Surface conditioner, chromium-free surface treatment method, and surface-treatment-film-including metal base material

Abstract

The present disclosure addresses the problem of providing a surface conditioner with which it is possible to achieve desired adhesion of a surface treatment film to a metal base material. A surface conditioner according to an embodiment of the present disclosure is used for surface conditioning in a stage prior to surface treatment being performed on a metal base material. The surface conditioner contains an iron (III) compound, a molybdenum compound, and a chelating agent. The iron element content of the surface conditioner is 0.02-1.0 mass%, and the molybdenum element content of the surface conditioner is 0.05-2.5 mass%. The pH of the surface conditioner is 10 or higher.

Description

Surface conditioner, chromium-free surface treatment method, and metal substrate containing surface treatment film

[0001] The present invention relates to a surface conditioner, a chromium-free surface treatment method, and a metal substrate having a surface treatment film.

[0002] Conventionally, in order to improve the corrosion resistance of metals, a method of treating the surface of metals with a surface treatment agent containing a chromium compound such as a hexavalent chromium compound or a trivalent chromium compound has been known. In recent years, due to trends in environmental regulations, various chromium-free surface treatment agents that do not contain chromium compounds have been developed.

[0003] The surface of a metal to be surface treated may have an oxide film or other metal elements unevenly distributed. In such cases, applying a surface treatment agent to the metal surface makes it difficult to achieve a uniform application. Therefore, prior to surface treatment of the metal, surface conditioning is performed (see, for example, Patent Document 1).

[0004] Special Publication No. 43-012974

[0005] Patent Document 1 discloses a technology for forming a protective film on the surface of zinc and zinc alloys using an alkaline aqueous solution. Cobalt and other elements are used in the alkaline aqueous solution, but the use of cobalt may not be desirable due to environmental regulations. As mentioned above, in recent years, various surface treatment agents have been developed, including not only surface treatment agents containing chromium compounds but also chromium-free surface treatment agents. Therefore, there has been a need for the development of a surface conditioner that can achieve favorable adhesion of the surface treatment film formed by the surface treatment agent to the metal substrate.

[0006] The present invention has been made in view of the above, and an object of the present invention is to provide a surface conditioner that can achieve favorable adhesion of a surface treatment film to a metal substrate.

[0007] (1) The present disclosure relates to a surface conditioner used for surface conditioning of a metal substrate prior to surface treatment, the surface conditioner comprising an iron (III) compound, a molybdenum compound, and a chelating agent, wherein the iron content in the surface conditioner is 0.02% by mass or more and 1.0% by mass or less, the molybdenum content in the surface conditioner is 0.05% by mass or more and 2.5% by mass or less, and the pH of the surface conditioner is 10 or more.

[0008] (2) The surface conditioner according to (1), wherein the iron (III) compound contains iron (III) nitrate, the molybdenum compound contains molybdate, and the chelating agent contains gluconic acid.

[0009] (3) The present disclosure also relates to a chromium-free surface treatment method for a metal substrate, the chromium-free surface treatment method including a degreasing step, a first water-washing step, a surface conditioning step, and optionally a second water-washing step, and a surface treatment step, in which the surface conditioning step is carried out using the surface conditioner according to (1) or (2).

[0010] (4) The chromium-free surface treatment method according to (3), wherein the surface treatment agent used in the surface treatment step contains an organic phosphonic acid resin, a phosphoric acid compound, and a complex fluoride, the organic phosphonic acid resin is a copolymer containing a segment derived from a carboxyl group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, and the phosphonic acid group-containing monomer is vinylphosphonic acid or a phosphonic acid group-containing acrylic acid ester.

[0011] (5) The chromium-free surface treatment method according to (4), wherein the surface treatment agent further contains a manganese compound.

[0012] (6) The chromium-free surface treatment method according to (4) or (5), wherein the surface treatment agent further contains a vanadium compound.

[0013] (7) The chromium-free surface treatment method according to any one of (4) to (6), wherein the complex fluoride is hydrosilicofluoric acid.

[0014] (8) The chromium-free surface treatment method according to any one of (5) to (7), wherein the manganese content ratio of the manganese compound to the organic phosphonic acid resin (manganese / organic phosphonic acid resin) is 0.05 or more and 2.0 or less.

[0015] (9) The present disclosure also relates to a metal substrate having a surface treatment film, the metal substrate having a film of the surface conditioner according to any one of (1) to (8) and a film of a surface treatment agent, wherein the surface treatment agent comprises an organic phosphonic acid resin, a phosphoric acid compound, and a complex fluoride, the organic phosphonic acid resin is a copolymer comprising a segment derived from a carboxyl group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, and the phosphonic acid group-containing monomer is vinylphosphonic acid or a phosphonic acid group-containing acrylic acid ester.

[0016] (10) The metal substrate with a surface treatment film according to (9), wherein the surface treatment agent further contains a manganese compound and a vanadium compound.

[0017] (11) The metal substrate with a surface treatment film according to (9) or (10), which has a coating film on the film of the surface treatment agent.

[0018] According to the present invention, it is possible to provide a surface conditioner that can achieve preferable adhesion of a surface treatment film to a metal substrate.

[0019] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the description of the following embodiments.

[0020] <Surface Conditioner> The surface conditioner according to this embodiment is used for surface conditioning of a metal substrate, which is a preliminary step in the surface treatment of the metal substrate. The surface conditioner according to this embodiment contains an iron (III) compound, a molybdenum compound, and a chelating agent. The pH of the surface conditioner is 10 or higher.

[0021] (Iron (III) Compound) When an iron (III) compound is contained in a surface conditioner, iron elements derived from the iron (III) compound are precipitated on the surface of a metal substrate prepared with the surface conditioner. The precipitated iron elements serve as reaction sites when a surface treatment film is formed by surface treatment, and a composite metal salt film can be efficiently formed from components derived from the metal substrate and components derived from the surface treatment agent that are eluted from the surface of the metal substrate during surface treatment. This improves the chemical bonding strength between the metal substrate surface and the surface treatment film, thereby improving adhesion. In addition, a fine and dense surface treatment film can be formed in a short time.

[0022] The content of iron element in the surface conditioner is 0.02 mass% or more and 1.0 mass% or less. The content of iron element is preferably 0.03 mass% or more and 0.5 mass% or less. If the content of iron element is less than 0.03 mass%, a sufficient amount of iron element cannot be precipitated on the surface of the metal substrate, and the number of reaction sites during surface treatment is reduced, so the effect of improving adhesion is not sufficiently obtained. On the other hand, if the content of iron element exceeds 0.5 mass%, a large amount of iron element is precipitated on the surface of the metal substrate, and the surface of the metal substrate is excessively coated with iron element, and the components derived from the metal substrate that are eluted during surface treatment are reduced, so a surface treatment film with an appropriate composition cannot be obtained, and the effect of improving adhesion is not sufficiently obtained.

[0023] In this specification and claims, the term "in the surface conditioner" refers to the mass of the entire surface conditioner. In this standard, not only the solid content but also the volatile content in the surface conditioner is included in the mass of the entire surface conditioner.

[0024] The iron (III) compound preferably includes iron (III) nitrate. Iron (III) nitrate may be a hydrate, for example, Fe(NO ３ ) ３ ・9H ２ The iron(III) compound may contain a compound other than iron(III) nitrate, such as iron(III) sulfate. It is preferable that the iron(III) compound does not contain iron(III) chloride.

[0025] (Molybdenum Compound) When a molybdenum compound is contained in a surface conditioner, molybdenum element derived from the molybdenum compound is precipitated on the surface of a metal substrate prepared with the surface conditioner, similar to an iron (III) compound. The precipitated molybdenum element serves as a reaction site when a surface treatment film is formed by surface treatment, and a composite metal salt film can be efficiently formed from components derived from the metal substrate and components derived from the surface treatment agent that are eluted from the surface of the metal substrate during surface treatment. This improves the chemical bonding strength between the metal substrate surface and the surface treatment film, thereby improving adhesion. Furthermore, a fine and dense surface treatment film can be formed in a short time. The coexistence of a molybdenum compound and an iron (III) compound in the surface conditioner of the present invention further improves adhesion between the metal substrate surface and the surface treatment film.

[0026] The content of molybdenum element in the surface conditioner is 0.05% by mass or more and 2.5% by mass or less. The content of molybdenum element is preferably 0.06% by mass or more and 1.0% by mass or less. If the content of molybdenum element is less than 0.06% by mass, a sufficient amount of molybdenum element cannot be precipitated on the surface of the metal substrate, resulting in fewer reaction sites during surface treatment, and therefore, the effect of improving adhesion cannot be sufficiently obtained. On the other hand, if the content of molybdenum element exceeds 1.0% by mass, a large amount of molybdenum element is precipitated on the surface of the metal substrate, resulting in the surface of the metal substrate being excessively coated with molybdenum element, and therefore, fewer components derived from the metal substrate are eluted during surface treatment, making it impossible to obtain a surface treatment film with an appropriate composition, and therefore, the effect of improving adhesion cannot be sufficiently obtained.

[0027] The molybdenum compound preferably contains a molybdate. Specific examples of the molybdate include, but are not limited to, sodium molybdate and ammonium molybdate (VI). The molybdate may be a hydrate. The molybdenum compound may contain a compound other than the molybdate, such as molybdenum oxide, molybdenum fluoride, molybdenum alkoxide, or molybdenyl acetylacetonate.

[0028] (Chelating Agent) The chelating agent stabilizes the metal elements contained in the surface conditioner. Examples of the chelating agent include carboxylic acid chelating agents such as gluconic acid, citric acid, tartaric acid, and EDTA, and salts thereof, as well as phosphonic acid chelating agents such as HEDP and PBTC. These may be used alone or in combination of two or more. The chelating agent preferably contains gluconic acid.

[0029] The content of the chelating agent in the surface conditioner is not particularly limited, but is preferably 0.05% by mass to 6.0% by mass, and more preferably 0.1% by mass to 5.0% by mass. If the content of the chelating agent is too low, the metal elements contained in the surface conditioner cannot be sufficiently stabilized, and the metal elements are likely to precipitate in excess, which may impair the adhesion improvement effect. Furthermore, if the content of the chelating agent is too high, the chelating agent is likely to be incorporated into the surface conditioning film, which reduces water resistance, and is particularly disadvantageous in terms of secondary adhesion after a boiling water test.

[0030] The pH of the surface conditioner is 10 or higher. This removes oxide films, such as zinc oxide films, and other metal elements, such as aluminum, from the surface of the metal substrate. Therefore, the anchor effect improves the physical bonding strength between the metal substrate surface and the film formed on the surface. In order to efficiently remove the other metal elements present on the surface of the metal substrate in a short period of time, the pH of the surface conditioner is preferably 13 or higher.

[0031] (Other Components) The surface conditioner according to this embodiment may contain components other than those described above. For example, it may contain a pH adjuster such as sodium hydroxide to adjust the pH of the surface conditioner to 10 or higher, or a solvent such as water or a solvent. Furthermore, other components, such as a leveling agent, an antifoaming agent, or an antibacterial agent, may be contained within a range that does not impair the effects of the present invention. On the other hand, it is preferable that the surface conditioner is substantially free of cobalt. This allows the surface conditioner to comply with environmental regulations. It is also preferable that the surface conditioner is substantially free of phosphorus, fluorine, and chromium. "Substantially free of cobalt, phosphorus, fluorine, and chromium" means that cobalt, phosphorus, fluorine, and chromium are not present in amounts sufficient to function as components in the surface conditioner. For example, in the case of cobalt, this means that the concentration of cobalt in the surface conditioner is less than 10 ppm. Since the surface conditioner used in this embodiment is substantially free of cobalt, phosphorus, fluorine, and chromium, compounds containing these elements that cause environmental impact are substantially not used, thereby reducing the environmental impact.

[0032] <Metal Substrate> The metal substrate to be surface-conditioned by the surface conditioner of this embodiment is not particularly limited, but examples thereof include iron-based materials such as cold-rolled steel, hot-rolled steel, stainless steel, electrogalvanized steel, hot-dip galvanized steel, zinc-aluminum alloy-plated steel, zinc-iron alloy-plated steel, zinc-magnesium alloy-plated steel, zinc-aluminum-magnesium alloy-plated steel, aluminum-plated steel, aluminum-silicon alloy-plated steel, tin-plated steel, lead-tin-plated steel, chromium-plated steel, and Ni-plated steel. Aluminum-based materials include metal materials such as pure aluminum and various aluminum alloys. Among these, zinc-containing metal substrates are preferred. The surface conditioner of this embodiment can effectively remove zinc oxide films, aluminum, and the like present on the metal substrate surface, thereby improving adhesion between the surface treatment film and the metal substrate surface. The shape of the metal substrate is not particularly limited, but examples thereof include plate-like shapes.

[0033] <Chromium-Free Surface Treatment Method> The chromium-free surface treatment method according to this embodiment includes a degreasing step, a first water-rinsing step, a surface conditioning step, and optionally a second water-rinsing step, and a surface treatment step. The chromium-free surface treatment method preferably includes the above steps in the order described above.

[0034] (Degreasing step) The degreasing step is a step of degreasing the surface of the metal substrate using a degreasing agent. The degreasing step can be performed using a degreasing agent. As the degreasing agent, for example, a known degreasing agent having alkaline or acidic liquid properties and containing a surfactant, an etching agent, etc. can be used.

[0035] (First Water-Rinsing Step) The first water-rinsing step is a step of rinsing the surface of the metal substrate that has been subjected to the degreasing step. The first water-rinsing step is not particularly limited, and can be performed by a known method such as spraying washing water.

[0036] (Surface Conditioning Step) The surface conditioning step is a step of applying the surface conditioner according to the above embodiment to the surface of the metal substrate after degreasing. The method of applying the surface conditioner is not particularly limited, and examples include roll coating, bar coating, spray treatment, and immersion treatment. The agent temperature in the surface conditioning step can be set appropriately depending on the surface reactivity of the metal substrate to be applied, and may be, for example, 30 to 60°C. The surface conditioning step may include a step of drying or baking the surface conditioner applied to the surface of the metal substrate. The drying or baking method is not particularly limited.

[0037] (Second Water-Rinsing Step) The second water-rinsing step is a step of rinsing the surface of the metal substrate that has been subjected to the surface conditioning step, and can be performed as needed. The second water-rinsing step is not particularly limited, and can be performed by a known method such as spraying washing water.

[0038] (Surface Treatment Step) The surface treatment step is a step of applying a surface treatment agent to the surface of the metal substrate that has undergone the surface conditioning step. The method of applying the surface treatment agent is not particularly limited, and examples include roll coating, bar coating, spraying, and immersion. The surface treatment step forms a surface treatment film on the surface of the metal substrate. Since the surface treatment step can be performed at the temperature of the working environment without requiring heating, the agent temperature is not particularly limited, and may be, for example, 5 to 50°C. However, if the chemical solution freezes during storage due to a drop in temperature in winter, it must be heated to return to a liquid state before use. The surface treatment step may also include a step of drying or baking the surface treatment agent applied to the surface of the metal substrate. The drying or baking method is not particularly limited. For example, after applying the surface treatment agent to the surface of the metal substrate, an upper layer may be painted while the surface treatment agent is still uncured, and then baking may be performed.

[0039] [Surface Treatment Agent] The surface treatment agent used in the surface treatment step preferably contains an organic phosphonic acid resin, a phosphoric acid compound, and a complex fluoride. It is more preferable that the surface treatment agent further contains a manganese compound and a vanadium compound. The surface treatment agent preferably does not contain trivalent or hexavalent chromium. The form of trivalent or hexavalent chromium is not particularly limited, and may include metallic chromium, chromium ions, chromium compounds, etc.

[0040] (Organic Phosphonic Acid Resin) The organic phosphonic acid resin is a copolymer containing a segment derived from a carboxy group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer. The segment derived from a carboxy group-containing acrylic acid monomer reacts with a coating film formed on a film formed by a surface treatment agent, improving adhesion. The segment derived from a phosphonic acid group-containing monomer reacts with the surface of a metal substrate to which the surface treatment agent is applied, improving adhesion. In addition, the crosslinking effect of other components improves chemical resistance. The segment derived from a carboxy group-containing acrylic acid monomer may be a monomer segment in which the functional group of an acrylic monomer having a functional group other than a carboxy group has been modified to form a carboxy group. The segment derived from a phosphonic acid group-containing monomer may be a monomer segment in which the functional group of a monomer having a functional group other than a phosphonic acid group has been modified to form a phosphonic acid group.

[0041] The carboxyl group-containing acrylic acid monomer is not particularly limited, but it is preferable to use, for example, a (meth)acrylic acid monomer.

[0042] The phosphonic acid group-containing monomer is vinylphosphonic acid, vinylidene-1,1-diphosphonic acid, or a phosphonic acid group-containing acrylic ester.

[0043] The content ratio of the segment derived from the phosphonic acid group-containing monomer in the organic phosphonic acid resin is preferably 20 mol% or more and 95 mol% or less with respect to the total of all segments constituting the organic phosphonic acid resin. When the content ratio of the segment derived from the phosphonic acid group-containing monomer is 20 mol% or more, the phosphonic acid group is sufficiently bonded to the metal substrate surface, improving adhesion and corrosion resistance. On the other hand, when it exceeds 95 mol%, bonding with the coating film is insufficient, resulting in reduced adhesion and corrosion resistance.

[0044] The content ratio of the segment derived from the carboxyl group-containing acrylic acid monomer in the organic phosphonic acid resin is preferably 5 mol% or more and 80 mol% or less relative to the total of all segments constituting the organic phosphonic acid resin. When the content ratio of the segment derived from the carboxyl group-containing acrylic acid monomer is 5 mol% or more, the acrylic acid group is sufficiently bonded to the coating film, improving adhesion and corrosion resistance. On the other hand, when it exceeds 80 mol%, bonding with the metal substrate surface is insufficient, resulting in reduced adhesion and corrosion resistance.

[0045] The organic phosphonic acid resin may contain other segments derived from monomers other than those mentioned above. The other monomers are not particularly limited, but examples thereof include hydroxyl group-containing acrylic monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, 1-methylethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate. Examples of suitable organic phosphonic acid resins include acrylic acid ester monomers such as acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, and dicyclopentadienyl (meth)acrylate; non-acrylic monomers such as styrene, α-methylstyrene, t-butylstyrene, vinylnaphthalene, acrylonitrile, methacrylonitrile, ethylene, propylene, vinyl acetate, vinyl propionate, butadiene, and isoprene; and (meth)acrylamides such as N-hydroxyethyl (meth)acrylamide, N-hydroxypropyl (meth)acrylamide, and N,N'-methylenebisacrylamide. The content of the other segments in the organic phosphonic acid resin is preferably 30 mol% or less, more preferably 10 mol% or less, and most preferably 0 mol%. The organic phosphonic acid resin is a two-component system of a carboxy group-containing acrylic acid monomer and a phosphonic acid group-containing monomer, and more preferably does not contain segments derived from other monomers. When the content of the other segments in the organic phosphonic acid resin is 30 mol % or less, the resin is sufficiently bonded to the surface of the metal substrate and the coating film, improving adhesion and corrosion resistance.

[0046] The organic phosphonic acid resin can be prepared by solution polymerization of a monomer mixture containing the above-mentioned monomers. The molecular weight of the organic phosphonic acid resin is preferably 10,000 to 100,000 in weight-average molecular weight. A weight-average molecular weight of 10,000 or more improves adhesion and corrosion resistance, while a weight-average molecular weight of 100,000 or less allows the resin to be blended without crosslinking with other metal components and increasing viscosity. The weight-average molecular weight can be measured by gel permeation chromatography. Commercially available organic phosphonic acid resins may also be used. Commercially available resins are not particularly limited, and examples include the ADDIBOND® series manufactured by Solvay.

[0047] By setting the content of the organic phosphonic acid resin to 2% by mass or more relative to the total solid content of the surface treatment agent, it is possible to improve the adhesion to metal and the edge corrosion resistance. By setting the content of the organic phosphonic acid resin to 30% by mass or less, it is possible to blend it in a well-balanced manner with other components, and it is possible to exhibit high corrosion resistance, adhesion, and chemical resistance.

[0048] (Phosphate Compound) Phosphate compounds include compounds having a phosphate group, such as orthophosphoric acid (phosphoric acid) and condensed phosphoric acid, as well as salts thereof. The inclusion of a phosphate compound in a surface treatment agent can improve the corrosion resistance of metals. The condensed phosphoric acid is a general term for linear polymeric phosphoric acids produced by dehydration condensation of orthophosphoric acid, and examples thereof include pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, and ultraphosphoric acid. Salts of the phosphate compounds include, but are not limited to, sodium salts, potassium salts, and ammonium salts.

[0049] The content of the phosphate compound is preferably 30 to 70% by mass relative to the total solid content of the surface treatment agent. When the content of the phosphate compound is 30% by mass or more, it becomes possible to improve the corrosion resistance of the metal. When the content of the phosphate compound is 70% by mass or less, it becomes possible to blend it in a balanced manner with other components, and it becomes possible to exhibit high corrosion resistance, adhesion, and chemical resistance.

[0050] (Complex Fluoride) When a complex fluoride is contained in a surface treatment agent, it improves the adhesion between a film formed by the surface treatment agent and a metal. Examples of complex fluorides include hydrosilicic acids such as hydrosilicic acid, zinc hydrosilicic acid, magnesium hydrosilicic acid, nickel hydrosilicic acid, iron hydrosilicic acid, and calcium hydrosilicic acid; ２ ZrF ６ ), ammonium hexafluorozirconate ((NH ４ ) ２ ZrF ６ fluoride of zirconium, such as titanium hydrofluoric acid (H ２ TiF ６ ), ammonium hexafluorotitanate ((NH ４ ) ２ TiF ６ The complex fluoride is preferably hydrosilicofluoric acid, as this further improves adhesion.

[0051] The content of the complex fluoride is preferably 5.0 to 20% by mass relative to the total solid content of the surface treatment agent. A complex fluoride content of 5.0% by mass or more improves adhesion between the coating and the metal. A complex fluoride content of 20% by mass or less allows for a well-balanced blend with other components, enabling high corrosion resistance, adhesion, and chemical resistance to be exhibited.

[0052] (Manganese Compound) When contained in a surface treatment agent, the manganese compound improves the chemical resistance (acid resistance and alkali resistance) of the metal. Examples of the manganese compound include organic acid salts such as manganese acetate, manganese benzoate, manganese lactate, manganese formate, and manganese tartrate; halides such as manganese chloride and manganese bromide; inorganic acid salts such as manganese nitrate, manganese carbonate, and manganese sulfate; alkoxides such as manganese methoxide; manganese acetylacetonate (II), manganese acetylacetonate (III), manganese dioxide, and manganese oxide.

[0053] When the content of elemental manganese derived from the manganese compound is 1% by mass or more relative to the total solid content of the surface treatment agent, it is possible to improve the chemical resistance of the metal. When the content of elemental manganese derived from the manganese compound is 15% by mass or less, it is possible to blend it in a well-balanced manner with other components, and it is possible to exhibit high corrosion resistance, adhesion, and chemical resistance.

[0054] The manganese element content mass ratio of the manganese compound to the organic phosphonic acid resin (manganese / organic phosphonic acid resin) is preferably 0.05 to 2.0. When the manganese / organic phosphonic acid resin ratio is 0.05 or more, a sufficient amount of manganese is ensured to exhibit chemical resistance, thereby favorably improving the chemical resistance of the metal. When the manganese / organic phosphonic acid resin ratio is 2.0 or less, the functional groups of the organic phosphonic acid resin are not consumed in bonding with manganese, and a sufficient amount of organic phosphonic acid resin is ensured, thereby favorably improving adhesion and corrosion resistance. From the above perspective, it is more preferable that the manganese / organic phosphonic acid resin ratio is 0.1 to 1.0.

[0055] (Vanadium Compound) When included in the surface treatment agent, the vanadium compound acts as a rust inhibitor and improves the corrosion resistance of the metal. The vanadium compound is not particularly limited, but examples thereof include vanadium pentoxide, metavanadic acid, ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride, vanadyl sulfate, vanadyl oxalate, magnesium vanadate, vanadium trioxide, vanadium trichloride, vanadium dioxide, vanadyl acetylacetonate, and vanadium acetylacetonate.

[0056] The content of the vanadium compound is preferably 5.0 to 20% by mass relative to the total solid content of the surface treatment agent. When the content of the vanadium compound is 5.0% by mass or more, the corrosion resistance of the metal is improved. When the content of the vanadium compound is 20% by mass or less, it can be blended in a well-balanced manner with other components, and high corrosion resistance, adhesion, and chemical resistance can be exhibited.

[0057] (Other Components) The surface treatment agent of the present embodiment may contain a chelating agent from the viewpoint of improving the stability of the treatment liquid. Examples of chelating agents that can be used in the surface treatment agent of the present embodiment include at least one selected from the group consisting of phosphonic acid chelating agents, aminocarboxylic acid chelating agents, and carboxyethyl group-based chelating agents.

[0058] Here, examples of phosphonic acid chelating agents include HEDP, NTMP, PBTC, EDTMP, etc. Examples of aminocarboxylic acid chelating agents include EDTA, NTA, DTPA, HEDTA, TTHA, PDTA, DPTA-OH, HIDA, DHEG, GEDTA, CMGA, EDDS, etc. Examples of carboxyethyl group-based chelating agents include citric acid, structural isomers of citric acid, adipic acid, aminohexanoic acid, etc.

[0059] The total content of the chelating agents contained in the surface treatment agent of this embodiment is preferably 1,000 to 15,000 ppm by mass, and more preferably 1,500 to 12,000 ppm by mass. If the total content of the chelating agents is less than 1,000 ppm by mass, the chelating stabilization effect of the metal components in the aqueous solution becomes insufficient. On the other hand, if the total content of the chelating agents exceeds 15,000 ppm by mass, the chelating stabilization effect saturates, making the surface treatment agent uneconomical.

[0060] The surface treatment agent of the present embodiment may further contain other components to the extent that the above-mentioned functions are not impaired. Examples of other components include known components contained in surface treatment agents, such as crosslinking agents, rust inhibitors, leveling agents, antifoaming agents, pH adjusters, and antibacterial agents.

[0061] (Other Steps) The chromium-free surface treatment method according to this embodiment may include other steps than those described above, provided that the effects of the present invention are not impaired. For example, the method may include a step of forming a coating film such as a primer layer or a top coat layer on top of the surface treatment film formed using the surface treatment agent.

[0062] The chromium-free surface treatment method according to this embodiment preferably involves first conditioning the surface with a surface conditioner containing an iron (III) compound, a molybdenum compound, and a chelating agent, and having a pH of 10 or higher, and then performing the surface treatment with a surface treatment agent containing an organic phosphonic acid resin, a phosphoric acid compound, a complex fluoride, and a manganese compound. Iron and molybdenum precipitated on the surface of the metal substrate by the surface conditioning serve as reaction sites, allowing a surface treatment film derived from the surface treatment agent to be efficiently formed, thereby forming a surface treatment film with excellent adhesion, corrosion resistance, and chemical resistance.

[0063] <Metal substrate containing a surface treatment film> The metal substrate containing a surface treatment film according to this embodiment is a metal substrate having a surface treatment film formed on its surface by the above-mentioned chromium-free surface treatment method. That is, the metal substrate containing a surface treatment film has a film formed by curing the above-mentioned surface conditioner and a film formed by curing the above-mentioned surface treatment agent. The film thickness is not particularly limited, but is preferably 0.01 to 1.0 μm. The weight of the film is not particularly limited, but is preferably 0.01 to 1.0 g / m ２ It is preferable that:

[0064] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0065] [Examples 1 to 42, Comparative Examples 1 to 9] <Preparation of Surface Conditioner> The components and water were blended and mixed and stirred to obtain the surface conditioners of the examples and comparative examples, so as to obtain the contents shown in Tables 1 to 4 below. In Comparative Example 1, no surface conditioner was used and no surface conditioning was performed. The content of each component in Tables 1 to 4 below indicates the content (mass %) in the surface conditioner. "Mo content (mass %)," "Fe content (mass %)," and "Co content (mass %)" refer to the content of each element in the surface conditioner.

[0066] The abbreviations used in Tables 1 to 4 are explained below.

[0067] (Metal substrate) GI: hot-dip galvanized steel sheet GL: hot-dip 55% aluminum-zinc alloy plated steel sheet

[0068] (Molybdenum compounds) A1: Sodium molybdate dihydrate A2: Ammonium molybdate (VI) tetrahydrate

[0069] (Iron (III) compounds) B1: Iron (III) nitrate B2: Iron (III) sulfate (Fe ２ (SO ４ ) ３ 70% (60-80%)

[0070] (Chelating agents) C1: Sodium gluconate C2: Trisodium citrate C3: Sodium tartrate C4: 1-hydroxyethane-1,1-diphosphonic acid (HEDP) C5: 3-carboxy-3-phosphonohexanedioic acid (PBTC) C6: Ethylenediaminetetraacetic acid tetrasodium salt dihydrate (EDTA-Na)

[0071] (Other ingredients) D: Sodium hydroxide A3: Cobalt nitrate hexahydrate B3: Iron (II) chloride tetrahydrate

[0072]

[0073]

[0074]

[0075]

[0076] <Preparation of Surface Treatment Agent> Each component was mixed and stirred with ion-exchanged water so that the solid content in the surface treatment agent was 2 mass% and the contents thereof were as shown in Tables 5 to 8 below, thereby obtaining surface treatment agents according to each Example and Comparative Example. The content of each component in Tables 5 to 8 below indicates the solid content (parts by mass). "Mn ratio" and "organic phosphonic acid resin ratio" refer to the content ratio of each component in the surface treatment agent (solid content mass ratio). "Mn / organic phosphonic acid resin" refers to the content ratio by mass of the manganese element of the manganese compound relative to the organic phosphonic acid resin (manganese / organic phosphonic acid resin).

[0077] The abbreviations used in Tables 5 to 8 are explained below.

[0078] (E1, E2: organic phosphonic acid resin, E3, E4: resin) E1: ADDIBOND (registered trademark) 021 (organic phosphonic acid resin (non-volatile content (NV): 20%), copolymer of vinylphosphonic acid and acrylic acid, molar ratio of vinylphosphonic acid: 30%, weight average molecular weight: 30,000 to 90,000, manufactured by Solvay) E2: ADDIBOND (registered trademark) 829 (organic phosphonic acid resin (non-volatile content (NV): 40%), manufactured by Solvay) E3: JURYMER AC-10L (polyacrylic acid (non-volatile content (NV): 40%), manufactured by Toagosei Co., Ltd.) E4: tannic acid

[0079] (Phosphate compound) F: Phosphate

[0080] (G1 to G4: Complex fluorides) G1: Hydrosilicic acid G2: Zirconic hydrofluoric acid (manufactured by Morita Chemical Industries Co., Ltd.) G3: Titanic hydrofluoric acid (manufactured by Morita Chemical Industries Co., Ltd.) G4: Aluminum fluoride

[0081] (H1 to H2: Manganese compounds) H1: Manganese nitrate H2: Manganese carbonate

[0082] (K1 to K4: Vanadium compounds) K1: Vanadyl sulfate K2: Ammonium metavanadate K3: Vanadyl oxalate K4: Vanadyl acetylacetonate (VO(C ５ H ７ O ２ ) ２ ) (Nasem Vanadyl, manufactured by Nippon Chemical Industry Co., Ltd.)

[0083] (Other ingredients) I: Zinc oxide J: Magnesium oxide L: 1-hydroxyethane-1,1-diphosphonic acid (chelating agent)

[0084]

[0085]

[0086]

[0087]

[0088] [Preparation of Test Plates] The metal substrates shown in Tables 1 to 4 above were spray-degreased using an alkaline degreasing agent (Nippon Paint Surf Chemicals, Surf Cleaner 155) at 60°C for 10 seconds and then rinsed with water. Thereafter, the surface conditioners according to the Examples and Comparative Examples shown in Tables 1 to 4 above were immersed or sprayed at 45°C for 6 seconds, rinsed with water, and then dried at 80°C. Subsequently, the surface treatment agents according to the Examples and Comparative Examples shown in Tables 5 to 8 above were applied with a bar coater (number: #3) after adjusting the solids concentration, and then dried using a hot air circulation oven so that the metal substrate reached a temperature of 80°C, thereby performing surface treatment. Next, a commercially available PCM primer paint (Flexicoat 600, manufactured by Nippon Paint Industrial Coatings Co., Ltd.) was applied to the test plate (dry film thickness: 5.0 μm) and baked at 200°C. Next, a PCM top coat paint (Flexicoat 5030, polyester paint, manufactured by Nippon Paint Industrial Coatings Co., Ltd.) was applied to the baked surface (dry film thickness: 15 μm) and baked at 225°C to produce a coated steel plate. Appropriate test specimens were cut from each of the coated steel plates produced in this manner to serve as test plates for each Example and Comparative Example. The test plates obtained as described above were subjected to the following evaluations. The evaluation results are shown in Tables 9 and 10.

[0089] <Evaluation> [Primary Bending Adhesion] In an environment of 20°C, the test plate was bent 180° without a spacer (0TT), or bent 180° with two 0.5 mm GI or GL plates sandwiched between them as spacers (2TT), and the bent portion was peeled off with tape, and the degree of peeling was observed with a 20x magnifying glass and evaluated according to the following criteria: A score of 3.5 or higher was considered a pass.

[0090] (Evaluation criteria) 5: No peeling 4.5: 1 to 10% peeling 4: 11 to 20% peeling 3.5: 21 to 30% peeling 3: 31 to 40% peeling 2.5: 41 to 50% peeling 2: 51 to 60% peeling 1.5: 61 to 70% peeling 1: 71 to 80% peeling 0.5: 81 to 90% peeling 0: 91 to 100% peeling

[0091] [Secondary Bending Adhesion] The test plate was immersed in boiling water for 2 hours and then left indoors for 24 hours. The test plate was evaluated under the same conditions as the primary bending adhesion, 0TT and 2TT, using the same criteria. A score of 3.5 or higher was considered to be acceptable.

[0092] [SST (Salt Spray Test)] A test plate with a cross cut was placed in a salt spray corrosion tester specified in JIS Z2317 for 1000 hours, and the maximum corrosion blister width on one side from the cut and the average corrosion blister width from the edge were measured and evaluated according to the following criteria: A maximum corrosion blister width of 3 or more points on one side from the cut and an average corrosion blister width of 3 or more points from the edge were considered to be acceptable.

[0093] (Evaluation criteria: width of coating blister from cut portion) 5: Less than 0.5 mm 4.5: 0.5 mm or more, less than 1 mm 4: 1 mm or more, less than 1.5 mm 3.5: 1.5 mm or more, less than 3 mm 3: 3 mm or more, less than 3.5 mm 2.5: 3.5 mm or more, less than 4 mm 2: 4 mm or more, less than 4.5 mm 1.5: 4.5 mm or more, less than 5 mm 1: 5 mm or more, less than 5.5 mm 0.5: 5.5 mm or more, less than 6 mm 0: 6 mm or more

[0094] (Evaluation criteria: width of coating blister from the end of the test piece) 5: Less than 2 mm 4.5: 2 mm or more, less than 4 mm 4: 4 mm or more, less than 6 mm 3.5: 6 mm or more, less than 8 mm 3: 8 mm or more, less than 10 mm 2.5: 10 mm or more, less than 12 mm 2: 12 mm or more, less than 14 mm 1.5: 14 mm or more, less than 16 mm 1: 16 mm or more, less than 18 mm 0.5: 18 mm or more, less than 20 mm 0: 20 mm or more

[0095] [Alkali Resistance] The alkali resistance was evaluated in accordance with ASTM D714-56 by the following method. Each test plate was immersed in a 5% by mass aqueous solution of sodium hydroxide at room temperature for 24 hours, and the size and density of blisters formed on the evaluation surface were visually evaluated. The evaluation was performed according to the following criteria, and a score of 3.5 or higher was considered to be pass.

[0096] (Evaluation criteria) 5: No blisters 4.5: The size of one blister is less than 0.3 mm and the density of occurrence is VF or F. 4: The size of one blister is 0.3 mm or more and less than 0.6 mm and the density of occurrence is VF or F. 3.5: The size of one blister is less than 0.6 mm and the density of occurrence is FM. 3: The size of one blister is less than 0.6 mm and the density of occurrence is M. Alternatively, the size of one blister is 0.6 mm or more and less than 1.2 mm and the density of occurrence is F or FM. 2.5: The size of one blister is less than 0.6 mm and the density of occurrence is MD. Alternatively, the size of one blister is 0.6 mm or more and less than 1.2 mm and the density of occurrence is FM or M. Alternatively, the size of one blister is 1.2 mm or more and less than 1.8 mm and the density of occurrence is VF or F. 2: The size of each blister is 0.6 mm or more and less than 1.2 mm, and the density of occurrence is M or MD. Alternatively, the size of each blister is 1.2 mm or more and less than 1.8 mm, and the density of occurrence is F or FM. 1.5: The size of each blister is 1.2 mm or more and less than 1.8 mm, and the density of occurrence is M or MD. 1: The size of each blister is 1.8 mm or more, or the density of occurrence is D regardless of blister size.

[0097] The symbols used for the density of blisters have the following meanings: VF: The number of blisters is extremely small. F: The number of blisters is small. FM: The number of blisters is somewhere between F and M. M: The number of blisters is large. MD: The number of blisters is somewhere between M and D. D: The number of blisters is extremely large.

[0098] [Acid Resistance] Each test plate was immersed in a 5% by mass aqueous solution of hydrochloric acid at room temperature for 24 hours, and the size and density of blisters formed on the test surface were visually evaluated. The evaluation was performed according to the same criteria as in the alkali resistance test, and a score of 3.5 or more after 24 hours was considered to be a pass.

[0099]

[0100]

[0101] The results in Tables 9 and 10 clearly show that the surface conditioners according to the examples are capable of realizing favorable adhesion of the surface treatment film to the metal substrate, and also have excellent corrosion resistance and chemical resistance.

Claims

1. A surface conditioner used in surface conditioning prior to surface treatment of a metal substrate, the surface conditioner comprising an iron (III) compound, a molybdenum compound, and a chelating agent, the iron element content in the surface conditioner being 0.02% by mass or more and 1.0% by mass or less, the molybdenum element content in the surface conditioner being 0.05% by mass or more and 2.5% by mass or less, and the pH of the surface conditioner being 10 or more.

2. The surface conditioner according to claim 1, comprising iron (III) nitrate as the iron (III) compound, a molybdenum salt as the molybdenum compound, and gluconic acid as the chelating agent.

3. A chromium-free surface treatment method for a metal substrate, comprising a degreasing step, a first water-rinsing step, a surface conditioning step, and optionally a second water-rinsing step and a surface treatment step, wherein the surface conditioning step is carried out using the surface conditioner according to claim 1 or 2.

4. The chrome-free surface treatment method according to claim 3, wherein the surface treatment agent used in the surface treatment step comprises an organic phosphonic acid resin, a phosphoric acid compound, and a complex fluoride, the organic phosphonic acid resin is a copolymer comprising a segment derived from a carboxyl group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, and the phosphonic acid group-containing monomer is vinyl phosphonic acid or a phosphonic acid group-containing acrylic ester.

5. The chromium-free surface treatment method according to claim 4, wherein the surface treatment agent further contains a manganese compound.

6. The chromium-free surface treatment method according to claim 4, wherein the surface treatment agent further contains a vanadium compound.

7. The chromium-free surface treatment method according to claim 4, wherein the complex fluoride is hydrosilicofluoric acid.

8. The chromium-free surface treatment method according to claim 5, wherein the manganese element content ratio of said manganese compound to said organic phosphonic acid resin (manganese / organic phosphonic acid resin) is 0.05 or more and 2.0 or less.

9. A metal substrate containing a surface treatment film, comprising a film of the surface conditioner according to claim 1 or 2, and a film of a surface treatment agent, wherein the surface treatment agent comprises an organic phosphonic acid resin, a phosphoric acid compound, and a complex fluoride, the organic phosphonic acid resin is a copolymer comprising a segment derived from a carboxyl group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, and the phosphonic acid group-containing monomer is vinyl phosphonic acid or a phosphonic acid group-containing acrylic ester.

10. The metal substrate with a surface treatment film according to claim 9, wherein the surface treatment agent further contains a manganese compound and a vanadium compound.

11. The metal substrate with a surface treatment film according to claim 9, which has a coating film on the film of the surface treatment agent.

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