Metal surface treatment agent

Abstract

Provided is a metal surface treatment agent that enables high-temperature sintering and imparts high corrosion resistance to a metal base material. A metal surface treatment agent contains a silicic acid compound (A), an alkali metal salt other than the silicic acid compound, a vanadium compound, and a zirconium compound, and the content of silicon is 10% by mass or more relative to the total solid content of the metal surface treatment agent. The silicic acid compound (A) is preferably an alkali metal silicate.

Description

Technical Field

[0001] This invention relates to metal surface treatment agents. Background Technology

[0002] Previously, zinc phosphate treatment and zirconium-based chemical treatment were known techniques for imparting corrosion resistance to metal substrates such as steel. Zinc phosphate treatment was used as a chemical treatment for coating substrates, but because it uses phosphorus, a nutrient-rich element, and nickel, which may be carcinogenic, as coating components, there has been a tendency to avoid its use in recent years from the perspectives of environmental protection and its impact on human health.

[0003] Zirconium-based chemical conversion treatment was previously used for aluminum-based materials. As for techniques to impart high corrosion resistance to steel materials, there is still room for improvement.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-186456 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The technology described in Patent Document 1 relates to the surface treatment of steel sheets, wherein the surface treatment film contains an acrylic resin emulsion. When the main components of the surface treatment film contain resin components such as acrylic resin emulsion, it is currently difficult to achieve a sintering temperature (PMT) exceeding, for example, 200°C. Consequently, sufficient heat resistance, durability, and corrosion resistance after coating are not obtained.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a metal surface treatment agent that can be sintered at high temperature and impart high corrosion resistance to metal substrates.

[0010] Methods for solving problems

[0011] (1) The present invention relates to a metal surface treatment agent containing a silica compound (A), an alkali metal salt (B) other than silica compound, vanadium compound and zirconium compound, a vanadium compound (C), a zirconium compound (D) and water, wherein the content of silicon element is 10% by mass or more relative to the total solid content of the metal surface treatment agent.

[0012] (2) The metal surface treatment agent according to (1), wherein the silica compound (A) is an alkali metal silicate.

[0013] (3) The metal surface treatment agent according to (1) or (2), wherein the molar ratio (M / Si) of the alkali metal element (M) contained in the solid component of the metal surface treatment agent to the silicon element (Si) is 0.5 to 1.2.

[0014] (4) The metal surface treatment agent according to any one of (1) to (3), wherein, relative to the total solid content of the metal surface treatment agent, the content of vanadium is 0.1 to 10% by mass and the content of zirconium is 0.1 to 10% by mass.

[0015] (5) The metal surface treatment agent according to any one of (1) to (4) further comprises a chelating agent (E).

[0016] (6) A metal surface treatment film, which is formed by curing any one of (1) to (5) metal surface treatment agents.

[0017] (7) A surface-treated metal having the metal surface-treated film described in (6).

[0018] Invention Effects

[0019] According to the present invention, a metal surface treatment agent capable of high-temperature sintering and imparting high corrosion resistance to metal substrates can be provided. Detailed Implementation

[0020] Hereinafter, a metal surface treatment agent according to an embodiment of the present invention will be described. The present invention is not limited to the embodiments described below.

[0021] Metal Surface Treatment Agents

[0022] The metal surface treatment agent of this embodiment contains a silicate compound (A), an alkali metal salt (B) excluding the silicate compound, vanadium compound, and zirconium compound, a vanadium compound (C), a zirconium compound (D), and water. Additionally, a chelating agent (E) is preferably included.

[0023] (Silicic acid compound (A))

[0024] The silica compound (A) is the main component of the film formed by the metal surface treatment agent. By making the silica compound (A), an inorganic compound, the main component of the film, high-temperature sintering of the film is possible. Specific examples of silica compound (A) include alkali metal silicates, colloidal silica, alkyl silicate compounds, hydrolysis products of alkyl silicate compounds, and condensation products of alkyl silicate compounds. From the viewpoint of corrosion resistance, the silica compound (A) is preferably an alkali metal silicate. Examples of alkali metal silicates include alkali metal salts of orthosilicic acid such as lithium orthosilicate, sodium orthosilicate, and potassium orthosilicate, as well as alkali metal salts of metasilicic acid such as lithium metasilicate, sodium metasilicate, and potassium metasilicate. Examples of alkyl silicate compounds include methyl silicate and ethyl silicate.

[0025] The silicon content is 10% by mass or more relative to the total solids content of the metal surface treatment agent in this embodiment. Preferably, the silicon content is 20% by mass or more and 40% by mass or less. By setting the silicon content to 10% by mass or more, for example, it is possible to set the raw material arrival temperature (PMT) to 200°C or higher, thereby enabling high-temperature sintering of the film formed by the metal surface treatment agent. If the silicon content exceeds 40% by mass, the amount of other necessary components decreases, making it difficult to achieve the stability and corrosion resistance of the metal surface treatment agent.

[0026] (Alkali metal salt (B))

[0027] Alkali metal salts (B) are alkali metal salts other than silicate compounds, vanadium compounds, and zirconium compounds, and they function as crosslinking agents. By including alkali metal salts (B) in metal surface treatment agents, the barrier properties of the formed film against water and corrosive agents (such as chloride ions) are improved, resulting in enhanced corrosion resistance to the metal substrate. Specific examples of alkali metal salts (B) are not particularly limited, but examples include carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate; bicarbonates such as lithium bicarbonate, sodium bicarbonate, and potassium bicarbonate; hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and nitrites such as lithium nitrite, sodium nitrite, and potassium nitrite.

[0028] (vanadium compound (C))

[0029] Vanadium compounds (C) function as rust inhibitors by being added to metal surface treatment agents. Vanadium compounds (C) are not particularly limited, and examples include vanadium pentoxide, metavanadate, ammonium metavanadate, sodium metavanadate, vanadium oxychloride, vanadium oxysulfate, magnesium vanadate, vanadium trioxide, vanadium trichloride, vanadium dioxide, vanadium oxyacetylacetonate, and vanadium acetylacetonate.

[0030] The vanadium content is preferably 0.1 to 10% by mass relative to the total solids content of the metal surface treatment agent of this embodiment. More preferably, the vanadium content is 0.5 to 5% by mass. When the vanadium content is less than 0.1% by mass, sufficient rust prevention is not achieved. When the vanadium content exceeds 10% by mass, the stability and corrosion resistance of the metal surface treatment agent decrease.

[0031] (Zirconium compound (D))

[0032] Zirconium compounds (D) act as crosslinking agents, thereby improving the barrier properties of the formed film against water and corrosive agents (such as chloride ions), resulting in enhanced corrosion resistance. There are no particular limitations on zirconium compounds (D), but examples include zirconium carbonate salts such as ammonium zirconium carbonate and potassium zirconium carbonate, alkali metal fluorozirconates such as K₂ZrF₆, hexafluorozirconic acid (H₂ZrF₆), ammonium zirconium fluoride ((NH₄)₂ZrF₆), zirconium fluoride, zirconium nitrate, and zirconium oxide.

[0033] The zirconium content is preferably 0.1 to 10% by mass relative to the total solids content of the metal surface treatment agent of this embodiment. Within this range, the stability and corrosion resistance of the metal surface treatment agent are improved. More preferably, the zirconium content is 0.5 to 5% by mass. When the zirconium content is less than 0.1% by mass, its effect as a crosslinking agent is insufficient. When the zirconium content exceeds 10% by mass, the stability and corrosion resistance of the treatment agent decrease.

[0034] The molar ratio (M / Si) of the alkali metal element (M) to silicon element (Si) in the solid component of the metal surface treatment agent of this embodiment is preferably 0.5 to 1.2. More preferably, the molar ratio (M / Si) is 0.6 to 1.1. When the molar ratio (M / Si) is below 0.5, the corrosion resistance decreases. When the molar ratio (M / Si) exceeds 1.2, the stability of the metal surface treatment agent decreases. It should be noted that the alkali metal element (M) includes alkali metal elements derived from silicate compounds (A), vanadium compounds (C), zirconium compounds (D), or other compounds other than alkali metal salts (B).

[0035] (chelating agent (E))

[0036] Chelating agents (E) are added to metal surface treatment agents to stabilize zirconium in the agents. There are no particular limitations on chelating agents (E), and examples include hydroxycarboxylic acids such as lactic acid, malic acid, tartaric acid, citric acid, and gluconic acid; organophosphorus compounds such as ethylenediaminetetraacetic acid (EDTA) and 1-hydroxyethane-1,1-diphosphonic acid (HEDP); hydroxyamines such as triethanolamine (TEA); and salts of the above compounds.

[0037] As a chelating agent (E), it may contain organophosphorus compounds such as HEDP, but from the viewpoint of reducing the environmental impact caused by eutrophication, the metal surface treatment agent of this embodiment preferably does not contain phosphoric acid such as orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), metaphosphoric acid (HPO3) and inorganic phosphoric acid such as ammonium phosphate and sodium phosphate.

[0038] (Other ingredients)

[0039] The metal surface treatment agent of this embodiment includes water as a component other than those described above. Furthermore, other components may be further included in the metal surface treatment agent without impairing its functions. Examples of these other components include olefin resins such as acrylic resins, polyurethane resins, epoxy resins, and ethylene-acrylic acid copolymers, as well as polyester resins, polyolefin resins, alkyd resins, and polycarbonate resins. When the metal surface treatment agent includes the above-mentioned resin components, the solid content of the resin component relative to the total solid content of the metal surface treatment agent is preferably 10% by mass or less, more preferably 5% by mass or less. This allows for optimal high-temperature sintering of the metal surface treatment agent. Other components besides those described above include known components found in surface treatment agents such as crosslinking agents, rust inhibitors, leveling agents, defoamers, and pH adjusters.

[0040] (Solid content)

[0041] The solid content of the metal surface treatment agent in this embodiment is preferably 0.1 to 30% by mass, more preferably 1.0 to 25% by mass.

[0042] <Metal substrate>

[0043] The metal substrate, which is the object to be surface treated using the metal surface treatment agent of this embodiment, is not particularly limited. Examples include cold-rolled steel, hot-rolled steel, stainless steel, electro-galvanized steel, molten galvanized steel, zinc-aluminum alloy coated steel, zinc-iron alloy coated steel, zinc-magnesium alloy coated steel, zinc-aluminum-magnesium alloy coated steel, aluminum-based coated steel, aluminum-silicon alloy coated steel, tin-based coated steel, lead-tin-based coated steel, chromium-based coated steel, and Ni-based coated steel. The shape of the metal substrate is not particularly limited; for example, a plate shape may be used.

[0044] <Metal Surface Treatment Methods>

[0045] The metal surface treatment agent in this embodiment is a so-called coating-type metal surface treatment agent. The coating-type metal surface treatment agent can be used in a method where, after coating the surface treatment agent onto the surface of a metal substrate, the surface of the metal substrate is not washed with water before sintering (drying). That is, the metal surface treatment method in this embodiment includes a coating step of applying a metal surface treatment agent to the surface of a metal substrate and a sintering step of sintering the metal substrate coated with the metal surface treatment agent. The coating-type metal surface treatment agent of this embodiment has the advantage of being able to easily form a metal surface treatment film and not generating waste liquid.

[0046] In the coating process, there are no particular limitations on the method of applying a metal surface treatment agent to the surface of the metal substrate. For example, methods such as roller coating, bar coating, spraying, and dipping can be used. It should be noted that before the coating process, the surface of the metal substrate can be degreased, pickled, or etched as needed.

[0047] In the sintering process, after the coating process, the metal surface treatment agent coated on the metal substrate is sintered. There are no particular limitations on the sintering method described above. The sintering temperature is not particularly limited; for example, it is preferably set to 200°C to 400°C based on the raw material arrival temperature (PMT). The sintering time is not particularly limited; for example, it can be set to 3 to 180 seconds.

[0048] <Metal Surface Treatment Coating>

[0049] The film formed by the above-described metal surface treatment method (hereinafter, sometimes simply referred to as "film") contains all components of the metal surface treatment agent except for volatile components such as water. Specifically, the silicon content in the metal surface treatment film is 10% by mass or more. Preferably, the molar ratio (M / Si) of the alkali metal element (M) to the silicon element (Si) in the metal surface treatment film is 0.5 to 1.2. The vanadium content in the metal surface treatment film is preferably 0.1% to 10% by mass. The zirconium content in the metal surface treatment film is preferably 0.1% to 10% by mass. The film weight is not particularly limited, but is preferably 0.3 to 2.0 g / m³. 2 More preferably, it is 0.5–1.5 g / m 2 .

[0050] <Surface-treated Metals>

[0051] The surface-treated metal of this embodiment is formed by forming the aforementioned metal surface-treated film on the surface of the aforementioned metal substrate. The surface-treated metal may be a metal on which a coating is formed. As the coating material for forming the coating, there are no particular limitations; a single-coat coating material may be used, or a primer and a topcoat may be used.

[0052] Example

[0053] The present invention will now be described in more detail based on embodiments, but the present invention is not limited to the embodiments.

[0054] <Preparation of Metal Surface Treatment Agents>

[0055] [Examples 1 to 36, Comparative Examples 1 to 4]

[0056] The following metal surface treatment agent was prepared by measuring silicate compound (A), alkali metal salt (B), vanadium compound (C), zirconium compound (D), and chelating agent (E) in the manner described in Tables 1 to 4 below, adding ion-exchanged water such that the total solid content concentration of these compositions in the metal surface treatment agent was 18% by mass, and mixing and stirring. The amounts of each component listed in Tables 1 to 4 are expressed in parts by mass. The "Si content," "V content," and "Zr content" listed in Tables 1 to 4 represent the content (in mass%) of silicon, vanadium, and zirconium elements relative to the total solid content of the metal surface treatment agent, respectively.

[0057] The details of the types of raw materials recorded in Tables 1 to 4 are as follows.

[0058] (Silicic acid compound (A))

[0059] A1: Sodium Silicate No. 3 (Sodium silicate, manufactured by Nippon Chemical Industries, Ltd.)

[0060] A2: Lithium silicate 35 (Lithium silicate, SiO2 / Li2O (molar ratio) = 3.5, manufactured by Nippon Chemical Industries, Ltd.)

[0061] A3: Lithium silicate 75 (Lithium silicate, SiO2 / Li2O (molar ratio) = 7.5, manufactured by Nippon Chemical Industries, Ltd.)

[0062] A4: 2K Potassium Silicate (Potassium silicate, manufactured by Nippon Chemical Industries, Ltd.)

[0063] A5: Hydrolysis product of ethyl silicate 28 (ethyl silicate, manufactured by COLCOAT Co., Ltd.)

[0064] (Alkali metal salt (B))

[0065] B1: Sodium hydroxide

[0066] B2: Sodium bicarbonate

[0067] B3: Sodium carbonate

[0068] B4: Lithium hydroxide monohydrate

[0069] B5: Potassium hydroxide

[0070] B6: Sodium nitrite

[0071] B7: Lithium nitrite

[0072] (vanadium compound (C))

[0073] C1: Vanadium oxysulfate

[0074] C2: Ammonium metavanadate

[0075] C3: Sodium metavanadate

[0076] (Zirconium compound (D))

[0077] D1: Ammonium zirconate carbonate

[0078] D2: Potassium zirconium carbonate

[0079] D3: AZ Coat 5800MT (45% ammonium zirconium carbonate solution, manufactured by Sannopco Co., Ltd.)

[0080] D4: ZSL-10A (Zirconium oxide sol, pH 7.7, manufactured by Daiichi Rare Element Chemical Industry Co., Ltd.)

[0081] D5: Zirconium fluoride ammonium fluoride

[0082] D6: Zirconium nitrate

[0083] (chelating agent (E))

[0084] E1: Citric acid

[0085] E2: Gluconic acid

[0086] E3: 1-Hydroxyethylidene-1,1-Diphosphonic acid

[0087] E4: Triethanolamine

[0088] E5: Ethylenediaminetetraacetic acid

[0089] [Table 1]

[0090]

[0091] [Table 2]

[0092]

[0093] [Table 3]

[0094]

[0095] [Table 4]

[0096]

[0097] [Storage Stability Test]

[0098] In an incubator at 40°C, after allowing the metal surface treatment agents shown in Tables 1 to 4 to stand for 7 days, visually evaluate the storage stability according to the following criteria, with 2 being qualified. The results are shown in Tables 5 and 6.

[0099] 2: The content of the metal surface treatment agent has not settled

[0100] 1: The content of the metal surface treatment agent has settled

[0101] <Fabrication of Test Panels>[[]]

[0102] Using the metal surface treatment agents shown in Tables 1 to 4, perform surface treatment on cold-rolled steel sheets (SPCC270SD, manufactured by PALTEK Co., Ltd.) specified in JIS G3135 as metal substrates. The surface treatment is carried out according to the following steps. First, immerse the above-mentioned metal substrate in a solution obtained by adjusting Surf cleaner 53NF manufactured by Nippon Paint Surf Chemicals Co., Ltd. to a concentration of 2% at 45°C for 2 minutes for degreasing treatment. After washing the degreased metal substrate with water, dry it. Then, use a bar coater to coat the surface of the above-mentioned metal substrate with the metal surface treatment agents shown in Tables 1 to 4 so that the film thickness becomes 0.7 g / m 2 . Then, heat the above-coated metal substrate in an oven at a temperature of 550°C for 15 seconds for sintering. The raw material arrival temperature (PMT) during sintering is 300°C. Use the test panels obtained from the above-mentioned respective examples and comparative examples for the following evaluations. <00XX216><Evaluation>[[]]

[0104] [Corrosion Resistance (Salt Spray Test (SST))]

[0105] Place each test panel in a salt spray corrosion test machine as specified in JIS Z2317 for 4 hours, 8 hours, and 16 hours, and visually evaluate the area of red rust generation according to the following criteria, with a value of 2 or above being qualified. The results are shown in Tables 5 and 6.

[0106] 4: The area of red rust generation after 16 hours of SST is 5% or less of the area of the test panel

[0107] 3: The area of red rust generation after​​​​​​

[0110] [Table 5]

[0111]

[0112] [Table 6]

[0113]

[0114] The results in Tables 5 and 6 show the following: The test panels of the Examples exhibit superior corrosion resistance compared to the test panels of Comparative Examples 1, 3, and 4 (which do not contain specific components) and the test panel of Comparative Example 2 (which has a silicon content of less than 10% by mass). Furthermore, the metal surface treatment agents of the Examples demonstrate superior storage stability compared to the surface treatment agents of Comparative Examples 2 and 4.

Claims

1. A metal surface treatment agent comprising a silicate compound (A), an alkali metal salt (B) excluding the silicate compound, vanadium compound, and zirconium compound, a vanadium compound (C), a zirconium compound (D), and water, wherein the silicate compound (A) is an alkali metal silicate. The silicon content is between 10% and 40% by mass relative to the total solids content of the metal surface treatment agent.

2. A metal surface treatment agent comprising a silicate compound (A), an alkali metal salt (B) excluding the silicate compound, vanadium compound, and zirconium compound, a vanadium compound (C), a zirconium compound (D), and water. The silicon content, relative to the total solids content of the metal surface treatment agent, is between 10% and 40% by mass. The molar ratio of alkali metal element M to silicon element Si in the solid component of the metal surface treatment agent, i.e., M / Si, is 0.5~1.

2.

3. The metal surface treatment agent according to claim 2, wherein, The silica compound (A) is an alkali metal silicate.

4. The metal surface treatment agent according to claim 1 or 2, wherein, The content of vanadium is 0.1 to 10% by mass and the content of zirconium is 0.1 to 10% by mass relative to the total solid content of the metal surface treatment agent.

5. The metal surface treatment agent according to claim 1 or 2, further comprising a chelating agent (E).

6. A metal surface treatment film, which is formed by curing the metal surface treatment agent according to claim 1 or 2.

7. A surface-treated metal having the metal surface-treated film of claim 6.

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