Chemical conversion treatment agent, surface-treated metal, and surface treatment method

Abstract

Provided is a chemical conversion treatment agent capable of performing a chemical conversion treatment with which excellent corrosion resistance can be obtained after coating. The chemical conversion treatment agent contains (A) at least one metal component selected from the group consisting of zirconium, titanium, and hafnium, (B) fluorine, and (C) a water-soluble resin. The content of the metal component (A) is 10-10000 ppm by mass in terms of metal elements with respect to the total mass of the chemical conversion treatment agent, and the water-soluble resin (C) is a copolymer containing a segment derived from diallylamine and a segment derived from a (meth) acrylic monomer having a primary amino group.

Description

Technical Field

[0001] The present invention relates to a chemical conversion treatment agent, a surface-treated metal, and a surface treatment method. Background Art

[0002] Conventionally, in the case of applying cationic electrodeposition coating or powder coating to the surface of a metal substrate, in order to improve corrosion resistance, film adhesion, etc., the surface of the metal substrate is previously subjected to chemical conversion treatment. In recent years, chemical conversion treatment using zinc phosphate not containing chromium has been widely carried out.

[0003] In the chemical conversion treatment using zinc phosphate, it is difficult to perform drainage treatment due to the high reactivity of the treatment agent, and there are problems of generating sludge and a large environmental load. Therefore, a chemical conversion treatment agent composed of at least one selected from the group consisting of zirconium, titanium, and hafnium, fluorine, and a water-soluble resin has been proposed (for example, refer to Patent Document 1).

[0004] The technology disclosed in Patent Document 1 can perform good chemical conversion treatment on metals such as iron, zinc, and aluminum. However, there is still room for improvement in terms of corrosion resistance obtained after coating such as cationic electrodeposition coating and powder coating. Therefore, a chemical conversion treatment agent with improved corrosion resistance has been proposed (refer to Patent Document 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-218074

[0008] Patent Document 2: Japanese Patent No. 7052137 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] Regarding the technology disclosed in Patent Document 2, further improvement in corrosion resistance is required.

[0011] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a chemical conversion treatment agent capable of performing chemical conversion treatment that can obtain excellent corrosion resistance after coating.

[0012] Means for Solving the Problems

[0013] (1) The present invention relates to a chemical conversion treatment agent, which contains at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium, fluorine (B), and a water-soluble resin (C). The content of the above metal component (A) is 10 to 10,000 mass ppm in terms of metal element based on the total mass of the chemical conversion treatment agent. The above water-soluble resin (C) is a copolymer containing a segment derived from diallylamine and a segment derived from a (meth)acrylic acid monomer having a primary amino group.

[0014] (2) The chemical conversion treatment agent according to (1), wherein the content ratio of the segment derived from the above diallylamine in the above water-soluble resin (C) is 25 mol% or more and 98 mol% or less based on the total of the segment derived from the above diallylamine and the segment derived from the above (meth)acrylic acid monomer having a primary amino group.

[0015] (3) The chemical conversion treatment agent according to (1) or (2), wherein the (meth)acrylic acid monomer having a primary amino group is acrylamide.

[0016] (4) The chemical conversion treatment agent according to any one of (1) to (3), wherein the weight-average molecular weight of the above water-soluble resin (C) is 500 to 500,000.

[0017] (5) The chemical conversion treatment agent according to any one of (1) to (4), wherein the content of the above water-soluble resin (C) is 25 to 5,000 mass ppm in terms of solid content concentration based on the total mass of the chemical conversion treatment agent.

[0018] (6) The chemical conversion treatment agent according to any one of (1) to (5), wherein the above water-soluble resin (C) is an acid addition salt having an anionic counterion, and the pKa of the acid forming the above acid addition salt is in the range of -3.7 to 4.8.

[0019] (7) The chemical conversion treatment agent according to any one of (1) to (6), which further contains at least one metal component selected from the group consisting of aluminum and zinc.

[0020] (8) The chemical conversion treatment agent according to any one of (1) to (7), which further contains a silane coupling agent.

[0021] (9) A surface-treated metal having a chemical conversion film formed by curing the chemical conversion treatment agent according to any one of (1) to (8) on its surface.

[0022] (10) The surface-treated metal according to (9), wherein the content of the above metal component (A) in the above chemical conversion film is 5 to 500 mg / m 2 .

[0023] (11) A surface treatment method having a chemical conversion film formation step, wherein the chemical conversion film formation step forms a chemical conversion film by treating the surface of an object to be coated with the chemical conversion treatment agent according to any one of (1) to (8).

[0024] (12) The surface treatment method according to (11), further comprising an electrodeposition coating film formation step of forming an electrodeposition coating film by subjecting the object to be coated having the chemical conversion film formed thereon to electrodeposition coating.

[0025] Advantages of the Invention

[0026] According to the present invention, a chemical conversion treatment agent capable of performing chemical conversion treatment that can provide excellent corrosion resistance after coating can be provided. Detailed Embodiments

[0027] Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the descriptions of the following embodiments.

[0028] <Chemical Conversion Treatment Agent>

[0029] The chemical conversion treatment agent of the present embodiment can form a chemical conversion film on the surface of a metal substrate that can provide excellent corrosion resistance after coating. The metal substrate on which the chemical conversion film is formed and coated is not particularly limited, and can be used for various purposes such as automobile bodies and automobile parts, for example. Examples of the above coating include cationic electrodeposition coating, powder coating, water-based coating, solvent coating, and the like.

[0030] The chemical conversion treatment agent of the present embodiment contains at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium, fluorine (B), and a water-soluble resin (C).

[0031] (Metal Component (A))

[0032] The metal component (A) is a chemical conversion film formation component. By forming a chemical conversion film containing at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium on a metal substrate, the corrosion resistance and wear resistance of the metal substrate can be improved, and the adhesion to coating films such as electrodeposition coating films can be improved.

[0033] As the supply source of the above zirconium, there is no particular limitation, and examples thereof include alkali metal fluozirconates such as K2ZrF6, fluoziric acid (H2ZrF6), ammonium hexafluorozirconate ((NH4)2ZrF6), ammonium zirconium carbonate ((NH4)2ZrO(CO3)2), tetraalkylammonium-modified zirconium, zirconium fluoride, zirconium oxide, and the like.

[0034] The supply source of the above-mentioned titanium is not particularly limited. For example, alkali metal fluotitanates, fluotitanates such as (NH4)2TiF6, soluble fluotitanates such as H2TiF6, titanium fluoride, titanium oxide, etc. can be cited.

[0035] The supply source of the above-mentioned hafnium is not particularly limited. For example, hafnium fluoride acids such as H2HfF6, hafnium fluoride, etc. can be cited.

[0036] The content of the above-mentioned metal component (A) is 10 to 10,000 mass ppm in terms of metal element based on the total mass of the chemical conversion treatment agent. When the content of the metal component (A) is less than 10 ppm, sufficient performance of the obtained chemical conversion film cannot be obtained. When the content of the metal component (A) exceeds 10,000 mass ppm, no further effects can be obtained, which is economically disadvantageous. From the above viewpoints, the content of the above-mentioned metal component (A) is preferably 50 to 2,000 mass ppm in terms of metal element, and more preferably 50 to 800 mass ppm.

[0037] (Fluorine (B))

[0038] Fluorine (B) has the function of etching the surface of the metal substrate. The supply source of the above-mentioned fluorine is not particularly limited. For example, fluorides such as hydrofluoric acid, ammonium fluoride, fluoboric acid, ammonium bifluoride, sodium fluoride, sodium hydrogen fluoride, etc. can be cited. In addition, as complex fluorides, for example, hexafluorosilicates can be cited. As specific examples, fluorosilicic acid, zinc fluorosilicate, manganese fluorosilicate, magnesium fluorosilicate, nickel fluorosilicate, iron fluorosilicate, calcium fluorosilicate, etc. can be cited. In addition, fluorine-containing compounds such as alkali metal fluozirconates exemplified as the supply source of the above-mentioned metal component (A) are the supply source of the metal component (A) and can also be the supply source of fluorine (B).

[0039] The concentration of fluorine (B) is preferably 10 to 12,500 mass ppm in terms of fluorine element based on the total mass of the chemical conversion treatment agent. When the concentration of fluorine (B) is lower than 10 mass ppm, etching becomes insufficient and a good chemical conversion film cannot be obtained. When it exceeds 12,500 mass ppm, etching is excessive and a chemical conversion film cannot be formed sufficiently. From the above viewpoints, the concentration of fluorine (B) is more preferably 62.5 to 2,500 mass ppm. As a method for measuring the concentration of fluorine (B), for example, a method of quantitative analysis by ion chromatography can be cited.

[0040] (Water-soluble resin (C))

[0041] The water-soluble resin (C) is a copolymer containing a segment derived from diallylamine and a segment derived from a (meth)acrylic monomer having a primary amino group (hereinafter sometimes referred to as "diallylamine segment" and "amino acrylic segment"). The diallylamine segment may be in the form of a quaternary ammonium compound. In addition, each of the above segments may independently have a counter ion.

[0042] In the water-soluble resin (C) in the present embodiment, the content ratio of the diallylamine segment is preferably 25 mol% or more and 98 mol% or less relative to the total of the diallylamine segment and the amino acrylic segment. By making the content ratio of the above diallylamine segment 25 mol% or more, the adhesion to the electrodeposited coating film becomes good and the corrosion resistance is improved. By making the content ratio of the above diallylamine segment 98 mol% or less, the corrosion resistance in the SDT test is improved. From the above viewpoints, the content ratio of the diallylamine segment is more preferably 50 mol% or more and 98 mol% or less, and most preferably 80 mol% or more and 98 mol% or less.

[0043] As the above diallylamine segment, for example, the heterocyclic structures represented by the following general formulas (1a) and (1b) can be cited. The above heterocyclic structure may be a saturated heterocyclic structure.

[0044] [Chemical formula 1]

[0045]

[0046] (In the above formula, R 1 represents a hydrogen atom, an alkyl group or an aralkyl group.)

[0047] By including an amino acrylic segment composed of a (meth)acrylic monomer having a primary amino group in the water-soluble resin (C), the adsorption of the chemical conversion film to the substrate surface is improved. As the (meth)acrylic monomer having a primary amino group, for example, acrylamide, methacrylamide, (meth)acrylic acid amino methyl ester, (meth)acrylic acid amino ethyl ester, (meth)acrylic acid amino propyl ester, (meth)acrylic acid amino butyl ester, (meth)acrylic acid amino pentyl ester, (meth)acrylic acid amino hexyl ester, etc. can be cited.

[0048] The water-soluble resin (C) is preferably an acid addition salt having an anionic counter ion with respect to the ammonium cation. The dissociation constant pKa of the acid forming the above acid addition salt is preferably in the range of -3.7 to 4.8. It should be noted that in this specification, the dissociation constant pKa of the above acid refers to the value at a solvent of water and a temperature of 25 °C. As the diallylamine segment constituting the above acid addition salt, that is, the water-soluble resin (C), for example, it is represented by the following general formulas (1c) and (1d).

[0049] [Chemical formula 2]

[0050]

[0051] (In the formula, R 2 and R 3 represent a hydrogen atom, an alkyl group or an aralkyl group, and D - represents a monovalent anion.)

[0052] There is no particular limitation on the above anionic counter ion. For example, it is a monovalent anion, and examples thereof include carboxylate ions such as formate ion, acetate ion, benzoate ion, chloride ion, sulfate ion, nitrate ion, etc. Examples of the acid for forming an acid addition salt include organic acids such as formic acid, acetic acid, benzoic acid, and inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid.

[0053] The water-soluble resin (C) may have a segment other than the diallylamine segment and the aminoacrylate segment as needed. For example, segments derived from N,N-dialkylaminoalkyl (meth)acrylate and its salts or quaternary ammonium compounds, N,N-dialkylaminoalkyl (meth)acrylamide and its salts or quaternary ammonium compounds, vinylimidazole and its salts or quaternary ammonium compounds, vinylpyridine and its salts or quaternary ammonium compounds, N-alkylallylamine and its salts, N,N-dialkylallylamine and its salts, etc. can be cited.

[0054] The water-soluble resin (C) may further have a segment other than the above as needed. For example, it may have segments from sulfur dioxide, unsaturated compounds having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid alkyl esters such as (meth)methyl acrylate and (meth)ethyl acrylate, vinyl acetate, vinyl propionate and other vinyl carboxylates, unsaturated acids, etc.

[0055] The content ratio of the segments other than the diallylamine segment and the aminoacrylate segment in the water-soluble resin (C) is preferably 20% or less, more preferably 10% or less, and most preferably 0%. The content ratio of the segments other than the diallylamine segment and the aminoacrylate segment is defined as the mole% of the segments that do not belong to either the diallylamine segment or the aminoacrylate segment in the water-soluble resin (C) relative to the total of all segments.

[0056] The content of the water-soluble resin (C) is preferably 25 to 5000 mass ppm in terms of the resin solid content concentration relative to the total mass of the chemical conversion treatment agent. When the content is less than 25 mass ppm, sufficient adhesion of the chemical conversion film cannot be obtained. When it exceeds 5000 mass ppm, the formation of the chemical conversion film may be hindered. From the above viewpoints, the content of the water-soluble resin (C) is more preferably 50 to 2500 mass ppm and further preferably 50 to 600 mass ppm in terms of the resin solid content concentration.

[0057] The weight-average molecular weight of the water-soluble resin (C) is preferably from 500 to 500,000. When the weight-average molecular weight is less than 500, sufficient adhesion of the chemical conversion film cannot be obtained. When the weight-average molecular weight exceeds 500,000, formation of the chemical conversion film may be hindered. From the above viewpoints, the weight-average molecular weight of the water-soluble resin (C) is preferably from 5,000 to 100,000.

[0058] The weight-average molecular weight of the water-soluble resin (C) can be measured, for example, by gel permeation chromatography (GPC). As the measuring equipment, for example, Hitachi L-6000 type high performance liquid chromatograph can be used. As the eluent flow path pump, Hitachi L-6000 can be used, and as the detector, Shodex RISE-61 differential refractive index detector can be used. As the chromatographic column, a chromatographic column formed by double-connecting Asahipak's aqueous gel filtration type GS-220HQ (exclusion limit molecular weight 3,000) and GS-620HQ (exclusion limit molecular weight 2 million) can be used. An example of the GPC measuring method is shown below. The sample is adjusted to a concentration of 0.5 g / 100 ml with the eluent, and 20 μl is used. As the eluent, 0.4 mol / L aqueous sodium chloride solution is used. The column temperature is 30°C and the flow rate is 1.0 ml / minute. As the standard sample, polyethylene glycols with molecular weights of 106, 194, 440, 600, 1470, 4100, 7100, 10300, 12600, 23000, etc. are used to obtain the calibration curve. The weight-average molecular weight (Mw) of the copolymer is obtained based on the above calibration curve.

[0059] The water-soluble resin (C) can be modified within the range that does not impair the object of the present invention. For example, a part of the amino groups of the water-soluble resin (C) can be modified by methods such as acetylation, or it can be crosslinked with a crosslinking agent to an extent that does not affect solubility.

[0060] The method for preparing the water-soluble resin (C) is not particularly limited. For example, there can be mentioned a method in which a monomer mixture obtained by mixing diallylamine, a (meth)acrylic acid monomer having a primary amino group, and other components as required is subjected to radical polymerization in a suitable solvent in the presence of a radical polymerization initiator. Regarding the polymerization conditions, conditions well-known to those skilled in the art can be appropriately selected.

[0061] (Other polymers)

[0062] The chemical conversion treatment agent of the present embodiment may contain polymers other than the water-soluble resin (C). Examples of the polymers other than the water-soluble resin (C) include polymer components such as polyallylamine resin, polyvinylamine resin, polydiallylamine resin, urethane resin, acrylic resin, polyester resin, chitin-chitosan derivatives, and natural polymer derivatives such as cellulose derivatives. When the chemical conversion treatment agent of the present embodiment contains polymers other than the water-soluble resin (C), the solid component mass of the water-soluble resin (C) is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more, based on the total mass of the solid components of all the polymers.

[0063] (Other components)

[0064] The chemical conversion treatment agent of the present embodiment preferably further contains a silane coupling agent. By including a silane coupling agent in the chemical conversion treatment agent, the film adhesion of the chemical conversion film can be further improved. The silane coupling agent is not particularly limited. For example, it is preferably one or more silane coupling agents selected from the group consisting of amino group-containing silane coupling agents, epoxy group-containing silane coupling agents, hydrolyzates of amino group-containing silane coupling agents, hydrolyzates of epoxy group-containing silane coupling agents, polymers of amino group-containing silane coupling agents, and polymers of epoxy group-containing silane coupling agents.

[0065] Examples of the above-mentioned amino group-containing silane coupling agents are not particularly limited. For example, N-2(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)-3-aminopropyltrimethoxysilane, N-2(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N,N-bis〔3-(trimethoxysilyl)propyl〕ethylenediamine, and other known silane coupling agents can be cited. Commercially available amino group-containing silane coupling agents such as KBM-602, KBM-603, KBE-603, KBM-903, KBE-9103, KBM-573 (manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used.

[0066] The hydrolyzate of the above-mentioned amino group-containing silane coupling agent can be produced by a conventionally known method, for example, a method of dissolving the above-mentioned amino group-containing silane coupling agent in ion-exchanged water and adjusting it to an acidic state with an arbitrary acid. As the hydrolyzate of the above-mentioned amino group-containing silane coupling agent, commercially available products such as KBP-90 (manufactured by Shin-Etsu Chemical Co., Ltd.: active ingredient 32%) can also be used.

[0067] The above epoxy group-containing silane coupling agent is not particularly limited. For example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethylethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 5,6-epoxyhexyltriethoxysilane, etc. can be cited. Commercially available products such as "KBM-403", "KBE-403", "KBE-402", "KBM-303" (manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used.

[0068] The chemical conversion treatment agent of the present embodiment may contain components other than the above. For example, as a chemical conversion film forming component, it is preferably further contained at least one metal component selected from the group consisting of aluminum and zinc. Thereby, the corrosion resistance of the metal substrate formed with the chemical conversion film can be further improved. As a chemical conversion film forming component, in addition to the above, it may also contain at least one metal component selected from the group consisting of magnesium, calcium, gallium, indium, and copper. In addition, metal components of manganese, iron, cobalt, nickel, and chromium may also be contained. The supply source of the above film forming component is not particularly limited, and oxides, hydroxides, fluorides, chlorides, sulfates, nitrates, borates, carbonates, organic acid salts, etc. of each metal can be cited. The metal components of the above film forming component may be contained in the chemical conversion treatment agent as eluted components from the metal substrate to be chemically converted in the chemical conversion treatment bath.

[0069] The chemical conversion treatment agent of the present embodiment may contain an oxidizing agent. For example, as a chemical conversion film forming component, it is preferably further contained at least one oxidizing agent selected from the group consisting of nitric acid and nitrous acid. Thereby, the formation of the chemical conversion film can be promoted, and the corrosion resistance of the metal substrate can be further improved. Inorganic acids or their salts as oxidizing agents are considered to promote the formation reaction of the chemical conversion film as oxidizing agents. As inorganic acids, nitric acid, nitrous acid, hydrochloric acid, bromic acid, chloric acid, hydrogen peroxide, HMnO4, and HVO3, etc. can be cited. It should be noted that in the metal surface treatment composition, as an oxidizing agent, a compound containing a sulfonic acid group or its salt may be contained. It should be noted that in the metal surface treatment composition, as an oxidizing agent, a compound containing a sulfonic acid group or its salt may be contained. It should be noted that in the chemical conversion treatment agent, as an oxidizing agent, a compound containing a sulfonic acid group or its salt may be contained.

[0070] The chemical conversion treatment agent of the present embodiment preferably contains substantially no phosphate ions. In this specification, containing substantially no phosphate ions means that the phosphate ions are contained to such an extent that they do not function as components in the chemical conversion treatment agent. Since the chemical conversion treatment agent of the present embodiment contains substantially no phosphate ions, phosphorus, which is a cause of environmental load, is substantially not used. In addition, generation of sludge such as iron phosphate and zinc phosphate generated when using a zinc phosphate treatment agent can be suppressed.

[0071] (pH)

[0072] The pH of the above chemical conversion treatment agent is preferably 2.0 to 6.0. When the pH is less than 2.0, etching becomes excessive and a chemical conversion film cannot be sufficiently formed. When the pH exceeds 6.0, etching becomes insufficient and a good chemical conversion film cannot be obtained. From the above viewpoints, the pH is more preferably 2.0 to 5.5, and further preferably 3.0 to 4.5. In order to adjust the pH of the above chemical conversion treatment agent, acidic compounds such as nitric acid and sulfuric acid, and basic compounds such as sodium hydroxide, potassium hydroxide, and ammonia can be used.

[0073] <Surface-treated metal>

[0074] The surface-treated metal has a chemical conversion film formed by curing the chemical conversion treatment agent of the present embodiment on the surface of the metal substrate as the object to be coated. The surface-treated metal of the present embodiment not only has excellent adhesion and corrosion resistance between the chemical conversion film and the metal substrate, but also has excellent adhesion and corrosion resistance between the coating film and the chemical conversion film when a coating film such as an electrodeposited coating film is further formed on the chemical conversion film. The above metal substrate is not particularly limited, and examples thereof include iron-based substrates, aluminum-based substrates, and zinc-based substrates. Here, the iron-based substrate, aluminum-based substrate, and zinc-based substrate respectively refer to an iron-based substrate in which the substrate is composed of iron and / or its alloy, an aluminum substrate in which the substrate is composed of aluminum and / or its alloy, and a zinc-based substrate in which the substrate is composed of zinc and / or its alloy. The metal substrate may also be composed of a plurality of metal substrates among the iron-based substrate, aluminum-based substrate, and zinc-based substrate.

[0075] The chemical conversion treatment agent of the present embodiment can impart sufficient coating film adhesion even to an iron-based substrate that has difficulty in having sufficient coating film adhesion in a conventional chemical conversion treatment agent. The above iron-based substrate is not particularly limited, and examples thereof include cold-rolled steel sheets, hot-rolled steel sheets, mild steel sheets, and high-tensile steel sheets. The chemical conversion treatment agent of the present embodiment can impart excellent corrosion resistance and adhesion to both high-tensile steel sheets having a thick oxide film and cold-rolled steel sheets having a thin oxide film.

[0076] As the above-mentioned aluminum-based substrate, there is no particular limitation. For example, 5000 series aluminum alloy, 6000 series aluminum alloy, etc. can be cited. As the above-mentioned zinc-based substrate, there is no particular limitation. For example, zinc or zinc-based alloy coated steel plates such as electroplated, hot-dip plated, and vapor-deposited zinc-coated steel plates including galvanized steel plates, zinc-nickel plated steel plates, zinc-iron plated steel plates, zinc-chromium plated steel plates, zinc-aluminum plated steel plates, zinc-titanium plated steel plates, zinc-magnesium plated steel plates, and zinc-manganese plated steel plates can be cited.

[0077] In the chemical conversion film formed by the chemical conversion treatment agent of the surface-treated metal of the present embodiment, the content of the metal component (A) is preferably 5 to 500 mg / m 2 . When the above content of the metal component (A) is less than 5 mg / m 2 , a uniform chemical conversion film cannot be obtained. When the above content of the metal component (A) exceeds 500 mg / m 2 , no further effect can be obtained, which is economically disadvantageous. The content of the above metal component (A) is more preferably 5 to 200 mg / m 2 . In addition, in the chemical conversion film formed by the chemical conversion treatment agent, the ratio of the carbon content to the content of the metal component (A), that is, C / A, is preferably 10 to 27%.

[0078] <Surface treatment method>

[0079] The surface treatment method for surface-treating a metal substrate using the chemical conversion treatment agent of the present embodiment may include a chemical conversion film forming step and an electrodeposited coating film forming step.

[0080] (Chemical conversion film forming step)

[0081] The chemical conversion film forming step is a step of forming a chemical conversion film on the surface of the above metal substrate to produce a surface-treated metal. The chemical conversion film forming step is carried out by bringing the above chemical conversion treatment agent into contact with the surface of the metal substrate. As the method of the above contact, there is no particular limitation. For example, dipping method, spraying method, roll coating method, etc. can be cited. The treatment temperature in the above chemical conversion film forming step can be set within the range of 15 to 70 °C, preferably within the range of 15 to 50 °C, and more preferably within the range of 30 to 50 °C. The treatment time in the above chemical conversion film forming step can be set within the range of 5 to 1200 seconds, preferably within the range of 30 to 120 seconds.

[0082] (Electrodeposited coating film forming step)

[0083] The electrodeposition coating film forming process is a process of subjecting the surface-treated metal produced by the above chemical conversion film forming process to electrodeposition coating to form an electrodeposition coating film on the surface. The electrodeposition coating is not particularly limited. For example, it can be cationic electrodeposition coating. The cationic electrodeposition coating used for cationic electrodeposition coating is not particularly limited, and conventionally known cationic electrodeposition coatings composed of, for example, aminated epoxy resins, aminated acrylic resins, sulfonium epoxy resins, etc. can be used. The electrodeposition coating method using the above electrodeposition coating is not particularly limited, and known electrodeposition coating methods can be applied.

[0084] (Other processes)

[0085] The surface treatment method of the present embodiment may have a degreasing treatment process and a post-degreasing water washing treatment process before the above chemical conversion film forming process. In addition, a post-chemical conversion water washing treatment process may be provided after the above chemical conversion film forming process and before the electrodeposition coating film forming process.

[0086] The degreasing treatment process is carried out by immersion treatment for about several minutes at, for example, 30 to 55 °C using a degreasing agent such as a phosphorus-free and nitrogen-free degreasing cleaning solution. Pre-degreasing treatment may also be carried out before the degreasing treatment process.

[0087] The post-degreasing water washing treatment process is a process of washing the degreasing agent after the degreasing treatment, and is carried out by one or more spray treatments using a large amount of washing water.

[0088] The post-chemical conversion water washing treatment process is carried out by one or more spray treatments or immersion water washing within a range that does not affect the adhesion and corrosion resistance after coating, etc. The final above water washing treatment is preferably carried out with ion-exchanged water or pure water. After the post-chemical conversion water washing treatment process, a process for drying the surface-treated metal may be provided as needed.

[0089] In the above embodiment, it was described that the surface treatment method for surface-treating a metal substrate includes an electrodeposition coating film forming process. The surface treatment method of the present invention may also include a process of performing any one of powder coating, water-based coating, and solvent coating on an object to be coated having a chemical conversion film instead of the electrodeposition coating film forming process. The processes for performing powder coating, water-based coating, and solvent coating are not particularly limited, and conventionally known methods can be used. The chemical conversion treatment agent of the present embodiment can impart the same corrosion resistance as that imparted to the electrodeposition coating film even to the coating films formed by powder coating, water-based coating, and solvent coating.

[0090] Examples

[0091] Hereinafter, the content of the present invention will be described in more detail based on examples. The content of the present invention is not limited to the description of the following examples.

[0092] (Example 1)

[0093] A commercially available cold-rolled steel sheet (SPCC-SD, manufactured by Nippon Testpanel Co., Ltd., 70 mm × 150 mm × 0.8 mm) was used as the metal substrate, and surface treatment was carried out under the following conditions.

[0094] As the degreasing treatment process, it was immersed in 2% by mass of "Surfcleaner 53" (a degreasing agent manufactured by Nippon Paint Surf Chemicals Co., Ltd.) at 40°C for 2 minutes. As the post-degreasing water washing treatment process, it was spray-treated with tap water for 30 seconds. As the chemical conversion treatment process, zirconium fluoride, a water-soluble resin (diallylamine segment: 97 mol%, amino acrylic acid segment: 3 mol%, molecular weight 20,000, hydrochloride (pKa - 3.7) salt), and zinc nitrate hexahydrate (Zn(NO3)2·6H2O) were used. As shown in Table 1, a chemical conversion treatment agent was prepared such that the content of Zr in terms of metal element was 400 ppm by mass, the fluorine concentration was 500 ppm by mass, the content of the water-soluble resin in terms of resin solid content concentration was 100 ppm by mass, and the content of Zn was 500 ppm by mass. The pH was adjusted to 4.2 using sodium hydroxide. The temperature of the chemical conversion treatment agent was adjusted to 40°C, and the metal substrate was immersed for 120 seconds.

[0095] As the post-chemical conversion water washing treatment process, it was spray-treated with tap water for 30 seconds. Further, it was spray-treated with ion-exchanged water for 30 seconds. Then, as the drying treatment, it was dried in an electric drying furnace at 80°C for 5 minutes. Using "ZSXPrimusII" (an X-ray analysis device manufactured by Rigaku Corporation), the content of Zr as the metal component (A) in the chemical conversion treatment film (mg / m 2 ) and the C content from the water-soluble resin (mg / m 2 ) were measured and are shown in Table 3.

[0096] As the electrodeposition coating film forming process, "Powernix 310" (a cationic electrodeposition coating manufactured by Nippon Paint Automotive Coatings Co., Ltd.) was used for electrodeposition coating such that the dry film thickness became 20 μm. After water washing, it was sintered by heating at 170°C for 20 minutes to produce a test panel for Example 1. The "Zr film amount" in Table 3 represents the content of zirconium as the metal component (A) in the chemical conversion film, and the "C film amount" represents the content of carbon in the chemical conversion film.

[0097] (Examples 2 to 19, Comparative Examples 1 to 7)

[0098] Except that the composition and temperature of the chemical conversion treatment agent in the chemical conversion treatment process are the compositions and temperatures shown in Tables 1 and 2, and the metal substrate is the metal substrate shown in Table 3, test plates of the above-mentioned examples and comparative examples were produced in the same manner as in Example 1. Aluminum nitrate nonahydrate was used as the aluminum component, and a chemical conversion treatment agent was prepared such that the content of Al became the concentration shown in Table 2. It should be noted that the concentration (mass ppm) of each component shown in Tables 1 and 2 refers to the concentration relative to the total mass of the chemical conversion treatment agent. The "polymerization ratio" shown in Table 1 refers to the segment ratio (molar ratio) when the water-soluble resin (C) or the resin is a copolymer. The details of the symbols (abbreviations) shown in Tables 1 to 3 are as follows.

[0099] (Resin)

[0100] DA-Aam: Diallylamine-acrylamide copolymer

[0101] DA-AM: Diallylamine-allylamine copolymer

[0102] DA: Diallylamine polymer

[0103] Aam: Acrylamide polymer

[0104] AM: Allylamine polymer

[0105] (Additive component)

[0106] KBM603: N-2-(Aminoethyl)-3-aminopropyltrimethoxysilane (KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0107] Mn: Manganese(II) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Corporation)

[0108] Ca: Calcium(II) nitrate tetrahydrate (manufactured by Kanto Chemical Co., Inc. / Deer Grade 1)

[0109] Cu: Copper(II) nitrate trihydrate (manufactured by Fujifilm Wako Pure Chemical Corporation)

[0110] (Substrate)

[0111] SPC: Cold-rolled steel sheet (SPCC-SD, manufactured by Japan Testpanel Corporation, 70 mm × 150 mm × 0.8 mm)

[0112] GA: Alloy hot-dip galvanized steel sheet (SCGA270D, manufactured by Japan Testpanel Corporation, 70 mm × 150 mm × 0.8 mm)

[0113] Al: Aluminum alloy (6K21, manufactured by Kobe Steel, Ltd., 70 mm × 150 mm × 0.8 mm)

[0114] It should be noted that the pKa of acetic acid, which is the acid forming the water-soluble resin, i.e., the acid addition salt, in Example 13 is 4.8. In Comparative Example 7, DA and Aam were mixed and used at respective concentrations of DA: 97 mass ppm and Aam: 3 mass ppm.

[0115] [Secondary adhesion test (SDT)]

[0116] For the test plates of the examples and comparative examples, after applying two longitudinal parallel cuts reaching the substrate, they were immersed in a 5 mass% NaCl aqueous solution at 55 °C for 240 hours. Then, the test plates were washed with tap water and further dried at room temperature. Then, a tape peeling test was performed on the cut portion of the cross-cut of the electrodeposited coating film using Cellotape (registered trademark), and the maximum peeling width on one side from the cross-cut was measured. Evaluation was carried out according to the following criteria, and a value of 2 or more was considered qualified. The results are shown in Table 3.

[0117] 3: Peeling is less than 1.0 mm

[0118] 2: Peeling is 1.0 mm or more and less than 2.5 mm

[0119] 1: Peeling is 2.5 mm or more

[0120] [Total area of general surface blistering (SDT blistering) after salt warm water test (SDT)]

[0121] The test plates of the examples and comparative examples were immersed in a 5 mass% NaCl aqueous solution at 55 °C for 240 hours. Then, the test plates were washed with tap water and further dried at room temperature. Then, the total area ratio of the blisters generated on the general surface of the electrodeposited coating film was measured. The above general surface refers to the area excluding the portion from the end to 5 mm. Evaluation was carried out according to the following criteria, and a value of 2 or more was considered qualified. The results are shown in Table 3.

[0122] 3: Total area ratio of blisters is 0%

[0123] 2: Total area ratio of blisters exceeds 0% and is less than 1.0%

[0124] 1: Total area ratio of blisters is 1.0% or more

[0125] [Composite cyclic corrosion test (CCT)]

[0126] After applying cross-cutting to the test panels of the examples and comparative examples to reach the substrate, a combined cyclic corrosion test was conducted. The test method was carried out according to the provisions of JASO M609-91 for 100 cycles of combined tests. After the test, the maximum expansion width on both sides starting from the cut part was measured. Evaluation was made based on the following criteria, and a value of 4 or more was considered qualified. The results are shown in Table 3.

[0127] 5: Less than 3.5 mm

[0128] 4: 3.5 mm or more and less than 4.5 mm

[0129] 3: 4.5 mm or more and less than 6.0 mm

[0130] 2: 6.0 mm or more and less than 7.5 mm

[0131] 1: 7.5 mm or more

[0132] [Table 1]

[0133]

[0134] [Table 2]

[0135]

[0136] [Table 3]

[0137]

[0138] From the results of Tables 1 to 3, it can be confirmed that the chemical conversion treatment agent of each example can provide excellent corrosion resistance after painting compared with the chemical conversion treatment agent of the comparative example.

Claims

1. A chemical conversion treatment agent comprising at least one metal component (A) selected from the group consisting of zirconium, titanium, and hafnium, fluorine (B), and a water-soluble resin (C). The content of the metal component (A) is 10 to 10,000 mass ppm in terms of metal element relative to the total mass of the chemical conversion treatment agent. The water-soluble resin (C) is a copolymer containing a segment derived from diallylamine and a segment derived from a (meth)acrylic monomer having a primary amino group.

2. The chemical conversion treatment agent according to claim 1, wherein, The content ratio of the segment derived from diallylamine in the water-soluble resin (C) is 25 mol% or more and 98 mol% or less relative to the total of the segment derived from diallylamine and the segment derived from the (meth)acrylic monomer having a primary amino group.

3. The chemical conversion treating agent according to claim 1 or 2, wherein, The (meth)acrylic monomer having a primary amino group is acrylamide.

4. The chemical conversion treating agent according to claim 1 or 2, wherein, The weight-average molecular weight of the water-soluble resin (C) is 500 to 500,000.

5. The chemical conversion treating agent according to claim 1 or 2, wherein The content of the water-soluble resin (C) is 25 to 5,000 mass ppm in terms of solid content concentration relative to the total mass of the chemical conversion treatment agent.

6. The chemical conversion treatment agent according to claim 1 or 2, wherein The water-soluble resin (C) is an acid addition salt having an anionic counterion. The pKa of the acid forming the acid addition salt is in the range of -3.7 to 4.

8.

7. The chemical conversion treatment agent according to claim 1 or 2, further comprising at least one metal component selected from the group consisting of aluminum and zinc.

8. The chemical conversion treatment agent according to claim 1 or 2, further comprising a silane coupling agent.

9. A surface-treated metal having a chemical conversion film formed by curing the chemical conversion treatment agent according to claim 1 or 2 on the surface.

10. The surface-treated metal according to claim 9, wherein, The content of the metal component (A) in the chemical conversion coating is 5 to 500 mg / m in terms of metal element conversion 2 .

11. A surface treatment method having a chemical conversion film forming step. The chemical conversion film forming step is to form a chemical conversion film by treating the surface of an object to be coated with the chemical conversion treatment agent according to claim 1 or 2.

12. The surface treatment method according to claim 11, further including an electrodeposition coating film forming step of forming an electrodeposition coating film by subjecting the object to be coated having the chemical conversion film formed thereon to electrodeposition coating.

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