JP7768500B2 - Method for manufacturing a composite having an alloy film formed on a substrate, and the composite - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act is applicable. Published on March 2, 2020, in the "2020 Annual Meeting Proceedings" published by the Ceramic Society of Japan.

The present invention relates to a method for easily forming an alloy film with excellent peeling resistance on a substrate, and to a composite in which an alloy film with excellent peeling resistance is formed on a substrate.

Technology for forming metal films on substrates has been used in a variety of technical fields. For example, circuit boards are manufactured by attaching copper foil to a substrate with an adhesive and then etching the copper foil to form circuits. However, if the adhesive has low affinity with the substrate or copper foil, there is a risk that the metal film will peel off when using an adhesive.

Sputtering is a technique for forming metal films on substrates without using adhesives. Sputtering involves introducing an inert gas such as Ar gas into a vacuum, applying a negative voltage to a target made of the film-forming material to generate a glow discharge, ionizing the inert gas atoms, which collide with the target surface at high speed, violently ejecting particles of the film-forming material that make up the target, which then adhere to the surface of the substrate to form a metal film. However, sputtering is expensive to implement, and because it must be performed in a vacuum, it is difficult to apply to large structures or perform in situ.

For example, concrete used in port facilities and offshore airport facilities is coated with a titanium film to protect it from corrosion by seawater and other elements, and an anti-corrosion current is supplied to the reinforcing steel bars inside (see, for example, Patent Document 1). However, it is virtually impossible to coat the surface of the massive concrete structures that make up these facilities with metal by sputtering. Therefore, thermal spraying is generally used to coat concrete building materials with metal (see, for example, Patent Document 2).

Sewage may also contain Thiobacillus bacteria, which oxidize hydrogen sulfide, sulfur, and thiosulfate ions to produce sulfuric acid, causing corrosion of concrete sewer pipes and other structures. Corrosion-resistant Hume pipes containing inorganic powder carrying antibacterial metal ions have therefore been proposed (Patent Document 3). However, simply mixing antibacterial metal ions into raw cement may not fully exert antibacterial properties, and increasing the proportion of antibacterial metal ions may result in a decrease in strength. Therefore, it is desirable to coat the surfaces of sewer pipes and other structures with antibacterial metals.

By the way, alloys, which are mixtures of two or more metals, are used to improve the physical, chemical, or mechanical properties of pure metals. For example, an alloy of copper and zinc is called brass, and has excellent properties such as electrical conductivity, thermal conductivity, corrosion resistance, and workability, making it applicable in a wide range of fields. Therefore, composites in which the substrate is coated with an alloy can be said to be highly useful.

Japanese Patent Application Publication No. 4-314880 Japanese Unexamined Patent Publication No. 1-119576 Japanese Patent Application Publication No. 9-60768

As mentioned above, thermal spraying is generally used to coat concrete building materials with metal. However, concrete building materials are porous, and the sprayed metal has difficulty penetrating into the pores. Therefore, it must be said that the metal film formed by thermal spraying has low resistance to peeling from concrete building materials.
Therefore, an object of the present invention is to provide a method for easily forming an alloy film with excellent peeling resistance on a substrate, and a composite produced by the present invention and having an alloy film with high peeling resistance on its surface.

The present inventors have conducted extensive research to solve the above problems. As a result, they have discovered that, although they had expected that a metal oxide film would naturally be formed by applying a solution of a chelate complex of a specific metal component to a substrate and then heat-treating it, the film formed had a metallic luster and, upon analysis, was found to be composed almost entirely of an alloy, leading to the completion of the present invention.
The present invention will now be described.

[1] A method for producing a composite in which an alloy film is formed on a substrate, comprising:
applying a metal chelate complex solution containing a high standard oxidation-reduction potential metal component having an ionization tendency lower than that of Cd, a low standard oxidation-reduction potential metal component having an ionization tendency equal to or higher than that of Cd, and a chelating agent to the substrate;
a step of heat treating the portion of the substrate onto which the metal chelate complex solution is applied,
The method according to claim 1, wherein the molar ratio of the high standard redox potential metal component to the low standard redox potential metal component is 4 or greater.
[2] The method according to [1], wherein the metal chelate complex solution further contains a surfactant.
[3] The method according to [1] or 2, wherein the substrate is a hardened cement body.
[4] The method according to any one of [1] to [3], wherein the low standard oxidation-reduction potential metal component is Cu or Ni.
[5] The method according to any one of [1] to [4], wherein the high standard oxidation-reduction potential metal component is Zn.
[6] The method according to any one of [1] to [5], wherein the chelating agent is an aminocarboxylic acid chelating agent.
[7] A substrate and an alloy film layer,
The substrate is a hardened cement paste,
the alloy film layer contains a high standard redox potential metal component having an ionization tendency lower than that of Cd and a low standard redox potential metal component having an ionization tendency equal to or higher than that of Cd,
A composite, characterized in that the high standard oxidation-reduction potential metal component and the low standard oxidation-reduction potential metal component are present on the substrate side of the interface between the substrate and the alloy film layer.

The method of the present invention makes it possible to easily form an alloy film on the surface of a substrate, and it is possible to treat large substrates such as concrete building materials, and in situ treatment is also possible. Furthermore, because the method of the present invention uses a metal chelate complex solution rather than molten metal as in thermal spraying methods, it is also possible to fill the pores of porous substrates with metal, making it possible to form an alloy film with excellent peel resistance even on the surface of porous substrates. Therefore, the composite of the present invention is extremely useful industrially as a building material with excellent corrosion resistance.

1 shows the results of XRD analysis of a metal film obtained by applying a Cu/Zn chelate complex solution onto a polycrystalline alumina substrate and heating it with a hydrogen flame. 1 shows the results of XRD analysis of a metal film obtained by applying a Cu/Zn chelate complex solution to an aluminum alloy A5052 plate and heating it with a hydrogen flame.

The present invention relates to a method for producing a composite in which an alloy film is formed on a substrate. The method for producing a composite according to the present invention includes the steps of applying a metal chelate complex solution to the substrate, the metal chelate complex solution containing a high standard redox potential metal component with an ionization tendency lower than that of Cd, a low standard redox potential metal component with an ionization tendency equal to or greater than that of Cd, and a chelating agent, and heat-treating the portion of the substrate coated with the metal chelate complex solution. Each step of the method of the present invention will be explained below, but the present invention is not limited to the specific examples below.

1. Coating Step In this step, a metal chelate complex solution containing a high standard oxidation-reduction potential metal component having an ionization tendency lower than that of Cd, a low standard oxidation-reduction potential metal component having an ionization tendency equal to or higher than that of Cd, and a chelating agent is coated onto a substrate.

Ionization tendency is a relative indicator of the ease with which an element becomes ions, primarily in aqueous solution. The lower the ionization tendency, the higher the standard redox potential E°. Cd has an E° value of -0.4025 V. In this invention, we use high standard redox potential metal components with higher E° values and lower ionization tendency, and Cd and low standard redox potential metal components with lower E° values than Cd and higher ionization tendency. Examples of high standard redox potential metal components with low ionization tendency include, in descending order of ionization tendency, Co, Ni, Mo, Sn, Pb, Sb, Bi, Cu, Hg, Ag, Pd, Ir, Pt, and Au. Examples of low standard redox potential metal components with high ionization tendency include, in descending order of ionization tendency, Cd, Fe, Cr, Zn, Mn, Zr, and Al. Note that in this disclosure, the relative values of high standard redox potential metal components and low standard redox potential metal components are purely relative.

The alloy film formed on the surface of the substrate can be used as an electrode. For example, if an alloy film is formed on the surface of a hardened cement body and a voltage is applied, the alloy film will act as a corrosion-resistant coating. Furthermore, the metal elements can be selected based on their usefulness. Only one high standard redox potential metal component and one low standard redox potential metal component may be selected, or two or more may be selected and combined.

Examples of alloys include Krupp steel (Ni-Cr), Permalloy (Ni-Fe), chromium-molybdenum steel (Fe-Cr-Mo), manganese-molybdenum steel (Fe-Mn-Mo), stainless steel (Fe-Ni-Cr), and maraging steel (Fe-18- 30Ni (Co, Mo)), 42 Alloy (Fe-42Ni), Invar (Fe-36Ni), Kovar (Fe-29Ni-17Co), Permendur (Fe-Co), brass (Cu-Zn), nickel silver (Cu-27Zn-18Ni), Nordic Gold (89Cu-5Al-5Zn-1Sn), Kunife (60Cu-20Ni-20Fe), duralumin (Al-Cu), Hastelloy (50Ni-Mo-Cr-Fe), Inconel (72Ni-15Cr-Fe), Nichrome (80Ni-20Cr), Sun Platinum (85Ni-11Cr-3Ag), shape memory alloy (Ni-Ti), and Stellite (Co-30Cr-10W).

In the present invention, the molar ratio of the high standard redox potential metal component to the low standard redox potential metal component (number of moles of high standard redox potential metal component/number of moles of low standard redox potential metal component) is 4 or more. If this molar ratio is less than 4, the amount of metal oxide contained in the alloy film will be excessively large. The molar ratio is preferably 5 or more or 6 or more, more preferably 8 or more or 10 or more, and even more preferably 15 or more. There is no particular upper limit to this molar ratio, but if the molar ratio is too high, the properties of the low standard redox potential metal component may not be utilized, so it is preferably 50 or less.

The chelating agent is not particularly limited as long as it can form a chelate with the metal component and improve its solubility. Examples include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, ethylenediaminediacetic acid, 1,2-diaminopropanetetraacetic acid, 1,3-diaminopropanetetraacetic acid, hexamethylenediaminetetraacetic acid, 1,2-cyclohexanediaminetetraacetic acid, diaminopropanoltetraacetic acid, hydroxyethylenediaminetriacetic acid, glycol ether diaminetetraacetic acid, ethylenediaminedi(o-hydroxyphenyl)acetic acid, iminodiacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, methylglycinediacetic acid, and ethylenediaminediproacetic acid. Examples of chelating agents that can be used include aminocarboxylic acid chelating agents such as pionic acid, nitrilotripropionic acid, ethylenediaminedisuccinic acid, 1,3-diaminopropanedisuccinic acid, glutamic acid-N,N-diacetic acid, and aspartic acid-N,N-diacetic acid; phosphonic acid chelating agents such as hydroxyethylidene diphosphonic acid, nitrilotrismethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, 2-phosphono-1,2,4-butanetricarboxylic acid, phosphonohydroxyacetic acid, and hydroxyethyldimethylenephosphonic acid; and hydroxycarboxylic acid chelating agents such as gluconic acid, citric acid, tartaric acid, and malic acid.

The chelating agent is preferably water-soluble. A single chelating agent may be used, or two or more may be used in combination. Among these, aminocarboxylic acid chelating agents are preferably used because they are easily thermally decomposed in the subsequent heat treatment step. Preferred aminocarboxylic acid chelating agents include one or more selected from ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and nitrilotriacetic acid, with ethylenediaminetetraacetic acid being more preferred. These chelating agents are inexpensive and easily available, and metal chelate complex solutions formed from these chelating agents stably dissolve metal components, making it easy to prepare clear metal chelate complex solutions.

From the standpoints of cost and ease of handling, the solvent for the metal chelate complex solution is preferably water or a mixed solvent of water and a water-miscible organic solvent. Examples of water-miscible organic solvents include alcoholic solvents such as methanol, ethanol, and isopropanol. The solvent for the metal chelate complex solution preferably contains at least water, and for example, the concentration of water in the solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more or 95% by mass or more. From the standpoint of low environmental impact, it is particularly preferable to use substantially only water as the solvent; therefore, the metal chelate complex solution is preferably an aqueous chelate complex solution.

The content of the metal component in the metal chelate complex solution is preferably adjusted so that it is sufficiently dissolved by the chelating agent. For example, it can be 0.1% by mass or more and 15% by mass or less, and preferably 10% by mass or less. The content of the chelating agent in the metal chelate complex solution is preferably equal to or greater than the theoretical amount required for chelate coordination with the metal component, and is preferably 0.8 times by mole or more and 1.5 times by mole or less per mole of metal ions of the metal component. The molar ratio is preferably 0.9 times by mole or more, more preferably 0.95 times by mole or more, and preferably 1.2 times by mole or less, and more preferably 1.1 times by mole or less. The concentration of the metal chelate complex in the metal chelate complex solution can be, for example, 1% by mass or more and 60% by mass or less, and preferably 10% by mass or more and 40% by mass or less.
The metal chelate complex solution may contain additives in addition to the metal element and the chelating agent, including, but not limited to, surfactants and viscosity modifiers.

The surfactant reduces the surface tension of the metal chelate complex solution. For example, if the substrate is porous and the metal chelate complex solution contains a surfactant, the metal chelate complex solution can more easily penetrate into the pores. As a result, the alloy is also present in the pores, increasing the peeling resistance of the alloy film from the substrate.

Surfactants that can be used include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants without any particular restrictions. However, nonionic surfactants are preferred due to their affinity with porous substrates such as hardened cement. Nonionic surfactants are not particularly limited, but examples include acetylene-based surfactants, polyalkylene glycol-based nonionic surfactants, and silicone-based surfactants.

Viscosity adjusters are primarily used to increase the viscosity of the metal chelate complex solution and prevent dripping. Examples include polysaccharides, polymers such as polyethylene glycol and acrylic polymers, and amides.

The amount of additive used may be adjusted as needed to ensure that the effects of each component are fully achieved. For example, in the case of a surfactant, its concentration in the metal chelate complex solution may be 0.01% by mass or more and 1% by mass or less. This concentration is preferably 0.05% by mass or more, and preferably 0.5% by mass or less, and more preferably 0.2% by mass or less. The concentration of the viscosity modifier may be adjusted according to the desired viscosity of the metal chelate complex solution.

The metal chelate complex solution can be prepared by dissolving at least a metal compound containing a high standard redox potential metal component, a metal compound containing a low standard redox potential metal component, and a chelating agent in a solvent. Alternatively, the metal chelate complex solution may be prepared by dissolving a chelate complex of a metal element in a solvent.

Metal compounds containing high standard redox potential metal components and/or low standard redox potential metal components can include oxides, hydroxides, halide salts such as chlorides and bromides, carbonates, nitrates, sulfates, phosphates, borates, silicates, etc. Among these, metal oxides, metal hydroxides, metal carbonates, and metal nitrates are preferred. By preparing a metal chelate complex solution using these metal compounds, it is possible to prevent unwanted elements from being mixed into the alloy film formed by the coating and heat treatment processes.

The chelating agent used in preparing the metal chelate complex solution can be the free acid type or salt of the chelating agent described above. It is preferable to use an ammonium salt or an amine salt as the salt of the chelating agent. The use of such a chelating agent allows the ammonium ion or amine component to be easily decomposed during the heat treatment process, preventing unwanted elements from being mixed into the alloy film.

If the valence of the chelating agent is not equal to the valence of the metal ion to be chelated, a cation or anion may be added to make the metal chelate complex electrically neutral. Examples of cations include ammonium ions and quaternary ammonium cations. Examples of anions include nitrate ions and halide ions such as chloride ions and bromide ions, but nitrate ions are preferred because they are less likely to remain in the alloy film.

The temperature when preparing the metal chelate complex solution is not particularly limited as long as it is above the melting point and below the boiling point of the solvent, but is preferably 20°C or higher, more preferably 35°C or higher, even more preferably 50°C or higher, and preferably 80°C or lower, more preferably 70°C or lower. If the chelating agent or metal chelate complex does not dissolve completely, it is preferable to add ammonia, an amine, or the like to achieve complete dissolution.

When using the metal chelate complex as a raw material for the metal chelate complex solution, the metal chelate complex can be precipitated as a solid from the metal chelate complex solution prepared as described above, and this can be used as the raw material for the metal chelate complex solution. The metal chelate complex can be precipitated by adding a poor solvent to the metal chelate complex solution, or by heating, concentrating, or cooling the metal chelate complex solution. If necessary, further treatments such as filtration, drying, washing, or recrystallization may be performed.

The substrate to which the metal chelate complex solution is applied is not particularly limited as long as it has sufficient heat resistance so that it will not change or deform when heated in the subsequent heat treatment process, and is preferably composed primarily of inorganic materials. From this perspective, hardened cement paste, minerals, ceramics, and metals are preferably used as substrates. The substrate may also be real estate such as a structure, or may be a clay pipe or building material. Examples of real estate substrates include the walls and ceilings of structures such as tunnels, underground shopping malls, and ports, the walls and ceilings of buildings such as buildings, roads, bridges, and cliffs.

Cement is primarily composed of calcium oxide (CaO), silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and iron(III) oxide (Fe ₂ O ₃ ). Portland cement contains tricalcium silicate (alite, 3CaO·SiO ₂ ), dicalcium silicate (belite, 2CaO·SiO ₂ ), calcium aluminate (aluminate, 3CaO·Al ₂ O ₃ ), calcium aluminoferrite (ferrite, 4CaO·Al ₂ O ₃ ·Fe ₂ O ₃ ), and calcium sulfate (gypsum, CaSO ₃ ·2H ₂ O). Cement hardens through chemical reactions in which calcium oxide becomes calcium hydroxide and other components become hydrated. In addition to Portland cement, there are also blended cements, which are made by mixing Portland cement with blast furnace slag, fly ash, or silica-based admixtures. Mortar is made by mixing sand, which is a fine aggregate, with cement and water and then hardening it, while concrete is a hardened product made by solidifying sand, gravel, water, etc. with cement. As mentioned above, cement hardens through a hydration reaction, and the water that is not involved in the reaction evaporates, so typical hardened cement products are porous.

As mentioned above, hardened cement pastes are hardened by hydration and therefore tend to be degraded by water, particularly seawater, and because they contain calcium hydroxide, they also tend to be degraded by acids. However, the method of the present invention can coat part or all of the surface of the hardened cement paste substrate with an alloy film, thereby increasing the durability of the hardened cement paste.

Minerals include limestone such as marble, silica, and Oya stone. Ceramics include metal oxides such as alumina, zirconia, barium titanate, and silica; metal hydroxides such as hydroxyapatite; metal carbides such as silicon carbide; and metal nitrides such as silicon nitride. Metals that make up the substrate include metals other than those that form alloy films. Examples include iron; iron alloys such as carbon steel, stainless steel, chromium-molybdenum steel, and manganese-molybdenum steel; aluminum alloys such as duralumin; and nickel alloys such as Hastelloy and Monel.

The method for applying the metal chelate complex solution to the substrate is not particularly limited; for example, application using a brush or roller, as with paint, or spray application can be used. Depending on the size of the substrate, application by dipping or spin coating is also possible.

The metal chelate complex solution may be applied to the entire surface of the substrate, or to only a portion of it. Two or more types of metal chelate complex solutions may be used and applied to different areas to enhance the design of the applied areas. Furthermore, depending on the desired thickness of the alloy film, it is possible to increase the thickness of the metal chelate complex coating by repeatedly applying and drying the metal chelate complex solution, or by applying a thicker layer of a more viscous metal chelate complex solution.

The drying conditions after applying the metal chelate complex solution to the substrate surface can be adjusted appropriately depending mainly on the solvent used in the metal complex chelate solution. For example, the solution can be heated at a temperature of 40°C or higher and 80°C or lower for 5 minutes or longer and 1 hour or shorter. Alternatively, the solution can be left at room temperature until the coating is dry.

2. Heat Treatment Step In this step, the portion of the substrate coated with the metal chelate complex solution is heat-treated to form an alloy film. More specifically, by heating the portion coated with the metal chelate complex solution, organic components such as chelating agents and surfactants are thermally decomposed and removed. Furthermore, it is believed that, due to the use of a high standard oxidation-reduction potential metal component with a relatively low ionization tendency in the present invention, a film of the high standard oxidation-reduction potential metal is formed rather than a metal oxide, and that all or most of the low standard oxidation-reduction potential metal component with a relatively high ionization tendency also forms a metal film rather than a metal oxide.

The temperature in this process is adjusted within a range that allows the organic components to thermally decompose. For example, it can be set to 1000°C or higher and 3500°C or lower. A temperature of 1200°C or higher is preferred, with 1300°C or higher being more preferred. Heating can be performed using a flame obtained by burning a combustible gas. The combustible gas is not particularly limited, and examples include hydrogen, acetylene, propane, and butane. The inventors initially believed that a reducing hydrogen flame was necessary to form an alloy film. However, the method of the present invention makes it possible to form an alloy film using an acetylene or butane flame. The heat treatment time should also be adjusted appropriately. For example, if the formation of an alloy film is observed, the heat treatment should be stopped to prevent oxidation to metal oxide. The formation of an alloy film can be confirmed by discoloration from metal ions or the appearance of a metallic luster.

The heat treatment may be carried out using a laser instead of a flame. A laser is a light that is directional (linear), monochromatic, and coherent, and by irradiating a target object with a laser, the surface temperature of the target object can be rapidly increased, making processing possible. In the present invention, the reaction is caused to proceed by irradiating the area coated with the metal chelate complex solution with laser light and adjusting the surface temperature to the above range. The laser to be used may be selected appropriately within the range that allows the formation of an alloy film, and for example, a YAG laser or _CO2 laser, which are commonly used for laser processing, can be used.

The laser irradiation conditions can be adjusted so that an alloy film is formed on the area where the metal chelate complex solution is applied. For example, the higher the energy of the irradiated laser, the shorter the heat treatment time, but it is not desirable to use a laser with such high energy that it damages the formed alloy film. Specifically, it is preferable to use a laser with a relatively long wavelength, such as 1.06 μm or 10.6 μm, and a relatively low energy of 0.01 msec or more and 1 msec or less, with a pulse rate of approximately 1 pps or more and 100 pps or less. The laser irradiation time can be adjusted until the coated surface acquires a metallic luster.

The substrate is preferably placed in the flame or at the end of the flame. The distance from the burner that generates the flame to the substrate can be adjusted, for example, within a range of 30 mm to 300 mm. In the heat treatment process, the substrate is preferably heated by the flame while the substrate and/or burner are moved at a relative speed (relative to each other) of 10 mm/sec to 200 mm/sec. This prevents damage or deterioration of the substrate and facilitates the formation of an alloy film on the substrate surface. When the substrate and/or burner are moved in this manner, the substrate may be heated by the flame once or multiple times. In the latter case, it is convenient to heat the substrate by the flame while moving the substrate and/or burner back and forth, for example. When a laser is used, it is preferable to adjust the distance between the focusing system of the laser processing machine and the surface to be coated, for example, so that the amount of energy and irradiation area applied to the surface to be coated are appropriate.

As described above, a composite having an alloy film formed on a substrate can be obtained. According to the manufacturing method of the present invention, an alloy film can be easily formed on a substrate by applying a metal chelate complex solution to the substrate and then heat-treating it with a flame or laser. In other words, the composite of the present invention refers to a composite comprising a substrate and an alloy film layer, with at least a portion of the substrate being coated with the alloy film layer. The alloy film thus formed can be formed as a thin film, thereby reducing the costs associated with applying and forming metal. The thickness of the alloy film is not particularly limited, but can be, for example, 0.5 μm or more and 100 μm or less. Furthermore, according to the manufacturing method of the present invention, an alloy film can be easily formed in situ on a substrate, even if it is an immovable substrate such as a civil engineering structure or building.

As mentioned above, hardened cement pastes are generally porous because they are formed through chemical reactions such as hydration and contain relatively large-particle sand and gravel to enhance strength. Examples of hardened cement pastes include hardened cement itself, mortar, which is a hardened mixture of cement and sand, and concrete, which is a hardened mixture containing relatively large-particle gravel. All of these are porous. In contrast, thermal spraying methods using molten metal, for example, are unable to fill the pores of hardened cement pastes with metal, resulting in poor peeling resistance for the formed alloy film. However, the method of the present invention uses a liquid metal chelate complex solution, which allows the metal chelate complex solution to penetrate into the pores, resulting in the formation of an alloy film with excellent peeling resistance. A metal chelate complex solution containing a surfactant and reduced surface tension allows the solution to more easily penetrate even smaller pores.

Specifically, in the composite of the present invention, in which the substrate is a hardened cement paste, the metal component is present closer to the substrate than to the interface between the substrate and the alloy film, resulting in high peeling resistance of the alloy film. The interface between the substrate and the metal film refers to the average line at a reference length of 100 μm when the composite is cut in a direction perpendicular to the planar direction of the alloy film and the cross section is observed at a magnification of 1000x or more and 10,000x or less using a scanning electron microscope or the like. The average line here refers to the line obtained by converting the filtered waviness curve for the roughness curve into a straight line using the least squares method (JIS B 0601-1994).

The present invention will be explained in more detail below by showing examples, but the scope of the present invention is not limited to these examples.

Example 1: Formation of Cu—Zn alloy film on polycrystalline alumina plate (1) Preparation of metal chelate complex aqueous solution Ethylenediaminetetraacetic acid (150.7 g, 0.516 mol) was placed in a 500 mL beaker, and distilled water was added to bring the total volume to 350 g. 25% aqueous ammonia (70.2 g) and copper(II) oxide (41.1 g, 0.516 mol) were then added, and the mixture was stirred at 90°C for 4 hours to completely dissolve the solution. Distilled water was then added to dilute the solution, yielding a 40% by mass aqueous solution of EDTA.Cu.( _NH4 ) ₂ .
Similarly, ethylenediaminetetraacetic acid (150.0 g, 0.514 mol) was placed in a 500 mL beaker, and distilled water was added to bring the total volume to 350 g. 25% aqueous ammonia (69.9 g) and zinc oxide (41.3 g, 0.514 mol) were then added, and the mixture was stirred at 80°C for 3 hours to completely dissolve the EDTA.Zn.(NH4) ₂ . The mixture was then diluted with distilled water to obtain a 40% by mass aqueous solution of EDTA.Zn.( _NH4 ).
The obtained solutions were mixed to give a Cu:Zn molar ratio of 0.61:0.39, 0.71:0.29, 0.80:0.20, 0.90:0.10, or 0.95:0.05, and a nonionic surfactant ( ^Olfine® EXP.4300, manufactured by Nissin Chemical Industry Co., Ltd.) was added to the mixture to give a concentration of 0.1% by mass.

(2) Formation of Cu—Zn Alloy Film Each of the metal chelate complex aqueous solutions was applied to a 5 cm×2.5 cm polycrystalline alumina substrate in an amount of 0.012 g/cm ² per unit area, and dried at 65° C. for 20 minutes.
Next, using a spray gun ("6P-II" manufactured by Sulzer Metco), hydrogen was supplied at a rate of 32.5 L/min and oxygen at a rate of 43.0 L/min, and the spray gun was moved at a speed of 50 mm/s from a distance of 13 cm, scanning the front surface of the substrate three times to heat the coating.
The resulting coating was analyzed by X-ray diffraction using an X-ray diffraction apparatus ("Ultima IV" manufactured by Rigaku Corporation). The results are shown in Figure 1. In Figure 1, (a) to (e) indicate Cu:Zn (molar ratio). Specifically, Cu:Zn = 0.61:0.39 (a), 0.71:0.29 (b), 0.80:0.20 (c), 0.90:0.10 (d), and 0.95:0.05 (e) (molar ratio).

As shown in the results in Figure 1, the smaller the relative molar ratio of Zn to Cu, the smaller the ZnO peak intensity. At Cu:Zn = 0.80:0.20 (c), a ZnO peak was detected analytically, but the peak was not visible to the naked eye. According to the powder X-ray diffraction database published by the International Centre for Diffraction Data (ICDD), the diffraction peak angles (2θ) of Cu(111) and Cu(200) (ICDD-00-050-1333) are 43.2970° and 50.4330°, respectively, the diffraction peak angles (2θ) of Cu _0.951 Zn _0.049 (111) and (200) (ICDD-00-050-1333) are 43.2690° and 50.3930°, respectively, and the diffraction peak angles (2θ) of Cu _0.75 Zn _0.25 The diffraction peak angles (2θ) of (111) and (200) (ICDD-01-071-7924) are 42.6735° and 49.6865°, respectively, and the diffraction peak angles (2θ) of Cu _0.64 Zn _0.36 (111) and (200) (ICDD-00-050-1333) are 42.4350° and 49.2751°, respectively. The diffraction peak angles of Cu-Zn alloys tend to shift to lower angles as the Zn content increases. In the measurement results of this example, the diffraction peak angles (2θ) of (111) of Cu:Zn = 0.95:0.05 (e) and 0.90:0.10 (d) are 43.14°, and Cu:Zn = 0.80:0.20 (c) to 0.61 The diffraction peak angle (2θ) of Cu:Zn=0.95:0.39(a)(111) was 43.12°, the diffraction peak angle (2θ) of Zn=0.95:0.05(200) was 50.28°, the diffraction peak angle (2θ) of Cu:Zn=0.90:0.10(200) was 50.26°, and the diffraction peak angle (2θ) of Cu:Zn=0.80:0.20-0.61:0.39(200) was 50.24°, and similarly, a tendency was observed in which the diffraction peak angle shifted to a lower angle as the Zn content increased. Therefore, it was shown that a Cu—Zn alloy film was formed well, particularly when the molar ratio of Zn to Cu was 4 or more.

Example 2: Formation of Cu—Zn alloy film on aluminum alloy plate A Cu—Zn alloy film was formed on an aluminum alloy plate in the same manner as in Example 1, except that the Cu:Zn (molar ratio) in the metal chelate complex aqueous solution was changed to 0.61:0.39, 0.71:0.29, 0.90:0.10, or 0.95:0.05.
The obtained coating was analyzed by X-ray diffraction using an X-ray diffraction apparatus ("Ultima IV" manufactured by Rigaku Corporation). The results are shown in Figure 2. In Figure 2, (a) to (d) indicate Cu:Zn (molar ratio). Specifically, Cu:Zn = 0.61:0.39 (a), 0.71:0.29 (b), 0.90:0.10 (c), and 0.95:0.05 (d) (molar ratio).

As shown in Figure 2, only Cu:Zn = 0.61:0.39 (a) exhibited ZnO diffraction peaks. Furthermore, while the (111) and (200) diffraction peak angles (2θ) tended to be higher for Cu:Zn = 0.71:0.29 (b) and 0.61:0.39 (a), the (111) diffraction peak angle (2θ) for Cu:Zn = 0.95:0.05 (d) was 42.80°, and the (111) diffraction peak angle (2θ) for Cu:Zn = 0.90:0.10 (c) was 42. 74°, the diffraction peak angle (2θ) for Cu:Zn = 0.95:0.05 (d) (200) was 49.96°, and the diffraction peak angle (2θ) for Cu:Zn = 0.90:0.10 (c) (200) was 49.90°. This suggests that a Cu-Zn alloy film is formed well when the molar ratio of Zn to Cu is 4 or higher.

The method of the present invention makes it possible to easily produce alloy film-coated composites with excellent corrosion resistance and antibacterial properties that can be used for concrete building materials in tunnels, underground shopping malls, ports, and other areas where deterioration due to moisture and seawater is a concern, as well as for sewer pipes where deterioration due to moisture and acids produced by microorganisms is a concern.

Claims (6)

A method for producing a composite in which an alloy film is formed on a substrate, comprising:
applying a metal chelate complex solution containing Cu, Zn, a chelating agent, and a surfactant to the substrate; and
a step of heat treating the portion of the substrate onto which the metal chelate complex solution is applied,
The method according to claim 1, wherein the molar ratio of Cu to Zn is 4 or greater. The method of claim 1, wherein the substrate is a hardened cement paste. The method of claim 1 or 2, wherein the molar ratio of Cu to Zn (number of moles of Cu/number of moles of Zn) is 4 or more and 50 or less. The method of any one of claims 1 to 3, wherein the metal chelate complex solution contains water or a mixed solvent of water and a water-miscible organic solvent as the solvent. The method according to any one of claims 1 to 4, wherein the Cu and Zn contents of the metal chelate complex solution are 0.1% by mass or more and 15% by mass or less. The method according to any one of claims 1 to 5, wherein the chelating agent is an aminocarboxylic acid chelating agent.