Method for producing trivalent chromium plated product and trivalent chromium plated product

Abstract

To provide a method for producing a trivalent chromium plated product having a glossy appearance equal to that of hexavalent chromium plating, and to provide a trivalent chromium plated product.SOLUTION: The method for producing a trivalent chromium plated product of the present invention includes a plating treatment step of energizing an object to be plated as a cathode in a trivalent chromium plating solution, and an ion removal step of removing ions of metals other than Cr. In the ion removal step, an ion exchange resin for removing ions of metals other than Cr is used. The color difference Δ E between the plating film of the trivalent chromium plated product obtained by the method for producing a trivalent chromium plated product and the hexavalent chromium plating film is less than 3.5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a trivalent chromium plated product and a trivalent chromium plated product. [Background technology]

[0002] Hexavalent chromium plating solutions are widely used in the metal finishing industry for both decorative and hard chrome plating because chrome plating gives a silvery luster and has excellent corrosion resistance. However, in recent years, with consideration given to the environment, development has progressed in plating solutions that contain trivalent chromium and do not use hexavalent chromium. On the other hand, it has generally been difficult to achieve the same performance as hexavalent chromium plating with plating solutions containing trivalent chromium. For example, trivalent chromium electrolytes tend to be more sensitive to metal impurities than hexavalent chromium electrolytes.

[0003] In recent years, various trivalent chromium plating solutions that aim to achieve the same performance as hexavalent chromium plating have been reported, including a method for improving the corrosion resistance of a trivalent chromium coating (Patent Document 1) and a method for controlling the color of a trivalent chromium coating (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2021-507114 [Patent Document 2] Special Publication No. 2015-510549 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned trivalent chromium plating, particularly decorative trivalent chromium plating, has the problem that it is not possible to obtain a coating that has the same glossy appearance as hexavalent chromium plating and also has corrosion resistance.

[0006] The present disclosure has been made in view of the above circumstances, and provides a method for producing a trivalent chromium-plated product having a glossy appearance equivalent to that of hexavalent chromium plating, and a trivalent chromium-plated product. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a specific trivalent chromium plating solution, plating conditions, etc., and have completed the present invention.

[0008] That is, the present invention includes the following aspects. [1] A method for producing a trivalent chromium plating product, comprising: a plating step of applying current to a substrate as a cathode in a trivalent chromium plating solution; and an ion removal step of removing ions of metals other than Cr, The ion removal step uses an ion exchange resin that removes ions of metals other than Cr, A method for producing a trivalent chromium plating product, wherein the plating film of the trivalent chromium plating product obtained by the method for producing a trivalent chromium plating product has a color difference ΔE of less than 3.5 from a hexavalent chromium plating film. [2] The method for producing a trivalent chromium plating product according to [1], wherein the plating film of the trivalent chromium plating product has a difference in lightness ΔL value from the hexavalent chromium plating film of less than 2.0, a color characteristic a value of +2.0 to -2.0, and a color characteristic b value of +2.0 to -2.0. [3] The method for producing a trivalent chromium plated product according to [1] or [2], wherein the thickness of the plating film of the trivalent chromium plated product is 0.2 μm or more and 1 μm or less. [4] In the plating treatment step, The plating temperature is 30 to 65°C. The plating treatment pH is 3.0 to 4.2, Plating current density is 4~10A / dm 2 The method for producing a trivalent chromium plating product according to any one of [1] to [3], [5] In the plating treatment step, The plating process time is 3 to 30 minutes. The plating electrode distance is 200 to 500 mm, Plating process agitation: 5 to 100 L / min·m 2 and The method for producing a trivalent chromium plated product according to any one of [1] to [4], wherein the plating electrode uses one or more selected from the group consisting of Ti, Pt, Ir oxide, and Ta. [6] In the plating treatment step, The plating temperature is 50 to 56°C. The plating treatment pH is 3.0 to 3.8, Plating current density is 5~8A / dm 2 and The plating process takes 3 to 10 minutes. The plating electrode distance is 250 to 350 mm, Plating process agitation: 5 to 100 L / min·m 2 and The method for producing a trivalent chromium plated product according to any one of [1] to [5], wherein the plating electrode uses one or more selected from the group consisting of Ti, Pt, Ir oxide, and Ta. [7] A trivalent chromium plating product obtained by the method for producing a trivalent chromium plating product according to any one of [1] to [6], The plating film of the trivalent chromium plating product is characterized in that the color difference ΔE from a hexavalent chromium plating film is less than 2.0. [8] The plating film of the trivalent chromium plating product has a brightness difference ΔL value with respect to the hexavalent chromium plating film of less than 2.0, The trivalent chromium plating product according to [7], wherein the color characteristics are a value of +2.0 to -2.0 and b value of +2.0 to -2.0. [9] The trivalent chromium plating product according to [7] or [8], wherein the thickness of the plating film of the trivalent chromium plating product is 0.2 μm or more and 1 μm or less.

[10] The trivalent chromium plating product according to any one of [7] to [9], wherein the plating film of the trivalent chromium plating product has an L value of 65 to 90, a lightness difference ΔL value from a hexavalent chromium plating film of less than 2.0, and a b value of +1.0 to -1.5. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a principle diagram of a trivalent chromium plating apparatus in the first embodiment. [Figure 2] FIG. 2 is a principle diagram showing the relationship between the electrode distance and the width of the object to be plated in the first embodiment (when the width of the object to be plated is small). [Figure 3] FIG. 3 is a principle diagram showing the relationship between the electrode distance and the width of the object to be plated in the first embodiment (when the object to be plated has a large width). [Figure 4] FIG. 4 shows the relationship between the concentration of various ions other than Cr and the amount of immersion when trivalent Cr plating is performed for 8 minutes and then the plate is repeatedly immersed in the solution for 40 minutes in a case where the ion removal process of removing ions of metals other than Cr using an ion exchange resin is not included in Comparative Example 1. [Figure 5] FIG. 5 is a graph showing the relationship between the amount of untreated solution and the elapsed time when 120 L of plating solution is passed through the ion exchange resin at a circulation rate of 2 L / min in Reference Example 1, in which an ion removal step of removing ions of metals other than Cr using an ion exchange resin is included. [Figure 6] FIG. 6 is a graph showing the relationship between the concentrations of various ions other than Cr and the elapsed time when 120 L of plating solution is passed through the ion exchange resin at a circulation rate of 2 L / min in Reference Example 1, in which an ion removal step of removing ions of metals other than Cr using an ion exchange resin is included. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following embodiment shows one aspect of the present disclosure, does not limit the present disclosure, and can be modified as desired within the scope of the technical idea of ​​the present disclosure. In the following drawings, the scale of each structure is different from the actual structure to make each configuration easier to understand.

[0011] (Method of manufacturing trivalent chromium plating products) A method for producing a trivalent chromium-plated product according to one embodiment of the present disclosure includes a plating step in which a current is applied to a substrate in a trivalent chromium plating solution using the substrate as the cathode, and an ion removal step in which ions of metals other than Cr are removed. The ion removal step uses an ion exchange resin that removes ions of metals other than Cr. The plating film of the trivalent chromium-plated product obtained by the method for producing a trivalent chromium-plated product has a color difference ΔE of less than 3.5 compared to a hexavalent chromium-plated film. Therefore, the mixture of trivalent chromium-plated products with hexavalent chromium products is not a concern, and it is easier to gradually convert from conventional hexavalent chromium plating methods to trivalent chromium plating methods. The "ions of metals other than Cr" include, for example, ions of metals such as Cu and Zn that become impurities.

[0012] FIG. 1 shows the principle of the trivalent chromium plating apparatus of this embodiment. In the plating process, for example, as shown in FIG. 1, a workpiece 1 is immersed between two anodes (2A, 2B) in a trivalent chromium plating solution 4 in a plating tank 5. Then, a current is passed through the workpiece 1, which serves as the cathode 3, to plate the workpiece. That is, a metal chromium plating is formed from a chemical containing trivalent chromium as a main component. An anode chamber (not shown) may be formed near the anodes (2A, 2B), for example, using a known cation exchange membrane. Examples of the anodes (2A, 2B) include Ti electrodes coated with a known Ir-Ta composite oxide thin film. The cathode 3 is electrically connected to the workpiece 1. If necessary, a stirring device (not shown) for stirring the trivalent chromium plating solution 4 may be provided.

[0013] The method for producing a trivalent chromium-plated product of the present embodiment may include, in addition to the above-mentioned plating treatment step, steps such as a pretreatment step for cleaning, a nickel plating step, and a post-treatment step including cleaning, as necessary.

[0014] The pretreatment processes for the purpose of cleaning include dissolving metal surfaces and processing oils that have oxidized over time, removing machining oils with alkali, ultrasonic cleaning of processing and polishing residues, physical foaming cleaning by electrolysis in alkali, chemical dissolution cleaning, and acid neutralization of alkaline cleaning solutions. By combining these processes appropriately, the substrate can be made more suitable for plating. In the embodiment of the present disclosure, it is not necessary to provide a pre-treatment step. Although examples of the pre-treatment step have been described above, the present disclosure is not limited to the above, and any suitable pre-treatment steps may be selected and combined as needed, and the order of the pre-treatment steps is not limited.

[0015] The nickel plating process is a process of plating nickel. For example, seal nickel, bright nickel, supplemental flash nickel, semi-bright nickel, electroless nickel, emulsion nickel, etc. are used. This process allows the surface to be chrome-plated or the surface after chrome plating to have the desired unevenness. It is desirable to use a nickel plating that is suited to the substrate, application, and purpose of the object to be plated.

[0016] The post-treatment including cleaning is, for example, a post-treatment of the plated object obtained in the plating process by electrolysis or acid immersion. The electrolysis method is a method of forming a protective coating on the surface of the plated object using electrolysis. The acid immersion method is a method of immersing the plated object in an acidic solution to form a protective coating on the surface or passivate the plated object. This can further stabilize the surface of the coating.

[0017] Although four main steps have been described above, it is also possible to perform the plating process on the object to be plated by repeating the described processes multiple times, and by adding processes as needed, such as water washing, between each process.

[0018] [Ion exchange resin] Examples of the ion exchange resin according to this embodiment include styrene-based iminodiacetic acid functional group-type ion exchange resins and styrene-based aminomethyl phosphate functional group-type ion exchange resins. Examples of the styrene-based iminodiacetic acid functional group-type ion exchange resins include the commercially available AMBERSEP IRC748 (manufactured by Organo Corporation). Examples of the styrene-based aminomethyl phosphate functional group-type ion exchange resins include the commercially available AMBERSEP IRC747UPS (manufactured by Organo Corporation) and the commercially available SurTec IAT (manufactured by SurTec MMC Japan Co., Ltd.). It is believed that by using such an ion exchange resin, the initially adsorbed trivalent chromium ions are replaced by divalent metal ions upon contact with the resin.

[0019] [Item to be plated] The substrates used for plating include iron substrates such as non-ferrous copper alloys, zinc, zinc alloys, and stainless steel, as well as resin substrates. For example, when a copper alloy substrate is used, nickel plating is applied to the substrate, followed by a chrome plating as the outermost layer. When zinc or a zinc alloy substrate is used, copper plating is applied to the substrate, followed by nickel plating, and then a chrome plating as the outermost layer. When a resin substrate is used, the substrate is subjected to a conductive treatment such as electroless plating of copper or nickel, followed by semi-bright nickel and bright nickel plating, followed by a chrome plating as the outermost layer. This layer structure, excluding surface treatments, in which chrome plating is applied as the outermost layer, i.e., nickel plating or alloy plating, can create the desired unevenness on the surface to be chrome-plated or the surface after chrome plating. The object to be plated in this embodiment may be an object that has already been treated by the above-mentioned nickel plating step, etc. For example, when the substrate of the object to be plated is a copper alloy substrate, a zinc or zinc alloy substrate, or a resin substrate, the object may be one that has been treated by the above-mentioned nickel plating, the above-mentioned copper plating / nickel plating, or the above-mentioned copper or nickel electroless plating / nickel plating.

[0020] [Trivalent chromium plating solution] The trivalent chromium plating solution according to this embodiment contains a Cr source, a complexing agent, an auxiliary complexing agent, an auxiliary agent, a pH buffer, a conductive salt, and a surfactant. In addition, as a commercially available plating solution, there is a chemical such as SurTec 883XT (manufactured by SurTec MMC Japan Co., Ltd.).

[0021] <Cr source> Examples of the Cr source include chromium compounds of sulfuric acid, basic sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. The Cr source is preferably a sulfuric acid-based compound in which unnecessary substances unintended to be in the coating are hardly incorporated. More preferably, it is chromium(III) sulfate or basic chromium(III) sulfate. The content of the Cr source in the trivalent chromium plating solution is not particularly limited, but for example, in terms of Cr ions, it is preferably 0.3 to 1.0 mol / L, more preferably 0.4 to 0.6 mol / L.

[0022] <Complexing agent> Examples of the complexing agent include organic acids selected from the group consisting of carboxylic acids such as saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and amino acids, or derivatives of such organic acids. One or more complexing agents can be appropriately selected and combined for use. Examples of the derivative of the organic acid include amides such as saccharin, and sodium, potassium, and ammonium salts of the carboxylic acid. Specific examples of the organic acid include acetic acid, oxalic acid, formic acid, succinic acid, lactic acid, maleic acid, malonic acid, malic acid, carboxylic acid, tricarboxylic acid, aminocarboxylic acid, tartaric acid, glycine, and the like. The complexing agent is preferably saccharin, oxalic acid with a small molecular weight, or formic acid, which is difficult to be incorporated into the coating. More preferably, it is saccharin. For example, when obtaining a trivalent chromium coating, a complexing agent must be added to the plating solution to facilitate chromium deposition. This results in organic matter being incorporated into the chromium coating, which tends to result in a lower purity and darker color than a hexavalent chromium coating. Complexing agents have the effect of lowering the high deposition potential of trivalent chromium ions. In other words, by including them, chromium deposition occurs against the predominant water electrolysis, resulting in the deposition of chromium ions. Specifically, they can make chromium deposition more dominant than water electrolysis, thereby promoting the deposition of chromium ions. Specifically, trivalent chromium ions have a more positive potential than hexavalent chromium ions, so even if the energy is increased, water electrolysis prevails and chromium deposition does not occur. Therefore, when depositing trivalent chromium ions, complexing can be used to control the potential to favor deposition. The content of the complexing agent in the trivalent chromium plating solution is not particularly limited, but for example, the molar ratio of the complexing agent to Cr is preferably 1 / 1 to 1 / 26, and more preferably 1 / 10 to 1 / 17. The content of the complexing agent in the trivalent chromium plating solution is not particularly limited, but is preferably 0.02 to 0.07 mol / L, and more preferably 0.03 to 0.05 mol / L, for example.

[0023] <Adjuvants> Auxiliaries are added to adjust various properties of the plating solution, including corrosion resistance, complex formation, color adjustment, plating solution life extension, and efficiency adjustment. The adjuvant is preferably, for example, an organic compound, an inorganic acid, or an alcohol. More specifically, examples thereof include sodium thiocyanate, ascorbic acid, sodium ascorbate, hydrogen peroxide, polyethylene glycol, tin salts such as tin sulfate and tin chloride, iron chloride, iron sulfate, sodium allylsulfonate, vinylsulfonic acid, and thiourea. One or more adjuvants can be appropriately selected and used in combination. The content in the trivalent chromium plating solution may be added according to the plating state of the product and is not particularly limited.

[0024] <pH buffer> Examples of the pH buffer include boric acid or salts of boric acid. Boric acid serves to buffer the shift of the pH of the product surface to alkaline during plating. On the other hand, depending on the concentration, it has a property of being prone to crystallization at low temperatures. A good appearance can be obtained by adjusting to an appropriate content. The content of the pH buffer in the trivalent chromium plating solution is not particularly limited, but for example, it is preferably 40 to 100 g / L, more preferably 70 to 90 g / L.

[0025] <Conductive salt> Examples of the conductive salt include compounds of sulfuric acid, hydrochloric acid, and nitric acid with sodium, potassium, and ammonium. The conductive salt affects the inter-liquid resistance of the plating solution. A good appearance can be obtained by setting an appropriate content. When the amount is insufficient, the inter-liquid resistance becomes high. On the other hand, since there is a limit to the dissolution amount, adjustment to an appropriate content is required. The content of the conductive salt in the trivalent chromium plating solution is not particularly limited, but sulfuric acid-based salts of the same series as the anion used in the Cr supply source are preferred. For example, the content of sodium sulfate is preferably 100 to 250 g / L, more preferably 150 to 230 g / L.

[0026] <Surfactant> Examples of the surfactant include succinic acid, sulfosuccinic acid, alkyl sulfosuccinic acid, dodecylbenzene sulfonic acid, alcohols, etc. The surfactant plays a role in enhancing the affinity between the metal plating surface and the solution. Therefore, the adhesion strength can be maintained. The content of the surfactant in the trivalent chromium plating solution is not particularly limited, but for example, alkyl sulfosuccinic acid is preferably 0.03 to 0.90 g / L, more preferably 0.05 to 0.18 g / L.

[0027] [Trivalent chromium plating treatment conditions] The method for producing a trivalent chromium plated product of this embodiment may include a plating step in which an electric current is passed through the object to be plated as a cathode under the following plating conditions. The plating conditions include, for example, plating temperature, plating pH, plating time, plating efficiency, electrode distance, stirring speed, or electrodes, etc. A good trivalent chromium plating product can be obtained by using one or a combination of two or more of these.

[0028] The plating temperature refers to the temperature of the plating solution. The plating temperature is, for example, preferably 30 to 65° C., and more preferably 50 to 56° C. Within this temperature range, crystallization of boric acid does not occur, and a glossy appearance can be obtained.

[0029] The plating treatment pH is the pH of the plating solution. The plating treatment pH is preferably 2.8 to 4.2, and more preferably 3.0 to 3.8. Within this pH range, a good trivalent chromium plating product can be obtained, in which complex formation with Cr occurs.

[0030] The plating current density is 4 to 10 A / dm 2 is preferable, and more preferably 5 to 8 A / dm 2 In this range, hexavalent Cr ions are not formed.

[0031] The plating treatment time is the time for which current is passed. The plating treatment time is preferably 3 to 30 minutes, and more preferably 5 to 10 minutes. Within this treatment time range, a better color tone can be obtained. The distance between electrodes during plating is preferably 200 to 500 mm, and more preferably 250 to 350 mm. The plating process stirring speed is the speed at which the solution is stirred. The plating process stirring speed is 5 to 100 L / min m 2 is preferable, and more preferably 7 to 54 L / min m 2 is. The plating electrode preferably uses one or more materials selected from the group consisting of Ti, Pt, Ir oxide, and Ta.

[0032] [Evaluation of trivalent chromium plating film] <Color difference ΔE> When the colors of the standard hexavalent chromium plating are L6, a6, and b6, and the colors of the trivalent chromium plating are L3, a3, and b3, the color difference ΔE can be calculated using the following formula. The method for measuring the color difference will be explained in the examples.

[0033] ΔE=√((L6-L3) 2 +(a6-a3) 2 +(b6-b3) 2 )

[0034] For example, if the differences are L = 2, a = 2, and b = 2, ΔE=√(4+4+4)=√12=3.46. The plating solution and plating conditions used for the reference hexavalent chromium plating will be explained later. The substrate (object to be plated) for the hexavalent chromium plating may have the same uneven shape as the trivalent chromium plating to be compared, or may be the same substrate as the trivalent chromium plating to be compared. In this case, the above value (L6 - L3) can be free from the influence of the reflectance that changes due to the unevenness of the substrate.

[0035] <Lightness difference ΔL value> The appearance of trivalent chromium plated products can be expressed using the a-value, b-value, and L-value. The L-value here refers to brightness, which is also affected by the substrate. Therefore, a more accurate representation of the color tone of the plating itself can be achieved by using the brightness difference ΔL, which eliminates the effect of reflectance that varies with substrate irregularities. Specifically, using substrates with the same irregularities, hexavalent chromium plating and trivalent chromium plating are performed, respectively. The absolute value ΔL of the difference between the brightness L6 of the resulting hexavalent chromium plating film and the brightness L3 of the trivalent chromium plating film (L3 - L6) can be used to indicate the range required for plating. For example, for a stop valve with a rough surface, the conventional hexavalent chromium plating coating has an L6 of 72.85, while the trivalent chromium plating coating of this embodiment has an L3 of 72.50. For a water outlet with a fine surface, the hexavalent chromium plating coating has an L6 of 86.68, while the trivalent chromium plating coating has an L3 of 87.07. The L value indicates brightness and changes with reflectance, so it is affected by the unevenness of the substrate. As a result, even with the same plating, the L6 values ​​for a stopcock with a rough surface and a spout with a fine surface are significantly different, at 72.85 and 86.68, respectively. In other words, the L value can also be considered to represent appearance. On the other hand, when comparing the same substrate as above, because the uneven shape of the substrate is the same, when the brightness difference between hexavalent chromium and trivalent chromium is expressed as ΔL, the stopcock is 0.35 and the spout is 0.39, so there is almost no difference. By clarifying the standards, it is possible to accurately grasp the color differences of plating. The intended product is a plumbing fixture such as a water outlet, a water outlet pipe, a stop valve, and a handle, but the invention can also be applied to parts and products used in household appliances, not just plumbing fixtures.

[0036] [Hexavalent chromium plating film and its manufacturing method] The "hexavalent chromium plating film" of the present disclosure is a decorative chromium plating film formed by a known hexavalent chromium plating method using a known hexavalent chromium plating solution.

[0037] Examples of the known hexavalent chromium plating method and the known hexavalent chromium plating solution include the method and plating solution described in Non-Patent Document 1 below (e.g., particularly, the description on page 91, "3.3.2 Hexavalent chromium bath composition and working conditions"). [Non-patent document 1] Electroplating Research Society: Plating Textbook, published by Nikkan Kogyo Shimbun (1986)

[0038] The hexavalent chromium plating method may be, for example, a known electrolytic method, etc. Specific examples include plating conditions disclosed in the comparative examples described below. An example of the hexavalent chromium plating solution is an electrolytic solution called a Sargent bath, which is prepared by adding 0.92 g / L of sulfuric acid, a primary catalyst, to an aqueous solution containing 230 g / L of industrial chromic acid, which is 1 / 250 of the amount of chromic acid. The substrate for hexavalent chromium plating to be compared with the present disclosure may be an object of a similar shape to the substrate for trivalent chromium plating of the present disclosure, or may simply be a flat object such as a test piece. The substrate for hexavalent chromium plating may be a substrate made of the same material as the substrate for trivalent chromium plating of the present disclosure, or may be made of a similar material or a different material. It is preferable that the substrate for hexavalent chromium plating has the same material for at least the outermost chromium plating layer and the layers below it. The substrate to be plated with hexavalent chromium plating, which is the subject of comparison to the present disclosure, may have the same shape, substrate material, and layer structure as the substrate to be plated with trivalent chromium plating of the present disclosure. For example, the layer structure may be as follows, depending on the material of the substrate. For example, when a copper alloy is used as the substrate, nickel plating is applied to the substrate, and hexavalent chromium plating is provided as the outermost layer on top of that. When zinc or a zinc alloy is used as the substrate, copper plating is applied to the substrate, nickel is applied thereon, and then hexavalent chromium plating is provided as the outermost layer. When a resin substrate is used as the substrate, the substrate is subjected to a conductive treatment such as electroless plating of copper or nickel, and then semi-bright nickel and bright nickel plating are applied thereon, and hexavalent chromium plating is provided as the outermost layer. From the viewpoint of providing a trivalent chromium plating product having a glossy appearance equivalent to that of conventional hexavalent chromium plating, the "conventional hexavalent chromium plating film" of the present disclosure may have a thickness similar to that of a hexavalent chromium plating film commonly used in practice. That is, the thickness may be different from that of the trivalent chromium plating film of the present disclosure. Specifically, the "conventional hexavalent chromium plating film" of the present disclosure may have a thickness of 0.1 to 0.5 μm, or may have a thickness of 0.3 μm.

[0039] (trivalent chromium plating product) A trivalent chromium plating product according to one embodiment of the present invention is obtained by the above-described method for producing a trivalent chromium plating product (including each preferred embodiment). That is, it is a trivalent chromium plating product treated with trivalent chromium plating. The plating film of the trivalent chromium plating product according to this embodiment has a color difference ΔE from a hexavalent chromium plating film of less than 3.5. The plating film of the trivalent chromium plating product according to this embodiment preferably has a color difference ΔE from a hexavalent chromium plating film of less than 2.0. The plating film appearance of the trivalent chromium plating product according to this embodiment is excellent, and the color difference ΔE from a hexavalent chromium plating film, which is a thin metal film electrolytically produced from an aqueous solution of chromic acid and sulfuric acid, is not noticeable even when mixed with hexavalent chromium products. In this disclosure, a "trivalent chromium plating product" refers to a plated object and a trivalent chromium plating film covering the entire or partial surface of the plated object. Examples of the plated object include components and products used in home appliances, such as the spouts, outlet pipes, stop valves, and handles of faucets, and handles of cabinets and doors. A "trivalent chromium plating film" is a chromium metal film formed by electrolytic reduction of trivalent chromium ions. That is, it is a chromium metal film derived from trivalent chromium ions. A "hexavalent chromium plating film" is a chromium metal film formed by electrolytic reduction of hexavalent chromium ions. In theory, trivalent chromium plating films and hexavalent chromium plating films are the same chromium metal film. However, due to differences in the valence of the derived chromium ions, it is presumed that the metal microstructures, trace amounts of components other than chromium, and mechanical properties of the metal films differ. Furthermore, the type of derived chromium ions also tends to be labeled on the final product. Therefore, it is recognized that "trivalent chromium plating film" and "hexavalent chromium plating film" are films with different properties. As described above, the trivalent chromium plating product of this embodiment can be evaluated to a certain extent based on its color characteristics, but there are still many unknowns regarding the relationship between the microstructural characteristics of the resulting product and the color characteristics, which depend on the components of the trivalent chromium plating solution, plating conditions, etc. Microstructural characteristics include, for example, components other than the Cr metal in the coating, the surface microstructure, the cross-sectional microstructure, and the structure of the metallic chromium. The relationship between these characteristics and the color characteristics remains largely unknown. In particular, the comparison of the microstructures of metallic chromium coatings obtained by trivalent chromium plating and hexavalent chromium plating has not been fully elucidated.

[0040] The difference in lightness ΔL between the plating film of the trivalent chromium plating product and the hexavalent chromium plating film is preferably less than 2.0, more preferably 1.5 or less, and may be 0.1 or more, 0.2 or more, 0.5 or more, or 1.0 or more. It is more preferable that the plating film of the trivalent chromium plating product has color characteristics of a value a of +2.0 to -2.0 and a value b of +2.0 to -2.0. The lightness difference ΔL value is the absolute value of the difference between the lightness L of the plating film of a trivalent chromium plating product and the lightness L of the plating film of a hexavalent chromium plating product obtained using a substrate (substrate to be plated) having the same uneven shape. From the viewpoint of ensuring an excellent appearance, the thickness is preferably 0.2 μm or more. Furthermore, from the viewpoint of cost-effectiveness of the decorative chrome plating product, the thickness of the plating film may be 1 μm or less. More preferably, the thickness is 0.2 μm or more and 0.8 μm or less, and even more preferably, the thickness is 0.2 μm or more and 0.4 μm or less. It is more preferable that the plating film of the trivalent chromium plating product has an L value of 65 to 90 (ΔL less than 2.0), an a value of +0.5 to −1.0, and a value of +1.0 to −1.5. As described above, the trivalent chromium plating product of this embodiment can be evaluated to a certain extent based on its color characteristics, but there are still many unknowns regarding the relationship between the microstructural characteristics of the resulting product and the color characteristics, which depend on the components of the trivalent chromium plating solution, plating conditions, etc. Microstructural characteristics include, for example, components other than the Cr metal in the coating, the surface microstructure, the cross-sectional microstructure, and the structure of the metallic chromium. The relationship between these characteristics and the color characteristics remains largely unknown. In particular, the comparison of the microstructures of metallic chromium coatings obtained by trivalent chromium plating and hexavalent chromium plating has not been fully elucidated. [Example]

[0041] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0042] Example 1 A trivalent chromium plating product was produced for a water outlet as the object to be plated by a manufacturing method including a plating step under the following plating conditions using a trivalent chromium plating solution or hexavalent chromium plating solution of the composition shown below, and a step of adsorbing and removing metal ions other than Cr. In the step of adsorbing and removing metal ions other than Cr, an ion exchange resin (AMBERSEP IRC748, size, ion exchange resin amount: volume 1.2 L (volume 1 / 100 of the plating solution) that removes metal ions other than Cr) was used. Eight portions of the trivalent chromium plating were applied to the water outlet as the object to be plated, and the water outlet was repeatedly immersed in the solution for 40 minutes. As a result, approximately 450 water outlets (plated area 1707 dm) were plated. 2 ) When plating, the trivalent chromium plating product did not become cloudy. Copper and zinc ions that leach from copper alloy substrates into plating solutions are difficult to precipitate in hexavalent chromium plating solutions, but they precipitate easily in trivalent chromium plating solutions, so the tolerance is small. Compared to hexavalent chromium plating solutions, trivalent chromium plating solutions tend to precipitate metal ions such as copper and zinc leach- ed from the substrate more easily, and are therefore more sensitive to metal impurities.

[0043] The ion exchange conditions were as follows: Amount of ion exchange resin: Volume 1.2 L (resin volume is 1 / 100 of the plating solution) Circulation flow rate to ion exchange resin: 2 L / min for 120 L (surface velocity is approximately 90 mm / min = speed passing through the resin)

[0044] Spout: Made of brass, with a relatively smooth buffed finish, pipe-shaped, approximately 500 mm long, with a surface area of ​​3.62 dm 2 (471g) and two pieces were taken.

[0045] The trivalent chromium plating film obtained as the trivalent chromium plating product was evaluated, and the evaluation results are shown in Table 1.

[0046] <Composition of trivalent chromium plating solution> The plating solution used contains approximately 0.5 mol / L of chromium (III) sulfate or basic chromium (III) sulfate as the Cr source, saccharin as a complexing agent at a molar ratio of approximately 1 / 15 to Cr, 70 to 100 g of boric acid as an auxiliary agent, 150 to 230 g of sodium sulfate as a conductive salt, and a small amount of alkylsulfosuccinic acid. A commercially available plating solution with similar components, Sutec 883XT (manufactured by Surtec MMC Japan Co., Ltd.), may also be used.

[0047] <Trivalent chromium plating conditions> Shown in Table 1.

[0048] <Electrode distance> Figures 2 and 3 are simplified diagrams showing the principle of the relationship between the electrode distance and the width of the workpiece in a typical electroplating facility. Anodes are placed facing each other in a plating tank, which is filled with a solution such as a plating solution containing the metal ions to be deposited and a complexing agent.

[0049] The object to be plated is immersed in the solution of the plating tank so that it is positioned between two anodes. Then, the object to be plated is plated by passing an electric current through the object to be plated as the cathode. That is, in the embodiment of the present disclosure, chrome plating is formed from a chemical containing trivalent chromium as a main component. Here, the distance between the anode and the jig that fixes the cathode is defined as the inter-electrode distance.

[0050] As shown in the principle diagrams of Figures 2 and 3, the effect on the coating of the plating product differs depending on the ratio of the width of the objects 21 and 31 to the direction between the electrodes (horizontal direction in Figure 1). Even if Figures 2 and 3 have the same inter-electrode distance (d21, d22, d31, d32), the width (direction between the electrodes, horizontal direction in Figure 1) of Figure 3 is larger, so the inter-electrode distance in Figure 3 has a greater effect on plating than Figure 2. For example, in the case of the water outlet shown in Figure 2, the outer diameter is 30 mm, the distance between electrodes (d21, d22) is 250 mm, the position D22 closest to the electrode is 250 mm - 30 mm / 2 = 235 mm, and the position D21 farthest from the electrode is 250 mm. The ratio of these distances is 0.94. The distance between electrodes (d21, d22) is 250 mm. On the other hand, in the case of the bath faucet shown in Figure 3, the height is 70 mm, the distance between the electrodes (d31, d32) is 250 mm, the position D32 closest to the electrode is 250-70m=180 mm, the position D31 farthest is 250 mm, and the ratio of these distances is 0.72. If the distance between the poles (d21, d22, d31, d32) is set to 200 mm, a shallow spout will have a distance ratio of 0.93 and will be less affected, but in the case of a bathroom faucet, the distance ratio will be 0.65, and the deeper the object to be plated, the more pronounced the difference depending on the part.

[0051] <Stirring strength> When using air agitation instead of mechanical agitation, the agitation force weakens as the liquid surface area increases, even if the amount of air blown in is the same. 2 The flow strength was expressed as the amount of air blown into the tube per minute. The mixing strength is 2750cm 2 The flow strength was expressed as the amount of air blown into the tube per minute. Strong mixing means a liquid surface area of ​​2750 cm 2 The air blown in per minute is 15L or more (ejection volume: 54L / min m 2 ). During stirring, the liquid surface area is 2750cm 2The air blown in per minute is less than 10 to 15 L (ejection volume: 36 to 54 L / min m 2 ). Weak mixing means a liquid surface area of ​​2750 cm 2 The air blown in per minute is 2 to 6 L, and the ejection volume is 7 to 21 L / min m 2 ).

[0052] <color tone> The color of the surface of the coating of the trivalent chromium plating product and the surface of the coating of the hexavalent chromium plating product was measured using a color difference meter (color difference meter CR-400 (manufactured by Konica Minolta, Inc.) measurement conditions: SCI). The L*a*b* value in the L*a*b* color system was measured. In addition, the color difference ΔE of the change in the color of the coating surface of the trivalent chromium plating product was calculated based on the color of the coating surface of the hexavalent chromium plating product of the same type of plated object (base material). For example, the trivalent chromium plating products of Examples 1 and 2, Reference Examples 1 and 2, and Comparative Example 2 were compared with the hexavalent chromium plating product of Comparative Example 1. In addition, the color difference ΔE of the change in color of the coating surface of the trivalent chromium plating product was calculated based on the color of the coating surface of the hexavalent chromium plating product. The hexavalent chromium plating product used as the reference was the same type of plated object as the trivalent chromium plating product being calculated.

[0053] <Appearance: Evaluation method for cloudiness> The appearance of the plated object is evaluated visually. If the appearance is not noticeable, it is judged that there is no cloudiness and is rated as "A." If the appearance is noticeable, it is judged that there is cloudiness and is rated as "B."

[0054] [Table 1]

[0055] In Table 1, the meaning of each symbol is explained below. Plated object S: Water outlet Plating solution T: trivalent chromium, H: hexavalent chromium *1:Based on theoretical calculation Example 2 A trivalent chromium-plated product was formed in the same manner as in Example 1, except that an ion exchange resin, SurTec880IAT (manufactured by SurTec MMC Japan Co., Ltd.), which adsorbs and removes ions of metals other than Cr, was used in an amount of 1.2 L by volume (1 / 100 of the volume of the plating solution), and the trivalent chromium plating conditions shown in Table 1 were used. For the water outlets to be plated, trivalent Cr plating was applied for 8 minutes, and the water outlets were repeatedly immersed in the solution for 40 minutes. As a result, approximately 450 water outlets (total plating area: 1707 dm2) were plated. 2 ) When plating, the trivalent chromium plating product did not become cloudy.

[0056] The trivalent chromium plating film obtained as the trivalent chromium plating product was evaluated, and the evaluation results are shown in Table 1.

[0057] (Comparative Example 1) A hexavalent chromium plated product was formed in the same manner as in Example 1, except that no ion exchange resin was used and the following hexavalent chromium plating solution and hexavalent chromium plating conditions shown in Table 1 were used. The plating film of the product was evaluated, and the results are shown in Table 1.

[0058] <Composition of hexavalent chromium plating solution> The hexavalent chromium plating solution used was an electrolytic solution generally known as a Sargent bath. Specifically, an aqueous solution containing 230g / L of industrial chromic acid was added with 0.92g / L of sulfuric acid, which is the primary catalyst and is 1 / 250 of the amount of chromic acid.

[0059] (Comparative Example 2) A trivalent chromium-plated product was formed in the same manner as in Example 1, except that no ion exchange resin was used and the trivalent chromium plating conditions shown in Table 1 were used. The target object was a water outlet, and trivalent chromium plating was applied to 8 portions of the object, followed by repeated 40-minute immersion in the solution. As a result, approximately 450 water outlets (total plated area: 1707 dm2) were plated. 2 ) When plating, the trivalent chromium plating result became cloudy. The trivalent chromium plating film of the trivalent chromium plating product at the time when cloudiness occurred was evaluated, and the results are shown in Table 1.

[0060] (Reference example 1) A trivalent chromium-plated product was formed in the same manner as in Example 1, except that no ion exchange resin was used and the trivalent chromium plating conditions shown in Table 1 were used. Trivalent chromium plating was applied to a water outlet as the object to be plated for 8 minutes, and the object was repeatedly immersed in the solution for 40 minutes. As a result, when approximately 45 water outlets were plated, no cloudiness occurred in the coating of the trivalent chromium-plated product. The trivalent chromium plating film obtained as the trivalent chromium plating product was evaluated, and the evaluation results are shown in Table 1.

[0061] (Reference example 2) A trivalent chromium-plated product was formed in the same manner as in Example 1, except that no ion exchange resin was used and the trivalent chromium plating conditions shown in Table 1 were used. Trivalent chromium plating was applied to a water outlet as the object to be plated for 8 minutes, and the object was repeatedly immersed in the solution for 40 minutes. As a result, when approximately 300 water outlets were plated, no cloudiness occurred in the coating of the trivalent chromium-plated product. The trivalent chromium plating film obtained as the trivalent chromium plating product was evaluated, and the evaluation results are shown in Table 1.

[0062] Figure 4 shows the relationship between the concentration of various ions other than Cr and the amount of immersion when the process does not include an ion removal process using ion exchange resin to remove ions of metals other than Cr. Trivalent Cr plating is performed for 8 minutes, followed by repeated immersion for 40 minutes. Measurement of the various ions at the time cloudiness occurred revealed that the concentrations reached Ni: 14.6 ppm, Cu: 3.7 ppm, and Zn: 1.3 ppm.

[0063] (Reference example 3) FIG. 5 is a graph showing the relationship between the amount of untreated solution and the elapsed time when 120 L of plating solution is passed through the ion exchange resin at a circulation rate of 2 L / min, in a case where an ion removal step using an ion exchange resin is included to remove ions of metals other than Cr. FIG. 6 is a graph showing the relationship between the concentrations of various ions other than Cr and the elapsed time when 120 L of plating solution is passed through the ion exchange resin at a circulation rate of 2 L / min, in a case where an ion removal step for removing ions of metals other than Cr using an ion exchange resin is included. As shown in Figures 5 and 6, under these conditions, theoretically 98% of the plating solution can be circulated in approximately 240 minutes. In addition, the concentrations of Ni and Zn ions reached approximately 0 ppm in approximately 240 minutes, and the exchange efficiency is considered to be close to 100%. [Explanation of symbols]

[0064] 1, 21, 31, 41: Plated object 2A, 2B, 22A, 22B, 32A, 32B: Anode 3, 23, 33: Cathode (jig) 4, 24, 34: Plating solution 5.25.35: Plating tank 10, 20, 30: Plating equipment D21, D31: Farthest position D22, D32: Positions closest to the electrodes d21, d22, d31, d32: Distance between poles

Claims

1. A method for producing a trivalent chromium plating product, comprising: a plating step of applying current to an object to be plated as a cathode in a trivalent chromium plating solution; and an ion removal step of removing ions of metals other than Cr, The ion removal step uses an ion exchange resin that removes ions of metals other than Cr, The method for producing a trivalent chromium plating product, wherein the plating film of the trivalent chromium plating product obtained by the method for producing a trivalent chromium plating product has a color difference ΔE from a hexavalent chromium plating film of less than 3.

5.

2. The plating film of the trivalent chromium plating product has a lightness difference ΔL value from the hexavalent chromium plating film of less than 3.5, a color characteristic a value of +2.0 to −2.0, and a color characteristic b value of +2.0 to −2.

0. The method for producing a trivalent chromium plating product according to claim 1.

3. The method for producing a trivalent chromium plated product according to claim 1, wherein the thickness of the plating film of the trivalent chromium plated product is 0.2 μm or more and 1 μm or less.

4. In the plating treatment step, The plating temperature is 30 to 65°C, The plating treatment pH is 3.0 to 4.2, Plating current density is 4 to 10 A / dm ２ The method for producing a trivalent chromium plating product according to claim 1,

5. In the plating treatment step, The plating time is 3 to 30 minutes, The plating process electrode distance is 200 to 500 mm, Plating treatment agitation: 5 to 100 L / min. ２ and The method for producing a trivalent chromium plated product according to claim 1, wherein the plating treatment electrode uses one or more selected from the group consisting of Ti, Pt, Ir oxide, and Ta.

6. In the plating treatment step, The plating temperature is 50 to 56°C, The plating treatment pH is 3.0 to 3.8, Plating current density is 5 to 8 A / dm ２ and The plating time is 3 to 10 minutes, The plating process electrode distance is 250 to 350 mm, Plating treatment agitation: 5 to 100 L / min. ２ and The method for producing a trivalent chromium plated product according to claim 1, wherein the plating treatment electrode uses one or more selected from the group consisting of Ti, Pt, Ir oxide, and Ta.

7. A trivalent chromium plating product obtained by the method for producing a trivalent chromium plating product according to any one of claims 1 to 6, The plating film of the trivalent chromium plating product is characterized in that the color difference ΔE from the hexavalent chromium plating film is less than 2.

0.

8. The plating film of the trivalent chromium plating product has a brightness difference ΔL value from the hexavalent chromium plating film of less than 2.0, The trivalent chromium plating product according to claim 7, wherein the color characteristics are an a value of +2.0 to -2.0 and a b value of +2.0 to -2.

0.

9. The trivalent chromium plating product according to claim 7, wherein the thickness of the plating film of the trivalent chromium plating product is 0.2 μm or more and 1 μm or less.

10. The trivalent chromium plating product has an L value of 65 to 90, a lightness difference ΔL value from the hexavalent chromium plating film is less than 2.0, an a value of +0.5 to -1.0, and a b value of +1.0 to -1.

5. The trivalent chromium plating product according to claim 7.

Images