JP2005324543A - Surface treated steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel especially for heavy duty coated steel free from environmental loading material, which reduces cathodic separation from an edge of a resin coated layer formed on the surface of the steel during cathodic protection. <P>SOLUTION: A surface treated steel is composed of, a surface treated layer 2 which contains a partial hydrolysate of an aluminum coupling agent comprising an aluminum compound having an oxidation number of 3 on the surface of a steel stock 1, and at least one or more resin coating layers 4 laminated through an adhesive layer 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface-treated steel material that does not contain environmentally hazardous substances, and particularly for coated steel materials for heavy anticorrosion.

  Coated steel materials represented by polyethylene lining and polyurethane lining in social infrastructure such as bridges, piles, piers, outdoor steel structures, etc. have severe corrosive environments such as seaside atmosphere, underground, rivers, etc. Since it is used in places, high durability is required. For this reason, a chromate conversion treatment is usually performed as a base treatment. However, since chromium (VI) is an environmentally hazardous substance, an alternative chemical conversion treatment that does not use an environmentally hazardous substance is required while maintaining performances such as primary adhesion, water-resistant adhesion, and resistance to cathode peeling. Here, the primary adhesion refers to the adhesion of the steel coating layer in the atmosphere, and the water-resistant adhesion refers to the adhesion of the steel coating layer when the steel is immersed in an electrolyte solution for a long time in water. Cathode releasability refers to the adhesion of the steel coating layer when cathodic protection is applied to the steel being immersed.

  Here, the cathodic protection will be described in some detail. Cathodic protection means that the base metal is made lower than the natural corrosion potential, preferably by lowering the potential until the base metal reaches a thermodynamically stable region in a given environment. It is widely known as a highly reliable anticorrosion principle. Originally performed on bare steel, but steel is coated or coated to improve the anticorrosion properties of areas where galvanic protection is difficult to continue, such as the tidal zone, to reduce landscape, power costs, and to expand the reach of the anticorrosion current. Often done in

  As the potential for cathodic protection, a potential of −2 to −0.7 V (vs. saturated potassium chloride / silver chloride / silver electrode, the same shall apply hereinafter) is recommended as a potential for sufficiently protecting the steel surface and keeping the cathode peeling rate small. In the ocean, river, and water, -1.2 to -0.7 V is preferable, more preferably -1.1 to -0.9 V, and in the ground, -2.0 to -2.0 V. ~ -1.5V is recommended. If it exceeds −0.7 V, the cathode peeling rate is reduced, but the anticorrosion effect may be reduced. Moreover, although it is sufficiently anticorrosive at a potential of −1.5 V in the sea or river and less than −2.0 V in the ground, the cathode peeling rate may not be negligible.

In order to apply the cathodic protection current (voltage), an external power source or a galvanic electrode such as aluminum alloy or zinc can be used.
Since actual cathode stripping proceeds slowly, in an evaluation test, the cathode stripping resistance is often evaluated by an accelerated test at an elevated temperature.

  As a chromium alternative chemical conversion treatment that has been used recently, a silane coupling agent or a condensation polymer thereof can be used. These hydrolysates are considered to generate metal base atoms M and a bond called M—O—Si and exhibit high adhesion. In addition, an organic resin, an organic inhibitor, or a metal ion is also added to improve the characteristics.

  However, the treatment of the silane coupling agent system is not satisfactory. Actually, even if the primary adhesion and the water-resistant adhesion are improved, the cathode peeling resistance is not so improved. Alternative substances that do not use other environmentally hazardous substances have the same tendency. However, if the chemical conversion treatment is not performed (no treatment), the performance required for the heavy anticorrosion coated steel material cannot be satisfied.

  Here, the cathode peeling will be described. In the coated steel material during cathodic protection, peeling of the coating film or coating (cathode peeling) proceeds from the coating end. In general, the lower the potential at the time of cathodic protection, the higher the anticorrosion property, but the cathode peeling becomes prominent, which is a big problem. Since the coating film peeling speed determines the life of the coating system, a technique for suppressing the cathode peeling phenomenon of the coating layer (naturally, environmentally friendly type that does not use hexavalent chromium) is desired. Cathodic stripping that occurs during cathodic protection differs in principle from stripping that occurs in normal air. Peeling that occurs in the atmosphere occurs due to corrosion that occurs at the point where water and oxygen penetrate in the thickness direction and reach the steel material due to coating defects such as coating films and films. Therefore, penetration of water and oxygen can be prevented by increasing the thickness of the coating or by performing chemical conversion treatment with excellent corrosion resistance.

  Japanese Patent Application Laid-Open No. 11-12719 (Patent Document 1) discloses a technique of alternately laminating selectively permeable substances of anions and cations on the surface of a steel material on which a corrosion-resistant film is formed. This technical idea is to suppress the phenomenon in which cations and anions move from the external environment across the coating surface to the steel base material by the laminated structure of the coating film, and aims to improve the corrosion resistance of the steel base material.

  On the other hand, cathode peeling during cathodic protection involves cations such as sodium ions in the environment penetrating from the side along the steel / coating resin interface. It reaches. Thus, although the appearance is not deteriorated, the cathode peeling always proceeds and expands under the coating. Although it is a phenomenon similar to the separation in the atmosphere, the principle is different. Therefore, it is easy to use a general surface treatment technology idea that attempts to block corrosion factors by increasing the coating thickness or laminating a non-permeable layer, or to suppress the metal anode reaction rate with an inhibitor. Even if applied to the above, it is ineffective or not very effective in preventing this cathode peeling.

Japanese Patent Laid-Open No. 11-12719

  Therefore, there is a strong demand for an alternative chemical conversion treatment that improves the performance required for heavy anticorrosion coated steel materials and does not use environmentally hazardous substances. Accordingly, an object of the present invention is to provide a surface-treated steel material that solves the above-described problems of the prior art and does not use environmentally hazardous substances.

(1) A surface-treated steel material obtained by laminating a chemical conversion treatment layer containing a partial hydrolyzate of an aluminum coupling agent and at least one resin coating layer on the steel material surface.
(2) The surface-treated steel material according to (1), wherein the content of the partial hydrolyzate of the aluminum coupling agent is 1 mg / m ^{2 to} 1 g / m ² in terms of aluminum.
(3) The surface-treated steel material according to (1) or (2), wherein the partial hydrolyzate of the aluminum coupling agent has an average composition represented by the formula (I).
_{Al (OC n H 2n + 1} ) x (OH) yO (3-xy) / 2 ···· (I)
(Where 0.1 ≦ x ≦ 1, 2 ≦ y ≦ 2.9, 1 ≦ n ≦ 10)

(4) In the chemical conversion treatment layer, epoxy resin, acrylic resin, urethane resin, polyester resin, urea resin, tungstate ion, molybdate ion, vanadate ion, borate ion, condensed borate ion Or a surface treatment according to (1), which contains at least one compound selected from salts thereof, rare earth ions or salts thereof, aluminate ions or salts thereof, phosphate ions or salts thereof, condensed phosphate ions or salts thereof. Steel material.

(5) The surface-treated steel material according to (4), wherein the content of the compound in the chemical conversion treatment layer is 60% by mass or less.
(6) The surface-treated steel material according to (1), (4) or (5), wherein the chemical conversion treatment layer contains one or more hydrolyzate of silane coupling agent or silica.
(7) In the surface-treated steel material according to (6), the total content ratio of silicon in the hydrolyzate of the silane coupling agent or one or more compounds of silica is 15% by mass or less based on the aluminum element. is there.

  According to the product of the present invention, it is possible to improve all the performances required for heavy anticorrosion coated steel without using environmentally hazardous substances.

Hereinafter, the best mode for carrying out the present invention will be described in detail. FIG. 1 is a schematic cross-sectional view of a steel product according to the present invention. In the figure, a treated layer 2 of the present invention is provided on the surface of a steel substrate 1, and an adhesive layer 3 is provided thereon. Furthermore, a resin coating layer 4 is provided thereon. Although the steel base material 1 used for this invention will not be limited if iron is a main component, The low alloy steel materials represented by normal steel materials and seawater-resistant steel, and stainless steel materials can be illustrated. In addition, zinc, zinc alloy, aluminum, aluminum alloy, magnesium-containing alloy or the like may be plated or sprayed as necessary, and the amount of adhesion is usually recommended to be 50 to 500 g / m ^2. However, neither is limited. Further, by forming the chemical conversion treatment layer of the present invention, a surface-treated steel material having excellent corrosion resistance and little performance variation can be obtained.

  Before the chemical conversion treatment, the surface of the steel material must be sufficiently polished and cleaned by blasting, pickling or alkaline degreasing. This is because the formation of the metal / processed film layer interface is necessary to exhibit the action of the present invention. The blasting process is a means that can easily and reliably remove the oxide layer and scale on the steel surface at the site, and examples thereof include sandblasting and shot blasting. The degree of surface preparation should be a level from which red rust, black rust and other scales on the steel surface are removed (preferably Sa2 1/2 or more). Pickling removes oxides, such as red rust formed in the surface, by washing with 5 mass% hydrochloric acid etc., for example. Alkaline degreasing refers to a process of removing rust preventive oil and the like adhering to the surface with an alkaline surfactant solution.

The chemical conversion treatment usually refers to a treatment in which the surface of the steel material undergoes a chemical change by the chemical conversion treatment liquid and the surface is modified. In the present invention, although the chemical reaction with the surface is not clear, it is used in the sense that the steel material surface and the material layer of the present invention are in contact with each other to form an interface.
The resin coating layer formed on the chemical conversion treatment layer may be a single resin layer or a laminate of two or more layers as long as the entire surface of the steel material is covered. In the case of lamination, examples include a primer layer for the purpose of improving corrosion resistance and adhesion, an adhesive layer, and a coated top layer responsible for blocking corrosive substances in the external environment. The resin that can be used for the resin coating layer is a polymer (organic resin) having a C—C bond as a skeleton, a polymer (including a semimetal such as silicon) -oxygen bond or a Si—N bond (inorganic resin) as a skeleton. , Both are bonded at a molecular level, that is, a polymer having a COM (metal, semimetal) skeleton (hybrid resin) in whole or in part. Specifically, an epoxy resin, a polyethylene resin, an organopolysiloxane resin, etc. can be illustrated.

The primer layer can be provided to improve the adhesion between the base material and the adhesive layer, and to improve the corrosion resistance of the base material, and examples include, but are limited to, an epoxy primer and zinc rich paint. is not.
The adhesive layer can be provided for the purpose of adhering the steel material or primer layer and the coating layer, and examples thereof include, but are not limited to, an epoxy adhesive and a modified polyethylene adhesive.

  The covering top layer is not limited as long as it has weather resistance, corrosion resistance, and water-resistant adhesion to the underlayer, and the covering top layer may be further laminated on the covering top layer. In addition to normal coating (top, intermediate coating), thick film type coating, film, sheet and the like can be exemplified. The thickness is suitably 0.05 mm to 10 mm. In the case of a thermoplastic resin film or resin sheet, it may be directly bonded by thermal fusion, or may be bonded using a film having an adhesive layer on the back. In addition, for the purpose of improving corrosion resistance, adhesion, and design, it is also possible to use a metal having excellent corrosion resistance, such as aluminum, stainless steel, titanium, etc., as a foil, and laminate it to a steel material. Even when the metal foil is laminated via the organic resin adhesive layer, it can be regarded as the surface-treated steel material of the present invention.

  The cathodic peeling phenomenon is thought to occur because cations such as sodium ions penetrate from the side along the interface between the steel and the coating, and the area becomes alkalized. As a result, it was found that the substance represented by the formula (I) has an effect of inhibiting the cathode peeling phenomenon. The elucidation of the detailed reason is a topic for the future. However, aluminum (III), which has a large positive charge, inhibits the movement of sodium ions and the like in the external environment from the side, and the organic functional group is It is presumed that the adhesion is improved and the Al—O bonds network the coating film. And in order to form a network, it is thought that the number of organic functional groups couple | bonded with a trivalent aluminum atom is restrict | limited.

  On the other hand, in the silane coupling agent system treatment, in M-O-Si, silicon atoms are much less positively charged than aluminum, so adhesion and film strength are sufficient, but the steel / coating interface. Can not inhibit the cations entering along Therefore, it is difficult to improve the cathode peel resistance. Thus, the technical idea of the present invention optimizes the chemical composition of the chemical conversion coating layer containing aluminum (III) immediately above the steel surface in order to suppress the movement of cations along the steel / chemical conversion treatment interface. It is said that the peeling of the coating layer is reduced by making it.

Formula (I) shows a material layer composed of aluminum (III) and its network by an average chemical composition formula using a structural formula. Since n, x, y, and z are average values, they are real numbers having significant digits. OC _n H _{2n + 1} is an alkoxy group, and when n is small, the hydrolysis rate is fast, and when n is large, adhesion and paintability with an organic resin are improved. Preferably 1 to 5 is recommended. When there is one type of alkoxyl group, n is a natural number, but when there are two or more types, the value of n is an average value weighted by the molar ratio of each alkoxy group to aluminum.

  x is the total value of the molar ratio of all alkoxyl groups in the chemical conversion film to aluminum. When 0.1 ≦ x, the adhesion with the resin is improved. When x <0.1, the wettability / adhesiveness of paints, primers, adhesives, and the like deteriorates. When 1 <x, the treated film is not sufficiently polymerized, and the adhesiveness deteriorates. Therefore, the chemical conversion treatment containing aluminum (III) was made practical by defining x in an appropriate range.

  y is the molar ratio of Al—OH groups to aluminum. Therefore, x and y in the formula (I) can be obtained from the hydrolysis reaction rate t of the aluminum coupling agent. Since 1 mol of the aluminum coupling agent has 3 mol of alkoxy groups, when the hydrolysis reaction rate is t (0 ≦ t ≦ 1), 3 tmol of alkoxy groups become hydroxyl groups. ) Mole of alkoxy groups remain. Therefore, at this time, x = 3 (1-t) and y = 3t. t is easily determined from the molar ratio of aluminum and alkoxy groups, from the molar ratio of the alkoxy groups after the initial treatment and from the treatment, or from the mass reduction rate after the initial treatment and after the treatment.

  3-xy (= z) represents the molar ratio of oxide ions to aluminum. Occurs by condensation of OH groups. In natural drying, z is 0 to 0.01, and becomes 0.01 to 3 by baking. In the chemical conversion treatment for the coated steel material, it is usually within the range of 0.01 to 1, preferably 0.01 to 0.5, particularly preferably 0.01 to 0.1.

If the amount of aluminum deposited is less than 1 mg / m ² , there is no practical effect, so it must be more than that. When the adhesion amount is large, the corrosion resistance and water resistance adhesion are improved due to the barrier effect, but when the cathode peeling resistance is more than 1 g / m ² , it almost reaches saturation. From the standpoint of chemical conversion treatment, it is defined as less than 1 g / m ² , but a coated steel sheet using the composition of the present invention as a paint is also possible, and in that case, even an adhesion amount of 100 g / m ² can be put to practical use. The chemical conversion treatment layer of the present invention can be prepared by dissolving an aluminum coupling agent in an organic solvent, immersing / applying a solution containing water adjusted in pH as necessary to a steel material, and drying / baking. . The processing method will be described below.

Aluminum coupling agent refers to aluminum alcoholate represented by the general formula _{Al (OC n H 2n + 1} ) 3, Al (OC 2 H 5) 3, Al (OC 3 H 7) 3, Al (OC 4 H ₉ ) ₃ and Al (OC ₃ H ₇ ) ₂ (OC ₄ H ₉ ) can be exemplified. These undergo a hydrolysis reaction with water to produce Al-OH. The treatment concentration can range from 0.01% by mass to saturation concentration, and is usually prepared in the range of 0.05 to 5% by mass, desirably in the range of 0.1 to 2% by mass. The organic solvent is not particularly limited, and examples thereof include alcohols such as ethanol, propanol, and butanol, acetate esters, acetone, xylene, and the like. In order to accelerate drying, an organic solvent having high volatility, particularly an organic solvent having a boiling point of 90 ° C. or less is desirable.

  The pH-adjusted water is usually recommended in the neutral range of pH 5.5 to 8.0. However, if the aluminum coupling agent with a large n or the coating temperature is low, ammonia or the like is added to the alkaline catalyst. An action may be imparted, and it is recommended to adjust to pH 8-11. Water is added in a volume that dissolves in the organic solvent, but the theoretical amount of water required to be in the range of x in formula (I) is 2 to 2.9 times the molar concentration of the aluminum coupling agent. It is.

In the presence of sufficient water, the aluminum coupling agent is finally all hydrolyzed and eventually polymerizes, but temporarily becomes a hydroxide. Therefore, after adding water, sufficient time is not given to the hydrolysis reaction (typical time is within 10 minutes), and -OC _n H _{2n + 1} remains in the chemical conversion film by coating and drying. be able to. That is, if it is a volatile organic solvent, it will dry quickly after coating. However, if it takes a long time to dry after coating, or if it is dried in a high humidity environment, the hydrolysis reaction will continue with moisture in the air. It is necessary. Drying is recommended by hot air drying or heating of the substrate.

  Moreover, it can bake after application | coating. It is known that when the hydrolyzate of the coupling agent is baked at several hundred degrees C., it becomes glass, but the present invention is a chemical conversion treatment film and does not need to be made into glass. Therefore, a baking temperature of 250 ° C. or lower is sufficient, preferably 60 to 200 ° C., more preferably 60 to 120 ° C. is recommended. In addition, baking said here says the state in which the resin coating layer is not formed on the chemical conversion treatment layer. When a part of the —OH group is dehydrated and condensed by drying and baking, an Al—O—Al bond is generated.

  In order to further improve the post-treatment properties such as corrosion resistance, adhesion, coating and adhesion of the chemical conversion treatment layer, compounds such as organic resins, organic polymers, transition metal ions, transition metal oxo ions, and silicon compounds can be added. These compounds are incorporated into the network described by the formula (I) by hydrogen bonding with Al-OH or charge transfer bonding with Al-O-Al, thereby making the chemical conversion coating film stronger. To do. If these are larger than the specified amount, the concentration of aluminum (III) becomes relatively small, and the effect of reducing cathode peeling cannot be seen.

Epoxy resin is a general term for a material in which substances having an epoxy functional group —OCH (O) CH ₂ are polymerized such as (C _n H _{2n + 1} O) ₃ Si (CH ₂ ) _m OCH (O) CH _2. say. At present, it mainly refers to a substance obtained by copolymerizing bisphenol A with epichlorohydrin or the like, but is not limited thereto.

  Similarly, acrylic resin is a polymerized / copolymerized product of acrylic acid, urethane resin is a polymerized / copolymerized product of hexamethylene diisocyanate butanediol, polyester is a substance having an ester group (-COOR; R is an organic functional group), The urea resin is a polymerized / copolymerized product of excamethylene diisocyanate and hexamethylene diamine. Here, the polymerization / copolymerized product refers to a product produced by these production methods, and the production method is not limited as long as the chemical structural formula is the same.

  These resins may exist as a component of a polymer blend or a polymer alloy in addition to a simple substance. Usually, it is used as fine particles dispersed in the chemical conversion treatment liquid, but it may be contained in the treatment liquid in the form of a resin and a curing agent and polymerized after coating. These can further improve film-forming properties, paintability, and coating film adhesion.

  Metal ions and metal oxo ions further improve the corrosion resistance and cathode peel resistance. Although the product of the present invention is premised on cathodic protection, there are some areas where cathodic protection is difficult to be applied and some areas where the anticorrosion is not applied. In some cases, high corrosion resistance / adhesion is often required in these areas. Ions may be hydrated in the chemical conversion coating, or may form complexes with hydroxide ions and others. Since the ions listed in the claims are limited to those having a small environmental load, they do not contain chromium ions, but if chromium ions are also added, the same performance is exhibited. Rare earths refer to Sc, Y, lanthanoids and actinoids, but it is not recommended to use radioactive elements such as plutonium contained therein.

As these metal ions, tungstate ions (WO ⁴⁻ ), molybdate ions (MoO ⁴⁻ ), vanadate ions (VO ₄ ³⁻ ), borate ions (BO ₃ ³⁻ ), condensed borate ions (B ₄₎ O ₇ ²⁻ etc.), rare earth ions (Y ³⁺ , Ce ³⁺ , Ce ⁴⁺ etc.), aluminate ions AlO ₂ ⁺ ), phosphate ions (PO ₄ ³⁻ ), polyphosphates as condensed phosphate ions ions ^{_{(P n O 3n + 1 (}} n + 2) -) and metaphosphate ion ^{_{(P m O 3m m-) (}} n is 2 or more, m is 3 or more), and was defined these compounds.

By adding silica (SiO ₂ ) or Si—O to the chemical conversion treatment layer composition, it is possible to improve the corrosion resistance, adhesion, cathode peel resistance, and chemical conversion film-forming property. Si-O is incorporated into a network with a film structure in the same manner as aluminum. However, even if Si-O exceeds 15% by mass with respect to aluminum, the coating does not become stronger. In order to introduce silicon into the film, a silane coupling agent, a condensation polymer thereof, a hydrolyzate thereof, silica, or the like is added to the chemical conversion solution.

Silane coupling _{agent, (C n H 2n + 1} O) 4 Si, (C n H 2n + 1 O) 3 SiR, (C n H 2n + 1 O) 2 SiRR ', (C n H 2n + 1 O) is a compound represented by SiRR′R ″ (n is a natural number, R, R ′, R ″ are organic functional groups). The alkoxy group is sequentially hydrolyzed to generate an OH group, which becomes a silane coupling agent hydrolyzate. In addition, a polycondensation product of a silane coupling agent (C _n H _{2n + 1} O) _{2m + 2} Si _m O _m-1 is also sequentially hydrolyzed in the same manner, and finally (OH) _{2m + 2} Si _m O _m- to _1. These OH groups are bonded to other functional groups, or the OH groups are condensed with each other to generate Si—O—Si. When the alkoxy group remains without being hydrolyzed, it can be identified with the alkoxy group in the formula (I), and thus the x value increases.

A 6 mm-thick rolled steel material was shot blasted (Sa2 1/2). Pure water (pH = 6.5) was added to an ethanol solution of Al (OC ₃ H ₇ ) ₃ to prepare a chemical conversion treatment solution. Depending on the sample, an aqueous acrylic emulsion, zinc borate (Zn ₃ (BO ₃ ) ₂ ), and an aqueous silica sol (neutral) were added. By changing the concentration of Al (OC ₃ H ₇ ) ₃ and the amount of pure water added, the adhesion amount of the compound of formula (I) and the x value in the formula (I) were adjusted. After adding water, it was applied to the sample and dried with a dryer. On top of this, a polyethylene resin sheet having a thickness of 2 mm was pressure-bonded via a modified polyethylene resin adhesive sheet. Alternatively, a tar epoxy resin coating was applied in a thickness of 200 μm, dried and cured (abbreviated as TE).

In the treatment (comparative example) using only the silane coupling agent, a 1% by mass aqueous solution (hydrolyzed and dissolved) of γ-glycidoxypropyltrimethoxysilane was applied. The untreated sample (comparative example) was pressure-bonded to the polyethylene resin sheet in the same manner after the shot blast treatment.
The adhesion amount of the compound of the formula (I) is obtained from the aluminum peak height of XPS (X-ray photoelectron spectroscopy), and the value of x is the C—H infrared absorption peak (about 2900 to 3000 cm ⁻¹ ) of the treated film. ).

In the primary adhesion test, a peel test was performed on the prepared sample as it was. In the water-resistant adhesion test, the sample was immersed in a 50% 3% sodium chloride aqueous solution for half a year and then peeled in the same manner.
The cathode peel test was conducted at 60 ° C. for 1 month. A hole reaching a base with a diameter of 6 mm was formed in the center of the sample plate and immersed in a 3% by mass sodium chloride aqueous solution, and the potential of the steel material was adjusted to -1.5 V (vs. sat. -KCl / AgCl / Ag). After completion of the test, the coating layer was attached and the average peel distance from the circumference of the hole was determined.

The test results are shown in Tables 1 and 2. In the table, Al is Al (OC ₃ H ₇ ) x (OH) yO _{(3-xy) / 2} , and Si is an abbreviation for a silane coupling treatment substance. The peel strengths listed in Table 1 as> 20 kg / cm mean that the polyethylene coating was broken during the measurement. The composition ratios in Table 2 are mass% of the compound.

It is a schematic cross section of the steel product according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel material base material 2 This invention process layer 3 Adhesive bond layer 4 Resin coating layer


Patent applicant: Nippon Steel Corporation
Attorney Attorney Shiina and others 1

Claims (7)

A surface-treated steel material obtained by laminating a chemical conversion treatment layer containing a partial hydrolyzate of an aluminum coupling agent and at least one resin coating layer on a steel material surface. The surface-treated steel material according to claim 1, wherein the content of the partial hydrolyzate of the aluminum coupling agent is 1 mg / m ^{2 to} 1 g / m ² in terms of aluminum. The surface-treated steel material according to claim 1 or 2, wherein the partial hydrolyzate of the aluminum coupling agent has an average composition represented by the formula (I).
_{Al (OC n H 2n + 1} ) x (OH) yO (3-xy) / 2 ···· (I)
(Where 0.1 ≦ x ≦ 1, 2 ≦ y ≦ 2.9, 1 ≦ n ≦ 10) In the chemical conversion treatment layer, epoxy resin, acrylic resin, urethane resin, polyester resin, urea resin, tungstate ion, molybdate ion, vanadate ion, borate ion, condensed borate ion or salt thereof The surface-treated steel material according to claim 1, comprising at least one compound selected from the group consisting of: rare earth ions or salts thereof, aluminate ions or salts thereof, phosphate ions or salts thereof, condensed phosphate ions or salts thereof. The surface-treated steel material according to claim 4, wherein a content ratio of the compound in the chemical conversion treatment layer is 60% by mass or less. The surface-treated steel material according to claim 1, 4 or 5, wherein the chemical conversion treatment layer contains one or more hydrolyzate of silane coupling agent or silica. The surface-treated steel material according to claim 6, wherein a total content ratio of silicon in the hydrolyzate of the silane coupling agent or one or more compounds of silica is 15% by mass or less based on the aluminum element.

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