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
  • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
• • 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
  • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
• • 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
  • 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
• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process
  • C25D13/12—Electrophoretic coating characterised by the process characterised by the article coated
  • C25D13/16—Wires; Strips; Foils
• • 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
  • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents

Definitions

• the present invention relates to surface-treated metal sheets and automotive components.
• automotive parts are made from metal sheets such as steel sheets, and are manufactured through a number of processes, such as (1) cutting the metal sheets to a specified size, (2) cleaning the cut metal sheets, (3) press-forming the cleaned metal sheets, (4) joining the formed materials by spot welding or gluing, (5) degreasing and cleaning the press oil from the surfaces of the joined parts, (6) chemical treatment, and (7) painting.
• automotive parts used as exterior panels generally also go through painting processes such as (8) undercoat and (9) topcoat. Therefore, there is a high demand in the automotive industry for cost reductions through simplification of manufacturing processes, especially chemical treatment and painting processes.
• the corrosion resistance of automotive parts is often ensured by a chemical conversion treatment layer formed in a chemical conversion treatment process, and an electrocoat coating film formed in a subsequent electrocoat coating process.
• the joints of molded parts are not covered by the electrocoat coating film and are likely to be exposed to a corrosive environment in a bare state.
• anti-corrosion secondary materials such as sealers and anti-corrosion wax are used to supplement the corrosion resistance of the joints of molded parts.
• the use of these anti-corrosion secondary materials not only increases the manufacturing costs of automobiles, but also reduces productivity and increases the weight of the vehicle body. For this reason, there is a high demand for automotive parts that can ensure corrosion resistance even if these anti-corrosion secondary materials are reduced.
• Patent Document 1 discloses a surface-treated metal sheet that meets the above needs, in which a coating film containing a binder resin, oxide particles, non-oxide ceramic particles, and an anti-rust pigment is formed on the surface of the metal sheet.
• the oxide particles dissolve in the chemical conversion treatment process to impart an anchor effect to the chemical conversion treatment layer, thereby improving the adhesion of the subsequently formed electrodeposition coating film to the surface-treated metal sheet.
• the non-oxide ceramic particles function as conductive particles to impart conductivity to the coating film.
• the anti-rust pigment imparts corrosion resistance to the surface-treated metal sheet.
• the surface-treated metal sheet described in Patent Document 1 has excellent adhesion, weldability, and corrosion resistance of the electrodeposition coating film.
• the surface-treated metal plate described in Patent Document 1 has room for improvement in terms of manufacturing costs. That is, the surface-treated metal plate described in Patent Document 1 uses expensive non-oxide ceramic particles as conductive particles. This significantly increases the manufacturing cost of the surface-treated metal plate, undermining the cost benefits of reducing the use of secondary rust-preventing materials.
• the object of the present invention is to provide a surface-treated metal sheet that can be resistance-welded and electro-deposition-coated, has excellent corrosion resistance, and can be manufactured without using non-oxide ceramic particles, i.e., does not contain non-oxide ceramic particles.
• Another object of the present invention is to provide an automobile component having the surface-treated metal sheet, i.e., an automobile component including a surface-treated metal sheet that can be resistance-welded and electro-deposition-coated, has excellent corrosion resistance, and does not contain non-oxide ceramic particles.
• the present invention relates to the following surface-treated metal sheets and automotive components.
• a surface-treated metal sheet comprising a metal sheet and a coating film having a thickness of 0.5 to 5.0 ⁇ m disposed on a surface of the metal sheet, the coating film containing a binder resin, doped oxide particles, and an anti-rust pigment, the content of the doped oxide particles being 5 to 20 vol % of the coating film, the content of the anti-rust pigment being 20 to 50 vol % of the coating film, and a value (B/A) of a ratio of an average particle diameter (B) of the doped oxide particles to an average particle diameter (A) of the anti-rust pigment being 0.75 to 4.00.
• the doped oxide particles include at least one selected from the group consisting of zinc oxide particles doped with Al, Ga or In, tin oxide particles doped with P, Sb or As, indium oxide particles doped with Sn or Ge, titanium oxide particles coated with zinc oxide doped with Al, Ga or In, titanium oxide particles coated with tin oxide doped with P, Sb or As, and titanium oxide particles coated with indium oxide doped with Sn or Ge.
• the anti-rust pigment has an average particle size of 0.5 to 4.0 ⁇ m.
• the anti-rust pigment comprises at least one selected from the group consisting of a phosphate compound, a silicate compound, amorphous silica, and a vanadate compound.
• the binder resin is a water-soluble or water-dispersible aqueous resin.
• the binder resin is an epoxy resin.
• the coating film does not contain any of non-oxide ceramic particles, iron alloy particles, and stainless steel particles.
• An automobile component including a painted metal sheet, the painted metal sheet having the surface-treated metal sheet according to any one of [1] to [8], a chemical conversion coating layer disposed on a surface of the coating film, and an electrodeposition coating film disposed on the surface of the chemical conversion coating layer.
• the present invention provides a surface-treated metal sheet that can be resistance-welded and electrocoated, has excellent corrosion resistance, and can be manufactured more cheaply than conventional methods, as well as an automotive component having the same.
• FIG. 1 is a schematic diagram showing a cross section of a surface-treated metal sheet according to one embodiment of the present invention.
• FIG. 2A is a schematic diagram showing a cross-section of a coating film when the ratio of average particle sizes is within a predetermined range
• FIG. 2B is a schematic diagram showing a cross-section of a coating film when the ratio of average particle sizes is outside the predetermined range.
• FIG. 3A is a backscattered electron image (composition image) of a cross section of a coating film of a surface-treated metal sheet according to one embodiment of the present invention
• FIGS. 3B to 3G are element mapping images of various elements in the same field of view.
• FIG. 4A is a backscattered electron image (composition image) of the cross section of the coating of a surface-treated metal sheet for comparison
• FIGS. 4B to 4G are element mapping images of various elements in the same field of view.
• FIG. 5 is a schematic diagram showing a cross section of a coated metal sheet according to one embodiment of the present invention.
• a numerical range expressed using “ ⁇ ” means a range that includes the numerical values written before and after " ⁇ " as the lower and upper limits.
• the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages.
• a surface-treated metal sheet according to an embodiment of the present invention includes a metal sheet and a coating film disposed on a surface of the metal sheet.
• the coating film is disposed on at least one main surface of the metal sheet and includes a binder resin, doped oxide particles, and an anti-rust pigment.
• FIG. 1 is a schematic diagram showing a cross section of a surface-treated metal plate according to one embodiment of the present invention.
• the surface-treated metal plate 100 has a metal plate 110 and a coating film 120 disposed on one side of the metal plate 110.
• the coating film 120 contains a binder resin 122, doped oxide particles 124, and an anti-rust pigment 126.
• Metal plate The type of metal plate is not particularly limited and can be appropriately selected depending on the application. Examples of materials for the metal plate include steel (iron-based alloy), aluminum, aluminum alloy, magnesium, and magnesium alloy.
• the steel sheet may be an ordinary steel sheet, or a special steel sheet containing added elements such as chromium. However, when press forming, it is preferable that the steel sheet is one in which the type and amount of added elements and the metal structure are appropriately controlled so as to have the desired forming process followability.
• the steel sheet may be a plated steel sheet. Examples of plated steel sheets include zinc-based plated steel sheets and aluminum-based plated steel sheets.
• Examples of zinc-based plating layers of zinc-based plated steel sheets include a plating layer made of zinc; an alloy plating layer of zinc and at least one selected from the group consisting of aluminum, cobalt, tin, nickel, iron, chromium, titanium, magnesium and manganese; and various zinc-based alloy plating layers containing other metallic elements or nonmetallic elements (e.g., a quaternary alloy plating layer of zinc, aluminum, magnesium and silicon).
• the alloy components other than zinc are not particularly limited.
• These zinc-based plating layers may further contain small amounts of different metallic elements or impurities such as cobalt, molybdenum, tungsten, nickel, titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, arsenic, etc., or may contain inorganic substances such as silica, alumina and titania.
• Examples of the aluminum-based plating layer of the aluminum-based plated steel sheet include a plating layer made of aluminum; an alloy plating layer of aluminum and at least one selected from the group consisting of silicon, zinc, and magnesium (e.g., an alloy plating layer of aluminum and silicon, an alloy plating layer of aluminum and zinc, a ternary alloy plating layer of aluminum, silicon, and magnesium).
• Zinc-plated steel sheets and aluminum-plated steel sheets may be multi-layer plated steel sheets in combination with other types of plating layers (e.g., iron plating layers, iron and phosphorus alloy plating layers, nickel plating layers, cobalt plating layers, etc.).
• plating layers e.g., iron plating layers, iron and phosphorus alloy plating layers, nickel plating layers, cobalt plating layers, etc.
• the method for forming the plating layer is not particularly limited.
• electroplating, electroless plating, hot-dip plating, vapor deposition plating, dispersion plating, etc. can be used to form the plating layer.
• the plating layer can be formed either continuously or batchwise. After the plating layer is formed, it may be subjected to treatments such as zero spangle treatment for uniform appearance, annealing treatment for modifying the plating layer, and temper rolling for adjusting the surface condition or material.
• the coating film is disposed on at least one of the main surfaces (i.e., at least one surface) of the above-mentioned metal plate.
• the "main surfaces” refer to the two relatively large surfaces (the front surface and the back surface) of the metal plate.
• the coating film may be formed on both sides (both main surfaces) of the metal plate, or only on one side (one main surface) of the metal plate.
• the coating film may be formed only on a part of the surface of the metal plate, or may be formed on the entire surface of the metal plate.
• the coating film contains a binder resin, doped oxide particles, and an anti-rust pigment.
• the coating film may contain other additives, etc., as necessary.
• the binder resin functions as a binder that binds each component in the coating film.
• the binder resin may be a water-soluble or water-dispersible aqueous resin that dissolves or disperses in water, or a solvent-based resin that dissolves or disperses in an organic solvent. From the viewpoint of production cost and environmental compatibility, the binder resin is preferably an aqueous resin.
• water-based resin is not particularly limited.
• water-based resins include water-soluble or water-dispersible resins such as epoxy resins, urethane resins, polyester resins, acrylic resins, phenolic resins, and mixed resins of two or more of these resins.
• the number average molecular weight (Mn) of the epoxy resin is not particularly limited, but is preferably 1400 to 20,000, more preferably 2,000 to 10,000, and particularly preferably 2,000 to 4,000. That is, the number average molecular weight (Mn) of the epoxy resin is preferably 1400 or more as a lower limit, and more preferably 2,000 or more.
• the number average molecular weight (Mn) of the epoxy resin is preferably 20,000 or less as an upper limit, more preferably 10,000 or less, and particularly preferably 4,000 or less.
• the number average molecular weight of the epoxy resin be 1400 to 20,000, the crosslinking reaction can proceed sufficiently when the epoxy resin is crosslinked, thereby improving the corrosion resistance of the surface-treated metal sheet.
• the crosslink density of the coating film can be prevented from becoming too high, and the workability of the coating film can be maintained.
• the number average molecular weight (Mn) of the resin refers to the number average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).
• the glass transition temperature (Tg) of the epoxy resin is not particularly limited, but may be, for example, 120°C or lower, may be 115°C or lower, or may be 110°C or lower.
• the glass transition temperature (Tg) of the epoxy resin is, for example, 50°C or higher, may be 55°C or higher.
• the glass transition temperature (Tg) of the epoxy resin may be 50 to 120°C.
• the glass transition temperature (Tg) can be measured, for example, using a thermal analyzer TMA7100 (Hitachi High-Tech Science Corporation).
• the acid value of the epoxy resin is not particularly limited, but is, for example, 0 to 30 mgKOH/g.
• the acid value means the acid value of the solid content, and can be measured in accordance with the provisions of JIS K 0070.
• the epoxy resin is preferably in the form of an emulsion with an emulsion particle size of 10 to 100 nm (preferably 20 to 60 nm). If the emulsion particle size is too small, the production costs may increase. On the other hand, if the emulsion particle size is too large, the gaps between the emulsion particles may become large when the emulsion is made into a coating film, which may reduce the barrier properties of the coating film.
• the type of epoxy resin is not particularly limited.
• the epoxy resin may be a hydroxyl-containing epoxy resin (including modified hydroxyl-containing epoxy resin).
• epoxy resins include a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst as necessary; bisphenol-type epoxy resins such as bisphenol A type and bisphenol F type; and novolac-type epoxy resins.
• modified epoxy resins include modified epoxy resins such as acrylic-modified epoxy resins, urethane-modified epoxy resins, and amine-modified epoxy resins.
• an acrylic-modified epoxy resin can be prepared by reacting the bisphenol-type epoxy resin or the novolac-type epoxy resin with a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid.
• a urethane-modified epoxy resin can be prepared by reacting the bisphenol-type epoxy resin or the novolac-type epoxy resin with a polyisocyanate compound.
• the number average molecular weight (Mn) of the polyester resin is not particularly limited, but is preferably 10,000 to 30,000. If the number average molecular weight of the polyester resin is less than 10,000, it may be difficult to ensure sufficient processability. On the other hand, if the number average molecular weight of the polyester resin exceeds 30,000, the adhesion between the coating film and the electrodeposition coating film formed thereon may decrease. In addition, when crosslinking is performed using a curing agent such as melamine, the crosslinking reaction may not proceed sufficiently, resulting in a decrease in the performance of the coating film.
• a curing agent such as melamine
• the urethane resin is preferably in the form of an emulsion with an emulsion particle size of 10 to 100 nm (preferably 20 to 60 nm). If the emulsion particle size is too small, the cost may be high. On the other hand, if the emulsion particle size is too large, the gaps between the emulsions may become large when the coating is formed, and the barrier properties of the coating may decrease.
• urethane resins include polyether-based urethane resins, polycarbonate-based urethane resins, and polyester-based urethane resins. These may be used alone or in combination.
• solvent-based resins examples include epoxy resins, polyester resins, urethane resins, acrylic resins, and mixed resins of two or more of these resins.
• the binder resin may be a cross-linked resin having a cross-linked structure, or a non-cross-linked resin having no cross-linked structure. From the viewpoint of low-temperature film formation of the coating film, it is preferable that the binder resin be a non-cross-linked resin.
• a water-soluble crosslinking agent is preferred as the crosslinking agent (hardening agent) that imparts a crosslinked structure to the binder resin.
• the crosslinking agent is preferably melamine, isocyanate, or the like.
• the amount of crosslinking agent added is not particularly limited, but is preferably 5 to 30 parts by mass per 100 parts by mass of resin solids. If the amount of crosslinking agent added is less than 5 parts by mass, the crosslinking reaction with the resin may not proceed sufficiently, resulting in insufficient performance of the coating film. On the other hand, if the amount of crosslinking agent added is more than 30 parts by mass, the crosslinking reaction may proceed too far, causing the coating film to become excessively hard and reducing processability.
• the content of the binder resin is not particularly limited, but is preferably 20 to 80% by mass relative to the coating film (total solid content of the coating film). If the content of the binder resin is less than 20% by mass, the function as a binder is not expressed, the cohesive force of the coating film is reduced, and the adhesion of the coating film is reduced or the coating film is prone to cohesive failure. If the content of the binder resin exceeds 80% by mass, the ratio of the pigment components (e.g., doped oxide particles and rust-preventive pigments) contained in the coating film is reduced, and it may be difficult to achieve both electrical conductivity, corrosion resistance and adhesion.
• the content of the binder resin is not particularly limited, but is preferably 20 to 80% by mass relative to the coating film (total solid content of the coating film). If the content of the binder resin is less than 20% by mass, the function as a binder is not expressed, the cohesive force of the coating film is reduced, and the adhesion of the coating film is reduced or the coating film is
• the content of the binder resin is more preferably 25 to 70% by mass relative to the coating film (total solid content of the coating film), and even more preferably 30 to 60% by mass. That is, the lower limit of the content of the binder resin is 20% by mass or more relative to the coating film (total solid content of the coating film), preferably 25% by mass or more, and more preferably 30% by mass or more.
• the upper limit of the binder resin content is 80% by mass or less, preferably 70% by mass or less, and more preferably 60% by mass or less, relative to the coating film (total solid content of the coating film).
• the binder resin content is calculated by the following mass spectrometry.
• a sample is prepared by scraping off the coating from the surface-treated metal plate, and the obtained sample is analyzed based on pyrolysis gas chromatography mass spectrometry (GC-MS). Specifically, a certain amount of polystyrene is added to the obtained sample as a standard substance, and the sample is pyrolyzed by heating to 600°C in a GC-MS device (for example, Agilent's GC system "7890B"). The decomposition products obtained by pyrolysis are analyzed by GC-MS and peak analysis is performed to identify the type and amount of the decomposition products.
• GC-MS pyrolysis gas chromatography mass spectrometry
• the amount of binder resin can be determined by comparing the peak area of the styrene monomer corresponding to the known mass (certain amount) of polystyrene added as a standard substance with the peak area of all the remaining peaks corresponding to the binder resin from the analyzed peaks.
• the amount of binder resin in the coating can be obtained by calculating the ratio of the amount of binder resin to the mass of the scraped sample (coating).
• the ratio of the total amount of the epoxy resin, the urethane resin, and the polyester resin to the entire binder resin is preferably 50% or more, more preferably more than 50%, and particularly preferably 60% by volume or more, from the viewpoint of adhesion to the metal plate and retention of the pigment component.
• the binder resin may be composed of a combination of an epoxy resin, a urethane resin, and a polyester resin. In other words, the total content of the epoxy resin, the urethane resin, and the polyester resin in the binder resin may be 100%.
• the doped oxide particles are particles whose surface is composed of a metal oxide containing a doping element (impurity).
• the doped oxide particles are conductive and impart conductivity to the coating film. Since the surface-treated steel sheet according to the present embodiment contains doped oxide particles in the coating film, it can be subjected to resistance welding and electrodeposition coating even if the coating film does not contain other conductive particles such as non-oxide ceramic particles, iron alloy particles, or stainless steel particles.
• a chemical conversion treatment is often performed before painting to form a chemical conversion treatment layer.
• a typical example of such a chemical conversion treatment layer is an acid chloride layer such as a phosphate film.
• the chemical conversion treatment liquid for forming such an acid chloride layer is acidic (e.g., pH 2 to 3), and the doped oxide particles have the property of dissolving in an acidic chemical conversion treatment liquid.
• the surface-treated steel sheet according to the present embodiment is chemically treated using an acidic chemical conversion treatment liquid
• the doped oxide particles in the coating surface layer dissolve, and the pH in the vicinity increases, causing the components of the chemical conversion treatment liquid (e.g., acid chlorides such as phosphates) to precipitate and grow in the areas where the doped oxide particles have dissolved.
• the components of the chemical conversion treatment liquid grow in a wedge shape so as to protrude from the inside of the coating surface layer to the surface.
• adhesion between the coating film and the coating film is further increased by the anchor effect of the crystals that grow in a wedge shape (for example, crystals of acid chlorides such as phosphates) in addition to the high adhesion provided by the chemical properties of the chemical conversion solution components (see Figure 5).
• the coating also contains an anti-rust pigment.
• this anti-rust pigment can be dissolved by an acidic chemical conversion treatment solution.
• doped oxide particles are included in the coating together with the anti-rust pigment, the doped oxide particles are actively dissolved by the acidic chemical conversion treatment solution, making it difficult for the anti-rust pigment to dissolve. This further improves the corrosion resistance of the surface-treated steel sheet according to this embodiment.
• the metal oxide constituting the doped oxide particles is not particularly limited as long as it can impart electrical conductivity to the coating film, and examples thereof include zinc oxide (ZnO) , tin oxide ( SnO2 ), and indium oxide ( In2O3 ).
• the doped oxide particles may be composed of a metal oxide containing a doping element throughout the particle, or only the surface layer of the particle may be composed of a metal oxide containing a doping element.
• the doped oxide particles may be zinc oxide particles doped with a doping element, tin oxide particles doped with a doping element, or indium oxide particles doped with a doping element.
• the doped oxide particles may also be particles composed of other metal oxides coated with zinc oxide, tin oxide, or indium oxide doped with a doping element. Examples of other metal oxides include titanium oxide (TiO 2 ).
• the doping element an element having a different number of valence electrons from the metal element (e.g., Zn, Sn, or In) contained in the metal oxide is used.
• the metal element e.g., Zn, Sn, or In
• ZnO, valence 2 zinc oxide (ZnO, valence 2)
• Al, Ga, and In, which are group 13 elements having similar valences, are more preferable, and Al and Ga are particularly preferable.
• tin oxide SnO 2 , valence 4
• P, Sb, and As are more preferable, and P and Sb are particularly preferable.
• indium oxide In 2 O 3 , valence 3
• Sn and Ge are more preferable, and Sn is particularly preferable.
• the doped oxide particles include at least one selected from the group consisting of zinc oxide particles doped with Al, Ga or In, tin oxide particles doped with P, Sb or As, indium oxide particles doped with Sn or Ge, titanium oxide particles coated with zinc oxide doped with Al, Ga or In, titanium oxide particles coated with tin oxide doped with P, Sb or As, and titanium oxide particles coated with indium oxide doped with Sn or Ge.
• the content of the doping element is preferably 0.05 to 5 atom % relative to the undoped metal oxide, and more preferably 0.1 to 5 atom %.
• the shape of the doped oxide particles is not particularly limited, but is preferably a nearly spherical shape such as a sphere, pseudo-sphere (e.g., an oblong spheroid, an ellipsoid, a chicken egg, a rugby ball, etc.), or a polyhedron (e.g., a soccer ball (truncated icosahedron), a cube (cube), or the brilliant cut shapes of various gemstones).
• Doped oxide particles with a nearly spherical shape tend to be easily dispersed uniformly throughout the coating film, making it easier to form effective electrical paths that run through the coating film in the thickness direction uniformly throughout the entire coating film, further improving the conductivity of the coating film.
• the ratio (B/A) of the average particle size (B) of the doped oxide particles to the average particle size (A) of the anti-rust pigment is preferably 0.75 to 4.00.
• the average particle size of the doped oxide particles refers to the average primary particle size when the doped oxide particles are present alone in the coating film, and refers to the average secondary particle size representing the particle size of the doped oxide particles when they are aggregated together in the coating film.
• the average particle size of the doped oxide particles is calculated by the following cross-sectional observation. The cross section in the thickness direction of the surface-treated metal sheet is mirror-polished, and the cross section of the coating film is photographed at 5000 times magnification (field of view: 24 ⁇ m ⁇ 18 ⁇ m) with a scanning electron microscope (manufactured by JEOL Ltd., "JSM-7100F", acceleration voltage: 15 kV).
• the obtained backscattered electron image 10 doped oxide particles with relatively large particle sizes are arbitrarily selected.
• the average value of the long side length and short side length measured using image processing software (Image J Ver. 1.54h) is calculated to be the particle size of the particle.
• the arithmetic mean of the particle sizes of the 10 particles is calculated to determine the average particle size.
• the same measurement is performed on 10 backscattered electron images, and the arithmetic mean of each backscattered electron image is taken as the average particle size of the doped oxide particles.
• the content of the doped oxide particles is 5 to 20 volume % relative to the coating film (total solid content of the coating film), preferably 10 to 15 volume %. That is, the lower limit of the content of the doped oxide particles is 5 volume % or more relative to the coating film (total solid content of the coating film), preferably 10 volume % or more.
• the upper limit of the content of the doped oxide particles is 20 volume % or less relative to the coating film (total solid content of the coating film), preferably 15 volume % or less. If the content of the doped oxide particles is less than 5 volume %, the coating film may not be given sufficient conductivity. In addition, it becomes difficult to obtain the effect of improving adhesion due to the anchor effect of the chemical conversion treatment layer formed thereon.
• the content of the doped oxide particles exceeds 20 volume %, the adhesion between the coating film and the electrodeposition coating film formed thereon may decrease due to a decrease in the cohesive force of the coating film.
• the content of the doped oxide particles is preferably 15 volume % or less, and may be less than 15 volume %.
• the content of doped oxide particles in the coating is calculated by the following cross-sectional observation.
• the area occupied by the coating and the area occupied by the doped oxide particles are measured using image processing software (Image J). Since the volumetric proportion of each component in the coating roughly corresponds to the area proportion of each component when the coating is observed in cross-section, the measured area proportion of the doped oxide particles is taken as the volume proportion of the doped oxide particles.
• image J image processing software Since the volumetric proportion of each component in the coating roughly corresponds to the area proportion of each component when the coating is observed in cross-section, the measured area proportion of the doped oxide particles is taken as the volume proportion of the doped oxide particles.
• the same measurement is performed on 10 backscattered electron images, and the arithmetic mean value is taken as the content (volume %) of doped oxide particles.
• Phosphate compounds, silicate compounds, amorphous silica, and vanadate compounds can release silicate ions, phosphate ions, vanadate ions, or counter cations of these anions (e.g., alkaline earth metal ions, Zn ions, Al ions, etc.) in aqueous coating compositions or coatings in response to changes in the surrounding environment.
• these ions for example, phosphate ions react with metal ions in the metal plate to form a poorly soluble film and inhibit corrosion.
• Silicate ions form an inorganic polymer layer (barrier layer) on the surface of the metal plate to protect the metal plate from corrosion factors.
• Vanadate ions like phosphate ions, form a film on the surface of the metal plate and have the effect of inhibiting corrosion.
• ions with oxidizing properties such as vanadate ions are thought to further inhibit corrosion because they promote the formation of the poorly soluble film and inorganic polymer layer.
• phosphate compounds include metal salts such as orthophosphoric acid, polyphosphoric acid (single linear polymers of orthophosphoric acid with a degree of polymerization of up to 6, or mixtures of two or more of these), metaphosphoric acid (single cyclic polymers of orthophosphoric acid with a degree of polymerization of 3 to 6, or mixtures of two or more of these), tetrametaphosphoric acid, and hexametaphosphoric acid; phosphorus pentoxide; phosphate minerals such as monetite, torfilite, whitlockite, xenotime, sturcolite, strubite, and orthorite; commercially available complex phosphate pigments such as silica polyphosphate and tripolyphosphate; metal salts such as phytic acid, phosphonic acid (phosphorous acid), and phosphinic acid (hypophosphorous acid); and mixtures of two or more of these.
• metal salts such as orthophosphoric acid, polyphosphoric acid (sing
• the orthophosphates referred to here include their monohydrogen salts (HPO4 2- ) and dihydrogen salts (H 2 PO 4 - ). Furthermore, polyphosphates include their hydrogen salts.
• the cationic species forming the phosphate is not particularly limited, and may be, for example, metal ions such as Co, Cu, Fe, Mn, Nb, Ni, Sn, Ti, V, Y, Zr, Al, Ba, Ca, Mg, Sr, and Zn; or oxocations such as vanadyl, titanyl, and zirconyl.
• the cationic species forming the phosphate are preferably Al, Ca, Mg, Mn, and Ni.
• the phosphate compound may be used alone or in combination of two or more kinds.
• alkali metal phosphate a large amount of alkali metal as a cationic species that forms phosphate is not preferred.
• the product obtained by calcination in the industrial manufacturing process tends to dissolve too much in water.
• a slightly larger amount of alkali metal may be used. Examples of such control include a method of controlling the dissolution rate in water by making the anti-rust pigment coexist with other additives that suppress the solubility in water, or by making the pigment coexist with a highly cross-linked resin or inorganic polymer.
• silicate compounds include alkaline earth metal silicates such as magnesium silicate and calcium silicate; alkali metal silicates such as lithium silicate, sodium silicate, and potassium silicate; and aluminum silicate.
• lithium silicate, sodium silicate, and potassium silicate are, for example, lithium silicate having a molar ratio of silicon oxide (SiO 2 ) to lithium oxide (Li 2 O) of 0.5 ⁇ (SiO 2 /Li 2 O) ⁇ 8, sodium silicate having a molar ratio of silicon oxide (SiO 2 ) to sodium oxide (Na 2 O) of 0.5 ⁇ (SiO 2 /Na 2 O) ⁇ 4, potassium silicate having a molar ratio of silicon oxide (SiO 2 ) to potassium oxide (K 2 O) of 0.5 ⁇ (SiO 2 /K 2 O) ⁇ 4, and hydrates of these silicates.
• lithium orthosilicate Li 4 SiO 4 ; 2Li 2 O.SiO 2
• hexalithium orthodisilicate Li 6 Si 2 O 7 ; 3Li 2 O.2SiO 2
• lithium metasilicate Li 2 SiO 3 ; Li 2 O.SiO 2
• lithium disilicate Li 2 Si 2 O 5 ; Li 2 O.2SiO 2
• tetralithium heptasilicate Li 2 O.7SiO 2
• lithium tetrasilicate Li 2 Si 4 O 9 ; Li 2 O.4SiO 2
• tetralithium nonasilicate 2Li 2 O.9SiO 2
• tetralithium hexadecanosilicate 2Li 2 O.15SiO 2
• sodium orthosilicate Na 4 SiO 4 ; 2Na2O.SiO2
• sodium metasilicate Na 4 SiO 4 ; 2Na2O.SiO2
• amorphous silica examples include amorphous silica having an oil absorption of 100 to 1000 ml/100 g and a specific surface area of 200 to 1000 m 2 /g.
• the oil absorption of silica can be measured according to JIS K 5101-13-2.
• the specific surface area of silica can be measured by the BET method.
• Vanadate compounds are composite compounds in which vanadium has a valence of 0, 2, 3, 4, or 5, or two or more valencies, such as oxides, hydroxides, oxyacid salts of various metals, vanadyl compounds, halides, sulfates, metal powders, etc. These decompose when heated or in the presence of water, and react with coexisting oxygen.
• vanadium metal powder or divalent compounds will eventually change to trivalent, tetravalent, or pentavalent compounds.
• Zero-valent ones, such as vanadium metal powder can be used for the above reasons, but are not practically preferred due to problems such as insufficient oxidation reactions.
• Pentavalent vanadium compounds have vanadate ions and are easily reacted with phosphate ions by heating to form heteropolymers that contribute to rust prevention. Therefore, it is preferable to include a pentavalent vanadium compound as one component.
• vanadium compounds include vanadium(II) compounds such as vanadium(II) oxide and vanadium(II) hydroxide, vanadium(III) compounds such as vanadium(III) oxide, vanadium(IV) compounds such as vanadium(IV) oxide and vanadyl halides, vanadium(V) compounds such as vanadium(V) oxide and vanadium(V) salts (orthovanadates, metavanadates, pyrovanadates, etc. of various metals), or mixtures thereof.
• the preferred metal species constituting the vanadate are the same as those shown for the phosphate.
• alkali metal vanadates When using alkali metal vanadates, the product obtained by calcination in the industrial manufacturing process tends to dissolve too much in water, so as with phosphates, it is not advisable to use large amounts of alkali metal vanadates. However, as with alkali metal phosphates, if the solubility in water can be controlled, there is no problem with using them. The same applies to vanadium halides and sulfates.
• the ratio (B/A) of the average particle size (B) of the doped oxide particles to the average particle size (A) of the anti-rust pigment is preferably 0.75 to 4.00.
• the average particle size of the anti-rust pigment is not particularly limited as long as the above average particle size ratio value is satisfied, but the lower limit is preferably 0.2 ⁇ m or more, more preferably 0.5 ⁇ m or more, and particularly preferably 1.0 ⁇ m or more.
• the upper limit of the average particle size of the anti-rust pigment is preferably 5.0 ⁇ m or less, more preferably 4.0 ⁇ m or less, and particularly preferably 2.0 ⁇ m or less.
• the average particle size of the anti-rust pigment refers to the average primary particle size when the anti-rust pigment is present alone in the coating film, and refers to the average secondary particle size that represents the particle size of the anti-rust pigment when aggregated together in the coating film.
• the average particle size of the anti-rust pigment is calculated by the following cross-sectional observation. In the backscattered electron image obtained in the same manner as the above-mentioned method for measuring the average particle size of the doped oxide particles, 10 anti-rust pigments with relatively large particle sizes are arbitrarily selected. For each particle, the average values of the long side length and short side length measured using image processing software (Image J) are calculated to determine the particle size of the particle.
• Image J image processing software
• the arithmetic mean value of the particle sizes of the 10 particles is calculated to determine the average particle size.
• the same measurement is performed on 10 backscattered electron images, and the arithmetic mean value of each backscattered electron image is determined to be the average particle size of the anti-rust pigment.
• the thickness of the coating film is made small in order to ensure the conductivity of the coating film.
• the content of the rust-preventive pigment is 20 to 50 volume % of the coating film (total solid content of the coating film). If the content of the rust-preventive pigment is less than 20 volume %, the corrosion resistance may be insufficient. If the content of the rust-preventive pigment is more than 50 volume %, the workability of the coating film may decrease and the cohesive force may decrease.
• the content of the rust-preventive pigment is preferably 25 volume % or more, may be 30 volume % or more, or may be more than 30 volume %.
• the content of the rust-preventive pigment is preferably 45 volume % or less.
• the content of the anti-rust pigment in the coating is calculated by the following cross-sectional observation.
• the area occupied by the coating and the area occupied by the anti-rust pigment are measured using image processing software (Image J). Since the volumetric proportion of each component in the coating roughly corresponds to the area proportion of each component when the coating is observed in cross-section, the measured area proportion of the anti-rust pigment is taken as the volume proportion of the anti-rust pigment. Similar measurements are performed on 10 backscattered electron images, and the arithmetic mean value is taken as the content (volume %) of the anti-rust pigment.
• the coating film contains doped oxide particles for imparting electrical conductivity and an anti-rust pigment for imparting corrosion resistance. If the doped oxide particles in the coating film cannot form an effective electrical path penetrating the thickness direction of the coating film, the coating film cannot be imparted with appropriate electrical conductivity. From this viewpoint, in the surface-treated metal sheet according to the present embodiment, the ratio (B/A) of the average particle size (B) of the doped oxide particles to the average particle size (A) of the anti-rust pigment is 0.75 to 4.00, preferably 1.00 or more, and preferably 3.00 or less.
• FIG. 2A is a schematic diagram showing the cross section of a coating film when the average particle size ratio (B/A) is 2.40
• Fig. 2B is a schematic diagram showing the cross section of a coating film when the average particle size ratio (B/A) is 0.42.
• the doped oxide particles 124 can efficiently form an effective electrical path E that penetrates the thickness direction of the coating film 120.
• FIG. 2A when the average particle size ratio (B/A) is within the range of 0.75 to 4, i.e., when the doped oxide particles 124 are somewhat large relative to the anti-rust pigment 126, the doped oxide particles 124 can efficiently form an effective electrical path E that penetrates the thickness direction of the coating film 120.
• FIG. 1 is a schematic diagram showing the cross section of a coating film when the average particle size ratio (B/A) is 2.40
• Fig. 2B is a schematic diagram showing the cross section of a coating film when the average particle size ratio (B/A) is 0.42.
• Figures 3A to 3G are EPMA images of the cross section of the coating of a surface-treated metal sheet when the average particle size ratio (B/A) is 2.00 (corresponding to Figure 2A).
• Figure 3A is a backscattered electron image (composition image) of the cross section of the coating
• Figure 3B is an element mapping image of Fe
• Figure 3C is an element mapping image of Zn
• Figure 3D is an element mapping image of P
• Figure 3E is an element mapping image of Mg
• Figure 3F is an element mapping image of Si
• Figure 3G is an element mapping image of Al.
• Figures 4A to 4G are EPMA images of the cross section of the coating of a surface-treated metal sheet when the average particle size ratio (B/A) is 0.50 (corresponding to Figure 2B).
• Figure 4A is a backscattered electron image (composition image) of the cross section of the coating
• Figure 4B is an element mapping image of Fe
• Figure 4C is an element mapping image of Zn
• Figure 4D is an element mapping image of P
• Figure 4E is an element mapping image of Mg
• Figure 4F is an element mapping image of Si
• Figure 4G is an element mapping image of Al.
• the oxide (ZnO) particles 124 doped with the doping element (Al) are close to both surfaces (both the upper and lower surfaces) of the coating film 120. It is believed that these doped oxide particles 124 function as electrical paths.
• the oxide (ZnO) particles 124 doped with the doping element (Al) are far away from at least one of the surfaces (both the upper and lower surfaces) of the coating film 120. It is highly likely that these oxide particles 124 cannot function as electrical paths.
• the EPMA images were obtained using the following measurement method. As with the SEM measurements described above, the cross section of the coating was observed using an SEM attached to an EPMA device (JXA-iHP200F manufactured by JEOL Ltd., measurement conditions: acceleration voltage 15 kV, irradiation current: 3 x 10-8 A), and the EPMA images were obtained by performing elemental analysis of the elements Fe, Zn, P, Mg, Si, and Al. Note that Figures 3A and 4A show the analysis results of each element superimposed.
• the coating film may further contain other additives, such as well-known additives such as extender pigments, solid lubricants, and leveling agents.
• extender pigments examples include titania and zirconia.
• Solid lubricants can impart excellent lubricity to coating films and improve their powdering resistance.
• solid lubricants include polyolefin waxes or paraffin waxes such as polyethylene wax, synthetic paraffin, natural paraffin, microwax, and chlorinated hydrocarbons; and fluororesin waxes such as polyfluoroethylene resins (e.g., polyethylene tetrafluoride resin), polyvinyl fluoride resin, and polyvinylidene fluoride resin.
• the average particle size of the solid lubricant is not particularly limited, but is preferably 0.05 to 4 ⁇ m. If the average particle size of the solid lubricant is less than 0.05 ⁇ m, the surface concentration of the lubricant tends to increase the area occupied by the lubricant on the surface layer of the coating film, and adhesion between the coating film and the paint film formed thereon may decrease. On the other hand, if the average particle size of the solid lubricant exceeds 4 ⁇ m, the lubricant is likely to fall off the resin coating film, making it difficult to obtain the desired lubricity and causing corrosion resistance to decrease. From the viewpoint of obtaining paint adhesion, corrosion resistance, lubricity, and powdering resistance, the average particle size of the solid lubricant is more preferably 0.1 to 3 ⁇ m, and even more preferably 0.3 to 2 ⁇ m.
• the softening point of the solid lubricant is preferably 100°C to 135°C, more preferably 110°C to 130°C. If the softening point of the solid lubricant is 100°C to 135°C, the lubricity and powdering resistance are further improved.
• the content of the solid lubricant is preferably 0.1 to 10 mass% of the coating film (total solid content of the coating film). If the content of the solid lubricant is less than 0.1 mass%, sufficient lubrication may not be obtained. If the content of the solid lubricant exceeds 10 mass%, the adhesion and corrosion resistance between the coating film and the paint film formed thereon may decrease.
• the content of the solid lubricant is more preferably 0.2 to 5 mass % of the coating film (total solid content of the coating film), and even more preferably 0.5 to 2.5 mass %, from the viewpoints of adhesion between the coating film and the paint film, lubricity, and corrosion resistance.
• the thickness of the coating film is 0.5 to 5.0 ⁇ m from the viewpoint of enabling resistance welding and electrodeposition coating while ensuring corrosion resistance.
• the thickness of the coating film is the thickness of the portion where the doped oxide particles and/or the rust-preventive pigments do not protrude from the surface of the coating film.
• the thickness of the coating film is less than 0.5 ⁇ m, the adhesion and corrosion resistance between the coating film and the electrodeposition coating film formed on its surface may not be sufficiently obtained.
• the thickness of the coating film exceeds 5 ⁇ m, the conductivity of the coating film may decrease, making resistance welding and electrodeposition coating difficult, and the cohesive force of the coating film may decrease.
• the thickness of the coating film is preferably 3.0 ⁇ m or less, and may be less than 3.0 ⁇ m.
• the coating thickness is measured by the following cross-sectional observation.
• 10 locations are arbitrarily selected as measurement points for the coating thickness, with an interval of 5 ⁇ m or more between each.
• the 10 locations may be selected not only from a single image, but also from multiple images measured in different observation regions (fields of view).
• the average value of the coating thickness measured at the 10 locations is calculated using image processing software (Image J) and used as the coating thickness.
• the coating thickness is the length of the coating in the direction perpendicular to the surface of the surface-treated metal sheet.
• the surface of the surface-treated metal sheet referred to here does not mean a microscopic range on the order of a few ⁇ m, but the surface (main surface) that extends across the entire surface-treated metal sheet to be measured.
• the method for forming the coating film is not particularly limited, and a well-known method can be used.
• a composition for forming a coating film is prepared by mixing a binder resin, doped oxide particles, an anti-rust pigment, and other additives as necessary in a solvent.
• the solvent may be water or an organic solvent, but is preferably water in terms of production cost and environmental suitability.
• the composition for forming a coating film is preferably a water-based composition. Then, the composition for forming a coating film is applied to at least one side of a metal plate, and then dried and heated to form a coating film.
• the uses of the surface-treated metal sheet according to the present embodiment are not particularly limited.
• the surface-treated metal sheet and the coated metal sheet according to the present embodiment can be widely used for automobile parts (automobile bodies, chassis parts, etc.), machine parts (casings, etc.), home appliance parts (casings, etc.), building materials (roofs, walls, etc.), etc.
• the surface-treated metal sheet according to the present embodiment conductive doped oxide particles are blended in the coating, the ratio (B/A) of the average particle size (B) of the doped oxide particles to the average particle size (A) of the rust-preventive pigment blended in the coating is set to 0.75 to 4.00, and the thickness of the coating is reduced. Therefore, the conductivity of the coating is improved in the surface-treated metal sheet according to the present embodiment. Therefore, the surface-treated metal sheet according to the present embodiment is suitable not only for resistance welding but also for electrodeposition coating.
• the surface-treated metal sheet according to the present embodiment maintains sufficient corrosion resistance while ensuring the conductivity of the coating.
• the surface-treated metal sheet according to this embodiment doped oxide particles are used as the conductive particles in the coating.
• the surface-treated metal sheet according to this embodiment it is not necessary to use expensive non-oxide ceramic particles as the conductive particles. Therefore, the surface-treated metal sheet according to this embodiment can be manufactured at a lower cost than conventional surface-treated metal sheets that contain non-oxide ceramic particles.
• the automobile component according to this embodiment is an automobile component including a painted metal plate, and the painted metal plate has a surface-treated metal plate according to the embodiment, a chemical conversion coating layer disposed on the surface of the coating film of the surface-treated metal plate, and an electrochemical coating film disposed on the surface of the chemical conversion coating layer.
• the automobile component is, for example, an automobile body component or an undercarriage component.
• FIG. 5 is a schematic diagram showing a cross section of a coated metal sheet according to an embodiment of the present invention (a partially enlarged cross section of an automobile member).
• the coated metal sheet 200 has a metal sheet 110, a coating film 120 disposed on the surface of the metal sheet 110, a chemical conversion treatment layer 210 disposed on the surface of the coating film 120, and an electrodeposition coating film 220 disposed on the surface of the chemical conversion treatment layer 210.
• the chemical conversion treatment layer 210 is a discontinuous layer composed of a large number of acid chloride crystals 212 precipitated on the surface of the coating film 120.
• the surface-treated metal sheet may be formed into a predetermined shape depending on the application.
• multiple surface-treated metal sheets may be joined by welding, adhesives, etc.
• the surface-treated metal sheet according to this embodiment has excellent electrical conductivity of the coating, so defects such as cracks due to welding are unlikely to occur, and a coating film can be formed by electrochemical coating.
• the chemical conversion layer is a layer located on the surface of the coating film and formed by performing a chemical conversion treatment on the coating film surface.
• the chemical conversion layer may be a continuous layer that covers the surface of the surface-treated steel sheet without any gaps, or may be a discontinuous layer that covers the surface of the surface-treated steel sheet intermittently.
• a representative example of such a chemical conversion layer is an acid chloride layer such as a phosphate layer.
• the chemical conversion solution for forming such an acid chloride layer is acidic (e.g., pH 2 to 3), and the doped oxide particles have the property of dissolving in an acidic chemical conversion solution.
• the surface-treated steel sheet according to the present embodiment is chemically treated using an acidic chemical conversion solution
• the doped oxide particles in the coating film surface layer dissolve, and the pH in the vicinity increases, causing components of the chemical conversion solution (e.g., acid chlorides such as phosphates) to precipitate and grow at the locations where the doped oxide particles have dissolved.
• the components of the chemical conversion solution grow in a wedge shape so as to protrude from the inside of the coating film surface layer to the surface. As shown in FIG.
• Examples of the phosphate include crystalline phosphate and amorphous phosphate. From the viewpoint of having wedge-shaped phosphate present in the chemical conversion coating layer, crystalline phosphate is preferred.
• Examples of crystalline phosphates include zinc phosphate (hopite: Zn 3 (PO 4 ) 2.4H 2 O), zinc iron phosphate (phosphophyllite: Zn 2 Fe (PO 4 ) 2.4H 2 O), manganese phosphate (heuriolite: Mn 5 ( PO 3 (OH)) 2 (PO 4 ) 2.4H 2 O), manganese iron phosphate ((Mn 1-x Fe x ) 5 H 2 (PO 4 ) 4.4H 2 O, where x represents that the iron-based metallic material is etched during the chemical conversion treatment and the iron component is contained in the coating; 0 ⁇ x ⁇ 1), and calcium zinc phosphate (scholzite: CaZn 2 (PO 4 ) 2.2H 2 O).
• Examples of amorphous phosphates include iron phosphat
• the chemical conversion layer may also be composed of a component other than phosphate.
• the chemical conversion layer may contain a salt of at least one selected from iron, titanium, zirconium, hafnium, indium, tin, bismuth, vanadium, nickel, cerium, molybdenum, and tungsten with nitrate ions, sulfate ions, fluorine ions, complex fluorine ions, or carbonate ions.
• salts include titanium oxide, zirconium oxide, hafnium oxide, indium oxide, tin oxide, bismuth oxide, vanadium oxide, nickel oxide, cerium oxide, molybdenum oxide, tungsten oxide, iron sulfide, zirconium fluoride, titanium fluoride, hafnium fluoride, and indium fluoride.
• the thickness of the chemical conversion layer is not particularly limited, but is preferably 0.01 ⁇ m to 3 ⁇ m, more preferably 0.03 ⁇ m to 2 ⁇ m, and even more preferably 0.05 ⁇ m to 1 ⁇ m. If the chemical conversion layer contains a crystalline salt, the chemical conversion layer will have irregularities due to the crystals, so it is not appropriate to discuss the thickness. However, attention can be paid to the crystal diameter of the chemical conversion layer.
• the crystal diameter of the crystalline phosphate is preferably 0.10 to 5 ⁇ m, more preferably 0.30 to 4 ⁇ m, and even more preferably 0.50 to 3 ⁇ m.
• the electrodeposition coating film is disposed on the surface-treated metal plate via a chemical conversion coating layer.
• the electrodeposition coating film is a film formed by electrodeposition coating.
• the coating film may be a single layer or a multi-layer (for example, a coating film consisting of an undercoat layer, an intermediate coat layer, and a top coat layer).
• the coated metal plate according to the present embodiment may be coated by other coating treatments such as powder coating and solvent coating in addition to electrodeposition coating.
• the automotive component according to this embodiment can be manufactured, for example, by a step (first step) of forming a chemical conversion coating layer on the surface of a coating film of a surface-treated metal plate, and a step (second step) of forming an electrodeposition coating film on the surface of the chemical conversion coating layer.
• the above-mentioned surface-treated metal sheet is prepared.
• the surface-treated metal sheet may be formed into a predetermined shape.
• the surface-treated metal sheet may be formed using a known forming technique, such as cutting or press forming.
• multiple surface-treated metal sheets or plates may be joined by welding (e.g., spot welding, etc.).
• the surface-treated metal sheet may be subjected to known pretreatment, such as degreasing and surface adjustment.
• a chemical conversion treatment is performed on the surface-treated metal sheet to form a chemical conversion layer on the surface of the coating film.
• the chemical conversion solution and treatment conditions used in the chemical conversion treatment can be appropriately selected depending on the state and composition of the chemical conversion layer to be formed.
• the chemical conversion solution can be an acidic aqueous solution containing phosphate ions as anions and at least one selected from zinc, calcium, and manganese as cations.
• the acidic aqueous solution further contains transition metal ions such as nickel and cobalt; oxidizing agents such as nitric acid and nitrous acid; and etching components such as fluorine ions and complex fluorine ions.
• transition metal ions such as nickel and cobalt
• oxidizing agents such as nitric acid and nitrous acid
• etching components such as fluorine ions and complex fluorine ions.
• Examples of commercially available acidic aqueous solutions for phosphate treatment include “Palbond 860”, “Palbond L3020”, “Palphos M1A”, “Palphos M5", “Palbond 880”, “Palbond SX35”, “Palbond L47”, and “Ferricote 7" manufactured by Nippon Parkerizing Co., Ltd.
• the pH of the above-mentioned chemical conversion solution is not particularly limited, but is preferably 1.0 to 5.0, and more preferably 2.0 to 4.0.
• the temperature of the above chemical conversion treatment solution during the chemical conversion treatment is not particularly limited, but is preferably 30°C to 120°C, more preferably 35°C to 110°C, and even more preferably 40°C to 100°C.
• the time of the chemical conversion treatment is not particularly limited, and can be appropriately selected depending on the desired adhesion amount of the chemical conversion treatment layer to be formed.
• the chemical conversion solution may be, for example, an acidic aqueous solution containing phosphate ions as anions and at least one selected from iron, tin, zirconium, titanium, and hafnium as cations.
• the acidic aqueous solution further contains transition metal ions such as nickel and cobalt; oxidizing agents such as nitric acid and nitrous acid; and etching components such as fluorine ions and complex fluorine ions.
• an acidic aqueous solution for phosphate treatment that appropriately combines the types and contents of the above-mentioned anions and cations
• a commercially available one can be used as is.
• Examples of commercially available acidic aqueous solutions for phosphate treatment include "Palphos 1077", “Palphos 525T”, and “Palphos K5100” manufactured by Nippon Parkerizing Co., Ltd.
• the pH of the above-mentioned chemical conversion solution is not particularly limited, but is preferably 1.0 to 5.0, and more preferably 2.0 to 4.0.
• the temperature of the chemical conversion solution during chemical conversion is not particularly limited, and is preferably 10°C to 100°C, more preferably 15°C to 80°C, and even more preferably 20°C to 60°C.
• the time of chemical conversion is not particularly limited, and can be appropriately selected depending on the desired adhesion amount of the chemical conversion layer to be formed.
• the solids concentration of each component is shown as the ratio (unit: volume %) of the solids (non-volatile content) of each component to the solids (non-volatile content) of the entire aqueous composition.
• Anti-rust pigment PAM Mg-containing aluminum dihydrogen tripolyphosphate (K-WHITE G105, Teika Co., Ltd.)
• PA Aluminum dihydrogen tripolyphosphate (K-WHITE K105, Teika Corporation)
• Si silicon dioxide (amorphous silica) (Snowtex (registered trademark) ZL, Nissan Chemical Industries, Ltd.)
• V Vanadium pentoxide (Kanto Chemical Co., Ltd.)
• the contents (volume %) of the doped oxide particles and the rust-preventive pigment in the coating were calculated by the following procedure, and the values were substantially the same as the concentrations (volume %) of the doped oxide particles and the rust-preventive pigment shown in Tables 1 to 4.
• the backscattered electron images obtained in the same manner as in the above-mentioned method for measuring the average particle size of the doped oxide particles were used to measure the areas occupied by the coating, the doped oxide particles, and the rust-preventive pigment using image processing software (Image J).
• the measured area ratio of the doped oxide particles and the area ratio of the rust-preventive pigment were taken as the volume ratio of the doped oxide particles and the volume ratio of the rust-preventive pigment, respectively. Similar measurements were performed on 10 backscattered electron images, and the arithmetic mean values were taken as the content (volume %) of the doped oxide particles and the content (volume %) of the rust-preventive pigment.
• the aqueous compositions were applied to metal sheets using a bar coater so as to obtain the compositions shown in Tables 1 to 4, and the sheets were dried using an oven under conditions in which the maximum temperature reached was 140° C. and maintained for 8 seconds to form coating films.
• the thickness of the coating film was adjusted by diluting the aqueous composition and the number of the bar coater so as to obtain the values shown in Tables 1 to 4.
• the thickness of the coating film was measured by the following procedure. In the multiple images (backscattered electron images) obtained by the above-mentioned SEM measurement, 10 locations were selected as the measurement points for the film thickness, with an interval of 5 ⁇ m or more between each. The average value of the film thicknesses measured at the 10 locations was calculated using image processing software (Image J), and this was taken as the film thickness of the coating film.
• Image J image processing software
• a uniform electrodeposition coating film was formed. Furthermore, if an electrodeposition coating film was not formed, the surface of the underlying metal plate was visually recognized.
• the surface of the metal plate can be identified as a metal plate by metallic gloss, spangle pattern, etc.
• the electrodeposition coating film was subjected to salt spray for 80 hours, and then an adhesion test was performed by the cross-cut method in accordance with JIS K 5600-5-6 (2016). After that, the ratio of the area of the part where the electrodeposition coating film peeled off to the test area of each surface-treated metal plate (peel rate of the coating film (%)) was measured. From the peel rate of the coating film, the adhesion of the electrodeposition coating film was evaluated according to the following criteria. When the evaluation result was "C", it was determined that it was unsuitable for electrodeposition coating. A: The peeling rate was less than 5%. B: The peeling rate was 5% or more and less than 15%. C: The peeling rate was 15% or more.
• sample Nos. 1 to 44 which are surface-treated metal sheets corresponding to the examples, are superior in appearance and adhesion of the electrocoat coating film, as well as corrosion resistance, compared to sample Nos. 45 to 53, which are surface-treated metal sheets corresponding to the comparative examples.
• resistance welding could be performed appropriately on the surface-treated metal sheets of sample Nos. 1 to 44.
• the surface-treated metal sheets and painted metal sheets of the present invention are useful in a variety of applications, such as automotive components.

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• Other Surface Treatments For Metallic Materials (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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• 2024
  • 2024-04-17 KR KR1020257032378A patent/KR20250165605A/ko active Pending
  • 2024-04-17 CN CN202480016423.4A patent/CN120813728A/zh active Pending
  • 2024-04-17 JP JP2025515270A patent/JP7817651B2/ja active Active
  • 2024-04-17 WO PCT/JP2024/015309 patent/WO2024219435A1/ja not_active Ceased
• 2025
  • 2025-09-11 MX MX2025010726A patent/MX2025010726A/es unknown

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