WO2021065485A1 - Matériau d'acier traité en surface - Google Patents

Matériau d'acier traité en surface Download PDF

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Publication number
WO2021065485A1
WO2021065485A1 PCT/JP2020/034943 JP2020034943W WO2021065485A1 WO 2021065485 A1 WO2021065485 A1 WO 2021065485A1 JP 2020034943 W JP2020034943 W JP 2020034943W WO 2021065485 A1 WO2021065485 A1 WO 2021065485A1
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Prior art keywords
plating layer
mass
coating film
less
steel material
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PCT/JP2020/034943
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English (en)
Japanese (ja)
Inventor
輝生 ▲高▼田
慎太郎 熊倉
洋一 戸崎
諒 内橋
聡 矢尾板
Original Assignee
日鉄鋼板株式会社
日本ペイント・インダストリアルコーティングス株式会社
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Publication of WO2021065485A1 publication Critical patent/WO2021065485A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/09—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/095—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyurethanes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/18—Layered products comprising a layer of metal comprising iron or steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/02—Magnesia
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/02—Compounds of alkaline earth metals or magnesium
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C09D175/06—Polyurethanes from polyesters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/08—Anti-corrosive paints
    • C09D5/10—Anti-corrosive paints containing metal dust
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/63—Additives non-macromolecular organic
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent

Definitions

  • the present invention relates to a surface-treated steel material.
  • Painted steel materials coated with cold-rolled steel materials and plated steel materials as base materials are also called pre-coated metals, and are used for various purposes such as outdoor units for air conditioners, home appliance exterior parts for water heaters, and exterior building materials for roofs, walls, etc. It is used.
  • a coated steel material including a galvanized steel material is usually coated with a rust preventive paint in order to improve rust prevention and prevent rusting.
  • Patent Document 1 describes a molten Zn-Al system by adding Mg or the like into a plating layer. The rust prevention properties of plated steel materials have been improved.
  • the coating film on a steel material such as a plated steel material may be imparted with properties such as rust prevention.
  • a rust preventive coating composition for forming a coating film on a steel material such as a plated steel material Japanese Patent Application Laid-Open No. 2009-227748 (Patent Document 2) states that (A) a specific acrylic resin and a specific polyester resin.
  • At least one type of hydroxyl group-containing film-forming resin (B) bisphenol type epoxy resin, (C) curing agent, (D) epoxy resin having a secondary or tertiary amino group, secondary or tertiary amino group
  • a rust-preventive coating composition containing at least one adhesion-imparting resin selected from the acrylic resin and the resole-type phenol resin and (E) rust-preventive pigment is disclosed.
  • the rust preventive pigment (E) is a vanadium compound of at least one of (1) vanadium pentoxide, calcium vanadate and ammonium metavanadate, and (2) metal silicate and silica fine particles. It is disclosed that it contains at least one kind of silicon-containing compound and (3) phosphoric acid-based metal salt.
  • a chromium-containing paint composition as a rust preventive paint.
  • the chromium-containing coating composition By using the chromium-containing coating composition and forming the chromium-containing coating film, the generation of rust can be suppressed.
  • the use of chromium-containing coating compositions is being restricted due to concerns about adverse effects on the environment. Therefore, as a rust preventive agent other than the chromium compound, a coating composition containing a vanadium compound has been proposed.
  • Patent Document 3 describes a coating composition containing (A) a hydroxyl group-containing coating film-forming resin, (B) a cross-linking agent, and (C) a rust preventive pigment mixture.
  • the rust preventive pigment mixture (C) is derived from (1) vanadium pentoxide, at least one vanadium compound among calcium vanadate and ammonium metavanadate, (2) metal silicate and (3) phosphate-based calcium salt.
  • the coating composition is disclosed.
  • acid rain causes corrosion of the coating film of a coated steel sheet.
  • acid rain means that acid rain-causing substances originating from sulfur dioxide (SO 2 ), nitrogen oxides (NOx), etc. dissolve in rain, snow, fog, etc., and the atmosphere becomes more acidic than usual. It refers to the phenomenon of becoming more acidic or the environment becoming more acidic than usual.
  • SO 2 sulfur dioxide
  • NOx nitrogen oxides
  • the acid rain-causing substance when the acid rain-causing substance is present in a dew condensation and damp environment, at least one of the sulfide and the nitride contained in the acid rain-causing substance may be exposed to a damp state and the corrosion reaction may proceed. is there.
  • the coating compositions described in Patent Documents 2 and 3 have insufficient rust preventive properties, and for example, the rust preventive properties are not sufficient for application to outdoor applications, and there is room for improvement. Moreover, there is room for improvement in rust prevention under acidic environmental conditions. As described above, there is a demand for a surface-treated steel material having rustproof properties under acidic environmental conditions and also having rust preventive properties for a longer period of time.
  • the object to be coated when used outdoors, the object to be coated may be exposed to a high humidity environment, and a surface-treated steel material exhibiting excellent moisture resistance is required. Further, it is required to improve the physical properties such as rust prevention by the aluminum / zinc alloy plated steel material and the physical properties such as rust prevention by the coating film covering the steel material.
  • An object of the present invention is to solve the above problems, and more specifically, to provide a surface-treated steel material which can exhibit excellent rust resistance for a long period of time and also exhibits excellent moisture resistance. Make it an issue.
  • the aluminum-zinc alloy plating layer contains Al, Zn, Si and Mg as constituent elements, and has a Mg content of 0.1 to 10% by mass.
  • the aluminum-zinc alloy plating layer contains 0.2 to 15% by volume of the Si—Mg phase, and the mass ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer is 3% or more.
  • the coating film is a coating film formed from a rust-preventive coating composition containing a coating film-forming resin (A), a cross-linking agent (B), and a magnesium oxide (C).
  • the coating film-forming resin (A) is an ester-based urethane resin.
  • the ester-based urethane resin has a number average molecular weight of 1,000 or more and 40,000 or less, a glass transition point of -50 ° C or more and 70 ° C or less, a solid acid value of 30 mgKOH / g or less, and the above.
  • Magnesium oxide (C) has a lattice constant of less than 0.4214 nm. BET specific surface area is 2.0 m 2 / g or less, Surface-treated steel material.
  • the magnesium oxide (C) is added to 100 g of the artificial acidic sea aqueous solution as the magnesium oxide (C) in the rust preventive coating composition. It is an oxide having a magnesium metal ion concentration of 70 ppm or less in the aqueous solution.
  • the magnesium oxide (C) has a conductivity of 320 ⁇ S / cm in an aqueous solution prepared by adding 1 g of the magnesium oxide (C) to 100 g of pure water. The following oxides.
  • the magnesium oxide (C) is a fired magnesium product fired at a temperature of 1,000 ° C. or higher.
  • the magnesium oxide (C) has a pH of 8 or more in an aqueous solution in which 1 g of the magnesium oxide (C) is added to 100 g of pure water. The average particle size is 0.5 ⁇ m or more and 20 ⁇ m or less.
  • the magnesium oxide (C) is magnesium oxide.
  • the magnesium oxide (C) is added to 100 parts by mass of the resin solid content of the coating film-forming resin (A). It is included in the range of 1 part by mass or more and 150 parts by mass or less.
  • the surface-treated steel material of the present disclosure has a Mg content in the outermost layer having a depth of 50 nm in the aluminum-zinc alloy plating layer, in a region having a diameter of 4 mm and a depth of 50 nm. Is less than 60% by mass.
  • the ratio of the Si—Mg phase on the surface of the aluminum / zinc alloy plating layer of the surface-treated steel material of the present disclosure is 30% or less in terms of area ratio.
  • the surface-treated steel material of the present disclosure is used.
  • Al content in aluminum / zinc alloy plating layer is 25-75% by mass,
  • the Si content is 0.5 to 10% by mass with respect to Al, and the mass ratio of Si: Mg is 100: 50 to 100: 300.
  • the surface-treated steel material of the present invention can exhibit excellent rust resistance for a long period of time, and further can exhibit excellent moisture resistance.
  • the conventional evaluation of rust prevention has a short test time, and the evaluation site has been judged only by the molded portion (flat surface of the object to be coated).
  • objects to be coated with various shapes have been manufactured.
  • the protective effect of the coating film may not be sufficient in the processed portion, the end face, the cross-cut portion, etc., and corrosion occurs from these portions.
  • a coating composition that exhibits excellent rust prevention properties over a long period of time even in a processed portion, an end face, and a cross-cut portion, and further exhibits long-term and even ultra-long-term rust prevention properties. Is required.
  • a paint composition containing a chromium-based compound is used.
  • a coating composition containing a chromium-based compound can satisfactorily suppress the generation of rust on an object to be coated.
  • reduction in environmental load is also required, and it will be necessary to reduce the amount of chromium compounds in the rust preventive paint composition in the future. Conceivable.
  • a vanadium compound such as a vanadate metal salt is used for the purpose of reducing chromium-based compounds.
  • a vanadium compound such as a vanadate metal salt
  • it is effective to increase the amount of the vanadium compound contained in the coating composition.
  • vanadium compounds, especially vanadate are highly water soluble. Therefore, when the coating composition contains a large amount of vanadium compound, the coating film easily absorbs moisture. As a result, there is a problem that the moisture resistance of the coating film is lowered and blisters are generated in the coating film.
  • Such blister of the coating film also causes a decrease in rust prevention property and also causes a decrease in moisture resistance of the coating film. Therefore, if the coating composition contains a large amount of vanadium compound, it may be difficult to provide both long-term rust resistance and moisture resistance.
  • the rust-preventive coating composition of the present invention can exhibit excellent rust-preventive properties over a long period of time, and can further form a coating film exhibiting excellent moisture resistance. Moreover, even under acidic environmental conditions, it is possible to form a coating film showing excellent rust prevention properties for a long period of time. Therefore, for example, the generation of rust that may be caused by "acid rain” or the like can be suppressed.
  • acid rain-causing substances are absorbed by a water film in a dew condensation and humid environment. It is thought that it is possible to prevent problems such as the environment being oxidized and corrosion progressing.
  • the rust preventive coating composition of the present disclosure can exhibit excellent moisture resistance.
  • the present inventors have stated that the rust preventive coating composition of the present disclosure can significantly reduce the moisture absorption of the coating film as compared with, for example, a vanadium compound by containing the specific magnesium oxide (C) according to the present disclosure. I found it. Therefore, the decrease in the moisture resistance of the coating film can be suppressed or greatly reduced, and the occurrence of blisters on the coating film can also be suppressed or greatly reduced.
  • the rust-preventive coating composition of the present disclosure can exhibit excellent rust-preventive properties for a long period of time, and can also form a coating film having excellent moisture resistance.
  • the rust-preventive coating composition of the present disclosure in an object to be coated which can have various shapes, not only a flat surface of the object to be coated but also, for example, a processed portion, an end face, a cross-cut portion and the like. , The protective effect of the coating film can be sufficiently exhibited.
  • the rust-preventive coating composition of the present disclosure can suppress or significantly reduce blister in the processed portion, end face, and cross-cut portion, and even in such a portion, excellent rust prevention and moisture resistance over a long period of time. Can be shown.
  • both the plated steel sheet and the coating film can exhibit excellent rust resistance for a long period of time, and also can exhibit excellent moisture resistance.
  • the surface-treated steel material of the present disclosure has excellent workability, chemical resistance, weather resistance, and scratch resistance, in addition to being able to form a coating film having excellent rust resistance over a long period of time. It is a surface-treated steel material that is also excellent in design and wear resistance.
  • the surface-treated steel material of the present disclosure will be described.
  • the surface-treated steel material of the present disclosure is a surface-treated steel material in which a coating film is formed on the surface of the steel material via a base layer containing at least an aluminum-zinc alloy plating layer.
  • the aluminum-zinc alloy plating layer contains Al, Zn, Si and Mg as constituent elements, and has a Mg content of 0.1 to 10% by mass.
  • the aluminum-zinc alloy plating layer contains 0.2 to 15% by volume of the Si—Mg phase, and the mass ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer is 3% or more.
  • the aluminum-zinc alloy plating layer contains Al, Zn, Si, Cr and Mg as constituent elements, has an Mg content of 0.1 to 10% by mass, and has a Cr content of 0.02 to 1. It is 0.0% by mass, the aluminum-zinc alloy plating layer contains 0.2 to 15% by volume of Si—Mg phase, and the mass ratio of Mg in the Si—Mg phase to the total amount of Mg is 3% or more.
  • a base layer containing at least an aluminum-zinc alloy plating layer (hereinafter, simply referred to as “plating layer”) is formed on the surface of the steel material, and the coating composition according to the present disclosure is used as an upper layer.
  • a coating film using is formed.
  • the steel material include various members such as thin steel plates, thick steel plates, shaped steels, steel pipes, and steel wires. That is, the shape of the steel material is not particularly limited.
  • a base layer is formed by a plating layer and a chemical conversion treatment layer obtained by subjecting the plating layer to a chromate-free chemical conversion treatment. The content of this chemical conversion treatment layer is not particularly limited.
  • the plating layer is formed by hot-dip galvanizing treatment and contains Al, Zn, Si and Mg as constituent elements.
  • Al particularly improves the corrosion resistance of the surface of the plating layer
  • the sacrificial anticorrosion action of Zn suppresses edge creep particularly at the cut end face of the surface-treated steel material, thereby enhancing the corrosion resistance of the surface-treated steel material.
  • Si suppresses excessive alloying between Al and the steel material in the plating layer, and suppresses that the alloy layer (described later) interposed between the plating layer and the steel material impairs the workability of the surface-treated steel material. Will be done.
  • the plating layer when the plating layer appropriately contains Mg, which is a metal lower than Zn, the sacrificial anticorrosion action of the plating layer is strengthened, and the corrosion resistance of the surface-treated steel material is further improved.
  • the plating layer is formed by hot dip galvanizing treatment and contains Al, Zn, Si, Cr and Mg as constituent elements.
  • the plating layer contains 0.2 to 15% by volume of the Si—Mg phase.
  • the Si-Mg phase is a phase composed of an intermetallic compound of Si and Mg, and is dispersed in the plating layer. The higher the volume ratio of the Si—Mg phase in the plating layer, the more the generation of wrinkles in the plating layer is suppressed. This is because in the process in which the hot-dip galvanized metal is cooled during the production of the surface-treated steel to form a plating layer, the Si-Mg phase is contained in the hot-dip galvanized metal before the hot-dip galvanized metal is completely solidified. It is considered that this Si—Mg phase precipitates and suppresses the flow of the hot-dip galvanized metal.
  • the volume ratio of the Si—Mg phase is 0.2 to 15% by volume, preferably 0.2 to 10% by volume, and more preferably 0.4 to 5%. Volume%.
  • the volume ratio of the Si-Mg phase in the plating layer is equal to the area ratio of the Si-Mg phase on the cut surface when the plating layer is cut in the thickness direction.
  • the Si—Mg phase on the cut surface of the plating layer can be clearly confirmed by observation with an electron microscope. Therefore, by measuring the area ratio of the Si—Mg phase on the cut surface, the volume ratio of the Si—Mg phase in the plating layer can be indirectly measured.
  • the plating layer is composed of a Si—Mg phase and other phases containing Zn and Al.
  • the phase containing Zn and Al is mainly composed of an ⁇ —Al phase (dendrite structure) and a Zn—Al—Mg eutectic phase (interdrenite structure).
  • the phase containing Zn and Al is further composed of a phase composed of Mg—Zn2 (Mg—Zn2 phase), a phase composed of Si (Si phase), and an Fe—Al intermetallic compound depending on the composition of the plating layer. It may include various phases such as a constituent phase (Fe—Al phase). Therefore, the volume ratio of the Zn and Al-containing phase in the plating layer is 99.8 to 85% by volume, preferably 99.8 to 90% by volume, and more preferably 99.6 to 95% by volume. ..
  • the mass ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer is 3% by mass or more.
  • Mg not contained in the Si—Mg phase is contained in the phase containing Zn and Al.
  • Mg is contained in the ⁇ —Al phase, the Zn—Al—Mg eutectic phase, the Mg—Zn2 phase, the Mg-containing oxide film formed on the plating surface, and the like.
  • Mg is contained in the ⁇ —Al phase
  • Mg is dissolved in the ⁇ —Al phase.
  • the mass ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer can be calculated after considering that the Si—Mg phase has the stoichiometric composition of Mg2Si.
  • the Si—Mg phase may contain a small amount of elements such as Al, Zn, Cr, and Fe other than Si and Mg, and the composition ratio of Si and Mg in the Si—Mg phase is also stoichiometric. Although it may vary slightly from the composition, it is very difficult to strictly determine the amount of Mg in the Si—Mg phase in consideration of these.
  • the Si—Mg phase when the mass ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer is determined, the Si—Mg phase has a stoichiometric composition of Mg2Si as described above. It is considered to be.
  • the mass ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer can be calculated by the following formula (1).
  • R A / (M x CMG / 100) x 100 ...
  • R indicates the mass ratio (mass%) of Mg in the Si—Mg phase to the total amount of Mg in the plating layer.
  • A indicates the Mg content (g / m 2 ) contained in the Si—Mg phase in the plating layer per unit area in plan view of the plating layer.
  • M indicates the mass (g / m 2 ) of the plating layer per unit area in plan view of the plating layer.
  • CMG indicates the total Mg content (mass%) in the plating layer.
  • A can be calculated from the following formula (2).
  • V 2 indicates the volume (m 3 / m 2 ) of the Si—Mg phase in the plating layer per unit area in plan view of the plating layer.
  • ⁇ 2 indicates the density of the Si—Mg phase, and its value is 1.94 ⁇ 106 (g / m 3 ).
  • ⁇ indicates the mass content ratio of Mg in the Si—Mg phase, and the value is 0.63.
  • V 2 can be calculated from the following equation (3).
  • V 2 V 1 ⁇ R 2 /100 ... (3)
  • V 1 indicates the total volume (m 3 / m 2 ) of the plating layer per unit area in plan view of the plating layer.
  • R 2 indicates the volume ratio (volume%) of the Si—Mg phase in the plating layer.
  • V 1 can be calculated from the following equation (4).
  • V 1 M / ⁇ 1 ... (4) ⁇ 1 indicates the density (g / m 3 ) of the entire plating layer.
  • the value of ⁇ 1 can be calculated by weighted averaging the densities of the constituent elements of the plating layer at room temperature based on the composition of the plating layer.
  • Mg in the plating layer is contained in the Si—Mg phase in a high ratio as described above. Therefore, the amount of Mg present on the surface layer of the plating layer is reduced, which suppresses the formation of the Mg-based oxide film on the surface layer of the plating layer. Therefore, wrinkles in the plating layer caused by the Mg-based oxide film are suppressed.
  • This ratio is more preferably 5% by mass or more, further preferably 20% by mass or more, and particularly preferably 50% by mass or more.
  • the upper limit of the ratio of Mg in the Si—Mg phase to the total amount of Mg is not particularly limited, and this ratio may be 100% by mass.
  • the Mg content is preferably less than 60% by mass even in a region having a diameter of 4 mm and a depth of 50 nm.
  • the Mg content in the outermost layer of this plating layer can be measured by glow discharge emission spectroscopy (GD-OES: Glow Discharge-Optical Measurement Spectroscopy).
  • GD-OES Glow Discharge-Optical Measurement Spectroscopy
  • the Mg content in the outermost layer of the plating layer is more preferably less than 40% by mass, further preferably less than 20% by mass, and particularly preferably less than 10% by mass.
  • the Mg content is more preferably less than 40% by mass, further preferably less than 20% by mass, and particularly preferably less than 10% by mass.
  • the Mg content in the MgO oxide of the stoichiometric composition is about 60% by mass. That is, when the Mg content is less than 60% by mass, MgO having a stoichiometric composition (an oxide film of MgO alone) does not exist in the outermost layer of the plating layer, or MgO having this stoichiometric composition is formed. It means that it is significantly suppressed. In the present embodiment, the excessive oxidation of Mg in the outermost layer of the plating layer is suppressed, so that the formation of an oxide film of MgO alone is suppressed.
  • a composite oxide containing a small amount or a large amount of oxides of elements other than Mg such as Al, Zn, and Sr is formed, and therefore the content of Mg in the surface layer of the plating layer is relatively reduced. it seems to do.
  • the area ratio of the Si—Mg phase on the surface of the plating layer is preferably 30% or less.
  • the Si—Mg phase is thin and easily formed in a mesh shape on the surface of the plating layer, and when the area ratio of the Si—Mg phase is large, the appearance of the plating layer changes.
  • the plating surface distribution state of the Si—Mg phase is non-uniform, uneven gloss is visually observed in the appearance of the plating layer. This uneven gloss is a poor appearance called sagging.
  • the area ratio of the Si—Mg phase on the surface of the plating layer is 30% or less, sagging is suppressed and the appearance of the plating layer is improved.
  • the fact that the surface of the plating layer has a small amount of Si—Mg phase is effective for maintaining the corrosion resistance of the plating layer for a long period of time.
  • the amount of the Si—Mg phase deposited on the inside of the plating layer is relatively increased. Therefore, the amount of Mg inside the plating layer is increased, so that the sacrificial anticorrosion action of Mg is exhibited in the plating layer for a long period of time, whereby the high corrosion resistance of the plating layer is maintained for a long period of time. become.
  • the area ratio of the Si—Mg phase on the surface of the plating layer is more preferably 20% or less, further preferably 10% or less. It is particularly preferable if it is 5% or less.
  • the Mg content in the plating layer is in the range of 0.1 to 10% by mass as described above. If the Mg content in the plating layer is less than 0.1% by mass, the corrosion resistance of the plating layer cannot be sufficiently ensured. If this content is more than 10% by mass, the corrosion resistance is lowered, and dross is likely to occur in the hot-dip galvanizing bath during the production of the plated steel material.
  • the content of this Mg is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more. Further, the content of this Mg is particularly preferably 5.0% by mass or less, and further preferably 3.0% by mass or less. It is particularly preferable that the Mg content is in the range of 1.0 to 3.0% by mass.
  • the Al content in the plating layer is preferably in the range of 25 to 75% by mass.
  • this content is 25% by mass or more, the Zn content in the plating layer does not become excessive, and sufficient corrosion resistance on the surface of the plating layer is ensured.
  • this content is 75% by mass or less, the sacrificial anticorrosion effect of Zn is sufficiently exhibited, the hardening of the plating layer is suppressed, and the bendability of the surface-treated steel material is improved.
  • the Al content is preferably 75% by mass or less.
  • the Al content is particularly preferably 45% by mass or more.
  • the Al content is particularly preferably 65% by mass or less. It is particularly preferable that the Al content is in the range of 45 to 65% by mass.
  • the Si content in the plating layer is preferably in the range of 0.5 to 10% by mass with respect to the Al content.
  • the Si content is particularly preferably 1.0% by mass or more.
  • the Si content is particularly preferably 5.0% by mass or less. It is particularly preferable that the Si content is in the range of 1.0 to 5.0% by mass.
  • the mass ratio of Si: Mg in the plating layer is in the range of 100: 50 to 100: 300. In this case, the formation of the Si—Mg layer in the plating layer is particularly promoted, and the generation of wrinkles in the plating layer is further suppressed.
  • the mass ratio of Si: Mg is preferably 100: 70 to 100: 250, and more preferably 100: 100 to 100: 200.
  • the plating layer contains Cr as a constituent element.
  • Cr promotes the growth of the Si—Mg phase in the plating layer, increases the volume ratio of the Si—Mg phase in the plating layer, and increases the volume ratio of Mg in the Si—Mg phase to the total amount of Mg in the plating layer. The ratio will be high. As a result, wrinkles in the plating layer are further suppressed.
  • the Cr content in the plating layer is in the range of 0.02 to 1.0% by mass. When the Cr content in the plating layer is within the above range, the corrosion resistance of the plating layer can be sufficiently ensured, and wrinkles and sagging of the plating layer can be sufficiently suppressed.
  • the Cr content is preferably 0.05% by mass or more.
  • the Cr content is preferably 0.5% by mass or less.
  • the Cr content is particularly preferably in the range of 0.07 to 0.2% by mass.
  • the Cr content in the outermost layer having a depth of 50 nm in the plating layer is preferably 100 to 500 mass ppm. In this case, the corrosion resistance of the plating layer is further improved. It is considered that this is because the presence of Cr in the outermost layer forms a passivation film in the plating layer, which suppresses the anodic dissolution of the plating layer.
  • the Cr content is preferably 150 to 450 mass ppm, and more preferably 200 to 400 mass ppm.
  • an alloy layer containing Al and Cr is interposed between the plating layer and the steel material.
  • the alloy layer is regarded as a layer different from the plating layer.
  • the alloy layer may contain various metal elements such as Mn, Fe, Co, Ni, Cu, Zn, and Sn as constituent elements in addition to Al and Cr.
  • the presence of such an alloy layer tends to promote the growth of the Si-Mg phase in the plating layer, the volume ratio of the Si-Mg phase in the plating layer increases, and the total amount of Mg in the plating layer is increased.
  • the proportion of Mg in the Si—Mg phase increases. As a result, wrinkles and sagging of the plating layer are further suppressed.
  • the ratio of the Cr content ratio (mass ratio) in the alloy layer to the Cr content ratio (mass ratio) in the plating layer is preferably in the range of 2 to 50.
  • the growth of the Si—Mg phase is promoted in the vicinity of the alloy layer in the plating layer, so that the area ratio of the Si—Mg phase on the surface of the plating layer becomes low, so that sagging is further suppressed.
  • the corrosion resistance of the plating layer is maintained for a longer period of time.
  • the ratio of the Cr content in the alloy layer to the Cr content in the plating layer is preferably 3 to 40, more preferably 4 to 25.
  • the amount of Cr in the alloy layer can be derived by measuring the cross section of the plating layer using an energy dispersive X-ray analyzer (EDS).
  • EDS energy dispersive X-ray analyzer
  • the thickness of the alloy layer is preferably in the range of 0.05 to 5 ⁇ m. When this thickness is 0.05 ⁇ m or more, the above-mentioned action by the alloy layer is effectively exhibited. When this thickness is 5 ⁇ m or less, the workability of the surface-treated steel material is less likely to be impaired by the alloy layer.
  • the corrosion resistance of the plating layer after bending and deformation is also improved.
  • the reason is considered to be as follows.
  • the plating layer is subjected to severe bending deformation, cracks may occur in the plating layer and the coating film on the plating layer. At that time, water and oxygen infiltrate into the plating layer through cracks, and the alloy in the plating layer is directly exposed to the corrosive factor.
  • Cr present in the plating layer, particularly in the surface layer, and Cr present in the alloy layer suppress the corrosion reaction of the plating layer, thereby suppressing the spread of corrosion starting from cracks.
  • the Cr content in the outermost layer having a depth of 50 nm in the plating layer is preferably 300 mass ppm or more, particularly 200 to 400 mass ppm. It is preferably in the range of.
  • the ratio of the Cr content ratio (mass ratio) in the alloy layer to the Cr content ratio (mass ratio) in the plating layer is 20 or more. It is preferably in the range of 20 to 30 in particular.
  • the plating layer preferably further contains Sr as a constituent element.
  • Sr particularly promotes the formation of the Si—Mg layer in the plating layer.
  • Sr suppresses the formation of the Mg-based oxide film on the surface layer of the plating layer. It is considered that this is because the Sr oxide film is more likely to be formed preferentially than the Mg-based oxide film, so that the formation of the Mg-based oxide film is inhibited. As a result, the occurrence of wrinkles in the plating layer is further suppressed.
  • the content of Sr in the plating layer is preferably in the range of 1 mass ppm or more and 1000 mass ppm or less.
  • the content of Sr is particularly preferably 5 mass ppm or more. Further, the content of Sr is particularly preferably 500 mass ppm or less, and further preferably 300 mass ppm or less. The content of Sr is preferably in the range of 20 to 50 mass ppm.
  • the plating layer preferably further contains Fe as a constituent element.
  • Fe particularly promotes the formation of the Si—Mg layer in the plating layer.
  • Fe also contributes to the miniaturization of the microstructure and spangle structure of the plating layer, thereby improving the appearance and workability of the plating layer.
  • the Fe content in the plating layer is preferably in the range of 0.1 to 1.0% by mass. If the Fe content is less than 0.1% by mass, the microstructure and spangle structure of the plating layer become coarse, and the appearance of the plating layer deteriorates and the workability deteriorates.
  • the Fe content is particularly preferably 0.5% by mass or less. It is particularly preferable that the Fe content is in the range of 0.1 to 0.5% by mass.
  • the plating layer may further contain an element selected from alkaline earth elements, Sc, Y, lanthanoid elements, Ti and B as constituent elements.
  • Alkaline earth elements Be, Ca, Ba, Ra
  • Sc Y
  • lanthanoid elements La, Ce, Pr, Nd, Pm, Sm, Eu, etc.
  • the total content of these components in the plating layer is preferably 1.0% by mass or less in terms of mass ratio.
  • the ⁇ -Al phase (dendrite structure) of the plating layer becomes finer and the spangle becomes finer, so that the appearance of the plating layer by the spangle is improved. Further, at least one of Ti and B further suppresses the generation of wrinkles in the plating layer. This is because the Si-Mg phase is also miniaturized by the action of Ti and B, and this miniaturized Si-Mg phase effectively flows the hot-dip galvanized metal in the process of solidifying the hot-dip galvanized metal to form a plating layer. It is thought that this is to suppress it.
  • the total content of Ti and / or B in the hot-dip galvanizing bath 2 is preferably in the range of 0.0005% by mass or more and 0.1% by mass or less in terms of mass ratio. ..
  • the total content of Ti and / or B is particularly preferably 0.001% by mass or more.
  • the total content of Ti and / or B is particularly preferably 0.05% by mass or less. It is particularly preferable that the total content of Ti and / or B is in the range of 0.001 to 0.05% by mass.
  • Zn occupies the balance of all the constituent elements of the plating layer, excluding the constituent elements other than Zn.
  • the plating layer preferably contains the above elements as constituent elements.
  • the plating layer contains only Al, Zn, Si, Mg, Cr, Sr, and Fe as constituent elements, or these elements, as well as alkaline earth elements, Sc, Y, lanthanoid elements, Ti and B. It is preferable that only the element selected from the above is contained as a constituent element.
  • the plating layer may contain unavoidable impurities such as Pb, Cd, Cu, and Mn.
  • the content of the unavoidable impurities is preferably as small as possible, and it is particularly preferable that the total content of the unavoidable impurities is 1% by mass or less in terms of mass ratio with respect to the plating layer.
  • the steel material is immersed in a hot-dip galvanizing bath having a composition that matches the composition of the constituent elements of the plating layer.
  • the hot-dip galvanizing process forms an alloy layer between the steel material and the plating layer, but the resulting variation in composition is negligibly small.
  • a hot-dip plating bath containing ⁇ 1.0% by mass of Fe and Zn is prepared.
  • a hot-dip plating bath containing Sr of about 1000% by mass, Fe of 0.1 to 1.0% by mass, and Zn is prepared.
  • the mass ratio of Si: Mg in the hot-dip galvanizing bath is preferably in the range of 100:50 to 100: 300.
  • Al is 25 to 75% by mass
  • Si is 0.5 to 10% by mass with respect to Al
  • Mg is 0.1 to 0.5% by mass
  • Fe is 0.1 to 0. It can contain 0.6% by mass and Sr in the range of 1 to 500% by mass.
  • Al is 25 to 75% by mass
  • Cr is 0.02 to 1.0% by mass
  • Si is 0.5 to 10% by mass with respect to Al
  • Mg is 0.1 to 0% by mass. It can contain 5% by mass, Fe in the range of 0.1 to 0.6% by mass, and Sr in the range of 1 to 500% by mass.
  • a hot-dip galvanizing bath can be prepared in which a component selected from alkaline earth element, lanthanoid element, Ti and B is further contained and the balance is Zn.
  • Wrinkles are less likely to occur in the plating layer formed by hot-dip galvanizing.
  • Mg molten metal containing Mg
  • Mg-based oxide film is formed. Wrinkles were likely to occur in the plating layer due to the Mg-based oxide film.
  • the hot-dip plating bath having the above composition when used to form the plating layer, the concentration of Mg in the surface layer of the hot-dip galvanized metal adhering to the steel material is suppressed, and the plating layer is formed even if the hot-dip galvanized metal flows. Wrinkles are less likely to occur on the surface of the surface. Further, the fluidity inside the hot-dip galvanized metal is reduced, and the flow itself of the hot-dip galvanized metal is suppressed, so that the wrinkles are less likely to occur.
  • the ⁇ -Al phase In the process of cooling and solidifying the hot-dip galvanized metal adhering to the surface of the steel material, the ⁇ -Al phase first precipitates as primary crystals and grows like dendrites. As the solidification of the Al-rich ⁇ -Al phase progresses in this way, the Mg and Si concentrations in the remaining hot-dip galvanized metal (that is, in the components of the hot-dip galvanized metal that have not yet solidified) gradually increase. Next, when the steel material is cooled and its temperature is further lowered, a Si-containing phase (Si—Mg phase) containing Si is solidified and precipitated from the remaining hot-dip galvanized metal. As described above, this Si—Mg phase is a phase composed of an alloy of Mg and Si.
  • Precipitation / growth of this Si—Mg phase is promoted by Cr, Fe and Sr.
  • Mg in the hot-dip galvanized metal into the Si—Mg phase, the movement of Mg to the surface layer of the hot-dip galvanized metal is hindered, and the concentration of Mg on the surface layer of the hot-dip galvanized metal is suppressed.
  • Sr in the hot-dip galvanized metal also contributes to suppressing the concentration of Mg. This is because Sr is an element that easily oxidizes in hot-dip galvanized metals like Mg, so Sr forms an oxide film on the plating surface competitively with Mg, and as a result, the formation of Mg-based oxide film is suppressed. It is thought that this is because.
  • the Si—Mg phase solidifies and grows in the remaining hot-dip galvanized metal other than the primary crystal ⁇ —Al phase, so that the hot-dip galvanized metal becomes a solid-liquid mixed phase state, and thus the hot-dip galvanized metal itself.
  • the fluidity of the plating layer is reduced, and as a result, the occurrence of wrinkles on the surface of the plating layer is suppressed.
  • Fe is important in controlling the microstructure and spangles of the plating layer. The reason why Fe affects the structure of the plating layer is not always clear at this time, but it is because Fe alloys with Si in the hot-dip galvanized metal and this alloy becomes solid nuclei when the hot-dip galvanized metal solidifies. Conceivable.
  • Sr is a low-key element like Mg
  • the sacrificial anticorrosion action of the plating layer is further strengthened by Sr, and the corrosion resistance of the surface-treated steel material is further improved.
  • Sr also exerts an action of suppressing the needle-like formation of the precipitated form of the Si phase and the Si—Mg phase, so that the Si phase and the Si—Mg phase are spheroidized and the generation of cracks in the plating layer is suppressed.
  • an alloy layer containing a part of Al in the hot-dip galvanized metal is also formed between the plating layer and the steel material.
  • an Fe—Al alloy layer mainly composed of Al in the plating bath and Fe in the steel material is formed.
  • an alloy layer containing Al in the plating bath and some or all of the constituent elements of the pre-plating, or further containing Fe in the steel material is formed.
  • the alloy layer When the plating bath contains Cr, the alloy layer further contains Cr as a constituent element together with Al.
  • the alloy layer contains Si, Mn, Fe, Co, Ni, Cu, Zn, Sn, etc. as constituent elements in addition to Al and Cr, depending on the composition of the plating bath, the presence or absence of pre-plating, the composition of the steel material 1, and the like. It can contain various metal elements.
  • a part of Cr in the hot-dip galvanized metal is contained in the alloy layer at a higher concentration than in the plated layer.
  • Cr in the alloy layer promotes the growth of the Si—Mg phase in the plating layer, increases the volume ratio of the Si—Mg phase in the plating layer, and increases the volume ratio of the Si—Mg phase in the plating layer.
  • the ratio of Mg in the Si—Mg phase to the total amount of Mg in the above increases. As a result, the effect will not be repeated as described above.
  • the thickness of the alloy layer is preferably in the range of 0.05 to 5 ⁇ m. When the thickness of the alloy layer is within the above range, the corrosion resistance of the surface-treated steel material is sufficiently improved, and the workability is also sufficiently improved.
  • the concentration of Cr is maintained in a certain range near the surface thereof, and the corrosion resistance of the plating layer is further improved accordingly.
  • the reason for this is not clear, but it is presumed that Cr combines with oxygen to form a composite oxide film near the surface of the plating layer.
  • the Cr content in the outermost layer having a depth of 50 nm in the plating layer is 100 to 500 mass ppm.
  • the corrosion resistance of the plating layer after bending and deformation is also improved.
  • the reason is considered to be as follows.
  • cracks may occur in the plating layer and the coating film on the plating layer.
  • water and oxygen infiltrate into the plating layer through cracks, and the alloy in the plating layer is directly exposed to the corrosive factor.
  • Cr present in the plating layer, particularly in the surface layer, and Cr present in the alloy layer suppress the corrosion reaction of the plating layer, thereby suppressing the spread of corrosion starting from cracks.
  • the hot-dip galvanized metal treated in the above preferred embodiment is a multidimensional hot-dip metal containing seven or more elements, and its solidification process is extremely complicated and difficult to predict theoretically. Through experimental observations, etc., they came to obtain the above important findings.
  • the hot-dip galvanizing bath contains Ca in particular, the occurrence of dross in the hot-dip galvanizing bath is significantly suppressed.
  • the hot-dip galvanizing bath contains Mg, it is inevitable that some dross will occur even if the Mg content is 10% by mass or less, and plating is required to ensure a good appearance of the surface-treated steel material. It is necessary to remove the dross from the bath, but when the hot-dip galvanizing bath further contains Ca, the generation of dross due to Mg is remarkably suppressed.
  • the Ca content in the hot-dip galvanizing bath is preferably in the range of 50 to 5000 mass ppm. When this content is 50 mass ppm or more, the generation of dross in the hot-dip plating bath is effectively suppressed. If the Ca content is excessive, dross caused by Ca may occur, but if the Ca content is 5000 mass ppm or less, the dross caused by Ca is suppressed. This content is further preferably in the range of 200 to 1000 mass ppm.
  • the wrinkles on the surface of the plating layer are suppressed as described above, so that there are no ridges having a height of more than 200 ⁇ m and a steepness of more than 1.0, particularly on the surface of the plating layer.
  • the steepness is a value defined by (height of the ridge ( ⁇ m)) ⁇ (width of the bottom surface of the ridge ( ⁇ m)).
  • the bottom of the ridge is the intersection of the ridge with a virtual plane that includes the flat surface around the ridge.
  • the height of the ridge is the height from the bottom of the ridge to the tip of the ridge.
  • the ridges are prevented from penetrating the coating film, and the thickness of the coating film can be easily made uniform.
  • the appearance of the surface-treated steel material on which the coating film is formed is improved, and the surface-treated steel material can exhibit further excellent corrosion resistance and the like due to the coating film.
  • hot-dip galvanizing treatment is performed on the steel material using a hot-dip galvanizing bath having the above composition. It can be achieved by applying.
  • the steel material on which the pre-plating layer containing at least one component selected from Cr, Mn, Fe, Co, Ni, Cu, Zn, and Sn is formed is melted for forming the plating layer. It may be plated.
  • a pre-plating layer is formed on the surface of the steel material. This pre-plating layer improves the wettability between the steel material and the hot-dip galvanized metal during the hot-dip galvanizing treatment, and improves the adhesion between the steel material and the plating layer.
  • the pre-plating layer depends on the type of metal constituting the pre-plating layer, but also contributes to further improvement in the surface appearance and corrosion resistance of the plating layer.
  • a Cr-containing pre-plating layer when a Cr-containing pre-plating layer is formed, the formation of a Cr-containing alloy layer is promoted between the steel material and the plating layer, and the corrosion resistance of the surface-treated steel material is further improved.
  • a pre-plating layer containing Fe or Ni is formed, the wettability between the steel material and the hot-dip galvanized metal is improved, the adhesion of the plating layer is greatly improved, and the precipitation of the Si—Mg phase is promoted. The surface appearance of the plating layer is further improved.
  • the promotion of the precipitation of the Si—Mg phase is considered to be caused by the reaction between the pre-plated layer and the hot-dip galvanized metal.
  • the amount of adhesion of the pre-plating layer is not particularly limited, but it is preferable that the amount of adhesion on one side of the steel material is in the range of 0.1 to 3 g / m2. If the amount of adhesion is less than 0.1 g / m2, it is difficult to cover the surface of the steel material with the pre-plating layer, and the improvement effect of the pre-plating is not sufficiently exhibited. If the amount of adhesion exceeds 3 g / m2, not only the improvement effect is saturated but also the manufacturing cost is high.
  • the steel material to be plated is a member made of steel such as carbon steel, alloy steel, stainless steel, nickel chrome steel, nickel chrome molybdenum steel, chrome steel, chrome molybdenum steel, and manganese steel.
  • Examples of the steel material include various members such as thin steel plates, thick steel plates, shaped steels, steel pipes, and steel wires. That is, the shape of the steel material is not particularly limited.
  • the steel material may be flux-treated before the hot-dip galvanizing treatment.
  • This flux treatment the wettability and adhesion of the steel material to the hot-dip galvanizing bath can be improved.
  • the steel material may be subjected to heat annealing / reduction treatment before being immersed in the hot-dip galvanizing bath, or this treatment may be omitted.
  • the steel material may be pre-plated before the hot-dip galvanizing treatment.
  • the gas wiping method can be selected.
  • the type of gas (wiping gas) injected into the steel sheet in the gas wiping method include air, nitrogen, argon, helium, and water vapor. These wiping gases may be preheated and then injected onto the steel sheet.
  • the method for adjusting the amount of plating adhesion is not limited to the gas wiping method, and various methods for controlling the amount of adhesion can be applied.
  • the adhesion amount control method includes the roll drawing method, the method of wiping the hot-dip galvanized metal with a shielding plate, the electromagnetic force wiping method, and the plating adhesion amount using natural gravity drop without applying an external force. The method of adjustment and the like can be mentioned. Two or more types of methods for adjusting the amount of plating adhesion may be combined.
  • the plated steel sheet is cooled by, for example, air cooling, mist cooling, or the like.
  • the hot-dip galvanized metal adhering to the surface of the steel sheet solidifies to form a plating layer.
  • the steel sheet is cooled by the cooling device until the surface temperature of the hot-dip galvanized metal (or the plating layer) becomes 300 ° C. or lower. It is preferable to be done.
  • the surface temperature of the hot-dip galvanized metal is measured with, for example, a radiation thermometer.
  • the cooling rate from when the steel sheet is pulled out from the plating bath until the surface of the hot-dip galvanized metal on the steel sheet is cooled to 300 ° C. is 5 to 100 ° C./ It is preferably in the range of sec.
  • a plurality of cooling devices may be used in combination. In this embodiment, the cooling conditions can be set as appropriate.
  • the cooling rate of the surface of the hot-dip galvanized metal on the steel sheet is preferably 50 ° C./sec or less while the surface temperature of the hot-dip galvanized metal is 500 ° C. or higher.
  • the precipitation of the Si—Mg phase on the surface of the plating layer is particularly suppressed, and thus the occurrence of sagging is suppressed.
  • the reason why the cooling rate in this temperature range affects the precipitation behavior of the Si—Mg phase is not always clear at this time, but if the cooling rate in this temperature range is high, the temperature gradient in the thickness direction of the hot-dip plated metal becomes large.
  • the precipitation of the Mg—Si layer is preferentially promoted on the surface of the hot-dip plated metal having a lower temperature, and as a result, the precipitation amount of the Si—Mg phase on the outermost surface of the plating increases. Be done.
  • the cooling rate in this temperature range is more preferably 40 ° C./sec or less, and particularly preferably 35 ° C./sec or less.
  • the cooled steel sheet is temper-rolled by a temper-rolling / shape-correcting device, and then shape-corrected.
  • the rolling reduction by temper rolling is preferably in the range of 0.3 to 3%.
  • the elongation rate of the steel sheet 1a due to shape correction is preferably 3% or less.
  • the temperature of the hot-dip galvanizing bath in the pot is preferably a temperature higher than the solidification start temperature of the hot-dip galvanizing bath and 40 ° C. higher than the solidification start temperature. It is more preferable that the temperature of the hot-dip galvanizing bath in the pot is higher than the solidification start temperature of the hot-dip galvanizing bath and 25 ° C. higher than the solidification start temperature.
  • the upper limit of the temperature of the hot-dip galvanizing bath is limited in this way, the time required from the steel sheet being pulled out from the hot-dip galvanizing bath until the hot-dip galvanized metal adhering to the steel sheet solidifies is shortened.
  • the time during which the hot-dip galvanized metal adhering to the steel sheet is in a fluid state is shortened, and therefore wrinkles are less likely to occur in the plating layer.
  • the temperature of the hot-dip plating bath is 20 ° C. higher than the solidification start temperature of the hot-dip galvanizing bath, the occurrence of wrinkles in the plating layer is particularly significantly suppressed.
  • the steel sheet When the steel sheet is withdrawn from the hot-dip galvanizing bath, it may be drawn into a non-oxidizing atmosphere or a low-oxidizing atmosphere, and further, the steel sheet is subjected to a gas wiping method in this non-oxidizing atmosphere or a low-oxidizing atmosphere.
  • the amount of hot-dip galvanized metal adhered may be adjusted.
  • the non-oxidizing gas or the low-oxidizing gas means a gas having a low oxygen concentration as compared with the atmosphere.
  • the oxygen concentration of the non-oxidizing gas or the low-oxidizing gas is preferably 1000 ppm or less.
  • the atmosphere filled with the non-oxidizing gas or the low-oxidizing gas is the non-oxidizing atmosphere or the low-oxidizing atmosphere, and the oxidation reaction is suppressed in this atmosphere.
  • the steel sheet drawn out from the hot-dip galvanizing bath is exposed to a non-oxidizing atmosphere or a low-oxidizing atmosphere. Oxidation of the metal is suppressed, and it becomes more difficult for the Mg-based oxide film to be formed on the surface layer of the hot-dip galvanized metal. Therefore, the occurrence of wrinkles in the plating layer is further suppressed.
  • a non-oxidizing gas such as nitrogen gas or a low-oxidizing gas
  • the steel sheet after the hot-dip galvanizing treatment is further subjected to an overaging treatment.
  • the workability of the surface-treated steel material is further improved.
  • the overaging treatment is performed by holding the steel sheet 1a within a certain temperature range for a certain period of time.
  • the steel sheet is transferred from the outside of the heat insulating container to the inside of the heat insulating container, particularly when the temperature of the steel sheet after heating by the heating device is in the range of 180 to 220 ° C., that is, the temperature of the steel sheet is within the above range. Is preferable.
  • the holding time y (hr) of the steel sheet in the heat insulating container preferably satisfies the following formula (1a).
  • T (° C.) in the formula (1a) is the temperature (holding temperature) of the steel sheet 1a during the holding time y (hr), and is the minimum temperature when the temperature of the steel sheet 1a fluctuates.
  • the steel material that has been subjected to the hot-dip galvanizing treatment or further the over-aging treatment is subjected to a chromate-free chemical conversion treatment by superimposing it on the plating layer, and the rust preventive coating composition according to the present disclosure is used on the steel material.
  • the existing coating film is formed.
  • the base layer containing at least an aluminum / zinc alloy plating layer on the surface of the steel material according to the present disclosure and the coating film using the rust preventive coating composition according to the present disclosure can have good adhesion and can have good adhesion for a long period of time. It is possible to obtain a surface-treated steel material that exhibits excellent rust resistance and excellent moisture resistance.
  • the rust-preventive coating composition of the present disclosure is a rust-preventive coating composition containing a coating film-forming resin (A), a cross-linking agent (B), and a magnesium oxide (C).
  • Magnesium oxide (C) has a lattice constant of less than 0.4214 nm and has a lattice constant of less than 0.4214 nm.
  • the BET specific surface area is 2.0 m 2 / g or less.
  • Magnesium oxide (C) has a lattice constant of less than 0.4214 nm and has a lattice constant of less than 0.4214 nm.
  • the BET specific surface area is 2.0 m 2 / g or less.
  • the coating composition according to the present disclosure has, for example, various usage environments, for example, in addition to the effects of the coating composition described above. Even under conditions where the air temperature is high and the environment is humid, there is a tendency for stable rust prevention to be exhibited.
  • the inclusion of the magnesium oxide (C) according to the present disclosure can suppress a significant increase in the amount of alkaline ions dissolved even in an acidic environment. It is presumed to be. As a result, the magnesium oxide (C) according to the present disclosure stably supplies the corrosion suppressing factor, and corrosion can be suppressed for a long period of time.
  • the coating composition according to the present disclosure can exhibit sufficient rust preventive properties even in an acidic environment.
  • the specific magnesium oxide (C) according to the present disclosure can exhibit a function as a rust preventive pigment in the coating composition according to the present disclosure.
  • the magnesium oxide (C) is a rust preventive pigment.
  • the present inventor has found that the coating composition of the present disclosure containing the magnesium oxide (C) according to the present disclosure can significantly reduce water absorption and moisture absorption of the coating film as compared with the coating composition containing a vanadium compound. Found. Therefore, the coating film formed from the rust-preventive coating composition containing the magnesium oxide (C) according to the present disclosure can suppress or greatly reduce the decrease in moisture resistance. In addition, the occurrence of blisters on the coating film can be suppressed or greatly reduced. Further, the rust preventive coating composition according to the present disclosure containing the magnesium oxide (C) according to the present disclosure can suppress or significantly reduce blister in the processed portion, the end face, and the cross-cut portion.
  • the magnesium oxide (C) has a specific relationship according to the present invention, for example, the processed portion, the end face, and the cross-cut portion also exhibit excellent rust resistance for a long period of time, and further, for a long period of time. Furthermore, it can exhibit rust prevention properties over an ultra-long term.
  • the inclusion of the magnesium oxide (C) according to the present disclosure enables good transfer of magnesium ions to the plating layer and is consumed by corrosion. It is presumed that it will be possible to supplement the magnesium in the plated layer. Therefore, the surface-treated steel material of the present disclosure can ensure long-term corrosion resistance.
  • the magnesium oxide (C) in the present disclosure is an oxide having a lattice constant of less than 0.4214 nm and a BET specific surface area of 2.0 m 2 / g or less. It contains at least one selected from the group consisting of tin magnesium oxide (SnMgO), indium magnesium oxide (InMgO) and magnesium oxide (MgO).
  • the magnesium oxide (C) may be magnesium oxide, which is an oxide whose composition is represented by MgO. Since the magnesium oxide (C) is an oxide represented by magnesium oxide (MgO), a coating film exhibiting excellent corrosion resistance can be formed.
  • the magnesium oxide (C) according to the present disclosure has a lattice constant of less than 0.4214 nm, for example, a lattice constant of 0.4213 nm or less. In one embodiment, the magnesium oxide (C) has a lattice constant of less than 0.4212 nm. By having such a lattice constant, it is possible to form a coating film having good rust prevention properties. Further, the magnesium oxide (C) according to the present disclosure may be a cubic crystal. In the present specification, the lattice constant can be measured using, for example, an X-ray diffractometer MAXima_X XRD-7000 (manufactured by Shimadzu Corporation) or the like.
  • the magnesium oxide (C) according to the present disclosure has a lattice constant of 0.4211 nm or less.
  • a lattice constant of 0.4211 nm or less.
  • the magnesium oxide (C) according to the present disclosure has a lattice constant of 0.4200 nm or more, for example, a lattice constant of 0.4205 nm or more, and a lattice constant of 0.4208 nm or more. There may be. In one embodiment, the magnesium oxide (C) according to the present disclosure has a lattice constant of 0.4209 nm or more, for example, a lattice constant of 0.4210 nm or more.
  • the magnesium oxide (C) according to the present disclosure has a BET specific surface area of 2.0 m 2 / g or less. By having the BET specific surface area, it is possible to form a coating film having excellent rust prevention properties for a longer period of time.
  • the BET specific surface area of the magnesium oxide (C) according to the present disclosure is 1.8 m 2 / g or less, for example, 1.6 m 2 / g or less, 1.5 m 2 / g or less. May be.
  • the BET specific surface area of the magnesium oxide (C) may be 1.4 m 2 / g or less, for example 1.3 m 2 / g or less, and 1.1 m 2 / g or less. ..
  • the BET specific surface area can be measured using, for example, an automatic specific surface area measuring device Gemini VII 23900 (manufactured by Shimadzu Corporation). Such an effect should not be construed in a specific theory, but it is more effective that the BET specific surface area of the magnesium oxide (C) is within such a range. It is considered that this is because it is possible to suppress the depletion of the corrosion suppressing factor derived from the magnesium oxide (C) with respect to the portion where corrosion can occur, and it is possible to continuously supply this suppressing factor.
  • the BET specific surface area of the magnesium oxide (C) according to the present disclosure is 0.1 m 2 / g or more, for example, 0.2 m 2 / g or more, and 0.3 m 2 / g or more. May be.
  • a BET specific surface area it is possible to form a coating film having excellent rust prevention properties for a longer period of time. More specifically, a coating film exhibiting rust prevention properties for a long period of time can be formed, and corrosion in an acidic environment can be suppressed or greatly reduced for a long period of time.
  • the BET specific surface area of the magnesium oxide (C) is 0.1 m 2 / g or more and 2.0 m 2 / g or less, for example, 0.3 m 2 / g or more and 1.5 m 2 / g or less. Is.
  • the BET specific surface area of the magnesium oxide (C) can be appropriately combined within the above range.
  • a coating film having excellent rust prevention properties can be formed for a longer period of time. More specifically, a coating film exhibiting rust prevention properties for a long period of time can be formed, and corrosion in an acidic environment can be suppressed or greatly reduced for a long period of time.
  • the magnesium oxide (C) is an oxide having a magnesium metal ion concentration of 70 ppm or less in an aqueous solution obtained by adding 1 g of the magnesium oxide (C) to 100 g of an artificial acidic sea aqueous solution.
  • the magnesium oxide (C) according to the present disclosure has a magnesium metal ion concentration of 69 ppm or less in an aqueous solution prepared by adding 1 g of the magnesium oxide (C) according to the present disclosure to 100 g of an artificial acidic sea aqueous solution.
  • it is an oxide of 66 ppm or less and 65 ppm or less.
  • the magnesium metal ion concentration in the aqueous solution obtained by adding 1 g of the magnesium oxide (C) according to the present disclosure to 100 g of the artificial acidic sea aqueous solution is 10 ppm or more, for example. It is an oxide of 20 ppm or more.
  • the anticorrosive coating composition of the present disclosure is depleted for a long time because the magnesium oxide (C) is a magnesium oxide satisfying such conditions.
  • the corrosion inhibitor from magnesium oxide is supplied to the steel plate, and corrosion can be suppressed.
  • blistering and peeling of the coating film can be satisfactorily suppressed for a long time in a high temperature and high humidity environment.
  • rust-preventive coating composition of the present disclosure blister in the processed portion, the end face, and the cross-cut portion can be suppressed or greatly reduced.
  • "exhibiting rust prevention under high temperature conditions” means that even if the atmospheric temperature is high (for example, 40 ° C. or higher) and the temperature is as high as 80 ° C., it is good. It means to show rust prevention.
  • the magnesium metal ion concentration in an aqueous solution in which 1 g of magnesium oxide (C) is added to 100 g of an artificial acidic sea aqueous solution can be measured based on the JIS G 0594 cycle corrosion test method. More specifically, an aqueous solution based on the acid salt aqueous solution used in Method B defined by the JIS G 0594 cycle corrosion test method can be used as an artificial acidic sea aqueous solution. That is, the pH is adjusted to 2.5 by using a mixture of nitric acid and sulfuric acid specified in Section 4.2.2 of JIS G 0594, assuming that the composition of artificial seawater is close to that specified in JIS G 0594. Artificial acidic seawater can be prepared. For example, a marine art series (manufactured by Tomita Pharmaceutical Co., Ltd.) or the like can be used as the reagent.
  • the value obtained by subtracting a blank from the element concentration (magnesium metal ion concentration) contained in the above supernatant is an aqueous solution obtained by adding 1 g of magnesium oxide (C) to 100 g of an artificial acidic sea aqueous solution. It can be the magnesium metal ion concentration in.
  • the blank a value obtained by measuring the element concentration (magnesium metal ion concentration) of the artificially acidic seawater is used in the same manner as in the supernatant liquid.
  • the magnesium oxide (C) is an oxide having a conductivity of 320 ⁇ S / cm or less in an aqueous solution in which 1 g of magnesium oxide (C) is added to 100 g of pure water, for example, 310 ⁇ S / cm.
  • the magnesium oxide (C) may be an oxide having a conductivity of 305 ⁇ S / cm or less, and may be, for example, an oxide having a conductivity of less than 301 ⁇ S / cm.
  • the corrosion suppressing factor from magnesium oxide is supplied to the steel sheet without being exhausted for a long time, and the corrosion can be suppressed. Further, it is possible to suppress or greatly reduce the deterioration of the moisture resistance of the coating film, and further, it is possible to suppress or greatly reduce the occurrence of blisters on the coating film. Further, with the rust preventive coating composition of the present disclosure, blister in the processed portion, the end face, and the cross-cut portion can be suppressed or greatly reduced.
  • the magnesium oxide (C) is an oxide having a conductivity of 10 ⁇ S / cm or more in an aqueous solution in which 1 g of magnesium oxide (C) is added to 100 g of pure water, for example, 20 ⁇ S / cm. It is the above-mentioned oxide, and is an oxide of 50 ⁇ S / cm or more.
  • the corrosion suppressing factor from magnesium oxide can be more stably supplied to the steel sheet without being depleted for a long time, and the corrosion can be suppressed. Further, it is possible to suppress or greatly reduce the deterioration of the moisture resistance of the coating film, and further, it is possible to suppress or greatly reduce the occurrence of blisters on the coating film. Further, with the rust preventive coating composition of the present disclosure, blister in the processed portion, the end face, and the cross-cut portion can be suppressed or greatly reduced.
  • the magnesium oxide (C) is a fired magnesium product fired at a temperature of 1,000 ° C. or higher. Since the rust-preventive coating composition according to the present disclosure is a magnesium oxide fired under such temperature conditions, it is possible to exhibit excellent rust-preventive properties for a longer period of time, and further to provide excellent moisture resistance.
  • the coating film shown can be formed.
  • the magnesium oxide (C) may be a magnesium calcined product fired at a temperature of 1,100 ° C. or higher, for example, a magnesium calcined product fired at a temperature of 1,200 ° C. or higher. It's okay.
  • the magnesium oxide (C) may be a magnesium calcined product fired at a temperature of 2,200 ° C.
  • the magnesium oxide (C) may be a magnesium calcined product fired at a temperature of 1,000 ° C. or higher and 2,200 ° C. or lower, and fired at a temperature of 1,100 ° C. or higher and 2,000 ° C. or lower. It may be a fired magnesium product. Further, the magnesium oxide (C) may contain a plurality of types of fired products fired in such a temperature range in combination. For example, magnesium oxide (C) can also be produced by a method of oxidizing metallic magnesium.
  • the magnesium oxide (C) of the present disclosure is a magnesium oxide satisfying such a condition, so that the steel plate is not depleted for a long time. Corrosion-suppressing factors from magnesium oxide are supplied, and corrosion can be suppressed. Further, it is possible to suppress or greatly reduce the deterioration of the moisture resistance of the coating film, and further, it is possible to suppress or greatly reduce the occurrence of blisters on the coating film. For example, by satisfying the above conditions, blistering and peeling of the coating film can be satisfactorily suppressed for a long time in a high temperature and high humidity environment. Moreover, with the rust-preventive coating composition of the present disclosure, blister in the processed portion, the end face, and the cross-cut portion can be suppressed or greatly reduced.
  • the magnesium oxide (C) is an oxide having a pH of 8 or more and 13 or less in an aqueous solution in which 1 g of magnesium oxide (C) is added to 100 g of pure water, for example, 9 or more and 13 or less. It may be 10 or more and 13 or less.
  • the pH is 8 or more and 12 or less.
  • ion-exchanged water and 1 g of magnesium oxide (C) are mixed, a stirrer chip is added, and the mixture is stirred at room temperature (23 ° C.) for 4 hours. Then, for example, the pH can be measured using a pH meter (desktop pH meter F-74, manufactured by HORIBA, Ltd.) or the like.
  • the average particle size of the magnesium oxide (C) is 0.5 ⁇ m or more and 20 ⁇ m or less, for example, 1 ⁇ m or more and 15 ⁇ m or less, and 1 ⁇ m or more and 10 ⁇ m or less.
  • the apparent volume concentration (PVC) of magnesium oxide (C) is due to the fact that the average particle size of magnesium oxide (C) is within such a range. It is considered that the excessive increase can be suppressed, and higher corrosion resistance can be exhibited. In addition, it can have excellent coating film blocking properties and can exhibit higher corrosion resistance.
  • the average particle size can be measured using, for example, a laser diffraction type particle size distribution measuring device SALD-2300 (manufactured by Shimadzu Corporation) or the like.
  • SALD-2300 manufactured by Shimadzu Corporation
  • the corrosion of the object to be coated according to the present disclosure is caused by the corrosion factors such as water, salt water, acidic water and the like permeating to the metal side through the coating film.
  • the coating film formed from the coating composition according to the present disclosure can block such corrosive factors from penetrating into the object to be coated.
  • such a blocking property is also referred to as a coating film blocking property.
  • the coating composition of the present disclosure comprises magnesium oxide (C) with respect to a total of 100 parts by mass of the solid content of the coating film-forming resin (A) and the solid content of the cross-linking agent (B). 1. It may be contained in 1 part by mass or more and 150 parts by mass or less, for example, 25 parts by mass or more and 150 parts by mass or less.
  • magnesium oxide (C) in such a relationship, the rust-preventive coating composition of the present invention can exhibit excellent rust-preventive properties over a long period of time, and further, a coating film exhibiting excellent moisture resistance. Can be formed.
  • the coating film-forming resin (A) in the rust-preventive coating composition of the present disclosure is an ester-based urethane resin, and the ester-based urethane resin has a number average molecular weight of 1,000 or more and 40,000 or less and a glass transition point. It is ⁇ 50 ° C. or higher and 70 ° C. or lower, and the solid content acid value is 30 mgKOH / g or lower.
  • the ester-based urethane resin according to the present disclosure is a resin having a functional group capable of reacting with the cross-linking agent (B) and having a coating film-forming ability.
  • the obtained coating film can be provided with a good balance of bending workability, moisture resistance, corrosion resistance and weather resistance.
  • the ester-based urethane resin means a resin having both a urethane group and an ester group in the main chain. Further, a resin in which the number of urethane groups is 5% or more larger than the number of ester groups by comparing the number of urethane groups and the number of ester groups in the main chain is called an ester-based urethane resin.
  • the urethane polymer include those obtained by reacting a polyol compound described later with a polyisocyanate compound and then further chain-extending with a chain extender. For example, it can be obtained by polycondensation of a copolymerized polyester resin having a hydroxyl group and a polyisocyanate compound.
  • the hydroxyl group-containing polyester resin can be obtained by reacting a hydroxyl group-containing polyester resin with an aliphatic diisocyanate compound by a known method.
  • the hydroxyl group-containing polyester resin can be prepared by polycondensing an acid component such as a polycarboxylic acid and / or an acid anhydride with a polyhydric alcohol.
  • the coating film forming resin (A) has a number average molecular weight (Mn) of 1,000 or more and 40,000 or less, the cross-linking reaction with the cross-linking agent (B) described later sufficiently proceeds, and high moisture resistance is achieved. Can form a coating film to have. Further, excellent corrosion resistance can be ensured. For example, although it should not be interpreted only in a specific theory, the elution of magnesium oxide (C) contained in the coating film becomes appropriate, and the corrosion resistance under acidic environmental conditions becomes good. Further, it is possible to prevent the crosslink density of the coating film from becoming too high, and it is possible to form a coating film having a sufficient elongation rate, for example, a coating film having a sufficient bending workability.
  • Mn number average molecular weight
  • the rust preventive coating composition of the present disclosure has an appropriate viscosity and is easy to handle.
  • the number average molecular weight (Mn) is a polystyrene-equivalent value obtained by gel permeation chromatography (GPC).
  • the number average molecular weight (Mn) of the ester-based urethane resin is 1,000 or more and 30,000 or less, for example, 2,000 or more and 28,000 or less, and 2,500 or more and 25,000 or less. May be.
  • the ester-based urethane resin has a number average molecular weight (Mn) of 6,000 or more and 15,000 or less.
  • the term "ester-based urethane resin” simply means that it contains at least one selected from the group consisting of ester-based urethane resins and modified products of ester-based urethane resins. ..
  • the cross-linking reaction with the cross-linking agent (B) proceeds sufficiently, and a coating film having high moisture resistance can be formed. Further, excellent corrosion resistance can be ensured.
  • the elution of magnesium oxide (C) contained in the coating film becomes appropriate, and the corrosion resistance under acidic environmental conditions becomes good. Further, it is possible to prevent the crosslink density of the coating film from becoming too high, and it is possible to form a coating film having a sufficient elongation rate, for example, a coating film having a sufficient bending workability.
  • the rust preventive coating composition of the present disclosure has an appropriate viscosity and is easy to handle.
  • the ester-based urethane resin according to the present disclosure has a glass transition point of ⁇ 50 ° C. or higher and 70 ° C. or lower.
  • the glass transition temperature (Tg) of the urethane resin can be ⁇ 40 ° C. or higher and 60 ° C. or lower, for example, ⁇ 35 ° C. or higher and 55 ° C. or lower, and ⁇ 30 ° C. or higher and 50 ° C. or lower. ..
  • the glass transition temperature (Tg) of the ester-based urethane resin is within the above range, the moisture permeability of the coating film does not become excessively high, the moisture resistance of the coating film becomes sufficient, and the corrosion resistance also becomes good.
  • the glass transition temperature (Tg) can be measured using, for example, a thermal analyzer TMA7100 (manufactured by Hitachi High-Tech Science Co., Ltd.) or the like.
  • the solid acid value of the ester-based urethane resin is 30 mgKOH / g or less.
  • the solid content acid value is in such a range, for example, hydrolysis resistance can be improved and a coating film having moisture resistance can be formed. In addition, excellent corrosion resistance can be ensured.
  • the solid acid value can be measured in accordance with the provisions of JIS K 0070.
  • the solid acid value of the ester-based urethane resin is 0.1 mgKOH / g or more and 30 mgKOH / g or less, for example, 0.1 mgKOH / g or more and 30 mgKOH / g or less, and 0.3 mgKOH / g or more. It may be 30 mgKOH / g or less.
  • the solid content acid value is in such a range, hydrolysis resistance can be improved and a coating film having moisture resistance can be formed. In addition, excellent corrosion resistance can be ensured.
  • the urethane group concentration (mass%) in the ester-based urethane resin is 2% by mass or more and 20% by mass or less, for example, 5% by mass or more and 17% by mass or less.
  • the urethane group concentration in the urethane resin is within such a range, excellent moisture resistance and corrosion resistance can be ensured.
  • urethane resin examples include those obtained by reacting a polyol compound with a polyisocyanate compound and then further chain-extending with a chain extender.
  • the polyol compound is not particularly limited as long as it is a compound containing two or more hydroxyl groups per molecule, and for example, ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, and trimethylolpropylene glycol.
  • the polyisocyanate compound is not particularly limited as long as it is a compound containing two or more isocyanate groups per molecule, and for example, an aliphatic isocyanate such as hexamethylene diisocyanate (HDI) and a fat such as isophorone diisocyanate (IPDI).
  • HDI hexamethylene diisocyanate
  • IPDI isophorone diisocyanate
  • aromatic diisocyanates such as cyclic diisocyanate and tolylene diisocyanate (TDI)
  • aromatic aliphatic diisocyanates such as diphenylmethane diisocyanate (MDI)
  • MDI diphenylmethane diisocyanate
  • the chain extender is not particularly limited as long as it is a compound containing one or more active hydrogens in the molecule, and water or an amine compound can be applied.
  • amine compound examples include aliphatic polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine and tetraethylenepentamine, and aromatic polyamines such as tolylene diamine, xylylene diamine and diaminodiphenylmethane.
  • aliphatic polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine and tetraethylenepentamine
  • aromatic polyamines such as tolylene diamine, xylylene diamine and diaminodiphenylmethane.
  • Alicyclic polyamines such as diaminocyclohexylmethane, piperazine, 2,5-dimethylpiperazine, isophoronediamine, hydrazines such as hydrazine, dihydrazide succinate, dihydrazide adipate, dihydrazide phthalate, hydroxyethyldiethylenetriamine, 2- [(2-Aminoethyl) amino] alkanolamines such as ethanol and 3-aminopropanediol can be mentioned.
  • polycarboxylic acid constituting the copolymerized polyester resin having a hydroxyl group examples include aliphatic polycarboxylic acids such as oxalic acid, succinic acid, adipic acid, and azelaic acid, terephthalic acid, isophthalic acid, orthophthalic acid, and 4,4'-diphenyldicarboxylic acid.
  • Aromatic polycarboxylic acids such as acids and trimellitic acids, as polyol components, ethylene glycol, propylene glycol, trimethylene glycol, 1,3-butadiol, 1.4-butadiol, 1.5-bentandiol, 1.6- Examples thereof include hexanediol, neopentyl glycol, trimethylolpropane, trimethylolethane, and pentaerythritol.
  • the copolymerized polyester of the present invention contains an excess of hydroxyl groups in the range of 1.0 / 1.001 to 1.0 / 2.0 in the equivalent ratio of the carbonyl group in the polycarboxylic acid and the hydroxyl group of the polyol component. Preferably, it is obtained by a usual transesterification method or a direct esterification reaction. A particularly preferable equivalent ratio is in the range of 1.0 / 1.01 to 1.0 / 1.5.
  • the acid anhydride that can be contained in the acid component is not particularly limited, and is, for example, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, succinic anhydride, trimellitic anhydride. Examples thereof include acid, phthalic anhydride, maleic anhydride, succinic anhydride, dodecenyl succinic anhydride and the like.
  • reaction components may be used in addition to the acid component and the polyol component.
  • reaction components include monocarboxylic acids, hydroxycarboxylic acids, lactones, drying oils, semi-drying oils, and fatty acids thereof. More specifically, examples thereof include monoepoxyside compounds such as Cardura E (manufactured by Shell Chemical Co., Ltd.) and lactones. The above lactones can be ring-opened and added to polyesters of polyhydric carboxylic acid and polyhydric alcohol to form a graft chain.
  • ⁇ -propiolaclone, dimethylpropiolactone, butyllactone, ⁇ - examples thereof include valerolactone, ⁇ -caprolactone, ⁇ -caprolactone, ⁇ -caprolactone, crotolactone, ⁇ -valerolactone, and ⁇ -caprolactone. Of these, ⁇ -caprolactone is the most preferable.
  • the coating composition of the present disclosure may contain the following resins in addition to the coating film forming resin (A).
  • resins for example, epoxy resin and its modified product (acrylic modified epoxy resin, etc.); polyester resin and its modified product (urethane modified polyester resin, epoxy modified polyester resin, silicone modified polyester resin, etc.); acrylic resin and its modified product (silicone modified acrylic) Resin, etc.); Urethane resin and its modified products (ether-based urethane resin, carbonate-based urethane resin, epoxy-based urethane resin, etc.); Phenolic resin and its modified products (acrylic-modified phenol resin, epoxy-modified phenol resin, etc.); Phenoxy resin; Epoxy resins and modified products thereof (urethane-modified epoxy resins, acrylic-modified epoxy resins, etc.); resins such as fluorine resins can be mentioned. Only one of these resins may be used alone, or two or more of these resins may be used in combination. Further, it may be contained within a range that does not impair the
  • thermoplastic resin can be used.
  • the thermoplastic resin include chlorinated olefin resins such as chlorinated polyethylene and chlorinated polypropylene; homopolymers or copolymers containing vinyl chloride, vinyl acetate, vinylidene chloride and the like as monomer components; cellulose resins; acetal resins. Alexandre resin; Rubber chloride resin; Modified polypropylene resin (acid anhydride-modified polypropylene resin, etc.); Fluororesin (for example, vinylidene fluoride resin, vinyl fluoride resin, copolymer of fluorinated olefin and vinyl ether, fluorinated A copolymer of an olefin and a vinyl ester) and the like. Only one type of thermoplastic resin may be used alone, or two or more types may be used in combination. By using the thermoplastic resin in combination, better coating film physical characteristics such as coating film strength and elongation can be obtained.
  • Cross-linking agent (B) reacts with the coating film-forming resin (A) to form a cured coating film.
  • the cross-linking agent (B) include a polyisocyanate compound; a blocked polyisocyanate compound in which the isocyanate group of the polyisocyanate compound is blocked with an active hydrogen-containing compound (sometimes referred to as “BI”); an amino resin; a phenol resin, and the like. Can be done. Among these, it is preferable to contain one or more selected from the blocked polyisocyanate compound and the amino resin.
  • the polyisocyanate compound and the polyisocyanate compound constituting the block polyisocyanate compound are not particularly limited, and conventionally known ones can be used. Specific examples include, for example, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, cyclohexane-1,3- or 1,4-diisocyanate, 1-isocyanato-3.
  • IPDI isophorone diisocyanate
  • MDI dicyclohexylmethane-4,4'-diisocyanate
  • a cyclized polymer of each diisocyanate (isocyanurate type), an isocyanate / biuret type (biuret type), or an adduct type may be used. Only one type of polyisocyanate compound may be used alone, or two or more types may be used in combination.
  • the isocyanurate-type polyisocyanate compound is one of those preferably used in the present invention.
  • the polyisocyanate compound it is preferable to use an aromatic polyisocyanate compound containing one or more aromatic functional groups in the molecule.
  • aromatic polyisocyanate compound By using the aromatic polyisocyanate compound, the moisture resistance of the coating film can be improved and the strength of the coating film can be improved.
  • Preferred aromatic polyisocyanate compounds include 2,4- or 2,6-diisocyanatotoluene (TDI), 2,2'-, 2,4'-or 4,4'-diisocyanatodiphenylmethane ( MDI), xylene diisocyanate (XDI), naphthalene diisocyanate (NDI) and the like can be mentioned.
  • the isocyanate group content of the polyisocyanate compound constituting the blocked polyisocyanate compound as measured in accordance with JIS K7301-1995 is usually 3 to 20%, preferably 5 to 5% of the solid content of the polyisocyanate compound. It is 15%.
  • the isocyanate group content is within the above range, the curability of the coating film is further improved. In addition, it is possible to suppress an excessively high crosslink density of the obtained coating film, and the corrosion resistance can be improved.
  • Specific examples include, for example, phenol, cresol, xylenol, ⁇ -caprolactam, ⁇ -valerolactam, ⁇ -butyrolactam, methanol, ethanol, n-, i-, or t-butyl alcohol, ethylene glycol monoethyl ether, ethylene.
  • Glycol monobutyl ether diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, formamide oxime, acetoaldoxime, acetoxime, methyl ethyl kedoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime, dimethyl malonate, ethyl acetoacetate, acetyl acetone , Pyrazole, etc.
  • the active hydrogen-containing compound only one kind may be used alone, or two or more kinds may be used in combination.
  • the thermal dissociation temperature of the blocked polyisocyanate compound depends on the type of the polyisocyanate compound and the active hydrogen-containing compound constituting the blocked polyisocyanate compound, the presence or absence of a catalyst, and the amount thereof. ) Is 120 to 180 ° C., a blocked polyisocyanate compound is preferably used. By using a block polyisocyanate compound showing a dissociation temperature within this range, the stability of the coating material can be improved, and since it is excellent in the cross-linking reactivity with the coating film-forming resin (A), it has moisture resistance. Can obtain a good coating film.
  • Examples of the blocked polyisocyanate compound (e) having a dissociation temperature of 120 to 180 ° C. include Death Module BL3175 manufactured by Sumika Covestro Urethane Co., Ltd. and Coronate 2554 manufactured by Tosoh Co., Ltd. In the present specification, the blocked polyisocyanate compound may be referred to as (BI).
  • the amino resin examples include melamine resin and urea resin, and among them, melamine resin is preferably used.
  • Melamine resin generally means a thermosetting resin synthesized from melamine and aldehyde, and has three reactive functional groups-NX 1 X 2 in one molecule of triazine nucleus.
  • the melamine resin is a fully alkyl type containing -N- (CH 2 OR) 2 [R is an alkyl group, the same applies hereinafter] as a reactive functional group; -N- (CH 2 OR) (CH 2) as a reactive functional group.
  • Methylol group containing OH Methylol group containing OH
  • imino group containing -N- (CH 2 OR) (H) as reactive functional group
  • -N- (CH 2 OR) (CH 2 OH) reactive functional group
  • methylol / imino group types containing -N- (CH 2 OR) (H) or containing -N- (CH 2 OH) (H) can be exemplified.
  • a melamine resin having at least one methylol group or imino group on average in one molecule hereinafter referred to as amino resin (f)
  • amino resin (f) a melamine resin having at least one methylol group or imino group on average in one molecule
  • a mold or methylol / imino-based melamine resin or a mixture thereof is preferable to use a mold or methylol / imino-based melamine resin or a mixture thereof.
  • the melamine resin for example, the trade name Mycoat 715 manufactured by Ornex Japan Co., Ltd. can be mentioned.
  • Amino resins such as melamine resins have excellent cross-linking reactivity with the coating film-forming resin (A) even under no catalyst, and a coating film having good moisture resistance can be obtained.
  • the melamine resin may be referred to as (MF).
  • the amount of the cross-linking agent (B) according to the present invention is 1 part by mass or more and 150 parts by mass or less in terms of solid content with respect to 100 parts by mass of solid content of the coating film forming resin (A), for example, 2 parts by mass or more. It is 100 parts by mass or less.
  • the amount of the cross-linking agent (B) is 5 parts by mass or more and 95 parts by mass or less in terms of solid content with respect to 100 parts by mass of the solid content of the coating film forming resin (A).
  • the cross-linking reaction with the coating film-forming resin (A) proceeds more satisfactorily, the moisture permeability of the coating film becomes better, and the moisture resistance of the coating film becomes further improved. It will be good. Moreover, the corrosion resistance is further improved. Further, the magnesium oxide (C) contained in the coating film can be stably eluted for a long period of time, and further excellent corrosion resistance can be obtained.
  • the coating composition of the present invention may further contain at least one extender pigment selected from the group consisting of calcium carbonate, barium sulfate, clay, talc, mica and silica.
  • extender pigment selected from the group consisting of calcium carbonate, barium sulfate, clay, talc, mica and silica.
  • the amount of the extender pigment is 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the total solid content of the coating film forming resin (A) and the cross-linking agent (B), for example, 10 parts by mass. More than 30 parts by mass or less.
  • the amount of the extender pigment is within such a range, the moisture resistance can be improved. Further, it is possible to suppress the excessively high moisture permeability of the coating film, for example, it is possible to suppress the excessive infiltration of water into the coating film, and it is possible to improve the moisture resistance of the coating film.
  • the coating composition of the present disclosure may further contain at least one coupling agent selected from the group consisting of silane-based coupling agents, titanium-based coupling agents and zirconium-based coupling agents.
  • the coupling agent By adding the coupling agent, the adhesion between the base material (object to be coated) and the coating film formed from the coating composition according to the present disclosure can be further improved, and the moisture resistance of the coating film can be further improved. Can be done.
  • the coupling agent is not particularly limited, and conventionally known ones can be used.
  • Specific examples of the coupling agents preferably used are silane coupling agents such as Z-6011 and Z-6040 manufactured by Dow Corning Toray Co., Ltd .; titanium such as Organix TC-401 and Organix TC-750 manufactured by Matsumoto Fine Chemicals.
  • Coupling agents examples thereof include zirconium-based coupling agents such as Organix ZC-580 and Organix ZC-700 manufactured by Matsumoto Fine Chemicals. Of these, silane-based coupling agents are preferably used.
  • the amount of the coupling agent may be 0.1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total solid content of the coating film-forming resin (A) and the cross-linking agent (B), for example, 0. It may be 0.5 parts by mass or more and 10 parts by mass or less. When the amount of the coupling agent is within such a range, the moisture resistance can be improved and the storage stability of the coating composition can be well maintained.
  • the coating composition of the present invention may contain a curing catalyst.
  • the curing catalyst include tin catalysts, amine catalysts, lead catalysts and the like, and among them, organotin compounds are preferably used.
  • organotin compounds are preferably used as the organic tin compound.
  • the organic tin compound for example, dibutyltin dilaurate (DBTL), dibutyltin oxide, tetra-n-butyl-1,3-diacetoxystanoxane and the like can be used.
  • the amount of the curing catalyst may be 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the total solid content of the coating film forming resin (A) and the cross-linking agent (B). It may be 1 part by mass or more and 1.0 part by mass or less. When the amount of the curing catalyst is within such a range, for example, the storage stability of the coating composition can be well maintained.
  • the coating composition of the present invention may contain a curing catalyst.
  • the curing catalyst in this case include acid catalysts such as carboxylic acid and sulfonic acid, and among them, dodecylbenzenesulfonic acid, paratoluenesulfonic acid and the like are preferably used.
  • the content of the curing catalyst is 0. It may be 1 part by mass or more and 1.0 part by mass or less. When the amount of the curing catalyst is within such a range, for example, the storage stability of the coating composition can be well maintained.
  • the coating composition of the present disclosure may contain other additives other than the above, if necessary.
  • other additives include rust-preventive pigments other than the magnesium oxide (C) according to the present disclosure; extender pigments other than the above-mentioned extender pigments; colorants such as color pigments and dyes; bright pigments; solvents; ultraviolet absorption.
  • Agents (benzophenone-based UV absorbers, etc.); Antioxidants (phenol-based, sulfoid-based, hindered amine-based antioxidants, etc.); Plastic agents; Surface conditioners (silicone, organic polymers, etc.); Anti-sagging agents; Thickeners Lubricant such as wax; Pigment dispersant; Pigment wetting agent; Leveling agent; Color-coding inhibitor; Anti-precipitation agent; Antifoaming agent; Antiseptic agent; Antifreeze agent; Emulsifier; Antifungal agent; Antibacterial agent; Stabilizer, etc. is there. These additives may be used alone or in combination of two or more.
  • a non-chromium-based rust preventive pigment can be further used as long as the effects produced by the present disclosure are not impaired.
  • molybdate pigments zinc molybdate, strontium molybdate, etc.
  • molybdate pigments aluminum molybdate pigments, etc.
  • calcium silica-based pigments calcium silica-based pigments
  • phosphate-based rust preventive pigments silicate-based anticorrosives.
  • Examples thereof include rust pigments, havanazinate-based rust preventive pigments, calcium hydroxide, magnesium hydroxide, and non-chromium-based rust preventive pigments such as hydroxides or oxides of the second element such as magnesium oxide other than this claim. These may be used alone or in combination of two or more. Since the coating composition of the present invention contains a predetermined magnesium oxide (C), it exhibits sufficiently high corrosion resistance, but if necessary, a rust preventive pigment other than the magnesium oxide (C) as described above is further added. Can include.
  • pigments other than the above-mentioned extender pigments alumina, bentonite, etc. may be added as long as the moisture resistance, rust prevention, bending workability, etc. of the obtained coating film are not impaired. These may be used alone or in combination of two or more.
  • Colored pigments include, for example, colored inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, and cold dust; phthalocyanine blue, phthalocyanine green, quinacridone, perylene, anthrapyrimidine, carbazole violet, anthrapyridine, azoorange, and flavanthron yellow. , Isoindoline Yellow, Azo Yellow, Induslon Blue, Dibrom Anzaslon Red, Perylene Red, Azo Red, Anthraquinone Red, etc. Colored Organic Pigments; Aluminum Powder, Alumina Powder, Bronze Powder, Copper Powder, Tin Powder, Zinc Powder, Phosphorus Examples thereof include iron oxide and atomized titanium. These may be used alone or in combination of two or more.
  • colored inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, and cold dust
  • phthalocyanine blue phthalocyanine green
  • quinacridone perylene
  • anthrapyrimidine carbazo
  • glitter pigment examples include aluminum foil, bronze foil, tin foil, gold leaf, silver foil, titanium metal foil, stainless steel foil, alloy foil such as nickel and copper, and foil pigment such as foil-like phthalocyanine blue. .. These may be used alone or in combination of two or more.
  • the solvent examples include water; ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and the like.
  • Glycol-based organic solvents such as dipropylene glycol monoethyl ether and propylene glycol monomethyl ether acetate; alcohol-based organic solvents such as methanol, ethanol and isopropyl alcohol; ether-based organic solvents such as dioxane and tetrahydrofuran; 3-methoxybutyl acetate and ethyl acetate , Ester organic solvents such as isopropyl acetate, butyl acetate; ketone organic solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, isophorone; and N-methyl-2-pyrrolidone, toluene, pentane, iso-pentane, hexane.
  • alcohol-based organic solvents such as methanol, ethanol and isopropyl alcohol
  • ether-based organic solvents such as dioxane and te
  • the coating composition of the present invention may be a water-based coating material or an organic solvent-based coating material.
  • the method for preparing the coating composition according to the present disclosure is not particularly limited.
  • the coating composition according to the present disclosure includes, for example, a coating film-forming resin (A), a cross-linking agent (B) and a magnesium oxide (C), and optionally used thermoplastic resins, extender pigments, coupling agents, and the like.
  • the curing catalyst and other additives can be prepared by mixing using a mixer such as a roller mill, a ball mill, a bead mill, a pebble mill, a sand grind mill, a pot mill, a paint shaker, or a disper.
  • the coating composition of the present disclosure is a two-component coating material comprising a main agent component containing a coating film-forming resin (A) and a magnesium oxide (C) and a cross-linking agent component containing a cross-linking agent (B). You may.
  • the coating composition of the present invention may be applied as an undercoat coating, which is also called a primer. Further, it may be used as a top coat paint to be overlaid on the base coat paint. Further, it may be an intermediate coating paint formed in an intermediate layer between the undercoat coating and the topcoat coating. Alternatively, the coating composition of the present invention may be used as a coating composition for forming a single-layer coating film, not for forming a multi-layer coating film. The coating composition of the present invention can exhibit excellent corrosion resistance and moisture resistance when used on any portion of the multi-layer coating film. Above all, the coating composition of the present invention is preferably used as an undercoat coating material.
  • Undercoat paints, topcoat paints and intermediate coat paints other than the coating composition of the present invention may be conventionally known, and examples of the undercoat paint include conventionally known non-chromium-based rust preventive paints and the like.
  • Examples of the intermediate coating paint include polyester resin-based paints and fluororesin-based paints.
  • the coating film composed of the coating composition of the present invention can be formed by applying the coating composition to an object to be coated such as a steel plate and then performing a baking treatment for heating the object to be coated.
  • the baking temperature (the maximum temperature reached by an object to be coated such as a steel plate) is, for example, 150 ° C. or higher and 270 ° C. or lower, and by curing the coating composition according to the present disclosure at such a temperature, sufficient strength is obtained.
  • a coating film can be formed.
  • the baking time is, for example, 10 to 200 seconds.
  • the undercoat coating composition is applied and then baked, and then the topcoat coating composition is applied and the topcoat coating film is baked. After applying the undercoat coating composition, the topcoat coating composition may be applied wet-on-wet without baking, and then baked at the same time.
  • the film thickness (dry film thickness) of the coating film (hereinafter referred to as the coating film of the present invention) obtained by using the coating composition of the present invention is usually 1 to 30 ⁇ m. It is preferably 10 to 30 ⁇ m.
  • the coating film formed from the coating composition of the present disclosure can show good results in both “immersion in acidic salt water-drying cycle test 15 cycles” and "CCHC test 2,000 hours", for example. Since good results can be shown in these tests, it is possible to achieve both long-term stable rust prevention and moisture resistance.
  • the "immersion-drying cycle test with acidic salt water” can be measured based on the method shown in Japanese Patent No. 5857156. It is considered that a coating film having rust preventive properties and stable rust preventive properties for a long period of time can be obtained, for example, by giving good test results.
  • CCHC test 2,000 hours is performed by exposing the coating film to a high temperature and high humidity environment called CCHC (Cleveland Condensing Humidity Cabinet: ASTM D-2247-87-Type A2) for 2,000 hours. This is an evaluation test for coating film blisters to be evaluated. Further, by setting the test time to 2,000 hours, it is considered that the coating film according to the present disclosure can maintain excellent moisture resistance for a long period of time even if the coating film is exposed to a harsher environment.
  • the coating composition according to the present disclosure can show excellent results in such a plurality of tests, and can form a coating film having both long-term stable rust prevention and moisture resistance.
  • the rust prevention property under acidic environmental conditions can be evaluated based on a test using "acidic salt water”. Further, in the present disclosure, a coating film having excellent rust prevention properties under acidic environmental conditions can be obtained, and for example, excellent rust prevention properties against acid rain can be exhibited.
  • the materials, ingredients, etc. used to prepare the paint composition are as follows.
  • a base layer including an aluminum-zinc alloy plating layer was formed by immersing a steel material (manufactured by Nippon Steel Co., Ltd.) in a hot-dip metal, and hot-dip galvanized steel materials 1 to 6 were prepared. At this time, the components of the molten metal were adjusted so that the amount of each constituent element in the plating layer was the amount (mass%) shown in Table 1. Further, zinc (Zn) is described as “ ⁇ ” when it is present in the plating layer.
  • coating film forming resin (A1) (ester urethane resin 1)
  • A1 ester urethane resin 1
  • 55 parts by mass of adipic acid, 6.1 parts by mass of phthalic anhydride, 27 parts by mass of neopentyl glycol and 26.1 parts by mass of propylene glycol were mixed in a reaction vessel equipped with a thermometer, a condenser and a stirrer, and in a nitrogen stream. The temperature was gradually raised to 230 ° C., and the esterification reaction was carried out while distilling off the generated water.
  • Coating film forming resins (A2) to (A8) (ester urethane resins 2 to 8, respectively) were prepared in the same manner as above, except that the monomer type and amount were changed as shown in Table 3A.
  • Table 3A shows various special values such as monomer composition and molecular weight of each resin.
  • Solid content concentration 50% -Coating resin (A13) (acrylic resin 1); Acrydic A452 (manufactured by DIC) Number average molecular weight: 17,000, solid content Acid value: 2.7 mgKOH / g, glass transition temperature: 70 ° C., solid content Concentration: 40% by mass Coating film forming resin (A14) (acrylic resin 2); Acridic A607-60 (manufactured by DIC) Number average molecular weight 3,800, solid acid value: 1.0 mgKOH / g, glass transition temperature: 30 ° C., solid Mineral concentration: 60% by mass
  • Cross-linking agent (B1) polyisocyanate compound 1
  • Death module BL3575 blocked polyisocyanate manufactured by Sumika Cobestrourethane
  • Hexamethylene diisocyanate (HDI) block isocyanurate type, blocking agent: dimethylpyrazole
  • Isocyanate group content 10.5% by mass
  • solid content concentration 75% by mass -Crosslinking agent (B2) (amino resin)
  • Mycoat 715 manufactured by Ornex Japan, imino-based melamine resin
  • Mycoat 715 manufactured by Ornex Japan, imino-based melamine resin
  • Mycoat 715 manufactured by Ornex Japan, imino-based melamine resin
  • Solvent 1 Cyclohexanone (manufactured by Shoei Chemical Industry Co., Ltd.)
  • Solvent 2 Solvento 150 (manufactured by Shell Chemical Co., Ltd.) -Curing catalyst; KS-1260 (manufactured by Kyodo Yakuhin Co., Ltd., dibutyltin dilaurate)
  • Non-volatile content 100% by mass
  • Example 1 142.9 parts by mass of the coating film forming resin (A1), 45.0 parts by mass of cyclohexanone, 45.0 parts by mass of Solbesso 150 and 60 parts by mass of magnesium oxide (C1) are mixed and sand milled (dispersion medium: glass beads). To prepare a dispersion composition 1 by dispersing until the maximum particle size of the coarse pigment particles was 10 ⁇ m or less.
  • dispersion composition 18.1 parts by mass of Death Module BL-3575 (manufactured by Sumika Cobestro Urethane Co., Ltd.) as a cross-linking agent (B1) and 0.5 mass by mass of KS1260 (manufactured by Kyodo Yakuhin Co., Ltd.) as a curing catalyst. Parts were added and mixed uniformly with a disper to prepare a coating composition 1. Details of the composition according to Example 1 are shown in Table 4A.
  • Examples 2 to 25, Comparative Examples 1 to 16 various physical property evaluations were carried out using the coated steel sheet thus formed.
  • a coating film was formed in the same manner in the other examples and comparative examples.
  • a coating composition was prepared in the same manner as in Example 1 except that the type and amount of each component were changed as described in Tables 4A to 4E (Examples) and Tables 6A and 6B (Comparative Examples). , A coated steel sheet for evaluation was obtained.
  • Examples 2 to 25, Comparative Examples 1 to 16 the coating composition of any of Examples 1 to 25 and Comparative Examples 1 to 16 is applied to the surface of the steel sheet so that the dry coating film has a thickness of 5 ⁇ m, and baked at a maximum temperature of 200 ° C. for 30 seconds. Was carried out to form a surface undercoat coating film.
  • Nippe Super Coat 300HQ manufactured by Nippon Paint Industrial Coatings
  • Nippe Super Coat 300HQ which is a polyester-based topcoat paint
  • Baking was performed for 2 seconds to form a surface topcoat film, and a coated steel sheet for evaluation was obtained.
  • Reference Example 1 Regarding Reference Example 1, instead of the phosphoric acid treatment agent (Surfcoat EC2310), NRC300 (manufactured by Nippon Paint Surf Chemicals Co., Ltd.), which is a chromate treatment agent, is applied to the front and back surfaces of the steel plate, chromate treatment is applied, and chromium is applied.
  • NRC300 manufactured by Nippon Paint Surf Chemicals Co., Ltd.
  • Nippe Supercoat 667 Primer which is an undercoat paint containing strontium acid acid
  • Nippe Supercoat 300HQ manufactured by Nippon Paint Industrial Coatings
  • the value obtained by subtracting the magnesium metal ion concentration contained in the artificially acidic seawater from the magnesium metal ion concentration contained in the supernatant liquid is the magnesium metal ion in the aqueous solution obtained by adding 1 g of magnesium oxide (C) to 100 g of the artificially acidic seawater solution. It was defined as the concentration.
  • Evaluation items 1 Boiling water resistance test The coated steel sheet obtained above is cut into 5 cm x 10 cm, and the obtained test piece is immersed in boiling water at about 100 ° C. for 2 hours and then pulled up to give the appearance of the coating film on the surface side.
  • ATM D714-56 evaluation of flat surface blisters.
  • ASTM D714-56 evaluates the size (mean diameter) and density of each blister in comparison with a standard photo finish, and indicates a grade symbol.
  • the size is 8 (diameter about 1 mm), 6 (diameter about 2 mm), 4 (diameter about 3 mm), 2 (diameter about 5 mm) in this order, and the density is F, FM, M, MD from the smallest.
  • D is classified into 5 stages, and if there is no blistering, it is set to 10. A score of 8 FM or higher was evaluated as good.
  • the coated steel sheet test piece after being immersed in boiling water at about 100 ° C. for 2 hours was evaluated by performing a grid tape adhesion test (grid adhesion test).
  • grid tape adhesion test according to the JIS K 5400 8.5.2 (1990) grid tape method, the gap between the cuts is set to 1 mm, 100 grids are made, and cellophane adhesive tape is adhered to the surface. , The number of grids remaining on the coated surface when peeled off rapidly was investigated.
  • the 4T bending process is a process in which the surface of the coated plate is turned to the outside, four plates of the same thickness as the coated plate are sandwiched inside, and the coated plate is bent 180 degrees by a vise. After processing, the four plates are removed and used for the test.
  • FIG. 1A is a diagram schematically showing a cross section 20 of an upper burr and a cross section 30 of a lower burr in the obtained coated steel sheet test piece 10. Further, the coated steel sheet test piece 10 has a coating film front surface 11 and a coating film back surface 12.
  • FIG. 1B is a schematic view showing a cross-cut portion 40 and a 4T bent portion 50 provided on the coated steel sheet test piece 10 used in the corrosion resistance test. Further, the coated steel sheet test piece 10 has an upper burr 21 and a lower burr 31.
  • Each of the obtained coated steel sheet test pieces was subjected to a composite cycle corrosion test (CCT) according to JIS K 5600-7-9A JASO M609. 120 cycle test (total 960) with (2 hours of 5% saline spray at 35 ° C)-(4 hours of drying at 60 ° C)-(2 hours of standing in a moisture resistance tester with RH of 95% or more at 50 ° C) as one cycle. Time) was done. The state of the edge portion, the cross cut portion and the 4T bent portion of the coated steel sheet test piece after this test was evaluated based on the following evaluation method and evaluation criteria. In each case, a score of 4 or higher was evaluated as good.
  • Equipment used Composite cycle tester CYP-90 (manufactured by Suga Test Instruments Co., Ltd.)
  • the corrosion state of the cross-cut part was evaluated by the following criteria based on the ratio of the length of white rust generated in the exposed part of the substrate with a cut width of 0.5 mm and the average value of the left and right blisters width (sum of both sides) of the cross-cut part. .. 5: The ratio of the length of white rust generated in the exposed portion of the substrate is less than 25%, and the blistering width is less than 3 mm. 4: White rust generation length ratio of 25% or more and less than 50% in the exposed portion of the substrate, and a blistering width of less than 3 mm. 3: White rust generation length ratio of 50% or more and blister width less than 3 mm in the exposed part of the substrate.
  • the acid salt aqueous solution used in Method B defined by the JIS G 0594 cycle corrosion test method was referred to. That is, using Marine Art SF-1 (manufactured by Tomita Pharmaceutical Co., Ltd.) as a composition similar to the artificial seawater specified in JIS G 0594, and using a mixed solution of nitric acid and sulfuric acid specified in Section 4.2.2. The pH was adjusted to 2.5 to obtain acidic salt water.
  • Test condition Each of the obtained coated steel sheet test pieces was subjected to a 15-cycle test (360 hours in total) under the condition of 23 ° C. with 6 hours of immersion ⁇ 18 hours of drying as one cycle.
  • the state of the edge portion, the cross-cut portion, and the 4T bent portion of the coated steel sheet test piece after the test was evaluated based on the following evaluation method and evaluation criteria. In each case, a score of 4 or higher was evaluated as good.
  • the total length of the rusted portion in the 4T bent portion was determined and evaluated according to the following criteria. 5: No rust is observed. 4: White rust is observed, but less than 10 mm. 3: White rust is 10 mm or more and less than 25 mm. 2: White rust is 25 mm or more and less than 40 mm. 1: White rust is 40 mm or more, or red rust is observed.
  • edge creep width blister width
  • the average value of the edge creep width (blister width) of the left and right long sides (that is, the long side having the upper burr and the long side having the lower burr) of the coated steel sheet test piece was obtained and evaluated according to the following criteria.
  • Fukure width is 15 mm or more and less than 20 mm.
  • 1 Fukure width is 20 mm or more.
  • the corrosion state of the cross-cut part was evaluated by the following criteria based on the ratio of the length of white rust generated in the exposed part of the substrate with a cut width of 0.5 mm and the average value of the left and right blisters width (sum of both sides) of the cross-cut part. .. 5: The ratio of the length of white rust generated in the exposed portion of the substrate is less than 25%, and the blistering width is less than 3 mm. 4: White rust generation length ratio of 25% or more and less than 50% in the exposed portion of the substrate, and a blistering width of less than 3 mm. 3: White rust generation length ratio of 50% or more and blister width less than 3 mm in the exposed part of the substrate.
  • the surface-treated steel material of the present invention can exhibit excellent rust resistance for a long period of time, and can further form a coating film exhibiting excellent moisture resistance. Moreover, even under acidic environmental conditions, it is possible to form a coating film showing excellent rust prevention properties for a long period of time. Therefore, for example, the generation of rust that may be caused by "acid rain” or the like can be suppressed. Further, it is possible to suppress or greatly reduce the deterioration of the moisture resistance of the coating film, and further, it is possible to suppress or greatly reduce the occurrence of blisters on the coating film.
  • the surface-treated steel material of the present disclosure in an object to be coated which can have various shapes, not only the surface of the object to be coated on a flat surface but also, for example, a processed portion, an end face, a cross-cut portion and the like are coated.
  • the protective effect of the film can be sufficiently exhibited.
  • the surface-treated steel material according to the present invention is equivalent to a test piece formed from a coating composition containing chromium. Or even better rust prevention could be shown.
  • Comparative Examples 1 to 7 do not contain the specific magnesium oxide according to the present disclosure, it is possible to obtain a surface-treated steel material having the same characteristics as those of Examples in terms of rust prevention and moisture resistance. There wasn't.
  • the surface-treated steel material of the present invention can exhibit excellent rust resistance for a long period of time, and can form a coating film exhibiting excellent moisture resistance.

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  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Abstract

L'invention a pour objet de fournir un matériau d'acier traité en surface qui peut présenter d'excellentes propriétés antirouilles sur le long terme, et qui en outre présente une excellente résistance à l'humidité. Plus précisément, l'invention fournit un matériau d'acier traité en surface à la surface duquel est formé un film de revêtement avec une sous-couche contenant au moins une couche de placage d'alliage d'aluminium et de zinc, pour intermédiaire. La couche de placage d'alliage d'aluminium et de zinc contient Ai, Zn, Si et Mg en tant qu'éléments constitutifs. La teneur en Mg est comprise entre ０,１ et １０% en masse. La couche de placage d'alliage d'aluminium et de zinc contient 0,2 à 15% en volume d'une phase Si-Mg. Le rapport massique de la phase Si-Mg est supérieur ou égal à 3% pour la masse totale de Mg dans la couche de placage. Le film de revêtement est formé à partir d'une composition de matériau de revêtement antirouille contenant une résine (A) de formation de film de revêtement antirouille, un agent de réticulation (B) et un oxyde de magnésium (C). L'oxyde de magnésium (C) présente une constante de réseau inférieure à ０,４２１４ｎｍ, et une surface spécifique BET inférieure ou égale à ２,０ｍ２／ｇ.
PCT/JP2020/034943 2019-10-04 2020-09-15 Matériau d'acier traité en surface WO2021065485A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021235363A1 (fr) * 2020-05-20 2021-11-25 日鉄鋼板株式会社 Tôle d'acier plaquée et revêtue
JP7287590B1 (ja) * 2022-03-17 2023-06-06 Ｊｆｅスチール株式会社 表面処理亜鉛めっき鋼板
WO2023176027A1 (fr) * 2022-03-17 2023-09-21 Ｊｆｅスチール株式会社 Tôle d'acier plaquée de zinc traitée en surface
WO2024111458A1 (fr) * 2022-11-25 2024-05-30 日本ペイント・サーフケミカルズ株式会社 Agent de traitement de surface métallique

Citations (2)

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Publication number Priority date Publication date Assignee Title
JP2011068868A (ja) * 2009-08-24 2011-04-07 Kikusui Chemical Industries Co Ltd 防錆塗料
JP2017197795A (ja) * 2016-04-26 2017-11-02 日本ペイント・インダストリアルコ−ティングス株式会社 表面処理鋼材

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6690046B1 (ja) * 2019-10-04 2020-04-28 日本ペイント・インダストリアルコ−ティングス株式会社 防錆塗料組成物及び防錆塗膜の製造方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011068868A (ja) * 2009-08-24 2011-04-07 Kikusui Chemical Industries Co Ltd 防錆塗料
JP2017197795A (ja) * 2016-04-26 2017-11-02 日本ペイント・インダストリアルコ−ティングス株式会社 表面処理鋼材

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021235363A1 (fr) * 2020-05-20 2021-11-25 日鉄鋼板株式会社 Tôle d'acier plaquée et revêtue
JP7287590B1 (ja) * 2022-03-17 2023-06-06 Ｊｆｅスチール株式会社 表面処理亜鉛めっき鋼板
WO2023176027A1 (fr) * 2022-03-17 2023-09-21 Ｊｆｅスチール株式会社 Tôle d'acier plaquée de zinc traitée en surface
WO2024111458A1 (fr) * 2022-11-25 2024-05-30 日本ペイント・サーフケミカルズ株式会社 Agent de traitement de surface métallique

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