Metal surface treatment agent

Abstract

To provide a metal surface treatment agent that allows for high-temperature baking and can impart high corrosion resistance to metal substrates. [Solution] A metal surface treatment agent containing 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% by mass or more relative to the total solid content of the metal surface treatment agent. The silicate compound (A) is preferably an alkali metal silicate.

Description

Technical Field

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

Background Art

[0002] Conventionally, as a technique for imparting corrosion resistance to metal substrates such as steel, zinc phosphate treatment and zirconium-based chemical conversion treatment are known. Zinc phosphate treatment is used as a chemical conversion treatment for a painting base, but in recent years, it has a tendency to be avoided from the viewpoints of environmental protection and influence on the human body because it contains phosphorus, which is an eutrophication element, and nickel, which may be carcinogenic, as film components.

[0003] Zirconium-based chemical conversion treatment is a technique that has been conventionally applied to aluminum-based materials, and at present, there is still room for improvement in the technique of imparting high corrosion resistance to steel materials.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technique described in Patent Document 1 is a technique related to a surface-treated steel sheet, and the surface treatment film contains an acrylic resin emulsion. When the surface treatment film contains a resin component such as an acrylic resin emulsion as a main component, it is difficult to set the material reaching temperature (PMT) at the time of baking to a high temperature exceeding, for example, 200°C, and sufficient heat resistance and durability of the coating film cannot be obtained, and sufficient corrosion resistance after painting has not been obtained at present.

[0006] The present invention has been made in view of the above, and an object thereof is to provide a metal surface treatment agent that enables high-temperature baking and can impart high corrosion resistance to a metal substrate. [Means for solving the problem]

[0007] (1) The present invention relates to a metal surface treatment agent containing 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 content of silicon element is 10% by mass or more with respect to 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 alkali metal elements (M) to silicon elements (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% by mass and the zirconium element content is 0.1 to 10% by mass with respect to the total solid content of the metal surface treatment agent.

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

[0012] (6) A metal surface treatment film obtained by curing a metal surface treatment agent described in any of (1) to (5).

[0013] (7) A surface-treated metal having the metal surface treatment coating described in (6). [Effects of the Invention]

[0014] According to the present invention, a metal surface treatment agent can be provided that allows for high-temperature baking and can impart high corrosion resistance to a metal substrate. [Modes for carrying out the invention]

[0015] The following describes metal surface treatment agents according to embodiments of the present invention. The present invention is not limited to the embodiments described below.

[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 is also preferable that it contains a chelating agent (E).

[0017] (Silicate compound (A)) Silicate compound (A) is the main component of the film formed by the metal surface treatment agent. By making the main component of the film an inorganic compound, silicate compound (A) can be baked at high temperatures. Specific examples of 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, alkali metal silicates are preferred for silicate compound (A). Examples of alkali metal silicates include alkali metal salts of orthosilicic acid such as lithium orthosilicate, sodium orthosilicate, and potassium orthosilicate; and 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.

[0018] The silicon content of the metal surface treatment agent in this embodiment is 10% by mass or more relative to the total solid content. Preferably, the silicon content is 20% by mass or more and 40% by mass or less. A silicon content of 10% by mass or more makes it possible to bake the film formed by the metal surface treatment agent at a high temperature, for example, with a material maturation temperature (PMT) of 200°C or higher. If the silicon content exceeds 40% by mass, the amount of other essential components will decrease, making it difficult to exhibit the stability and corrosion resistance of the metal surface treatment agent.

[0019] (Alkali metal salt (B)) The alkali metal salt (B) is an alkali metal salt other than a silicate compound, a vanadium compound, and a zirconium compound, and acts as a crosslinking agent. When the alkali metal salt (B) is contained in the metal surface treatment agent, the barrier property of the formed film against water and corrosion factors (such as chloride ions) is improved, and as a result, the corrosion resistance imparted to the metal substrate can be improved. Specific examples of the alkali metal salt (B) are not particularly limited, and examples include carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate; bicarbonates such as lithium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate; hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; nitrites such as lithium nitrite, sodium nitrite, and potassium nitrite; and the like.

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

[0021] The content of vanadium element in the total solid content of the metal surface treatment agent of this embodiment is preferably 0.1 to 10% by mass. The content of the above vanadium element is more preferably 0.5 to 5% by mass. When the content of the vanadium element is less than 0.1% by mass, sufficient rust prevention property cannot be obtained. When the content of the vanadium element exceeds 10% by mass, the stability and corrosion resistance of the metal surface treatment agent decrease.

[0022] (Zirconium compound (D)) The zirconium compound (D) acts as a crosslinking agent to improve the barrier properties of the formed film against water and corrosion factors (such as chloride ions), and as a result, improves the corrosion resistance. The zirconium compound (D) is not particularly limited, and examples thereof include zirconium carbonate salts such as ammonium zirconium carbonate and potassium zirconium carbonate; alkali metal fluorozirconates such as K2ZrF6; zirconium hydrofluoride acid (H2ZrF6); ammonium zirconium fluoride ((NH4)2ZrF6); zirconium fluoride; zirconium nitrate; zirconium oxide; and the like.

[0023] With respect to the total solid content of the metal surface treatment agent of the present embodiment, the content of zirconium element is preferably 0.1 to 10% by mass. When the content of zirconium element is within 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% by mass. When the content of the zirconium element is less than 0.1% by mass, the effect as a sufficient crosslinking agent cannot be obtained. When the content of the zirconium element exceeds 10% by mass, the stability and corrosion resistance of the treatment agent decrease.

[0024] 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 of the present embodiment is preferably 0.5 to 1.2. The molar ratio (M / Si) is more preferably 0.6 to 1.1. When the molar ratio (M / Si) is less than 0.5, the corrosion resistance decreases. When 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 the zirconium in the metal surface treatment agent. The chelating agent (E) is not particularly limited, but examples include 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 include an organophosphorus compound such as HEDP mentioned above, but from the viewpoint of reducing environmental impact due to eutrophication, the metal surface treatment agent according to this embodiment is preferably free from phosphoric acids such as orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), and metaphosphoric acid (HPO3), and inorganic phosphorus compounds such as phosphates such as ammonium phosphate and sodium phosphate.

[0027] (Other ingredients) The metal surface treatment agent of this embodiment contains water as an additional component. Furthermore, the metal surface treatment agent may contain other components as long as they do not impair the above-mentioned functions. 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 above-mentioned resin components are included 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, and more preferably 5% by mass or less. This allows for favorable high-temperature baking of the metal surface treatment agent. Other components not mentioned above include known components contained in surface treatment agents such as crosslinking agents, rust inhibitors, leveling agents, defoaming agents, and pH adjusters.

[0028] (Solid content) The solid content of the metal surface treatment agent in this embodiment is preferably 0.1 to 30% by mass, and more preferably 1.0 to 25% by 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, but examples include cold-rolled steel, hot-rolled steel, stainless steel, electro-galvanized 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 nickel plated steel. The shape of the metal substrate is not particularly limited, but examples include a plate shape.

[0030] <Metal surface treatment methods> The metal surface treatment agent of this embodiment is a so-called coating-type metal surface treatment agent. The coating-type metal surface treatment agent is 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 washing it with water. That is, the metal surface treatment method of this embodiment comprises a coating step of applying the metal surface treatment agent to the surface of a metal substrate, and a baking step of baking the metal surface treatment agent applied to the metal substrate. The coating-type metal surface treatment agent of this embodiment has the advantage of being able to form a metal surface treatment film relatively easily and not generating waste liquid.

[0031] In the coating process, the method of applying the metal surface treatment agent to the surface of the metal substrate is not particularly limited, and examples include roll coating, bar coating, spraying, and immersion. Prior to the coating process, degreasing, pickling, or etching may be performed on the surface of the metal substrate as needed.

[0032] In the baking process, the metal surface treatment agent applied to the metal substrate after the coating process is baked. The baking method is not particularly limited. The baking temperature is not particularly limited, but is preferably 200°C to 400°C, for example, in terms of the material temperature (PMT). The baking time is not particularly limited, but can be, for example, 3 to 180 seconds.

[0033] <Metal surface treatment coating> The film formed by the above metal surface treatment method (hereinafter sometimes simply referred to as "film") contains all components of the above-mentioned metal surface treatment agent, excluding volatile components such as water. Specifically, the silicon content in the metal surface treatment film is 10% by mass or more. The molar ratio (M / Si) of alkali metal elements (M) to silicon elements (Si) in the metal surface treatment film is preferably 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 / m². 2 Preferably, it is 0.5 to 1.5 g / m 2 It is preferable that it be so.

[0034] <Surface-treated metals> The surface-treated metal according to this embodiment is formed by forming the metal surface treatment film on the surface of the metal substrate. The surface-treated metal may also be formed by forming a coating film on the metal surface treatment film. The paint used to form the coating film is not particularly limited, and a one-coat paint may be used, or a primer and topcoat may be used. [Examples]

[0035] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0036] <Preparation of metal surface treatment agent> [Examples 1-36, Comparative Examples 1-4] The silicate compound (A), alkali metal salt (B), vanadium compound (C), zirconium compound (D), and chelating agent (E) were weighed to obtain the solid content shown in Tables 1 to 4 below. Ion-exchanged water was added and mixed and stirred so that the total solid content concentration of these compositions in the metal surface treatment agent was 18% by mass, thereby obtaining the metal surface treatment agent. The units of the blending amounts of each component listed in Tables 1 to 4 are parts by mass. The "Si amount," "V amount," and "Zr amount" listed in Tables 1 to 4 indicate the content of silicon, vanadium, and zirconium elements relative to the total solid content of the metal surface treatment agent (unit: mass%).

[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 Industrial Co., Ltd.) A2: Lithium silicate 35 (Lithium silicate, SiO2 / Li2O (molar ratio) = 3.5, manufactured by Nippon Chemical Industrial Co., Ltd.) A3: Lithium silicate 75 (Lithium silicate, SiO2 / Li2O (molar ratio) = 7.5, manufactured by Nippon Chemical Industrial Co., Ltd.) A4: 2K Potassium Silicate (manufactured by Nippon Chemical Industrial 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 compound (C)) C1: Vanadyl sulfate C2: Ammonium metavanadate C3: Sodium metavanadate

[0041] (Zirconium compound (D)) D1: Zirconium carbonate ammonium D2: Potassium Zirconium Carbonate D3: AZ Coat 5800MT (45% Zirconium Ammonium Carbonate Solution, manufactured by Sunopco Co., Ltd.) D4: ZSL-10A (Zirconium oxide sol, pH 7.7, manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.) D5: Zirconium fluoride D6: Zirconium nitrate

[0042] (Chelating agent (E)) E1: Citric Acid E2: Gluconate 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] After allowing the metal surface treatment agents shown in Tables 1 to 4 to stand in a 40°C incubator for 7 days, their storage stability was visually evaluated according to the following criteria, with a score of 2 being considered 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 panels> The metal surface treatment agents shown in Tables 1 to 4 were used to surface-treat cold-rolled steel sheets (SPCC270SD, manufactured by Paltec Co., Ltd.) specified in JIS G3135 as the metal substrate. The surface treatment was carried out in the following procedure. First, the metal substrate was immersed in a 2% solution of Surf Cleaner 53NF, manufactured by Nippon Paint Surf Chemicals Co., Ltd., at 45°C for 2 minutes to degrease it. After degreasing, the metal substrate was washed with water and dried. Next, the metal surface treatment agents shown in Tables 1 to 4 were applied to the surface of the metal substrate using a bar coater, with a film thickness of 0.7 g / m². 2 The coating was applied in the manner described above. Next, the coated metal substrate was heated in an oven at 550°C for 15 seconds to bake it. The material temperature reached during baking (PMT) was 300°C. The following evaluations were performed using the test plates obtained for each example and comparative example described above.

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

[0050] [Table 5]

[0051] [Table 6]

[0052] The results in Tables 5 and 6 clearly show the following: The test plates according to the Examples exhibit superior corrosion resistance compared to the test plates according to Comparative Examples 1, 3, and 4, which do not contain specific components, and to the test plate according to Comparative Example 2, which has a silicon content of less than 10% by mass. Furthermore, the metal surface treatment agents according to the Examples exhibit superior storage stability compared to the surface treatment agents according to Comparative Examples 2 and 4.

Claims

1. Silicate compound (A) and Alkali metal salts (B) other than silicate compounds, vanadium compounds, and zirconium compounds, Vanadium compounds (C) and Zirconium compound (D) and It contains water, A metal surface treatment agent having a silicon element content of 10% by mass or more relative to the total solid content of the metal surface treatment agent.

2. The metal surface treatment agent according to claim 1, wherein the silicic acid compound (A) is an alkali metal silicate.

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

2.

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

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

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

7. A surface-treated metal having the metal surface treatment film described in claim 6.

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