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

• This invention relates to an acidic bath for electroplating zinc suitable for forming glossy zinc platings having dense crystal structures under high current densities.
• the prior art acidic zinc plating bath utilizes zinc sulfate, zinc chloride or zinc fluoroborate or the like as the source of Zn ions.
• sulfate or chloride is often added to the bath.
• the surface of the platings is coarse and is not glossy.
• large crystals are formed.
• it has been proposed to add a small quantity of an organic substance such as extract of licorice, glue, gum arabic, dextrose, B naphthol or the like into the bath.
• an acidic bath for electroplating zinc which comprises a mixture of an aqueous solution containing 200 to 650 g/l of zinc sulfate, 50 to 200 g/l of zinc chloride, 10 to 70 g/l of ammonium chloride, 5 to 30 g/l of sodium succinate and at least one member selected from the group consisting of 0.1 to g/l of nicotinic acid amide and 0.01 to 0.1 g/
• Zinc sulfate and zinc chloride are used as the source of Zn iOns, and their concentrations are determined on the following basis. More particularly, with a concentration of zinc sulfate of less than 200 g/l it is impossible to use high current densities because the surface of the platings is burnt, whereas with a concentration above 650 g/l, there is a tendency to form precipitates. Said precipitates are zinc ammonium sulfates, which taint a conductor roll for passing an electrical current or precipitate on the surface of plating film to deteriorate the plating film.
• the concentration of zinc chloride at a concentration of less than 50 g/l, the conductivity is too low to provide high current densities, whereas at a concentration above 200 g/l, the appearance of the platings becomes poor when they are treated with a phosphate or chromic acid.
• ammonium chloride The purpose of incorporation of ammonium chloride is to improve conductivity. At a concentration of less than 10 g/l, the purpose of ammonium chloride can not be attained whereas at a concentration above 70 g/l, there is a tendency to form precipitates.
• pH of the electrolytic bath is between 3.5 and 4.5 and most desirably pH is about 4.0.
• pH of the electrolytic bath above 4.5 would cause precipitation of compounds of Fe and Zn.
• pH of the electrolytic bath below 3.5 would cause generation of hydrogen in the bath, which would be absorbed by the plating film and cause pin holes in the said plating film.
• the principal function of sodium succinate is to stabilize the pH of the plating bath. At a concentration of sodium succinate of less than 5 g/l, the action thereof for buffering the pH is not sufficient whereas at a concentration above 30 g/l, the advantage of the sodium succinate is not increased.
• Nicotinic acid amide and ethoxylated-a-naphthol sulphonic acid are incorporated for the purpose of providing dense and glossy plated surfaces. They can be used singly or in combination. Incorporation of these compounds forms fine crystals thus providing smooth, glossy and beautiful plated surfaces.
• a quantity of 0.1 to 10 g/l is suitable for nicotinic acid amide.
• a concentration of less than 0.1 g/l is not effective, whereas a concentration of more than 10 g/l does not increase the desired advantage.
• a suitable concentration of ethoxylated-a-naphthol sulphonic acid is from 0.01 g/] to 0.1 g/l.
• a concentration of less than 0.01 g/] is not efficient, whereas a concentration of above 0.1 g/l forms pin holes in the plated surfaces, and blakish plated surfaces of poor appearance;
• EXAMPLE 1 A cold rolled steel plate was plated under following conditions. Composition of the bath:
• Nicotinic acid amide (C H N,O) 5 g/l Current density 60 A/dm Plating period 8 sec.
• Zinc sulfate ZnSO '7H O
• Zinc chloride ZnCl,
• NI-I Cl Zinc chloride
• NI-I Cl Sodium succinate((CH COONa) '6H O)
• Ethoxylated-a-naphthol sulphonic acid 0.05 gll (CIZHILIOZS) 80 A/dm 4 sec.
• said bath comprises an aqueous solution of 200 to 650 g/l of zinc sulfate, 50 to 200 g/l of zinc chloride, 10 to g/l of ammonium chloride, 5 to 30 g/l of sodium succinate and at least one member selected from the group consisting of 0.1 to 10 g/l of nicotinic acid amide and 0.01 to 0.1 g/l of ethoxylated-anaphthol sulphonic acid.
• a method of electroplating zinc comprising electroplating zinc at a current density of from 10 A/dm to A/dm at a cathode immersed in the bath of claiml.

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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)

Family

ID=14033634

Family Applications (1)

Country Status (9)

Cited By (4)

Families Citing this family (4)

Citations (1)

• 1971
  • 1971-11-16 JP JP46091695A patent/JPS513298B2/ja not_active Expired
• 1972
  • 1972-10-06 CA CA153,451A patent/CA1008797A/en not_active Expired
  • 1972-10-09 GB GB4645872A patent/GB1360715A/en not_active Expired
  • 1972-10-11 US US00296636A patent/US3766024A/en not_active Expired - Lifetime
  • 1972-10-16 ZA ZA727332A patent/ZA727332B/xx unknown
  • 1972-10-18 DE DE2251103A patent/DE2251103C3/de not_active Expired
  • 1972-11-13 FR FR7240151A patent/FR2160426B1/fr not_active Expired
  • 1972-11-14 AU AU48825/72A patent/AU472938B2/en not_active Expired
  • 1972-11-15 IT IT31711/72A patent/IT970916B/it active

Patent Citations (1)

Non-Patent Citations (1)

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