Chromium-plated member and method for producing same

Abstract

The purpose of the present invention is to provide: a chromium-plated member which exhibits excellent corrosion resistance even if the upper layer is a trivalent chromium-plated layer, in particular, corrosion of copper or a copper alloy is suppressed, and which has a good appearance; and a manufacturing method which enables the production of such a chromium-plated member. This chromium-plated member is provided with: a base body having a surface layer comprising copper or a copper alloy; a first nickel plating layer formed in contact with the surface layer of the substrate; a second nickel plating layer formed on the first nickel plating layer in a contact manner; and a trivalent chromium plating layer formed on the second nickel plating layer in a contact manner, the chromium plating member being characterized in that the second nickel plating layer has an anode potential of-215 mV to-290 mV at a current density of 0.1 mA / cm2, and the first nickel plating layer has a potential lower than that of the second nickel plating layer by 15 mV to 150 mV.

Description

Technical Field

[0001] The present invention relates to chromium-plated components, particularly nickel-chromium plated components, and a method for manufacturing the same. Background Art

[0002] Conventionally, chromium plating has been performed for purposes such as decoration of a base material, corrosion prevention, and imparting conductivity. Chromium plating generally has a silver-white appearance, and thus has excellent aesthetic decorativeness and is useful as a decorative coating film. In addition, a chromium plating layer can form a passivation film on the surface by its self-passivation ability, and thus is also excellent in corrosion resistance. In particular, a product having a chromium plating film formed on the surface of a resin base material is lightweight and low in cost compared to a product made of a metal raw material, and thus is used as various components typified by automotive components.

[0003] Among chromium-plated components (products), products having a nickel plating layer as a base (nickel-chromium plated products) are particularly excellent in decorativeness and corrosion resistance and are used for various base materials typified by resin. It is considered that the high corrosion resistance of nickel-chromium plating is due to sacrificial corrosion of the underlying nickel layer, thereby preventing corrosion of the chromium plating layer.

[0004] The corrosion resistance of the nickel layer itself in a nickel-chromium plated product can be improved by forming a two-layer or three-layer structure composed of a semi-bright nickel plating layer containing almost no sulfur component, a bright nickel plating layer containing a sulfur component, and other nickel plating layers having different compositions (see, for example, Patent Documents 1 to 4). This is because the bright nickel plating layer having a low potential is sacrificially corroded, and in a chromium-plated component having such a nickel plating layer, the corrosion resistance is higher. Recently, the requirement for the corrosion resistance of chromium-plated components has been increasing, and further research on improving the corrosion resistance, typified by the structure of the nickel plating layer as a base, has been continuously conducted.

[0005] For example, Patent Documents 1 and 2 disclose a nickel-chromium plated product in which a semi-bright nickel plating layer, a bright nickel plating layer, and a eutectic nickel plating layer are sequentially provided on a substrate, and a chromium plating layer is added thereon. Here, the eutectic nickel plating layer refers to a layer in which fine particles such as silica are eutectically formed to form a microporous structure. Since the corrosion current is dispersed by a large number of pores, corrosion of the bright nickel plating layer is suppressed. In the invention described in Patent Document 1, the corrosion resistance was improved by further adjusting the potential difference between the respective nickel plating layers. In addition, in the invention described in Patent Document 2, the corrosion resistance was improved by making the concentration of metal ions having a high electrode potential different between the respective nickel plating layers.

[0006] Patent Document 3 discloses a surface modification method that oxidizes the surface of a chromium-plated component having the same structure as those in Patent Documents 1 and 2, and forms a chromium oxide coating film on the surface of the chromium plating film. In addition, Patent Document 4 discloses a chromium-plated component that sequentially includes copper plating, sulfur-free nickel plating (semi-bright nickel plating), bright nickel plating, high-potential nickel plating, and trivalent chromium plating with a microporous structure or a microcrack structure on a resin substrate. In Patent Document 4, as the high-potential nickel plating, eutectoid nickel plating (MP nickel plating) having a microporous structure is also disclosed. The inventions described in Patent Documents 3 and 4 are technologies for improving the corrosion resistance of plated components by modifying the chromium plating layer, but in either technology, the nickel plating layer has a three-layer structure with a semi-bright nickel plating layer as the lowermost layer.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Laid-Open No. 5-171468

[0010] Patent Document 2: Japanese Patent Laid-Open No. 6-146069

[0011] Patent Document 3: Japanese Patent Laid-Open No. 2007-275750

[0012] Patent Document 4: Japanese Patent Laid-Open No. 2010-185116 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] However, there is still room for improvement in the corrosion resistance of chromium-plated components having a nickel-based underlayer. In recent years, due to environmental considerations, trivalent chromium is often used instead of hexavalent chromium in chromium plating. However, if such trivalent chromium plating is performed on a nickel plating layer, the corrosion resistance may not necessarily be as good as that of hexavalent chromium plating. The plated products described in Patent Documents 1 and 2 are both manufactured by hexavalent chromium plating, and when the chromium plating layer is formed by trivalent chromium plating, the corrosion resistance may become insufficient. In addition, in the method of passivating the surface of the chromium plating layer as described in the invention of Patent Document 3, processes and equipment for surface oxidation are required, resulting in an increase in manufacturing costs.

[0015] In the invention described in Patent Document 4, there are usually the following difficulties: in terms of making the trivalent chromium plating layer have a microporous structure, it is difficult to obtain sufficient corrosion resistance unless non-conductive particles are used to form micropores.

[0016] In addition, in many nickel-chromium plated articles, the nickel plating layer has a three-layer structure (also in the plated articles described in Patent Documents 2 and 4 where two layers are required as the nickel plating layer). A semi-bright nickel plating layer (sulfur-free nickel plating layer) is formed on the substrate side, and a bright nickel plating layer is formed on top of it. Thus, from the viewpoint of preventing corrosion, the semi-bright nickel plating layer with a potential higher than that of the bright nickel plating layer covers the copper or copper alloy directly below. However, according to the present inventors' recent discovery, if the potential of the nickel plating layer in contact with the substrate is high, when the corrosion of the nickel plating layer on the substrate side reaches the substrate, there is a tendency for the corrosion to proceed rapidly. In contrast, through the research of the inventors of the present application, it is known that by making the nickel plating layer on the substrate side a bright nickel plating layer with a potential lower than that of the semi-bright nickel plating layer, corrosion can be prevented.

[0017] However, it is known that even if the nickel plating layer on the substrate side is made a bright nickel plating layer, expansion or the like may occur due to the corrosion of copper or copper alloy.

[0018] In order to solve the above problems, an object of the present invention is to provide a chromium-plated component that exhibits excellent corrosion resistance even when the upper layer is a trivalent chromium plating layer, in which the corrosion of copper or copper alloy is suppressed and the appearance is good, and a manufacturing method capable of manufacturing such a chromium-plated component.

[0019] Means for Solving the Problems

[0020] The present inventors have found that in a chromium-plated component, different from the conventional nickel-chromium plating, by forming two low-potential nickel plating layers on the substrate and specifying the potential of each nickel plating layer within a specific range, excellent corrosion resistance is exhibited, the corrosion of copper or copper alloy is suppressed, and the appearance also becomes good, thereby completing the present invention.

[0021] That is, the present invention provides the following (1) to (10).

[0022] (1) A chromium-plated component, comprising: a substrate having a surface layer made of copper or copper alloy; a first nickel plating layer formed in contact with the surface layer of the substrate; a second nickel plating layer formed in contact with the first nickel plating layer; and a trivalent chromium plating layer formed in contact with the second nickel plating layer, wherein the second nickel plating layer has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 and the first nickel plating layer has a potential 15 mV to 150 mV lower than that of the second nickel plating layer.

[0023] (2) The chromium-plated component according to (1) above, wherein the film thickness ratio of the first nickel plating layer to the second nickel plating layer is 1:10 to 30:1.

[0024] (3) The chromium plating component according to (1) above, wherein the film thickness ratio of the first nickel plating layer to the second nickel plating layer is 1:4 to 14:1.

[0025] (4) The chromium plating component according to any one of (1) to (3) above, wherein the total film thickness of the first nickel plating layer and the second nickel plating layer is 1 μm to 30 μm.

[0026] (5) The chromium plating component according to any one of (1) to (4) above, wherein an electrolytic chemical conversion treatment film and / or an immersion chemical conversion treatment film is further provided on the trivalent chromium plating layer.

[0027] (6) The chromium plating component according to any one of (1) to (5) above, wherein the second nickel plating layer is a layer containing no non-conductive fine particles.

[0028] (7) The chromium plating component according to any one of (1) to (6) above, wherein the substrate is made of one or more materials selected from the group consisting of resin, ceramic, and metal and has the above-mentioned surface layer made of copper or a copper alloy, or is a substrate made of copper or a copper alloy.

[0029] (8) A method for manufacturing a chromium plating component, the method for manufacturing the chromium plating component comprising the following steps: forming a first nickel plating layer in contact with the surface layer on a substrate having a surface layer mainly made of copper or a copper alloy; forming a second nickel plating layer in contact with the first nickel plating layer; and forming a trivalent chromium plating layer in contact with the second nickel plating layer. The method for manufacturing the chromium plating component is characterized in that the second nickel plating layer has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 and the first nickel plating layer has a potential 15 mV to 150 mV lower than that of the second nickel plating layer.

[0030] (9) The method for manufacturing a chromium plating component according to (8) above, further comprising a step of forming an electrolytic chemical conversion treatment film and / or an immersion chemical conversion treatment film on the surface of the trivalent chromium plating layer.

[0031] Advantages of the Invention

[0032] The chromium plating component of the present invention exhibits excellent corrosion resistance even when the upper layer is a trivalent chromium plating layer. In particular, the corrosion of copper or a copper alloy is suppressed and the appearance is good. In addition, according to the method for manufacturing a chromium plating component of the present invention, a chromium plating component having excellent corrosion resistance and appearance can be manufactured. Description of the Drawings

[0033] Figure 1It is a cross-sectional schematic view showing an embodiment of the chromium-plated component of the present invention. Detailed Embodiment

[0034] Hereinafter, the present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments.

[0035] "Chromium-Plated Component"

[0036] The chromium-plated component of the present invention includes: a substrate having a surface layer made of copper or a copper alloy; a first nickel plating layer formed in contact with the surface layer of the substrate; a second nickel plating layer formed in contact with the first nickel plating layer; and a trivalent chromium plating layer formed in contact with the second nickel plating layer. The chromium-plated component is characterized in that the second nickel plating layer has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 and the first nickel plating layer has a potential 15 mV to 150 mV lower than that of the second nickel plating layer.

[0037] Figure 1 It is a schematic cross-sectional view showing an embodiment of the chromium-plated component of the present invention. As Figure 1 shown, in the chromium-plated component 1 of the present embodiment, a first nickel plating layer 3 is formed in contact with the surface 2A of the substrate 2, a second nickel plating layer 4 is formed on the first nickel plating layer 3, and further, a trivalent chromium plating layer 5 is formed on the upper layer thereof, and they are sequentially formed in contact with the surface of the substrate or the plating layer directly below each other. Hereinafter, each of these elements will be described.

[0038] [Substrate]

[0039] In the chromium-plated component 1, the substrate 2 is an object to be plated on which the following plating layers are formed. The substrate 2 has a surface layer 22 made of copper or a copper alloy at least on the surface 2A side where the plating layer is formed.

[0040] Specifically, the substrate 2 has a base material 21 and a surface layer 22 made of copper or a copper alloy. It should be noted that in the present embodiment, as Figure 1 shown, an example of the substrate 2 in which the base material 21 and the surface layer 22 are composed of different elements is shown, but it is not limited thereto, and the base material 21 may be made of copper or a copper alloy, and the base material 21 and the surface layer 22 may be continuous and integral.

[0041] (Base Material)

[0042] The base material 21 corresponds to the main part of the substrate 2 as an object to be plated, and there is no particular limitation on its shape and material. In Figure 1In the illustrated embodiment, each plating layer 3 to 5 is formed on one side of the flat substrate 2 having the surface layer 22 on the base material 21, but the chromium plating member of the present invention is not limited to such a manner. The base material 21 may be, for example, various-shaped handles, grilles, moldings, car emblems and other automotive parts, outboard engine parts, faucet metal fittings, building materials parts represented by door handles and window frames, home appliance parts, and other parts of any shape and use.

[0043] The base material 21 is preferably composed of one or more materials selected from the group consisting of resin, ceramic, and metal, and has a surface layer 22 made of copper or a copper alloy to form the substrate 2, but is not limited to such materials. The base material 21 may also be a composite material of various resins, elastomers, ceramics, metals, carbon materials, etc. The base material 21 may also be composed of copper or a copper alloy itself and form the substrate 2 without other essential surface layers. In this case, the surface layer of the substrate 2 is of course composed of copper or a copper alloy. It should be noted that in this article, "composed of copper or a copper alloy" means that the above surface layer is mainly composed of copper or a copper alloy, and does not exclude the inclusion of trace additives and inevitable impurities.

[0044] When the base material 21 is made of a metallic material, the composition of the metallic material is not particularly limited. Examples of the metal include, but are not limited to, copper, copper alloy, nickel, nickel alloy, iron, stainless steel, zinc, etc. In order to obtain adhesion, these metals can be appropriately subjected to activation treatment and strike plating. If copper or a copper alloy is used for strike plating or other treatments, the obtained base material 21 can be directly used as the substrate 2 in the chromium plating member 1.

[0045] The type of resin or the like constituting the base material 21 is also not particularly limited. Examples include ABS (acrylonitrile-butadiene-styrene resin), PC (polycarbonate), ABS containing PC, SBS (styrene-butadiene-styrene copolymer), acrylic resin, polyolefin resins such as polypropylene or polyethylene, polyphenylene ether, polyphenylene sulfide, polyacetal, polyamide, polyimide, polyester, polyvinyl acetate, polyurethane, epoxy resin, phenolic resin, and CFRP (carbon fiber reinforced plastic), resin containing CNF (cellulose nanofiber), etc., but are not limited to these. Among them, the base material based on ABS resin is suitable as the base material of the chromium plating member 1 because it is easy to plate and easy to form a surface layer of copper or a copper alloy.

[0046] (Plating treatment of the base material)

[0047] Preferably, a metal is used to conductivize the ceramic or resin substrate 21 as described above to facilitate plating. The method of conductivizing with a metal is not particularly limited, and various methods such as electroless plating, electroplating, sputtering of a metal, and metal evaporation can be used. Electroless plating with copper, a copper alloy, nickel, or a nickel alloy is particularly preferred. The method and conditions of electroless plating are also not particularly limited and can be carried out according to conventional methods and conditions.

[0048] Preferably, the substrate 21 that has undergone electroless plating is further subjected to electrocopper plating or electrocopper alloy plating (electrolytic copper-based plating). Through electrolytic copper-based plating, a surface layer 22 with particularly excellent adhesion can be formed. When electroless plating is carried out with copper or a copper alloy and a copper-based layer is formed, it is also preferred to overlap electrolytic copper-based plating. The method and conditions of electrolytic copper-based plating are also not particularly limited and can be carried out according to conventional methods and conditions. In this way, the surface layer 22 in the substrate 2 can be prepared.

[0049] (Surface layer)

[0050] The surface layer 22 constitutes the surface of the substrate 21 in the substrate 2 or the upper layer thereof, that is, the surface on the side where the subsequent plating layer is formed, and is composed of copper or a copper alloy. In this way, on the surface layer 22 composed of copper or a copper alloy, the subsequent plating layer, specifically the first nickel plating layer 3, is formed in contact on the surface 2A side.

[0051] [Nickel plating layer]

[0052] In the chromium plating member 1, as described above, the first nickel plating layer 3 is formed on the surface 2A of the substrate 2, the second nickel plating layer 4 is formed thereon, and further a trivalent chromium plating layer 5 is formed on the upper layer thereof. Here, the first nickel plating layer 3 and the second nickel plating layer 4 are collectively referred to as the "nickel plating layer".

[0053] In the nickel plating layer, the second nickel plating layer 4 on the side of the trivalent chromium plating layer 5 has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 When. The first nickel plating layer 3 in contact with the substrate 2 has a lower potential than the second nickel plating layer 4. That is, in the chromium plating member 1, the first nickel plating layer 3 with a low potential is formed in contact with the surface layer 22 without being separated by other layers such as a semi-bright nickel layer with a high potential directly above the substrate 2.

[0054] The following will describe these nickel plating layers in detail. First, the second nickel plating layer 4 whose potential value range is specified and its potential will be described.

[0055] [Second nickel plating layer]

[0056] The second nickel plating layer 4 is at a current density of 0.1 mA / cm 2A nickel plating layer having an anodic potential of -215 mV to -290 mV. Further, from the viewpoint of further improving the corrosion resistance of the chromium plating member 1, the anodic potential is preferably -220 mV to -285 mV, more preferably -220 mV to -280 mV.

[0057] The anodic potential is the potential that serves as a reference for the equilibrium potential and clearly indicates the high and low relationship of the potential. Regarding the anodic potential, for example, a specimen (specimen for potential measurement) from which the chromium plating layer 5 has been removed from the chromium plating member 1 can be used as the working electrode, and it can be measured by chronopotentiometry. Specifically, platinum is used as the counter electrode, a silver-silver chloride (saturated KCl) electrode is used as the reference electrode, and nickel chloride hexahydrate 300 g / L, sodium chloride 50 g / L, and boric acid 25 g / L are used as the electrolyte, and the voltage is measured by chronopotentiometry. The voltage value of the working electrode when the current density is 0.1 mA / cm 2 is taken as the "anodic potential" of the second nickel plating layer 4.

[0058] The high and low relationship of the potential is usually evaluated by the equilibrium potential described later, but the present inventors have found this time that the anodic potential reflects the high and low relationship of the potential several times more sensitively than the equilibrium potential. In addition, the anodic potential also has the advantage of being able to be measured by a simpler method than the equilibrium potential. Therefore, as described above, the potential of the second nickel plating layer 4 is defined by the anodic potential to manage the physical properties of the chromium plating member 1.

[0059] It should be noted that the above anodic potential of the nickel plating layer varies depending on conditions such as the type of plating. Generally, the average bright nickel plating layer is about -250 mV, the top layer of the three-layer nickel plating in the general nickel-chromium plating (for example, the eutectoid nickel plating layer) is a value on the higher potential side, and the average semi-bright nickel plating layer is a value of about -150 mV on the higher potential side. Therefore, the second nickel plating layer 4 can be composed of, for example, a general bright nickel plating layer, or a satin nickel plating layer having an equivalent potential, and a nickel plating layer whose potential is adjusted to the lower or higher potential side with a potential regulator.

[0060] (Equilibrium potential)

[0061] The equilibrium potential of the second nickel plating layer 4 having the above-described anodic potential is approximately in the range of -402 mV to -414 mV. The equilibrium potential can be measured, for example, using platinum as the counter electrode, a silver-silver chloride (saturated KCl) electrode as the reference electrode, and a liquid containing nickel chloride hexahydrate 300 g / L, sodium chloride 50 g / L, and boric acid 25 g / L as the electrolyte. For example, a specimen (specimen for potential measurement) from which the chromium plating layer 5 has been removed from the chromium plating member 1 is used as the working electrode, and by chronopotentiometry, the current density is set to 0.01, 0.1, 1, -0.01, -0.1, and -1 mA / cm2 Make a Tafel plot using the voltage value at that time, and the equilibrium potential can be obtained from this.

[0062] (Bright nickel plating layer)

[0063] The bright nickel plating layer, which is one of the representative examples of the second nickel plating layer 4, contains sulfur in the nickel plating film. The type of the bright nickel plating layer is not particularly limited.

[0064] The bright nickel plating layer can be formed by electroplating using a known nickel plating solution containing a primary brightener composed of a sulfur compound or the like. Specifically, the nickel plating solution is not particularly limited, and for example, a Watts bath, a sulfamic acid bath, a citric acid bath, a Weisberg bath, etc. can be used.

[0065] In addition, as the primary brightener contained in the nickel plating solution for forming the bright nickel plating layer, for example, aromatic sulfonimides such as sodium 1,5-naphthalenedisulfonate, sodium 1,6-naphthalenedisulfonate, sodium 2,5-naphthalenedisulfonate, sodium 1,3,6-naphthalenetrisulfonate, sodium benzenesulfonate, sodium benzenesulfinate, sodium o-benzoylbenzenesulfimide (saccharin), sulfinic acids, vinylsulfonic acid sodium salts, allylsulfonic acid sodium salts and other vinyl-based unsaturated sulfonates can be cited. One kind or a combination of two or more kinds of them can be used.

[0066] In addition, a brightening / leveling agent (secondary brightener) for the purpose of imparting brightness / leveling can be used together with or instead of the primary brightener. As the brightening / leveling agent, for example, acetylene-based unsaturated alcohols such as 1,4-butyne diol, hexynediol, propynol and their derivatives, pyridine-based sulfonic acid sodium salts, etc. can be cited. One kind or a combination of two or more kinds of them can also be used.

[0067] It should be noted that as the primary brightener and the brightening / leveling agent (secondary brightener), commercially available products such as #81, #83, #810, etc. used in the HI-BRITE#88 process (manufactured by JCU Co., Ltd.) can also be used.

[0068] In the nickel plating solution, the above-mentioned primary brightener is contained at a concentration of, for example, 0.1 g / L to 10 g / L, preferably 1 g / L to 5 g / L, more preferably 1.5 g / L to 4 g / L. In addition, in the nickel plating solution, the brightening / leveling agent is contained at a concentration of, for example, 0.5 ppm to 300 ppm, preferably 10 ppm to 200 ppm, more preferably 20 ppm to 200 ppm.

[0069] The plating solution for bright nickel plating preferably contains a wetting agent. Examples of the wetting agent include surfactants. The surfactants are not particularly limited, and examples thereof include nonionic surfactants such as polyethylene glycol and anionic surfactants such as sodium polyoxyethylene alkyl ether sulfate. These surfactants can be used singly or in combination of two or more. It should be noted that as the wetting agent, commercially available products such as #82, #82-A, and #82-K used in the HI-BRITE#88 process (manufactured by JCU Co., Ltd.) can be used. The above-mentioned wetting agent is contained in the nickel plating solution at a concentration of, for example, 10 ppm to 1000 ppm, more preferably 100 ppm to 500 ppm.

[0070] There are no particular limitations on the conditions for electroplating used to form the bright nickel plating layer, and conventional conditions can be employed. For example, the bath temperature can be 40°C to 60°C, more preferably 45°C to 55°C, and the current density can be 1 A / dm 2 ~10 A / dm 2 、more preferably 2 A / dm 2 ~5 A / dm 2 under these conditions.

[0071] The bright nickel plating layer thus prepared can be formed as the second nickel plating layer 4 on the first nickel plating layer. By adjusting the amounts of the primary brightener, brightening / leveling agent (secondary brightener), and temperature in the plating solution, the anodic potential of the bright nickel plating layer can be shifted to the lower potential side or the higher potential side within the range of -215 mV to -290 mV. The potential adjustment of the bright nickel plating layer can also be carried out by mixing a potential regulator.

[0072] (Potential regulator)

[0073] As the potential regulator contained in the nickel plating solution, known potential regulators can also be used. Examples include low-potential side potential regulators such as sodium saccharin, sodium benzenesulfinate, S-ethylisothiouronium hydrobromide, 3-[[amino(imino)methyl]thio]propionic acid, 2,4-thiazolidinedione, 5-chloro-2-methyl-4-isothiazolin-3-one, and 2-methyl-4-isothiazolin-3-one; and high-potential side potential regulators such as butynediol, hexynediol, propargyl alcohol, allyl sodium sulfate, formalin, chloral hydrate (2,2,2-trichloro-1,1-ethanediol), and tribromoacetaldehyde hydrate (2,2,2-tribromo-1,1-ethanediol), but are not limited thereto.

[0074] It should be noted that as the potential regulator, commercially available products such as TRI-STRIKE as the low-potential side potential regulator and ADDITIVE-E as the high-potential side potential regulator (both manufactured by JCU Co., Ltd.) can also be used.

[0075] By performing plating treatment using a nickel plating solution in which the concentrations of a primary brightener, a secondary brightener, a potential regulator, etc. are appropriately adjusted, a second nickel plating layer 4 having the potential as described above can be formed. Of course, a plating solution other than a bright nickel plating solution can also be used to form the second nickel plating layer 4 having an anode potential of -215 mV to -290 mV. For example, the second nickel plating layer 4 can also be formed by satin nickel plating described below. The plating at this time can be performed under the same conditions as the above-described bright nickel plating.

[0076] (Satin nickel plating layer)

[0077] Satin nickel plating refers to a plating method in which fine uneven shapes are formed on the surface of a plating film, thereby obtaining a semi-bright and non-bright pear-skin-like appearance. An emulsion is formed by adding various surfactants to a nickel plating bath, and adsorption and detachment from the film surface are repeated. At the site where the emulsion is adsorbed, the precipitation of the film is hindered, and after detachment, a concave shape is formed on the surface layer of the film, thereby enabling a pear-skin-like appearance to be obtained. As the surfactant, for example, cationic surfactants and anionic surfactants can be mentioned, but are not limited to these. In this way, a satin nickel plating layer can be manufactured by using a nickel plating solution in which these surfactants are dispersed. It can also be formed by containing non-conductive fine particles such as silica, kaolin, and barium sulfate in the plating solution. Such satin nickel plating is useful in manufacturing the chromium plating component 1 having a pear-skin-like appearance.

[0078] The satin nickel plating layer can also be formed using commercially available products such as the DOUBLET SATIN Process (manufactured by JCU Corporation).

[0079] It should be noted that as the nickel plating solution, a nickel plating solution not containing non-conductive fine particles such as silica is preferably used to form a second nickel plating layer 4 not containing non-conductive fine particles. In addition, when non-conductive fine particles are included, the content is also preferably about 5% by mass or less, particularly preferably 1% by mass or less, relative to the total mass of the second nickel plating layer 4. By forming a second nickel plating layer 4 that does not contain non-conductive fine particles or contains non-conductive fine particles to an extent of 5% by mass or less, precipitation of such fine particles can be prevented, and the appearance of the chromium plating component 1 can be made better. In addition, by using a nickel plating solution not containing non-conductive fine particles in the plating treatment, the management of the plating solution becomes easy, and there is also an advantage that the plating process can be simplified. It should be noted that in the present invention, "not containing non-conductive fine particles" means "not containing non-conductive fine particles other than unavoidable impurities". It does not only refer to the case where the amount of non-conductive fine particles is 0, and for example, it also includes a layer in which non-conductive fine particles are mixed in an amount of 0.1% by mass or less.

[0080] As described above, a second nickel plating layer having a lower potential than the uppermost nickel plating layer in a conventional nickel-chromium plating member having a three-layer nickel plating layer is formed on the first nickel plating layer 3.

[0081] [The first nickel plating layer]

[0082] The first nickel plating layer 3 is a nickel plating layer having a potential 15 mV to 150 mV lower than that of the second nickel plating layer 4. In a conventional nickel-chromium plating member, it has a considerably lower potential than a semi-bright nickel plating layer that is often used as the plating layer directly above the substrate.

[0083] The first nickel plating layer 3 can be prepared, for example, using a plating solution in which the types and contents of the primary brightener, brightening / leveling agent (secondary brightener), and potential regulator in the above-mentioned bright nickel plating solution are changed. Alternatively, it can be prepared using a commercially available low-potential nickel plating solution such as the TRI-STRIKE process (manufactured by JCU Corporation).

[0084] In addition, the conditions for electroplating used to form the first nickel plating layer 3 are not particularly limited, and conventional conditions can be employed. For example, it can be carried out under the conditions of a bath temperature of 40°C to 60°C, more preferably 45°C to 55°C, and a current density of 1 A / dm 2 to 10 A / dm 2 , more preferably 2 A / dm 2 to 5 A / dm 2 .

[0085] (Measurement of potential difference and potential)

[0086] As described above, the first nickel plating layer 3 has a potential 15 mV to 150 mV lower than that of the second nickel plating layer 4. From the viewpoint of further improving the corrosion resistance of the chromium plating member 1, it preferably has a potential 30 mV to 150 mV lower than that of the second nickel plating layer 4, more preferably 40 mV to 140 mV lower, further preferably 50 mV to 120 mV lower, and particularly preferably 70 mV to 100 mV lower.

[0087] Such a potential difference can be measured, for example, by the STEP test in accordance with ASTM B764: "Simultaneous Determination of the Thickness and Potential of Each Layer in Multilayer Nickel Deposits". More specifically, a silver-silver chloride reference electrode (reference electrode) and a specimen obtained by removing the trivalent chromium plating layer 5 from the chromium-plated component 1 (specimen for potential difference measurement) can be placed in an electrolytic solution (20 °C) containing 300 g / L of NiCl2·6H2O, 50 g / L of NaCl, and 25 g / L of H3BO3, and the measurement can be carried out using a commercially available device such as a multilayer nickel plating corrosion resistance measurement device. It should be noted that the measurement conditions for the potential difference here are different from those for the anodic potential and equilibrium potential described above. Therefore, for example, the anodic potential or equilibrium potential of the first nickel plating layer 3 cannot be obtained by subtracting this potential difference from the anodic potential or equilibrium potential of the second nickel plating layer 4.

[0088] In the chromium-plated component 1, as described above, the first nickel plating layer 3 is formed directly above the surface layer 22 in the substrate 2, the second nickel plating layer 4 is formed directly above it and on the side of the chromium plating layer 5, and the second nickel plating layer 4 has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 and the first nickel plating layer 3 has a potential 15 mV to 150 mV lower than that of the second nickel plating layer 4. According to such a chromium-plated component 1, excellent corrosion resistance and good appearance are exhibited.

[0089] In the chromium-plated component 1, the reason for achieving the above effects is not yet determined and is not limited by a specific theory. However, as one of the reasons, since the potential of the first nickel plating layer 3 is low, the corrosion of the adjacent surface layer 22 made of copper or a copper alloy is effectively suppressed, and it is difficult to generate voids or the like. As a result, it is possible to also suppress the generation of swelling near the plating layer. At the same time, it is considered that since the second nickel plating layer 4 is inhibited from sacrificial corrosion by the first nickel plating layer 3 with a lower potential, the overall corrosion resistance of the chromium-plated component 1 is improved.

[0090] [Film Thickness and Film Thickness Ratio of Nickel Plating Layer]

[0091] In the chromium-plated component 1, the film thicknesses of the first nickel plating layer 3 and the second nickel plating layer 4 constituting the nickel plating layer are not particularly limited and can be set, for example, to 100 μm or less, or in the range of 1 μm to 50 μm according to the purpose. In addition, from the viewpoint of making the corrosion resistance more excellent and reducing the nickel plating cost, the total film thickness (nickel film thickness) of the first nickel plating layer 3 and the second nickel plating layer 4 is preferably in the range of 1 μm to 30 μm, more preferably in the range of 2 μm to 20 μm, and particularly preferably in the range of 5 μm to 15 μm.

[0092] In addition, the film thickness ratio of the first nickel plating layer 3 to the second nickel plating layer 4 is preferably in the range of 1:10 to 30:1, more preferably in the range of 1:4 to 14:1. Thereby, there is a tendency to exhibit more excellent corrosion resistance. In addition, by making the film thickness ratio in the range of 1:4 to 4:1, particularly in the range of 1:2 to 4:1, the corrosion resistance of the chromium plating member 1 can become more remarkable.

[0093] [Trivalent chromium plating layer]

[0094] In the chromium plating member 1, a trivalent chromium plating layer 5 is formed in contact with the second nickel plating layer 4. By means of this trivalent chromium plating layer 5, a plating member having excellent corrosion resistance and aesthetic decorativeness and useful for decorative purposes or the like can be provided.

[0095] There is no particular limitation on the method for forming the trivalent chromium plating layer 5 either, and it can be processed under desired conditions by a conventional plating method. For example, it can be formed by electroplating treatment using a known trivalent chromium plating solution containing a trivalent chromium compound, a complexing agent, a conductive salt, a pH buffer, etc.

[0096] In the trivalent chromium plating solution for forming the trivalent chromium plating layer 5, the trivalent chromium compound is not particularly limited. Examples thereof include basic chromium(III) sulfate (Cr(OH)SO4), chromium(III) sulfate, chromium(III) chloride, chromium(III) sulfamate, chromium(III) acetate, etc. Among them, it is preferable to use basic chromium sulfate and / or chromium sulfate. These trivalent chromium compounds can be one kind or a combination of two or more kinds. In addition, the content of the trivalent chromium compound in the trivalent chromium plating solution can be, for example, on the order of 1 g / L to 25 g / L in terms of metallic chromium.

[0097] In addition, there is no particular limitation on the complexing agent either. Examples thereof include aliphatic monocarboxylic acids (salts) such as formic acid, ammonium formate, potassium formate; aliphatic dicarboxylic acids and their salts such as succinic acid, maleic acid, malic acid; aliphatic tricarboxylic acids (salts) such as citric acid, ammonium citrate; carboxylic acids (salts) having two or more hydroxyl groups and two or more carboxyl groups such as tartaric acid, diammonium tartrate, sodium tartrate; amino carboxylic acids such as glycine, etc. These complexing agents can be one kind or a combination of two or more kinds. The content of the complexing agent in the trivalent chromium plating solution can be, for example, on the order of 0.1 g / L to 50 g / L.

[0098] In addition, there is no particular limitation on the conductive salt either. Examples thereof include sulfates such as potassium sulfate, ammonium sulfate, sodium sulfate; chlorides such as potassium chloride, ammonium chloride, sodium chloride; sulfamates such as potassium sulfamate, ammonium sulfamate, sodium sulfamate, etc. These conductive salts can be one kind or a combination of two or more kinds. The content of the conductive salt in the trivalent chromium plating solution can be, for example, on the order of 100 g / L to 500 g / L.

[0099] In addition, there is no particular limitation on the pH buffer. Examples thereof include boric acid, sodium borate, potassium borate, phosphoric acid, dipotassium hydrogen phosphate, etc. These pH buffers may be used alone or in combination of two or more. The content of the pH buffer in the trivalent chromium plating solution may be, for example, on the order of 25 g / L to 200 g / L.

[0100] The trivalent chromium plating solution may further contain blackening agents such as sodium thiocyanate, methionine, cysteine, tin salts such as ascorbic acid, sodium ascorbate, hydrogen peroxide, polyethylene glycol, stannous sulfate, stannous chloride, iron chloride, sodium saccharin, sodium allylsulfonate, sodium vinylsulfonate, etc.

[0101] As the trivalent chromium plating solution containing the above complexing agent, conductive salt, and pH buffer, commercially available products such as JCUTRICHROM JTC series (manufactured by JCU Co., Ltd.), TOPFINECHROME series (manufactured by Okuno Pharmaceutical Co., Ltd.), ASUSCHROME series (manufactured by SurTec), TriChrome series (manufactured by Atotech), Envirochrome process, Twilite process (both manufactured by Macdermid), etc. can be used. The chromium plating layer usually has a silver-white appearance, but a black plating layer can also be formed by mixing, for example, the above blackening agent in the plating solution.

[0102] There is no particular limitation on the conditions for electroplating used to form the trivalent chromium plating layer 5, and conventional conditions can be adopted. For example, it can be carried out under the conditions that the bath temperature is 30°C to 60°C, carbon or iridium oxide is used as the anode, and the cathode current density is 5 A / dm 2 ~20 A / dm 2 .

[0103] In the chromium-plated component 1, as shown in the following examples, regardless of the type and film thickness of the trivalent chromium plating layer 5, excellent corrosion resistance and good appearance are exhibited. Therefore, the film thickness of the trivalent chromium plating layer 5 is not particularly limited. For example, it can be 0.05 μm or more, specifically 0.1 μm to 1.0 μm, particularly 0.15 μm to 0.50 μm, which is the general plating layer thickness in chromium-plated products.

[0104] [Electrolytic conversion treatment, immersion conversion treatment]

[0105] The chromium-plated component 1 preferably further has an electrolytic conversion treatment film and / or an immersion conversion treatment film on the trivalent chromium plating layer 5 described above. Thereby, the corrosion resistance of the chromium-plated component 1 may be further improved. The electrolytic conversion treatment and the immersion conversion treatment performed on the surface of the trivalent chromium plating layer 5 are not particularly limited, and conventional treatment methods can be applied according to the desire. As examples, there may be mentioned chromate treatment, wax treatment, treatment with a solution such as benzotriazole or triazinethiol, treatment with a solution of a compound having an amino group or an imino group, and heat treatment, etc., but are not limited thereto. By such post-treatment, the corrosion resistance of the chromium-plated component can be further improved, or discoloration or hydrogen embrittlement, etc. can be more effectively prevented.

[0106] (Chromate treatment)

[0107] In the electrolytic conversion treatment or the immersion conversion treatment, it is more preferable to perform a treatment containing hexavalent chromium ions, so-called chromate treatment. Since the chromate coating film has self-healing properties, the corrosion resistance of the chromium-plated component 1 can be further improved.

[0108] As the chromate treatment, there may be mentioned, for example, known electrolytic conversion treatments or immersion conversion treatments using hexavalent chromium ions such as chromic anhydride and dichromate. The electrolytic conversion treatment can be performed by a conventional method. For example, commercially available processes such as the EBACHRO-500 process and the EBACHRO-900 process (manufactured by JCU Corporation) and the treatment agents used therein can be used. In addition, instead of the chromate treatment, a conversion treatment containing trivalent chromium ions or a chromium-free conversion coating treatment using metals such as molybdenum, vanadium, phosphoric acid, permanganic acid, and iron can be used.

[0109] [Chromium-plated component and its uses]

[0110] The chromium-plated component 1 exhibits excellent corrosion resistance even when the upper layer is the trivalent chromium plating layer 5, and has a good appearance. The chromium-plated component 1 shows a high evaluation result with a rating number (R.N.) of approximately 9 or more, for example, 9.3 or more, in the CASS test, which is a corrosion resistance evaluation method based on JIS H8502. Therefore, the chromium-plated component 1 can be used as various components such as automotive components, outboard engine components, faucet metal fittings, building materials components, and home appliance components.

[0111] [Manufacturing method of chromium-plated component]

[0112] As described above, the chromium-plated component 1 can be manufactured by the following method for manufacturing a chromium-plated component, which method has the following steps: on a substrate 2 having a surface layer 22 made of copper or a copper alloy, a first nickel plating layer 3 is formed in contact on the surface layer; a second nickel plating layer 4 is formed in contact on the first nickel plating layer 3; and a trivalent chromium plating layer 5 is formed in contact on the second nickel plating layer 4. The manufacturing method is characterized in that the second nickel plating layer 4 has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 and the first nickel plating layer 3 has a potential 15 mV to 150 mV lower than that of the second nickel plating layer 4.

[0113] Each of the steps of forming the first nickel plating layer 3, the second nickel plating layer 4, and the trivalent chromium plating layer 5 can be carried out using the methods and conditions described in the description of each plating layer. An electrolytic chemical conversion treatment film and / or an immersion chemical conversion treatment film as described above can be further formed on the surface of the trivalent chromium plating layer 5. In the manufacturing method of the chromium-plated component 1, only two nickel plating layers can be formed, so that manufacturing can also be carried out with fewer steps.

[0114] Examples

[0115] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by any of these descriptions.

[0116] <<Example 1>>

[0117] A chromium-plated component according to the present invention was manufactured as follows.

[0118] (Preparation of Substrate)

[0119] After the entire surface of an ABS resin molded product (shape: flat plate) was etched with chromic acid, reduction treatment, catalysis, and activation were carried out according to a conventional method, and then electroless nickel plating was carried out. For chromic acid etching, a treatment solution containing 400 g / L of chromic anhydride, 400 g / L of sulfuric acid, and 10 g / L of trivalent chromium was used. For electroless nickel plating, the ENILEX NI-5 process (manufactured by JCU Corporation) was used at 40°C. Then, electrolytic copper plating was carried out using the CU-BRITE EP-30 process (manufactured by JCU Corporation) at room temperature and 3 A / dm 2 under the condition of to prepare a substrate.

[0120] (First Nickel Plating)

[0121] The substrate obtained above was immersed in a first nickel plating solution, and a first nickel plating layer having a thickness of 6 μm was formed under the conditions of 50°C, 3 A / dm 2 , and 15 minutes. As the first nickel plating solution, the following low-potential nickel plating base solution was directly used.

[0122] <Low-potential nickel plating bath>[

[0123] · Watts bath

[0124] Nickel sulfate 260 g / L

[0125] Nickel chloride 40 g / L

[0126] Boric acid 40 g / L

[0127] · TRI-STRIKE process (manufactured by JCU Co., Ltd.)

[0128] TRI-STRIKE 3 ml / L

[0129] #82 (wetting agent) 2 ml / L

[0130] (Second nickel plating)

[0131] Next, immerse in the following second nickel plating bath and form a second nickel plating layer with a thickness of 6 μm under the conditions of 50 °C, 3 A / dm 2 , 15 minutes (total film thickness of the first nickel plating layer and the second nickel plating layer = 12 μm, thickness ratio of the first nickel plating layer: second nickel plating layer = 1:1). As the second nickel plating bath, use a liquid in which TRI-STRIKE (manufactured by JCU Co., Ltd.) is mixed in an amount of 1 ml / L as a potential regulator in the bright nickel plating bath as described below. The second nickel plating layer thus prepared has a potential lower than that of the average bright nickel plating layer, and the potential difference with respect to the first nickel plating layer is adjusted to +60 mV (the potential of the first nickel plating layer is 60 mV lower than that of the second nickel plating layer).

[0132] <Bright nickel plating bath>[

[0133] · Watts bath

[0134] Nickel sulfate 260 g / L

[0135] Nickel chloride 40 g / L

[0136] Boric acid 40 g / L

[0137] · HI-BRITE #88 process (manufactured by JCU Co., Ltd.)

[0138] #810 (secondary brightener) 3 ml / L

[0139] #82 (wetting agent) 2 ml / L

[0140] #83 (primary brightener) 10 ml / L

[0141] (Trivalent chromium plating)

[0142] Next, it was immersed in the following trivalent chromium plating solution, and a white trivalent chromium plating layer was formed in contact with the above-mentioned second nickel plating layer under the conditions of 55 °C and 10 A / dm 2 ² for 4 minutes. The obtained chromium-plated component specimen had a good appearance.

[0143] <Trivalent chromium plating solution>

[0144]

[0145] For the chromium-plated component specimen obtained as described above, the appearance was evaluated, and the film thickness and the like were measured to conduct a corrosion resistance evaluation test. The test method is as follows. The test results are shown in Table 1 described later.

[0146] (Film thickness measurement)

[0147] · The film thickness of each nickel plating layer was measured from the cross-sectional microscope photograph.

[0148] · The film thickness of the chromium plating layer (Cr film thickness) was measured using the fluorescence X-ray analyzer "FT-150H" manufactured by Hitachi High-Technologies Corporation.

[0149] (Anodic potential measurement)

[0150] The chromium-plated component specimen was immersed in 1:1 hydrochloric acid to remove the chromium plating layer, and then masked to produce a specimen (specimen for potential measurement) in which the second nickel plating layer was exposed on the surface in a circular shape with a diameter of 6 mm. Using this specimen for potential measurement as the working electrode, platinum as the counter electrode, and a silver-silver chloride (saturated KCl) electrode as the reference electrode, the voltage was measured by chronopotentiometry. As the electrolyte, an aqueous solution with a pH of 2.75 containing 300 g / L of nickel chloride hexahydrate, 50 g / L of sodium chloride, and 25 g / L of boric acid was used. Using the HZ-7000 manufactured by Hokuto Denko Corporation as the device, the measurement was carried out under the conditions of 25 °C, 600 seconds, and without stirring. The measurement was performed n = 3 times, and the average value was adopted.

[0151] · The current density was set to 0.1 mA / cm 2 ², and the voltage value of the working electrode when the voltage was stable was set as the "anodic potential" of the second nickel plating layer.

[0152] It should be noted that, similarly, the current density was set to 0.01, 0.1, 1, -0.01, -0.1, and -1 mA / cm 2 ², and a Tafel curve was made from the voltage value of the working electrode when the voltage was stable to obtain the equilibrium potential. As a result, when the anodic potential of the second nickel plating layer was -215 mV to -290 mV, the equilibrium potential was -402 mV to -414 mV.

[0153] (Measurement of potential difference)

[0154] The potential difference between the first nickel plating layer and the second nickel plating layer is measured by the STEP test in accordance with ASTM B764: "Simultaneous determination of the thickness and potential of each layer in multilayer nickel deposits". Before the measurement, an electrolytic solution (20 °C) containing 300 g / L of NiCl2·6H2O, 50 g / L of NaCl, and 25 g / L of H3BO3 is prepared. The sample for measuring the potential difference is prepared in this electrolytic solution, and the measurement is carried out using the multilayer nickel plating corrosion resistance measuring device "ED-3" manufactured by Chuo Seisakusho Co., Ltd. with a silver-silver chloride electrode as the reference electrode.

[0155] (Evaluation of corrosion resistance)

[0156] The corrosion resistance is evaluated by the CASS test according to JIS H8502. An aqueous solution containing 50 ± 5 g / L of sodium chloride and 0.26 ± 0.02 g / L of copper chloride (CuCl2·2H2O) and adjusted to a pH of 3.0 - 3.2 with acetic acid is sprayed onto a 65 × 50 mm sample under the following conditions, and the rating number (R.N.) after 80 hours is measured.

[0157] · Spray volume: 1.5 ± 0.5 ml / 80 cm 2 / h

[0158] · Temperature inside the test chamber: 50 ± 2 °C

[0159] · Temperature of the brine tank: 50 ± 2 °C

[0160] · Temperature of the air saturator: 63 ± 2 °C

[0161] · Compressed air pressure: 70 kPa - 167 kPa

[0162] Visually observe the appearance of the sample after the above CASS test, and evaluate it according to the number and ratio of bulges (voids in the inner plating layer) according to the following criteria.

[0163] 5: No bulge

[0164] 4: Five or fewer bulges

[0165] 3: The area with bulges is less than half of the sample surface, but six or more bulges are generated.

[0166] 2: Although there are parts without bulges, bulges are generated in more than half of the sample surface area.

[0167] 1: Bulges are generated on the entire surface of the sample

[0168] 《Example 2》

[0169] The surface layer of the chromium-plated component specimen obtained by the same operation as in Example 1 was further subjected to electrolytic chromate treatment. The electrolytic chromate treatment was carried out using the EBACHRO-500 process (a hexavalent chromium-based treatment solution containing 100 ml / L of ECR-500 manufactured by JCU Co., Ltd.) at 40 °C and 0.1 A / dm 2 ² for 1 minute. The obtained chromium-plated component specimen had a good appearance. For this specimen, tests were carried out in the same manner as in Example 1, and the results are shown in Table 1 described later.

[0170] 《Examples 3 to 8, Comparative Examples 1 to 4》

[0171] Except for changing the mixing ratio of the first nickel plating solution and the second nickel plating solution, the same operations as in Example 1 or 2 were carried out. As the first nickel plating solution, a liquid in which TRI-STRIKE (manufactured by JCU Co., Ltd.) was mixed in an amount of 1 to 5 ml / L in the above bright nickel plating base solution to lower the potential (Examples 3 to 8), and a liquid in which ADDITIVE-E (manufactured by JCU Co., Ltd.) was mixed in an amount of 0 to 0.1 ml / L to raise the potential (Comparative Examples 1 to 4) were used. As the second nickel plating solution, the above bright nickel plating base solution (Examples 3 to 6), and a liquid in which ADDITIVE-E (manufactured by JCU Co., Ltd.) was mixed in an amount of 0.1 to 1 ml / L to raise the potential (Examples 7 to 8, Comparative Examples 1 to 4) were used.

[0172] The potential difference of the second nickel plating layer prepared in these examples and comparative examples was adjusted to +60 mV with respect to the first nickel plating layer (the potential of the first nickel plating layer was 60 mV lower than that of the second nickel plating layer), and it had a higher potential than the second nickel plating layer in Examples 1 to 2. The appearance of the obtained chromium-plated component specimens just after production was good. The test results of these specimens are shown in Table 1 described later.

[0173] 《Comparative Example 5》

[0174] In the same manner as the chromium-plated component described in Patent Document 4, a specimen having a three-layer structure of a nickel plating layer was manufactured under the following conditions, and evaluation was carried out in the same manner as in Example 1.

[0175] (Semi-bright nickel plating)

[0176] The substrate prepared in the same manner as in Example 1 was immersed in the following semi-bright nickel plating solution, and a semi-bright nickel plating layer was formed under the conditions of 55 °C, 3 A / dm 2 ² for 15 minutes.

[0177] <Semi-bright nickel plating solution>

[0178] · Watts bath

[0179] Nickel sulfate 260 g / L

[0180] Nickel chloride 40 g / L

[0181] Boric acid 40 g / L

[0182] ·CF-24T process (manufactured by JCU Co., Ltd.)

[0183] CF-24T 1 ml / L

[0184] #82-K (wetting agent) 1 ml / L

[0185] (Bright nickel plating)

[0186] Next, immerse it in the above-mentioned bright nickel plating bath, and form a bright nickel plating layer under the conditions of 50 °C, 3 A / dm 2 , and 12 minutes. The bright nickel plating layer has a potential 145 mV lower than that of the underlying semi-bright nickel plating layer.

[0187] (MP nickel plating)

[0188] Furthermore, immerse it in the following MP nickel plating solution, and form an MP nickel plating layer under the conditions of 55 °C, 3 A / dm 2 , and 3 minutes. The MP nickel plating layer has a potential 55 mV higher than that of the underlying bright nickel plating layer. In addition, the film thickness ratio of the semi-bright nickel plating layer: bright nickel plating layer: MP nickel plating layer is 5:4:1.

[0189] <MP nickel plating solution>

[0190] · Watts bath

[0191] Nickel sulfate 260 g / L

[0192] Nickel chloride 40 g / L

[0193] Boric acid 40 g / L

[0194] · MP-NI308 process (manufactured by JCU Co., Ltd.)

[0195]

[0196]

[0197] (Preparation of chromium-plated component specimens)

[0198] Next, perform trivalent chromium plating under the same conditions as in Example 1 to prepare chromium-plated component specimens and evaluate their physical properties. The evaluation results are shown in Table 1 described later.

[0199] <<Comparative Example 6>>

[0200] Prepare a sample in which the nickel plating layer (lower layer) on the substrate side in the two-layer nickel plating layer is at a high potential. The substrate prepared in the same manner as in Example 1 was successively subjected to semi-bright nickel plating, bright nickel plating, and trivalent chromium plating to prepare a chromium plating component sample, and a physical property test was conducted. It should be noted that each plating treatment was carried out under the same conditions as in Comparative Examples 1 and 5, etc., but the plating time of the bright nickel plating was 15 minutes. In addition, in the chromium plating component sample of this comparative example, the semi-bright nickel plating layer in the lower layer had a potential 145 mV higher than that of the bright nickel plating layer in the upper layer. The test results of the obtained chromium plating component sample are shown in Table 1.

[0201] [Table 1]

[0202]

[0203] *Potential difference of the lower nickel plating layer relative to the upper nickel plating layer

[0204] ※Potential difference relative to the central bright nickel plating layer: lower layer +145 mV, upper layer +55 mV

[0205] The rating numbers (R.N.) of the chromium plating component samples of Examples 1 to 8 and Comparative Examples 1 to 4 having the first nickel plating layer with a potential 60 mV lower than that of the second nickel plating layer on the substrate side were all 9.0 or more in the CASS test, which was superior to the samples of Comparative Example 5 having a three-layer nickel plating layer structure. It implies the importance of making the nickel plating layer on the substrate side at a low potential. Among them, according to the present invention, it is known that the chromium plating component samples of Examples 1 to 8 in which the anode potential of the second nickel plating layer is in the range of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 showed the highest values in the swelling evaluation results, and the overall corrosion resistance was excellent. In addition, according to the present invention, it is known that although the nickel plating process has one less process than the usual nickel-chromium plating, it is also possible to manufacture a chromium plating component with extremely excellent corrosion resistance.

[0206] On the other hand, in Comparative Examples 1 to 4 in which the anode potential of the second nickel plating layer was outside the range specified by the present invention, swelling occurred on the entire surface of the sample after the CASS test. It can be seen that in order to suppress swelling, it is necessary to control the potential of the second nickel plating layer (upper nickel plating layer) within a specific range. In addition, in the sample of Comparative Example 6 in which the nickel plating layer on the lower layer side was at a higher potential than the upper layer side, the R.N. decreased. It was shown again that in improving the corrosion resistance of the chromium plating component, it is important to make the nickel plating layer on the substrate side at a lower potential.

[0207] It should be noted that in the specimens of Examples 5 to 6, compared with the specimens of Examples 3 to 4 under the same conditions, the film thickness of the chromium plating layer is more than 3 times, but the CASS test results are the same. It is implied that the chromium-plated components of the present invention exhibit excellent corrosion resistance regardless of the film thickness of the trivalent chromium plating layer. In addition, in the specimens of the chromium-plated components of Examples 1 to 8, even when the nickel film thickness is 12 μm, the R.N. value is 9.0 or more, which is the same as or higher than that of the chromium-plated components with a nickel film thickness of 25 μm described later. Although the nickel film thickness is less than half, the same corrosion resistance is still exhibited, indicating that the corrosion resistance can be improved without using a large amount of nickel by the present invention. That is, according to the manufacturing method of the present invention, the amount of nickel used can be reduced, so the nickel plating process can also be carried out in a shorter time and at a lower cost.

[0208] 《Examples 9 to 18》

[0209] Except for changing the ratio of the first nickel plating solution, the same operations as in Example 7 or 8 were carried out. As the first nickel plating solution, a liquid in which TRI-STRIKE (manufactured by JCU Co., Ltd.) was mixed in an amount of 0 to 5 ml / L was used in the above bright nickel plating base solution (Examples 9 to 14) or low-potential nickel plating base solution (Examples 15 to 18). In Examples 9 and 10, the bath temperature was set to 60 °C, and the potential difference between the first nickel plating layer and the second nickel plating layer was adjusted. The obtained chromium-plated component specimens all showed good appearance. The test results of these specimens are shown in Table 2 described later.

[0210] 《Comparative Example 7》

[0211] Using the above bright nickel plating base solution as the first nickel plating solution and the above low-potential nickel plating base solution as the second nickel plating solution, the same operations as in Example 3 were carried out except for this. The test results of the obtained chromium-plated component specimens are shown in Table 2 described later.

[0212] 《Comparative Example 8》

[0213] Except for raising the bath temperature of the first nickel plating solution to 52 °C, the same operations as in Example 3 were carried out. The test results of the obtained chromium-plated component specimens are shown in Table 2 described later.

[0214] 《Comparative Example 9》

[0215] For reference, a hexavalent chromium-plated component was also prepared. Instead of trivalent chromium plating, the following plating solution was used for hexavalent chromium plating at 42 °C, 10 A / dm 2 , for 3 minutes, and except for this, the same operations as in Comparative Example 7 were carried out. The test results of the obtained chromium-plated component specimens are shown in Table 2 described later.

[0216] <Hexavalent chromium plating solution>

[0217] ·EBACHROM E-300LN process (manufactured by JCU Corporation)

[0218]

[0219] Comparative Example 10

[0220] Instead of trivalent chromium plating, the same hexavalent chromium plating as in Comparative Example 9 was performed, and otherwise, the same operations as in Example 3 were carried out. The appearance of the obtained chromium-plated component sample was extremely poor. Therefore, the R.N. evaluation in the CASS test was not performed. The results of swelling evaluation, etc. are shown in Table 2.

[0221] [Table 2]

[0222]

[0223] *Potential difference of the lower nickel plating layer with respect to the upper nickel plating layer #The lower layer is at a higher potential

[0224] According to the present invention, the R.N. of the chromium-plated component samples of Examples 3, 4, and 7 to 18, in which the anodic potential of the second nickel plating layer is in the range of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 and the first nickel plating layer has a potential 15 mV to 150 mV lower than that of the second nickel plating layer, are all 9.0 or more, and the swelling evaluation results are all 4 or more, showing excellent corrosion resistance. Among them, the R.N. of the chromium-plated component samples of Examples 13 to 18, in which the first nickel plating layer has a potential 70 mV or more lower than that of the second nickel plating layer, is 9.5 or more, and the swelling evaluation result is 5, showing particularly excellent corrosion resistance.

[0225] On the other hand, in Comparative Examples 7 and 8 where the potential difference between the first nickel plating layer and the second nickel plating layer is outside the above range, although the swelling test results are good, the R.N. is poor. The same is true for the samples of Comparative Examples 9 and 10 with hexavalent chromium plating. It can be seen that the potential of the second nickel plating layer and the potential difference between the two nickel plating layers both need to be within the specified range, and the chromium-plated component samples according to the present invention show corrosion resistance superior to that of hexavalent chromium-plated components.

[0226] Examples 19 to 70, Comparative Examples 11 to 34

[0227] The potential difference between the first nickel plating layer and the second nickel plating layer was fixed at -60 mV, and the nickel film thickness was fixed at 12 μm. The influence of the film thickness ratio on the corrosion resistance was studied. The treatment times of the first nickel plating and the second nickel plating were 1 minute to 29 minutes and 1 minute to 29 minutes respectively, and the film thickness ratio of the two nickel plating layers was varied in various ways. Except for this, the same operations as in Examples 1 to 8 and Comparative Examples 1 to 4 were carried out. It should be noted that the correlation between the plating time and the film thickness of each nickel plating layer was confirmed by the measurement based on the above cross-sectional micrographs. The appearance of the obtained chromium-plated component specimens just after production was all good. The test results of these specimens are shown in Tables 3 and 4 together with the results of Examples 1 to 4 and Comparative Examples 1 to 4, etc.

[0228] [Table 3]

[0229]

[0230] *Ratio of the film thickness of the first nickel plating layer to the second nickel plating layer

[0231] [Table 4]

[0232]

[0233] *Ratio of the film thickness of the first nickel plating layer to the second nickel plating layer

[0234] According to the present invention, for the chromium-plated component specimens of Examples 19 to 70 etc. where the anodic potential of the second nickel plating layer at a current density of 0.1 mA / cm 2 is -215 mV or less, the R.N. of all of them is 8.0 or more, and the swelling evaluation results are all 4 or more, showing excellent corrosion resistance. Among them, the chromium-plated component specimens with a low anodic potential of the second nickel plating layer, especially the chromium-plated component specimens of Examples 1, 2 and 19 to 30 with the potential as low as -273 mV, show extremely excellent corrosion resistance.

[0235] On the other hand, for the chromium-plated component specimens of Comparative Examples 11 to 34 etc. where the anodic potential of the second nickel plating layer is higher than -215 mV, although the R.N. is a good value, the swelling evaluation results are all 3 or less. In particular, for the chromium-plated component specimens of Comparative Examples 3, 4 and 23 to 34 with an anodic potential as high as -194 mV, the swelling evaluation results are all 1, and the corrosion resistance is extremely poor. This shows the importance of reducing the potential of the nickel plating layer.

[0236] In addition, regarding R.N., in the specimens with a lower potential of the two nickel plating layers, in addition, in the specimens where the ratio of the film thickness of the first nickel plating layer to the second nickel plating layer is 1:9 to 29:1, especially 1:4 to 14:1, and particularly 1:4 to 4:1, particularly good results were obtained.

[0237] Examples 71 - 72

[0238] Except that the total film thickness of the first nickel plating layer and the second nickel plating layer is 25 μm, the same operations as in Example 3 or 4 are performed (the potential difference between the two nickel plating layers is 60 mV, and the film thickness ratio is 1:1). All the obtained chromium-plated component specimens showed good appearance. The test results of these specimens are shown in Table 5 described later.

[0239] Comparative Examples 35 - 38

[0240] In addition, the film thickness ratio of semi-bright nickel plating layer : bright nickel plating layer : MP nickel plating layer is set to 9:6:1, the nickel film thickness is set to 25 μm, and the potential difference of the MP nickel plating layer relative to the bright nickel plating layer is set to +30 mV or +70 mV. Except for this, the same operations as in Comparative Example 5 are performed. In Comparative Examples 36 and 38, chromate treatment is also performed in the same manner as in Example 4. The test results of the obtained specimens are shown in Table 5 described later.

[0241] Comparative Example 39

[0242] Instead of trivalent chromium plating, hexavalent chromium plating is performed, and the same operations as in Comparative Example 35 are performed otherwise. The hexavalent chromium plating is performed in the same manner as in Comparative Example 9. The test results of the obtained specimens are shown in Table 5.

[0243] [Table 5]

[0244]

[0245] *Potential difference of the lower nickel plating layer relative to the upper nickel plating layer

[0246] ※The nickel plating layer is three-layer; potential difference relative to the central bright nickel plating layer

[0247] ※1 Lower layer +145 mV, upper layer +30 mV; ※2 Lower layer +145 mV, upper layer +70 mV

[0248] The chromium-plated component specimens according to Examples 71 and 72 of the present invention showed corrosion resistance equivalent to that of Comparative Examples 35 - 39 having a three-layer nickel plating structure, although the nickel plating layer is two-layer.

[0249] Examples 73 - 74

[0250] As the chromium plating, instead of white trivalent chromium plating, black trivalent chromium plating is performed, and the same operations as in Examples 5 - 6 are performed otherwise. Regarding the black trivalent chromium plating, the specimen is immersed in the following black trivalent chromium plating solution at 40 °C, 10 A / dm 2, under the condition of 3 minutes. The obtained chromium-plated component specimens showed good appearance. The test results of the obtained specimens are shown in Table 6 described later.

[0251] <Black trivalent chromium plating solution>

[0252] ·JTC-BK process (manufactured by JCU Co., Ltd.)

[0253]

[0254]

[0255] 《Comparative Examples 40 - 41》

[0256] As the chromium plating, black trivalent chromium plating was carried out, and the potential difference between the MP nickel plating layer and the bright nickel plating layer was +35 mV. Other than that, the same operations as in Comparative Example 35 or 36 were carried out. The black trivalent chromium plating was carried out in the same manner as in Examples 73 - 74. The test results of the obtained specimens are shown in Table 6.

[0257] [Table 6]

[0258]

[0259] *Potential difference of the lower nickel plating layer relative to the upper nickel plating layer

[0260] ※The nickel plating layer is three layers; potential difference relative to the central bright nickel plating layer: lower layer +145 mV, upper layer +35 mV

[0261] The chromium-plated component specimens according to Examples 73 and 74 of the present invention showed excellent corrosion resistance equivalent to or higher than that of the specimens of Comparative Examples 40 and 41 having a three-layer nickel plating layer. It can be seen that the effects of the present invention are exhibited regardless of whether the trivalent chromium plating layer is a white trivalent chromium plating layer, a black trivalent chromium plating layer, or any other trivalent chromium plating layer.

[0262] 《Examples 75 - 76》

[0263] Using the following satin nickel plating solution (pH 4.2) as the second nickel plating solution, a second nickel plating layer was formed under the conditions of 52 °C, 3 A / dm², and 15 minutes. Other than that, the same operations as in Example 3 or 4 were carried out. The appearances of the obtained chromium-plated component specimens were all good. The test results of these specimens are shown in Table 7.

[0264] <Satin nickel plating solution>

[0265] ·Watts bath

[0266] Nickel sulfate 470 g / L

[0267] Nickel chloride 40 g / L

[0268] Boric acid 40 g / L

[0269] ·DOUBLET SATIN process (manufactured by JCU Co., Ltd.)

[0270]

[0271] [Table 7]

[0272]

[0273] *Potential difference of the lower nickel plating layer relative to the upper nickel plating layer

[0274] It shows that even when the second nickel plating layer of the chromium plating component of the present invention is satin nickel plating layer, it exhibits excellent corrosion resistance.

[0275] From the above examples, it can be seen that according to the present invention, a chromium plating component with excellent corrosion resistance and good appearance can be manufactured through a more simplified process even when the upper layer is a trivalent chromium plating layer.

[0276] Symbol description

[0277] 1 Chromium plating component

[0278] 2 Substrate

[0279] 2A Surface of the substrate

[0280] 3 First nickel plating layer

[0281] 4 Second nickel plating layer

[0282] 5 Trivalent chromium plating layer

[0283] 21 Base material

[0284] 22 Surface layer

Claims

1. A chromium-plated component, the chromium-plated component comprising: A substrate having a surface layer made of copper or a copper alloy; A first nickel plating layer formed in contact with the surface layer of the substrate; A second nickel plating layer formed in contact with the first nickel plating layer; and A trivalent chromium plating layer formed in contact with the second nickel plating layer, The chromium-plated component is characterized in that The second nickel plating layer has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 2 The first nickel plating layer has a potential 15 mV to 150 mV lower than that of the second nickel plating layer.

2. The chromium-plated component according to claim 1, wherein, The film thickness ratio of the first nickel plating layer to the second nickel plating layer is 1:10 to 30:

1.

3. The chromium-plated component according to claim 1, wherein, The film thickness ratio of the first nickel plating layer to the second nickel plating layer is 1:4 to 14:

1.

4. The chromium-plated component according to claim 1, wherein, The total film thickness of the first nickel plating layer and the second nickel plating layer is 1 μm to 30 μm.

5. The chromium-plated component according to claim 1, wherein, An electrolytic conversion treatment film and / or an immersion conversion treatment film is further provided on the trivalent chromium plating layer.

6. The chromium-plated component according to claim 1, wherein, The second nickel plating layer is a layer free of non-conductive particles.

7. The chromium-plated component according to claim 1, wherein, The substrate is a base material made of one or more materials selected from the group consisting of resin, ceramic, and metal and having the surface layer mainly made of copper or a copper alloy, or a base material mainly made of copper or a copper alloy.

8. A method for manufacturing a chromium-plated component, the method for manufacturing a chromium-plated component comprising the following steps: On a substrate having a surface layer mainly made of copper or a copper alloy, a first nickel plating layer is formed in contact with the surface layer; A second nickel plating layer is formed in contact with the first nickel plating layer; and A trivalent chromium plating layer is formed in contact with the second nickel plating layer, The method for manufacturing a chromium-plated component is characterized in that The second nickel plating layer has an anodic potential of -215 mV to -290 mV at a current density of 0.1 mA / cm 2 2 The first nickel plating layer has a potential 15 mV to 150 mV lower than that of the second nickel plating layer.

9. The method for manufacturing a chromium-plated component according to claim 8, further comprising the step of forming an electrolytic conversion treatment film and / or an immersion conversion treatment film on the surface of the trivalent chromium plating layer.

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