Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
  • C25D3/14—Electroplating: Baths therefor from solutions of nickel or cobalt from baths containing acetylenic or heterocyclic compounds
  • C25D3/16—Acetylenic compounds

Definitions

• the present invention relates to a nickel electroplating bath for depositing a decorative nickel coating on a substrate to be treated.
• the present invention is also directed to a method for depositing a decorative nickel coating on a substrate to be treated.
• the invention is related to 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.
• the most conventional system is based on the so-called "Watts electrolytic bath", which has the following general composition: 240- 550 g/l nickel sulfate (NiSO 4 ⁇ 7 H 2 O or NiSO 4 ⁇ 6 H 2 O), 30-150 g/l nickel chloride (NiCl 2 ⁇ 6 H 2 O), and 30-55 g/l boric acid (H 3 BO 3 ).
• nickel sulfate provides the necessary concentration of nickel ions, while nickel chloride improves anode corrosion and increases conductivity.
• Boric acid is used as a weak buffer to maintain the pH value.
• organic and inorganic agents are often added to the electrolyte.
• the types of added brighteners and their concentrations determine the appearance of the nickel coating, i.e., brilliant, bright, semi-bright, satin, matte etc.
• boric acid has been classified as toxic in the meantime and is considered to be banned for the world market. So, the industry has a strong demand to replace boric acid by other non-toxic substances.
• nickel electroplating bath which shall be suitable as a basis for depositing various kinds of different nickel coatings regarding their optical appearance and their chemical properties, such as bright nickel coating, semi-bright nickel coating, satin nickel coating, matte nickel coating or non-conductive particle containing nickel coating.
• a nickel electroplating bath having all features of claim 1. Appropriate modifications to the inventive bath are protected in dependent claims 2 to 8. Further, claim 9 relates to a method for depositing a decorative nickel coating on a substrate to be treated, while claims 10 to 14 focus on appropriate modifications of this method. Claim 15 relates to a use of such a nickel electroplating bath for depositing a bright, semi-bright, satin, matte or non-conductive particle containing nickel coating by conducting such a method.
• the present invention accordingly provides 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 a nickel ion source, at least one amino acid and/or at least one carboxylic acid, which is not an amino acid; wherein the total concentration of the amino acid(s) is ranging from 1 to 10 g/l, wherein the total concentration of carboxylic acid(s), which is/are not an amino acid, is ranging from 10 to 40 g/l; wherein the electroplating bath is free of boric acid; wherein the total concentration of the nickel ions is ranging from 55 to 80 g/l; and wherein the nickel electroplating bath has a chloride content ranging from 7.5 to 40 g/l.
• the at least one amino acid and/or the at least one carboxylic acid are representing complexing agents for complexing the nickel ions in the respective nickel electroplating bath.
• the "classical” complexing agent of the prior art namely boric acid
• the nickel electroplating bath of the present invention is boric acid free.
• nickel electroplating bath which is suitable as a basis for depositing various kinds of different nickel coatings regarding their optical appearance and their chemical properties, such as bright nickel coating, semi-bright nickel coating, satin nickel coating, matte nickel coating or non-conductive particle containing nickel coating.
• the nickel electroplating bath also shows good levelling performance and leads to well-levelled coatings.
• the nickel electroplating bath has a chloride content ranging from 10 to 30 g/l.
• chloride content means in the context of the present invention a chloride ion source.
• Nickel chloride may be replaced partly by sodium chloride.
• chloride in the electrolyte may be replaced partly by equivalent amounts of bromide.
• a nickel ion source in the context of the present invention can be any kind of nickel salt or nickel complex, which is suitable to provide a free nickel ion in the respective nickel electrodeposition bath, such as nickel chloride and/or nickel sulfate.
• the nickel electroplating bath of the present invention can be used for depositing decorative nickel coatings on a plurality of different kind of substrates to be treated based on a metal and/or metal alloy, in particular steel, copper, brass, aluminum, bronze, magnesium and/or zinc diecasting; or on "POP" substrates.
• POP means in the sense of the invention "plating on plastics”.
• POP substrates comprise a synthetic substrate, preferably based on at least one polymeric compound, more preferably based on acrylonitrile-butadiene- styrene (ABS), polyamide, polypropylene or ABS/PC (polycarbonate).
• the nickel electroplating bath is substantially free, preferably completely free, of any other metal ion (additionally to the nickel ion source, which is always provided in the inventive electroplating bath), which can be electrolytically deposited together with the nickel ion source as nickel alloy layer.
• the nickel electroplating bath is substantially free, preferably completely free, of an iron, gold, copper, bismuth, tin, zinc, silver, lead, and aluminum ion source.
• substantially free means in the context of the present invention a concentration of less than 1 g/l, preferably less than 0.1 g/l, and more preferably less than 0.01 g/l of the respective metal ion source.
• the at least one amino acid is selected from the group consisting of ⁇ alanine, glycine, glutamic acid, DL- aspartic acid, threonine, valine, glutamine or L-serine.
• the at least one carboxylic acid which is not an amino acid, is selected from the group consisting of mono carboxylic acids, di carboxylic acids or tri carboxylic acids.
• the at least one carboxylic acid which 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.
• the electroplating bath comprises at least two different carboxylic acids, which are both not amino acids; wherein the total concentration of said two different carboxylic acids, is ranging from 10 to 40 g/l.
• the electroplating bath comprises at least one amino acid and one carboxylic acid, which is not an amino acid; wherein the total concentration of said amino acid is ranging from 1 to 10 g/l, wherein the total concentration of said carboxylic acid, which is not an amino acid, is ranging from 10 to 40 g/l.
• the total concentration of the nickel ions is ranging from 60 to 75 g/l, and preferably from 62 to 72 g/l.
• the pH-Value of the electroplating bath ranges from 2 to 6, preferably from 3 to 5, more preferably from 3.5 to 4.7.
• the nickel electroplating bath may comprise in certain embodiments of the present invention at least a wetting agent, such as 2-ethylhex-ylsulfate, di-alkylsulfusuccinate, polymerized naphtalenesulfonate, lauryl sulfate or lauryl ether sulfate, wherein the concentration of such a wetting agent, is used, is ranging from 5 to 500 mg/l, preferably ranging from 10 to 350 mg/l, and more preferably ranging from 20 to 250 mg/l.
• a wetting agent such as 2-ethylhex-ylsulfate, di-alkylsulfusuccinate, polymerized naphtalenesulfonate, lauryl sulfate or lauryl ether sulfate, wherein the concentration of such a wetting agent, is used, is ranging from 5 to 500 mg/l, preferably ranging from 10 to 350 mg/l, and more preferably ranging from 20 to 250 mg
• 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, more preferably from 0.05 to 0.5 g/l.
• 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, more preferably from 0.05 to 0.5 g/l.
• 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, more preferably from 0.05 to 0.5 g/l.
• the electroplating bath may also further comprise salicylic acid at 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.
• salicylic acid at 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.
• the electroplating bath may further comprises additional compounds selected from brighteners, leveling agents, internal stress reducers, and wetting agents, in particular at a concentration 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.
• a primary brightener can be comprised in certain embodiments, preferably for bright nickel coatings, unsaturated, in most cases aromatic sulfonic acids, sulfonamides, sulfimides, N-sulfonylcarboxamides, sulfinates, di-arylsulfones or the salts thereof, in particular the sodium or potassium salts.
• the most familiar compounds are for example m-benzenedisulfonic acid, benzoic acid sulfimide (saccharine), trisodium 1,3,6- naphthalene trisulfonate, sodium benzene monosulfonate, dibenzene sulfonamide, sodium benzene mono-sulfinate, vinyl sulfonic acid, allyl sulfonic acid, sodium salt of allyl sulfonic acid, p-toluene sulfonic acid, p-toluene sulfonamide, sodium propargyl sulfonate, benzoic acid sulfimide, 1,3,6-naphthalenetrisulfonic acid and benzoyl benzene sulfonamide.
• benzoic acid sulfimide 1,3,6-naphthalenetrisulfonic acid and benzoyl benzene sulfonamide.
• Such a primary brightener can comprise propargyl alcohol and/or derivatives (ethoxylated or propoxylated) thereof.
• the primary brighteners can be added to the electrolyte bath at 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. It is also possible to use several primary brighteners simultaneously.
• the object of the present invention is also solved by a method for depositing a decorative nickel coating on a substrate to be treated comprising the following method steps:
• the method for depositing is executed in a working temperature range from 30°C to 70°C, preferably from 40°C to 65°C, and more preferably from 50°C to 60°C.
• the method for depositing is executed in a working current density range from 1 to 7 Ampere/dm 2 (ASD), preferably from 1.5 to 6 ASD, and more preferably from 2 to 5 ASD.
• ASD Ampere/dm 2
• the method for depositing is executed in a working time for applying the voltage and the subsequent electrodeposition of the decorative nickel coating (method steps iii) and iv)) ranging from 5 to 50 minutes, preferably from 6 to 35 minutes, and more preferably from 8 to 25 minutes.
• the electroplating bath further comprises at least a saccharin and/or a saccharin derivative in form of a saccharin salt, preferably the sodium salt of saccharin, at a concentration ranging from 1 to 10 g/l, preferably from 1.5 to 7 g/l, more preferably from 2 to 6 g/l; and at least a sulfonic acid and/or a derivative of a sulfonic acid in form of a sulfonic acid salt, preferably selected from the group consisting of allyl sulfonic acid, vinyl sulfonic acid, sodium salt of allyl sulfonic acid, sodium salt of vinyl sulfonic acid, or mixtures thereof, at a total concentration ranging from 0.1 to 5 g/l, preferably from 0.25 to 3.5 g/l, more preferably from 0.5 to 2.0 g/l.
• the electroplating bath further comprises at least a diol, preferably selected from the group consisting of 2,5 hexinediol and 1,4 butinediol, at a concentration ranging from 10 to 300 mg/l, preferably from 50 to 250 mg/l, more preferably from 100 to 220 mg/l; or at least an additive selected from the group of pyridiniumpropylsulfobetaine (PPS) or derivatives thereof (such as PPS-OH), at a total concentration ranging from 5 to 350 mg/l, preferably from 10 to 200 mg/l, more preferably from 50 to 150 mg/l.
• PPS pyridiniumpropylsulfobetaine
• the object of the present invention is also solved by making use of such a nickel electroplating bath for depositing a bright, semi-bright, satin, matte or non-conductive particle containing nickel coating by conducting such a method.
• the present invention thus addresses the problem of providing a boric acid free nickel electroplating bath for depositing decorative nickel coatings of different optical appearance and chemical properties, such as bright nickel coating, semi-bright nickel coating, satin nickel coating, matte nickel coating or non-conductive particle containing nickel coating.
• the substrates have been always pretreated in the following manner before their use for the nickel deposition:
• Sample substrates have been scratched for subjective optical judgment of leveling. The glance of the resulting nickel coatings on the substrates has been also judged optically.
• the size of the sample substrates have been always 7 cm x 10 cm (width x length) leading to a surface to be treated of 70 cm 2 on one side (Tables 1,2, and 3).
• Table 1 shows conducted experiments for bright nickel coatings in accordance with embodiments of the present invention.
• the nickel deposition took place for all experiments listed in Table 1 in a Hull cell wherein 2.5 Ampere (A) was applied for 10 minutes at a temperature of 55°C +/- 3 °C. Further, 3 liter/min pressure air was introduced during nickel deposition.
• the nickel concentration was 67 g/l for all experiments listed in Table 1.
• Table 2 exhibits comparative experiments for bright nickel coatings in accordance with comparative embodiments outside of the present invention.
• the nickel deposition took place for all experiments listed in Table 2 in a Hull cell at a temperature of 55°C +/- 3 °C as in the experiments listed in Table 1. Further, 3 liter/min pressure air was introduced during nickel deposition. The respective columns are showing the number of the experiment, the used acid as complexing agent, the concentration of the acid used as complexing agent, the pH-value of the nickel bath, the applied current in Ampere (A), the nickel ion concentration in g/l, the application time of the current in minutes, and the achieved result of the nickel coating (columns have been described from the left to the right of Table 2). Table 2: Comparative experiments for bright nickel coatings Exp.
• Experiments 30 to 35 show comparative experiments making use of the same respective acids as complexing agent as in certain experiments in Table 1, but with a different concentration. Experiments 30 to 35 all have a too low or too high concentration of the complexing agent for the nickel ions compared to the claimed concentration ranges.
• Table 3 exhibits inventive experiments for bright nickel coatings in accordance with further embodiments of the present invention.

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• Electroplating And Plating Baths Therefor (AREA)
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