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
  • C25D3/14—Electroplating: Baths therefor from solutions of nickel or cobalt from baths containing acetylenic or heterocyclic compounds
  • C25D3/18—Heterocyclic compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/625—Discontinuous layers, e.g. microcracked layers

Definitions

• microcrack chromium coatings 204/49 in which an intervening or intermediate coating of [51] CL C23) 5 0 23 5 32 23 5 50 nickel, cobalt, nickel-iron, nickel-cobalt OI iron-cobalt [58] Field 01 Search 204/41, 43 T, 48, 49 is applied to a Substrate and the chwmium coating is electrodeposited thereon.
• the intermediate coating is [56] References Cited applied from a bath containing the metal or metals ,UNITED STATES PATENTS and a pyridine derivative, especially a nicotinic or t (1.
• the invention relates to the formation of microcrack chromium coatings on a substrate and, more particularly, to a method of producing such coatings whereby an intermediate coating is first applied to the substrate.
• the chromium coating is then deposited upon this intervening coating by electroplating from a conventional chromium-plating bath.
• the intervening coating was applied from an electrolyte containing the metal ions and, in addition to-ammonium ion and chloride ion, at least one aromatic, aliphatic or aromatic-aliphatic carboxylic acid, salt or acid anhydride.
• the intervening layer was preferably nickel applied from a bath to which the carboxylic acid was added in the form of its anhydride.
• the carboxylic acid, acid anhydride or salt was provided in a concentration of 5 to 70 grams per liter g/l), in amounts corresponding to the limit of solubility of the carboxylic acid in the bath.
• the carboxylic acid was the aromatic acid phthalic acid and was present in an amount of 20 to 60 g/l.
• the crack count was between 300 and 850 cracks/cm and the ultimate deposited chromium coating fulfilled all of the requirements set forth in the aforementioned application.
• pyridine derivatives including nicotinic acid can be used for the formation of microcrack chr0- mium deposits by incorporating them in baths from which the intervening layer is deposited.
• the pyridine derivatives are added individually or in combination and in amounts between 0.01 and 8 g/l.
• the most reproducible and satisfactory results are obtained when the additive is nicotinic acid or isonicotinic acid and when the additive is present in an amount of 0.01 to 5 g/l preferably about 0.4 g/l. Otherwise the practice set forth in the aforementioned copending application is used. 1
• the microcrack chromium layer may be applied as described in French Pat. No. 1,447,970 or Dettner Elze, Band II pages 184-188, Hanser Verlag, Kunststoff, 1966.
• the intervening coating is a nickel layer deposited from a nickel electroplating bath of conventional composition but including at least 5 g/l of the aromatic carboxylic acid 'with the range of the carboxylic acid being between 5 and g/l but preferably 20 to 60 g/l.
• the nickel-plating bath (or the cobaltcontaining plating bath as the case may be) will contain the usual substances employed in the deposition of the respective coatings. Reference is made in this respect to the ENCYCLOPEDIA OF ELECTROCHEMIS- TRY, Reinhold Publishing Corp., New York 1964.
• the metal ions may be present in an amount ranging from 30 to g/l and will be nickel, cobalt and combinations thereof with one another or with iron, the metal ions being introduced into an aqueous bath in the form of the sulfate, sulfamate, chloride, fluoroborate, fluoride and/or acetate.
• the bath contains 10 to g/ 1 of chloride ion, the chloride being introduced as the nickel, cobalt, iron ammonium, magnesium or alkali metal (lithium, sodium, potassium) chloride. 10 to 100 g/l of ammonium, ion may also be present and, where desired, boric acid is employed in conventional quantities.
• the bath according to the present invention is an aqueous solution containing 100 to 400 g/l (preferably 220 g/l) of NiCl .6H O (or a corresponding cobalt or iron salt in electrochemically equivalent quantity or a mixture of cobalt, nickel and iron salts in electrochemically equivalent quantity) and 10 to 200 g/l (preferably 80 g/l) of ammonium acetate.
• the bath for application of the intervening coating may include the carboxylic acids mentioned earlier and, if desired, one or more brighteners and/or one or more antifoaming surfactants or wetting agents in accordance with conventional principles.
• the bath according to the present invention should be at a pH between 1 and 6 (preferably between 3 and 4) as adjusted with hydrochloric acid or aqueous ammonia, the electrodeposition of the intervening coating should be carried out with a current density up to thirty amperes per square decimeter (Aldm and preferably between 5 and 15 A/dm at a temperature of 20 to 70C (preferably 40 to 45C) and for a period of 10 seconds to 10 minutes(preferably l to 3 minutes).
• a current density up to thirty amperes per square decimeter (Aldm and preferably between 5 and 15 A/dm at a temperature of 20 to 70C (preferably 40 to 45C) and for a period of 10 seconds to 10 minutes(preferably l to 3 minutes).
• the intervening coating is then electroplated with chromium from a sulfuric acidor mixed-acid electrolyte as described in the aforementioned copending application, depending upon the thickness of the chromium coating and the parameters of the chromium plating bath, the ultimate coating has a crack count of 1200 cracks/cm or more.
• the bath for deposition of the intervening layer includes, in addition to the metal ion,
• Isonicotinic acid hydrazide in an amount up to 5 g/l (preferably 0.1 to 0.3 g/l), pyridine-3-carbinol in amounts up to 5 g/l (preferably 0.4 g/l), pyridine-4- aldehyde in amounts up to 5 g/l (preferably 0.2 to 3.4 g/l), L-nicotine in amounts up to 5 g/l (preferably 0.2 to 0.4 g/l), l-(3-pyridyl)-2-(4-pyridyl)-ethylene in an amount up to 2 g/l (preferably 0.1 g/l), 4-pyridylacrylic acid in an amount up to 8 g/l (0.4 g/l preferred), and pyridine-3-aldoxime in an amount up to 5 g/l (preferably 0.2 to 0.4 g/l).
• the corresponding cobalt or iron salt in combination with the cobalt and nickel salt were used in chemically equivalent quantities and in each case the chloride was replaced by the sulfamate, sulfate fluoroboride, fluoride, citrate and acetate with similar results.
• the crack count was increased still further.
• a method of coating a metal substrate with microcrack chromium comprising applying a first metallic layer to said substrate by electroplating nickel, cobalt or a combination of either with the other or with iron onto said substrate from an aqueous acidic electroplating bath containing the respective metal ions, ammo nium ion and chloride ion together with a microcrackincreasing quantity of at least one pyridine derivative and thereafter electrodepositing a chromium layer upon said first layer to produce a microcrack coating, said pyridine derivative being selected from the group which consists of nicotinic acid and isonicotinic acid, isonicotinic acid hydrazide, pydidine-3-carbinol, pyridine-4-aldehyde, L-nicotine l-( 3-pyridyl )-2-( 4- pyridyl)-ethylene, 4-pyridylacrylic acid and pyridine-3- aldoxime and being present in said bath

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Electroplating Methods And Accessories (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (4)

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Citations (8)

• 1972
  • 1972-08-01 DE DE2237807A patent/DE2237807C3/de not_active Expired
• 1973
  • 1973-07-13 GB GB3364073A patent/GB1411312A/en not_active Expired
  • 1973-07-26 IT ITMI1973A27109A patent/IT7327109A1/it unknown
  • 1973-07-30 US US383532A patent/US3901773A/en not_active Expired - Lifetime
  • 1973-08-01 FR FR7328268A patent/FR2213348B2/fr not_active Expired

Patent Citations (8)

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