Metal surface treatment agents

Abstract

The purpose of the present invention is to provide a metal surface treatment agent that can be baked at high temperatures and can impart high corrosion resistance to metal base materials.　Provided is a metal surface treatment agent comprising a silicic acid compound (A), an alkali metal salt (B) that is different from a silicic acid compound, a vanadium compound and a zirconium compound, a vanadium compound (C), a zirconium compound (D), and water, in which the content of a silicon element is 10% by mass or more relative to the whole solid content in the metal surface treatment agent. The silicic acid compound (A) is preferably a silicic acid salt of an alkali metal.

Description

[Technical Field]

[0001] The present invention relates to a metal surface treatment agent. [Background technology]

[0002] Zinc phosphate treatment and zirconium-based conversion coatings have been known as techniques for imparting corrosion resistance to metal substrates such as steel. Zinc phosphate treatment is used as a conversion coating for paint primers, but because it contains phosphorus, a eutrophic element, and nickel, which may be carcinogenic, as coating components, its use has tended to be avoided in recent years due to concerns about environmental protection and its impact on the human body.

[0003] Zirconium-based chemical conversion coating is a technology that has conventionally been applied to aluminum-based materials, and currently there is still room for improvement in the technology for imparting high corrosion resistance to steel materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-186456 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology described in Patent Document 1 relates to surface-treated steel sheets, and the surface treatment film contains an acrylic resin emulsion. When the main component of the surface treatment film contains a resin component such as an acrylic resin emulsion, it is difficult to raise the material temperature (PMT) during baking to a high temperature exceeding 200°C, for example, and the current situation is that the coating film does not have sufficient heat resistance and durability, and sufficient corrosion resistance after painting is also not achieved.

[0006] The present invention has been made in view of the above, and an object of the present invention is to provide a metal surface treatment agent that can be baked at high temperatures and can impart high corrosion resistance to metal substrates. [Means for solving the problem]

[0007] (1) The present invention relates to a metal surface treatment agent comprising a silicate compound (A), an alkali metal salt (B) other than a silicate compound, a vanadium compound, and a zirconium compound, a vanadium compound (C), a zirconium compound (D), and water, wherein the silicon content is 10 mass% or more based on the total solid content of the metal surface treatment agent.

[0008] (2) The metal surface treatment agent according to (1), wherein the silicate compound (A) is an alkali metal silicate.

[0009] (3) The metal surface treatment agent according to (1) or (2), wherein the molar ratio (M / Si) of the alkali metal element (M) to the silicon element (Si) contained in the solid content of the metal surface treatment agent is 0.5 to 1.2.

[0010] (4) The metal surface treatment agent according to any one of (1) to (3), wherein the vanadium element content is 0.1 to 10 mass % and the zirconium element content is 0.1 to 10 mass % relative to the total solid content of the metal surface treatment agent.

[0011] (5) The metal surface treatment agent according to any one of (1) to (4), further comprising a chelating agent (E).

[0012] (6) A metal surface treatment film obtained by curing the metal surface treatment agent according to any one of (1) to (5).

[0013] (7) A surface-treated metal having the metal surface treatment film according to (6). [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a metal surface treatment agent that can be baked at high temperatures and can impart high corrosion resistance to metal substrates. DETAILED DESCRIPTION OF THE INVENTION

[0015] The metal surface treatment agent according to the embodiment of the present invention will be described below, but the present invention is not limited to the description of the following embodiment.

[0016] <Metal surface treatment agent> The metal surface treatment agent according to this embodiment contains a silicate compound (A), an alkali metal salt (B) other than a silicate compound, a vanadium compound, and a zirconium compound, a vanadium compound (C), a zirconium compound (D), and water. It also preferably contains a chelating agent (E).

[0017] (Silicate compound (A)) The silicate compound (A) is the main component of the coating formed by the metal surface treatment agent. By using the inorganic silicate compound (A) as the main component of the coating, the coating can be baked at high temperatures. Specific examples of the silicate compound (A) include alkali metal silicates, colloidal silica, alkyl silicate compounds, hydrolysis products of alkyl silicate compounds, and condensation polymerization products of alkyl silicate compounds. However, from the viewpoint of corrosion resistance, the silicate 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; alkali metal salts of metasilicic acid such as lithium metasilicate, sodium metasilicate, and potassium metasilicate; and the like. Examples of alkyl silicate compounds include methyl silicate, ethyl silicate, and the like.

[0018] The silicon element content of the metal surface treatment agent of this embodiment is 10% by mass or more relative to the total solid content. The silicon element content is preferably 20% by mass or more and 40% by mass or less. When the silicon element content is 10% by mass or more, the coating formed by the metal surface treatment agent can be baked at a high temperature, for example, with a material temperature (PMT) of 200°C or higher. If the silicon element content is more than 40% by mass, the blending amounts of other essential components will be reduced, making it difficult for the metal surface treatment agent to exhibit stability and corrosion resistance.

[0019] (Alkali metal salt (B)) The alkali metal salt (B) is an alkali metal salt other than silicate compounds, vanadium compounds, and zirconium compounds, and acts as a crosslinking agent. The inclusion of the alkali metal salt (B) in the metal surface treatment agent improves the barrier properties of the formed coating against water and corrosion factors (chloride ions, etc.), thereby improving the corrosion resistance of the metal substrate. Specific examples of the alkali metal salt (B) include, but are not limited to, 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.

[0020] (Vanadium Compounds (C)) The vanadium compound (C) acts as a rust inhibitor when added to a metal surface treatment agent. The vanadium compound (C) is not particularly limited, but examples thereof include vanadium pentoxide, metavanadic acid, ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride, vanadyl sulfate, magnesium vanadate, vanadium trioxide, vanadium trichloride, vanadium dioxide, vanadyl acetylacetonate, and vanadium acetylacetonate.

[0021] The vanadium content of the metal surface treatment agent of this embodiment is preferably 0.1 to 10 mass% relative to the total solid content. The vanadium content is more preferably 0.5 to 5 mass%. If the vanadium content is less than 0.1 mass%, sufficient rust prevention properties cannot be obtained. If the vanadium content exceeds 10 mass%, the stability and corrosion resistance of the metal surface treatment agent are reduced.

[0022] (Zirconium Compounds (D)) The zirconium compound (D) acts as a crosslinking agent, improving the barrier properties of the formed coating against water and corrosive factors (chloride ions, etc.), resulting in improved corrosion resistance. The zirconium compound (D) is not particularly limited, but examples thereof include zirconium carbonate salts such as ammonium zirconium carbonate and potassium zirconium carbonate; alkali metal fluorozirconates such as KZrF; hydrofluoric zirconate (HZrF); ammonium zirconate fluoride ((NH)ZrF); zirconium fluoride; zirconium nitrate; and zirconium oxide.

[0023] The content of zirconium element relative to the total solid content of the metal surface treatment agent of this embodiment is preferably 0.1 to 10 mass%. With the zirconium element content in this range, the stability and corrosion resistance of the metal surface treatment agent are improved. The content of the zirconium element is more preferably 0.5 to 5 mass%. If the content of the zirconium element is less than 0.1 mass%, the effect as a sufficient crosslinking agent cannot be obtained. If the content of the zirconium element exceeds 10 mass%, the stability and corrosion resistance of the treatment agent are reduced.

[0024] The molar ratio (M / Si) of alkali metal element (M) to silicon element (Si) contained in the solid content of the metal surface treatment agent of this embodiment is preferably 0.5 to 1.2. The molar ratio (M / Si) is more preferably 0.6 to 1.1. If the molar ratio (M / Si) is less than 0.5, corrosion resistance decreases. If the molar ratio (M / Si) exceeds 1.2, the stability of the metal surface treatment agent decreases. The alkali metal element (M) includes alkali metal elements derived from the silicate compound (A), vanadium compound (C), zirconium compound (D), or other compounds other than the alkali metal salt (B).

[0025] (Chelating agent (E)) The chelating agent (E) is added to the metal surface treatment agent to stabilize zirconium in the metal surface treatment agent. Examples of the chelating agent (E) include, but are not limited to, hydroxycarboxylic acids such as lactic acid, malic acid, tartaric acid, citric acid, and gluconic acid; ethylenediaminetetraacetic acid (EDTA); organophosphorus compounds such as 1-hydroxyethane-1,1-diphosphonic acid (HEDP); hydroxyamines such as triethanolamine (TEA); and salts of the above compounds.

[0026] The chelating agent (E) may contain an organic phosphorus compound such as HEDP. However, from the viewpoint of reducing the environmental impact of eutrophication, it is preferable that the metal surface treatment agent according to this embodiment does not contain inorganic phosphorus compounds such as phosphoric acids, such as orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), and metaphosphoric acid (HPO3), and phosphates, such as ammonium phosphate and sodium phosphate.

[0027] (Other ingredients) The metal surface treatment agent of this embodiment contains water as a component other than those described above. The metal surface treatment agent may also contain other components to the extent that the above functions are not impaired. Examples of other components include resin components such as acrylic resins, urethane resins, epoxy resins, olefin resins such as ethylene-acrylic copolymers, polyester resins, polyolefin resins, alkyd resins, and polycarbonate resins. When the resin components are contained in the metal surface treatment agent, the solid content of the resin components 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 the metal surface treatment agent to be favorably baked at high temperatures. Examples of other components besides those described above include known components contained in surface treatment agents, such as crosslinkers, rust inhibitors, leveling agents, antifoaming agents, and pH adjusters.

[0028] (Solid content) The solid content of the metal surface treatment agent of this embodiment is preferably 0.1 to 30 mass %, more preferably 1.0 to 25 mass %.

[0029] <Metal base material> The metal substrate to be surface-treated with the metal surface treatment agent of this embodiment is not particularly limited, and examples thereof 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. The shape of the metal substrate is not particularly limited, and examples thereof include a plate shape.

[0030] <Metal surface treatment method> The metal surface treatment agent of this embodiment is a so-called application-type metal surface treatment agent. Application-type metal surface treatment agents are used in a method in which the surface treatment agent is applied to the surface of a metal substrate, and then the surface of the metal substrate is baked (dried) without rinsing with water. That is, the metal surface treatment method of this embodiment comprises an application step of applying the metal surface treatment agent to the surface of the metal substrate, and a baking step of baking the applied metal surface treatment agent on the metal substrate. The application-type metal surface treatment agent of this embodiment has the advantage that it allows for relatively easy formation of a metal surface treatment film and does not produce waste liquid.

[0031] In the coating step, the method for coating the surface of the metal substrate with the metal surface treatment agent is not particularly limited, and examples thereof include roll coating, bar coating, spraying, immersion, etc. Prior to the coating step, the surface of the metal substrate may be subjected to a degreasing treatment, pickling, or etching treatment, if necessary.

[0032] In the baking step, after the application step, the metal surface treatment agent applied to the metal substrate is baked. The baking method is not particularly limited. The baking temperature is not particularly limited, but it is preferable that the material reach temperature (PMT) is, for example, 200°C to 400°C. The baking time is not particularly limited, but it can be, for example, 3 to 180 seconds.

[0033] <Metal surface treatment film> The film formed by the above metal surface treatment method (hereinafter, sometimes simply referred to as "film") contains all of the components of the above metal surface treatment agent, excluding volatile components such as water. That is, the silicon content of the metal surface treatment film is 10 mass % or more. The molar ratio (M / Si) of the alkali metal element (M) to the silicon element (Si) contained in the metal surface treatment film is preferably 0.5 to 1.2. The vanadium content of the metal surface treatment film is preferably 0.1 to 10 mass %. The zirconium content of the metal surface treatment film is preferably 0.1 to 10 mass %. The film weight is not particularly limited, but is preferably 0.3 to 2.0 g / m 2 It is preferable that the density is 0.5 to 1.5 g / m 2 It is more preferable that:

[0034] <Surface-treated metal> The surface-treated metal according to this embodiment is obtained by forming the metal surface treatment film on the surface of the metal substrate. The surface-treated metal may be one in which a coating film is formed on the metal surface treatment film. The paint for forming the coating film is not particularly limited, and a one-coat paint or a primer and a top coat may be used. [Example]

[0035] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. However, Examples 6 and 14 are reference examples.

[0036] <Preparation of metal surface treatment agent> [Examples 1 to 36, Comparative Examples 1 to 4] The silicic acid compound (A), alkali metal salt (B), vanadium compound (C), zirconium compound (D), and chelating agent (E) were weighed out so as to obtain the solid content shown in Tables 1 to 4 below, and ion-exchanged water was added thereto so that the total solid content of these compositions in the metal surface treatment agent was 18 mass %, followed by mixing and stirring to obtain a metal surface treatment agent. The unit of the blending amount of each component shown in Tables 1 to 4 is parts by mass. The "Si content," "V content," and "Zr content" shown in Tables 1 to 4 respectively indicate the content (unit: mass %) of elemental silicon, elemental vanadium, and elemental zirconium relative to the total solid content of the metal surface treatment agent.

[0037] Details of the types of raw materials listed in Tables 1 to 4 are shown below.

[0038] (Silicate compound (A)) A1: J Sodium Silicate No. 3 (sodium silicate, manufactured by Nippon Chemical Industry Co., Ltd.) A2: Lithium silicate 35 (lithium silicate, SiO / LiO (molar ratio) = 3.5, manufactured by Nippon Chemical Industry Co., Ltd.) A3: Lithium silicate 75 (lithium silicate, SiO / LiO (molar ratio) = 7.5, manufactured by Nippon Chemical Industry Co., Ltd.) A4: 2K potassium silicate (potassium silicate, manufactured by Nippon Chemical Industry Co., Ltd.) A5: Hydrolysis product of ethyl silicate 28 (ethyl silicate, manufactured by Colcoat Co., Ltd.)

[0039] (Alkali metal salt (B)) B1: Sodium hydroxide B2: Sodium bicarbonate B3: Sodium carbonate B4: Lithium hydroxide monohydrate B5: Potassium hydroxide B6: Sodium nitrite B7: Lithium nitrite

[0040] (Vanadium Compounds (C)) C1: Vanadyl sulfate C2: Ammonium metavanadate C3: Sodium metavanadate

[0041] (Zirconium Compounds (D)) D1: Ammonium zirconium carbonate D2: Potassium zirconium carbonate D3: AZ Coat 5800MT (45% ammonium zirconium carbonate solution, manufactured by San Nopco Co., Ltd.) D4: ZSL-10A (zirconium oxide sol, pH 7.7, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) D5: Ammonium zirconate fluoride D6: Zirconium nitrate

[0042] (Chelating agent (E)) E1: Citric acid E2: Gluconic acid E3: 1-hydroxyethylidene-1,1-diphosphonic acid E4: Triethanolamine E5: Ethylenediaminetetraacetic acid

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] [Table 4]

[0047] [Storage stability test] The metal surface treatment agents shown in Tables 1 to 4 were left to stand in an incubator at 40°C for 7 days, and then the storage stability was visually evaluated according to the following criteria, with a score of 2 being acceptable. The results are shown in Tables 5 and 6. 2: The contents of the metal surface treatment agent have not settled. 1: The contents of the metal surface treatment agent have settled

[0048] <Preparation of test plate> Using the metal surface treatment agents shown in Tables 1 to 4, surface treatment was carried out on cold-rolled steel sheets (SPCC270SD, manufactured by Paltec Co., Ltd.) specified in JIS G3135 as metal substrates. The surface treatment was carried out as follows. First, the metal substrates were immersed in a solution prepared by adjusting the concentration of Surf Cleaner 53NF, manufactured by Nippon Paint Surf Chemicals Co., Ltd., at 45°C for 2 minutes to carry out a degreasing treatment. After the degreasing treatment, the metal substrates were washed with water and then dried. Next, the metal surface treatment agents shown in Tables 1 to 4 were applied to the surfaces of the metal substrates using a bar coater in a coating amount of 0.7 g / m. 2 The coated metal substrate was then baked in an oven at a temperature of 550°C for 15 seconds. The material reached temperature (PMT) during baking was 300°C. The test plates obtained in the above manner according to the examples and comparative examples were evaluated as follows.

[0049] <Evaluation> [Corrosion resistance (salt spray test (SST))] Each test plate was placed in a salt spray corrosion tester specified in JIS Z2317 for 4 hours, 8 hours, and 16 hours, and the area of ​​red rust was visually evaluated according to the following criteria, with a score of 2 or higher being considered a pass. The results are shown in Tables 5 and 6. 4: After 16 hours of SST, the area of ​​red rust is 5% or less of the test plate area 3: After 8 hours of SST, the area of ​​red rust is 5% or less of the test plate area 2: After 4 hours of SST, the area of ​​red rust is 5% or less of the test plate area 1: The area of ​​red rust after 4 hours of SST exceeds 5% of the test plate area.

[0050] [Table 5]

[0051] [Table 6]

[0052] The results in Tables 5 and 6 make the following clear: The test plates according to the Examples have better corrosion resistance results than the test plates according to Comparative Examples 1, 3, and 4, which do not contain any specific component, and the test plate according to Comparative Example 2, which has a silicon content of less than 10 mass%. In addition, the metal surface treatment agents according to the Examples have better storage stability than the surface treatment agents according to Comparative Examples 2 and 4.

Claims

1. a silicate compound (A); an alkali metal salt (B) other than silicate compounds, vanadium compounds, and zirconium compounds; a vanadium compound (C); a zirconium compound (D); water, The silicon element content is 20% by mass or more and 40% by mass or less relative to the total solid content of the metal surface treatment agent, The metal surface treatment agent, wherein the silicate compound (A) is an alkali metal silicate.

2. A silicate compound (A), an alkali metal salt (B) other than silicate compounds, vanadium compounds, and zirconium compounds; a vanadium compound (C); a zirconium compound (D); water, The silicon element content is 20% by mass or more and 40% by mass or less relative to the total solid content of the metal surface treatment agent, A metal surface treatment agent, wherein the molar ratio (M / Si) of alkali metal element (M) to silicon element (Si) contained in the solid content of the metal surface treatment agent is 0.5 to 1.

2.

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

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

5. A metal surface treatment film obtained by curing the metal surface treatment agent according to claim 1 or 2.

6. A surface-treated metal having the metal surface treatment film according to claim 5.

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