Classifications

• • 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
  • B05D7/16—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 using synthetic lacquers or varnishes
• • 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
• • 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
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
• • 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
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
• • 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
• • 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
  • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
  • C23C2/36—Elongated material
  • C23C2/40—Plates; Strips
• • 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
• • 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
  • B05D2202/00—Metallic substrate
  • B05D2202/40—Metallic substrate based on other transition elements

Definitions

• the present invention relates to a surface-treated steel sheet having high corrosion resistance and excellent blackening resistance.
• Plated steel sheets such as galvanized steel sheets with excellent corrosion resistance and blackening resistance are widely used for home appliances, building materials, and automobiles.
• the surface of various plated steel sheets such as galvanized steel sheets may deteriorate depending on the surrounding environment.
• the plating layer is oxidized by an electrolyte such as salt contained in the atmosphere, oxygen and moisture present in a high-temperature and high-humidity environment, and white rust is generated.
• white rust is generated, the appearance uniformity of the plated steel sheet is impaired, so that the plated steel sheet is generally required to have corrosion resistance that suppresses the occurrence of white rust.
• a steel sheet plated with a Zn-based alloy such as a Zn—Al—Mg-based alloy plating is known.
• Zn-based alloy plated steel sheets are required to have both short-term corrosion resistance and long-term corrosion resistance.
• Short-term corrosion resistance means, for example, that the contractor does not corrode in a period (about one year) before delivering the plated steel sheet to the orderer.
• Long-term corrosion resistance means, for example, a product for building materials. This means that the period until the required strength is not obtained is reduced as much as possible.
• Zn-based alloy-plated steel sheet Another characteristic required for Zn-based alloy-plated steel sheet is blackening resistance.
• Blackening means that the plating layer is oxidized and turns black. The blackening particularly occurs remarkably in a Zn—Al alloy-plated steel sheet or a Zn—Al—Mg alloy-plated steel sheet in which Al or Mg is added during galvanization. It is not preferable in use that the discoloration of the plated steel sheet is visually recognized from the appearance due to the blackening of the plating layer. Therefore, Zn-based alloy-plated steel sheets such as Zn—Al—Mg-based alloy plated steel sheets are required to have excellent blackening resistance while having corrosion resistance.
• Patent Document 1 a steel sheet, a Zn—Al—Mg alloy plating layer formed on the surface of the steel plate, and a film containing aluminum formed on the alloy plating layer are excellent in blackening resistance and corrosion resistance.
• a galvanized steel sheet is disclosed.
• Patent Document 2 discloses a chromate-free painted metal plate having a coating film containing a flake-like aluminum pigment having an organic resin as a film-forming component and having a surface deactivated on at least one surface of the metal plate. It is taught that such a metal plate is excellent in corrosion resistance and blackening resistance.
• patent document 3 it has a plated steel plate which has the plating layer arrange
• Chemical conversion steel sheets containing resin, metal flakes and chemical conversion components are disclosed, and it is taught that the use of such steel sheets can improve corrosion resistance and blackening resistance.
• Patent Documents 2 and 3 sufficient control has not been made on the control of the concentration distribution of pigments such as flaky aluminum, and there is still room for improvement in blackening resistance.
• an object of the present invention is to provide a surface-treated steel sheet having high corrosion resistance and excellent blackening resistance in a Zn-based alloy-plated steel sheet.
• the present inventors have used a coloring pigment such as an aluminum pigment in a coating film formed on a Zn-based alloy plating layer. It has been found that it is important to control the average concentration to 5 to 15% by mass%. With such control, when the color pigment is observed from a direction perpendicular to the surface of the coating film, the color pigment sufficiently covers the Zn-based alloy plating layer, so that the color pigment makes the blackening of the Zn-based alloy plating layer invisible. Therefore, the change in appearance can be suppressed and excellent blackening resistance can be obtained.
• the present inventors have also found that it is important to concentrate the color pigment on the Zn-based alloy plating layer side in the coating film.
• the color pigment can be prevented from protruding from the surface of the coating film, thereby preventing the formation of corrosion factor paths and ensuring corrosion resistance. can do.
• the color pigment can be arranged in a narrow area and closer to each other in the coating film. Accordingly, the color pigment can be distributed at a high density in the coating film, and a wider range of the Zn-based alloy plating layer can be effectively invisible, and as a result, the blackening resistance is improved.
• the present invention has been made on the basis of the above findings, and the gist thereof is as follows.
• a steel sheet, a Zn-based alloy plating layer formed on at least one surface of the steel sheet, and a coating film having an average thickness T 1 formed on the Zn-based alloy plating layer and containing a color pigment, a rust preventive pigment, and a binder resin Have The chemical composition of the Zn-based alloy plating layer is mass%, Al: 0.01 to 60%, Mg: 0.001 to 10%, and Si: 0 to 2%, The average concentration of the colored pigment in the coating film is 5 to 15% by mass%, The average concentration C A1 of the color pigment present in the region of width T 2 in the thickness direction of the coating film from the surface of the coating film, and the thickness of the coating film from the interface on the Zn-based alloy plating layer side of the coating film The ratio C A1 / C A2 to the average concentration C A2 of the color pigment present in the region of width T 2 in the direction is 0.2 to 0.9
• the average concentration of the anticorrosive pigment in the coating film is 3% to 12% by mass%
• the average concentration of the color pigment in the coating film is 5 to 15% by mass, and the color pigment is concentrated on the Zn-based alloy plating layer side in the coating film.
• the coloring pigment makes the Zn-based alloy plating layer invisible sufficiently when observed from the direction perpendicular to the coating film surface.
• a surface-treated steel sheet having high corrosion resistance and excellent blackening resistance can be provided.
• the surface-treated steel sheet according to the present invention has high corrosion resistance and resistance even when the thickness of the coating film is reduced because the colored pigment in the coating film is concentrated on the Zn-based alloy plating layer side. Black denaturation can be provided.
• the surface-treated steel sheet according to the present invention is an average comprising a steel sheet, a Zn-based alloy plating layer formed on at least one surface of the steel sheet, and a Zn-based alloy plating layer, and including a color pigment, a rust preventive pigment, and a binder resin.
• the coating composition has a thickness of T 1 and the chemical composition of the Zn-based alloy plating layer is, by mass%, Al: 0.01 to 60%, Mg: 0.001 to 10%, and Si: 0 to 2%
• the average concentration of the colored pigment in the coating film is 5 to 15% by mass, and the average concentration of the coloring pigment existing in the region of the width T 2 from the surface of the coating film in the thickness direction of the coating film.
• ⁇ Steel plate> It does not specifically limit as a steel plate (plating original plate) in this invention, General steel plates, such as a hot-rolled steel plate and a cold-rolled steel plate, can be used.
• the steel type is not particularly limited, and for example, Al-killed steel, ultra-low carbon steel containing Ti, Nb, etc., and high-tensile steel containing elements such as P, Si, Mn, etc. can be used. is there.
• the thickness of the steel plate in the present invention is not particularly limited, but may be, for example, 0.25 to 3.5 mm.
• the Zn-based alloy plating layer in the present invention is formed on a steel plate. This Zn-based alloy plating layer may be formed on one side of the steel plate or on both sides.
• the Zn-based alloy plating layer may be a Zn—Al—Mg alloy plating layer containing at least Al and Mg, and may further be a Zn—Al—Mg—Si alloy plating layer containing Si. Each of these contents (concentrations) is, by mass, Al: 0.01 to 60%, Mg: 0.001 to 10%, and Si: 0 to 2%, with the balance being Zn and impurities.
• % when the chemical composition of the Zn-based alloy plating layer is simply described as “%”, it means “mass%”.
• the Al content of the Zn-based alloy plating layer is less than 0.01%, the effect of improving the corrosion resistance of the plated steel sheet due to the inclusion of Al is not sufficiently exhibited, and when it exceeds 60%, the effect of improving the corrosion resistance is saturated. Therefore, the Al content may be 0.01% or more, such as 0.1% or more, 0.5% or more, 1% or more, 3% or more, or 5% or more, and 60% or less, for example, 55% or less, 50% or less, 40% or less, or 30% or less.
• a preferable Al content is 1 to 60%, more preferably 5 to 60%.
• the Mg content of the Zn-based alloy plating layer is less than 0.001%, the effect of improving the corrosion resistance of the plated steel sheet due to the inclusion of Mg may not be sufficiently exhibited.
• Mg cannot be completely dissolved in the plating bath and floats as an oxide (generally called dross).
• dross oxide
• the oxide adheres to the plating surface layer and causes an appearance defect. There is a risk that a portion that is not plated (generally referred to as non-plating) may occur.
• the Mg content may be 0.001% or more, for example, 0.01% or more, 0.1% or more, 0.5% or more, 1% or more, or 2% or more, and 10% or less. For example, it may be 8% or less, 6% or less, 5% or less, or 4% or less.
• the Mg content is preferably 1 to 5%, more preferably 1 to 4%.
• the lower limit of the Si content of the Zn-based alloy plating layer may be 0%, but in order to further improve the corrosion resistance of the Zn-based alloy plating layer, it may be 0.001% to 2%.
• the Si content may be, for example, 0.005% or more, 0.01% or more, 0.05% or more, 0.1% or more, or 0.5% or more, and 1.8% or less, It may be 1.5% or less or 1.2% or less.
• the Si content is preferably 0.1 to 2%, more preferably 0.5 to 1.5%.
• the Zn-based alloy plating layer in the present invention can be formed by a known plating method such as hot dipping or vapor deposition plating.
• the thickness of the Zn-based alloy plating layer may be 1 to 30 ⁇ m.
• the coating film in the present invention is formed on the Zn-based alloy plating layer.
• the coating film contains a rust preventive pigment and a binder resin in addition to the color pigment.
• the average thickness T 1 of the coating film may be any value as long as sufficient corrosion resistance and blackening resistance are ensured. For example, it is preferably 3 ⁇ m or more and 15 ⁇ m or less. If the average thickness T 1 of the coating film is less than 3 ⁇ m, there is a possibility that a part of the color pigment protrudes from the coating film and the corrosion factor reaches the alloy plating layer, so that sufficient corrosion resistance cannot be secured. .
• the thickness becomes insufficient to ensure the effect of making the Zn-based alloy plating layer invisible by the colored pigment in the coating film, and the blackening resistance may be deteriorated.
• the average thickness T 1 of the coating film is more than 15 ⁇ m, the effect of improving the corrosion resistance and blackening resistance by increasing the average thickness of the coating film is saturated.
• the average thickness T 1 of the coating film may be, for example, 4 ⁇ m or more, 5 ⁇ m or more, or 6 ⁇ m or more, and may be 12 ⁇ m or less or 10 ⁇ m or less. Therefore, the average thickness T 1 of the coating film is more preferably 3 ⁇ m or more and 12 ⁇ m or less.
• blackening resistance does not mean to suppress the occurrence of blackening of the Zn-based alloy plating layer underlying the coating film, and even if blackening occurs in the Zn-based alloy plating layer. This means that the appearance of the surface-treated steel sheet is not changed by making the black pigment visible from the outside by the colored pigment in the coating film.
• average thickness T 1 means any of five locations on the interface of the coating film on the Zn-based alloy plating layer side by observing a cross section of a steel sheet having a coating film with a microscope. The shortest distance from each position to the surface of the coating film is measured, and the measured values are averaged.
• the substance for example, aggregate
• the said distance is measured in the position where the substance does not exist. This is because the presence of such a substance may cause the distance to be measured to be larger than the actual thickness of the coating film when the coating film is observed from the cross-sectional direction.
• another layer like a chemical conversion treatment layer may exist between a Zn type alloy plating layer and a coating film. When such another layer exists, the thickness of the layer is not included in the average thickness T 1 .
• the colored pigment in the present invention for example, a general colored pigment such as titanium oxide, zinc oxide, iron oxide, aluminum oxide, barium sulfate, aluminum, or carbon black can be used.
• the color pigment is aluminum.
• aluminum is eluted by reacting with water. Therefore, when a water-based paint is used as a paint for forming a coating film as in the present invention, it is necessary to coat aluminum with an oxide or a resin.
• the average concentration (average content) of the colored pigment in the coating film is 5 to 15% by mass.
• the color pigment can make the blackening of the Zn-based alloy plating layer invisible, thereby suppressing the change in appearance and obtaining excellent blackening resistance. If the average concentration of the color pigment in the coating film is less than 5%, the density of the color pigment in the coating film for making the blackening of the Zn-based alloy plating layer invisible becomes insufficient, and the blackening resistance decreases. On the other hand, when the average concentration of the colored pigment in the coating film exceeds 15%, a large amount of the coloring pigment is present in the coating film. When the coating film is thinned, a part of the coloring pigment is relatively early. The possibility of protruding from the surface of the coating film increases, and the corrosion resistance may deteriorate.
• the average concentration of the color pigment in the coating film may be 6% or more, 7% or more, and may be 12% or less or 10% or less.
• the average concentration of the color pigment in the coating film is preferably 5 to 12%, more preferably 5 to 10%.
• the “average concentration of colored pigments in the coating film” is measured using a glow discharge optical emission surface analysis device (Glow Discharge Optical Emission Spectrometry: GD-OES). Specifically, when the type of the color pigment, that is, the specific compound of the color pigment is known, the coating film is sputtered from the surface toward the plating layer, and the major elements constituting the color pigment are deepened. The vertical density profile is measured every 1.0 ⁇ m. Then, the average value of the measured concentration of the main element is obtained, the measured concentration is converted based on the molecular weight of the known colored pigment compound, and the average concentration of the colored pigment in the coating film is obtained.
• GD-OES glow discharge optical emission surface analysis device
• the field emission electron probe microanalyzer Field Emission-Electron Probe
• the “average concentration of the color pigment in the coating film” may be measured as described above.
• the colored pigment in the coating is concentrated on the Zn-based alloy plating layer side.
• the color pigment concentration index is based on the average concentration C A1 of the color pigment present in the region of width T 2 in the thickness direction of the coating film from the surface of the coating film and the interface on the Zn-based alloy plating layer side of the coating film. It is determined by the ratio C A1 / C A2 to the average concentration C A2 of the color pigment existing in the region of the width T 2 in the thickness direction of the coating film.
• the ratio C A1 / C A2 of the surface-treated steel sheet according to the present invention is 0.2 or more and 0.9 or less.
• C A1 and C A2 are set as described above. Measure and determine the ratio C A1 / C A2 .
• such a surface-treated steel sheet is not included in the scope of the present invention.
• the ratio C A1 / C A2 of the surface-treated steel sheet according to the present invention is 0.2 or more and 0.9 or less.
• this ratio C A1 / C A2 is less than 0.2, the rust preventive pigment is relatively concentrated on the surface side of the coating film, and when the coating thickness is reduced, the rust preventive pigment is relatively short. As a result, a layer having a low concentration is exposed and sufficient long-term corrosion resistance cannot be obtained.
• the ratio C A1 / C A2 exceeds 0.9, the effect of thickening the colored pigment cannot be obtained, and a part of the colored pigment protrudes from the coating film, resulting in insufficient corrosion resistance.
• the C A1 / C A2 ratio may be, for example, 0.3 or more or 0.4 or more, and may be 0.8 or less or 0.7 or less.
• the C A1 / C A2 ratio is preferably 0.3 or more and 0.8 or less, and more preferably, the C A1 / C A2 ratio is 0.4 or more and 0.7 or less.
• the “average concentration C A2 of the colored pigment existing in the region of the width T 2 ” is measured using GD-OES in the same manner as the “average concentration of the colored pigment in the coating film”. Specifically, sputtering is performed from the surface direction of the coating film to the depth direction of the Zn-based alloy plating layer, and the concentration distribution in the depth direction of the coating film with respect to the main elements constituting the color pigment is increased by 0.1 ⁇ m. measured in the range of T 2.
• the average value of the measured concentration of the main element is obtained, the measured concentration is converted based on the molecular weight of the known colored pigment compound, and the average concentration of the colored pigment in the coating film is obtained.
• the sputtering time can be converted into coating thickness information by measuring the relationship between the sputtering time and the coating depth in advance.
• C A1 and C A2 can be obtained by measuring the concentration distribution in the film thickness direction of the elements constituting the color pigment.
• the ratio C A1 / C A2 in the coating film is 0.2 or more and 0.9 or less.
• the color pigment concentration on the surface side of the coating film becomes relatively low.
• the surface-treated steel sheet according to the present invention has a Zn-based alloy plating layer as compared with the case where the coloring pigment is uniformly distributed in the coating film. It can be made invisible effectively from the outside, and thus the blackening resistance is significantly improved.
• the colored pigment is distributed in a narrow region, when a pigment having an orientation having a high average aspect ratio (for example, scaly shape, flat shape, etc.) is used,
• the direction can be aligned parallel or substantially parallel to the surface of the coating film, and the plating layer can be effectively invisible, and the blackening resistance can be improved.
• the colored pigment according to the present invention can have any shape as long as sufficient corrosion resistance and blackening resistance are ensured, but the shape of the colored pigment is not limited to, for example, spherical, elliptical, acicular, Examples include a flat shape, a thin plate shape, a scale shape, and a spindle shape.
• the colored pigment in the present invention is preferably scaly in order to make the Zn-based alloy plating layer invisible more effectively and to obtain excellent blackening resistance.
• the “average particle size” and “average aspect ratio” for the colored pigment according to the present invention are determined by the following methods. First, an arbitrary one colored pigment is elementally mapped from the surface by FE-EPMA, and the major axis X 1 and minor axis X 2 of the colored pigment are obtained.
• the major axis X 1 means the length of the largest line segment that crosses the colored pigment in the contour of the color pigment image specified by element mapping
• the minor axis X 2 means the colored pigment. It means the length of the perpendicular line to the major axis X 1 across the.
• element mapping is performed from the cross-sectional direction by FE-EPMA, and the value of the thickness X 3 (generally, the dimension in the direction perpendicular to the measurement plane of the major axis and the minor axis described above) is measured.
• the particle diameter and the aspect ratio are obtained for any 10 or more colored pigments, and each is averaged to obtain the “average particle diameter” and “average aspect ratio” of the colored pigment.
• the major axis X 1 , minor axis X 2 and thickness X 3 of the color pigment according to the present invention can be any value as long as they can be present in the coating film.
• the major axis X 1 is 5 ⁇ m or more and 30 ⁇ m or less.
• the minor axis X 2 is preferably 1 ⁇ m or more and 30 ⁇ m or less, and the thickness X 3 is preferably 0.0025 ⁇ m or more.
• the average particle diameter of the color pigment according to the present invention is preferably, for example, 7 ⁇ m or more and 30 ⁇ m or less, and the average aspect ratio is preferably 20 or more.
• the color pigment has a high aspect ratio, the color pigment can make the Zn-based alloy plating layer invisible in a wide range, and the blackening resistance can be further enhanced.
• the average particle diameter of the color pigment is less than 7 ⁇ m, the Zn-based alloy plating layer cannot be sufficiently invisible and the blackening resistance may be insufficient.
• the average particle diameter of the colored pigment exceeds 30 ⁇ m, there is a possibility that the colored pigment may protrude from the coating film and sufficient corrosion resistance may not be ensured.
• the average aspect ratio is less than 20, the Zn-based alloy plating layer cannot be made sufficiently invisible and blackening resistance may be insufficient.
• the average particle size of the color pigment according to the present invention is more preferably 10 ⁇ m or more and 25 ⁇ m or less.
• the average aspect ratio is more preferably 25 or more, and further preferably 30 or more.
• the upper limit of the average aspect ratio is not limited, but may be 100, for example.
• the values of the major axis X 1 and the minor axis X 2 are close, that is, the ratio X 1 / X 2 is close to 1.0. Is more advantageous.
• the ratio X 1 / X 2 is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, and even more preferably 1.0 or more and 2.0 or less. Can be.
• the thickness X 3 of the coloring pigment is smaller than the average thickness T 1 of the coating film. Further, if the color pigment protrudes from the coating film, a corrosion factor penetration path may be formed and the corrosion resistance may be deteriorated. Therefore, the color pigment thickness X 3 is smaller than the average thickness T 1 of the coating film. Is more advantageous.
• the color pigment thickness X 3 is preferably 0.5 T 1 or less, and more preferably 0.4 T 1 or less.
• Anti-rust pigment As a rust preventive pigment used in the coating film in this invention, 1 type, or 2 or more types of Si, Mo, W, and Ba can be included. Preferably, one or more of Si, Mo and Ba are included. Specific examples of these compounds include, but are not limited to, silica (Grace, MSK-8D), calcium-modified silica (WR Grace, SHIELDEXC303), barium borate (Showa Chemicals Reagents).
• the rust preventive pigment is silica.
• the rust preventive pigment can be porous. By making it porous, the specific surface area is large and the apparent specific gravity is low, so it is easier to concentrate on the surface side of the coating film.
• a rust preventive pigment for example, silica having a specific surface area of 20 m 2 / g or more, for example, 50 m 2 / g or more, 100 m 2 / g or more, or 200 m 2 / g or more is used. It can.
• the upper limit of the specific surface area of a rust preventive pigment is not specifically limited, For example, what is necessary is just 500 m ⁇ 2 > / g.
• “apparent specific gravity” means the density when the rust preventive pigment itself and the internal voids are in volume, and includes “the volume of the rust preventive pigment itself” and “the volume of the internal voids”. It is.
• the average concentration of the rust preventive pigment in the coating film can be 3 to 12% by mass%. By setting it as such a range, a coating film can fully function as a film
• the adhesion may be reduced.
• the average concentration of the anticorrosive pigment in the coating film may be 4% or more, 5% or more, or 6% or more, and may be 11% or less or 10% or less.
• the average concentration of the rust preventive pigment in the coating film is preferably 5 to 12% or less, more preferably 5 to 10% or less.
• the average concentration of the anticorrosive pigment in the coating film can be obtained using the same method as the above-described “average concentration of the colored pigment in the coating film”.
• the rust preventive pigment in the coating is concentrated on the surface side of the coating.
• the ratio C B1 / C B2 of the surface-treated steel sheet according to the present invention is 1.2 or more and 5.0 or less when the ratio C A1 / C A2 for the color pigment is 0.2 or more and 0.9 or less. In order to more reliably obtain the effect of concentration of the rust preventive pigment on the surface layer side, it is preferably 1.3 or more and 4.0 or less. If this ratio C B1 / C B2 is less than 1.3, the effect of thickening the rust-preventing pigment, which improves the long-term corrosion resistance of the plane portion, may not be obtained sufficiently.
• the ratio C B1 / C B2 may be 1.5 or more, 1.8 or more, or 2.0 or more, and may be 3.8 or less, 3.5 or less, or 3.2 or less.
• the ratio C B1 / C B2 is preferably 1.5 or more and 3.5 or less, and more preferably the ratio C B1 / C B2 is 1.8 or more and 3.2 or less.
• C B1 and C B2 are obtained by the same method as C A1 and C A2 described above.
• the anticorrosive pigment in the coating film is distributed in the coating film so that the value of the above ratio C B1 / C B2 is 1.3 or more and 4.0 or less, that is, the antirust pigment is on the surface side of the coating film.
• the corrosion resistance of the surface of the coating film is sufficiently improved, and the long-term corrosion resistance in the flat portion is further improved.
• the average particle diameter of the rust preventive pigment can be appropriately selected according to the average thickness T 1 of the coating film, and can be 0.2 to 10 ⁇ m.
• the average particle diameter of the rust preventive pigment is preferably 0.4 to 8 ⁇ m, and more preferably 0.5 to 6 ⁇ m.
• the average particle diameter of the rust preventive pigment can be determined by the same method as the average particle diameter of the color pigment described above. That is, for 10 or more rust preventive pigments, element mapping is performed by FE-EPMA from the surface and cross-sectional direction of the coating film, and the major axis Y 1 , minor axis Y 2 and thickness Y 3 of the rust preventive pigment are obtained. The average particle diameter of the rust preventive pigment can be determined from the value.
• the thickness Y 3 of the rust preventive pigment is preferably somewhat smaller than the average thickness T 1 of the coating film as in the case of the color pigment.
• the thickness Y 3 of the rust preventive pigment is , preferably at 0.5 T 1 or less, more preferably 0.4 T 1 or less, even more preferably at 0.3 T 1 or less, most preferably 0.1 T 1 or less.
• the binder resin used as a component of the coating film in the present invention is preferably a polyester resin, a urethane resin, or an acrylic resin. In the present invention, it is important to use an imino group type melamine resin as a curing agent for these resins.
• the binder resin in the present invention is a polyester resin.
• the polyester resin used in the present invention preferably has a glass transition temperature Tg of ⁇ 20 to 70 ° C. and a number average molecular weight of 3000 to 30000. When the binder resin is a urethane resin, it is preferable that Tg is 0 to 50 ° C. and the number average molecular weight is 5000 to 25000.
• the binder resin is an acrylic resin
• Tg is 0 to 50 ° C. and the number average molecular weight is 3000 to 25000.
• an aqueous solvent is used as a solvent for the binder resin.
• wax such as polyethylene wax or PTFE wax
• resin beads such as acrylic resin beads or urethane resin beads
• phthalocyanine blue phthalocyanine green
• methyl orange methyl violet
• a dye such as alizarin
• the strength of the coating film is increased, or a desired color can be imparted to the coating film, which is more preferable. What is necessary is just to determine these addition amounts suitably so that it may not become disadvantageous for the coating film in this invention.
• a dye can be used as a colorant in order to impart a desired color to the coating film according to the present invention, and thus to the surface-treated steel sheet according to the present invention.
• the dyes may be used alone or in combination of a plurality of dyes.
• a well-known dye can be used, For example, phthalocyanine blue, phthalocyanine green, methyl orange, methyl violet, or alizarin is used. be able to.
• the surface-treated steel sheet according to the present invention is, for example, an aqueous solution in which a coloring pigment and a rust preventive pigment are added to a Zn-based alloy plating layer formed on a steel sheet, and an imino group type melamine resin is added as a curing agent for the binder resin. It can be produced by applying a paint and heating it with a predetermined heat pattern to cure the paint.
• ⁇ Formation of Zn-based alloy plating layer> As a steel plate, what has arbitrary board thickness and chemical composition can be used. For example, a cold rolled steel sheet having a thickness of 0.25 to 3.5 mm can be used.
• the Zn-based alloy plating layer can be formed by hot-plating Zn—Al—Mg alloy plating on a steel plate to a thickness of 1 to 30 ⁇ m. The hot dipping can be performed, for example, in a hot dipping bath at 400 to 550 ° C. to which various metals are added.
• the contents of Al and Mg are, by mass, Al: 0.01 to 60%, Mg: 0.001 to 10%, and the balance is typically Zn and impurities.
• a Zn—Al—Mg—Si alloy plating layer containing Si: 0.001 to 2% by mass% can also be formed.
• the paint is prepared by mixing a binder resin such as a polyester resin dispersed in a solvent (for example, molecular weight: 16000, Tg: 10 ° C.) and an imino group-type melamine resin at a solid content mass ratio of 100: 10 to 100: 30, Subsequently, it can obtain by disperse
• a solvent for example, an aqueous solvent (for example, water) is used.
• the rust preventive pigment in the coating film is concentrated on the surface side of the coating film, and the color pigment in the coating film is concentrated on the Zn-based alloy plating layer side.
• concentration distribution of anti-corrosion pigments and colored pigments can be formed by utilizing the phenomenon that the imino group-type melamine resin is concentrated on the surface layer of the coating film under specific conditions.
• the present inventors have found out.
• the concentration of the anticorrosive pigment on the surface side of the coating is selected by selecting an anticorrosive pigment (for example, porous silica) having an apparent specific gravity smaller than that of the colored pigment, ie, having a large specific surface area.
• the rust preventive pigment moves to the surface layer together with the melamine resin.
• the thickening mechanism is not only due to the apparent specific gravity difference between the colored pigment and the rust preventive pigment, but also has chemical affinity between the imino group-type melamine resin and the rust preventive pigment, and they mutually interact. By acting, it is considered that the rust preventive pigment is concentrated on the surface side of the coating film as the imino group type melamine resin is concentrated on the surface layer.
• the concentration of the imino group-type melamine resin on the surface layer is more conspicuous than when a solvent system is used.
• the inventors have found. This is presumably because the imino group-type melamine resin that did not crosslink with polyester or the like when the coating was cured to form a coating film was present more in the aqueous coating than in the solvent-based coating.
• the polyester resin or the like is dispersed in an emulsion state, so that a crosslinking reaction between the reactive functional group (OH group) inside the emulsion particles and the imino group type melamine resin occurs.
• the concentration of the imino group type melamine resin on the surface layer was remarkable.
• the thickening effect of imino group-type melamine resins in water-based paints is that the compatibility between water and melamine is low, and the surface free energy of imino group-type melamine resins is smaller than that of water. It can also be considered that this is because the melamine resin easily floats on the surface layer. Accordingly, in the present invention, it is effective to use an aqueous solvent as a solvent in order to promote concentration of the imino group type melamine resin on the surface layer.
• a methylated melamine resin and a butylated melamine resin are generally known in addition to the imino group type melamine resin used in the present invention.
• methylated melamine resin is added as a curing agent in water-based paints, there is no noticeable concentration phenomenon on the surface layer of rust-preventive pigment during baking, and butylated as a curing agent in water-based paints.
• the present inventors have found that the paint is solidified when mixed with an aqueous solvent and cannot be used as a paint. Therefore, in order to obtain a coating film as in the present invention, it is extremely effective to use a combination of an aqueous solvent, a binder resin, and an imino group type melamine resin as a curing agent for the binder resin.
• a rust preventive pigment is concentrated on the surface side of the paint film, a relatively heavy color pigment such as aluminum in the paint film It becomes difficult to be distributed on the surface side of the film and is relatively concentrated on the Zn-based alloy plating layer side.
• the rust preventive pigment is concentrated on the surface side of the coating film, so that the colored pigment is pressed down so as to remain on the Zn-based alloy plating layer side in the coating film.
• a surface-treated steel sheet in which the ratio C B1 / C B2 of the anticorrosive pigment in the coating film is 1.2 or more and 5.0 or less, preferably 1.3 or more and 4.0 or less is obtained.
• a surface-treated steel sheet according to the present invention in which the ratio C A1 / C A2 of the color pigment in the coating film is 0.2 or more and 0.9 or less is obtained. Also, to concentrate the rust preventive pigment and the colored pigment on the surface layer side and the Zn-based alloy plating layer side, respectively, depending on the properties of the imino group type melamine resin in the water-based paint, select the particle size and specific gravity of the rust preventive pigment. Is effective. In order to obtain the concentration distribution of the rust preventive pigment and the color pigment according to the present invention, it is effective that the average particle diameter of the rust preventive pigment is 0.2 to 10 ⁇ m and the specific surface area is 20 m 2 / g or more.
• an acidic catalyst can be added to the paint to concentrate the melamine resin on the surface layer of the coating film, if necessary.
• the acidic catalyst include, but are not limited to, a weakly acidic catalyst (Catalyst 296-9 / Ornex Japan), a strongly acidic catalyst (Catalyst 600 / Ornex Japan), or an amine block strongly acidic catalyst (Catalyst). 602 / manufactured by Ornex Japan) can be used.
• the acidic catalyst is added in an amount of 0.1 to 1.0% by mass in the paint.
• the obtained paint can be applied on the Zn-based alloy plating layer with a predetermined thickness, for example, by a roll coater, and baked and cured with a predetermined heat pattern.
• the baking is performed at a heating rate of 5 to 70 ° C./second so that the steel plate temperature finally reaches 180 to 230 ° C.
• the steel plate temperature can be maintained for 1 to 5 seconds, preferably 1 to 3 seconds at a temperature of 70 to 150 ° C., preferably 100 to 150 ° C. is important.
• the plated steel sheet at room temperature (for example, 20 ° C.) is once heated to 70 to 150 ° C. (first heating step) and held at that temperature for 1 to 5 seconds.
• first heating step Further heating to 180 to 230 ° C. (second heating step) provides the coating film in the present invention.
• Such a heat pattern can be realized by two heating furnaces. Specifically, the heating furnace A and the heating furnace B are installed in order with respect to the sheet passing direction of the Zn-based alloy plated steel sheet coated with the paint, and the heat treatment is performed between the heating furnace A and the heating furnace B. It is preferable to provide a temperature holding region that is not performed.
• the temperature of the plated steel sheet coated with the paint in the heating furnace A is raised to a temperature of 70 to 150 ° C., held at that temperature in the temperature holding region for 1 to 5 seconds, and then heated to 180 to 230 ° C. in the heating furnace B.
• the paint can be cured by raising the temperature to between.
• the heat pattern may be performed continuously as described above, or may be performed batchwise.
• the antirust pigment can be efficiently concentrated on the surface layer as the surface layer of the imino group type melamine resin is concentrated.
• the concentration of the rust preventive pigment according to the present invention and thus the concentration of the colored pigment is efficiently obtained. It may not be possible.
• the holding temperature exceeds 150 ° C.
• the binder resin reacts with the curing agent, the viscosity of the paint increases, and the rust preventive material becomes difficult to move to the surface layer. It may not be obtained.
• the concentration ratio of the rust preventive pigment according to the present invention is based on melamine concentration as described above, and can be controlled by the melamine resin type and melamine resin concentration used. In addition, it can be adjusted by the heat pattern at the time of curing the coating film, the average particle diameter and specific gravity of the rust preventive pigment, and the like. Specifically, an aqueous solvent, a binder resin such as a polyester resin, and a curing agent that is an imino group type melamine resin are used so that the ratio of the binder resin to the curing agent is in the range of 100: 10 to 100: 30. And a color pigment and a rust preventive pigment are added to prepare a paint.
• the surface-treated steel sheet according to the present invention can be manufactured. That is, the average concentration C A1 of the color pigment present in the region of the width T 2 in the thickness direction of the coating film from the surface of the coating film and the thickness direction of the coating film from the interface on the Zn-based alloy plating layer side of the coating film
• a surface-treated steel sheet having a size of +1.1 ⁇ m can be produced.
• ⁇ Preparation of surface-treated steel sheet sample> (Formation of Zn-based alloy plating layer) A cold-rolled steel sheet having a thickness of 1 mm is immersed in a hot-dip plating bath having a chemical composition of Al: about 11%, Mg: about 3%, and Zn: about 86% at about 450 ° C. for 3 to 5 seconds. A Zn-11% Al-3% Mg alloy plating layer having a thickness of about 10 ⁇ m was formed. Also, the composition of the dissolution plating bath was changed, and a Zn-1% Al-1% Mg alloy plating layer and Zn-40% Al-8% Mg alloy plating having a thickness of about 10 ⁇ m were applied on the cold-rolled steel sheet in the same procedure. A layer was formed.
• a cold rolled steel sheet having a thickness of 1 mm is placed in a hot-dip plating bath at about 450 ° C. with a chemical composition of Al: about 11%, Mg: about 3%, Si: about 1%, and Zn: about 85%. It was immersed for 2 seconds to form a Zn-11% Al-3% Mg-1% Si alloy plating layer having a thickness of about 10 ⁇ m on the cold-rolled steel sheet.
• the composition of the dissolution plating bath was changed, and a Zn-11% Al-3% Mg-0.4% Si alloy plating layer and Zn-11% Al having a thickness of about 10 ⁇ m were formed on the cold-rolled steel sheet in the same procedure. A ⁇ 3% Mg—1.5% Si alloy plating layer was formed.
• a polyester resin (molecular weight: 16,000; glass transition point: 10 ° C.) as a binder resin was dispersed in water as an emulsion, and the pH was adjusted to 8.0 to 9.0.
• the imino group type melamine resin was mixed therein. The ratio of the concentration of the polyester resin and the imino group type melamine resin was 100: 20.
• resin-coated aluminum having an average particle diameter of 10 ⁇ m and an average aspect ratio of 25 (major axis X 1 : 12 ⁇ m, minor axis X 2 : 8 ⁇ m, thickness X 3 : 0.40 ⁇ m) as a color pigment, and the average particle diameter 3 ⁇ m of Si two compounds as rust pigment (silica a: a specific surface area of 320 m 2 / g, silica B: specific surface area of 180m 2 / g), Ba two compounds (barium borate a: a specific surface area of 40 m 2 / g , Barium borate B: specific surface area 4.2 m 2 / g), Mo compound (calcium molybdate: specific surface area 80 m 2 / g) or W compound (tungsten oxide: specific surface area 40 m 2 / g) A paint was prepared.
• the addition amounts of the color pigment and the rust preventive pigment were appropriately adjusted so that a desired concentration was obtained in the coating film when measured using GD-OES.
• Table 1 shows the types of anticorrosive pigments added (Si-A is silica A, Si-B is silica B, Ba-A is barium borate A, Ba-B is barium borate B, and Mo is molybdic acid. Calcium and W represent tungsten oxide).
• Sample No. No. 32 is an example in which no rust preventive pigment was added.
• 35 is an example in which a methylated melamine resin is used in place of the imino group type melamine resin.
• the coating material prepared as described above was applied on a Zn-based alloy plating layer with a roll coater so that the average thickness T 1 of the coating film to be formed was 5 ⁇ m and cured by baking. Baking was performed under the conditions as described in Table 1 (attainment temperature A, heating time A, heating rate A, holding time, attainment temperature B, heating time B, heating rate B). Specifically, first, the temperature at the start of baking of the plated steel sheet on which the Zn-based alloy plating layer is formed is maintained at 20 ° C., and the coating material is applied to the plated steel sheet, as described in Table 1.
• the temperature was raised at the heating rate A to the ultimate temperature A in the heating furnace A, held at the ultimate temperature A for a predetermined holding time, and then heated at the heating rate B to the ultimate temperature B in the heating furnace B.
• the ratio C A1 / C A2 and / or the ratio C B1 / C B2 of the sample of the surface-treated steel sheet was adjusted by changing the combination of the heating rate at the time of baking, the ultimate temperature of the steel sheet, and the holding time.
• the average concentration of the colored pigment in the coating film; the average concentration of the rust preventive pigment in the coating film; the ratio C A1 / C A2 for the color pigment; and the ratio C B1 / C for the rust preventive pigment B2 was determined by elemental analysis using GD-OES. The values determined in this way are shown in Table 1.
• Each sample was subjected to a salt spray test (based on the JASO M609-91 method) as an evaluation test for corrosion resistance.
• This salt spray test consists of (1) salt spray 2 hours (5% NaCl, 35 ° C.); (2) drying 4 hours (60 ° C.); and (3) wet 2 hours (50 ° C., humidity 95% or more). A total of 120 cycles (total 960 hours) were performed as one cycle.
• the end face of each sample was sealed with a tape and tested. Each sample had a width of 50 mm and a length of 100 mm.
• the corrosion resistance was evaluated by observing the surface (planar portion) of the sample after 960 hours of the salt spray test with an optical microscope and determining the rust generation area ratio Z. Specifically, first, the surface of the sample was read with a scanner. Then, the area
• the evaluation of blackening resistance was determined by measuring “color change ⁇ L * ” (lightness L of the sample after the test ⁇ lightness L of the sample before the test) on the surface of the sample before and after performing the weather resistance test.
• ⁇ L * was determined by color tone measurement (JIS Z8729) based on the CIE color system (L * a * b * color system) using a spectrocolorimeter (Suga Test Instruments Co., Ltd .: SC-T45). .
• the score was determined in 8 steps as follows. A score of 3 or higher was considered acceptable for blackening resistance.
• Score 8 ⁇ L * ⁇ 1 Score 7: 1 ⁇ L * ⁇ 2 Score 6: 2 ⁇ L * ⁇ 3 Score 5: 3 ⁇ L * ⁇ 4 Score 4: 4 ⁇ L * ⁇ 5 Score 3: 5 ⁇ L * ⁇ 6 Score 2: 6 ⁇ L * ⁇ 7 Score 1: 7 ⁇ L *
• Examples 1 to 8 are examples when the ratio C A1 / C A2 of the color pigment is changed. Sample No. In Nos. 2 to 7, the ratio was in the range of 0.2 to 0.9 of the range according to the present invention, so that it had sufficient corrosion resistance and blackening resistance.
• sample No. In No. 1 since the ratio C A1 / C A2 was less than 0.2, the rust preventive pigment was relatively concentrated on the surface side of the coating film, and there was a region where the rust preventive pigment was insufficient in a relatively short time. As a result, the corrosion resistance was insufficient.
• Sample No. In No. 8 since the ratio C A1 / C A2 was more than 0.9, the color pigment was dispersed almost uniformly in the coating film, and many coloring pigments were present on the surface side of the coating film. The formation of the path could not be sufficiently suppressed, and the corrosion resistance was insufficient. Furthermore, sample no. In No. 8, when the surface of the coating film was thinned, the concentration of the color pigment in the coating film was insufficient, so that the underlying Zn-based alloy plating layer could not be made sufficiently invisible, and blackening resistance was insufficient. became.
• Examples 4 and 9 to 12 are examples in the case where the type of the rust preventive pigment is changed while the ratio C A1 / C A2 is kept constant. Sample No. 4 and 9-12 all had excellent corrosion resistance and blackening resistance. In particular, when the rust preventive pigment contains Si—A, Si—B, Ba—A, or Mo, it has better corrosion resistance. No. No. 13 is No.13. In this example, the same rust preventive agent Si—B as in No. 12 was used, and the ratio C A1 / C A2 and the ratio C B1 / C B2 were changed, and had sufficient corrosion resistance and blackening resistance.
• Sample No. in Table 1 3 and 14-16, or sample no. Examples 6 and 17 to 19 are examples in which the ratio C B1 / C B2 for the rust preventive pigment is changed while the ratio C A1 / C A2 for the colored pigment is constant. All the samples had sufficient corrosion resistance and blackening resistance. Further, when the ratio C B1 / C B2 of the anticorrosive pigment was 1.3 or more and 4.0 or less, the corrosion resistance was further excellent.
• Sample No. in Table 1 Examples 20 to 25 are examples in the case where the average concentration of the color pigment in the coating film is changed. Sample No. In Nos. 21 to 24, since the average concentration of the color pigment was in the range of 5% by mass or more and 15% by mass or less of the range according to the present invention, it had sufficient blackening resistance and corrosion resistance.
• sample No. In No. 20 since the average concentration of the colored pigment in the coating film was less than 5% by mass, the density of the colored pigment in the entire coating film was insufficient, and the underlying Zn-based alloy plating layer could not be sufficiently seen. The blackening resistance was insufficient.
• Sample No. In No. 25 since the average concentration of the color pigment in the coating film was more than 15% by mass, the color pigment protruded from the surface of the coating film even when the ratio C A1 / C A2 was within the range according to the present invention. The formation of a path through which the factor can pass cannot be sufficiently suppressed, and the corrosion resistance becomes insufficient.
• Sample No. in Table 1 Nos. 26 to 31 are examples when the average concentration of the anticorrosive pigment in the coating film is changed. All the samples had sufficient corrosion resistance and blackening resistance.
• the average concentration of the rust preventive pigment in the coating film is in the range of 3% by mass or more and 12% by mass or less, the corrosion resistance improving effect by the rust preventive pigment becomes remarkable, and an appropriate amount of the rust preventive pigment is formed on the surface layer. Since the orientation of the color pigment was excellent, it had better corrosion resistance and blackening resistance.
• Sample No. in Table 1 Since No. 32 contained no rust preventive pigment in the coating film, the corrosion resistance and blackening resistance were insufficient.
• Sample No. No. 33 has a small specific surface area of the rust preventive pigment, that is, a high specific gravity, and the concentration distribution of the color pigment and the rust preventive pigment could not be controlled even when the imino group type melamine resin was used as a curing agent. Became insufficient.
• Sample No. No. 34 has a high holding temperature, cannot obtain the desired color pigment and rust preventive pigment concentration distribution, and the rust preventive pigment is excessively concentrated on the surface side of the coating film. An area where pigment is insufficient appears and corrosion resistance is insufficient.
• Sample No. No. 35 uses a methylated melamine resin as a curing agent, the concentration phenomenon does not occur remarkably, and the concentration distribution of the color pigment and the rust preventive pigment cannot be controlled, so that the corrosion resistance and blackening resistance are insufficient. It became.
• Sample No. in Table 1 36 to 40 are sample Nos. This is an example in which only the chemical composition of the Zn-based alloy plating layer was changed from 4 and had sufficient blackening resistance and corrosion resistance.
• the average concentration of the color pigment in the coating film is 5% by mass or more and 15% by mass or less, and the color pigment is concentrated on the Zn-based alloy plating layer side in the coating film.
• the surface-treated steel sheet had a surface-treated steel sheet having high corrosion resistance and excellent blackening resistance.
• sample Nos. 4 as a reference, the average particle diameter and average aspect ratio of the color pigment contained in the coating film and the average thickness T 1 of the coating film were changed, and the sample No. Nos. 41 to 58 were prepared, and their corrosion resistance and blackening resistance were evaluated.
• Sample No. for Samples 41 to 58 the production conditions were changed as appropriate, and Sample Nos. The ratio C A1 / C A2 : 0.5 and the ratio C B1 / C B2 : 2.5 were obtained.
• the color pigment resin-coated aluminum was used in the same manner as the samples in Table 1.
• the rust preventive pigment silica A having an average particle diameter of 3 ⁇ m was used.
• the evaluation of the corrosion resistance and blackening resistance scores was performed using sample No. The same procedure as in 1 to 40 was performed.
• the major axis X 1 , minor axis X 2 and thickness X 3 of the color pigment used, the average particle diameter and average aspect ratio of the color pigment obtained therefrom, and the average thickness T 1 of the resulting coating film Table 2 shows the corrosion resistance score and blackening resistance score.
• X 1 to X 3 were determined by examining 15 colored pigments in the coating using FE-EPMA, and the average particle diameter and average aspect ratio of the colored pigments were determined from these values.
• the average thickness T 1 of the coating film was determined from cross-sectional observation by SEM.
• a surface-treated steel sheet having high corrosion resistance and excellent blackening resistance can be provided.
• the present invention can be said to be an invention with extremely high industrial value.

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