JP2006283045A - Surface-treated steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treated steel wherein the cathode is prevented from being peeled off from an end face of a resin-coated layer deposited on the surface of the steel during the cathodic protection. <P>SOLUTION: A titanium compound treatment layer with the oxidation number of the predetermined composition being 4 is laminated on the surface of the surface-treated steel, and a resin-coated layer is laminated thereon. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 the seaside atmosphere, seawater, underground and rivers. 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, primary adhesion refers to the adhesion of the steel material coating layer in the atmosphere, water resistance adhesion refers to the adhesion of the steel material coating layer when the steel material is immersed in the electrolyte solution for a long time in water, Cathodic peel resistance further 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 -1.5V is recommended. If it exceeds −0.7 V, the cathode peeling rate is reduced, but the anticorrosion effect may be reduced. Further, when the potential is -1.5 V in the sea or river and less than -2.0 V in the ground, the corrosion is sufficiently prevented, but 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 the cathodic protection, the coating film or the coating peels off from the coated 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 is different in principle from stripping that occurs in normal air. Peeling that occurs in the atmosphere occurs due to corrosion or cathodic reaction that occurs at the point where water or oxygen penetrates in the thickness direction and reaches the steel material due to coating defects such as coating films and films. Therefore, it can be prevented by increasing the thickness of the coating to prevent the entry of corrosion factors such as water and oxygen, 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 a steel material surface 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 stripping 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 that seems to be similar to the delamination in the atmosphere, the principle is different, so the corrosion factor is blocked by increasing the thickness of the coating, or by laminating a non-permeable layer, or the metal anode with an inhibitor. Even if a general surface treatment technology idea that attempts to suppress the reaction rate is easily applied, it is ineffective or less 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 is excellent in cathode peeling, satisfies the performances required for conventional heavy anticorrosion steel materials such as primary and secondary adhesion, 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 hydrolysis product of a titanium coupling agent and at least one resin coating layer on a steel material surface.
(2) The surface-treated steel material according to (1), wherein the content of the partial hydrolyzate of the titanium coupling agent is 1 mg / m ^{2 to} 1 g / m ² in terms of titanium.
(3) The surface-treated steel material according to (1) or (2), wherein the partial hydrolyzate of the titanium coupling agent has an average composition represented by the formula (I).
_{Ti (OC n H 2n + 1} ) x (OH) y O (4-xy) / 2 ···· (I)
(Where 0.1 ≦ x ≦ 1, 3 ≦ y ≦ 3.9, 1 ≦ n ≦ 10)

(4) In the chemical conversion treatment layer, epoxy resin, acrylic resin, urethane resin, polyester resin, urea resin, or a cured product thereof, tungstate ion, molybdate ion, vanadate ion, boric acid The surface-treated steel material according to (1), which contains at least one compound selected from ions, condensed borate ions or salts thereof, rare earth ions or salts thereof.
(5) The surface-treated steel material according to (4), wherein the total mass ratio of the compound in the chemical conversion treatment layer is twice or less with respect to the titanium element mass.

(6) The surface-treated steel material according to (1), (4) or (5), which contains a hydrolyzate of a silane coupling agent in the chemical conversion treatment layer.
(7) The content of the hydrolyzate of the silane coupling agent in the chemical conversion treatment layer of silicon element is 15 mol% or less with respect to the titanium element.

  According to the present invention, it is possible to improve all performances required for heavy anticorrosion coated steel materials 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, the treatment layer 2 of the present invention is provided on the surface of a steel substrate 1, and the 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 the main component surface, a normal steel material, seawater-resistant steel, and a stainless steel material can be illustrated. Further, by forming the chemical conversion treatment layer of the present invention, it is possible to obtain a surface-treated steel material having excellent corrosion resistance and little variation in performance. Before the chemical conversion treatment, the surface of the steel material must be sufficiently polished and washed 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 (preferably Sa2 1/2 or more) from which red rust, black rust and other scales on the steel surface have been removed. 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. Resins that can be used for the resin coating layer are polymers having a C—C bond as a skeleton (organic resin), metals (including semimetals such as silicon) -oxygen bonds and Si—N bonds as a skeleton (inorganic resin), Alternatively, a polymer (hybrid resin) in which both are bonded at a molecular level, that is, a COM (metal, semimetal) skeleton 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. Examples include, but are limited to, epoxy primers and zinc rich paints. 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 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 has been found that the substance represented by the formula (I) as an average composition has an effect of inhibiting the cathode peeling phenomenon. The elucidation of the detailed reason is a future task, but titanium (IV), 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 enhanced and Ti—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 tetravalent titanium atom is restrict | limited.

  On the other hand, in the silane coupling agent system treatment, in M-O-Si, since silicon atoms are much less positively charged than titanium, 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 titanium (IV) directly on the surface of the steel material in order to suppress the movement of cations along the steel material / chemical conversion treatment interface. It is said that the peeling of the coating layer is reduced by making it.

The formula (I) shows a material layer composed of titanium (IV) and its network by an average chemical composition formula using a structural formula. Since n, x, and y are average values, they have significant digits. It is a real number. Although defined by the average chemical composition, it is preferable that the molecular formula is composed only of the substance represented by the formula (I). -OC _n H _{2n + 1} is an alkoxy group, and when n is large, the hydrolysis rate is fast, and when it is small, adhesion and paintability with an organic resin are poor. More preferably, 2 to 5 is recommended. In general, coupling means that two other molecules are cross-linked by a reactive group. Therefore, a coupling agent refers to a substance having two or more alkoxy groups. Therefore, the compound represented by the formula (I) is not a coupling agent.

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 titanium.
x is the total value of the molar ratio of all alkoxyl groups in the chemical conversion film to titanium. 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, and when 1 <x, the treated film is not sufficiently polymerized, and the adhesiveness deteriorates. Therefore, the chemical conversion treatment containing titanium (IV) was made practical by defining x in an appropriate range.

  y is the molar ratio of Ti—OH groups to titanium. Therefore, x and y in the formula (I) can be obtained from the hydrolysis reaction rate t of the titanium coupling agent. Since 1 mol of the titanium coupling agent has 4 mol of alkoxy groups, when the hydrolysis reaction rate is t (0 ≦ t ≦ 1), 4 tmol of alkoxy groups become hydroxyl groups. ) Mole of alkoxy groups remain. Therefore, at this time, x = 4 (1-t) and y = 4t. t is easily determined from the molar ratio of titanium and alkoxy groups, from the molar ratio of alkoxy groups after the initial treatment and after treatment, or from the mass reduction rate after the initial treatment and after treatment.

4-xy / 2 (= z) represents the molar ratio of oxide ions to titanium. 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 titanium element 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 material 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 dissolves a titanium coupling agent in an organic solvent, and if necessary, immerses the steel in a solution adjusted to pH or other additives and applies the solution to the steel. Then, it can be made by drying and baking.
The processing method will be described below.

The titanium coupling agent refers to a titanium alcoholate represented by the general formula Ti (OC _n H _{2n + 1} ) ₄ , Ti (OC ₂ H ₅ ) ₄ , Ti (OC ₃ H ₇ ) ₄ , Ti (OC _4). H ₉ ) ₄ , Ti (OC ₃ H ₇ ) ₃ (OC ₄ H ₉ ) and the like can be exemplified. This alkoxy group causes a hydrolysis reaction with water to produce Ti—OH. The concentration of the treatment liquid can be in the range of 0.01% by mass to the saturated concentration.

  The organic solvent is not particularly limited, and examples thereof include alcohols such as ethanol, propanol, and butanol, acetates, acetone, xylene, toluene, 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 water is usually neutral, but if the titanium coupling agent has a large n or the coating temperature is low, ammonia or the like may be added to impart alkali catalysis, and the water adjusted to pH 8-11 Is recommended. Moreover, when the amount of water in the organic solvent is large and the pH can be measured, and the iron surface corrodes during drying, the solution can be similarly adjusted to pH 8.5 to 10 to prevent corrosion. x can be adjusted by the amount of water, and the theoretical molar amount of water required to be in the range of x of the present invention is 4x times the molar amount of the titanium coupling agent.

The titanium coupling agent is finally all hydrolyzed in the presence of sufficient water, and eventually polymerizes to become 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 even after 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 continues with moisture in the air. It is necessary.

  For drying, hot air drying or heating of the substrate is recommended. 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 invention is a chemical conversion 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, the baking said here is a case where the resin coating layer is not formed on the chemical conversion treatment layer. When some OH groups are dehydrated and condensed by drying and baking, Ti—O—Ti bonds are formed.

  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 Ti-OH or charge transfer bonding with Ti-O-Ti, and the chemical conversion coating film becomes stronger. To do. If these are larger than the prescribed amount, the concentration of titanium (IV) becomes relatively small, and the effect of reducing the cathode peeling becomes difficult to see. By adding a resin, film formability, paintability, and coating film adhesion can be further improved.

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. To tell. At present, a cured product of a substance obtained by copolymerizing bisphenol A or bisphenol F with epichlorohydrin or the like can be exemplified, but it is not limited thereto.

  Similarly, urethane resin is a polymerization / copolymerization product of hexamethylene diisocyanate butanediol, polyester is a substance having an ester group (-COOR; R is an organic functional group), urea resin is polymerization of excamethylene diisocyanate and hexamethylenediamine. -It is a copolymer. Here, the polymerization / copolymerization 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.

  Moreover, the thing suitably hardened with the hardening | curing agent can also be used for these resin. These resins may exist as a component of a polymer blend or a polymer alloy in addition to a simple substance and a cured product thereof. Usually, it is used by being dispersed as fine particles in a chemical conversion treatment liquid, but it may be contained in the treatment liquid in the form of a resin and a curing agent, followed by curing and polymerization after coating.

  A metal ion or a metal oxo ion crosslinks with a polar group of an organic resin or a carbon or titanium atom in the formula (I) to further improve the corrosion resistance and the cathode peeling resistance. In the present invention, although anti-corrosion is a prerequisite, there are some areas where the anti-corrosion is difficult to be applied and areas where the anti-corrosion is not applied. In some cases, high corrosion resistance / adhesion is often required in the area.

  These ions may be hydrated in the chemical conversion film, or may form a complex with hydroxide ions and others. Since the ions listed in the item of means are limited to those having a small environmental load, chromium ions are not included, but the same performance is exhibited if chromium ions are also added. 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.) and their salts were defined. When the total amount of these additives exceeds twice the mass of titanium element, the effect of titanium element is reduced. Although depending on the case, it is usually sufficient to add up to about 0.1 to 0.5 times the titanium element mass.

By adding the hydrolyzate of the silane coupling agent to the chemical conversion treatment layer composition, the stress of the chemical conversion treatment coating is relieved, and the chemical conversion coating film forming property can be improved. Silane coupling _{agent, (C c H 2c + 1} O) 4 Si (C c H 2c + 1 O) 3 SiR, (C c H 2c + 1 O) 2 SiRR ', (C c H 2c + 1 O ) SiRR′R ″ (C is a natural number, R, R ′, R ″ are organic functional groups), but the alkoxy group is sequentially hydrolyzed to become an OH group (silane coupling agent) Hydrolyzate). If the alkoxy group remains without being hydrolyzed, it is identified with the alkoxy group in the formula (I), and thus the x value increases. It is sufficient that these addition amounts are 15 mol% with respect to the titanium element, and even if it is more than this, the network between titanium does not become strong.

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 Ti (OC ₃ H ₇ ) ₄ 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. The adhesion amount of the compound of formula (I) and the x value in the formula (I) were adjusted by changing the concentration and the amount of pure water added. After adding water, it was applied to the sample and dried with a dryer. A polyethylene resin sheet having a thickness of 2 mm was pressure-bonded thereon via a modified polyethylene resin adhesive sheet. Alternatively, a tar epoxy resin coating was similarly applied to 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.
(I) The adhesion amount of the formula compound is determined from the titanium 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. Calculated from height.

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 an aqueous 3% by weight sodium chloride solution at 50 ° C. for half a year and then peeled in the same manner.
The cathode peeling test was conducted at 60 ° C. for 1 month. A hole reaching a 6 mm diameter substrate was opened 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. From the size of the cell, the maximum separation distance is 25 mm.

The test results are shown in Tables 1 and 2. In Tables 1 and 2, Si is an abbreviation for a silane coupling agent, and Ti is an abbreviation for Ti (OC _n H _{2n + 1} ) _x (OH) _y O _{(4-xy) / 2} . The adhesion amount column in Table 2 indicates the adhesion amount (g / m ² ) of each composition, and Ti indicates the adhesion amount of only the titanium element. The peel strengths listed in Table 1 with> 20 kg / cm mean that the polyethylene coating was broken during the measurement.

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 hydrolysis product of a titanium coupling agent and one or more resin coating layers on a steel material surface. The surface-treated steel material according to claim 1, wherein the content of the partial hydrolyzate of the titanium coupling agent is 1 mg / m ^{2 to} 1 g / m ² in terms of titanium. The surface-treated steel material according to claim 1 or 2, wherein the partial hydrolyzate of the titanium coupling agent has an average composition represented by the formula (I).
_{Ti (OC n H 2n + 1} ) x (OH) y O (4-xy) / 2 ···· (I)
(Where 0.1 ≦ x ≦ 1, 3 ≦ y ≦ 3.9, 1 ≦ n ≦ 10) In the chemical conversion treatment layer, epoxy resin, urethane resin, polyester resin, urea resin, or a cured product thereof, tungstate ion, molybdate ion, vanadate ion, borate ion, condensed borate ion or The surface-treated steel material according to claim 1, comprising at least one compound selected from the salts, rare earth ions or salts thereof. The surface-treated steel material according to claim 4, wherein a total mass ratio of the compound in the chemical conversion treatment layer is twice or less with respect to a titanium element mass. The surface-treated steel material according to claim 1, 4 or 5, wherein the chemical conversion treatment layer contains a hydrolyzate of a silane coupling agent. The surface-treated steel material according to claim 6, wherein the content ratio of the hydrolyzate of the silane coupling agent in the chemical conversion treatment layer of silicon element is 15 mol% or less with respect to the titanium element.

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