Surface treatment method for metal substrate and surface treatment device

Abstract

To provide a surface treatment method for a metal substrate having high production efficiency.SOLUTION: The inventive surface treatment method for a metal substrate includes following steps in this order: a pretreatment step for applying a pretreatment liquid to the surface of a metal substrate, a plating step for applying a plating liquid to the surface of the metal substrate, a silica coat forming step for applying an aqueous antirust surface-treatment liquid containing a silane compound and water to the surface of the metal substrate, forming a silica coat thereon, and a baking step for baking the metal substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surface treatment method for a metal substrate and a surface treatment device. [Background technology]

[0002] Various surface treatment methods for metal substrates have been developed to date. One such technique is described in Patent Document 1. Patent Document 1 describes a post-treatment system that performs zinc plating, baking, and hexavalent chromium film treatment (chromate treatment) in this order (e.g., claim 1 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-3270 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of studies by the present inventors, it has become clear that there is room for improvement in terms of production efficiency in the post-processing system described in Patent Document 1 above. [Means for solving the problem]

[0005] In a typical plating system such as that described in Patent Document 1, pretreatment, plating, baking, and chromate treatment (post-treatment) are performed in that order. By performing baking immediately after plating, hydrogen molecules generated in the substrate by plating can be expelled from the substrate by baking, thereby preventing hydrogen embrittlement in the metal substrate. Such conventional baking treatments had to be carried out before chromate treatment. The reasons for this include the fact that if baking treatment is carried out after chromate treatment, it is difficult to expel hydrogen molecules generated in the base material to the outside of the base material, and there is a risk of cracks occurring in the chromate film due to heating during baking treatment. It is known that cracks occur in chromate films at around 70°C due to shrinkage caused by dehydration. However, when the baking treatment is performed before the chromate treatment, a step of cooling the heated metal base material, a waiting time for cooling, and space for temporarily storing the metal base material during cooling are required, which may reduce the manufacturing efficiency of the entire surface treatment process.

[0006] The inventors further studied and found that by carrying out the plating step, the silica film forming step, and the baking step in this order, the cooling step after the baking process is unnecessary, and the cooling waiting time can be reduced, thereby shortening the lead time. In addition, the acid activation treatment before the chromate treatment and the activation treatment of the zinc film including the chromate, which were carried out in the plating system, are also unnecessary. Furthermore, by using a silica film, cracking of the film due to heating during the baking process can be suppressed compared to the above-mentioned chromate film, and hydrogen molecules in the base material can be more easily released to the outside. Although the detailed mechanism is unclear, it is believed that because the silica coating contains silica, a heat-resistant material, it can suppress film cracking. In addition, because the silica coating is formed with a lower density than a chromate coating, it can easily remove hydrogen molecules generated in the base material. As described above, the inventors have found that the manufacturing efficiency of the entire surface treatment process can be improved by performing the plating step, the silica film forming step, and the baking step in this order, and have completed the present invention.

[0007] According to the present invention, A pretreatment step of applying a pretreatment liquid to the surface of the metal substrate; a plating step of applying a plating solution onto the surface of the metal base material; a silica film forming step of applying an aqueous rust-preventive surface treatment liquid containing a silane compound and water to the surface of the metal substrate to form a silica film; and a baking step of baking the metal substrate; In accordance with the present invention, there is provided a method for treating the surface of a metal substrate, comprising the steps of:

[0008] Further, according to the present invention, a pretreatment section for applying a pretreatment liquid onto the surface of the metal substrate; a plating processing section for applying a plating solution onto a surface of the metal base material; a silica film forming section for applying an aqueous rust-preventive surface treatment liquid containing a silane compound and water onto the surface of the metal substrate to form a silica film; and A baking unit for baking the metal base material; The above-mentioned steps are connected in a line in this order to provide a surface treatment apparatus. Effect of the Invention

[0009] According to the present invention, there are provided a surface treatment method for a metal substrate, which has excellent production efficiency, and a surface treatment device for carrying out the method. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing an example of a process flow in the surface treatment method of the present embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of a surface treatment apparatus according to the present embodiment. [Diagram 3] FIG. 1 is a diagram showing an embodiment of the configuration of a surface treatment device. [Figure 4] FIG. 1 is a diagram showing a reference example of the configuration of a surface treatment device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The surface treatment method and surface treatment device for a metal substrate according to this embodiment will be outlined below.

[0012] The surface treatment method for a metal substrate in this embodiment includes, in this order, a pretreatment step of applying a pretreatment liquid onto the surface of the metal substrate, a plating step of applying a plating liquid onto the surface of the metal substrate, a silica film formation step of applying an aqueous rust-preventive surface treatment liquid containing a silane compound and water onto the surface of the metal substrate as one of the post-treatment steps to form a silica film, and a baking step of baking the metal substrate.

[0013] The above surface treatment method is configured to perform the baking process after the post-treatment process (silica film formation process) rather than before the post-treatment process. Therefore, by performing the plating process, silica film formation process, and baking process in this order, the cooling process after the baking process is unnecessary, and the cooling wait time can be reduced, shortening the lead time. In addition, activation and water rinsing of the zinc film after the baking process, which were conventionally performed before the chromate treatment, are also unnecessary. In this way, by adopting a silica film formation process instead of the conventional chromate treatment for the post-treatment and carrying out a baking process after this silica film formation process, it is possible to eliminate multiple processes such as cooling and activation that were necessary in the conventional chromate treatment, thereby reducing the lead time of the entire process, thereby realizing a surface treatment method for metal substrates with excellent manufacturing efficiency.

[0014] The surface treatment device of this embodiment also includes a pretreatment section, a plating section, a posttreatment section (silica film forming section), and a baking section as means for carrying out each step in the above-mentioned method for treating the surface of a metal substrate.

[0015] The above surface treatment equipment can reduce equipment costs and save space compared to the case where the steps are pre-treatment, plating, baking, and post-treatment (e.g., chromate treatment) in that order. A simple calculation shows that the equipment costs can be reduced by about 15 to 25% and the equipment area by about 25 to 35%.

[0016] The above surface treatment device eliminates the need for equipment and space required for processes that can be reduced by the above surface treatment method. For example, it eliminates the need for space to store the metal substrate heated by the baking treatment until it is cooled before being transported to the next process, it eliminates the need for heat insulating equipment and space between the baking device and other devices adjacent to it, and it eliminates the need for an acid activation tank or water washing tank before the chromate treatment after the baking treatment, or a dehydrator after the chromate treatment. In this way, in the above-mentioned surface treatment apparatus, the overall apparatus configuration can be reduced and space can be saved, so that a significant cost reduction can be achieved.

[0017] At least a part or all of the chemicals used in the surface treatment method can be substantially free of chromium components. Specifically, the pretreatment liquid, plating liquid, and aqueous anticorrosive surface treatment liquid may be configured to substantially not contain chromium components, or the pretreatment liquid, plating liquid, chemical conversion treatment liquid, and aqueous anticorrosive surface treatment liquid may be configured to substantially not contain chromium components. This makes it possible to realize a chromium-free surface treatment method and surface treatment device for metal substrates. In addition, the waste liquid generated by these surface treatment methods and surface treatment devices does not contain chromium, so that the environmental load during waste liquid treatment can be reduced.

[0018] In the surface treatment method of this embodiment, it is possible to continuously treat all the steps including the pretreatment step, plating step, silica film formation step, and baking step, and in the case of a chemical conversion treatment step, all the steps including the chemical conversion treatment step, online. That is, the process can be continuously performed from after the pretreatment step to before the post-treatment step, specifically before the silica film formation step, without going through a drying treatment. In the surface treatment device, it is not necessary to install a dehydrator between after the pretreatment unit and before the post-treatment unit. In this case, the chemical liquid used in each step or each unit is appropriately selected from those that can be transferred to the next process without drying (dehydration). For example, an aqueous chemical liquid can be preferably used.

[0019] Hereinafter, each step in the method for treating the surface of a metal substrate according to the present embodiment will be described in detail.

[0020] The surface treatment method includes a pretreatment step, a plating step, a post-treatment step, and a baking step, in this order, as shown in FIG.

[0021] The pretreatment step is not particularly limited as long as it includes a pretreatment before plating, and it is a step of applying a pretreatment liquid onto the surface of the metal base material, thereby cleaning the surface of the metal base material.

[0022] The pretreatment may involve, for example, one or more of immersion methods such as liquid circulation cleaning, ultrasonic cleaning, barrel cleaning, and electric field cleaning; spray (atomizing) methods such as spray cleaning; and the like.

[0023] An appropriate pretreatment liquid is used according to the above cleaning method. Examples of the pretreatment liquid include degreasing agents such as caustic soda, silicates, carbonates, phosphates, chelating agents, surfactants, and antifoaming agents; acidic liquids such as hydrochloric acid and sulfuric acid; and solvents such as sorbent naphtha, benzene, trichloroethylene, and 1,1,1-trichloroethane. The acidic liquid may contain a corrosion inhibitor, an acid pickling promoter, and the like, as necessary.

[0024] After washing in the pretreatment step or between two or more washes, steps such as washing with water and neutralization may be carried out. As an example of the pretreatment process, for example, alkaline degreasing → water washing → acid washing → water washing may be adopted, and in addition to this, electrolytic degreasing → water washing → neutralization → water washing or electrolytic degreasing → water washing, etc. may be further carried out.

[0025] In the pretreatment process, the chemical cleaning method using the pretreatment liquid can improve the cleaning stability compared to physical cleaning methods such as blast cleaning. In addition, it is easy to scale up.

[0026] As the pretreatment liquid, for example, a phosphate-based pretreatment liquid or an alkaline pretreatment liquid may be used as an aqueous chemical liquid obtained by dissolving a phosphate surface conditioner "ZEC-PZ3" or an alkaline degreaser "ZEC-ZC4" manufactured by Electric Discharge Precision Processing Laboratory Co., Ltd. in water.

[0027] In this specification, examples of a method for applying a chemical solution such as a pretreatment solution, a plating solution, a chemical conversion treatment solution, or an aqueous anticorrosive surface treatment solution to a metal substrate include an immersion method in which the treatment is performed in a state where the substrate is immersed in a liquid chemical solution, and a spray method in which the treatment is performed in a state where the substrate is in contact with a mist of the chemical solution.

[0028] The pretreatment liquid, plating liquid, chemical conversion treatment liquid, and aqueous anticorrosive surface treatment liquid may be applied to the metal substrate using the same or different methods. In one preferred embodiment, at least the plating liquid may be applied using the immersion method, the pretreatment liquid and the plating liquid may be applied using the immersion method, or all of the chemical liquids may be applied using the immersion method.

[0029] The metal substrate is not particularly limited, and may include, for example, one or more selected from the group consisting of an iron-based substrate, an aluminum-based substrate, a magnesium-based substrate, a nickel-based substrate, and a cobalt-based substrate. These substrates each contain iron, aluminum, magnesium, nickel, or cobalt as a main component. Each substrate may contain one or more metal elements or nonmetal elements other than the main component as a secondary component.

[0030] As materials constituting the iron-based substrate, various steel materials and iron-based alloys can be used, and examples thereof include carbon steel, alloy steel, nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, manganese steel, tool steel, stainless steel, heat-resistant steel, nitriding steel, and case-hardened steel.

[0031] The metal substrate is not particularly limited, but metal parts such as bolts, nuts, screws such as tapping screws and screws, and pre-processed materials such as metal plates can be used.

[0032] In the plating step, a plating solution is applied to the surface of the pretreated metal base material to form a plating film. In one specific example of the plating process, a metal substrate is immersed in a plating solution to form a plating film on the surface of the metal substrate. The plating film is formed on a part or the entire surface of the metal substrate.

[0033] The method for forming the plating film is not particularly limited, but examples thereof include electroplating, electroless plating, and hot-dip plating. Examples of electroplating include zinc plating, nickel plating, tin plating, zinc-nickel plating, and nickel-chrome plating. An example of the electroless plating is electroless nickel plating. An example of the hot-dip plating is hot-dip galvanizing.

[0034] The plating solution may be any solution containing a plating metal component such as a metal salt or molten metal, and may contain, for example, one or more metal elements selected from the group consisting of zinc, nickel, and tin. The plating solution may have a known composition depending on the type of plating.

[0035] In the post-treatment step, a post-treatment is carried out on the surface of the metal base material on which the plating film has been formed, to form an anti-rust film. The post-treatment step includes at least a silica film forming step, and preferably includes a step of carrying out a chemical conversion treatment step and a silica film forming step in this order.

[0036] In the chemical conversion treatment step, a chemical conversion treatment liquid is applied after the plating step and before the silica film forming step, to form a chemical conversion film on the plating film on the surface of the metal base material.

[0037] As the chemical conversion treatment, a known treatment method can be used, and examples thereof include phosphate treatments containing zinc, manganese, iron, calcium, etc.; zirconium-based treatments containing zirconium, titanium, hafnium, etc.; chemical conversion treatments containing cerium, vanadium, tungsten, etc.; and the like.

[0038] Among these, from the viewpoint of reducing the environmental load, non-chromium-based chemical conversion coatings such as phosphate treatment and zirconium-based treatment can be used.

[0039] In the case of phosphating, a phosphate-based chemical conversion treatment solution containing, for example, a phosphate having at least one of zinc, manganese, iron, and calcium, preferably zinc phosphate, may be used as the chemical conversion treatment solution. By using a chemical conversion treatment solution containing zinc phosphate, a zinc phosphate film can be obtained as the chemical conversion film.

[0040] In the case of zirconium-based treatment, a zirconium-based chemical conversion treatment liquid containing at least one of zirconium, titanium, and hafnium, preferably containing zirconium, may be used as the chemical conversion treatment liquid. By using the chemical conversion treatment liquid containing zirconium, a zirconium coating can be obtained as the chemical conversion coating.

[0041] As the chemical conversion treatment liquid, for example, an aqueous chemical solution containing water as a solvent may be used, such as "ZEC-PZ" containing zinc phosphate, "ZEC-PM" containing manganese phosphate, or "ZEC-ZC" containing zirconium, all manufactured by Electric Discharge Precision Machining Laboratory.

[0042] In the silica film forming step, an aqueous rust-preventive surface treatment liquid is applied to the surface of the metal base material on which a plating film or a chemical conversion film has been formed, to form a silica film.

[0043] Here, each component of the aqueous rust-preventive surface treatment solution will be described in detail.

[0044] The aqueous anticorrosive surface treatment liquid contains at least a silane compound and water. A silica film can be formed by drying the aqueous rust-preventive surface treatment liquid. The drying treatment may be performed at room temperature of 20 to 25°C, but may also be performed by heating to an appropriate temperature, for example, 60 to 100°C. The silica coating has the property of having low gas barrier properties against hydrogen gas, and therefore can suppress the hindrance of expelling hydrogen molecules generated in the metal base material to the outside during the baking step.

[0045] The aqueous rust-preventive surface treatment liquid preferably contains a water-dispersible resin. Water-dispersible resins are unlikely to be dissolved by H groups or OH groups that do not completely react during film formation and remain in the film, or by moisture, and are therefore thought to be able to improve the corrosion resistance and heat resistance of the silicon film. Among the water-dispersible resins, it is preferable to use a water-dispersible silicone resin from the viewpoint of heat resistance.

[0046] It is preferable to use a heat-resistant silica film as the silica film, as described above, which can prevent the silica film from cracking even when the film is subjected to a heat treatment under high temperature conditions in the subsequent baking step.

[0047] In this specification, the heat-resistant silica film can be defined as a film that does not develop cracks or other breaks in the film when heated at 200° C. for 4 hours.

[0048] The aqueous rust-preventive surface treatment liquid may contain one or more members selected from the group consisting of inorganic colloid particles, a silane coupling agent, and an organometallic compound.

[0049] <Silane compounds> The silane compound includes one or more members selected from the group consisting of a silane coupling agent and an alkoxysilane.

[0050] As the silane coupling agent, a silane compound having a hydrolyzable group such as an alkoxy group and a reactive functional group bonded to a silicon atom is used. As the silane coupling agent, either one or both of a monomer and an oligomer may be used. The use of a silane coupling agent can stabilize the aqueous solution. It is believed that the silane coupling agent can improve the affinity between components such as aqueous colloidal silica, thereby forming a stable aqueous solution (composition).

[0051] The silane coupling agent is, for example, a compound represented by the general formula: (R 1 ) m Si(OR 2 ) 4―m (In the above general formula, R 1 is a functional group having 1 to 20 carbon atoms, R 2 is a lower alkyl group. m is an integer of 0 to 3.) or a compound obtained by hydrolyzing and condensing the same is used. The silane coupling agent may be partially hydrolyzed in the composition.

[0052] Specific examples of silane coupling agents represented by the above general formula include Si(OCH3)4, Si(OC2H5)4, CH3Si(OCH3)3, CH3Si(OC2H5)3, C2H5Si(OCH3)3, C2H5Si(OC2H5)3, CH2(O)CHCHO(CH2)3Si(OCH3)3, CH2=C(CH3)COO(CH2)3Si(OCH3)3, CH2=CHCOO(CH2)3Si(OCH3)3, H2N(CH2)3Si(OCH3)3, HS(CH2)3Si(OCH3)3, OCN(CH2)3Si(OC2H5)3, etc.

[0053] In addition, in the above chemical formula, R 1 Examples of functional groups therein include vinyl, 3-glycidoxypropyl, 3-glycidoxypropylmethyl, 2-(3,4-epoxycyclohexyl)ethyl, p-styryl, 3-methacryloxypropyl, 3-methacryloxypropylmethyl, 3-acryloxypropyl, 3-aminopropyl, N-2-(aminoethyl)-3-aminopropyl, N-2-(aminoethyl)-3-aminopropylmethyl, N-phenyl-3-aminopropyl, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl, 3-ureidopropyl, 3-mercaptopropyl, and 3-isocyanatopropyl groups.

[0054] In the above chemical formula, specific examples of the lower alkyl group include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1-ethylpropyl, isopentyl, and neopentyl.

[0055] The silane coupling agent is preferably a water-soluble silane coupling agent that can be dissolved in water. The water-soluble silane coupling agent may include, for example, a silane coupling agent having an epoxy group as a functional group (epoxysilane) or a silane coupling agent having an amino group as a functional group (aminosilane). Among these, it is more preferable to use epoxysilane from the viewpoint of corrosion resistance.

[0056] Examples of the epoxy silane include glycidyl or epoxy group-containing trialkoxysilane compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexylethyl)trimethoxysilane.

[0057] As the alkoxysilane, a silane compound in which an alkoxy group is bonded to a silicon atom and a non-reactive functional group such as a hydrogen group or an alkyl group is bonded, for example, an alkylalkoxysilane can be used. As the alkoxysilane, either one or both of a monomer and an oligomer may be used. As the alkylalkoxysilane monomer, for example, at least one selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane can be used.

[0058] The content of the silane coupling agent and / or alkoxysilane in the aqueous rust-preventive surface treatment liquid is, for example, 0.1% by mass to 12% by mass, preferably 1% by mass to 11% by mass, and more preferably 1.5% by mass to 10% by mass, calculated as solid content.

[0059] In this specification, the symbol "to" indicates that the upper and lower limits are included, unless otherwise specified. The solid content refers to the remainder after removing volatile components such as water, alcohol solvent, etc. This solid content may be the residue remaining after the reaction of each component after the aqueous rust-preventive surface treatment liquid is heat-treated.

[0060] <Water dispersible resin> The aqueous rust-preventive surface treatment liquid may contain a water-dispersible resin. The water-dispersible resin is composed of a resin that disperses in water.

[0061] The resin constituting the water-dispersible resin may be appropriately selected from resins that can be dispersed in water, and may be, for example, polyacrylic acid resin, silicone resin, phenol resin, epoxy resin, polyurethane resin, polyester resin, polyvinyl butyral resin, phenol resin, or modified products thereof. These may be used alone or in combination of two or more. Among these, from the viewpoint of corrosion resistance and durability of the film, polyacrylic resin, epoxy resin, polyurethane resin, silicone resin, etc. may be used as the water-dispersible resin.

[0062] The content of the water-dispersible resin in the aqueous rust-preventive surface treatment liquid is, for example, 1% by mass to 12% by mass, preferably 1.5% by mass to 11% by mass, and more preferably 2% by mass to 10% by mass, calculated as solid content. By making the content equal to or greater than the lower limit, the heat resistance and corrosion resistance of the coating can be improved. By making the content equal to or less than the upper limit, the physical properties of the coating can be well-balanced. The content of the water-dispersible resin is, in terms of solid content, for example, 5 to 300 parts by mass, preferably 10 to 250 parts by mass, and more preferably 20 to 200 parts by mass, relative to 100 parts by mass of the silane coupling agent.

[0063] <Organometallic compounds> The organometallic compound includes one or more compounds selected from the group consisting of organotitanium compounds, organozirconium compounds, and organoaluminum compounds.

[0064] Examples of organic titanium compounds include titanium chelates, titanium alkoxides, and titanium acylates. Examples of organic zirconium compounds include zirconium chelates, zirconium alkoxides, and zirconium acylates. Examples of organic aluminum compounds include aluminum chelates and aluminum alkoxides. These compounds may be used alone or in combination of two or more. The organometallic compound may be a monomer or an oligomer, or both of them may be used.

[0065] Among these, an organic titanium compound and / or an organic zirconium compound may be used as the water-soluble transition metal compound.

[0066] The titanium chelate may be, for example, an organic compound represented by the general formula Ti(X)4 or an oligomer thereof. In the general formula, X is selected from a hydroxyl group, a lower alkoxy group, and a chelating substituent, and the four Xs may be the same or different.

[0067] The content of the organometallic compound is, for example, 0.01 to 7 mass %, preferably 0.015 to 5 mass %, and more preferably 0.02 to 3 mass %, calculated as solid content in the entire aqueous rust-preventive surface treatment liquid. The content of the organometallic compound is, in terms of solid content, for example, 0.1 to 50 parts by mass, preferably 0.5 to 150 parts by mass, and more preferably 1 to 20 parts by mass, relative to 100 parts by mass of the silane coupling agent.

[0068] Here, the aqueous rust-preventive surface treatment liquid may be configured to contain at least one of titanium dioxide powder and flaky metallic zinc powder, preferably neither of them. By not containing titanium dioxide powder or flaky metallic zinc powder, the long-term film stability of the aqueous rust-preventive surface treatment liquid can be improved and film cracking of the silica film over time can be suppressed.

[0069] <Inorganic colloid particles> The aqueous anticorrosive surface treatment liquid may contain inorganic colloidal particles such as aqueous colloidal silica.

[0070] The water-soluble colloidal silica is dispersed in a water solvent or a mixed solvent containing water, and contains inorganic particles made of SiO2. The average particle size of the inorganic particles may be, for example, 1 to 200 nm.

[0071] The aqueous anticorrosive surface treatment liquid may contain inorganic colloidal particles composed of inorganic oxides other than aqueous colloidal silica, such as Al2O3, ZrO2, Fe2O3, etc. The inorganic colloidal particles are composed of inorganic particles dispersed in water.

[0072] By using aqueous colloidal silica, the strength of the film obtained from the aqueous antirust surface treatment liquid can be further improved. Also, since the dispersibility in the composition can be increased, a silicon film in which silica particles are uniformly dispersed in the film can be formed.

[0073] The content of the inorganic colloidal particles or aqueous colloidal silica in the aqueous rust-preventive surface treatment liquid is, for example, 0.5% by mass to 12% by mass, preferably 0.6% by mass to 10% by mass, and more preferably 0.8% by mass to 8% by mass, calculated as solid content. By making it equal to or more than the lower limit, it is possible to impart an appropriate strength to the film. By making it equal to or less than the upper limit, it is possible to balance the physical properties of the film.

[0074] The content of the inorganic colloidal particles or aqueous colloidal silica is, in terms of solid content, for example, 10 parts by mass to 300 parts by mass, preferably 15 parts by mass to 200 parts by mass, and more preferably 20 parts by mass to 150 parts by mass, relative to 100 parts by mass of the silane coupling agent.

[0075] <Solvent> The aqueous rust-preventive surface treatment liquid includes a solvent containing water. This solvent may be composed of an aqueous solvent containing only water, or may be composed of an aqueous mixed solvent containing water and a hydrophilic solvent other than water.

[0076] Examples of the water include city water, distilled water, and ion-exchanged water.

[0077] The hydrophilic solvent may be a polar organic solvent such as alcohol. From the viewpoint of solution stability, the aqueous mixed solvent may be composed of a mixed solvent of water and alcohol. The content ratio of water in the aqueous mixed solvent can be determined in consideration of the chemical properties and blending amounts of each component in the aqueous rust-preventive surface treatment liquid. By using an alcohol, the solubility of each component can be improved, and the storage stability of the resulting aqueous rust-preventive surface treatment liquid can be improved.

[0078] Examples of the alcohol that can be used include low-boiling alcohols having a boiling point of less than 100° C., such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol, and high-boiling alcohols having a boiling point of 100° C. or higher, such as iso-butanol, methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether (PGME), butyl cellosolve, ethylene glycol monotertiary butyl ether (ETB), and diformaldehyde methoxyethanol. These may be used alone or in combination of two or more.

[0079] The content of the alcohol in the aqueous rust-preventive surface treatment liquid is, for example, 0.1% by mass to 20% by mass, preferably 0.2% by mass to 12% by mass, and more preferably 0.3% by mass to 10% by mass. By keeping it within the above range, the long-term storage stability of the composition can be improved. Also, by keeping it below the above upper limit, the adhesion can be improved.

[0080] The content of the alcohol is, for example, 0.1% by mass to 20% by mass, preferably 0.2% by mass to 15% by mass, and more preferably 0.3% by mass to 14% by mass, based on 100% by mass of the total content of the water and the alcohol. By keeping the content within such a numerical range, the long-term storage stability of the aqueous rust-preventive surface treatment liquid can be improved.

[0081] The content of the alcohol is, for example, 1 part by mass to 300 parts by mass, preferably 2 parts by mass to 200 parts by mass, more preferably 3 parts by mass to 170 parts by mass, relative to 100 parts by mass of the total content of the silane coupling agent and the water-dispersible resin. By making it equal to or more than the lower limit, a composition in which the silane coupling agent is stably dissolved can be realized. By making it equal to or less than the upper limit, the dispersibility of the water-dispersible resin can be increased. By making it within the above range, the long-term storage stability of the composition can be increased.

[0082] (Other ingredients) The aqueous rust-preventive surface treatment liquid may contain other additives in addition to the above components. As other additives, various additives usually contained in primer materials can be used, such as rust inhibitors, pH adjusters, lubricants, preservatives, fillers, colorants, surfactants, defoamers, leveling agents, and antibacterial agents. These may be used alone or in combination of two or more. The amount of additives added can be appropriately set depending on the application.

[0083] As the rust inhibitor, for example, a phosphoric acid-based rust inhibitor is used. The phosphoric acid-based rust inhibitor may contain a highly condensed phosphate or a polyvalent phosphoric acid ester. The aqueous rust-preventive surface treatment liquid may contain either a highly condensed phosphate or a polyvalent phosphate ester, or may contain both.

[0084] The aqueous rust-preventive surface treatment liquid may contain a highly condensed phosphate. The high condensation phosphate is a salt of a high condensate formed by dehydration condensation of four or more phosphoric acids. By using the high condensation phosphate, the corrosion resistance of the film made of the composition can be improved compared to the case where orthophosphoric acid, pyrophosphoric acid, triphosphoric acid, or salts thereof are used.

[0085] The degree of condensation of phosphoric acid in the highly condensed phosphate (the number of structural units derived from phosphoric acid in a molecule) is, for example, 4 or more, preferably 5 or more, and more preferably 6 or more. This can improve corrosion resistance. On the other hand, the upper limit of the degree of condensation is not particularly limited, but may be, for example, 50 or less, 40 or less, or 30 or less.

[0086] The polyvalent phosphate ester is a compound having a plurality of phosphate ester residues. The phosphate ester residues have a monophosphate structure or a diphosphate structure. The alcohol moiety forming the phosphate ester residue may be any of a primary alcohol, a secondary alcohol, and a tertiary alcohol. A specific example of the polyvalent phosphate ester is phytic acid.

[0087] Examples of the preservative include isothiazoline compounds.

[0088] As an example of the aqueous rust-preventive surface treatment liquid (aqueous rust-preventive treatment agent), all components contained in the composition may be composed of water-soluble components or water-dispersible components. That is, the aqueous rust-preventive surface treatment liquid may be composed of an aqueous solution containing only water-soluble components or water-dispersible components.

[0089] The aqueous rust-preventive surface treatment liquid may be a chromium-free rust-preventive treatment agent that is substantially free of chromium components such as hexavalent chromium and trivalent chromium.

[0090] In this specification, "substantially free of chromium components" refers to the amount of hexavalent chromium and trivalent chromium being 0.1 mass% or less. The amounts of hexavalent chromium and trivalent chromium refer to the content of chromium salts having these specific valences.

[0091] As the aqueous anti-rust surface treatment liquid, for example, the "ZEC-W" series manufactured by Electric Discharge Precision Processing Laboratory Co., Ltd. may be used.

[0092] The method for producing the aqueous rust-preventive surface treatment liquid is not particularly limited, but the liquid can be obtained by mixing the following components. The order in which the components are mixed is not limited, and the components can be mixed in any order.

[0093] The lower limit of the thickness (dry film thickness) of the silicon film is, for example, 0.3 μm or more, preferably 0.5 μm or more, and more preferably 1.0 μm or more, which allows the corrosion resistance effect to be fully exerted. On the other hand, the upper limit of the thickness of the silicon film is not particularly limited, but may be, for example, 100 μm or less, 50 μm or less, or 30 μm or less.

[0094] In the silicon film, each component contained in the aqueous anti-rust surface treatment solution undergoes various crosslinking reactions, spatial arrangements, and / or dispersions, as described below. In the silicon film, the solvent including water is removed by drying, but it is acceptable that some of it remains.

[0095] Although the detailed mechanism is unclear, the structure of the silicon film is presumed to be as follows. Silane coupling agents and / or silane compounds such as alkoxysilanes can form silicon coatings having two-dimensional and / or three-dimensional crosslinked structures through crosslinking reactions such as hydrolysis condensation of silyl groups contained in the molecules. A coating having a crosslinked structure is formed by a dehydration condensation reaction between a hydrolysis condensate of a silane compound and an organometallic compound. For example, a crosslinked structure is formed in the coating between a silicon atom derived from the silane compound and a transition metal atom derived from the organometallic compound via an oxygen atom. In addition, the organometallic compound promotes chemical bonding with the silane compound or other components contained therein, and can form a coating with high strength. In addition, silicon atoms derived from the silane compound and metal atoms from the organometallic compound chemically bond to the zinc-rich coating film, which is the base film, via oxygen atoms, and the silicon film physically bonds to the base film, thereby improving adhesion between the silicon film and the zinc-rich coating film. In addition, inorganic particles such as silica having an appropriate particle size are appropriately arranged in the void spaces in the film, so that a highly dense silicon film can be obtained. The surfaces of the inorganic particles such as silica can form chemical bonds with the silicon atoms of the silane compound in the crosslinked structure via oxygen atoms.

[0096] The baking step is not particularly limited as long as it heats the metal base material and performs a dehydrogenation treatment. The lower limit of the temperature of the heat treatment in the baking step is, for example, 150°C or more, preferably 180°C or more, and more preferably 190°C or more. This provides a dehydrogenation effect. The upper limit of the temperature of the heat treatment is, for example, 300°C or less, preferably 250°C or less, and more preferably 220°C or less. This can suppress deterioration of the metal substrate and the film formed on the surface thereof.

[0097] The time for the heat treatment in the baking step is, for example, 1 hour to 24 hours, preferably 2 hours to 10 hours, and more preferably 3 hours to 6 hours. By setting the time within the above numerical range, it is possible to achieve a balance between the dehydrogenation effect and the production efficiency.

[0098] By going through the above steps, a surface-coated metal substrate is obtained. This surface-coated metal substrate has excellent corrosion resistance.

[0099] An example of a surface-coated metal substrate has a structure in which a metal substrate, a plating film, and a silica coating are laminated in this order, or a structure in which a metal member, a plating film, a chemical conversion coating, and a silica coating are laminated in this order.

[0100] A preferred embodiment of the aqueous antirust surface treatment liquid contains 5-9% by mass of epoxy silane as a silane compound, 2-9% by mass of polyacrylic acid resin or silicone resin as a water-dispersible resin, 1-7% by mass of titanium chelating agent as an organometallic compound, 2-9% by mass of aqueous colloidal silica as inorganic colloidal particles, 1-10% by mass of alcohol as a solvent, and the remainder being water. This aqueous antirust surface treatment liquid may contain 0.2-1% by mass of a highly condensed phosphate or polyphosphate ester as a phosphorus-based antirust agent, and 0.01-0.2% by mass of an isothiazolinone-based compound as a preservative, if necessary. The above contents represent the amounts of the following components used. (Silane compounds) Epoxy silane 1: 3-glycidoxypropyltriethoxysilane (Asahi Kasei Wacker Silicone Co., Ltd., GF-82, solid content: 67% by mass) (Water dispersible resin) Polyacrylic acid resin 1: Water-dispersible acrylic resin (Stahl Polymers, solid content: 60% by weight) Silicone resin 1: Water-dispersible silicone resin (manufactured by Wacker Asahi Kasei Silicone Co., Ltd., solid content: 60% by mass) (organometallic compound) Titanium chelating agent 1: Titanium lactate ammonium salt (manufactured by Matsumoto Fine Chemical Co., Ltd., TC-300, solid content: 20% by mass) (Inorganic colloid particles) Aqueous colloidal silica 1: (Nissan Chemical Industries, Snowtex ST-O, acidic sol, particle size: 20 nm, solid content: 40% by mass) (Phosphorus-based rust inhibitor) Highly condensed phosphate 1: Ultra sodium phosphate (Kanto Chemical Co., Ltd., a network structure in which linear and cyclic phosphates are mutually bonded, solid content: 100% by mass) Polyphosphate ester 1: Phytic acid (manufactured by Fuso Chemical Co., Ltd., solid content: 100% by mass) (Preservatives) Isothiazolinone compound 1: isothiazolinone compound (manufactured by San-ai Oil Co., Ltd., IT-25XA, solid content: 100% by mass) (solvent) Water 1: Ion-exchanged water Alcohol 1: Isopropyl alcohol (manufactured by Taishin Chemical Co., Ltd.)

[0101] The present inventors carried out the following evaluation of the above surface treatment method. Several iron hexagonal bolts were degreased, washed with water, pickled, and washed with water (pretreatment process), then immersed in a zinc plating solution for electrolytic plating (plating process), washed with water, washed with nitric acid, and washed with water, then immersed in a phosphate-based chemical conversion treatment solution (ZEC-PC) or a zirconium-based chemical conversion treatment solution (ZEC-ZC) (chemical treatment process), washed with water, and then immersed in an aqueous rust-preventive surface treatment solution (ZEC-W) (silica film formation process), and then baked at 200°C for 4 hours (baking process), and the surface-treated hexagonal bolts were recovered. The obtained surface-treated hexagonal bolt had a zinc plating film of about 8 μm, a chemical conversion film (zinc phosphate film or zirconium film) of about 0.1 μm, and a silica film of about 1 μm on the iron base. The condition of the silica film on the surface-treated hexagonal bolts was checked, and a salt spray test (SST, test temperature: 35°C) was conducted in accordance with JIS Z2371 to measure the test time (h) until white rust appeared. In both cases where the chemical conversion coating was a zinc phosphate coating or a zirconium coating, observation of the coating showed no cracks in the silica coating, and in the SST test, no rust occurred up to 504 hours, and even at 1008 hours, only a small amount of white rust occurred. Therefore, the above-mentioned surface treatment method has shown results that it is possible to stably produce surface-coated metal substrates having excellent corrosion resistance.

[0102] The surface treatment method for a metal substrate according to the present embodiment may have the following modifications.

[0103] As one modification, a water washing process may be performed after the chemical conversion treatment process and before the silica film formation process, but a drying process may not be performed, which allows the process to be carried out continuously and improves production efficiency. As a modified example, after the baking step, an aqueous anticorrosive surface treatment liquid may be applied to the surface of the metal substrate. Also, the aqueous anticorrosive surface treatment liquid may be sprayed onto the surface of the metal substrate during construction or repair.

[0104] Each component of the surface treatment apparatus of this embodiment will be described in detail below. FIG. 2 is a diagram showing an example of the configuration of the surface treatment apparatus 100. As shown in FIG.

[0105] The surface treatment apparatus 100 of this embodiment includes a pre-treatment section 10, a plating section 20, a post-treatment section 30, and a baking section 50, which are connected in this order by a line 60. The surface treatment apparatus 100 performs each step of the above-mentioned method for treating a metal substrate by each section.

[0106] The pretreatment section 10 applies a pretreatment liquid onto the surface of a metal substrate (workpiece W). The plating section 20 applies a plating solution onto the surface of the metal substrate. The post-treatment section 30 has at least a silica film forming section 34, and preferably has a chemical conversion treatment section 32 and a silica film forming section 34. The silica film forming section 34, which is one section of the post-treatment section 30, applies an aqueous rust-preventive surface treatment liquid containing a silane compound and water onto the surface of the metal substrate to form a silica film. The baking section 50 bakes the metal base material. The line 60 means the movement path of the work W, and is composed of the movement path of a transport carrier (conveyor) that transports the work W.

[0107] FIG. 3 shows, as an embodiment, an example of a specific configuration of the surface treatment apparatus 100 that performs a pretreatment step, a plating step, a post-treatment step (a chemical conversion treatment step and a silica film forming step), and a baking step in this order. FIG. 4 shows, as a reference example, a specific configuration of a surface treatment apparatus that performs a pretreatment step, a plating step, a baking step, and a post-treatment step (chromate treatment) in this order. The arrows in Figures 3 and 4 indicate the path and order in which the workpiece W moves. 3 and 4 are assigned to correspond to the components constituting each section of the surface treatment device 100, such as the pre-treatment section 10, the plating section 20, the post-treatment section 30, and the baking section 50. Table 1 shows the relationship between the numbers in Fig. 3 and 4 and the execution tasks. The surface treatment apparatus 100 of FIG. 3 can reduce the number of overall components and can save space as compared with the surface treatment apparatus of FIG. 4, so that it is possible to achieve a significant cost reduction. The space-saving surface treatment apparatus 100 may be configured so that all components are located within the same facility.

[0108] [Table 1]

[0109] In the surface treatment apparatus 100, the workpiece W is transported by a transport carrier. Examples of the transport carrier include an overhead hanger, a belt-type or roller-type conveyor, etc. For example, the transport carrier puts the workpiece W into the plating solution in a treatment tank, and after plating, transports the workpiece W from the treatment tank to the next treatment tank.

[0110] The surface treatment apparatus 100, each section of which is connected by a line 60, can treat the workpieces W in a continuous manner as a whole.

[0111] Each of the pre-treatment unit 10, the plating unit 20, and the post-treatment unit 30 includes a treatment tank for holding a chemical solution. The treatment tank may be configured as a bathtub, a barrel, a basket, or the like. In the treatment tank, the workpiece W is immersed in the chemical solution or the chemical solution is sprayed onto the workpiece W. At this time, the treatment tank and / or the workpiece W may be rotated, or the chemical solution may be stirred. This increases the efficiency of the chemical treatment.

[0112] The chemical solution is replenished to the treatment tank from a replenishment tank. The surface treatment apparatus 100 may be configured so that the chemical solution is automatically replenished during operation. That is, the surface treatment apparatus 100 may be provided with an automatic management device that samples the chemical solution in the treatment tank, automatically analyzes the concentration of the active ingredient in the solution, replenishes any deficiency, and keeps the concentration constant.

[0113] The surface treatment device 100 may further include a wastewater treatment device. The used chemical solution is discharged to the outside by the wastewater treatment device. By using a chemical solution that does not substantially contain chromium components, it is possible to reduce the environmental load when the wastewater treatment device treats the chemical solution as wastewater.

[0114] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention. Below, examples of reference forms are given. 1. A pretreatment step of applying a pretreatment liquid onto the surface of a metal substrate; a plating step of applying a plating solution onto the surface of the metal base material; a silica film forming step of applying an aqueous rust-preventive surface treatment liquid containing a silane compound and water to the surface of the metal substrate to form a silica film; and a baking step of baking the metal substrate; A method for treating the surface of a metal substrate, comprising the steps of: 2. The surface treatment method according to 1., The surface treatment method comprises continuously performing the pretreatment step, the plating step, the silica film forming step, and the baking step online. 3. The surface treatment method according to 1. or 2., The surface treatment method includes a chemical conversion treatment step of applying a chemical conversion treatment liquid to form a chemical conversion film on the surface of the metal base material after the plating step and before the silica film forming step. 4. The surface treatment method according to 3., The surface treatment method, wherein the chemical conversion treatment liquid comprises one or more selected from the group consisting of a phosphate-based chemical conversion treatment liquid and a zirconium-based chemical conversion treatment liquid. 5. The surface treatment method according to 3. or 4., The surface treatment method, wherein a water washing treatment is carried out but a drying treatment is not carried out after the chemical conversion treatment step and before the silica film forming step. 6. The surface treatment method according to any one of 1. to 5., The surface treatment method, wherein the baking step includes a heat treatment at 150°C or higher and 300°C or lower. 7. The surface treatment method according to any one of 1. to 6., The surface treatment method, wherein the aqueous rust-preventive surface treatment liquid contains a water-dispersible resin. 8. The surface treatment method according to any one of 1. to 7., The surface treatment method, wherein the aqueous rust-preventive surface treatment liquid contains one or more members selected from the group consisting of inorganic colloid particles, a silane coupling agent, and an organometallic compound. 9. The surface treatment method according to any one of 1. to 8., The surface treatment method, wherein the pretreatment liquid, the plating liquid, and the aqueous rust-preventive surface treatment liquid are substantially free of chromium components. 10. The surface treatment method according to any one of 1. to 9., The surface treatment method, wherein the metal substrate comprises one or more selected from the group consisting of an iron-based substrate, an aluminum-based substrate, a magnesium-based substrate, a nickel-based substrate, and a cobalt-based substrate. 11. The surface treatment method according to any one of 1. to 10., The surface treatment method, wherein the plating solution contains one or more metal elements selected from the group consisting of zinc, nickel, and tin. 12. The surface treatment method according to any one of 1. to 11., The surface treatment method, wherein the pretreatment liquid comprises one or more liquids selected from the group consisting of a phosphate-based pretreatment liquid and an alkali-based pretreatment liquid. 13. A pretreatment section for applying a pretreatment liquid onto the surface of the metal substrate; a plating processing section for applying a plating solution onto a surface of the metal base material; a silica film forming section for applying an aqueous rust-preventive surface treatment liquid containing a silane compound and water onto the surface of the metal substrate to form a silica film; and A baking unit for baking the metal base material; The surface treatment device is provided with a configuration in which the above are connected in a line in this order. [Explanation of symbols]

[0115] Double work 10 Pretreatment section 20 Plating Department 30 Post-processing section 32 Chemical conversion treatment section 34 Silica film forming section 50 Baking Department 60 lines 100 Surface treatment device

Claims

1. A pretreatment step of applying a pretreatment liquid to the surface of the metal substrate; a plating step of applying a plating solution to the pretreated surface of the metal base material to form a plating film; a chemical conversion treatment step of applying a chemical conversion treatment liquid onto the plating film on the surface of the metal base material to form a chemical conversion coating; a silica film forming step of applying an aqueous rust-preventive surface treatment liquid containing a silane compound and water onto the chemical conversion coating on the surface of the metal base material to form a silica film; and a baking step of baking the metal substrate; A method for treating the surface of a metal substrate, comprising the steps of:

2. The surface treatment method according to claim 1, The surface treatment method comprises continuously performing the pretreatment step, the plating step, the silica film forming step, and the baking step online.

3. The surface treatment method according to claim 1 or 2, The surface treatment method, wherein the chemical conversion treatment liquid comprises one or more selected from the group consisting of a phosphate-based chemical conversion treatment liquid and a zirconium-based chemical conversion treatment liquid.

4. The surface treatment method according to any one of claims 1 to 3, The surface treatment method, wherein a water washing treatment is carried out after the chemical conversion treatment step and before the silica film forming step, but a drying treatment is not carried out.

5. The surface treatment method according to any one of claims 1 to 4, The baking step includes a heat treatment at 150° C. or higher and 300° C. or lower.

6. The surface treatment method according to any one of claims 1 to 5, The surface treatment method, wherein the aqueous rust-preventive surface treatment liquid contains a water-dispersible resin.

7. The surface treatment method according to any one of claims 1 to 6, The surface treatment method, wherein the aqueous rust-preventive surface treatment liquid contains one or more members selected from the group consisting of inorganic colloid particles, a silane coupling agent, and an organometallic compound.

8. The surface treatment method according to any one of claims 1 to 7, The surface treatment method, wherein the pretreatment liquid, the plating liquid, and the aqueous rust-preventive surface treatment liquid are substantially free of chromium components.

9. The surface treatment method according to any one of claims 1 to 8, The surface treatment method, wherein the metal substrate comprises one or more selected from the group consisting of an iron-based substrate, an aluminum-based substrate, a magnesium-based substrate, a nickel-based substrate, and a cobalt-based substrate.

10. The surface treatment method according to any one of claims 1 to 9, The surface treatment method, wherein the plating solution contains one or more metal elements selected from the group consisting of zinc, nickel, and tin.

11. The surface treatment method according to any one of claims 1 to 10, The surface treatment method, wherein the pretreatment liquid comprises one or more liquids selected from the group consisting of a phosphate-based pretreatment liquid and an alkali-based pretreatment liquid.

12. a pretreatment section for applying a pretreatment liquid onto the surface of the metal substrate; a plating processing section for applying a plating solution onto the pretreated surface of the metal base material to form a plating film; a chemical conversion treatment section for applying a chemical conversion treatment liquid onto the plating film on the surface of the metal base material to form a chemical conversion coating; a silica film forming section that applies an aqueous rust-preventive surface treatment liquid containing a silane compound and water onto the chemical conversion film on the surface of the metal base material to form a silica film; and A baking unit for baking the metal base material; The surface treatment device is provided with a configuration in which the above are connected in a line in this order.

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