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
  • C25D3/22—Electroplating: Baths therefor from solutions of zinc

Definitions

• the present invention relates to a method for obtaining a bright zinc coating in the electrodeposition of zinc from an alkaline bath.
• the conventional baths for obtaining bright zinc coatings have a cyanide content amounting to about 80 to 150 g./l. of sodium cyanide.
• the removal of the poisonous cyanides from the rinse water and sewage as required by law and health regulations can be carried out only at a very great expense, and the required safety measures render a zinc plating by means of cyanide baths so expensive that in many cases it can no longer be carried out economically.
• alkaline zinc baths which are free of cyanide and therefore do not have the mentioned disadvantages are also known, such baths, aside from having a lower electrolytic efliciency than cyanide baths, also do not produce any bright zinc deposits as are attained by cyanide baths.
• Zinc plating is, however, increasingly in demand and for many purposes it is of a much greater value than coatings of other materials.
• the other admixtures of the bath according to the invention for example, brighteners, agents for preventing voids, other kinds of metals, protective colloids, and others are well known in cyanide zinc baths. These include, for example, piperonal, vanillin, anisaldehyde, salicylic aldehyde, gelatin, dextrin compounds of molybdenum, chromium, mangnese, selenium or tellurium, surface-active compounds, and the like.
• the bath according to the invention further contains the usual amounts of a zincate which may be produced by dissolving zinc or a zinc compound (for example, zinc oxide, zinc sulphate, or zinc chloride) in alkalis, such as free alkali metal hydroxides.
• a zincate which may be produced by dissolving zinc or a zinc compound (for example, zinc oxide, zinc sulphate, or zinc chloride) in alkalis, such as free alkali metal hydroxides.
• the precipitation of the bright zinc coatings is carried out at room temperature and up to about 45 C. and at a current density of about 1 to 4 a./dm. and in the course of the electrolysis the. mentioned admixtures are added as desired.
• the plating process is carried out in the conventional manner either by agitating the electrolyte or by moving the material to be plated or by changing the polarity.
• Example 1 40 g. of zinc oxide together with g. of sodium hydroxide are dissolved in 1 liter of water, and hereto are added: 0.8 to 2.0 g. of white gelatin, dissolved in water; 0.2 to 0.4 g. of piperonal, dissolved in alcohol; and 10 to 20 cc. of triethanolamine.
• a wetting agent may be added, for example, one based on fatty alcohol sulphonates in an amount of 2 to 10 g./l.
• the electrolysis is carried out at 2 a./dm. and 1.2 to 1.5 v. and at room temperature.
• the plating period amounts to about 10 minutes.
• the precipitation amounts to about 0.5 ,u/min.
• the cathode is provided in the form of iron plates.
• Example 2 14 g. of crystallized zinc sulphate together with 230 g. of sodium hydroxide are dissolved in 1 liter of water, and hereto are added:
• Example 3 The following compounds are dissolved in 1 liter of water:
• Example 4 From an electrolyte which contains the following components dissolved in 1 liter of water, glossy perfect zinc coatings are attained at 1 to 3 a./dm. and 1.4 to 1.6 v. and at a room temperature of 18 to 25 C.:
• a method for obtaining a bright zinc coating which comprises exposing the object to be coated as a cathode in an aqueous cyanide-free alkaline zinc bath consisting essentially of a zincate selected from the group consisting of zinc and zinc compounds dissolved in an alkali metal hydroxide solution and an amine, and passing a current in said bath from anode to said cathode.
• said alkaline zinc bath also contains at least one additive selected from the group consisting of the conventional lustering and wetting agents therefor and said amine is selected from the group consisting of the alkanolamines, hexamethylenetetramine and mixtures thereof.
• a cyanide-free alkaline zinc bath for use in the electrodeposition of bright zinc coatings consisting essentially of an aqueous alkaline solution containing a substance selected from the group consisting of zinc and zinc compounds and an alkali metal hydroxide, and an additive therefor consisting essentially of an amine selected from the group consisting of the alkanolamines, hexamethylenetetramine and mixtures thereof, the ratio of said amine to said solution being from about 4 grams per liter to about 60 grams per liter.

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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)
• Materials Applied To Surfaces To Minimize Adherence Of Mist Or Water (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Anti-Oxidant Or Stabilizer Compositions (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (5)

Cited By (16)

Families Citing this family (1)

Citations (2)

• 0
  • NL NL280407D patent/NL280407A/xx unknown
  • NL NL133471D patent/NL133471C/xx active
• 1961
  • 1961-07-06 DE DESCH29958A patent/DE1150255B/de active Pending
• 1962
  • 1962-07-03 US US207426A patent/US3317412A/en not_active Expired - Lifetime
  • 1962-07-03 CH CH798962A patent/CH414300A/de unknown
• 1963
  • 1963-04-09 GB GB14134/63A patent/GB981516A/en not_active Expired

Patent Citations (2)

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