Metal surface cleaning agent, coated article, metal surface cleaning method, and method for producing coated article

Abstract

To provide a metal surface cleaning agent that exhibits superior adhesion to metal surfaces.SOLUTION: A metal surface cleaning agent comprises a hydrocarbon compound that dissolves oil, an organic acid aqueous solution that dissolves metal, and an amphiphilic solvent for mixing the hydrocarbon compound and the organic acid aqueous solution.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a metal surface cleaning agent, a coated body, a metal surface cleaning method, and a method for producing a coated body. [Background technology]

[0002] Many structures, including buildings and moving objects, are painted for the purpose of providing design and protection. In particular, in moving objects such as railroad cars and automobiles, it is necessary to smooth the coating surface in order to provide aesthetic appearance and reduce aerodynamic resistance. It is common to treat the surface to be painted before applying such a coating. For example, physical treatments such as blasting and polishing, phosphate treatment and zirconium treatment are performed on metals, and cleaning is required before and after these treatments to remove degreasing and foreign matter attached to the surface.

[0003] In these surface treatment techniques, the powder and abrasive dust used in blasting remain on the surface of the substrate, causing problems such as peeling of the coating, while in chemical conversion treatment, multiple tanks such as a cleaning tank, a treatment tank, and a rinsing tank are required. Large tanks are required for large products such as railroad cars, and large amounts of waste liquid are generated.

[0004] In addition, before and after these surface treatments, surface cleaning is required to remove degreasing and foreign matter adhering to the surface, and a removal composition using an organic solvent has been proposed as a method for this purpose (see, for example, Patent Document 1). This technology is expected to be effective in removing dirt and stains without causing discoloration of the aluminum surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-031716 Summary of the Invention [Problem to be solved by the invention]

[0006] When cleaning the surface of a metal to be coated using the conventional techniques described above, it is important to not only degrease but also to remove any foreign matter adhering to the surface. If the oil and foreign matter adhering to the surface cannot be removed with a surface cleaner, the paint film will not adhere to the metal surface and the paint will peel off.

[0007] An object of the present invention is to provide a metal surface cleaner having excellent adhesion to metal surfaces. [Means for solving the problem]

[0008] A metal surface cleaning agent according to one embodiment of the present invention is a metal surface cleaning agent for cleaning a metal surface, and is characterized by comprising a hydrocarbon compound that dissolves oil, an organic acid aqueous solution that dissolves the metal, and an amphipathic solvent for miscible mixing of the hydrocarbon compound and the organic acid aqueous solution. Effect of the Invention

[0009] According to one aspect of the present invention, a metal surface cleaner having excellent adhesion to a metal surface can be provided. [Brief description of the drawings]

[0010] [Figure 1A] 1 is a schematic cross-sectional view of a coating film illustrating an embodiment of the present invention. [Figure 1B] FIG. 4 is a schematic cross-sectional view of a coating film showing another embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram showing a vehicle having a painted part. [Diagram 3] FIG. 1 is a diagram showing Table 1-1. [Figure 4] FIG. 1 is a diagram showing Table 1-2. [Diagram 5] FIG. 1 is a diagram showing Table 1-3. [Figure 6] FIG. 1 is a diagram showing Table 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The vehicle according to the embodiment of the present invention is, for example, a vehicle having a painted part whose surface is painted, and the painted part includes a metal structure and a paint film that have been cleaned with a metal surface cleaner. Note that a surface treatment such as a silane coupling treatment may be performed between the metal structure surface and the paint film.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiment shown in the drawings. In addition, the configuration of the vehicle other than the painted parts is the same as the configuration of the vehicle according to the known technology, so a detailed description thereof will be omitted.

[0013] FIG. 2 shows a vehicle having a painted part.

[0014] As shown in FIG. 2, vehicle 401 is a vehicle having a painted portion 405 on its surface, where 402 is a wheel, 403 is a side sliding door, 404 is a window, and 406 is a pantograph.

[0015] The configuration of the coating unit 405 will be described with reference to Figures 1A and 1B. Figure 1A is a schematic cross-sectional view of a coating film showing an embodiment of the present invention. Figure 1B is a schematic cross-sectional view of a coating film showing another embodiment of the present invention.

[0016] As shown in FIG. 1A, the coated portion 405 has a metal structure 11 whose surface has been cleaned with a metal surface cleaner, and a coating film 31 provided on a cleaning surface 21 that has been cleaned with the metal surface cleaner.

[0017] Also, as shown in FIG. 1B, the painted portion 405 has a metal structure 11 whose surface has been cleaned with a metal surface cleaning agent, a surface treatment layer 32 provided on a cleaning surface 21 cleaned with the metal surface cleaning agent, and a paint film 31 provided on the surface treatment layer 32.

[0018] The metal cleaning agent is composed of a hydrocarbon compound, an organic acid aqueous solution, and an amphipathic organic solvent. Here, the hydrocarbon compound, the organic acid aqueous solution, and the amphipathic solvent are each preferably volatile. When the surface cleaning agent contains a large amount of non-volatile components, rinsing is required to remove the surface cleaning agent, and equipment for treating a large amount of rinse waste liquid is also required. By configuring the hydrocarbon compound, the organic acid aqueous solution, and the amphipathic solvent to be volatile, rinsing is not required to remove the surface cleaning agent, and equipment for treating a large amount of rinse waste liquid is also not required.

[0019] The metal structure 11 is made of, for example, a metal plate formed from a metal material to match the shape of an object. There is no particular limitation on the metal material constituting the metal structure 11. As the metal material, for example, steel, aluminum alloy, stainless steel, duralumin, etc., or CFRP (carbon reinforced plastic), GFRP (glass fiber reinforced plastic), etc. can also be partially used.

[0020] The metal structure 11 can be washed with a cleaning agent to expose a clean wash surface 21, and when a surface treatment agent such as a silane coupling agent is used, the reaction between the surface treatment agent and the metal surface can be ensured, thereby ensuring adhesion with the paint film.

[0021] Hydrocarbon compounds are components used to remove oil that is applied or adheres mainly to metal surfaces during storage or processing of metals. It is preferable that the hydrocarbon compound is volatile so that rinsing is not required and so that it does not remain and adversely affect the adhesion between the metal surface and the painted surface.

[0022] Hydrocarbon compounds are broadly classified into aliphatic, alicyclic, and aromatic. Any of them can be used, but aliphatic and alicyclic compounds are preferred because they have less impact on the human body and the environment. The aliphatic compounds are preferably linear or branched compounds with 5 to 20 carbon atoms, and may be a single compound or a mixture. The alicyclic compounds are preferably compounds with 5 to 20 carbon atoms and a cyclic structure as a chemical structure, similar to the aliphatic compounds, and the hydrocarbons bonded to the cyclic structure are preferably linear or branched compounds, and may be a single compound or a mixture. The aromatic compounds are preferably compounds with 6 to 20 carbon atoms, and the hydrocarbons bonded to the aromatic ring are preferably linear or branched compounds.

[0023] These hydrocarbon compounds have a similar chemical structure to machine oils that adhere to metal surfaces, and are excellent at dissolving and removing machine oils. In addition, they have very low surface tension and excellent wettability to oily surfaces, so the cleaning agent spreads over the metal surface and reduces leaks due to cissing.

[0024] Organic acids can remove dirt adhering to the surface by etching the metal oxide film present on the metal surface, which affects the adhesion of the paint film, and can also ensure the adhesion of the paint film by exposing a new surface. In addition, when a surface treatment agent is used, the reaction between the surface treatment agent and the metal surface can be ensured.

[0025] The organic acid is preferably a compound having one or more carbon atoms and one or more functional carboxyl groups. In order to promote acid dissociation, the organic acid may be made into an aqueous solution by coexisting with water. The organic acid is preferably volatile so that rinsing is not required and so that the organic acid does not remain and adversely affect the adhesion between the metal surface and the coating surface. The organic acid may also be mixed with water to be used as an aqueous solution.

[0026] The above-mentioned hydrocarbon compounds and organic acids are not compatible when simply mixed together, so an amphipathic solvent is used as an admixture. The admixture is preferably volatile. As an admixture, an organic solvent having one or more functional polar groups is preferable. By adding an admixture, the cleaning agent can be made compatible, emulsified or suspended to become a homogenous liquid that does not separate. If the homogenization is insufficient, the liquid will separate into two layers, and each of the separated liquids will come into contact with the metal surface, causing uneven degreasing or etching and causing problems such as paint peeling.

[0027] Examples of the hydrocarbon compound include aliphatic compounds having 5 to 20 carbon atoms, such as pentane, hexane, heptane, and octane, and isomers of these compounds having a branched structure. Examples of the alicyclic compounds include compounds having 5 to 20 carbon atoms and a cyclic structure, such as cyclopentane, cyclohexane, cycloheptane, cyclooctane, methylcyclohexane, ethylcyclohexane, and propylcyclohexane. Examples of the aromatic compounds include compounds having 5 to 20 carbon atoms and an aromatic ring structure, such as toluene, ethylbenzene, xylene, and cumene. Also, a mixture of any of aliphatic, alicyclic, and aromatic compounds may be used.

[0028] As organic acids, for example, compounds having one or more carbon atoms and one or more functional carboxyl groups include carboxylic acids such as formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexylic acid, heptanoic acid, and octanoic acid, and hydroxycarboxylic acids such as lactic acid. In addition to these, isomers of these having a branched structure may also be used. In addition to the above organic acids alone, mixtures of these may also be used. Although not particularly limited, it is desirable that the organic acids are volatile. If they are not volatile, they will remain on the metal surface after cleaning and cause metal corrosion, or a rinse solution will be used to prevent them from remaining, which will cause a large amount of waste liquid to be generated. They can also be used as an aqueous solution.

[0029] As the amphipathic solvent, a solvent that dissolves in a hydrocarbon compound and an aqueous solution of an organic acid is preferable. For example, there are compounds having one or more functional hydroxyl groups, such as alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, and terpineol, ethylene glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether, propylene glycols such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether, and hydroxy esters such as methyl lactate, ethyl lactate, propyl lactate, and butyl lactate.

[0030] The cleaning agent preferably contains 40-95% by mass of the hydrocarbon compound, 1-30% by mass of the organic acid aqueous solution, and 2-60% by mass of the amphipathic solvent. If the amount of the hydrocarbon compound is less than 40% by mass, the removal of oil is insufficient, and if it exceeds 95% by mass, it becomes difficult to mix with the organic acid aqueous solution. The concentration of the organic acid in the organic acid aqueous solution is 1-100% by mass. If the amount of the organic acid aqueous solution is less than 1% by mass, the removal of metal oxides is insufficient, and if it exceeds 30% by mass, it becomes difficult to mix with the hydrocarbon compound.

[0031] If the amount of the amphipathic solvent is less than 2% by mass, the hydrocarbon compound and the organic acid aqueous solution will not be mixed sufficiently, making it difficult to homogenize them. If the amount of the amphipathic solvent is more than 60% by mass, the content of the hydrocarbon compound will be reduced and the amount of the organic acid aqueous solution will also be reduced, making it difficult to remove the oil and etch the metal surface.

[0032] The coating film 31 is a coating film provided on the surface treatment layer. The coating film 31 can be configured to have, for example, a paint having an anticorrosive function for preventing corrosion of the metal structure 11, or a base coating such as putty applied relatively thickly for correcting the uneven shape of the surface of the metal structure 11, and a paint having a smooth and vivid color formed on the base coating. The coating film 31 may be configured as a single layer or multiple layers.

[0033] The thickness of the coating film 31 can be appropriately selected depending on the type of the coating film 31. For example, when the coating film 31 is a coating film intended to prevent rust and improve the design of a metal structure, it may have a thickness of 10 μm to 1000 μm.

[0034] Next, a method for forming the painted portion 405 of the vehicle 401 will be described.

[0035] First, a metal structure 11 formed into a predetermined shape is prepared, and a coating film 31 is formed on this metal structure 11. The coating film 31 is formed by applying paint to the metal structure 11 and drying it, but before the coating, dirt and the like adhering to the surface of the metal structure 11 is removed by cleaning with a surface treatment agent to form a cleaned surface 21.

[0036] Cleaning removes oil, dirt, and metal oxides from the metal surface by contacting the metal surface with a cleaning agent that is a mixture of the above-mentioned hydrocarbon compounds, organic acids, and amphipathic solvents. Methods for contacting the metal surface include, but are not limited to, wiping with a cloth soaked in the cleaning agent, spraying or applying the cleaning agent with a spray, brush, roller, etc., and dipping the metal in the cleaning agent.

[0037] The painted portion 405 of the vehicle 401 manufactured as described above can maintain strong adhesion between the metal structure 11 and the paint film 31 for a long period of time without any foreign matter between them. As a result, peeling of the paint film 31 and corrosion of the metal structure 11 can be prevented.

[0038] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0039] <Preparation of painting part> The materials used in the examples and comparative examples are shown below. EXAMPLES

[0040] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of an aqueous solution of acetic acid with a concentration of 99 mass% as an aqueous organic acid solution (b), and 30 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 1 was obtained.

[0041] For Examples 2 to 10, coating films were prepared in the same manner as in Example 1 using [A] a metal structure, [B] a surface treatment agent, and [C] a paint as shown in Table 1-1 in FIG. 3 and Table 1-2 in FIG. 4, and results were obtained. EXAMPLES

[0042] [A] Metal structure (A-1) Metal material: Stainless steel, thickness: 3mm, surface shape: flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 10 mass% concentration of lactic acid aqueous solution as an organic acid aqueous solution (b), and 30 mass% of ethylene glycol monobutyl ether as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 2 was obtained. EXAMPLES

[0043] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a lactic acid aqueous solution having a concentration of 1 mass% as an organic acid aqueous solution (b), and 30 mass% of propylene glycol monopropyl ether as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 3 was obtained. EXAMPLES

[0044] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% concentration of lactic acid aqueous solution as an organic acid aqueous solution (b), and 10 mass% of α-terpineol and 20 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 4 was obtained. EXAMPLES

[0045] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 40 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% concentration of lactic acid aqueous solution as an organic acid aqueous solution (b), and 50 mass% of propylene glycol monopropyl ether as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 5 was obtained. EXAMPLES

[0046] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 95% by mass of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 1% by mass of a 50% by mass aqueous solution of lactic acid as an aqueous organic acid solution (b), and 4% by mass of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 6 was obtained. EXAMPLES

[0047] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 30 mass% of a lactic acid aqueous solution having a concentration of 50 mass% as an organic acid aqueous solution (b), and 10 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 7 was obtained. EXAMPLES

[0048] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 95% by mass of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 3% by mass of a 50% by mass aqueous solution of lactic acid as an aqueous organic acid solution (b), and 2% by mass of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 8 was obtained. EXAMPLES

[0049] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 30 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% aqueous lactic acid solution as an aqueous organic acid solution (b), and 60 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 9 was obtained. EXAMPLES

[0050] [A] Metal structure (A-1) Metal material: Aluminum alloy (A5052), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of naphthenic hydrocarbon (Naphthesol 200 manufactured by ENEOS) as the hydrocarbon compound (a), 10 mass% of an aqueous solution of acetic acid with a concentration of 50 mass% as the aqueous organic acid solution (b), and 30 mass% of 1-butanol as the amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint: Urethane resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 10 was obtained. EXAMPLES

[0051] [A] Metal structure (A-1) Metal material: Aluminum alloy (A6N01), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% aqueous lactic acid solution as an aqueous organic acid solution (b), and 30 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 11 was obtained. EXAMPLES

[0052] [A] Metal structure (A-1) Metal material: Iron (SPCC), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% aqueous lactic acid solution as an aqueous organic acid solution (b), and 30 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 12 was obtained. EXAMPLES

[0053] [A] Metal structure (A-1) Metal material: Aluminum alloy (A6N01), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% aqueous lactic acid solution as an aqueous organic acid solution (b), and 30 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. (B-2) Treatment agent: A 1% by mass aqueous solution of an amino group-containing silane coupling agent (KBM-603, manufactured by Shin-Etsu Silicones) was applied and heat-treated at 50°C to treat the metal structure. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 13 was obtained. EXAMPLES

[0054] [A] Metal structure (A-1) Metal material: Aluminum alloy (A6N01), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% aqueous lactic acid solution as an aqueous organic acid solution (b), and 30 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. (B-2) Treatment agent: A 1% by mass aqueous solution of an amino group-containing silane coupling agent (KBM-603, manufactured by Shin-Etsu Silicones) was applied and heat-treated at 50°C to treat the metal structure. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 14 was obtained. EXAMPLES

[0055] [A] Metal structure (A-1) Metal material: Iron (SPCC), Thickness: 3mm, Surface shape: Flat (no steps) [B] Surface treatment agent (B-1) Cleaning agent: 60 mass% of paraffinic hydrocarbon (NS Clean 100 manufactured by ENEOS Corporation) as a hydrocarbon compound (a), 10 mass% of a 50 mass% aqueous lactic acid solution as an aqueous organic acid solution (b), and 30 mass% of 1-butanol as an amphipathic solvent (c) were mixed to prepare a homogeneous liquid. (B-2) Treatment agent: A 1% by mass aqueous solution of an amino group-containing silane coupling agent (KBM-603, manufactured by Shin-Etsu Silicones) was applied and heat-treated at 50°C to treat the metal structure. [C]Paint (C-1) Solution-based paint Epoxy resin paint (manufactured by Nippon Paint Co., Ltd.) The surface of the metal material (A-1) as the metal structure was degreased using the surface treatment agent [B]. After sufficient drying, the solution-based paint (C-1) was applied and heated at 50°C to prepare a coating film with a thickness of 50 μm, and Example 15 was obtained.

[0056] For Examples 2 to 12, coating films were prepared in the same manner as in Example 1 using [A] a metal structure, [B] a surface treatment agent, and [C] a paint as shown in Table 1-1 in FIG. 3 and Table 1-2 in FIG. 4, and results were obtained.

[0057] For Examples 13 to 15, a coating film was prepared in the same manner as in Example 1 using [A] a metal structure, [B] a surface treatment agent, and [C] a paint as shown in Table 1-3 in FIG. 5, and the results were obtained.

[0058] [Comparative Example 1] As in Example 1, the surface of the metal material (A-1) serving as the metal structure was degreased using a paraffin-based hydrocarbon (NS Clean 100, manufactured by ENEOS Corporation) as shown in Table 2 of Fig. 5. The solution-based paint (C-1) was applied to the thoroughly dried surface, and a coating film having a thickness of 50 µm was produced by heat treatment at 50°C, and Comparative Example 1 was obtained.

[0059] [Comparative Example 2] As shown in Table 2, degreasing was performed using a 50% by mass aqueous solution of lactic acid. A solution-based paint (C-1) was applied to the sufficiently dried surface, and a heat treatment was performed at 50° C. to prepare a coating film with a thickness of 50 μm, and Comparative Example 2 was obtained.

[0060] [Comparative Example 3] As shown in Table 2, degreasing was performed using ethylene glycol monobutyl ether, which is an amphipathic solvent. A solution-based paint (C-1) was applied to the thoroughly dried surface, and a coating film with a thickness of 50 μm was prepared by heat treatment at 50° C., and Comparative Example 3 was obtained.

[0061] <Evaluation> [Adhesion] Adhesion was evaluated for Examples 1 to 12 and Comparative Examples 1 to 3 by a cross-cut test (JIS K 5600-5-6). Adhesion was also evaluated for samples left stationary in an environment at a temperature of 85°C and a relative humidity of 85%. In the Examples, no peeling occurred in any case, and highly reliable and good adhesion was demonstrated. On the other hand, partial peeling was observed in Comparative Examples 1 to 5, and good adhesion could not be obtained.

[0062] [Neutral salt spray resistance] For Examples 1 to 12 and Comparative Examples 1 to 3, neutral salt spray resistance (JIS K 5600-7-1) was evaluated. A cross cut was made 20 mm or more away from the end of the test piece, reaching the base material, and after leaving it in 5% NaCl at 35°C for 240 hours, the area around the cross cut was checked for abnormalities such as cracks, blisters, and whitening, and the width of any abnormalities was recorded. A value of 3.0 mm or less was deemed to pass.

[0063] An embodiment of the present invention is a metal surface cleaner comprising a hydrocarbon compound for removing oil adhering to a metal surface, an organic acid for etching the metal surface, and an amphipathic organic solvent for misciblely mixing the hydrocarbon compound and the organic acid.

[0064] According to the embodiment of the present invention, it is possible to provide an excellent metal surface cleaner for ensuring good adhesion between a metal surface and a coating, thus realizing a metal surface treatment having excellent adhesion to the metal surface.

[0065] In addition, in an embodiment of the present invention, the hydrocarbon compound, the organic acid aqueous solution, and the amphipathic solvent of the metal surface cleaning agent are each volatile, thereby eliminating the need for rinsing to remove the surface cleaning agent, and also eliminating the need for equipment to treat large amounts of rinse waste liquid. [Explanation of symbols]

[0066] 11 Metal structures 21 Cleaning surface 31 Paint film 32 Surface treatment layer 401 vehicles 402 wheels 403 Side sliding door 404 Windows 405 Painting Department 406 Pantograph

Claims

1. A metal surface cleaner for cleaning a metal surface, comprising: A hydrocarbon compound that dissolves oil; an aqueous solution of an organic acid that dissolves the metal; an amphipathic solvent for miscible mixing of the hydrocarbon compound with the aqueous solution of an organic acid; A metal surface cleaning agent comprising:

2. 2. The metal surface cleaning solvent according to claim 1, wherein the hydrocarbon compound, the organic acid aqueous solution and the amphipathic solvent are each volatile.

3. The hydrocarbon compound is 3. The metal surface cleaning solvent according to claim 2, characterized in that it is made of any one of aliphatic, alicyclic and aromatic compounds having 5 to 20 carbon atoms.

4. The organic acid aqueous solution is 3. The metal surface cleaning solvent according to claim 2, characterized in that the solvent comprises an organic acid, which is a compound having one or more carbon atoms and one or more functional carboxyl groups, and the concentration of the organic acid is 1 to 100 mass %.

5. The amphiphilic solvent is 3. The metal surface cleaning solvent according to claim 2, wherein the solvent soluble in the hydrocarbon compound and the aqueous organic acid solution has one or more carbon atoms and one or more functional hydroxyl groups.

6. The metal surface cleaner is 40 to 95 mass % of the hydrocarbon compound; 1 to 30% by mass of the organic acid aqueous solution; 2 to 60% by weight of the amphiphilic solvent; 2. The metal surface cleaning solvent of claim 1, comprising:

7. A coated body having a coated portion in which a coating is applied to a metal surface, The coating section includes: A metal structure whose surface has been cleaned with a metal surface cleaner; a coating film provided on a surface that has been cleaned with the metal surface cleaning agent; having The metal surface cleaner is A hydrocarbon compound that dissolves oil; an aqueous solution of an organic acid that dissolves the metal; an amphipathic solvent for miscible mixing of the hydrocarbon compound with the aqueous solution of an organic acid; A coated body characterized by having the following:

8. 8. The coated body according to claim 7, wherein the hydrocarbon compound, the organic acid aqueous solution and the amphipathic solvent are each volatile.

9. The coated body according to claim 7, characterized in that a surface treatment layer is provided between the cleaning surface of the metal structure and the coating film.

10. The painted body according to claim 7, characterized in that the painted body having the painted portion is a railway vehicle.

11. A metal surface cleaning method for cleaning a metal surface with a metal surface cleaner, comprising: The metal surface cleaner is A hydrocarbon compound that dissolves oil; an aqueous solution of an organic acid that dissolves the metal; an amphipathic solvent for miscible mixing of the hydrocarbon compound with the aqueous solution of an organic acid; A method for cleaning a metal surface, comprising the steps of:

12. 12. The method of claim 11, wherein the hydrocarbon compound, the organic acid aqueous solution, and the amphipathic solvent are each volatile.

13. Cleaning the surface of the metal with the metal surface cleaner; The method for cleaning a metal surface according to claim 11, further comprising forming a coating film on the surface to be cleaned.

14. A method for producing a coated body, comprising forming a coating film on a surface that has been cleaned using the metal surface cleaning agent according to claim 1.

15. forming a surface treatment layer on the cleaning surface formed by the metal surface cleaning agent; The method for producing a coated body according to claim 14, characterized in that the coating film is formed on the surface treatment layer.

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