Method for manufacturing surface-treated metal member

Abstract

The present disclosure addresses the problem of providing a method for manufacturing a surface-treated metal member, wherein a preferable corrosion resistance property of the surface-treated metal member can be achieved and defects in appearance can be suppressed. A method for producing a surface-treated metal member according to one embodiment of the present disclosure includes a degreasing water washing step, a surface treatment agent contact step, and a drying step, wherein an aqueous surface treatment agent includes a silicon-including compound (A) which does not include a polar functional group other than a silanol group, a water-soluble amino group-including compound (B), and water, the mass concentration of (A+B), which is the total mass concentration of the silicon-including compound (A) and the water-soluble amino group-including compound (B) in the aqueous surface treatment agent, is within the range 1-30 g / L, and the value of the mass concentration ratio {A / (A+B)} of the silicon-including compound (A) relative to the total mass concentration (A+B) of the silicon-including compound (A) and the water-soluble amino group-including compound (B) in the aqueous surface treatment agent is in the range 45-95%.

Description

Method for manufacturing surface-treated metal members

[0001] The present invention relates to a method for producing a surface-treated metal member.

[0002] Conventionally, when painting the surface of a metal member, a chemical conversion treatment is usually carried out to form a chemical conversion coating on the surface of the metal member before painting, with the aim of imparting corrosion resistance, paint film adhesion, etc. to the metal member.

[0003] Conventional chemical conversion treatments have been performed using phosphate-based surface treatment agents or zirconium-based surface treatment agents that do not contain harmful heavy metals such as nickel. However, conventional surface treatment agents have had problems such as the inability to be used at room temperature, the generation of chemical conversion sludge as a by-product, and the need for one or more water washing steps after chemical conversion treatment, which increases the treatment time and cost. Therefore, in recent years, a paint-type surface treatment agent that can solve the above problems has been proposed (see, for example, Patent Document 1).

[0004] International Publication No. 2022 / 264949

[0005] When the time interval between contacting the surface treatment agent with the metal member and drying is long, the application-type surface treatment agent as disclosed in Patent Document 1 may cause dripping of the surface treatment agent or pooling of the surface treatment agent in the processed portion of the metal member. If dripping of the surface treatment agent occurs, there is a risk that the corrosion resistance of the metal member may be partially reduced. If pooling of the surface treatment agent occurs, there is a risk that the appearance of the metal member may be poor.

[0006] The present invention has been made in view of the above, and has as its object to provide a method for producing a surface-treated metal member that can provide a surface-treated metal member with desirable corrosion resistance and can suppress defects in appearance.

[0007] (1) The present disclosure provides a method for producing a surface-treated metal member, the method comprising: a degreasing and water-washing step of degreasing a metal member and then rinsing it with water to form a degreased and water-washed metal member; a surface-treatment-agent contacting step of contacting the degreased and water-washed metal member with an aqueous surface treatment agent to form a metal member having a liquid film on its surface; and a drying step of drying the liquid film on the metal member having the liquid film on its surface to form a coating, the aqueous surface treatment agent comprising a silicon-containing compound (A) containing no polar functional groups other than silanol groups, a water-soluble amino group-containing compound (B) and water, wherein the total mass concentration of the silicon-containing compound (A) and the water-soluble amino group-containing compound (B), that is, the mass concentration of (A+B), in the aqueous surface treatment agent is within the range of 1 to 30 g / L, and the mass concentration ratio of the silicon-containing compound (A) to the total mass concentration (A+B) of the silicon-containing compound (A) and the water-soluble amino group-containing compound (B), {A / (A+B)}, in the aqueous surface treatment agent is within the range of 45 to 95%.

[0008] (2) The method for producing a surface-treated metal member according to (1), wherein the metal member is a processed and molded member.

[0009] (3) The method for producing a surface-treated metal member according to (1) or (2), wherein the silicon-containing compound (A) is a silicon-containing compound having two or more silanol groups in one molecule.

[0010] (4) The method for producing a surface-treated metal member according to any one of (1) to (3), wherein the silicon-containing compound (A) is 1,2-bis(triethoxysilyl)ethane.

[0011] (5) The method for producing a surface-treated metal member according to any one of (1) to (4), wherein the water-soluble amino group-containing compound (B) is an aminosilane or an amine-modified epoxy resin.

[0012] (6) The method for producing a surface-treated metal member according to any one of (1) to (5), wherein the time interval between the end of the contact step with the surface treatment agent and the start of the drying step is 30 seconds or more.

[0013] (7) The amount of the film formed by the aqueous surface treatment agent after drying is 1 to 100 mg / m２ The method for producing a surface-treated metal member according to any one of (1) to (6), wherein the range is:

[0014] According to the present invention, a method for producing a surface-treated metal member can be provided that can provide a surface-treated metal member with favorable corrosion resistance and can suppress defects in appearance.

[0015] The method for producing a surface-treated metal member according to an embodiment of the present invention will be described below, but the present invention is not limited to the description of the following embodiment.

[0016] [Method for manufacturing a surface-treated metal member] The method for manufacturing a surface-treated metal member according to this embodiment includes a degreasing and water-washing step, a surface treatment agent contact step, and a drying step. Because the method for manufacturing a surface-treated metal member according to this embodiment includes a surface treatment agent contact step using a coating-type aqueous surface treatment agent, unlike zinc phosphate treatment, the water-washing step after the surface treatment agent contact step can be omitted. This reduces processing time and costs. A topcoat coating may be further formed on the surface of the surface-treated metal member obtained by the above manufacturing method using a topcoat paint. The surface-treated metal member according to this embodiment exhibits favorable adhesion to the topcoat coating. The topcoat paint is not particularly limited and may be a powder paint, a water-based paint, or a solvent-based paint.

[0017] <Metal Member> The metal member to be surface-treated by the method for producing a surface-treated metal member according to this embodiment is not particularly limited, and examples thereof include known metal members. Examples of metal members include iron-based substrates, aluminum-based substrates, zinc-based substrates, and magnesium-based substrates. The term "iron-based substrate" refers to a substrate containing at least one of iron and an iron alloy. Specific examples of iron-based substrates 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 term "aluminum-based substrate" refers to a substrate containing at least one of aluminum and an aluminum alloy. The term "zinc-based substrate" refers to a substrate containing at least one of zinc and a zinc alloy. The magnesium-based substrate means a substrate containing at least one of magnesium and a magnesium alloy.

[0018] In this embodiment, the metal member may be a processed and molded member. According to the method for producing a surface-treated metal member of this embodiment, even if the metal member to be treated is a processed and molded member, the surface-treated metal member produced can have favorable corrosion resistance and can suppress appearance defects. A processed and molded member refers to a metal member that has been processed, for example, by laser processing, press processing, or the like.

[0019] (Degreasing and Water-Rinsing Process) The degreasing and water-rinsing process is a process in which a metal member is degreased and then rinsed with water to form a degreased and water-rinsed metal member. By degreasing the metal member, oil and / or dirt adhering to the surface of the metal member is removed. The method for degreasing the metal member is not particularly limited, and examples include a method of immersion treatment in a degreasing agent such as a phosphorus-free, nitrogen-free degreasing cleaning solution at 30 to 55°C for about several minutes. A preliminary degreasing treatment may be performed before the degreasing method. By rinsing the metal member after degreasing with water, the degreasing agent on the surface of the degreased metal member is removed. The method for water-rinsing is not particularly limited, and examples include a method of spraying a large amount of washing water one or more times.

[0020] (Surface Treatment Agent Contacting Step) The surface treatment agent contacting step is a step in which the degreased and washed metal member obtained in the degreasing and washing step is promptly contacted with an aqueous surface treatment agent to form a metal member having a liquid film on its surface. The time interval between the end of the degreasing and washing step and the start of the surface treatment agent contacting step is preferably 30 seconds or less. The method for contacting the degreased and washed metal member with the aqueous surface treatment agent is not particularly limited, and examples include immersion, spraying, roll coating, and bar coating. Alternatively, the aqueous surface treatment agent may be poured over the degreased and washed metal member to contact it. The conditions for contacting the degreased and washed metal member with the aqueous surface treatment agent are not particularly limited, including both temperature and time. The temperature of the aqueous surface treatment agent during contact can be, for example, 10 to 40°C. The contact time can be set arbitrarily depending on the conditions of the equipment and members to be used, and can be, for example, 10 to 30 seconds. In the surface treatment agent contacting step, if the aqueous surface treatment agent may freeze in a cold environment, the aqueous surface treatment agent may be heated to the minimum extent necessary to prevent freezing, but in a normal environment, the aqueous surface treatment agent does not need to be heated. In the surface treatment agent contacting step, the degreased and water-washed metal member may be brought into contact with the aqueous surface treatment agent once, for example.

[0021] <Water-based surface treatment agent> The water-based surface treatment agent used in the surface treatment agent contact step contains a silicon-containing compound (A) (hereinafter sometimes simply referred to as "silicon-containing compound (A)") that does not contain any polar functional groups other than silanol groups, a water-soluble amino group-containing compound (B), and water. The inclusion of the silicon-containing compound (A) in the water-based surface treatment agent allows the silicon-containing compound (A) to be adsorbed onto the metal substrate, forming a film. Furthermore, the silicon-containing compound (A) functions as a primary binder for the film formed by the water-based surface treatment agent. The inclusion of the water-soluble amino group-containing compound (B) in the water-based surface treatment agent improves adhesion between the film formed by the water-based surface treatment agent and the topcoat coating.

[0022] The silicon-containing compound (A) is a compound that does not contain polar functional groups other than silanol groups, in other words, it is a compound that may contain non-polar functional groups other than silanol groups. Examples of non-polar functional groups include hydrocarbon groups. In this specification and claims, the concept of silanol groups includes silyl groups that can generate silanol groups by hydrolysis in addition to silanol groups. The silicon-containing compound (A) preferably has two silanol groups per molecule. Examples of such silicon-containing compounds (A) include compounds represented by the following formula (I):

[0023]

[0024] In the above formula (I), R １ , R ２ , R ３ , and R ４ each independently represents a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms. Examples of the monovalent organic group include hydrocarbon groups such as alkyl groups, alkenyl groups, cycloalkyl groups, and aryl groups. Preferred monovalent organic groups are alkyl groups having 1 to 4 carbon atoms, such as methyl groups and ethyl groups.

[0025] In the formula (I), Y represents a divalent organic group. Examples of the divalent organic group include an alkylene group and a group containing the divalent organic group as a partial structure. The divalent organic group preferably has 2 to 30 carbon atoms, and more preferably has 2 to 12 carbon atoms.

[0026] In the above formula (I), X １ and X ２ Each of X independently represents a hydrolyzable group. Examples of the hydrolyzable group include a hydroxyl group and an alkoxy group having 1 to 4 carbon atoms. １ and X ２ is preferably a hydroxyl group. １ and X ２ When is an alkoxy group, the alkoxy group is preferably a methoxy group or an ethoxy group.

[0027] In the above formula (I), a and b each independently represent an integer of 0 to 2, and 0≦a+b≦2. Furthermore, c and d each independently represent an integer of 0 to 2, and 0≦c+d≦2. It is preferable that a+b and c+d are both 0 or 1.

[0028] Specific examples of the silicon-containing compound (A) represented by formula (I) above include bis(trimethoxysilyl)methane, 1,2-bis(trimethoxysilyl)ethane, 1,2-bis(triethoxysilyl)ethane, 1,6-bis(trimethoxysilyl)hexane, 1,6-bis(triethoxysilyl)hexane, 1,8-bis(trimethoxysilyl)octane, 1,8-bis(triethoxysilyl)octane, 1,9-bis(trimethoxysilyl)nonane, 1,9-bis(triethoxysilyl)nonane, etc. Among these, 1,2-bis(triethoxysilyl)ethane is preferred from the viewpoints of safety in handling and the corrosion resistance and adhesion of the resulting coating.

[0029] The silicon-containing compound (A) may be, in addition to the compounds represented by the above formula (I), tetraethoxysilane, tetramethoxysilane, trimethoxysilylsilane, or condensates thereof.

[0030] The silicon-containing compound (A) may be used alone or in combination of two or more. The silicon-containing compound (A) may be partially hydrolyzed or condensed by hydrolysis.

[0031] The water-soluble amino group-containing compound (B) is a water-soluble compound having one or more amino groups in the molecule. The water-soluble amino group-containing compound (B) may have a silanol group in addition to the amino group.

[0032] Specific examples of the water-soluble amino group-containing compound (B) include aminosilanes such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, as well as amine-modified epoxy resins, etc. The water-soluble amino group-containing compound (B) may be used alone or in combination of two or more.

[0033] The amine-modified epoxy resin can be obtained by any modification method for modifying an epoxy resin with an amine. Examples of the modification method include a method of adding a primary amino group-containing compound to an epoxy resin, and a method of adding a ketiminated amino group-containing compound to an epoxy resin. Examples of the epoxy resin include bisphenol A epoxy resin and bisphenol F epoxy resin.

[0034] The total mass concentration (A+B) of the silicon-containing compound (A) and the water-soluble amino group-containing compound (B) in the aqueous surface treatment agent is within the range of 1 to 30 g / L. If the total mass concentration (A+B) is less than 1 g / L, the metal substrate will not be sufficiently covered with the film formed, resulting in a decrease in the corrosion resistance of the surface-treated metal member. If the total mass concentration (A+B) exceeds 30 g / L, liquid pools will form, resulting in a thick film at those locations, resulting in poor appearance of the surface-treated metal member. The total mass concentration (A+B) is preferably within the range of 3 to 30 g / L.

[0035] In the aqueous surface treatment agent, the mass concentration ratio of the silicon-containing compound (A) to the total mass concentration (A+B) of the silicon-containing compound (A) and the water-soluble amino group-containing compound (B) {A / (A+B)} is within the range of 45 to 95%. Here, the concentrations used in the calculation of {A / (A+B)} all refer to mass concentrations. If the concentration ratio {A / (A+B)} is less than 45%, the long time interval between the end of the contact step with the surface treatment agent and the start of the drying step will cause liquid runout, resulting in insufficient adsorption of the aqueous surface treatment agent to the metal substrate surface and the failure to form a continuous film. If the concentration ratio {A / (A+B)} is greater than 95%, the content of the water-soluble amino group-containing compound (B) will decrease, resulting in reduced adhesion to the topcoat film.

[0036] The aqueous surface treatment agent according to this embodiment contains water in addition to the silicon-containing compound (A) and the water-soluble amino group-containing compound (B). The water content can be an amount such that the total mass concentration (A + B) falls within a range of 1 to 30 g / L. The aqueous surface treatment agent may contain substances other than those described above, as long as the effects of the present invention are not impaired. For example, the aqueous surface treatment agent may also contain organic solvents, crosslinking agents that promote resin curing, surface conditioners used for leveling purposes, antifoaming agents used for foam suppression, and the like.

[0037] (Drying Process) The drying process is a process for forming a coating by drying the liquid film on the metal member having the liquid film on its surface obtained by the surface treatment agent contacting process. The aqueous surface treatment agent used in the surface treatment agent contacting process is non-reactive, and the formation of the surface treatment film does not involve a chemical conversion reaction, so no sludge is generated. Therefore, unlike conventional chemical conversion treatments, the manufacturing method according to this embodiment does not require a water washing process between the surface treatment agent contacting process and the drying process. This reduces the manufacturing time and manufacturing costs of the surface-treated metal member.

[0038] The drying temperature and drying time in the drying step are not particularly limited as long as they are sufficient to evaporate components not required for the coating (e.g., moisture, organic solvents, etc.). For example, the drying temperature can be 100°C and the drying time can be 10 minutes. The drying method is also not particularly limited, and for example, a commercially available hot air dryer can be used. Prior to the drying step, air blowing or the like may be performed to remove excess aqueous surface treatment agent.

[0039] The time interval between the end of the contact step with the surface treatment agent and the start of the drying step may be 30 seconds or more. The aqueous surface treatment agent according to this embodiment can ensure favorable corrosion resistance and adhesion of the surface-treated metal member even if the time interval is long and dripping or pooling occurs. The time interval may be 5 minutes or more, or 30 minutes or more. It is also preferable that it is less than 180 minutes. Here, during the period from the end of the contact step with the surface treatment agent to the start of the drying step, the surface-treated metal member is transported to the drying furnace without being heated, so the temperature of the surface-treated metal member is maintained at room temperature or below.

[0040] <Surface Treatment Film> The amount of the film formed by the aqueous surface treatment agent after the drying step is 1 to 100 g / m ２ This allows the surface-treated metal member to have favorable corrosion resistance and adhesion.

[0041] The method for producing a surface-treated metal member according to this embodiment may optionally include other processes as long as the effects of the present invention are not impaired. For example, after the drying process, a coating process may be included in which a topcoat coating film is formed using a topcoat coating. The topcoat coating used in the coating process is not particularly limited, and examples thereof include powder coatings such as BI-curing powder coatings and HAA-curing powder coatings, water-based coatings, and solvent-based coatings. The coating method in the coating process is not particularly limited, and known coating methods such as dipping, spraying, roll coating, bar coating, brush coating, and roller coating can be used.

[0042] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0043] [Preparation of Water-Based Surface Treatment Agents] <Examples 1 to 19, Comparative Examples 1 to 8> Water-based surface treatment agents according to each Example and Comparative Example were prepared according to the formulations shown in Table 1 below. The numbers indicating the blending amounts of component (A) and component (B) in Table 1 refer to parts by mass (solid content). In addition to the components shown in Table 1, the water-based surface treatment agents according to each Example and Comparative Example also contain water. Details of the components and materials shown in Table 1 are provided below.

[0044] (A): Silicon-containing compound (A) and its corresponding components A-1: ​​1,2-bis(triethoxysilyl)ethane (BTSE) KBE-3026 (manufactured by Shin-Etsu Chemical Co., Ltd.) A-2: Tetraethoxysilane (TEOS) KBE-04 (manufactured by Shin-Etsu Chemical Co., Ltd.) A-3: Bis(triethoxysilyl)amine Dynasylan 1124 (manufactured by Evonic)

[0045] (B): Water-soluble amino group-containing compound (B) and its corresponding components B-1: 3-aminopropyltrimethoxysilane KBM-903 (Shin-Etsu Chemical Co., Ltd.) B-2: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane KBM-603 (Shin-Etsu Chemical Co., Ltd.) B-3: N-phenyl-3-aminopropyltrimethoxysilane KBM-573 (Shin-Etsu Chemical Co., Ltd.) B-4: Amine-modified epoxy resin B-5: 3-glycidoxypropyltrimethoxysilane KBM-403 (Shin-Etsu Chemical Co., Ltd.)

[0046] (B-4: Method for Producing Amine-Modified Epoxy Resin) A reaction vessel equipped with a stirrer, a cooler, a nitrogen inlet tube, and a thermometer was charged with 702 parts of an epoxy resin with an epoxy equivalent of 188 synthesized from bisphenol A and epichlorohydrin, 269 parts of bisphenol A, 108 parts of dimer acid, and 190 parts of methyl isobutyl ketone (hereinafter referred to as "MIBK"). In the presence of 1 part benzyldimethylamine, the mixture was reacted at 117°C until the epoxy equivalent reached 1270. Subsequently, 255 parts of an aminoethylethanolamine ketimine compound (73% by mass MIBK solution) was added, and the mixture was reacted at 117°C for 1 hour. The mixture was then diluted with MIBK to a nonvolatile content of 75%, yielding an amine-modified epoxy resin with a number average molecular weight of 2400 and an amine equivalent of 1184. Acetic acid was added to the amine-modified epoxy resin to a neutralization rate of 20.0% (neutralization rate relative to the amine groups in the resin), and the mixture was diluted with ion-exchanged water. Thereafter, the mixture of MIBK and water was removed under reduced pressure until the solid content reached 40% by mass, thereby preparing an emulsion of an amine-modified epoxy resin.

[0047] (C): Metal substrate C-1: Cold-rolled steel sheet SPCC-SD (manufactured by Paltec Co., Ltd.) C-2: Hot-dip galvanized steel sheet GI (manufactured by Nippon Test Panel Co., Ltd.) C-3: Alloy hot-dip galvanized steel sheet GA (manufactured by Paltec Co., Ltd.) C-4: Electro-galvanized steel sheet SECC (manufactured by Paltec Co., Ltd.) C-5: Stainless steel sheet SUS316 (manufactured by Standard Test Piece Co., Ltd.)

[0048] (D): Topcoat paint D-1: BI curing powder paint Vilyusia PL1000 (manufactured by Nippon Paint Industrial Coatings Co., Ltd.) D-2: HAA curing powder paint Vilyusia Ecorea PL7000 (manufactured by Nippon Paint Industrial Coatings Co., Ltd.) D-3: One-component water-based paint Ode Ecoline S-130 (manufactured by Nippon Paint Industrial Coatings Co., Ltd.) D-4: Urethane one-component solvent-based paint Unipon 2700 (manufactured by Nippon Paint Industrial Coatings Co., Ltd.)

[0049] [Degreasing and Water-Rinsing Step] Each of the metal substrates (C) shown in Table 1 below was degreased by immersion for 120 seconds in a degreasing agent (trade name "Surf Cleaner 53NF" manufactured by Nippon Paint Surf Chemicals Co., Ltd.) heated to a temperature of 40°C, and then thoroughly rinsed with tap water to obtain a degreased and water-washed metal member.

[0050] [Surface Treatment Agent Contact Step] The aqueous surface treatment agents according to each Example and Comparative Example were sprayed onto the degreased and water-washed metal members described above at room temperature of 25°C for 30 seconds to bring the metal members into contact with the aqueous surface treatment agents, thereby forming a liquid film of the aqueous surface treatment agent on the surface of the metal members.

[0051] In the surface treatment agent contact step, the metal member was brought into contact with the surface treatment agent while in a suspended state. This allows evaluation of dripping on flat surfaces and puddling on edges of processed and molded members after surface treatment. Hanging the metal member can cause dripping on the upper and middle parts of the member after contact with the surface treatment agent. Furthermore, puddles (thick liquid film areas) can form on the edges, which are the lowest part. This allows evaluation of dripping on flat surfaces and puddling on edges of processed and molded members.

[0052] [Drying Step] After the surface treatment agent contact step was completed, the metal substrate was left at room temperature for 30 minutes without heating, and then the drying step was started in which the metal substrate according to each Example and Comparative Example was dried in a dryer at a temperature of 100°C. The drying step was continued for 10 minutes to obtain a metal member having a surface treatment film. The average amount of wet film on each steel plate 30 minutes after treatment was 8 g / m ２ It was.

[0053] [Painting step] The surface-treated metal members according to each of the Examples and Comparative Examples that had undergone the drying step were spray-painted with the topcoat paint (D) shown in Table 1 below, and dried to form a coating film. The surface-treated metal members (test plates) according to each of the Examples and Comparative Examples on which the coating film had been formed were evaluated as follows.

[0054] <Corrosion Resistance (SST) Test> A salt spray test (SST) was performed on the test plate for 500 hours under the conditions of JIS Z 2371:2015. Cellophane tape was then applied to the cross-cut area, and the cellophane tape was peeled off to check for peeling from the cross-cut area. Evaluation was then performed according to the following criteria. The results are shown in Table 1. 3: No peeling occurred after 500 hours. 2: No peeling occurred after 250 hours, but peeling occurred after 500 hours. 1: Peeling occurred after 250 hours.

[0055] <Evaluation of Appearance of Coating> The appearance of the surface-treated metal members according to each of the Examples and Comparative Examples after the painting process was visually evaluated according to the following evaluation criteria. The results are shown in Table 1. 2: No abnormalities 1: Poor appearance

[0056]

[0057] As shown in Table 1, it was confirmed that the surface-treated metal members according to each Example had better corrosion resistance and coating appearance than the surface-treated metal members according to each Comparative Example.

Claims

1. A method for producing a surface-treated metal member, comprising: a degreasing and washing step of degreasing a metal member and then washing it with water to form a degreased and water-washed metal member; a surface treatment agent contact step of contacting the degreased and water-washed metal member with an aqueous surface treatment agent to form a metal member having a liquid film on its surface; and a drying step of drying the liquid film on the metal member having the liquid film on its surface to form a coating, wherein the aqueous surface treatment agent comprises a silicon-containing compound (A) that does not contain a polar functional group other than a silanol group, a water-soluble amino group-containing compound (B), and water, and the total mass concentration of the silicon-containing compound (A) and the water-soluble amino group-containing compound (B) in the aqueous surface treatment agent, i.e., (A+B), is within the range of 1 to 30 g / L, a mass concentration ratio of the silicon-containing compound (A) to a total mass concentration (A+B) of the silicon-containing compound (A) and the water-soluble amino group-containing compound (B), {A / (A+B)}, in the aqueous surface treatment agent, is within a range of 45 to 95%.

2. The method for producing a surface-treated metal part according to claim 1, wherein the metal part is a processed and molded part.

3. The method for producing a surface-treated metal member according to claim 1, wherein the silicon-containing compound (A) is a silicon-containing compound having two or more silanol groups in one molecule.

4. The method for producing a surface-treated metal member according to claim 1, wherein the silicon-containing compound (A) is 1,2-bis(triethoxysilyl)ethane.

5. The method for producing a surface-treated metal member according to claim 1, wherein the water-soluble amino group-containing compound (B) is an aminosilane or an amine-modified epoxy resin.

6. The method for producing a surface-treated metal product according to claim 1, wherein the time interval between the end of the surface treatment agent contact step and the start of the drying step is 30 seconds or more.

7. The amount of the film formed by the aqueous surface treatment agent after drying is 1 to 100 mg / m ２ The method for producing a surface-treated metal member according to claim 1 , wherein the surface-treated metal member has a thickness of 100 nm or less and a thickness of 100 nm or less.

Images