Alkaline zinc-nickel alloy plating solution and zinc-nickel alloy barrel plating method using the same

Abstract

The present invention aims to provide a zinc-nickel alloy barrel plating solution that makes it possible to achieve efficient zinc-nickel alloy plating without occurrence of non-deposition even at low current density, when performing zinc-nickel alloy barrel plating on parts with large surface areas, such as small fastener screws, knurled nuts, and pop rivets used in electric vehicles; and a zinc-nickel alloy plating method that uses fewer chemicals and is easier to manage. An aspect of the present invention is a composition for zinc-nickel alloy barrel plating, namely an alkaline zinc-nickel alloy plating solution that contains zinc ions, nickel ions, sodium ions, hydroxide ions, and an amine-based chelating agent that forms complexes with nickel, and is free of nitrogen-containing heterocyclic compounds.

Description

Technical Field

[0001] The present invention relates to electroplating; in particular, it relates to a zinc-nickel alloy plating solution used for barrel plating and to a zinc-nickel alloy plating method.Background Art

[0002] With the shift toward carbon neutrality and the increasing electrification of vehicles, high corrosion resistance is required for small fasteners such as screws, knurled nuts, and pop rivets; to meet this requirement, zinc-nickel alloy plating has come into use.

[0003] However, since these parts have large surface areas, the current density used in barrel plating often becomes low. Furthermore, due to the characteristics of barrel plating equipment, the current is intermittently applied; consequently, the workpiece to be plated occasionally becomes an anode, causing the plated film to re-dissolve and reducing plating efficiency. Especially at low current density, there has been a problem in which no plating is deposited. Also, because the number of plating solution components to be controlled may be large or the component concentrations may be high, the burden on wastewater treatment, the complexity of component concentration control, and high costs have been points to improve.Summary of Invention

[0004] The present invention aims to provide a zinc-nickel alloy barrel plating solution that makes it possible to achieve efficient zinc-nickel alloy plating without occurrence of non-deposition even at low current density, when performing zinc-nickel alloy barrel plating on parts with large surface areas, such as small fastener screws, knurled nuts, and pop rivets used in electric vehicles; and a zinc-nickel alloy plating method that uses fewer chemicals and is easier to manage.

[0005] To achieve the above object, an aspect of the present invention is a composition for zinc-nickel alloy barrel plating, namely an alkaline zinc-nickel alloy plating solution that contains zinc ions, nickel ions, sodium ions, hydroxide ions, and an amine-based chelating agent that forms complexes with nickel, and is free of nitrogen-containing heterocyclic compounds. The reason is that by not including nitrogen-containing heterocyclic compounds in the plating solution, the content of carbon, which is noble in redox potential, in the plated film is suppressed; when the workpiece to be plated is not supplied with current or becomes an anode momentarily, it has been confirmed that the re-dissolution of zinc in the deposited plating film into the plating solution is difficult. By preventing this re-dissolution, it is possible to perform efficient barrel plating even at low current density; this led to the present invention. Moreover, by reducing the zinc concentration, nickel concentration, and chelating agent concentration, the uniform deposition can be improved, and the plating thickness at low current density portions can be increased. Furthermore, the burden on wastewater treatment can also be reduced.

[0006] Another aspect of the present invention is a plating method for performing zinc-nickel alloy barrel plating using an alkaline zinc-nickel alloy plating solution containing zinc ions, nickel ions, sodium ions, hydroxide ions, and an amine-based chelating agent that forms complexes with nickel, and not containing nitrogen-containing heterocyclic compounds.

[0007] Yet another aspect of the present invention may be as follows: [1] An alkaline zinc-nickel alloy plating solution comprising zinc ions, nickel ions, sodium ions, hydroxide ions, and an amine-based chelating agent, the alkaline zinc-nickel alloy plating solution being free of nitrogen-containing heterocyclic compounds. [2] The zinc-nickel alloy plating solution according to [1] above, wherein a content of zinc ions is 2 g / L or more and 7 g / L or less. [3] The zinc-nickel alloy plating solution according to [1] or [2] above, wherein a content of nickel ions is 0.4 g / L or more and less than 1.5 g / L. [4] The zinc-nickel alloy plating solution according to any one of [1] to [3] above, wherein a content of the amine-based chelating agent is 5 g / L or more and 100 g / L or less. [5] The zinc-nickel alloy plating solution according to any one of [1] to [4] above, wherein the solution contains sodium hydroxide at 50 g / L or more and 85 g / L or less. [6] The alkaline zinc-nickel alloy plating solution according to any one of [1] to [5] above, further comprising 8 mg / L or more and 100 mg / L or less of calcium ions and / or 2 mg / L or more and 40 mg / L or less of magnesium ions. [7] The alkaline zinc-nickel alloy plating solution according to any one of [1] to [6] above, further comprising a water-soluble cationic polymer. [8] The alkaline zinc-nickel alloy plating solution according to [7] above, wherein a content of the water-soluble cationic polymer is greater than 0.1 g / L and 10 g / L or less. [9] A zinc-nickel alloy barrel plating method comprising plating a workpiece to be plated using the zinc-nickel alloy plating solution according to any one of [1] to [8] above.

[0008] According to the present invention, it is possible to provide a zinc-nickel alloy plating solution that enables efficient barrel plating when plating small fastener screws, knurled nuts, pop rivets, and the like, no non-deposition occurs even at low current density; and a zinc-nickel alloy plating method that uses fewer chemicals and is easier to manage.Brief Description of Drawings

[0009] Fig. 1 is a diagram showing the results of Example 4 and Example 6. Fig. 2 is a graph showing the film thickness distribution of Example 4 and Example 6. Fig. 3 is a diagram showing the plated appearance in Example 5 and Reference Example 1. Description of Embodiments

[0010] Next, embodiments of the present invention are explained. The embodiments of the present invention described below are examples of plating solutions and plating methods to embody the technical concept of the present invention; the technical concept of the present invention is not limited to the specific compound names described below. Various modifications can be made within the technical scope described in the claims.

[0011] The zinc-nickel alloy plating solution according to an embodiment of the present invention is a plating solution used for electroplating; it is an alkaline aqueous solution mainly composed of sodium hydroxide and contains zinc ions, nickel ions, and an amine-based chelating agent that forms complexes with nickel, and does not contain nitrogen-containing heterocyclic compounds. In the plating method using this plating solution, the contents of the zinc ions, nickel ions, and chelating agent are preferably adjusted so that the nickel co-deposition ratio is 12 to 18 wt%; more preferably, it is adjusted so that the ratio is 12 to 15 wt%.

[0012] In a conventional zinc-nickel alloy plating solution, it is common to add water-soluble cationic polymers and nitrogen-containing heterocyclic compounds as brighteners to obtain dense and lustrous plated films. However, in the zinc-nickel alloy plating solution according to an embodiment of the present invention, it is characterized by not adding nitrogen-containing heterocyclic compounds.

[0013] Furthermore, to maintain the plating appearance at the initial stage of bath preparation of the plating solution, it is preferable to define the quality of the water used in the plating solution. Specifically, it is defined that the calcium ion content in the plating solution is 8 mg / L or more and 100 mg / L or less and / or the magnesium ion content is 2 mg / L or more and 40 mg / L or less. The calcium ion content is more preferably 15 mg / L or more and 85 mg / L or less.

[0014] The magnesium ion content is more preferably 2 mg / L or more and 30 mg / L or less.

[0015] The zinc-nickel alloy plating solution according to an embodiment of the present invention contains zinc ions. The content of zinc ions in the plating solution is preferably 2 g / L or more and 7 g / L or less, and more preferably 4 g / L or more and 6 g / L or less. As a zinc ion source, Na 2 [Zn(OH) 4 ], K 2 [Zn(OH) 4 ], ZnO, and the like may be cited. These zinc ion sources may be used alone or in combination of two or more.

[0016] The zinc-nickel alloy plating solution according to an embodiment of the present invention contains nickel ions. The content of nickel ions in the plating solution is preferably 0.4 g / L or more and 1.5 g / L or less, more preferably 0.4 g / L or more and 1.3 g / L or less, still more preferably 0.4 g / L or more and less than 1.0 g / L, and most preferably 0.6 g / L or more and 0.9 g / L or less. Examples of nickel ion sources include nickel sulfate. These metal ion sources may be used alone or in combination of two or more.

[0017] The zinc-nickel alloy plating solution according to an embodiment of the present invention contains sodium ions and hydroxide ions. Sodium ions and hydroxide ions may be contained as sodium hydroxide, or they may be contained from sources different from sodium hydroxide. When the plating solution contains sodium hydroxide, the content of sodium hydroxide is preferably 50 g / L or more and 85 g / L or less, and more preferably 55 g / L or more and less than 70 g / L.

[0018] Also, the content of sodium ions in the plating solution is preferably 28 g / L or more and 50 g / L or less, and more preferably 31 g / L or more and less than 40 g / L. The content of hydroxide ions in the plating solution is preferably 22 g / L or more and 35 g / L or less, and more preferably 24 g / L or more and less than 30 g / L.

[0019] The zinc-nickel alloy plating solution according to an embodiment of the present invention contains an amine-based chelating agent. Examples of amine-based chelating agents include alkylene amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine; alkylene oxide adducts of the above alkylene amines, such as ethylene oxide adducts and propylene oxide adducts; amino alcohols such as ethanolamine, diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, ethylenediaminetetra-2-propanol, N-(2-aminoethyl)ethanolamine, 2-hydroxyethylaminopropylamine; alkanolamine compounds such as N-(2-hydroxyethyl)-N,N',N'-triethylethylenediamine, N,N'-di(2-hydroxyethyl)-N,N'-diethylethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)propylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine; poly(alkyleneimine) obtained from ethylenimine, 1,2-propylenimine, and the like; poly(alkyleneamine) obtained from ethylenediamine, triethylenetetramine, and the like. The amine-based chelating agent preferably includes one or more selected from alkylene amine compounds, alkylene oxide adducts therof, and alkanolamine compounds. These amine-based chelating agents may be used alone or in combination of two or more. The content of the amine-based chelating agent in the plating solution is preferably 5 g / L or more and 100 g / L or less, and more preferably 30 g / L or more and 65 g / L or less.

[0020] The zinc-nickel alloy plating solution according to an embodiment of the present invention preferably further contains a water-soluble cationic polymer. Examples of water-soluble cationic polymers include (1) polyallylamines, such as copolymers of diallyldimethylammonium chloride and sulfur dioxide; polyamide-polyamines formed by condensation polymerization reactions, such as condensation products of ethylenediamine and epichlorohydrin, condensation products of dimethylaminopropylamine and epichlorohydrin, polyamine-polyurea resins such as condensation products of 3-dimethylaminopropylurea and epichlorohydrin and condensation products of bis(N,N-dimethylaminopropyl)urea and epichlorohydrin, and water-soluble nylon resins such as condensation products of N,N-dimethylaminopropylamine, an alkylenedicarboxylic acid, and epichlorohydrin; polyalkylene polyamines formed by condensation polymerization reactions, such as condensation products of diethylenetriamine or dimethylaminopropylamine with 2,2'-dichlorodiethyl ether, condensation products of dimethylaminopropylamine and 1,3-dichloropropane, condensation products of N,N,N',N'-tetramethyl-1,3-diaminopropane and 1,4-dichlorobutane, condensation products of N,N,N',N'-tetramethyl-1,3-diaminopropane and 1,3-dichloropropan-2-ol; and other polyamine compounds; (2) condensation polymerization products of dimethylamine, etc., and dichloroethyl ether. These water-soluble cationic polymers may be used alone or in combination of two or more. The content of the water-soluble cationic polymer in the plating solution is preferably greater than 0.1 g / L and 10 g / L or less, and more preferably greater than 0.1 g / L and 5 g / L or less.

[0021] The zinc-nickel alloy plating solution according to an embodiment of the present invention may further contain auxiliary additives. Examples of auxiliary additives include organic acids, silicates, and mercapto compounds. These auxiliary additives may be used alone or in combination of two or more. The content of auxiliary additives is preferably 0.01 to 50 g / L.

[0022] The zinc-nickel alloy plating solution according to an embodiment of the present invention may also contain a defoaming agent. Examples of defoaming agents include surfactants. These defoaming agents may be used alone or in combination of two or more. The content of the defoaming agent is preferably 0.01 to 5 g / L.

[0023] A representative example of the composition of the zinc-nickel alloy plating solution according to an embodiment of the present invention is shown in Table 1. The zinc-nickel alloy plating solution may also contain zinc-based plating chemicals used in commercially available alkaline baths, other than the contained substances in Table 1. Table 1Zinc Ion (g / L)Nickel Ion (g / L)Sodium Hydroxide (g / L)Amine-based Chelating Agent (g / L)Nitrogen-containing Heterocyclic Compound (g / L)Calcium Ion (mg / L)Magnesium Ion (mg / L)50.8654002510

[0024] When forming a plating using the zinc-nickel alloy plating solution according to an embodiment of the present invention, the temperature is preferably 15°C to 40°C, and more preferably 25°C to 35°C. The cathodic current density for zinc or zinc alloy plating is preferably 0.1 to 20 A / dm 2< , and more preferably 0.2 to 10 A / dm 2< .

[0025] Workpieces to be plated are not particularly limited and may be those commonly used in the technical field. For example, various metals such as iron, nickel, copper, zinc, aluminum, and alloys thereof may be used. There are no particular restrictions on shape; for example, it may be any articles including plate-shaped materials such as steel plates or plated steel plates, or shapes such as rectangular prisms, cylinders, tubes, spheres, and so forth. Specific examples of these articles include fasteners such as bolts, nuts, and washers; pipe components such as fuel pipes; cast iron components such as brake calipers and common rails; and other various items such as connectors, plugs, housings, sockets, and seat belt anchors.

[0026] For protecting the zinc-nickel alloy plating layer formed using the zinc-nickel alloy plating solution according to an embodiment of the present invention, it is possible to form an existing trivalent chromium conversion coating layer that does not contain hexavalent chromium. The plating method using the zinc-nickel alloy plating solution according to an embodiment of the present invention can use existing pretreatment and post-treatment processes.

[0027] Below, the invention will be described more specifically using Examples. Examples(Example 1)

[0028] Using the following alkaline zinc-nickel alloy plating bath (5 L), zinc-nickel alloy plating of about 8 µm thickness was performed on a panel (pickled steel sheet (SPHC-P steel sheet): 70 mm long×50 mm wide×1 mm thick). The cathodic current density was 4 A / dm 2< , and the anode current density was 8 A / dm 2< ; the plating bath temperature was 25°C; the plating time was 30 minutes; a nickel plate was used as the anode. After plating, the panel was rinsed in the following wash waters: [1st Rinse] A 100 mL portion of the plating solution diluted with 2 L of water for 60 s (room temperature) [2nd Rinse] A 10 mL portion of the plating solution diluted with 2 L of water for 60 s (room temperature) [3rd Rinse] Tap water for 60 s (room temperature)

[0029] Upon visual inspection after rinsing, the panel had no cracks (the plated film did not dissolve).Plating solution composition:

[0030] Zn ion concentration: 5 g / L (ZnO as Zn source) Ni ion concentration: 0.8 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 40 g / L (Comparative Example 1)

[0031] Using the following alkaline zinc-nickel alloy plating bath (5 L), zinc-nickel alloy plating of about 8 µm thickness was performed on a panel (pickled steel sheet (SPHC-P steel sheet): 70 mm long×50 mm wide×1 mm thick). The cathodic current density was 4 A / dm 2< , and the anode current density was 8 A / dm 2< ; the plating bath temperature was 25°C; the plating time was 30 minutes; a nickel plate was used as the anode. After plating, the panel was rinsed in the following wash waters: [1st Rinse] A 100 mL portion of the plating solution diluted with 2 L of water for 60 s (room temperature) [2nd Rinse] A 10 mL portion of the plating solution diluted with 2 L of water for 60 s (room temperature) [3rd Rinse] Tap water for 60 s (room temperature)

[0032] Upon visual inspection after rinsing, the panel had cracks (traces of plating film dissolution). It is considered that the plated film dissolved in the plating solution and in the first and second rinse waters.Plating solution composition:

[0033] Zn ion concentration: 5 g / L (ZnO as Zn source) Ni ion concentration: 0.8 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 40 g / L Brightener IZ-250YR2 (Dipsol Chemicals Co., Ltd.) 0.5 mL / L (a quaternary ammonium salt of nicotinic acid) (Example 2)

[0034] Using the following alkaline zinc-nickel alloy plating bath (30 L), barrel plating was performed by placing 1 kg of M8×35 bolts (iron) in an automated barrel plating machine (1 kg barrel). The cathodic current density was as shown in Table 2, and the anode current density was 8 A / dm 2< ; the plating bath temperature was 25°C; the plating time was 60 to 90 minutes (adjusted to achieve about 8 µm plating thickness). A nickel plate was used as the anode, and the rotation speed of the automated barrel plating machine was 4 to 6 rpm.

[0035] The bolts were taken out of the automated barrel plating machine, and the presence or absence of plating deposition was checked by visual inspection and X-ray fluorescence thickness measurement. The results are shown in Table 2.Plating solution composition:

[0036] Zn ion concentration: 5 g / L (ZnO as Zn source) Ni ion concentration: 0.8 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 40 g / L Brightener IZ-250YR1 (Dipsol Chemicals Co., Ltd.) 0.9 mL / L (Polyamine 0.15 g / L) (Comparative Example 2)

[0037] Using the following alkaline zinc-nickel alloy plating bath (30 L), barrel plating was performed by placing 1 kg of M8×35 bolts (iron) in an automated barrel plating machine (1 kg barrel). The cathodic current density was as shown in Table 2, and the anode current density was 8 A / dm 2< ; the plating bath temperature was 25°C; the plating time was 60 to 90 minutes (adjusted to achieve about 8 µm plating thickness). A nickel plate was used as the anode, and the rotation speed of the automated barrel plating machine was 4 to 6 rpm.

[0038] The bolts were taken out of the automated barrel plating machine, and the presence or absence of plating deposition was checked by visual inspection and X-ray fluorescence thickness measurement. The results are shown in Table 2.Plating solution composition:

[0039] Zn ion concentration: 8 g / L (ZnO as Zn source) Ni ion concentration: 1.6 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 130 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 60 g / L Brightener IZ-250YR1 (Dipsol Chemicals Co., Ltd.) 0.9 mL / L (Polyamine 0.15 g / L) Brightener IZ-250YR2 (Dipsol Chemicals Co., Ltd.) 0.5 mL / L (a quaternary ammonium salt of nicotinic acid) Table 2 Plating Solution TypeCathodic Current Density (A / dm 2< )0.30.40.50.751.0Example 2○○○○○Comparative Example 2×△○○○ ∘: Plating is deposited on all bolts (desired plating thickness). △ : Some bolts show plating deposition and some do not. Even among those with deposition, some are thinner than the desired thickness. ×: No plating deposition on all bolts (no plating). (Example 3 and Comparative Example 3)

[0040] Using the following alkaline zinc-nickel alloy plating bath (5 L), zinc-nickel alloy plating of about 8 µm thickness was performed on a Hull cell panel that had been subjected to electroless Ni plating (about 2 µm thick). The cathodic current density was 4 A / dm 2< , and the anode current density was 8 A / dm 2< ; the plating bath temperature was 25°C; the plating time was 45 minutes; a nickel plate was used as the anode. Before zinc-nickel alloy plating, the Hull cell panel with electroless Ni plating underwent pretreatment (rinsing → anodic electrolysis → rinsing → acid activation → rinsing). The obtained zinc-nickel alloy plated Hull cell panel was wrapped and baked in aluminum foil at 200°C for 30 minutes. The plating film peeled off due to baking was collected and analyzed for C content in the plating film by a high-frequency induction heating method (EMIA-Pro by Horiba, Ltd.). The results are shown in Table 3.

[0041] Plating solution composition: Zn ion concentration: 5 g / L (ZnO as Zn source) Ni ion concentration: 0.8 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 40 g / L Brightener IZ-250YR2 (Dipsol Chemicals Co., Ltd.) 0 or 0.2 mL / L (a quaternary ammonium salt of nicotinic acid) Table 3 Concentration of IZ-250YR2 (g / L)C content in Plating Film (%)00.1080.20.621 (Example 4)

[0042] Using the following alkaline zinc-nickel alloy plating bath (500 mL), a plating test similar to a Hull cell test was conducted using a long cell with a 20 cm iron plate as the cathode; the plating appearance, film thickness distribution, and Ni co-deposition ratio distribution were measured. These results are shown in Figures 1 and 2. A nickel plate was used as the anode, and the plating conditions similar to the Hull cell test were: 2 A - 20 min, 25°C; the plating bath was maintained at 25°C by cooling.Plating solution composition:

[0043] Zn ion concentration: 5 g / L (ZnO as Zn source) Ni ion concentration: 0.8 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 43 g / L (Example 5)

[0044] Using the following alkaline zinc-nickel alloy plating bath (500 mL), zinc-nickel alloy plating was performed by applying 24 Ah / L of electricity in a long cell with a 20 cm iron plate as the cathode. A nickel plate was used as the anode; the cathodic current density was 4 A / dm 2< , the anode current density was 8 A / dm 2< , the plating bath temperature was 25°C, and a nickel plate was used as the anode. The plating bath was cooled and maintained at 25°C. The Zn ion concentration in the plating bath was maintained constant by immersing and dissolving metallic zinc. The Ni ion concentration in the plating bath was maintained constant by adding a Ni replenisher IZ-250YNi (Dipsol Chemicals Co., Ltd.). The caustic soda concentration in the plating bath was periodically analyzed and replenished to maintain a constant level. The amine-based chelating agent IZ-250YB concentration in the plating bath was replenished and maintained constant. After 24 Ah / L of operation (running), the plating appearance was almost maintained (Figure 3).Plating solution composition:

[0045] Zn ion concentration: 5 g / L (ZnO as Zn source) Ni ion concentration: 0.8 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 40 g / L Ca ion concentration: 25 mg / L (from tap water) Mg ion concentration: 10 mg / L (from tap water) (Example 6)

[0046] Using the following alkaline zinc-nickel alloy plating bath (500 mL), a plating test similar to a Hull cell test was conducted using a long cell with a 20 cm iron plate as the cathode; the plating appearance, film thickness distribution, and Ni co-deposition ratio distribution were measured. These results are shown in Figures 1 and 2. A nickel plate was used as the anode, and the plating conditions similar to the Hull cell test were: 2 A - 20 min, 25°C; the plating bath was maintained at 25°C by cooling.Plating solution composition:

[0047] Zn ion concentration: 8 g / L (ZnO as Zn source) Ni ion concentration: 1.3 g / L (NiSO 4 ·6H 2 O as Ni source) Caustic soda concentration: 65 g / L Amine-based chelating agent (alkylene amine ethylene oxide adduct) IZ-250YB (Dipsol Chemicals Co., Ltd.) 43 g / L (Reference Example 1)

[0048] Except that tap water was replaced by ion-exchanged water (with 0 mg / L Ca ions and 0 mg / L Mg ions), the procedure was the same as in Example 5. After 24 Ah / L of operation (running), the plating appearance could not be maintained (Figure 3).

Claims

1. An alkaline zinc-nickel alloy plating solution comprising zinc ions, nickel ions, sodium ions, hydroxide ions, and an amine-based chelating agent, the alkaline zinc-nickel alloy plating solution being free of nitrogen-containing heterocyclic compounds.

2. The zinc-nickel alloy plating solution according to claim 1, wherein a content of zinc ions is 2 g / L or more and 7 g / L or less.

3. The zinc-nickel alloy plating solution according to claim 1 or 2, wherein a content of nickel ions is 0.4 g / L or more and less than 1.5 g / L.

4. The zinc-nickel alloy plating solution according to any one of claims 1 to 3, wherein a content of the amine-based chelating agent is 5 g / L or more and 100 g / L or less.

5. The zinc-nickel alloy plating solution according to any one of claims 1 to 4, wherein the solution contains sodium hydroxide at 50 g / L or more and 85 g / L or less.

6. The zinc-nickel alloy plating solution according to any one of claims 1 to 5, further comprising 8 mg / L or more and 100 mg / L or less of calcium ions and / or 2 mg / L or more and 40 mg / L or less of magnesium ions.

7. The zinc-nickel alloy plating solution according to any one of claims 1 to 6, further comprising a water-soluble cationic polymer.

8. The zinc-nickel alloy plating solution according to claim 7, wherein a content of the water-soluble cationic polymer is greater than 0.1 g / L and 10 g / L or less.

9. A zinc-nickel alloy barrel plating method comprising plating a workpiece to be plated using the zinc-nickel alloy plating solution according to any one of claims 1 to 8.

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