Nickel electroplating bath for depositing decorative nickel coatings on substrates

Abstract

To provide a nickel electroplating bath that does not contain boric acid.SOLUTION: The present invention relates to a nickel electroplating bath for depositing a decorative nickel coating on a substrate to be treated, characterized in that: the electroplating bath comprises at least one nickel ion source, at least one amino acid and / or at least one carboxylic acid, which is not an amino acid; the total concentration of the amino acid is ranging from 1 to 10 g / l, and the total concentration of carboxylic acid, which is / are not an amino acid, is ranging from 10 to 40 g / l; the electroplating bath is free of boric acid; the total concentration of the nickel ions is ranging from 55 to 80 g / l; and the nickel electroplating bath has a chloride content ranging from 7.5 to 40 g / l. The present invention also relates to: a method for depositing a nickel coating on a substrate to be treated; and the use of such an inventive nickel electroplating bath for depositing a bright, semi-bright, satin, matte or non-conductive particle containing nickel coating by conducting such a method.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to nickel electroplating baths for depositing decorative nickel coatings on treated substrates. The present invention also relates to methods for depositing decorative nickel coatings on treated substrates. Furthermore, the present invention relates to the use of such nickel electroplating baths of the present invention to deposit bright, semi-bright, satin, matte, or non-conductive particle-containing nickel coatings by carrying out such methods. [Background technology]

[0002] In nickel electroplating baths, it is generally very important to maintain the pH value within a defined range.

[0003] Therefore, in the past, buffer systems have been applied to nickel baths to achieve this goal.

[0004] The most common systems are based on the so-called "Watts electrolyzer" and have the following general composition: 240-550 g / l nickel sulfate (NiSO4·7H2O or NiSO4·6H2O), 30-150 g / l nickel chloride (NiCl2·6H2O), and 30-55g / l of boric acid (H3BO3).

[0005] The large amount of nickel sulfate provides the necessary nickel ion concentration, while nickel chloride improves anodic corrosion and increases electrical conductivity. Boric acid is used as a weak buffer to maintain pH.

[0006] Furthermore, organic and inorganic agents (brighteners) are often added to the electrolyte to achieve a bright and lustrous appearance for the nickel plated coating. The type of brighteners added and their concentrations determine the appearance of the nickel coating, i.e., bright, glossy, semi-bright, satin, matte, etc.

[0007] However, boric acid is classified as toxic and is likely to be banned from the global market, so there is a strong desire in the industry to replace boric acid with other non-toxic substances. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, in view of the prior art, it was an object of the present invention to provide a boric acid-free nickel electroplating bath.

[0009] More particularly, it was an object of the present invention to provide a nickel electroplating bath that is suitable as a basis for depositing a wide variety of different nickel coatings with respect to optical appearance and chemical properties, such as bright nickel coatings, semi-bright nickel coatings, satin-like nickel coatings, matte nickel coatings, or nickel coatings containing non-conductive particles.

[0010] It was a further object of the present invention to provide a method for depositing a variety of different nickel coatings with respect to optical appearance and chemical properties, such as bright nickel coatings, semi-bright nickel coatings, satin nickel coatings, matte nickel coatings, or nickel coatings containing non-conductive particles. [Means for solving the problem]

[0011] These objects, and also further objects not explicitly stated but which can be readily derived or identified from the context discussed herein in the introduction, are achieved by a nickel electroplating bath having all the features of claim 1. Appropriate modifications to the bath of the invention are protected in dependent claims 2 to 8. Furthermore, claim 9 relates to a method for depositing a decorative nickel coating on a treated substrate, while claims 10 to 14 focus on appropriate modifications of this method. Claim 15 relates to the use of such a nickel electroplating bath for depositing a bright, semi-bright, satiny, matte, or non-conductive particle-containing nickel coating by carrying out such a method.

[0012] Accordingly, the present invention provides a nickel electroplating bath for depositing a decorative nickel coating on a treated substrate, characterized in that the electroplating bath comprises at least one source of nickel ions, at least one amino acid, and / or at least one carboxylic acid that is not an amino acid, wherein the total concentration of the amino acids is in the range of 1 to 10 g / l and the total concentration of the carboxylic acids that are not amino acids is in the range of 10 to 40 g / l, the electroplating bath is free of boric acid, the total concentration of nickel ions is in the range of 55 to 80 g / l, and the nickel electroplating bath has a chloride content in the range of 7.5 to 40 g / l.

[0013] Herein, at least one amino acid and / or at least one carboxylic acid represent complexing agents for complexing nickel ions in the respective nickel electroplating baths. Herein, the "classical" complexing agent of the prior art, i.e., boric acid, must be and is avoided. Thus, the nickel electroplating baths of the present invention are boric acid-free.

[0014] It is therefore possible, in an unexpected manner, to provide a boric acid-free nickel electroplating bath that has a low environmental impact.

[0015] Furthermore, they have succeeded in providing a nickel electroplating bath that is suitable as a basis for depositing various types of different nickel coatings in terms of optical appearance and chemical properties, such as bright nickel coatings, semi-bright nickel coatings, satin nickel coatings, matte nickel coatings, or non-conductive particle-containing nickel coatings, etc. The nickel electroplating bath also exhibits good leveling performance, resulting in well-leveled coatings.

[0016] The objects, features, and advantages of the present invention will also become apparent from the following description taken in conjunction with the tables.

[0017] Table 1 shows inventive experiments on bright nickel coatings according to embodiments of the present invention.

[0018] Table 2 shows comparative experiments of bright nickel coatings according to comparative embodiments outside the scope of the present invention.

[0019] Table 3 shows inventive experiments on bright nickel coatings according to further embodiments of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] In a preferred embodiment of the present invention, the nickel electroplating bath has a chloride content in the range of 10 to 30 g / l.

[0021] The expression "chloride content" in the context of the present invention means the source of chloride ions.

[0022] Nickel chloride may be partially replaced with sodium chloride.

[0023] Additionally, chloride in the electrolyte may be partially replaced with an equal amount of bromide.

[0024] The source of nickel ions in the context of the present invention may be any type of nickel salt or nickel complex, such as nickel chloride and / or nickel sulfate, that is suitable for providing free nickel ions in the respective nickel electrodeposition bath.

[0025] The nickel electroplating bath of the present invention can be used to deposit decorative nickel coatings on several different types of substrates based on metals and / or metal alloys, in particular steel, copper, brass, aluminum, bronze, magnesium and / or zinc die-cast products; or on "POP" substrates. "POP" means "plating on plastics" in the sense of the present invention. POP substrates therefore preferably include synthetic substrates based on at least one polymer compound, more preferably based on acrylonitrile butadiene styrene (ABS), polyamide, polypropylene or ABS / PC (polycarbonate).

[0026] In preferred embodiments of the present invention, the nickel electroplating baths are substantially free, and preferably completely free, of other metal ions that may be electrolytically deposited along with the nickel ion source as a nickel alloy layer (in addition to the nickel ion source always provided in the electroplating baths of the present invention).

[0027] In particular, the nickel electroplating bath is preferably substantially free, and preferably completely free, of sources of iron, gold, copper, bismuth, tin, zinc, silver, lead, and aluminum ions.

[0028] The expression "substantially free" in the context of the present invention means a concentration of less than 1 g / l, preferably less than 0.1 g / l, more preferably less than 0.01 g / l of the respective metal ion source.

[0029] In one embodiment, the at least one amino acid is selected from the group consisting of beta-alanine, glycine, glutamic acid, DL-aspartic acid, threonine, valine, glutamine, or L-serine.

[0030] In one embodiment, the at least one carboxylic acid that is not an amino acid is selected from the group consisting of a monocarboxylic acid, a dicarboxylic acid, or a tricarboxylic acid.

[0031] In a preferred embodiment thereof, the at least one carboxylic acid that is not an amino acid is selected from the group consisting of tartaric acid, glycolic acid, malic acid, acetic acid, lactic acid, citric acid, succinic acid, propanoic acid, formic acid or glutaric acid.

[0032] In one embodiment, the electroplating bath comprises at least two different carboxylic acids, neither of which is an amino acid, and the total concentration of the two different carboxylic acids is in the range of 10 to 40 g / l.

[0033] In one embodiment, the electroplating bath comprises at least one amino acid and one carboxylic acid that is not an amino acid, wherein the total concentration of the amino acids is in the range of 1 to 10 g / L, and the total concentration of the carboxylic acids that are not amino acids is in the range of 10 to 40 g / L.

[0034] In a preferred embodiment, the total concentration of nickel ions is in the range of 60 to 75 g / l, preferably 62 to 72 g / l.

[0035] In one embodiment, the pH value of the electroplating bath ranges from 2 to 6, preferably from 3 to 5, and more preferably from 3.5 to 4.7.

[0036] Furthermore, in certain embodiments of the present invention, the nickel electroplating bath may contain at least one wetting agent, such as 2-ethylhexyl sulfate, di-alkylsulfusuccinate, polymeric naphthalene sulfonate, lauryl sulfate, or lauryl ether sulfate, and the concentration of such wetting agent used is in the range of 5 to 500 mg / L, preferably in the range of 10 to 350 mg / L, and more preferably in the range of 20 to 250 mg / L.

[0037] The electroplating bath may further comprise benzoic acid or an alkali metal benzoate at a concentration ranging from 0.005 to 5 g / L, preferably from 0.02 to 2 g / L, and more preferably from 0.05 to 0.5 g / L. Such additive compounds help to reduce internal stress in the deposited coating.

[0038] The electroplating bath may also further comprise salicylic acid in a concentration ranging from 0.1 to 10 g / L, preferably from 0.3 to 6 g / L, more preferably from 0.5 to 3.5 g / L. Such additives have a positive effect on the hardness, durability and optical properties of the coatings achieved.

[0039] The electroplating bath may further comprise additional compounds selected from brighteners, leveling agents, internal stress reducers, and wetting agents, especially in concentrations ranging from 0.005 to 5 g / l, preferably from 0.02 to 2 g / l, more preferably from 0.05 to 0.5 g / l.

[0040] Illustratively, the primary brightener may, in certain embodiments, preferably for bright nickel coatings, include unsaturated, most often aromatic sulfonic acids, sulfonamides, sulfimides, N-sulfonylcarboxamides, sulfinates, diarylsulfones, or salts thereof, particularly sodium or potassium salts.

[0041] The best known compounds are, for example, m-benzenedisulfonic acid, benzoic acid sulfimide (saccharin), 1,3,6-naphthalenetrisulfonic acid trisodium, benzenemonosulfonate sodium, dibenzenesulfonamide, benzenemonosulfinic acid sodium, vinylsulfonic acid, allylsulfonic acid, the sodium salt of allylsulfonic acid, p-toluenesulfonic acid, p-toluenesulfonamide, sodium propargylsulfonate, benzoic acid sulfimide, 1,3,6-naphthalenetrisulfonic acid and benzoylbenzenesulfonamide.

[0042] Additionally, such primary brighteners may include propargyl alcohol and / or its derivatives (ethoxylated or propoxylated).

[0043] The primary brightener may be added to the electrolyte bath in a concentration ranging from 0.001 to 8 g / l, preferably from 0.01 to 2 g / l, more preferably from 0.02 to 1 g / l. Several primary brighteners may be used simultaneously.

[0044] Furthermore, the object of the present invention is also to provide a method comprising the steps of: i) contacting the treated substrate with such a nickel electroplating bath of the present invention; ii) contacting at least one anode with a nickel electroplating bath; iii) applying a voltage to the treated substrate and at least one anode; iv) electrodepositing a decorative nickel coating onto the treated substrate; The problem is also solved by a method of depositing a decorative nickel coating on a treated substrate, comprising:

[0045] In one embodiment, the deposition process is carried out at an operating temperature range of 30°C to 70°C, preferably 40°C to 65°C, more preferably 50°C to 60°C.

[0046] In one embodiment, the deposition method is 1 to 7 amps / dm 2 (ASD), preferably 1.5 to 6 ASD, more preferably 2 to 5 ASD.

[0047] In one embodiment, the depositing method is carried out with a working time of voltage application and subsequent electrodeposition of the decorative nickel coating (method steps iii) and iv)) in the range of 5 to 50 minutes, preferably 6 to 35 minutes, more preferably 8 to 25 minutes.

[0048] In one embodiment, the electroplating bath further comprises at least one saccharin and / or saccharin salt, preferably a saccharin derivative in the form of the sodium salt of saccharin, in a concentration ranging from 1 to 10 g / L, preferably from 1.5 to 7 g / L, and more preferably from 2 to 6 g / L; and at least one sulfonic acid and / or a sulfonic acid derivative in the form of a sulfonate salt, preferably selected from the group consisting of allyl sulfonic acid, vinyl sulfonic acid, the sodium salt of allyl sulfonic acid, the sodium salt of vinyl sulfonic acid, or mixtures thereof, in a total concentration ranging from 0.1 to 5 g / L, preferably from 0.25 to 3.5 g / L, and more preferably from 0.5 to 2.0 g / L. This results in the deposition of a bright nickel coating. The selective selection of the above-mentioned additives demonstrates the unique utility of the nickel electroplating bath of the present invention for depositing decorative nickel coatings with different optical appearances and chemical properties.

[0049] In an alternative embodiment to the foregoing embodiment, the electroplating bath further comprises at least one diol, preferably selected from the group consisting of 2,5-hexynediol and 1,4-butynediol, in a concentration ranging from 10 to 300 mg / L, preferably from 50 to 250 mg / L, and more preferably from 100 to 220 mg / L; or at least one additive selected from the group of pyridinium propyl sulfobetaine (PPS) or a derivative thereof (e.g., PPS-OH), in a total concentration ranging from 5 to 350 mg / L, preferably from 10 to 200 mg / L, and even more preferably from 50 to 150 mg / L.

[0050] This results in the deposition of a semi-bright nickel coating. The selective selection of additives described above, as well as the alternative embodiments previously described, also demonstrate the unique utility of the nickel electroplating baths of the present invention for depositing decorative nickel coatings of different optical appearances and chemistries.

[0051] Furthermore, the objects of the present invention are also solved by the use of such nickel electroplating baths for depositing bright, semi-bright, satin-like, matte, or non-conductive particle-containing nickel coatings by carrying out such methods.

[0052] Thus, the present invention addresses the problem of providing a borate-free nickel electroplating bath for depositing decorative nickel coatings of different optical appearances and chemistries, such as bright nickel coatings, semi-bright nickel coatings, satin nickel coatings, matte nickel coatings, or non-conductive particle-containing nickel coatings.

[0053] The following non-limiting examples are provided to illustrate one embodiment of the present invention and to facilitate understanding of the invention, but are not intended to limit the scope of the invention as defined by the appended claims.

[0054] [overview] The substrate is always pretreated before use for nickel deposition in the following way: i) Degreasing with hot soak cleaner ii) Electrolytic degreasing iii) Rinse iv) Acid immersion with 10% by volume sulfuric acid

[0055] The sample substrates are scratched for a subjective optical judgment of the leveling. The appearance of the nickel coating obtained on the substrate is also judged optically. The size of the sample substrates is always 7cm x 10cm (width x length) with 70cm on each side. 2 resulting in a treated surface of (Tables 1, 2 and 3).

[0056] All concentrations shown in Tables 1, 2 and 3 for the acid form of the complexing agent are listed in g / l unless otherwise specified.

[0057] The experiments shown in Tables 1, 2 and 3 are numbered sequentially.

[0058] Turning now to the tables, Table 1 shows experimental performance of bright nickel coatings according to embodiments of the present invention.

[0059] Nickel deposition was carried out in a Hull Cell at 2.5 amps (A) for 10 minutes at a temperature of 55°C + / - 3°C for all experiments listed in Table 1. Additionally, pressurized air was introduced at 3 liters / minute during nickel deposition.

[0060] The nickel concentration was 67 g / l for all experiments listed in Table 1.

[0061] It is clear that uniform, bright, and leveled nickel coatings were obtained in all of the inventive experiments listed in Table 1. Even when many different acids were investigated as complexing agents for nickel ions, these boric acid-free baths always produced good, significant results. All acids were used in the specific respective concentration ranges set forth in claim 1, depending on the chemical nature of the acid, be it an amino acid or a non-amino acid carboxylic acid.

[0062] Each column indicates the experiment number, the acid used as the complexing agent, the concentration of the acid used as the complexing agent, the pH value of the nickel bath, and the achieved results of nickel coating in the range of highest to lowest current density on the Hull cell panel (for a total length of 10 cm) (the columns are listed from left to right in Table 1).

[0063] [Table 1]

[0064] Table 2 shows comparative experiments on bright nickel coatings according to comparative embodiments outside the scope of the present invention.

[0065] For all experiments listed in Table 2, nickel deposition was carried out in a Hull Cell at a temperature of 55°C + / - 3°C, similar to the experiments listed in Table 1. Additionally, 3 liters / minute of pressurized air was introduced during nickel deposition. Each column indicates the experiment number, the acid used as the complexing agent, the concentration of the acid used as the complexing agent, the pH value of the nickel bath, the applied current (amperes, A), the nickel ion concentration (g / l), the application time of the current (minutes), and the achieved result of the nickel coating (columns are listed from left to right in Table 2).

[0066] [Table 2]

[0067] Runs 30-35 represent comparative runs using the same respective acids as the complexing agents but at different concentrations as the specific runs in Table 1. Runs 30-35 all have concentrations of complexing agent relative to nickel ions that are either too low or too high compared to the claimed concentration ranges.

[0068] Runs 36-38 represent comparative runs in which the acid was used in the claimed concentration range, but the operating parameters were varied: current (Run 36), application time (Run 37), and nickel ion concentration (Run 38). Each value is highlighted and underlined in Table 2 for illustrative purposes.

[0069] It is clear that all comparative experiments listed in Table 2 produced worse results than the experiments in Table 1. Clearly, the selection of different parameters appropriate for depositing a uniform, bright nickel coating is unpredictable. Therefore, the claimed bath and method are inventive as a selection invention based on an inventive selection of the necessary parameters, where changing only one parameter clearly results in an inferior nickel coating rather than a bright, uniform nickel coating.

[0070] Comparative experiments 30-38 also contained no boric acid.

[0071] Experiments 39-41 show comparative experiments based on boric acid, which has been commonly used up to now as a complexing agent for nickel ions, and therefore represents the general prior art.

[0072] Table 3 shows the inventive experiments on bright nickel coatings according to further embodiments of the invention.

[0073] The experiments listed in Table 3 were performed in the same manner as the experiments listed in Table 1. Here, Experiments 42-46 represent the combination of two carboxylic acids, neither of which is an amino acid (Experiments 42 and 43), and one amino acid and one carboxylic acid that is not an amino acid (Experiments 44-46). All of the results for these inventive examples in Table 3 have the same positive results as Table 1. All result in a uniform, bright nickel coating. The column (Concentration) includes the concentrations of both acids.

[0074] [Table 3]

[0075] While the principles of the invention have been described with respect to certain specific embodiments, provided for purposes of illustration, it should be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. It is therefore to be understood that the invention disclosed herein is intended to cover all such modifications as fall within the scope of the appended claims. The scope of the invention is limited only by the scope of the appended claims.

Claims

1. A nickel electroplating bath for depositing a decorative nickel coating on a treated substrate, the electroplating bath comprising at least one source of nickel ions, at least one amino acid, and / or at least one carboxylic acid that is not an amino acid, wherein the total concentration of the amino acids is in the range of 1 to 10 g / l and the total concentration of the carboxylic acids that are not amino acids is in the range of 10 to 40 g / l, the electroplating bath is free of boric acid, the total concentration of the nickel ions is in the range of 55 to 80 g / l, and the nickel electroplating bath has a chloride content in the range of 7.5 to 40 g / l; the at least one carboxylic acid that is not an amino acid is selected from the group consisting of tartaric acid, glycolic acid, lactic acid, succinic acid, and glutaric acid; A nickel electroplating bath, wherein the pH value of the electroplating bath is in the range of 3.5 to 4.

7.

2. 2. The nickel electroplating bath of claim 1, wherein the at least one amino acid is selected from the group consisting of β-alanine, glycine, glutamic acid, DL-aspartic acid, threonine, valine, glutamine, or L-serine.

3. A nickel electroplating bath for depositing a decorative nickel coating on a treated substrate, characterized in that the electroplating bath contains at least one source of nickel ions, at least one amino acid, and / or at least one carboxylic acid that is not an amino acid, wherein the total concentration of the amino acids is in the range of 1 to 10 g / l and the total concentration of the carboxylic acids that are not amino acids is in the range of 10 to 40 g / l, the electroplating bath does not contain boric acid, the total concentration of the nickel ions is in the range of 55 to 80 g / l, and the nickel electroplating bath has a chloride content in the range of 7.5 to 40 g / l; the at least one carboxylic acid that is not an amino acid is selected from the group consisting of succinic acid and glutaric acid; A nickel electroplating bath, wherein the pH value of the electroplating bath is in the range of 3.5 to 4.

7.

4. A nickel electroplating bath for depositing a decorative nickel coating on a treated substrate, characterized in that the electroplating bath contains at least one source of nickel ions, at least one amino acid, and / or at least two different carboxylic acids which are not both amino acids, wherein the total concentration of the amino acids is in the range of 1 to 10 g / l and the total concentration of the at least two different carboxylic acids which are not both amino acids is in the range of 10 to 40 g / l, the electroplating bath does not contain boric acid, the total concentration of the nickel ions is in the range of 55 to 80 g / l, and the nickel electroplating bath has a chloride content in the range of 7.5 to 40 g / l; one of the at least two different carboxylic acids that are not both amino acids is selected from the group consisting of tartaric acid, glycolic acid, lactic acid, succinic acid, and glutaric acid; A nickel electroplating bath, wherein the pH value of the electroplating bath is in the range of 3.5 to 4.

7.

5. 4. The nickel electroplating bath according to claim 1, wherein the electroplating bath comprises at least one amino acid and one carboxylic acid that is not an amino acid, the total concentration of the amino acids being in the range of 1 to 10 g / l, and the total concentration of the carboxylic acids that are not amino acids being in the range of 10 to 40 g / l.

6. 6. The nickel electroplating bath according to claim 1, wherein the total concentration of nickel ions is in the range of 60 to 75 g / l.

7. The method steps are as follows: i) contacting the treated substrate with the nickel electroplating bath according to any one of claims 1 to 6; ii) contacting at least one anode with said nickel electroplating bath; iii) applying a voltage to the treated substrate and the at least one anode; iv) electrodepositing a decorative nickel coating onto the treated substrate; 1. A method for depositing a decorative nickel coating on a treated substrate, comprising:

8. 8. A method for depositing a decorative nickel coating according to claim 7, characterized in that the deposition method is carried out at an operating temperature range of 30°C to 70°C.

9. The deposition method is 1 to 7 amperes / dm ２ 9. A method for depositing a decorative nickel coating according to claim 7 or 8, characterized in that it is carried out in an operating current density range of (ASD).

10. 10. Method for depositing a decorative nickel coating according to any one of claims 7 to 9, characterized in that the depositing method is carried out with an operating time of voltage application and subsequent electrodeposition of the decorative nickel coating (method steps iii) and iv)) ranging from 5 to 50 minutes.

11. 11. The method for depositing a decorative nickel coating according to any one of claims 7 to 10, characterized in that the electroplating bath further comprises at least one saccharin and / or saccharin derivative in the form of a saccharin salt, in a concentration ranging from 1 to 10 g / l; and at least one sulfonic acid and / or derivative of sulfonic acid in the form of a sulfonate, in a total concentration ranging from 0.1 to 5 g / l.

12. 11. The method for depositing a decorative nickel coating according to any one of claims 7 to 10, characterized in that the electroplating bath further comprises at least one additive selected from the group of: at least one diol, in a concentration ranging from 10 to 300 mg / l; or at least one additive selected from the group of pyridinium propyl sulfobetaine (PPS) or its derivatives, such as PPS-OH, in a total concentration ranging from 5 to 350 mg / l.

13. 13. Use of the nickel electroplating bath according to any one of claims 1 to 6 for depositing a bright, semi-bright, matte or non-conductive particle-containing nickel coating by carrying out the method according to any one of claims 7 to 12.

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