JP2007002274A - Zinc-nickel alloy plating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zinc-nickel alloy plating method where deterioration in a plating liquid is suppressed, and a long term operation is possible. <P>SOLUTION: The zinc-nickel alloy electroplating method uses a zinc-nickel based alloy plating liquid with the pH of ≥13 comprising zinc ions, nickel ions, a nickel complexing agent such as amines, and an alkali component(s). In the plating method, a cathode tank, an anode tank stored with an anode liquid as an alkali component-containing solution are separated with a diaphragm such as an ion exchange membrane, the alkali component(s) is added to the anode liquid, and the concentration of the alkali component(s) in the cathode liquid is controlled. In this invention, it is possible that the amount of the alkali component(s) to be supplied to the anode liquid is controlled with the amount of electric current as an index and the pH of the plating liquid is held to ≥13, the anode plate may be C, Fe, Cr, Ni or their alloys, and the plating liquid can further comprise at least one kind selected from the group consisting of brighteners, lubricating agents, reducing agents and surfactants. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface treatment technique using a zinc-nickel alloy plating bath having a pH of 13 or more, and in particular, a zinc-nickel alloy capable of forming a zinc-nickel alloy plating film stably for a long time without deterioration of the plating solution. The present invention relates to a plating method.

Zinc-nickel alloy plating has excellent corrosion resistance compared to other zinc-based plating, so it is widely used for automotive parts, especially engine parts placed in high-temperature environments and parts that require high corrosion resistance. ing.
Conventional zinc-nickel alloy plating baths with a pH of 13 or more dissolve zinc and / or nickel using an appropriate nickel complexing agent to deposit metal zinc and metal nickel on the plating film. The nickel content in the plating film was adjusted by selecting. As the complexing agent, for example, JP-A-62-287092 and JP-A-06-173073 describe amines and their reaction products. However, when the amine complexing agent is used in a zinc-nickel alloy plating bath having a pH of 13 or higher, the complexing agent is oxidized and decomposed in the vicinity of the anode plate during energization, and the plating solution is pumped out during plating. Decomposition of the complexing agent is caused by the high concentration of alkali added to make up for the component. As a result, the solubility of zinc and / or nickel changes, or the plating solution deteriorates due to the influence of deteriorated substances generated from the complexing agent itself, and the current efficiency gradually decreases compared to the start of work, and the plating film thickness decreases. Various problems such as a decrease in the nickel content in the plating film and a decrease in the gloss of the plating film occur.

On the other hand, European Patent EP1102875B1 proposes a zinc-nickel alloy plating method in which an ion exchange membrane is provided between electrodes and an alkaline catholyte (plating solution) is used. However, in this method, an acidic solution such as sulfuric acid is used as the anolyte, and a high concentration of alkali is added to the catholyte to replenish the plating solution in order to protect the expensive anode made of platinum-plated titanium. Inevitably, the plating solution cannot be prevented from deteriorating. Furthermore, when the diaphragm is damaged, the acidic solution on the anode side and the alkaline solution on the cathode side may mix and cause a chemical reaction, leading to a major accident. In the case of this method, the anolyte and the catholyte must be managed separately, and are inferior in industrial use.
JP-A-62-287092 Japanese Patent Laid-Open No. 06-173073 European Patent EP1102875B1 Specification

As described above, in the prior art, since there is no industrially fundamental solution for stabilizing the plating solution of zinc-nickel alloy plating, the plating solution is partially discarded and renewed in the actual operation process. Is dealing with these problems, and has a great impact on the global environment.
In recent years, in the field of zinc-nickel alloy plating baths, the nickel content in the plating film is maintained at 10% to 15% to improve the corrosion resistance. The nickel complexing agent that can achieve the above nickel content is limited, and therefore, it may be necessary to use a nickel complexing agent that is weak against alkalis and oxidation and has a problem in stability. In view of the above, there is a need for a technique that satisfies the safety of the plating bath in industrial implementation of a zinc-nickel alloy plating bath having a pH of 13 or higher, suppresses environmental load, and can be operated continuously and stably.

The inventors changed the size of the anode plate with respect to the same amount of plating solution, changed the anode current density and performed electrolysis for a long time (20 ° C., 50 hours), and then plated with this plating solution. The nickel content of the rice was comparatively measured. As a result, the nickel content was obviously different due to the difference in anode current density. That is, when the anode current density was large (5 A / dm ² ), the nickel content was 10-15%, and when the anode current density was small (1 A / dm ² ), the nickel content was 4-6%. From this, it was considered that during the plating operation, various reactions occur at the anode and in the vicinity thereof, and as a result, the solubility of nickel changes or the plating solution deteriorates to lower the nickel content.

In addition, the present inventors prepared several types of plating solutions with different alkali component concentrations, respectively, performed a hull cell plating test using the plating solutions immediately after preparation and after standing for a long time, and compared plating gloss. . When a plating solution having a high alkali component concentration (sodium hydroxide concentration 200 g / L) is used after being left for 192 hours, the current of the Hull cell plate plated with Hull cell for 2A-20 minutes is compared with the case where the plating solution before being left is used. Gray koge was observed at a density of 6 A / dm ² or more. On the other hand, when a plating solution with a low alkali component concentration (sodium hydroxide concentration 100 g / L) is used, there is no significant difference in gloss even when the hull cell plate is plated for 2A-20 minutes before and after being left for a long time. It was. Therefore, it was considered that the influence of strong alkali was also a major cause of deterioration.
As described above, the present inventors have intensively studied to enable continuous industrial operation of zinc-nickel alloy plating, and most of the causes of aging of the plating solution are oxidative decomposition of the complexing agent at the anode. It was found that the complexing agent was decomposed by the high-concentration alkali component during the replenishment of the alkali component, the anode and the cathode were isolated, the alkali was added to the anolyte, and the resulting catholyte was managed as a result. Has been solved, and the method of the present invention has been invented in which a plating film in a stable state can be obtained industrially.

The present invention is a zinc-nickel alloy electroplating method using a zinc-nickel alloy plating solution (catholyte) having a pH of 13 or more, which contains zinc ions, nickel ions, a nickel complexing agent, and an alkali component. The cathode tank containing the catholyte and the anode tank containing the anolyte, which is an alkali component-containing solution, are separated by a diaphragm capable of moving component ions and electrons, and the alkali component is added to the anolyte to add the alkali component of the catholyte. The present invention relates to a plating method for controlling the concentration.
The nickel complexing agent in the plating solution preferably contains at least one selected from the group of amines and other nitrogen-containing compounds.
In the method of the present invention, the total amount of alkali replenished to the anolyte can be adjusted using the amount of current passed between the anode and the cathode as an index, and the catholyte can be maintained at a pH of 13 or more.
The diaphragm may be an ion exchange membrane.
The anode plate in the anode tank may be composed of one selected from the group consisting of C, Fe, Cr, Ni, and alloys thereof.
The plating solution may further contain at least one selected from the group of brighteners, smoothing agents, reducing agents, and surfactants.

  The zinc-nickel alloy electroplating method using the zinc-nickel alloy plating solution (catholyte) having a pH of 13 or more according to the present invention suppresses the deterioration of the plating solution and enables long-term operation with a stable plating solution component. It was. Furthermore, in the method of the present invention, the management of the alkali component concentration of the plating solution is industrially easy. The nickel content in the plating film obtained by the method of the present invention can be maintained at a stable rate.

A schematic diagram of an example of an apparatus that can be used in the present invention is shown in FIG.
The cathode tank (10) containing the zinc-nickel alloy plating solution (catholyte) (2) of the present invention and the anode tank (6) containing the anolyte (3) are membranes (4) capable of moving component ions and electrons. ).
About catholyte (plating solution);
The catholyte (2) in FIG. 1 is a solution containing zinc ions, nickel ions, a nickel complexing agent and an alkali component and having a pH of 13 or more, and the plating object (1) is immersed therein.
For the catholyte having a pH of 13 or higher, a commonly used aqueous solution of an alkaline component can be used. Examples of the alkali component include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. The alkali component contained in the catholyte and the following alkali component added to the anolyte may be the same or different, but during the plating operation, the cation contained in the anolyte (3) passes through the diaphragm (4) to form the catholyte ( 2) The same component is preferred because it moves into and controls the alkali component concentration of the catholyte.
The concentration of the alkali component in the catholyte may be in a range where the pH is 13 or more, and the preferred range varies depending on the alkali component species. It is. If it is less than 50 g / L, the adhesion with the base material of the plating film deteriorates and the uniform electrodeposition deteriorates. On the other hand, if it exceeds 150 g / L, the leveling of the plating film deteriorates.

Examples of the nickel complexing agent contained in the catholyte (2) of the present invention include amines and reactants thereof, and nitrogen-containing compounds and reactants thereof. As the above amines: triethanolamine, ethylenediamine, pentaethylenehexamine, diaminopropane, diethylenetriamine, ethylaminoethanol, aminopropylethylenediamine, bisaminopropylpiperazine, triethylenetetramine, tetraethylenepentamine, hexamethylenetetramine, isopropanolamine, amino Aliphatic amines such as alcohol, hydroxyethylaminopropylamine, tetramethylpropylenediamine, dimethylaminopropylamine; aliphatic amine polymers such as polyaminesulfone, polyethyleneimine, polyalkylenepolyamine, and polyallylamine;
Structural formula 1

（但し、Ｒ¹，Ｒ²は水素又はＣが１０以下のアルキルであり、ｎは１以上である。）で表されるポリマー、下記構造式２

Wherein R ¹ and R ² are hydrogen or C is alkyl having 10 or less, and n is 1 or more.

（但し、Ｒ¹，Ｒ²は水素、メチル、エチル、ブチル又はイソブチルであり、Ｒ³はＣＨ₂、Ｃ₂Ｈ₄又はＣ₃Ｈ₆でありｎは１以上である。）で表されるポリマー、下記構造式３

Wherein R ¹ and R ² are hydrogen, methyl, ethyl, butyl or isobutyl, R ³ is CH ₂ , C ₂ H ₄ or C ₃ H ₆ and n is 1 or more. Polymer, structural formula 3 below

（但し、Ｒ¹，Ｒ²，Ｒ³，Ｒ⁴は水素又はＣが５以下のアルキルであり、ＹはＳ又はＯであり、Ｘは無機陰イオンであり、ｎは１以上である。）で表されるポリマー、下記構造式４

(However, R ¹ , R ² , R ³ , R ⁴ are hydrogen or C is alkyl having 5 or less, Y is S or O, X is an inorganic anion, and n is 1 or more.) The polymer represented by the following structural formula 4

（Ｒ¹，Ｒ²，Ｒ³，Ｒ⁴：水素、Ｃが５以下のアルキル、Ｙ：Ｓ又はＯ，Ｘ：無機陰イオン、ｍおよびｎは１以上）で表されるポリマー、又は下記構造式５

(R ¹ , R ² , R ³ , R ⁴ : hydrogen, C is alkyl having 5 or less, Y: S or O, X: inorganic anion, m and n are 1 or more), or the following structure Formula 5

（Ｒ¹，Ｒ²，Ｒ³，Ｒ⁴：水素、メチル、エチル、イソプロピル、２−ヒドロキシルエチル−ＣＨ₂ＣＨ₂（ＯＣＣＨ₂ＣＨ₂）_xＯＨ（Ｘは０から６）、又は２一ヒドロキシルエチル−ＣＨ₂ＣＨ₂（ＯＣＨ₂ＣＨ₂）_xＯＨ（Ｘは０から６）から選ばれたもの、Ｒ⁵：（ＣＨ₂）₂−Ｏ−（ＣＨ₂）₂、（ＣＨ₂）₂−Ｏ−（ＣＨ₂）₂−Ｏ−（ＣＨ₂）₂、ＣＨ₂−ＣＨＯＨ−ＣＨ₂−Ｏ−ＣＨ₂−ＣＨＯＨ−ＣＨ₂から選ばれたもの、ｎ：１以上、Ｙ：Ｓ又はＯ，Ｚ：１〜５）で表されるポリマー、これらのコポリマー、ブロックポリマーが挙げられる。
その他の含窒素化合物として、イミダゾール、ピコリン、ピペラジン、メチルピペラジン、モルホリン、ベンジルピリジニウムカルボキシレート、ポリアミド、チオアセトアミド、チオアセトアミド誘導体、チオ尿素、チオ尿素誘導体（アルキル化物等）、尿素、尿素誘導体（アルキル化物等）、ポリアリルアミン等及びこれら同士の反応物が挙げられる。
又、反応物としては、上記アミン類又はその他の含窒素化合物と、グリシジル化合物若しくはジエチルエーテル化合物との反応物；上記化合物のメチル化若しくはエチル化誘導体又は誘導体同士の反応物；等が挙げられる。
アミン類と反応物を生成するグルシジル化合物として、エピクロルヒドリン、アリルグリシジルエーテル、ブチルグリシジルエーテル、フェニルグリシジルエーテル、グリシドール、メチルグリシジルエーテル、２−エチルヘキシルグリシジルエーテル、グリセロールジグリシジルエーテル、エチレングリコールジグリシジルエーテル、セカンダリーブチルフェノールジグリシジルエーテル、グリシジルメタクリレート等が挙げられる。

(R ¹ , R ² , R ³ , R ⁴ : hydrogen, methyl, ethyl, isopropyl, 2-hydroxylethyl-CH ₂ CH ₂ (OCCH ₂ CH ₂ ) _x OH (X is 0 to 6), or 2 monohydroxyl ethyl _{-CH 2 CH 2 (OCH 2 CH} 2) x OH (X is from 0 6) those selected _{^{from, R 5: (CH 2)}} 2 -O- (CH 2) 2, (CH 2) 2 - O— (CH ₂ ) ₂ —O— (CH ₂ ) ₂ , CH ₂ —CHOH—CH ₂ —O—CH ₂ —CHOH—CH ₂ , n: 1 or more, Y: S or O, And polymers represented by Z: 1 to 5), copolymers thereof, and block polymers.
Other nitrogen-containing compounds include imidazole, picoline, piperazine, methylpiperazine, morpholine, benzylpyridinium carboxylate, polyamide, thioacetamide, thioacetamide derivatives, thiourea, thiourea derivatives (alkylated products, etc.), urea, urea derivatives (alkyl) Compound), polyallylamine and the like, and a reaction product between them.
Examples of the reactant include a reaction product of the above amines or other nitrogen-containing compounds and a glycidyl compound or a diethyl ether compound; a methylated or ethylated derivative of the above compound or a reaction product of derivatives thereof;
Examples of glycidyl compounds that generate a reaction product with amines include epichlorohydrin, allyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, glycidol, methyl glycidyl ether, 2-ethylhexyl glycidyl ether, glycerol diglycidyl ether, ethylene glycol diglycidyl ether, secondary Examples thereof include butylphenol diglycidyl ether and glycidyl methacrylate.

The catholyte of the present invention may contain at least one selected from the group of brighteners, smoothing agents, reducing agents and surfactants.
Examples of the brightener and smoothing agent include aromatic aldehydes such as anisaldehyde, vanillin, heliotropin, and veratraldehyde, or substituted methyl groups thereof, ethylene glycol, polyethylene glycol, acetylenic alcohol, coumarin, pyridine, and quinoline. These derivatives and other known brighteners for galvanizing can be mentioned.
Examples of the reducing agent include ascorbic acid, citric acid, gallic acid, catechol, resorcinol, and bisulfite.
Examples of the surfactant mainly include nonionic surfactants. For example, polyoxyalkylene alkyl ether (or ester), polyoxyalkylene phenyl (or alkylphenyl) ether, polyoxyalkylene naphthyl (or alkyl naphthyl). Examples include ethers, polyethylene glycol fatty acid esters, polyoxyalkylene alkylamines, polyoxyalkylene condensate adducts of ethylenediamine, and polyoxyalkylene aliphatic amides.
In the catholyte (2) containing zinc ion, nickel ion and nickel complexing agent of the present invention, zinc oxide is dissolved with a caustic soda solution, and nickel sulfate is dissolved with water in a separate tank. After mixing the agent, it can be manufactured by mixing with a caustic soda solution containing zinc ions.

An anode plate (5) is arranged inside the anode tank (6) in FIG. 1, and one anode tank (6) may be provided for the object to be plated. Also, as shown in FIG. Two may be arranged on both sides of (1).
The anode plate of the present invention can be made of various materials, but is preferably insoluble in an alkaline component solution. For example, it is possible to use an industrially inexpensive and easily available metal member selected from the group of C, Fe, Cr, Ni and alloys thereof, such as nickel plate, iron plate, stainless steel plate, carbon Electrode. Among them, an iron plate is preferable when cost is considered in industrial operation.
The alkali component concentration of the anolyte (3) may be controlled by adding an alkali component or an alkali component solution directly to the anode tank (6). Further, the anode tank (6) and another auxiliary tank (8) filled with the alkaline component solution are connected by a conduit through the pump (7), and the alkali solution is passed from the auxiliary tank (8) while circulating the anolyte (3). By supplying the component solution, the alkali component concentration of the anolyte may be kept within a certain range. Further, as shown in FIG. 1, a plurality of anode tanks may be connected by a conduit, and the anolyte may be circulated.
Examples of the alkaline component that constitutes the anolyte or is added to the anolyte include the same ones as mentioned for making the catholyte into a solution having a pH of 13 or more. In the case of sodium hydroxide, for example, the concentration of the aqueous solution constituting the anolyte is preferably 50 to 250 g / L, more preferably 100 to 200 g / L. The alkali component replenished to the anode tank or the auxiliary tank may be a simple substance or a solution, but is preferably an aqueous solution. In the case of sodium hydroxide, for example, the concentration of the aqueous solution for replenishment is preferably 100 to 500 g / L, more preferably 200 to 250 g / L.

  The total amount of alkali supplied to the anolyte may be adjusted using the amount of current applied between the anode and the cathode as an index. That is, the amount of current supplied between the anode and the cathode is made proportional to the total amount of alkali supplied to the anolyte at a constant rate. The increased components in the anolyte are ionized by the current and pass through the diaphragm to compensate for the alkaline components in the catholyte (plating solution) lost by plating and pumping. As a result, the alkali component concentration of the catholyte (plating solution) can be controlled and maintained at pH 13 or higher.

  The diaphragm (4) used in the present invention is a porous film or partition wall that can pass alkali such as sodium, potassium, lithium ion and the like. An ion exchange membrane is preferred as the diaphragm. The diaphragm is not particularly limited and may be a commercially available product, and is preferably a cation exchange membrane. Specifically, for example, CR61ZL-386, CR61ZL-389 (manufactured by Yuasa Ionics Co., Ltd.), trade names Nafion 112, 117, 324, 350, 424, 551, 1110, 1135 (manufactured by DuPont Co., Ltd.), Product names Neoceptor CM1, CM2, CMS, CMX, CMB (above Tokuyama Co., Ltd.), product names Aciplex S-1112, S-1104, S-1004, S-1002 (above Asahi Kasei Kogyo Co., Ltd.) Can be mentioned. The diaphragm may be reinforced with a structure such as a punching plate that does not impede its function.

Examples of the method of the present invention will be described below. Unless otherwise specified, a 1 dm ² panel (SPCC) was used as a test piece used as a cathode for plating, and an iron plate (length 10 cm × width 5 cm × thickness 1 mm) was used as an anode plate. Further, the cathode cell and the anode cell were separated by a Tokuyama cation exchange membrane trade name Neoceptor CM1 (area 150 cm ² ) unless otherwise specified. The nickel eutectoid rate is measured using an energy dispersive fluorescent X-ray analyzer, and its unit is% by weight.
In Example 1 and Comparative Example 1 below, the relationship between alkali component replenishment from the anolyte and the amount of energization was examined.
Example 1
500 mL of a 134.4 g / L sodium hydroxide solution was used as the anolyte, and 2 L of a plating solution having the following bath composition 1 was used as the catholyte.
The plating method was based on the factory operation line, and a total of 20 AH / L (ampere hour per liter) was applied at a temperature of 20 ° C. During energization, the test piece was replaced every 4 AH / L, and the sodium hydroxide concentrations in the cathode and anode tanks were measured. The results are shown in Table 1.
Bath composition 1;
Metal zinc ion; 8 g / L
Nickel ion; 1.6 g / L
Sodium hydroxide; 125.6 g / L
Complexing agent (Nippon Surface Chemical Co., Ltd., trade name NI-T, component composition; reaction product of aliphatic amine and glycidyl compound 20% by weight); 120 g / L
The amount of sodium hydroxide in the anode tank was 40 g at the end compared with 67.2 g before the start of the test, a net decrease of 27.2 g, and the sodium hydroxide concentration of the anolyte was 80 g / L. On the other hand, the sodium hydroxide concentration of the catholyte was kept almost constant at 126.4 g / L at the end, compared with 125.6 g / L before the start of the test. The amount of sodium hydroxide supplied from the anolyte through the diaphragm to the catholyte (decreasing amount from the anolyte) was about 1.4 g / AH per energizing amount. The same test was performed four times, but there was no significant difference in the amount of sodium hydroxide supplied and was between 1.0 and 2.0 g / AH (0.99 g / AH, 1.6 g / AH, 1. 96 g / AH).

Comparative Example 1
As an anolyte, 500 mL of a 50 g / L concentration sulfuric acid solution was used, and 2 L of the plating solution having the above bath composition 1 was used as a catholyte. In the same manner as in Example 1, the cathode tank and the anode tank were separated by a cation exchange membrane, and the test piece was replaced every 4 AH / L by energization, and the sulfuric acid concentration in the anode tank was measured. The results are shown in Table 1.
The amount of sulfuric acid in the anode tank was 18.8 g at the end compared to 25 g before the start of the test, a net 6.2 g decrease, and the sulfuric acid concentration of the anolyte was 37.7 g / L. On the other hand, the sodium hydroxide concentration of the catholyte unilaterally decreased to 128.8 g / L before the start of the test and 108.8 g / L at the end.

In Example 2 and Comparative Example 2 below, the hull cell test was performed while adjusting the catholyte (plating solution) component during the plating operation. In Table 2, the Hull cell pattern before energization (plated surface appearance of the test piece used as the cathode in the Hull cell plating test) and the nickel eutectoid rate were 2A-20 minutes and 0.2A-20 minutes Hull cell plating. It is a value about things. The nickel eutectoid rate was measured at a current density of 3 A / dm ^{2 in} the test piece.
Example 2
500 mL of a 130.0 g / L concentration sodium hydroxide solution was used as the anolyte, and 2 L of a plating solution having the following bath composition 2 was used as the catholyte. Zinc dissolved in sodium hydroxide solution (sodium hydroxide concentration: 600 g / L, metallic zinc concentration: 169 g / L) in an amount almost equal to the precipitation amount every 4 AH / L, with a current of 20 AH / L at a temperature of 20 ° C. Nickel in a nickel-ethylenediamine complex solution (nickel concentration: 100 g / L) was supplied to the cathode chamber. After energization of 20 AH / L, trade names “ZN-202A” 8 mL / L and “ZN-202B” 8 mL / L (both manufactured by Nippon Surface Chemical Co., Ltd., “ZN-202A” component composition; water-soluble) (22.9% functional epoxy resin) “ZN-202B” component composition; 1.0% by weight aromatic aldehyde derivative) was added, and a Hull cell plating test (2A-20 minutes, 0.2A-20 minutes) was performed. Moreover, the complexing agent concentration of the plating solution energized with 20 AH / L was analyzed. The results are shown in Table 2.
Bath composition 2;
Metal zinc ion; 8 g / L
Nickel ion: 1.6 g / L
Sodium hydroxide; 120 g / L
Complexing agent (NI-T manufactured by Nippon Surface Chemistry Co., Ltd.); 120 g / L

Comparative Example 2
The same operation as in Example 2 was performed except that 2 L of the plating solution having the above bath composition 2 was used as the catholyte and 500 mL of a 50.0 g / L aqueous phosphoric acid solution was used as the anolyte. The results are shown in Table 2.
Comparative Example 3
The same operation as in Example 2 was performed, except that 2 L of the plating solution having the above bath composition 2 was used as the catholyte and the anode and the cathode were not separated. The results are shown in Table 2.
Comparative Example 4
Example 2 except that ² L of the plating solution having the above-described bath composition 2 was used as the catholyte, and the cathode and anode vessels were separated by a filter cloth (fiber trade name “pyrene” (polypropylene), thickness 1 mm, area 150 cm ² ). The same operation was performed. The results are shown in Table 2.
From Table 2 below, in Example 2, the reduction amount of the complexing agent after energization was small, gloss was observed on the entire surface of the Hull cell pattern, and the nickel eutectoid rate was maintained at the initial state. In Comparative Example 2 in which a phosphoric acid aqueous solution was used for the anolyte separated from the catholyte by the cation exchange membrane, the low current portion of the hull cell pattern of the test piece was insufficiently plated (unsatisfactory), and the high current portion was damaged. Observed. Further, the anode plate was corroded. Similar results were obtained in Comparative Example 3 in which no cation exchange membrane was used and 4 in which filter cloth was used.

Example 3
500 mL of a 130.0 g / L concentration sodium hydroxide solution was used as the anolyte, and 2 L of a plating solution having the following bath composition 3 was used as the catholyte. 20 AH / L energized at a temperature of 20 ° C., and dissolved in a sodium hydroxide solution (sodium hydroxide concentration 600 g / L, metal zinc concentration 169 g / L) in an amount almost equal to the precipitation amount every 4 AH / L. Zinc and nickel in a nickel-triethylenetetramine complex solution (concentration 100 g / L) were replenished to the cathode cell. After energizing 20 AH / L, the product names “ZN-203A” 12 mL / L and “ZN-203B” 6 mL / L (both manufactured by Nippon Surface Chemical Co., Ltd., “ZN-203A” component composition; water-soluble) Epoxy resin 19.5% by weight) “ZN-203B” component composition; aromatic amine derivative 2% by weight) was added, and a Hull cell plating test (2A-20 minutes, 0.2A-20 minutes) was performed. The complexing agent concentration of the plating solution energized with 20 AH / L was analyzed. The results are shown in Table 3.
Bath composition 3;
Metal zinc ion; 8 g / L
Nickel ion; 1.3 g / L
Sodium hydroxide; 120 g / L
Complexing agent (Nippon Surface Chemical Co., Ltd., trade name “NI-W” component composition; reaction product of aliphatic amine and glycidyl compound 40% by weight); 120 g / L

Comparative Example 5
The same operation as in Example 3 was performed except that 2 L of the plating solution having the above-described bath composition 3 was used as the catholyte and 500 mL of a 50.0 g / L sulfuric acid aqueous solution was used as the anolyte. The results are shown in Table 3.
Comparative Example 6
The same operation as in Example 3 was performed except that 2 L of the plating solution having the above bath composition 3 was used as the catholyte and the anode and the cathode were not separated. The results are shown in Table 3.
Comparative Example 7
The same operation as in Example 3 was performed, except that 2 L of the plating solution having the above-described bath composition 3 was used as the catholyte, and the cathode cell and the anode cell were separated by the filter cloth used in Comparative Example 4. The results are shown in Table 3.

  From Table 3 below, in Example 3, the decrease amount of the complexing agent after energization is small, gloss is observed on the entire surface of the Hull cell pattern, and the nickel eutectoid rate can maintain the initial state. In Comparative Example 5 where an aqueous sulfuric acid solution was used for the anolyte separated from the catholyte by the cation exchange membrane, the low current part of the hull cell pattern of the test piece was insufficiently plated (unsatisfactory), and the high current part was observed by kogation. It was. Further, the anode plate was corroded. Similar results were obtained in Comparative Example 3 in which no cation exchange membrane was used and 4 in which filter cloth was used.

1 is a schematic view of an example of a plating apparatus that can be used in the present invention used in Example 1. FIG.

Claims (6)

  A zinc-nickel alloy electroplating method using a zinc-nickel alloy plating solution (catholyte) having a pH of 13 or higher, which contains zinc ions, nickel ions, a nickel complexing agent and an alkali component, and contains the catholyte. The catholyte and the anolyte are not mixed with each other between the cathode tank and the anolyte containing the alkaline component-containing solution, and separated by a diaphragm capable of transferring only component ions and electrons, and the anolyte A plating method in which the alkali component concentration is controlled by adding an alkali component to the cathode.   The plating method according to claim 1, wherein the nickel complexing agent in the plating solution contains at least one selected from the group of amines and other nitrogen-containing compounds.   The plating method according to claim 1 or 2, wherein the amount of an alkaline component replenished to the anolyte is adjusted using the amount of current flowing between the anode and the cathode as an index, and the catholyte is maintained at pH 13 or more.   The plating method according to claim 1, wherein the diaphragm is an ion exchange membrane.   The plating method according to any one of claims 1 to 4, wherein the anode plate in the anode tank is composed of one selected from the group consisting of C, Fe, Cr, Ni, and alloys thereof.   The plating method according to claim 1, wherein the plating solution further contains at least one selected from the group consisting of a brightener, a smoothing agent, a reducing agent, and a surfactant.

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