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 and which has a good appearance; and a production method which enables the production of such a chromium-plated member. This chromium-plated member is provided with: a substrate having a surface layer comprising copper or a copper alloy; a bright nickel plating layer formed on the surface layer of the substrate in a contact manner; a high-potential nickel plating layer which is formed on the bright nickel plating layer in a contact manner and has a potential of 30-180 mV higher than that of the bright nickel plating layer; and a trivalent chromium plating layer formed on the high potential nickel plating layer in a contact manner. The film thickness ratio of the bright nickel plating layer to the high-potential nickel plating layer is preferably 1: 30 to 10: 1. The high-potential nickel plating layer is preferably a layer that does not contain non-conductive fine particles.

Description

Technical Field

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

[0002] Hitherto, chromium plating has been carried out 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 coating 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 as compared with 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), a product having a nickel plating layer as a base (nickel-chromium plated product) is particularly excellent in decorativeness and corrosion resistance and is 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 requirements for the corrosion resistance of chromium-plated components have 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 carried out.

[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 provided thereon. Here, the eutectic nickel plating layer is 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, the 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 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 nickel plating layers.

[0006] Patent Document 3 discloses a surface modification method, which oxidizes the surface of a chromium-plated component having the same structure as those in Patent Documents 1 and 2 to form an oxide coating of chromium on the surface of the chromium plating film. In addition, Patent Document 4 discloses a chromium-plated component, which successively has 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 any of these technologies, 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 the nickel plating layer, it is not necessarily possible to obtain the same corrosion resistance as that of hexavalent chromium plating. The plated products described in Patent Documents 1 and 2 are all 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 generally 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 products, the nickel plating layer has a three-layer structure (the same applies to the plated products described in Patent Documents 2 and 4 that require two layers as the nickel plating layer), and a semi-bright nickel plating layer (sulfur-free nickel plating layer) is formed on the substrate side. According to the findings of the present inventors, there is room for further improvement in terms of corrosion resistance in such a structure.

[0017] 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 and good appearance even when the upper layer is a trivalent chromium plating layer, and a manufacturing method capable of manufacturing such a chromium-plated component.

[0018] Means for Solving the Problems

[0019] The present inventors have found that in trivalent chromium plating, a bright nickel plating layer is formed directly above a copper-based substrate, then a high-potential nickel plating layer is formed directly above it, and then a trivalent chromium plating layer is formed, and the potential difference between the bright nickel plating layer and the high-potential nickel plating layer is specified to a specific value, whereby a chromium-plated component having excellent corrosion resistance and good appearance can be manufactured, and thus the present invention has been completed.

[0020] That is, the present invention provides the following (1) to (9).

[0021] (1) A chromium-plated component, characterized in that it comprises: a substrate having a surface layer made of copper or a copper alloy; a bright nickel plating layer formed in contact with the surface layer of the substrate; a high-potential nickel plating layer formed in contact with the bright nickel plating layer and having a potential 30 mV to 180 mV higher than that of the bright nickel plating layer; and a trivalent chromium plating layer formed in contact with the high-potential nickel plating layer.

[0022] (2) The chromium-plated component according to the above (1), wherein the film thickness ratio of the bright nickel plating layer to the high-potential nickel plating layer is 1:30 to 10:1.

[0023] (3) The chromium-plated component according to the above (1), wherein the film thickness ratio of the bright nickel plating layer to the high-potential nickel plating layer is 1:5 to 9:1.

[0024] (4) The chromium-plated component according to any one of the above (1) to (3), wherein the total film thickness of the bright nickel plating layer and the high-potential nickel plating layer is 1 μm to 30 μm.

[0025] (5) The chromium-plated component according to any one of the above (1) to (4), wherein an electrolytic conversion treatment film and / or an immersion conversion treatment film is further provided on the trivalent chromium plating layer.

[0026] (6) The chromium-plated component according to any one of (1) to (5) above, wherein the high-potential nickel plating layer is a layer free of non-conductive fine particles.

[0027] (7) The chromium-plated component according to any one of (1) to (6) above, wherein the substrate is a substrate made of one or more materials selected from the group consisting of resin, ceramic, and metal and having the surface layer made of copper or copper alloy, or a substrate made of copper or copper alloy.

[0028] (8) A method for manufacturing a chromium-plated component, characterized by comprising the following steps:

[0029] Forming a bright nickel plating layer in contact with the surface layer on a substrate having a surface layer made of copper or copper alloy;

[0030] Forming a high-potential nickel plating layer having a potential 30 mV to 180 mV higher than that of the bright nickel plating layer in contact with the bright nickel plating layer; and

[0031] Forming a trivalent chromium plating layer in contact with the high-potential nickel plating layer.

[0032] (9) The method for manufacturing a chromium-plated component according to (8) above, further comprising a step of forming an electrolytic chemical conversion film and / or an immersion chemical conversion film on the surface of the trivalent chromium plating layer.

[0033] Advantages of the Invention

[0034] The chromium-plated component of the present invention exhibits excellent corrosion resistance even when the upper layer is a trivalent chromium plating layer, and has a good appearance. In addition, according to the method for manufacturing a chromium-plated component of the present invention, a chromium-plated component having excellent corrosion resistance and appearance can be manufactured. Brief Description of the Drawings

[0035] Figure 1 It is a cross-sectional schematic view showing an embodiment of the chromium-plated component of the present invention. Detailed Description of the Embodiment

[0036] Hereinafter, the present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments.

[0037] "Chromium-Plated Component"

[0038] The chromium-plated component of the present invention is characterized in that it includes: a substrate having a surface layer made of copper or copper alloy; a bright nickel plating layer formed in contact with the surface layer of the substrate; a high-potential nickel plating layer formed in contact with the bright nickel plating layer and having a potential 30 mV to 180 mV higher than that of the bright nickel plating layer; and a trivalent chromium plating layer formed in contact with the high-potential nickel plating layer.

[0039] Figure 1 It is a schematic diagram showing a cross-section of a chromium-plated component according to an embodiment of the present invention. As Figure 1 shown, in the chromium-plated component 1 of the present embodiment, a bright nickel plating layer 3 is formed on the surface 2A of the substrate 2, a high-potential nickel plating layer 4 is formed thereon, and further a trivalent chromium plating layer 5 is formed on the upper layer thereof, and they are sequentially formed in contact with each other on the substrate surface or plating layer directly below. Hereinafter, each of these elements will be described.

[0040] [Substrate]

[0041] In the chromium-plated component 1, the substrate 2 is an object to be plated on whose surface 2A 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.

[0042] 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. The base material 21 may also be composed of copper or a copper alloy, and the base material 21 and the surface layer 22 may be continuous and integral.

[0043] (Base material)

[0044] The base material 21 corresponds to the main part of the substrate 2 to be plated, and there is no particular limitation on its shape and material. In Figure 1 the shown embodiment, the plating layers 3 to 5 are formed on one side of the flat substrate 2 with the surface layer 22 on the base material 21, but the chromium-plated component of the present invention is not limited to such a manner. The base material 21 can be, for example, various-shaped handles, grilles, moldings, car emblems and other automotive components, outboard engine components, faucet metal fittings, building materials components represented by door handles and window frames, home appliance components, and other components of any shape and use.

[0045] The base material 21 is preferably composed of one or more materials selected from the group consisting of resin, ceramic, and metal, and forms the substrate 2 with a surface layer 22 made of copper or a copper alloy, but is not limited to such materials. The base material 21 can also be a composite material of various resins, elastomers, ceramics, metals, carbon materials, etc. The base material 21 can also be composed of copper or a copper alloy by itself and form the substrate 2 without a surface layer of other elements. 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 unavoidable impurities.

[0046] When the base material 21 is made of a metal material, the composition of the metal 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 good adhesion, these metals can be appropriately subjected to activation treatment or strike plating. If copper or a copper alloy is used for strike plating or the like, the obtained base material 21 can be directly used as the substrate 2 in the chromium plating component 1.

[0047] 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 component 1 because it is easy to plate and easy to form a surface layer of copper or copper alloy.

[0048] (Plating treatment of the base material)

[0049] It is preferable to conduct a conductivity treatment on the ceramic or resin base material 21 as described above with a metal to facilitate plating. The method of conducting the conductivity treatment 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. Chemical plating with copper, copper alloy, nickel, or nickel alloy is particularly preferred. The method and conditions of chemical plating are also not particularly limited and can be carried out according to conventional methods and conditions.

[0050] It is preferable to further conduct electrocopper plating or electrocopper alloy plating (electrocopper-based plating) on the base material 21 that has been subjected to chemical plating. Through electrocopper-based plating, a surface layer 22 with particularly excellent adhesion and the like can be formed. When chemical plating is carried out with copper or a copper alloy and a copper-based layer is formed, it is also preferable to perform electrocopper-based plating in an overlapping manner. The method and conditions of electrocopper-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.

[0051] (Surface layer)

[0052] The surface layer 22 constitutes the surface of the base material 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 bright nickel plating layer 3, is formed in contact on the surface 2A side.

[0053] [Bright nickel plating layer]

[0054] In the chromium-plated component 1, a bright nickel plating layer 3 is formed in contact with the surface layer 22 of copper or a copper alloy on the substrate 2. That is, in the chromium-plated component 1, the bright nickel plating layer 3 is formed directly above the substrate 2 without intervening other layers such as a semi-bright nickel layer.

[0055] The bright nickel plating layer 3 contains sulfur in the nickel plating film. The bright nickel plating layer 3 is not particularly limited.

[0056] (Bright nickel plating)

[0057] The bright nickel plating layer 3 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.

[0058] In addition, as the primary brightener contained in the nickel plating solution for forming the bright nickel plating layer 3, for example, sodium 1,5-naphthalenedisulfonate, sodium 1,6-naphthalenedisulfonate, sodium 2,5-naphthalenedisulfonate, sodium 1,3,6-naphthalenetrisulfonate, sodium benzenesulfonate, sodium benzenesulfinate, sodium saccharin (o-benzoylsulfimide) and other aromatic sulfonimides, sulfinic acids, vinylsulfonic acid sodium salts, allylsulfonic acid sodium salts and other vinyl-based unsaturated sulfonates can be cited. They can be used alone or in combination of two or more.

[0059] In addition, a brightening / leveling agent (secondary brightener) for imparting brightness / leveling can be used together with or instead of the primary brightener. As the brightening / leveling agent, for example, 1,4-butynediol, hexynediol, propargyl alcohol and other acetylene-based unsaturated alcohols and their derivatives, pyridine-based sulfonate salts, etc. can be cited. They can also be used alone or in combination of two or more.

[0060] 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.

[0061] In the nickel plating solution, the above 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.

[0062] The plating solution for bright nickel plating preferably contains a wetting agent. Examples of the wetting agent include surfactants. The surfactant is 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 alone 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 Corporation) 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.

[0063] In addition, the conditions for electroplating used to form the bright nickel plating layer 3 are not particularly limited, and conventional conditions can be adopted. 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.

[0064] In this way, the bright nickel plating layer 3 can be formed in a state of being in contact with the surface layer 22 of the substrate 2.

[0065] [High-potential nickel plating layer]

[0066] In the chromium plating member 1, a high-potential nickel plating layer 4 is formed in contact with the bright nickel plating layer 3, and the high-potential nickel plating layer 4 has a potential 30 mV to 180 mV higher than that of the bright nickel plating layer 3. That is, in the chromium plating member 1, the high-potential nickel plating layer 4 having a specific electrochemical potential is formed directly above the bright nickel plating layer 3 without being formed on the side of the chromium plating layer 5 described later through other layers.

[0067] As long as the high-potential nickel plating layer 4 has a potential 30 mV to 180 mV higher than that of the bright nickel plating layer 3, it can be any nickel plating layer, and its composition and the like are not particularly limited. The electrochemical potential of the nickel plating layer is not uniquely determined only by the content of various components. For example, it can be controlled by adjusting the sulfur content and carbon content in the plating layer by using a potential regulator or the like.

[0068] (High-potential nickel plating)

[0069] The high-potential nickel plating layer 4 can be formed by electroplating treatment using a known nickel plating solution containing a desired amount of primary brightener, brightening / leveling agent (secondary brightener), potential regulator, and the like.

[0070] Specifically, regarding the nickel plating solution for forming the high-potential nickel plating layer 4, as the primary brightener and secondary brightener, the same substances as those used in the nickel plating solution for forming the above-mentioned bright nickel plating layer 3 can be used.

[0071] As the potential regulator contained in the nickel plating solution, well-known potential regulators can also be used. Examples thereof include butynediol, hexynediol, propargyl alcohol, allyl sodium sulfate, formalin, chloral hydrate (2,2,2-trichloro-1,1-ethanediol), tribromoacetaldehyde hydrate (2,2,2-tribromo-1,1-ethanediol), and the like.

[0072] It should be noted that as the potential regulator, commercially available products such as ADDITIVE-E (manufactured by JCU Corporation) can also be used.

[0073] By performing the plating treatment using such a nickel plating solution in which the concentrations of the primary brightener, secondary brightener, potential regulator, etc. are appropriately adjusted, a high-potential nickel plating layer 4 having the above-mentioned potential difference can be formed.

[0074] As the nickel plating solution, a nickel plating solution not containing non-conductive fine particles such as silica is preferably used to form a high-potential nickel plating layer 4 free of non-conductive fine particles. In addition, in the case of containing non-conductive fine particles, the content is also preferably about 5% by mass or less, particularly preferably 1% by mass or less, based on the total mass of the high-potential nickel plating layer 4. By forming a high-potential 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, the appearance of the chromium-plated member 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 to an extent of 0.1% by mass or less.

[0075] In addition, the conditions for the electroplating for forming the high-potential nickel plating layer 4 are not particularly limited, and conventional conditions can be adopted. 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 and more preferably 2 A / dm 2 to 5 A / dm 2 .

[0076] (Potential difference measurement)

[0077] As described above, the high-potential nickel plating layer 4 has a potential that is 30 mV to 180 mV higher than that of the bright nickel plating layer 3. Additionally, it preferably has a potential that is 30 mV to 160 mV higher, more preferably 40 mV to 160 mV higher, further preferably 60 mV to 120 mV higher, and particularly preferably 60 mV to 80 mV higher than that of the bright nickel plating layer 3.

[0078] 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 from which the trivalent chromium plating layer 5 has been removed 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 measured using a commercially available device such as a multilayer nickel plating corrosion resistance measurement device.

[0079] In the chromium-plated component 1, as described above, a bright nickel plating layer 3 is formed directly above the surface layer 22 in the substrate 2, and a high-potential nickel plating layer 4 is formed directly above it and on the side of the chromium plating layer 5. Moreover, the high-potential nickel plating layer 4 has a potential that is 30 mV to 180 mV higher than that of the bright nickel plating layer 3. According to such a chromium-plated component 1, excellent corrosion resistance and good appearance are exhibited.

[0080] 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 the first reason, it is considered that due to the sacrificial corrosion of the bright nickel plating layer 3 with a low potential, not only the corrosion reaction of the chromium plating layer 5 is inhibited, but also the corrosion reaction of the high-potential nickel plating layer 4 itself as the substrate is inhibited. Additionally, as the second reason, it is considered that the nickel plating layer directly formed in contact with the surface layer 22 of the substrate 2 being the bright nickel plating layer with a lower potential rather than the semi-bright nickel plating layer also contributes. Due to the sacrificial corrosion of this bright nickel plating layer 3, the corrosion of the adjacent surface layer 22 made of copper or a copper alloy is further inhibited, and as a result, the overall corrosion resistance of the chromium-plated component 1 may be improved.

[0081] [Film Thickness and Film Thickness Ratio of Nickel Plating Layer]

[0082] In the chromium-plated component 1, the film thicknesses of the bright nickel plating layer 3 and the high-potential nickel plating layer 4 as the nickel plating layers 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. Additionally, from the perspective of making the corrosion resistance more excellent and reducing the nickel plating cost, the total film thickness (nickel film thickness) of the bright nickel plating layer 3 and the high-potential 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.

[0083] In addition, the film thickness ratio of the bright nickel plating layer 3 to the high-potential nickel plating layer 4 is preferably in the range of 1:30 to 10:1, more preferably in the range of 1:9 to 9:1. Thereby, there is a tendency to exhibit more excellent corrosion resistance. In addition, by making the film thickness ratio in the range of 1:5 to 9:1, particularly 1:3 to 7:1, especially 1:3 to 5:1, the excellent corrosion resistance of the chromium plating member 1 can be maintained for a longer time.

[0084] Of course, the film thickness ratio of the two nickel plating layers is not limited to the above ratio and can be set to various values according to the purpose and use. Specifically, from the viewpoint of improving the effect of the bright nickel plating layer 3 based on sacrificial corrosion, the film thickness ratio of the bright nickel plating layer 3 to the high-potential nickel plating layer 4 can be set, for example, in the range of 1:2 to 7:1, particularly 1:1 to 5:1, especially 2:1 to 4:1. In addition, from the viewpoint of reducing the corrosion of the two nickel plating layer parts themselves, the film thickness ratio of the bright nickel plating layer 3 to the high-potential nickel plating layer 4 can be set, for example, in the range of 1:3 to 4:1, especially 1:3 to 2:1.

[0085] [Trivalent chromium plating layer]

[0086] In the chromium plating member 1, a trivalent chromium plating layer 5 is formed in contact with the high-potential nickel plating layer 4. Through this trivalent chromium plating layer 5, a plating member having excellent corrosion resistance and aesthetic decorativeness and useful for decorative purposes and the like can be provided.

[0087] The method for forming the trivalent chromium plating layer 5 is not particularly limited, and it can be processed under desired conditions by a conventional plating method. For example, it can be formed by electroplating using a known trivalent chromium plating solution containing a trivalent chromium compound, a complexing agent, a conductive salt, a pH buffer, etc.

[0088] 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, basic chromium sulfate and / or chromium sulfate are preferably used. 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, about 1 g / L to 25 g / L in terms of metallic chromium.

[0089] In addition, there is no particular limitation on the complexing agent. Examples thereof include aliphatic monocarboxylic acids (salts) such as formic acid, ammonium formate, and potassium formate; aliphatic dicarboxylic acids and their salts such as succinic acid, maleic acid, and malic acid; aliphatic tricarboxylic acids (salts) such as citric acid and ammonium citrate; carboxylic acids (salts) having two or more hydroxyl groups and two or more carboxyl groups such as tartaric acid, diammonium tartrate, and sodium tartrate; and amino carboxylic acids such as glycine. These complexing agents may be used alone or in combination of two or more. The content of the complexing agent in the trivalent chromium plating solution may be, for example, on the order of 0.1 g / L to 50 g / L.

[0090] In addition, there is no particular limitation on the conductive salt. Examples thereof include sulfates such as potassium sulfate, ammonium sulfate, and sodium sulfate; chlorides such as potassium chloride, ammonium chloride, and sodium chloride; and sulfamic acid salts such as potassium sulfamate, ammonium sulfamate, and sodium sulfamate. These conductive salts may be used alone or in combination of two or more. The content of the conductive salt in the trivalent chromium plating solution may be, for example, on the order of 100 g / L to 500 g / L.

[0091] 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.

[0092] The trivalent chromium plating solution may further contain blackening agents such as sodium thiocyanate, methionine, and cysteine, tin salts such as ascorbic acid, sodium ascorbate, hydrogen peroxide, polyethylene glycol, tin sulfate, and tin chloride, iron chloride, sodium saccharin, sodium allylsulfonate, sodium vinylsulfonate, etc.

[0093] 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.), アーサスクロム series (manufactured by SurTec), TriChrome series (manufactured by Atotech), Envirochrome process, Twilite process (both manufactured by Macdermid), etc. may be used. The chromium plating layer usually has a silver-white appearance, but a black plating layer may also be formed by mixing, for example, the above blackening agent in the plating solution.

[0094] There is no particular limitation on the conditions for electroplating used to form the trivalent chromium plating layer 5, and conventional conditions may be employed. For example, it may 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 of.

[0095] In the chromium-plated component 1, as also shown in the embodiments described later, excellent corrosion resistance and good appearance are exhibited regardless of the type and film thickness of the trivalent chromium plating layer 5. Therefore, the film thickness of the trivalent chromium plating layer 5 is not particularly limited and can be, for example, 0.05 μm or more, specifically 0.1 μm to 1.0 μm, particularly 0.15 μm to 0.50 μm, which is a general plating layer thickness in chromium-plated products.

[0096] [Electrolytic conversion treatment, immersion conversion treatment]

[0097] The chromium-plated component 1 preferably further has an electrolytic conversion treatment film and / or an immersion conversion treatment film on the above-mentioned trivalent chromium plating layer 5. 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 used according to requirements. As examples, there can be mentioned chromate treatment, wax treatment, treatment with a solution of 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 to these. 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.

[0098] (Chromate treatment)

[0099] 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.

[0100] As the chromate treatment, there can be mentioned, for example, well-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 Co., Ltd.) 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.

[0101] [Chromium-plated component and its uses]

[0102] The chromium-plated component 1 exhibits excellent corrosion resistance even when the upper layer is a 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 material components, and home appliance components.

[0103] "Manufacturing Method of Chromium-Plated Component"

[0104] As described above, the chromium-plated component 1 can be manufactured by a manufacturing method having the following steps: on a substrate 2 having a surface layer 22 made of copper or a copper alloy, a bright nickel plating layer 3 is formed in contact on the surface layer 22; a high-potential nickel plating layer 4 having a potential 30 mV to 180 mV higher than that of the bright nickel plating layer 3 is formed in contact on the bright nickel plating layer 3; and a trivalent chromium plating layer 5 is formed in contact on the high-potential nickel plating layer 4.

[0105] Each step of forming the bright nickel plating layer 3, the high-potential 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 it can also be manufactured with fewer steps.

[0106] Examples

[0107] 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.

[0108] "Example 1"

[0109] The chromium-plated component according to the present invention was manufactured as follows.

[0110] (Preparation of Substrate)

[0111] 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 performed. The chromic acid etching was carried out using a treatment solution containing chromic anhydride: 400 g / L, sulfuric acid: 400 g / L, and trivalent chromium: 10 g / L. The electroless nickel plating was carried out using the ENILEX NI-5 process (manufactured by JCU Corporation) 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.

[0112] (Bright Nickel Plating)

[0113] Immerse the obtained substrate in the following bright nickel plating solution, and form a bright nickel plating layer with a thickness of 6 μm under the conditions of 50 °C, 3 A / dm 2 , and 15 minutes.

[0114] <Bright nickel plating solution>

[0115] · Watts bath

[0116] Nickel sulfate 260 g / L

[0117] Nickel chloride 40 g / L

[0118] Boric acid 40 g / L

[0119] · HI-BRITE #88 process (manufactured by JCU Co., Ltd.)

[0120] #810 (secondary brightener) 3 ml / L

[0121] #82 (wetting agent) 2 ml / L

[0122] #83 (primary brightener) 10 ml / L

[0123] (High-potential nickel plating)

[0124] Next, immerse it in the following high-potential nickel plating solution, and form a high-potential nickel plating layer with a thickness of 6 μm under the conditions of 55 °C, 3 A / dm 2 , and 15 minutes (the total film thickness of the bright nickel plating layer and the high-potential nickel plating layer = 12 μm, the thickness ratio of the bright nickel plating layer to the high-potential nickel plating layer = 1:1). Mix a potential regulator of ADDITIVE-E (manufactured by JCU Co., Ltd.) in the plating solution at a concentration of 0.1 ml / L to adjust the potential difference between the high-potential nickel plating layer and the bright nickel plating layer to +45 mV.

[0125] <High-potential nickel plating solution>

[0126] · Watts bath

[0127] Nickel sulfate 260 g / L

[0128] Nickel chloride 40 g / L

[0129] Boric acid 40 g / L

[0130] · HI-BRITE #88 process (manufactured by JCU Co., Ltd.)

[0131]

[0132] (Trivalent chromium plating)

[0133] 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 high-potential nickel plating layer under the conditions of 55 °C, 10 A / dm 2 ², and 4 minutes. The obtained chromium-plated component specimen had a good appearance.

[0134] <Trivalent chromium plating solution>

[0135]

[0136] 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.

[0137] (Film thickness, potential difference measurement)

[0138] · The film thickness of each nickel plating layer was measured from the cross-sectional micrograph.

[0139] · 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.

[0140] · The potential difference between the high-potential nickel plating layer and the bright nickel plating layer was measured by the STEP test in accordance with ASTM B764: "Simultaneous determination of the thickness and potential of each layer in a multilayer nickel deposit". 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 was prepared. The specimen for the above potential difference measurement was placed in this electrolytic solution, and the measurement was carried out using the multilayer nickel plating corrosion resistance measuring device "ED-3" manufactured by Central Research Institute of Electric Power Industry Co., Ltd. with a silver-silver chloride electrode as the reference electrode.

[0141] (Corrosion resistance evaluation)

[0142] The corrosion resistance was evaluated by the CASS test based on 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 was sprayed onto the specimen under the following conditions, and the rating number (R.N.) after 80 hours was measured (in another part of the examples described later, the R.N. after 40 hours and 160 hours was also measured).

[0143] · Spray volume: 1.5 ± 0.5 ml / 80 cm 2 ²

[0144] · Temperature inside the test chamber: 50 ± 2 °C

[0145] · Temperature of the brine tank: 50 ± 2 °C

[0146] · Temperature of air saturator: 63 ± 2 °C

[0147] · Compressed air pressure: 70 kPa to 167 kPa

[0148] Example 2

[0149] 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 for 1 minute. The obtained chromium-plated component specimen had a good appearance. For this specimen, the test was carried out in the same manner as in Example 1, and the results are shown in Table 1 described later.

[0150] Examples 3 to 7

[0151] The concentration of ADDITIVE-E in the high-potential nickel plating solution was varied between 0.1 ml / L and 2 ml / L, and the potential difference between the high-potential nickel plating layer and the bright nickel plating layer was adjusted to +65 mV, +80 mV, and +160 mV. Otherwise, the same operations as in Example 1 or 2 were carried out. The obtained chromium-plated component specimens all had good appearances. The test results for these specimens are shown in Table 1 described later.

[0152] Comparative Example 1

[0153] A plating solution having the following composition was used instead of the high-potential nickel plating solution to form a 95 mV low-potential nickel plating layer directly above the bright nickel plating layer. Otherwise, the same operations as in Example 1 were carried out. It should be noted that the formation of the low-potential nickel plating layer was carried out at 50 °C and 3 A / dm 2 for 15 minutes. The test results of the obtained chromium-plated component specimens are shown in Table 1 described later.

[0154] <Low-potential nickel plating solution>

[0155] · Watts bath

[0156] Nickel sulfate 260 g / L

[0157] Nickel chloride 40 g / L

[0158] Boric acid 40 g / L

[0159] · TRI-STRIKE process (manufactured by JCU Co., Ltd.)

[0160] TRI-STRIKE 5 ml / L

[0161] #82 (Wetting Agent) 2 ml / L

[0162] Comparative Example 2

[0163] The high-potential nickel plating solution was made to contain no ADDITIVE-E, and then the bath temperature was lowered to 52°C. The potential difference between the high-potential nickel plating layer and the bright nickel plating layer was adjusted to 5 mV. Otherwise, the same operations as in Example 1 were carried out. The test results of the obtained chromium-plated component specimens are shown in Table 2 described later.

[0164] Comparative Example 3

[0165] In the same manner as the chromium-plated components described in Patent Document 4, specimens having a three-layer structure of nickel plating layer were manufactured under the following conditions and evaluated in the same manner as in Example 1.

[0166] (Semi-bright nickel plating)

[0167] 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 , and 15 minutes.

[0168] <Semi-bright nickel plating solution>

[0169] · Watts bath

[0170] Nickel sulfate 260 g / L

[0171] Nickel chloride 40 g / L

[0172] Boric acid 40 g / L

[0173] · CF-24T process (manufactured by JCU Corporation)

[0174] CF-24T 1 ml / L

[0175] #82-K (Wetting Agent) 1 ml / L

[0176] (Bright nickel plating)

[0177] Next, it was immersed in the following bright nickel plating solution, and a bright nickel plating layer was formed under the conditions of 50°C, 3 A / dm 2 , and 12 minutes. The bright nickel plating layer had a potential 145 mV lower than that of the underlying semi-bright nickel plating layer.

[0178] <Bright nickel plating solution>

[0179] · Watts bath

[0180] Nickel sulfate 260 g / L

[0181] Nickel chloride 40 g / L

[0182] Boric acid 40 g / L

[0183] · HI-BRITE #88 process (manufactured by JCU Co., Ltd.)

[0184] #810 (secondary brightener) 3 ml / L

[0185] #82 (wetting agent) 2 ml / L

[0186] #83 (primary brightener) 10 ml / L

[0187] (MP nickel plating)

[0188] Furthermore, immerse 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.

[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 plating component specimens)

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

[0199] 《Comparative Example 4》

[0200] Prepare a specimen in which a bright nickel plating layer is formed on the side of the chromium plating layer rather than on the side of the substrate. 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-plated component specimen, 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 3, etc., but the plating time of the bright nickel plating was 15 minutes. In addition, in the chromium-plated component specimen of this comparative example, the bright nickel plating layer had a potential 145 mV lower than that of the underlying semi-bright nickel plating layer. The test results of the obtained chromium-plated component specimen are shown in Table 1 described later.

[0201] Comparative Example 5

[0202] 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 1 were carried out. The test results of the obtained chromium-plated component specimen are shown in Table 1 described later.

[0203] <Hexavalent chromium plating solution>

[0204] ·EBACHROM E-300LN process (manufactured by JCU Corporation)

[0205]

[0206] Comparative Example 6

[0207] Instead of trivalent chromium plating, the same hexavalent chromium plating as in Comparative Example 5 was carried out, and except for this, the same operations as in Example 5 were carried out. The appearance of the obtained chromium-plated component specimen was extremely poor. Therefore, the corrosion resistance evaluation was not carried out.

[0208] [Table 1]

[0209]

[0210] *Potential difference (mV) of the upper-layer nickel plating layer relative to the bright nickel plating layer

[0211] ※Potential difference relative to the central bright nickel plating layer: lower layer +145 mV, upper layer +55 mV

[0212] #Potential difference (mV) of the upper layer (bright nickel plating layer) relative to the lower layer (semi-bright nickel plating layer)

[0213] According to the present invention, the rating numbers (R.N.) of the chromium-plated component specimens of Examples 1 to 7 having a high-potential nickel plating layer with a potential difference of +30 to +180 mV with respect to the bright nickel plating layer on the lower layer side in the CASS test are all 9.3 or more, showing excellent corrosion resistance. These R.N. values are significantly higher than those of Comparative Examples 1 and 2 outside the scope of the present invention for the potential difference between the two nickel plating layers, especially the specimen of Comparative Example 1 with a low-potential upper nickel plating layer, showing the effect of improving corrosion resistance brought about by specifying the potential difference.

[0214] The R.N. values in Examples 1 to 7 are also higher than those in Comparative Example 3 with a three-layer nickel plating structure described in Patent Document 4 or Comparative Example 5 with a hexavalent chromium plating. In addition, the specimens of the examples without chromate treatment also showed the same high R.N. as the chromate-treated products. 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 possible to manufacture chromium-plated components with good corrosion resistance and appearance without using hexavalent chromium-based reagents.

[0215] In addition, the specimens of Examples 1 to 7 according to the present invention showed significantly better corrosion resistance than the specimens of Comparative Example 4 having a semi-bright nickel plating layer on the substrate side and a bright nickel plating layer on the chromium plating layer side. This shows the importance of forming a bright nickel plating layer in contact on the upper surface of the substrate. It should be noted that in the specimen of Example 5, the film thickness of the chromium plating layer is more than twice that of the other examples, but the R.N. is the same as that of the other examples. This implies that the chromium-plated components of the present invention show excellent corrosion resistance regardless of the film thickness of the trivalent chromium plating layer.

[0216] It should be noted that the chromium-plated components of the present invention have an R.N. as high as 9.3 or more even when the nickel film thickness is 12 μm, which is equal to or higher than that of the chromium-plated components with a nickel film thickness of 25 μm described later. Despite the nickel film thickness being less than half, it still shows the same corrosion resistance, thus 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.

[0217] 《Examples 8 to 43》

[0218] The concentration of ADDITIVE-E in the high-potential nickel plating solution was varied between 0.1 ml / L and 2 ml / L to make various adjustments to the potential difference between the two nickel plating layers. Also, the treatment times for bright nickel plating and high-potential nickel plating were 1 minute to 29 minutes and 1 minute to 29 minutes, respectively, to vary the film thickness ratio of the two nickel plating layers. Other than that, the same operations as in Example 1 or 2 were carried out to fabricate chromium-plated component specimens (the nickel film thickness was 12 μm in all cases). It should be noted that the correlation between the plating time and the film thickness of each nickel plating layer was confirmed by measurement based on the above cross-sectional micrographs. All the obtained chromium-plated component specimens had good appearances. The test results of these specimens, together with the results of Comparative Examples 1 and 2, etc., are shown in Table 2.

[0219] [Table 2]

[0220]

[0221] 1) Potential difference (mV) of the upper-layer nickel plating layer relative to the bright nickel plating layer

[0222] 2) Film thickness ratio of each nickel plating layer, the underlined boldface is the value of the bright nickel plating layer

[0223] For the specimens of Examples 1 to 43 of the present invention having a high-potential nickel plating layer (upper-layer nickel plating layer) with a potential 35 mV to 160 mV higher than that of the bright nickel plating layer (lower-layer nickel plating layer), the R.N. in the CASS test was 9.0 or more in all cases, showing excellent corrosion resistance. In particular, for the specimens with a potential difference of +65 mV or more between the two nickel plating layers, the R.N. was approximately 9.5 or more, showing extremely excellent corrosion resistance.

[0224] It should be noted that in Example 5 and Example 30, the film thickness of the chromium plating layer was quite different, but the appearance and corrosion resistance were both good. This again shows that the chromium-plated components of the present invention can exhibit excellent corrosion resistance regardless of the film thickness of the trivalent chromium plating layer. In addition, the results of Examples 8 to 11 and Examples 28 to 31 suggest that if the film thickness ratio of the two nickel plating layers is more equal than about 9:1, the R.N. of the chromium-plated component specimens becomes higher.

[0225] 《Examples 44 to 71》

[0226] The potential difference between the two nickel plating layers was fixed at +65 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 bright nickel plating and high-potential nickel plating were 1 minute to 29 minutes and 1 minute to 29 minutes, respectively. The film thickness ratio of the two nickel plating layers was varied in various ways. Otherwise, the same operations as in Example 3 or 4 were carried out. It should be noted that the CASS test was carried out for 40 hours, 80 hours, and 160 hours. In addition, the correlation between the plating time and the film thickness of each nickel plating layer was confirmed by measurement based on the above cross-sectional micrographs. All the obtained chromium-plated component specimens showed good appearance. The test results of these specimens, together with the results of Example 3 and Comparative Example 3, etc., are shown in Table 3.

[0227] [Table 3]

[0228]

[0229] *Film thickness ratio of each nickel plating layer, the underlined boldface is the value of the bright nickel plating layer

[0230] ※Film thickness ratio of semi-bright nickel plating layer: bright nickel plating layer: MP nickel plating layer

[0231] Potential difference relative to the central bright nickel plating layer: +145 mV for the lower layer, +55 mV for the upper layer

[0232] Compared with the specimens of Comparative Example 3 with a three-layer structure of nickel plating layer, the chromium-plated component specimens of these examples all showed R.N. equal to or higher than that. That is, although it is a two-layer nickel plating structure with a less complicated manufacturing process, it still has better corrosion resistance. Among them, the specimens with a film thickness ratio of bright nickel plating layer: high-potential nickel plating layer of 1:29 to 9:1, especially the specimens with a film thickness ratio of 1:5 to 9:1, all had an R.N. of 9.0 or more without chromate treatment and 9.3 or more after chromate treatment after 80 hours, showing excellent corrosion resistance. In particular, the specimens with a film thickness ratio of 1:3 to 5:1 had an R.N. of approximately 9.5 or more after 80 hours, which was extremely excellent.

[0233] 《Examples 72 - 81》

[0234] The total film thickness of the bright nickel plating layer and the high-potential nickel plating layer was made 25 μm. Otherwise, the same operations as in Example 3 or 4 were carried out (the potential difference between the two nickel plating layers was 65 mV). All the obtained chromium-plated component specimens showed good appearance. The test results of these specimens are shown in Table 4 described later.

[0235] 《Comparative Examples 7 - 10》

[0236] The total film thickness of all nickel plating layers was made 25 μm, and the potential difference of the MP nickel plating layer with respect to the bright nickel plating layer was made +30 mV or +70 mV. Other than this, the same operations as in Comparative Example 3 were carried out. In Comparative Examples 8 and 10, the same chromate treatment as in Example 4 was also carried out. The test results of the obtained specimens are shown in Table 4 described later.

[0237] 《Comparative Example 11》

[0238] Instead of trivalent chromium plating, hexavalent chromium plating was carried out. Other than this, the same operations as in Comparative Example 7 were carried out. The hexavalent chromium plating was carried out in the same manner as in Comparative Example 5. The test results of the obtained specimens are shown in Table 4.

[0239] [Table 4]

[0240]

[0241] *The film thickness ratio of each nickel plating layer, the underlined boldface is the value of the bright nickel plating layer

[0242] #Film thickness ratio of semi-bright nickel plating layer: bright nickel plating layer: MP nickel plating layer

[0243] Potential difference from the central bright nickel plating layer: #1 is +145 for the lower layer and +30 for the upper layer; #2 is +145 for the lower layer and +70 for the upper layer (mV)

[0244] The R.N. of the chromium-plated component specimens according to Examples 72 to 81 of the present invention in the CASS test was all 9.0 or more, showing corrosion resistance equal to or higher than that of Comparative Examples 7 to 11 having a three-layer nickel plating structure. In particular, the R.N. of the chromium-plated component specimens with a film thickness ratio of bright nickel plating layer: high-potential nickel plating layer of 1:29 to 3:1 without chromate treatment was 9.3 or more, showing extremely excellent corrosion resistance.

[0245] 《Examples 82 to 83》

[0246] As the chromium plating, instead of white trivalent chromium plating, black trivalent chromium plating was carried out. Other than this, the same operations as in Example 5 were carried out. Regarding the black trivalent chromium plating, the specimen was immersed in the following black trivalent chromium plating solution and carried out under the conditions of 40 °C, 10 A / dm 2 , 3 minutes. The obtained chromium-plated component specimens had a good appearance. The test results of the obtained specimens are shown in Table 5 described later.

[0247] <Black trivalent chromium plating solution>

[0248] ·JTC-BK process (manufactured by JCU Co., Ltd.)

[0249]

[0250] Comparative Examples 12 - 13

[0251] As the chromium plating, black trivalent chromium plating was carried out, and the potential difference of the MP nickel plating layer with respect to the bright nickel plating layer was +35 mV. Otherwise, the same operations as in Comparative Example 7 or 8 were performed. The black trivalent chromium plating was carried out in the same manner as in Examples 82 - 83. The test results of the obtained specimens are shown in Table 5.

[0252] [Table 5]

[0253]

[0254] * The film thickness ratio of each nickel plating layer, the underlined boldface is the value of the bright nickel plating layer

[0255] # Film thickness ratio of semi - bright nickel plating layer: bright nickel plating layer: MP nickel plating layer

[0256] Potential difference with respect to the central bright nickel plating layer: +145 mV for the lower layer, +35 mV for the upper layer

[0257] The chromium - plated component specimens of Examples 82 and 83 according to the present invention showed excellent corrosion resistance exceeding that of the specimens of Comparative Examples 12 and 13 having three - layer nickel plating layers. 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.

[0258] From the above examples, according to the present invention, it is possible to manufacture a chromium - plated component with excellent corrosion resistance and good appearance even when the upper layer is a trivalent chromium plating layer through a simpler process.

[0259] Symbol Explanation

[0260] 1 Chromium - plated component

[0261] 2 Substrate

[0262] 2A Surface of the substrate

[0263] 3 Bright nickel plating layer

[0264] 4 High - potential nickel plating layer

[0265] 5 Trivalent chromium plating layer

[0266] 21 Base material

[0267] 22 Surface layer

Claims

1. A chromium-plated component, characterized in that, It has: a substrate having a surface layer made of copper or a copper alloy; a bright nickel plating layer formed in contact with the surface layer of the substrate; a high-potential nickel plating layer formed in contact with the bright nickel plating layer and having a potential 30 mV to 180 mV higher than that of the bright nickel plating layer; and a trivalent chromium plating layer formed in contact with the high-potential nickel plating layer.

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

1.

3. The chromium-plated component according to claim 1, wherein, The film thickness ratio of the bright nickel plating layer to the high-potential nickel plating layer is 1:5 to 9:

1.

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

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

6. The chromium-plated component according to claim 1, wherein, The high-potential nickel plating layer is a layer free of non-conductive fine 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 made of copper or a copper alloy, or a base material made of copper or a copper alloy.

8. A method for manufacturing a chromium-plated component, characterized in that, The following steps are included: forming a bright nickel plating layer in contact with the surface layer on a substrate having a surface layer made of copper or a copper alloy; forming a high-potential nickel plating layer having a potential 30 mV to 180 mV higher than that of the bright nickel plating layer in contact with the bright nickel plating layer; and forming a trivalent chromium plating layer in contact with the high-potential nickel plating layer.

9. The method for manufacturing a chromium plating component according to claim 8, 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.

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