal ions selected from Al, Mn, Mg, V, and Zn (b) Phosphoric acid: 300 to 1500 masses per 100 mass parts (solid content) of the metal ions in (a) above Parts (solid content)
(C) Organic resin: 5 to 100 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ions of (a) above
(D) One or more selected from N-methyliminodiacetic acid, iminodiacetic acid, 1,2-diaminocyclohexane, arginine, and proline : 10 to 300 with respect to 100 parts by mass (solid content) of the metal ion of (a). Part by mass (solid content)

[2] A surface treatment agent for galvanized steel materials, wherein at least a part of the organic resin is a water-dispersible resin in the surface treatment agent of [1].
[3] The surface treatment agent for galvanized steel material according to the above [1] or [2], further comprising a solid lubricant.
[4] A surface treatment film formed by applying the surface treatment agent according to any one of the above [1] to [3] on the surface of a zinc-based plated steel sheet and drying the surface treatment film, Mainly composed of a reaction product (i) of a phosphate ion and a plating metal and a metal salt (ii) containing one or more metals selected from Al, Mn, Mg, V, and Zn in contact with the plating layer And a surface-treated zinc-based plated steel sheet having a lower layer portion having a thickness of 0.02 to 3 μm containing the organic resin (iii).
[5] The surface treatment agent of any of the above [1] to [3] is applied to the surface of the zinc-based plated steel sheet so that the solid content adhesion amount is 0.05 to 3.0 g / m ² and dried. A method for producing a surface-treated galvanized steel sheet, characterized in that a surface-treated film is formed.

The surface treatment agent of the present invention enables stable surface treatment of a zinc-based plated steel sheet without generating sludge even when continuously treated, and is a chromate-treated zinc-based plated steel sheet for general use while being chromium-free. It is possible to obtain a chrome-free surface-treated zinc-based plated steel sheet having excellent corrosion resistance (corrosion resistance for flat plate portion, corrosion resistance after processing) comparable to that of the steel sheet, and having excellent conductivity and workability.
Therefore, the surface-treated zinc-based plated steel sheet of the present invention treated with such a surface treatment agent has excellent corrosion resistance (flat plate portion corrosion resistance, post-processing corrosion resistance) while being chromium-free, Excellent workability.

Hereinafter, the surface treating agent for galvanized steel material of the present invention will be described.
The surface treatment agent of the present invention is an aqueous solution containing the following components (a) to (d), having a pH of 1 to 4 and a free acidity of 3 to 20 in terms of 0.1 N sodium hydroxide. It is an agent. This surface treatment agent does not contain chromium.
(A) One or more metal ions selected from Al, Mn, Mg, V, and Zn (b) Phosphoric acid: 300 to 1500 masses per 100 mass parts (solid content) of the metal ions in (a) above Parts (solid content)
(C) Organic resin: 5 to 100 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ions of (a) above
(D) One or more selected from amines and derivatives thereof, aminopolycarboxylic acids and amino acids: 10 to 300 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ion of (a)

  The one or more metal ions selected from Al, Mn, Mg, V, and Zn as the component (a) are derived from a metal salt or / and a metal hydroxide added to the treatment agent. It is an ingredient to do. Examples of the metal salt and metal hydroxide include phosphates, nitrates, carbonates, sulfates, acetates, hydroxides containing at least one metal selected from Al, Mn, Mg, V, and Zn. One or more selected from these can be used. Among these, from the viewpoint of ensuring corrosion resistance, a combination of one or more inorganic acid salts of metals selected from Mn, Mg, and V and an inorganic acid salt of Zn, or Mn, Mg, It is particularly preferable to use one or more metal hydroxides selected from V and Zn hydroxide in combination.

The phosphate may be any salt as long as phosphate ions can be liberated in the treatment agent. Examples of the phosphoric acid component include polyphosphoric acid, hypophosphorous acid, pyrophosphoric acid, tripolyphosphoric acid, hexametaphosphoric acid, primary phosphoric acid, secondary phosphoric acid, and tertiary phosphoric acid. When a phosphate is used, it also serves as a supply source of phosphoric acid as the component (b).
The metal ion as the component (a) binds to phosphate ions in the film to form a phosphate, thereby contributing to improvement of corrosion resistance and imparting conductivity to the film.

The phosphoric acid as the component (b) is phosphoric acid such as orthophosphoric acid, polyphosphoric acid, hypophosphorous acid, pyrophosphoric acid, tripolyphosphoric acid, hexametaphosphoric acid, primary phosphoric acid, secondary phosphoric acid, and tertiary phosphoric acid. It may be added as an acid or as a phosphate as described above.
The phosphoric acid in the surface treatment agent reacts with the plating metal dissolved in the treatment agent when the surface treatment agent is brought into contact with the plating surface, and this reaction product is a metal due to the metal ion which is a component of (a). Together with the salt, a thin layer (lower layer portion x to be described later) rich in corrosion resistance that is firmly bonded to the plated surface in the vicinity of the interface with the plated surface is formed.
The blending amount of phosphoric acid as the component (b) in the surface treatment agent is 300 to 1500 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ion as the component (a). And When the blending amount of phosphoric acid with respect to 100 parts by mass of metal ions is less than 300 parts by mass, the component (a) cannot be stably present in the liquid, and precipitation occurs during storage of the liquid. On the other hand, when it exceeds 1500 parts by mass, a lot of free phosphoric acid remains in the film, so that the corrosion resistance decreases.

As the organic resin as the component (c), a water-soluble resin and / or a water-dispersible resin is used. Further, when considering not only the corrosion resistance but also the lubricity, a part or all of the resin is preferably a water dispersible resin. As the water-soluble resin, a polymer of a carboxyl group-containing monomer, a copolymer of a hydroxyl group-containing monomer and a carboxyl group-containing monomer, and the like are particularly preferable, and one or more of these can be used. It is more preferable to use one or more of these in combination with a water-dispersible resin.
Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acid and derivatives thereof. Examples of the ethylenically unsaturated carboxylic acid include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and dicarboxylic acids such as itaconic acid, maleic acid, and fumaric acid. Representative examples of the derivatives include antkari metal salts, ammonium salts, and organic amine salts. Preference is given to acrylic acid and methacrylic acid. These carboxyl group-containing monomers can be used alone or in combination of two or more.

Examples of the hydroxyl group-containing monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, -2,2-bis (hydroxymethyl) ethyl acrylate, (Meth) acrylic acid-2,3-dihydroxypropyl, (meth) acrylic acid-3-chloro-2-hydroxypropyl and other (meth) acrylic acid hydroxy esters, allyl alcohols, N-methylolacrylamide, N-butoxymethylol Mention may be made of monomers having a reducing hydroxyl group, such as hydroxyl group-containing acrylamides such as (meth) acrylamide. Particularly preferred are hydroxyethyl acrylate and hydroxyethyl methacrylate. These hydroxyl group-containing monomers can be used alone or in combination of two or more.
Note that the copolymer of the hydroxyl group-containing monomer and the carboxyl group-containing monomer may be further copolymerized with other polymerizable monomers as long as the properties of the surface treatment film expected in the present invention are maintained. It may be polymerized. Suitable monomers include (meth) acrylic acid esters such as styrenes and methyl methacrylate.

  The organic resin described above can further improve processability and post-processing corrosion resistance by further containing a water-dispersible resin. As the water dispersible resin, a resin that is stable in a low pH acidic aqueous solution (pH: 1 to 4) and can be uniformly dispersed is particularly preferable. As such a thing, what copolymerizes unsaturated monomers other than the monomer containing a carboxyl group or a hydroxyl group with the monomer containing a carboxyl group is mentioned. Examples of the preferred monomer include alkyl esters of methacrylic acid such as styrene, butyl methacrylate, and methyl methacrylate. Examples of the water-dispersible resin that is stable in an acidic aqueous solution having a pH of 1 to 4 and can be uniformly dispersed include, for example, polyesters, acrylics, and urethanes that are conventionally used for surface treatment of metal materials. . Two or more of these can be used in combination.

The water dispersible resin is particularly preferably one having a glass transition temperature (Tg) of 20 to 120 ° C. When the glass transition temperature is 20 ° C. or higher, the dried film is excellent in blocking resistance. On the other hand, when the glass transition temperature is 120 ° C. or lower, since the coating easily follows the deformation of the steel sheet during processing, and the coating is less likely to break, the post-processing corrosion resistance is improved.
The water-dispersible resin preferably has a particle size of 0.1 to 2.0 μm. The press moldability is improved when the particle size of the water-dispersible resin is 0.1 μm or more. On the other hand, when the particle size is 2.0 μm or less, the continuity of the lower layer portion x described later is easily maintained, and all of the corrosion resistance, press formability, and post-processing corrosion resistance are improved.

  The compounding amount of the organic resin as the component (c) in the surface treating agent is 5 to 100 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ion (a). . When the blending amount of the organic resin with respect to 100 parts by mass (solid content) of the metal ions is less than 5 parts by mass, the corrosion resistance is inferior, and the lubricity is also inferior, so that black foreign matter is easily generated during press molding or mold galling is likely to occur. On the other hand, if it exceeds 100 parts by mass, the corrosion resistance tends to be improved, but peeling occurs during press molding, black foreign matter is generated, the post-processing appearance tends to deteriorate, and the conductivity is also lowered.

One or more selected from amines and derivatives thereof, aminopolycarboxylic acids, and amino acids as the component (d) are added as chelating agents for metal ions (plating metal) dissolved from the plating surface. It is.
As a method for applying the surface treatment agent to the zinc-based plated steel sheet, a dipping method or a roll coating method is generally employed. In this case, if the surface treatment agent has a low pH, the plating metal (usually Zn) dissolves in the applied surface treatment agent and the pH rises. As a result, a precipitate is generated when the pH becomes higher than the dissolution stable pH of the metal component in the surface treatment agent, and this precipitate becomes sludge in the surface treatment agent. When such sludge in the surface treatment agent adheres to the steel sheet to be treated directly or via a coater roll, it causes poor appearance and poor performance, and further accumulates in the coater pan, making continuous production impossible. There is also.

  In order to prevent the above problems, the dissolution of the plating metal is prevented as much as possible by increasing the pH of the surface treatment agent. On the other hand, the pH is increased in order to increase the dissolution limit (pH upper limit) of the plating metal with respect to the surface treatment agent. It is necessary to achieve the contradictory phenomenon of lowering, and this cannot be achieved by the conventional technology. As a result of intensive studies, when an appropriate amount of one or more selected from amines and derivatives thereof, aminopolycarboxylic acids, and amino acids is added to the surface treatment agent, this component is pre-adsorbed on the plating surface, so that the plating metal Excessive etching is prevented, and the same component acts as a chelating agent in the surface treatment agent, and chelates metal ions (plating metal) dissolved from the plating surface to effectively improve the stability of the surface treatment agent. I found out.

  Examples of the component (d) exhibiting such effects include ethylenediamine, N-methylethylenediamine, N-ethylethylenediamine, Nn-propylethylenediamine, N-isopropylethylenediamine, N- (2-hydroxyethyl) ethylenediamine, N, N dimethylethylenediamine, N, N′dimethylethylenediamine, N, N′-dimethylethylenediamine, N, N′-di (2-hydroxyethyl) ethylenediamine, N, N, N ′, N′-tetramethylethylenediamine, 1 , 2-diaminopropane, meso-2,3diaminobutane, rac-2,3-diaminobutane, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, cis-1,2-diaminocyclohexane, trans-1,2- Diaminocyclohexane, Triethylenediamine, 1,2,3 triaminopropane, 1,3-diamino-2-aminomethylpropane, diethylenetriamine, 3,3'-diaminodipropylamine, triethylenetetraamine, 2,2 ', 2 "-tri Aminotriethyleneamine, 2-hydroxyethylamine, 2-methoxyethylamine, 2,2'-dihydroxydiethylamine, 2,2 ', 2 "-trihydroxytriethylamine, di (2-aminoethyl) ether, pyridine, 2-aminomethyl Pyridine, 2,2'-aminoethylpyridine, pyridine-2-carboxylic acid, pyridine-2,3-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, hydrazine nicotinate, isonicotitine Acid hydrazide, pyridoxamine, piperidine, pipette Amines such as gin-2,6 dicarboxylic acid, imidazole, histamine, 3-methylhistamine and derivatives thereof, iminodiacetic acid, iminodipropionic acid, N-methyliminodiacetic acid, N- (3,3'-dimethylbutyl) iminodiacetic acid, Phenyliminodiacetic acid, hydroxyethyliminodiacetic acid, hydroxyethyliminodipropionic acid, hydroxypropyliminodiacetic acid, 2-hydroxycyclohexyliminodiacetic acid, methoxyethyliminodiacetic acid, 2-hydroxybenzyliminodiacetic acid, N- (o -Carboxyphenyl) iminodiacetic acid, N- (m-carboxyphenyl) iminodiacetic acid, N- (p-carboxyphenyl) iminodiacetic acid, N- (carbamoylmethyl) iminodiacetic acid, cyanomethyliminodiacetic acid, aminoethyliminodiacetic acid, 2- Toxicarbonylaminoethyliminodiacetic acid, phosphonomethyliminodiacetic acid, phosphoethyliminodiacetic acid, nitrilotriacetic acid, carboxyethyliminodiacetic acid, carboxymethyliminodipropionic acid, nitrilotripropionic acid, N, N'-ethylenediaminediacetic acid, Ethylenediamine-N, N'dipropionic acid, N, N'-di (hydroxyethyl) ethylenediaminediacetic acid, Nn-butylethylenediaminetriacetic acid, N-cyclohexylethylenediaminetriacetic acid, N- (o-hydroxycyclohexyl) ethylenediaminetriacetic acid Acetic acid, N'-hydroxyethyl-N, N, N'-triacetic acid, benzylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, ethylenediamine-N, N'-diacetic acid N, N'-dipropionic acid, ethylenediamine -N, N'-diacetic acid N, N'-di (2-propionic acid), ethylenediaminetetrapropionic acid, 1,2-propiondiaminetetraacetic acid, trimethylenediaminetetraacetic acid, tetramethylenediaminetetraacetic acid, pentamethylene Diaminetetraacetic acid, hexamethylenediaminetetraacetic acid, trans-cyclohexane-1,2-diaminetetraacetic acid, 1,3,5-triaminocyclohexanehexaacetic acid, ethyletherdiaminetetraacetic acid, diethyltriaminepentaacetic acid, glycol etherdiaminetetraacetic acid Aminopolycarboxylic acids such as glycine, sarcosine, glycine methyl ester, alanine, valine, norleucine, leucine, phenylalanine, tyrosine, serine, threonine, cysteine, methionine, aspartic acid, aspart Ragin, glutamic acid, 1,2-diaminopropionic acid, ornithine, lysine, arginine, proline, histidine, N- ethyl glycine, glycyl alanine, amino acid and its derivatives, such as reduced glutathione and the like. These components can be used alone or in combination of two or more.

  The compounding amount in one or more kinds of surface treating agents selected from amines and derivatives thereof, aminopolycarboxylic acids and amino acids as the component (d) is the metal ion 100 as the component (a). It is set as 10-300 mass parts (solid content) with respect to a mass part (solid content). When the blending amount of the component (d) with respect to 100 parts by mass (solid content) of metal ions is less than 10 parts by mass, sufficient prior adsorption to the plating surface and chemical stability cannot be obtained, while on the other hand, when it exceeds 300 parts by mass. A large amount of the component (d) may remain in the film, which may reduce the corrosion resistance.

Furthermore, the surface treatment agent may contain a solid lubricant for the purpose of improving press moldability.
Examples of the solid lubricant include polyolefin wax (for example, polyethylene wax), paraffin wax (for example, synthetic paraffin and natural paraffin), fluororesin wax (for example, polytetrafluoroethylene), fatty acid amide compound (for example, , Stearamide, palmitate, etc.), metal soaps (eg, calcium stearate, lead stearate, etc.), metal sulfides (eg, molybdenum disulfide, tungsten disulfide, etc.), graphite, graphite fluoride, boron nitride One or more of polyalkylene glycols and alkali metal sulfates can be used, and among them, fluororesin waxes such as polyethylene wax and PTFE (polytetrafluoroethylene) are particularly preferable. Further, as the solid lubricant, those having low pH stability and a softening temperature of 100 ° C. or higher are preferable. From this viewpoint, polyolefin waxes and metal soaps are preferable.
The blending amount of the solid lubricant in the surface treatment agent is 5 to 50 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ion that is the component (a). If the blending amount of the solid lubricant with respect to 100 parts by mass (solid content) of metal ions is less than 5 parts by mass, the effect of improving lubricity and press formability cannot be obtained sufficiently, whereas if it exceeds 50 parts by mass, the film is soft. Thus, the appearance after processing deteriorates.

  When the surface treatment agent (treatment liquid) contains a water-dispersible resin or solid lubricant, since these are dispersed in the liquid, the lower layer portion of the surface treatment film formed by contact between the treatment agent and the plating surface x (a layer portion in contact with the plating layer, which is a metal salt containing a reaction product (i) of phosphate ions and plating metal and one or more metals selected from Al, Mn, Mg, V, and Zn It is also dispersed and contained in the lower layer portion (mainly comprising (ii) and containing the organic resin (iii)). For this reason, by containing the water dispersible resin, uniform lubricity can be ensured in any part in the depth direction of the lower layer part x. Moreover, lubricity is further improved by containing a solid lubricant. By these actions, press formability and post-processing corrosion resistance are ensured. Therefore, the surface treatment agent is particularly desirable that (1) at least a part (preferably all) of the organic resin contained is a water-dispersible resin, or (2) contains a solid lubricant. 3) It is preferable that at least a part (preferably all) of the organic resin is a water-dispersible resin and contains a solid lubricant.

The surface treatment agent may contain a surfactant from the viewpoint of prevention of foaming when applied to the surface to be treated (zinc-based plated steel sheet surface) and stability of the treatment liquid. The surfactant is not particularly limited as long as it is stable under an environment of pH 1 to 4, and examples thereof include nonionic surfactants.
Moreover, in order to provide other performance, you may make the surface treatment agent contain various additives used by normal surface treatment.

The surface treating agent of the present invention is obtained by dissolving or dispersing the above-described components in water as a solvent, and is usually an aqueous solution having a solid content concentration of about 5 to 25 mass%. If the solid content concentration is too low, it becomes difficult to secure the amount of adhesion when applied to a zinc-based plated steel sheet or the like. On the other hand, if the solid content concentration is too high, the treatment liquid stability tends to be inferior.
The surface treating agent of the present invention needs to have a pH of 1 to 4 and a free acidity of 3 to 20 in terms of 0.1 N sodium hydroxide. When the pH of the surface treatment agent is less than 1, the plating metal dissolves excessively, resulting in thinning of the plating layer, or the reaction product of the plating metal and phosphate ions is re-dissolved, resulting in improved corrosion resistance. There may not be. On the other hand, when pH exceeds 4, the reaction product of a plating metal and a phosphate ion will not be formed, and corrosion resistance will fall remarkably. Therefore, the pH of the surface treatment agent is set to 1 to 4. In order to adjust the pH of the surface treatment agent to 1 to 4, a hydroxide such as NaOH or KOH, an amine, or the like can be used as a neutralizing agent.

In the present invention, “0.1N sodium hydroxide equivalent free acidity” refers to 0.1N water required for dripping 3 drops of bromophenol blue into 10 mL of the surface treatment agent to change the color from yellow to blue. It was the amount (mL) of the aqueous sodium oxide solution, and was labeled as an anonymous number.
As described above, even if the pH of the surface treatment agent is adjusted to the range of 1 to 4, the corrosion resistance is reduced if the free acidity is outside the range of 3 to 20 in terms of 0.1 N sodium hydroxide. That is, when the free acidity is less than 3, the thickness of the lower layer portion x of the surface treatment film becomes too thin. On the other hand, when the free acidity exceeds 20, the continuity of the lower layer part x is inhibited. From such a viewpoint, the more preferable free acidity in terms of 0.1 N sodium hydroxide is 5 to 15. In the case of the same pH, the use of pyrophosphoric acid is effective for reducing the free acidity.

Hereinafter, the surface-treated zinc-based plated steel sheet of the present invention will be described in detail.
The surface-treated zinc-based plated steel sheet of the present invention has a surface-treated film formed by applying the above-described surface treatment agent to the surface of the zinc-based plated steel sheet and drying it.
Although there is no special restriction | limiting in the kind of galvanized steel plate used by this invention, For example, galvanized steel plate, Zn-Ni alloy plating steel plate, Zn-Fe alloy plating steel plate (electroplating steel plate, galvannealed steel plate), Zn-Cr alloy plated steel sheet, Zn-Mn alloy plated steel sheet, Zn-Co alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet, Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn- Al alloy-plated steel sheet (for example, Zn-5% Al alloy-plated steel sheet, Zn-55% Al alloy-plated steel sheet), Zn-Mg alloy-plated steel sheet, Zn-Al-Mg alloy-plated steel sheet (for example, Zn-6% Al- 3% Mg alloy-plated steel sheet, Zn-11% Al-3% Mg alloy-plated steel sheet), and metal oxides and polymers in the plating film of these plated steel sheets. Or the like can be used dispersed zinc composite-plated steel sheet (for example, Zn-SiO ₂ dispersion plating steel plate).

In addition, among the above-described plating, a multi-layer plated steel sheet in which two or more layers of the same type or different types are plated can also be used.
Moreover, as a plated steel plate, the steel plate surface may be previously plated with lightness such as Ni, and various plating as described above may be performed thereon.
As a plating method, any feasible method among an electrolytic method (electrolysis in an aqueous solution or electrolysis in a non-aqueous solvent), a melting method, and a gas phase method can be adopted.
Furthermore, in order to prevent blackening of the plating, about 1 to 2000 ppm of one or more trace elements of Ni, Co, Fe are deposited in the plating film, or one of Ni, Co, Fe is deposited on the surface of the plating film. These elements may be deposited by performing a surface conditioning treatment with an alkaline aqueous solution or an acidic aqueous solution containing the above.

  The surface treatment film formed on the surface of the galvanized steel sheet is selected from the reaction product (i) of phosphate ion and plating metal, and Al, Mn, Mg, V, and Zn in contact with the plating layer. It has a lower layer portion x mainly composed of a metal salt (ii) containing one or more metals and containing an organic resin (iii) and having a thickness of 0.02 to 3 μm.

This lower layer part x is defined as follows.
In the lower layer part x mainly composed of the reactant (i) and the metal salt (ii), the metal ions (plating metal) dissolved from the plating surface and diffused into the surface treatment agent and the phosphate ions in the surface treatment agent are Since the metal ions (component (a) described above) that react and are originally contained in the surface treatment agent are formed by reacting with phosphate ions or the like, the thickness thereof is determined by glow discharge spectroscopy (hereinafter, It can be measured by analysis of the metal component in the film thickness direction by GDS).

  FIG. 1 shows the result of component analysis in the direction of the thickness of the surface-treated film by GDS on the surface-treated zinc-based plated steel sheet of the present invention obtained by applying and drying a surface treatment agent containing Mg and Mn as metal ions. An example is shown. In this GDS, “RF-GDS3860” (trade name) manufactured by Rigaku Corporation was used, and measurement was performed under conditions of an anode diameter of 4 mm, 20 W, and an Ar gas flow rate of 300 cc / min. In FIG. 1, the sputtering time can be associated with the depth (thickness) direction position of the film on the basis of the iron-equivalent sputtering speed, and each element at the position in the depth (thickness) direction of the film. The abundance can be known from the signal intensity of. In FIG. 1, the sputtering time of 0 seconds is the outermost surface of the film, and in the depth region extending from the outermost surface of the film to the lower layer part x, the metal components (Mg, Mn) derived from the surface treatment agent coexist with the plated metal (Zn). You can see that In this depth region, the carbon component (C) peak of the organic resin is present on the surface layer side of the peak of the metal component (Mg, Mn), but coexists with the metal component (Mg, Mn).

  Here, the “lower layer portion x” of the surface treatment film in the present invention refers to the metal component derived from the surface treatment agent (component (a) described above, Mg in FIG. 1) in the GDS measurement results as shown in FIG. , Mn) from the depth position P1 at which the signal intensity reaches a peak, the depth position P2 at which the signal intensity becomes 1/10 of the peak value (in general, the depth position P2 is an interface with the plating surface). Can be considered). The region deeper than the depth position P1 is a layer mainly composed of a reaction product (i) of a phosphate ion and a plating metal and a metal salt (ii) and coexisting with an organic resin. This is because it is considered to contribute greatly to lubricity.

  The surface treatment film in the present invention is a result that the lower layer portion x mainly composed of the reactant (i) and the metal salt (ii) generated by strong ionic bonding forms a strong adhesion state with the zinc-based plating layer. It is thought that excellent corrosion resistance is expressed. In order to achieve such a tight adhesion state, the lower layer portion x needs to have a thickness of 0.02 to 3 μm. When the thickness of the lower layer portion x is less than 0.02 μm, the bonding between the plating layer and the surface treatment film becomes insufficient, and the corrosion resistance is deteriorated. On the other hand, when the thickness exceeds 3 μm, peeling of the lower layer portion x is likely to occur when processing such as bending is performed, the adhesiveness of the surface treatment film is deteriorated, and press formability is deteriorated. As a result, the appearance after processing also deteriorates. From the above viewpoint, the more preferable thickness of the lower layer part x is 0.1 to 1.5 μm. As will be described later, the thickness of the lower layer portion x can be adjusted by the coating amount of the surface treatment agent.

Next, the manufacturing method of a surface treatment zinc-plated steel plate is demonstrated.
The surface-treated zinc-based plated steel sheet of the present invention is coated with the surface treatment agent described above on the surface of the zinc-based plated steel sheet so that the solid content is 0.05 to 3.0 g / m ² , dried, and the surface It can be manufactured by forming a treatment film.
Usually, the surface treatment agent is applied to the surface of the galvanized steel sheet by a coating method such as roll coating, spray coating, brush coating or curtain flow. Here, the thickness of the lower layer part x can be 0.02-3 micrometers by apply | coating a surface treating agent so that solid content adhesion amount may be 0.05-3.0 g / m < ² >. Moreover, in order to make the thickness of the lower layer part x 0.1-1.5 micrometers, it is preferable to apply | coat a surface treating agent so that solid content adhesion amount may be 0.3-1.5 g / m < ² >.

  After applying such a surface treating agent, it is dried. In this drying step, it is preferable to heat the steel sheet to 50 to 100 ° C. to dry the surface treating agent. If the heating temperature (steel plate temperature) is 50 ° C. or higher, the moisture in the film hardly remains, and the corrosion resistance is improved. On the other hand, when the heating temperature (steel plate temperature) is 100 ° C. or lower, phosphoric acid is prevented from being orthorectified, so that the free acidity of the surface treatment agent is easily maintained, and the corrosion resistance is also improved. As the heating means, a hot stove, a dryer, a high-frequency heating furnace, an infrared heating furnace, or the like can be used.

Metal salts or metal hydroxides composed of the metal species shown in Table 1 and Table 3, organic resins shown in (1) below (both water-dispersible resins), phosphoric acid shown in (2), and (3) The water-based surface treatment agent is prepared by appropriately blending the chelating agent shown in the same formula (4) and the aqueous surface treatment agent, and this surface treatment agent is sprayed on the surface of the zinc-based plated steel plate shown in (5) below. Was applied. Then, it heated so that ultimate plate temperature might be 60 degreeC in 5 second, and formed the surface treatment film.
(1) Organic resin (Tg = glass transition temperature)
Resin A: Urethane resin emulsion (Tg: 80 ° C., dispersed particle size: 0.2 to 0.4 μm)
Resin B: acrylic resin emulsion (Tg: 100 ° C., dispersed particle size: 0.3 to 0.4 μm)
Resin C: Polyethylene resin emulsion (Tg: 80 ° C., dispersed particle size: 0.1 to 0.2 μm)
Resin D: Acrylic resin emulsion (Tg: 30 ° C., dispersed particle size: 0.1 to 0.2 μm)

(2) Phosphoric acid-Phosphoric acid I: Polyphosphoric acid-Phosphoric acid II: Pyrophosphoric acid-Phosphoric acid III: Tripolyphosphoric acid-Phosphoric acid IV: Hypophosphorous acid (3) Chelating agent-Chelating agent I: N-methyliminodi Acetic acid Chelating agent II: Iminodiacetic acid Chelating agent III: 8-hydroxyquinoline Chelating agent IV: 1,2-diaminocyclohexane Chelating agent V: L-arginine Chelating agent VI: L-proline ( 4) Solid lubricant-Solid lubricant E: Polyethylene wax (softening temperature: 110 ° C)
Solid lubricant F: Fluorine wax (PTFE) (softening temperature: 160 ° C.)

(5) Galvanized steel sheet ・ Plated steel sheet a: Electrogalvanized steel sheet (plate thickness: 1 mm, plating adhesion: 20 g / m ² )
Plated steel plate b: Electro-zinc-nickel plated steel plate (plate thickness: 1 mm, plating adhesion amount: 20 g / m ² , Ni: 12 mass%)
Plated steel sheet c: Hot dip galvanized steel sheet (plate thickness: 1 mm, plating adhesion: 60 g / m ² )
Plated steel sheet d: Alloyed hot-dip galvanized steel sheet (plate thickness: 1 mm, plating adhesion: 60 g / m ² , Fe: 10 mass%)
-Plated steel sheet e: Zinc-5% aluminized steel sheet (plate thickness: 1 mm, plating adhesion: 60 g / m ² , Al: 5 mass%)
Plated steel sheet f: Zinc-55% aluminum plated steel sheet (plate thickness: 1 mm, plating adhesion: 60 g / m ² , Al: 55 mass%)

About the surface treatment steel plate of each obtained Example, the thickness of the lower layer part x of a surface treatment film was measured by GDS. As a measuring device, “RF-GDS3860” (trade name) manufactured by Rigaku Corporation was used, and measurement was performed under the conditions of an anode diameter of 4 mm, 20 W, and an Ar gas flow rate of 300 cc / min.
About each Example, the zinc test | inhibition characteristic and chemical-solution stability of a surface treating agent, the flat plate electroconductivity of a surface-treated steel plate, a plane part corrosion resistance, post-processing corrosion resistance, and workability were evaluated with the following test methods. In addition, about evaluation of the zinc melt | dissolution suppression characteristic of a surface treating agent, it performed using the pure zinc electroplating steel plate.

(1) Zinc Dissolution Inhibiting Characteristics A 50 mm × 100 mm pure zinc electroplated steel sheet is immersed in the surface treatment agent (solid content 15 to 20 mass%, temperature 20 ° C.) of each example for 5 seconds, and the weight before and after the immersion of the plated steel sheet Changes were measured. The change in weight was converted to g / m ² and evaluated according to the following evaluation criteria.
○: Less than 0.1 g / m ² Δ: 0.1 g / m ² or more, less than 0.2 g / m ² ×: 0.2 g / m ² or more (2) Chemical stability at high pH A surface treatment agent (solid content: 15 to 20 mass%, temperature: 20 ° C.) was weighed in a beaker, and titrated with 1N NaOH while stirring the surface treatment agent, and the pH at the stage where precipitates were generated was measured. Measured and evaluated according to the following evaluation criteria.
○: pH 4 or more Δ: pH 3 or more and less than pH 4 ×: pH less than 3

(3) Plate conductivity A test piece having a size of 175 mm × 100 mm was cut out from the surface-treated steel sheet of each example, and a 4-terminal 4-deep needle type surface resistance meter (trade name “Mitsubishi Chemical Corporation” The average value of the surface resistance values measured at 10 points using “Loresta”) was evaluated according to the following evaluation criteria.
◎: Less than 0.1 mΩ ○: 0.1 mΩ or more, less than 0.5 mΩ △: 0.5 mΩ or more, less than 1.0 mΩ ×: 0.1 mΩ or more (4) Plane portion corrosion resistance 70 mm × from the surface-treated steel sheet of each example A test piece having a size of 150 mm was cut out, the end face of the test piece was sealed, and subjected to a salt spray test (JIS-Z-2371). The time required until white rust was generated in 5% of the surface area of each specimen was measured and evaluated according to the following evaluation criteria.
◎: 72 hours or more ○: 48 hours or more, less than 72 hours △: 24 hours or more, less than 48 hours ×: 24 hours or less

(5) Workability About the surface-treated steel sheet of each example, press forming was performed using the Eriksen cup tester under the following conditions, and the forming possibility (○: yes, x: not possible) and the forming load at that time were evaluated. .
<Processing conditions>
Punch diameter: 33mm
Blank diameter: 66mm
Drawing die shoulder curvature: 3mmR
Aperture speed: 60 mm / s
Wrinkle holding load: 1 ton
Quick dry oil coating (1.5 g / m ² )
Furthermore, as an evaluation of the appearance after processing, the ease of peeling of the surface treatment film after processing was evaluated. That is, after attaching “cellophane tape” (registered trademark) to the side wall portion of a molded product that has been press-molded using the Erichsen cup testing machine, it is peeled off and attached to a Cu plate. Zn count was measured by wire. Then, based on the count value, determination was performed based on the following criteria.
○: 10 kcps or less Δ: Over 10 kcps to 15 kcps
×: Over 15 kcps

(6) Corrosion resistance after processing The surface-treated steel sheet of each example was subjected to cylindrical molding under the above conditions, and then the end surface of the molded body was sealed and subjected to a salt spray test (JIS-Z-2371). The time required for white rust to occur in 5% of the surface area of each molded body was evaluated according to the following evaluation criteria.
◎: 12 hours or more ○: 6 hours or more, less than 12 hours △: 3 hours or more, less than 6 hours ×: 3 hours or less

The above test results are shown in Tables 1 to 4 together with the composition of the surface treatment agent and the structure of the surface treatment film.
As shown in Tables 1 to 4, all of the examples of the present invention are excellent in the zinc dissolution inhibiting property and chemical stability of the surface treatment agent, and the plated steel sheet on which the surface treatment film is formed by this surface treatment agent, It has excellent conductivity, corrosion resistance (flat portion corrosion resistance and post-processing corrosion resistance), and workability.

The graph which shows an example of the component analysis result of the surface treatment film | membrane thickness direction by GDS about the surface treatment zinc-plated steel plate of this invention

Claims (5)

A zinc-based plated steel material comprising an aqueous solution containing the following components (a) to (d), having a pH of 1 to 4 and a free acidity of 3 to 20 in terms of 0.1 N sodium hydroxide: Surface treatment agent.
(A) One or more metal ions selected from Al, Mn, Mg, V, and Zn (b) Phosphoric acid: 300 to 1500 masses per 100 mass parts (solid content) of the metal ions in (a) above Parts (solid content)
(C) Organic resin: 5 to 100 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the metal ions of (a) above
(D) One or more selected from N-methyliminodiacetic acid, iminodiacetic acid, 1,2-diaminocyclohexane, arginine, and proline : 10 to 300 with respect to 100 parts by mass (solid content) of the metal ion of (a). Part by mass (solid content)   The surface treating agent for galvanized steel material according to claim 1, wherein at least a part of the organic resin is a water-dispersible resin.   The surface treatment agent for galvanized steel according to claim 1 or 2, further comprising a solid lubricant.   It has the surface treatment film formed by apply | coating the surface treating agent in any one of Claims 1-3 to the surface of a zinc-plated steel plate, and drying, and this surface treatment film is in contact with a plating layer. And a reaction product (i) of a phosphate ion and a plating metal, and a metal salt (ii) containing at least one metal selected from Al, Mn, Mg, V, and Zn, and organic A surface-treated galvanized steel sheet having a lower layer portion having a thickness of 0.02 to 3 μm containing the resin (iii). The surface of the galvanized steel sheet is applied by applying the surface treatment agent according to any one of claims 1 to 3 so that the solid content is 0.05 to 3.0 g / m ² and drying. A method for producing a surface-treated galvanized steel sheet, comprising forming a treated film.

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