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

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

[Technical Field]

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

[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 a metal, surface conditioning is performed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 43-012974 Summary of the Invention [Problem to be solved by the invention]

[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 demand 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. [Means for solving the problem]

[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 described in (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 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.

[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 element 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 provides a surface treatment film-containing 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, the surface treatment agent includes 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 carboxy group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, The present invention relates to a surface-treated film-containing metal substrate, wherein the phosphonic acid group-containing monomer is vinylphosphonic acid or a phosphonic acid group-containing acrylic 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. [Effects of the Invention]

[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. DETAILED DESCRIPTION OF THE INVENTION

[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 prior to 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) compounds) By incorporating an iron (III) compound into the surface conditioner, iron elements derived from the iron (III) compound are precipitated on the surface of the metal substrate prepared with the surface conditioner. The precipitated iron elements serve as reaction sites when a surface treatment film is formed by the surface treatment, allowing for the efficient formation of a composite metal salt film of 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 the 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 period of time.

[0022] The content of iron element in the surface conditioner is 0.02% by mass or more and 1.0% by mass or less. The content of iron element is preferably 0.03% by mass or more and 0.5% by mass or less. If the content of iron element is less than 0.03% by mass, a sufficient amount of iron element cannot be precipitated on the surface of the metal substrate, resulting in fewer reaction sites during surface treatment and insufficient improvement in adhesion. On the other hand, if the content of iron element exceeds 0.5% by mass, a large amount of iron element is precipitated on the surface of the metal substrate, resulting in the surface of the metal substrate being excessively coated with iron element, and fewer components derived from the metal substrate are eluted during surface treatment. This prevents the formation of a surface treatment film with an appropriate composition and insufficient improvement in adhesion.

[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 contains iron(III) nitrate. Iron(III) nitrate may be a hydrate, such as Fe(NO3)3·9H2O. The iron(III) compound may contain a compound other than iron(III) nitrate, such as iron(III) sulfate. The iron(III) compound preferably does not contain iron(III) chloride.

[0025] (Molybdenum compounds) When the molybdenum compound is contained in the surface conditioner, molybdenum elements derived from the molybdenum compound are precipitated on the surface of the metal substrate prepared with the surface conditioner, similar to the iron (III) compound. The precipitated molybdenum 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. 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 molybdenum content in the surface conditioner is 0.05% by mass or more and 2.5% by mass or less. The molybdenum content is preferably 0.06% by mass or more and 1.0% by mass or less. If the molybdenum content is less than 0.06% by mass, a sufficient amount of molybdenum cannot be precipitated on the surface of the metal substrate, resulting in fewer reaction sites during surface treatment, and thus insufficient improvement in adhesion. If the molybdenum content exceeds 1.0% by mass, a large amount of molybdenum precipitates on the surface of the metal substrate, resulting in excessive molybdenum coating on the surface of the metal substrate. This reduces the amount of components derived from the metal substrate that are eluted during surface treatment, making it impossible to obtain a surface treatment coating with an appropriate composition, and thus insufficient improvement in adhesion.

[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 compounds other than molybdate, such as molybdenum oxide, molybdenum fluoride, molybdenum alkoxide, and 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 excessive amounts of the metal elements may be precipitated, which may impair the adhesion-improving effect. Furthermore, if the content of the chelating agent is too high, the chelating agent may be easily incorporated into the surface conditioning film, resulting in a decrease in water resistance, particularly in 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 anchoring 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 ingredients) 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 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 base material> The metal substrate to be surface-treated with the surface conditioner of this embodiment is not particularly limited. Examples of iron-based materials include 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. Examples of aluminum-based materials include pure aluminum and various aluminum alloys. Of 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. Examples include a plate shape.

[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 process) 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] (1st water washing process) The first water-washing step is a step of rinsing the surface of the metal substrate that has been subjected to the degreasing step. The first water-washing step is not particularly limited, and can be carried out by a known method such as spraying with washing water.

[0036] (Surface conditioning process) 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 thereof include roll coating, bar coating, spraying, and immersion. 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] (2nd water washing process) The second water-washing step is a step of washing the surface of the metal substrate after the surface conditioning step with water, and can be performed as needed. The second water-washing step is not particularly limited and can be performed by a known method such as spraying washing water.

[0038] (Surface treatment process) The surface treatment process is a process of applying a surface treatment agent to the surface of the metal substrate that has undergone the surface conditioning process. The method for applying the surface treatment agent is not particularly limited, and examples include roll coating, bar coating, spraying, and immersion. The surface treatment process forms a surface treatment film on the surface of the metal substrate. Since the surface treatment process 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 process may also include a process 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 may be metallic chromium, chromium ions, chromium compounds, or the like, but is not particularly limited thereto.

[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 the 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 the 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 the 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 the 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 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, based on the total of all segments constituting the organic phosphonic acid resin. When the content of the segment derived from the phosphonic acid group-containing monomer is 20 mol% or more, the phosphonic acid group bonds sufficiently with the metal substrate surface, improving adhesion and corrosion resistance. On the other hand, when the content exceeds 95 mol%, bonding with the coating film becomes insufficient, resulting in reduced adhesion and corrosion resistance.

[0044] The content 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 of the segment derived from the carboxyl group-containing acrylic acid monomer is 5 mol% or more, the acrylic acid group bonds sufficiently with the coating film, improving adhesion and corrosion resistance. On the other hand, when the content 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 preferably a two-component system of a carboxyl 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 (registered trademark) series manufactured by Solvay.

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

[0048] (phosphate compounds) 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 mass% relative to the total solid content of the surface treatment agent. When the content of the phosphate compound is 30 mass% or more, it is possible to improve the corrosion resistance of metals. When the content of the phosphate compound is 70 mass% or less, it is possible to blend it in a balanced manner with other components, and it is possible to exhibit high corrosion resistance, adhesion, and chemical resistance.

[0050] (complex fluoride) The complex fluoride contained in the surface treatment agent improves the adhesion between the coating formed by the surface treatment agent and the 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; zirconium fluorides such as hydrosilicic acid (HZrF) and ammonium hexafluorozirconate ((NH)ZrF); and titanium fluorides such as hydrotitanic acid (HTiF) and ammonium hexafluorotitanate ((NH)TiF). The complex fluoride is preferably hydrosilicic 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 compounds) The manganese compound contained in the surface treatment agent 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] By ensuring that the manganese content 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. By ensuring that the manganese content derived from the manganese compound is 15% by mass or less, it is possible to blend it in a balanced manner with other components, enabling it to exhibit high corrosion resistance, adhesion, and chemical resistance.

[0054] The mass ratio of the manganese element 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 perspectives, the manganese / organic phosphonic acid resin ratio is more preferably 0.1 to 1.0.

[0055] (vanadium compounds) When contained in a surface treatment agent, the vanadium compound acts as a rust inhibitor and improves the corrosion resistance of metals. Examples of the vanadium compound include, but are not limited to, 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 ingredients) The surface treatment agent of this embodiment may contain a chelating agent from the viewpoint of improving the stability of the treatment liquid. Examples of the chelating agent that can be used in the surface treatment agent of this 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 1000 to 15000 ppm by mass, more preferably 1500 to 12000 ppm by mass. If the total content of the chelating agents is less than 1000 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 15000 ppm by mass, the chelating stabilization effect saturates, making the method 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 processes) 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 the surface treatment film formed by 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 treating the surface 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 substrates containing surface treatment films> The metal substrate having 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 having 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 thickness of the film 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: [Example]

[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 contents shown in Tables 1 to 4 below, thereby obtaining surface conditioners according to the examples and comparative examples. 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 base material) GI: Hot-dip galvanized steel sheet GL: Hot-dip 55% aluminum-zinc alloy coated 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 (70% (60-80%) as Fe2(SO4)3)

[0070] (chelating agent) 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] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] <Preparation of surface treatment agent> The surface treatment agents according to the examples and comparative examples were obtained by mixing and stirring the components and 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. 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 of the manganese element in the manganese compound 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® 829 (organic phosphonic acid resin (non-volatile content (NV): 40%), manufactured by Solvay) E3: Jurimer AC-10L (polyacrylic acid (non-volatile content (NV): 40%), manufactured by Toagosei Co., Ltd.) E4: Tannic acid

[0079] (phosphate compounds) F: Phosphate

[0080] (G1 to G4: complex fluorides) G1: Hydrofluorosilicic acid G2: Fluorozirconate (Morita Chemical Industry Co., Ltd.) G3: Titanium hydrofluoric acid (Morita Chemical Industry Co., Ltd.) G4: Aluminum fluoride

[0081] (H1-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(C5H7O2)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] [Table 5]

[0085] [Table 6]

[0086] [Table 7]

[0087] [Table 8]

[0088] [Preparation of test panels] The metal substrates shown in Tables 1 to 4 above were sprayed and degreased using an alkaline degreaser (Nippon Paint Surf Chemicals, Surf Cleaner 155) at 60°C for 10 seconds, followed by rinsing with water. The surface conditioners according to the examples and comparative examples shown in Tables 1 to 4 above were then immersed or sprayed at 45°C for 6 seconds, rinsed with water, and dried at 80°C. The surface treatment agents according to the examples and comparative examples shown in Tables 5 to 8 above were then applied with a bar coater (number: #3) after adjusting the solids concentration, and the metal substrates were dried in a hot air circulating oven until the temperature reached 80°C, thereby completing the 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. A PCM top coat paint (Flexicoat 5030, polyester paint, manufactured by Nippon Paint Industrial Coatings Co., Ltd.) was then 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 coated steel plate to form 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 adhesion after bending] In a 20°C environment, the test plate was bent 180° without a spacer (0TT), or bent 180° with two 0.5mm GI or GL plates sandwiched between them as spacers (2TT). The bent area 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: 1-10% peeling 4:11-20% peeling 3.5: 21-30% peeling 3:31-40% peeling 2.5:41-50% peeling 2: 51-60% peeling 1.5: 61-70% peeling 1:71-80% peeling 0.5: 81-90% peeling 0:91~100% peeling

[0091] [Secondary adhesion after bending] The test panels were immersed in boiling water for 2 hours, then left indoors for 24 hours. As with the primary bending adhesion, the test panels were evaluated under the same criteria for 0TT and 2TT conditions. A rating of 3.5 or higher was considered a pass.

[0092] [SST (Salt Spray Test)] Test plates with cross cuts were 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 pass.

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

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

[0095] [Alkali resistance] The alkali resistance was evaluated in accordance with ASTM D714-56 using the following method. Each test panel 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 acceptable.

[0096] (Evaluation criteria) 5: No blister 4.5: The size of a single 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 but 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 occurrence density is FM. 3: The size of each blister is less than 0.6 mm and the density of occurrence is M. Alternatively, the size of each 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 each blister is less than 0.6 mm and the density of occurrence is MD, or the size of each blister is 0.6 mm or more and less than 1.2 mm and the density of occurrence is FM or M, or the size of each 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, or 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 one 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 a single blister is 1.8 mm or more, or the density of occurrence is D regardless of the size of the blister.

[0097] The symbols used for the occurrence density have the following meanings: VF: The number of blisters is extremely small. F: Only a few blisters occurred. FM: The number of blisters is somewhere between F and M. M: A large number of blisters occurred. 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 higher after 24 hours was considered to be a pass.

[0099] [Table 9]

[0100] [Table 10]

[0101] The results in Tables 9 and 10 clearly show that the surface conditioners according to the examples are able to achieve 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 for surface conditioning of a metal substrate prior to surface treatment, the surface conditioner includes an iron (III) compound, a molybdenum compound, and a chelating agent; The content of iron element in the surface conditioner is 0.02% by mass or more and 1.0% by mass or less, The content of molybdenum element in the surface conditioner is 0.05% by mass or more and 2.5% by mass or less, The surface conditioner has a pH of 10 or more.

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

3. 1. A method for chromium-free surface treatment of a metal substrate, comprising: The chromium-free surface treatment method 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, 3. A chromium-free surface treatment method, wherein the surface conditioning step is carried out using the surface conditioner according to claim 1.

4. 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 carboxy group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, 4. The chromium-free surface treatment method according to claim 3, wherein the phosphonic acid group-containing monomer is vinylphosphonic 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. 5. The chromium-free surface treatment method according to claim 4, wherein the complex fluoride is hydrosilicofluoric acid.

8. 6. The chromium-free surface treatment method according to claim 5, wherein a 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.

9. A coating of the surface conditioner according to claim 1 or 2; A surface treatment film-containing metal substrate having a coating of a surface treatment agent, the surface treatment agent includes 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 carboxy group-containing acrylic acid monomer and a segment derived from a phosphonic acid group-containing monomer, The metal substrate having a surface treatment film, wherein the phosphonic acid group-containing monomer is vinylphosphonic 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 comprises 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 top of the film of the surface treatment agent.

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