US3806431A - Zinc electroplating bath having low cyanide content - Google Patents

Zinc electroplating bath having low cyanide content Download PDF

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Publication number
US3806431A
US3806431A US00249628A US24962872A US3806431A US 3806431 A US3806431 A US 3806431A US 00249628 A US00249628 A US 00249628A US 24962872 A US24962872 A US 24962872A US 3806431 A US3806431 A US 3806431A
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zinc
alkanolamine
aldehyde
bath
cyanide
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Expired - Lifetime
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US00249628A
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English (en)
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R Koch
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Individual
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Priority to DENDAT2123108 priority Critical patent/DE2123108A1/de
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Priority to US00249628A priority patent/US3806431A/en
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00Electroplating: Baths therefor
    • C25D3/02Electroplating: Baths therefor from solutions
    • C25D3/22Electroplating: Baths therefor from solutions of zinc
    • C25D3/24Electroplating: Baths therefor from solutions of zinc from cyanide baths

Definitions

  • a bath for electroplating zinc containing in aqueous solution a zinc salt, an alkali metal cyanide, an alkali metal hydroxide, an aldehyde-alkanolamine condensation product, a water soluble polyvinyl alcohol and optionally salts of metals of Groups VII-B or VIII of the Periodic Table of Elements and further tricrotonylene tetramine and trithione (3-thio-3H-l,2-dithiole), said bath having a low cyanide content, yields highly brilliant zinc coatings with very good throwing power and metal distribution.
  • Preferred aldehyde-alkanolarnine condensation products are condensation products of a mono-alkanolamine with an aromatic aldehyde of the general formula CHO wherein R is hydroxyl and/or lower alkoxy having from 1 to 4 carbon atoms and x is zero, one, or two.
  • the invention BACKGROUND OF THE INVENTION
  • the invention relates to a zinc electroplating bath having a low cyanide content.
  • cyanide containing electroplating baths for depositing zinc on, e.g., iron.
  • the zinc deposits obtained with the known baths may have good throwing power, brilliance and a good metal distribution.
  • the addition of brighteners to the electroplating baths is required.
  • As brighteners for this purpose aldehyde-alkanolamine condensation products, water soluble polyvinyl alcohol and salts of metals of Group VII-B or Group VIII of the Periodic Table are known. Since the problem of water pollution and the costly measures of freeing waste water from poisonous substances gain growing importance the use of cyanide containing electroplating baths recently has decreased considerably. At present increasingly weak acid or alkaline zinc electroplating baths with no cyanide or having a low cyanide content are used which, however, usually do not provide the brilliance of cyanide containing zinc electroplating baths.
  • the cyanide content of the bath of the invention may be lowered from the normal content of 80 g. to 150 g./l. to a level of from g. to 25 g./l. without adversely affecting the zinc deposit obtained.
  • It is a further object of the present invention to provide an alkaline zinc electroplating bath comprising in aqueous solution a zinc salt, one or more aldehyde-alkanolarnine condensation products, water soluble polyvinyl alcohol and optionally salts of a metal of Groups VII- B or VIII of the Periodic Table of Elements and, in addition, tricrotonylene tetramine and trithione (3-thio-3H-l,2-dithiole).
  • additives such as additional brighteners may be used.
  • the zinc electroplating bath according to the invention preferably contains 0.1 g. to 1.0 g./l. of tricrotonylene tetramine. Most preferred is an amount of 0.1 g. to 0.5 g. of tricrotonylene tetramine per liter of the zinc bath.
  • the preferred amounts of trithione in the zinc bath are 0.01 g. to 0.05 g./l., in particular 0.01 g. to 0.02 g./l.
  • Preferred aldehyde-alkanolamine condensation products are condensation products of a lower mono-alkanolamine, such as mono-ethanolamine and of an aldehyde of the formula OHO - (R); wherein R is hydroxyl and/or lower alkoxy having 1 to 4 carbon atoms, in particular methoxy, and x is zero, one, or two.
  • Preferred aldehydes are salicylaldehyde, anisaldehyde, vanillin, or veratraldehyde.
  • unsaturated aromatic aldehydes such as cinnamic aldehyde, or formaldehyde can also be used.
  • the amount of the aldehyde-alkanolamine condensation product is preferably between 0.2 g. and 2 g./l. of the bath, in particular between 0.3 g. and 1 g./l., as the salt of a metal of Group VII-B or Group VIII of the Periodic Table, a salt of manganese, cobalt or nickel is preferred.
  • Said salt is used in amounts between 0.01 g. and 0.1 g./l. preferably between 0.01 g. and 0.05 g./l.
  • Polyvinyl alcohol is preferably used in an amount between 0.01 g. and 0.5 g./l., in particular between 0.1 g. and 0.5 g./l. of the bath.
  • EXAMPLE II 0.5 g./l. of a condensation product of mono-ethanolamine and vanillin, 0.2-0.4 'g./l. of tricrotonylene tetramine, 0.01-0.05 g./l. of trithione,
  • EXAMPLE III Smooth and bright zinc coatings on iron having good throwing power and metal distribution were obtained by using an electroplating bath of the following composition:
  • a zinc electroplating bath comprising, in aqueous solution,
  • a zinc salt in an amount equivalent to between about 7 g./l. and about 15 g./l. of zinc oxide
  • the zinc electroplating bath of claim 1 in which the condensation product of an aldehyde with an alkanolamine is the condensation product of a lower mono alkanolamine and an aromatic aldehyde of the formula OHO ('R) z in which R is a member selected from the group consisting of hydroxyl and lower alkoxy with 1 to 4 carbon atoms, and x is one of the numerals 0, 1, and 2.
  • a zinc electroplating bath comprising, in aqueous solutions,
  • a zinc salt in an amount equivalent to between about 7 g./l. and about 15 g./l. of zinc oxide

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (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)
US00249628A 1972-05-02 1972-05-02 Zinc electroplating bath having low cyanide content Expired - Lifetime US3806431A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DENDAT2123108 DE2123108A1 (OSRAM) 1972-05-02
US00249628A US3806431A (en) 1972-05-02 1972-05-02 Zinc electroplating bath having low cyanide content

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US00249628A US3806431A (en) 1972-05-02 1972-05-02 Zinc electroplating bath having low cyanide content

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3915815A (en) * 1972-11-15 1975-10-28 Reinhard Koch Alkaline zinc electroplating bath
US4169772A (en) * 1978-11-06 1979-10-02 R. O. Hull & Company, Inc. Acid zinc plating baths, compositions useful therein, and methods for electrodepositing bright zinc deposits

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3915815A (en) * 1972-11-15 1975-10-28 Reinhard Koch Alkaline zinc electroplating bath
US4169772A (en) * 1978-11-06 1979-10-02 R. O. Hull & Company, Inc. Acid zinc plating baths, compositions useful therein, and methods for electrodepositing bright zinc deposits

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Publication number Publication date
DE2123108A1 (OSRAM)

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