US3537959A - Electroplating baths and process for producing bright zinc deposits - Google Patents

Electroplating baths and process for producing bright zinc deposits Download PDF

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Publication number
US3537959A
US3537959A US640383A US3537959DA US3537959A US 3537959 A US3537959 A US 3537959A US 640383 A US640383 A US 640383A US 3537959D A US3537959D A US 3537959DA US 3537959 A US3537959 A US 3537959A
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United States
Prior art keywords
zinc
bath
electroplating
acid
baths
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US640383A
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English (en)
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Joachim Korpiun
Hans Joachim
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DR ING MAX SCHLOETTER fur GALVANOTECHNIK
MAX SCHLOETTER fur GALVANOTEC
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MAX SCHLOETTER fur GALVANOTEC
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    • 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

  • Electroplating with such baths is preferably effected at a pH between about 2.5 and about 5.5, a temperature between about C. and about 40 C., and a current density between about 0.5 amp./dm. and about 5 amp./ dmf
  • the baths are able to replace the heretofore used alkaline electroplating zinc baths and are substantially free of the disadvantages of said baths, especially the difficulties encountered in waste disposal.
  • the present invention relates to an acid galvanic electroplating zinc solution or bath and more particularly to an acid zinc bath for depositing semi-bright or fully bright zinc plates or coatings, to a elecroplating process by means of such an acid zinc bath, and to zinc coated artices obtained by electroplating in such a bath.
  • EX- tensively used are bright electroplating zinc baths based on cyanide.
  • cyanide baths have the disadvantage that the used solutions obtained on electroplating must be completely detoxified by destroying their remaining cyanide content to an amount of 0.1 mg./l. of sodium cyanide before they can be discharged into the sewer.
  • Such detoxification is rather expensive so that the economy of the electroplating process when using such cyanide baths is unfavorably affected.
  • cyanide-free alkaline zinc baths have been developed.
  • the zinc is present in the form of a zincate.
  • the use of zincate alone permits only the preperation of baths of moderate zinc concentrations so that, as a result thereof, only comparatively low deposition current densities can be achieved.
  • complex-forming agents are not destroyed when Working up the used solutions. Thus they pass over into the neutralizing plant wherein they prevent removal of zinc, and also of other metals, from the waste Water to an extent as required by law.
  • Acid zinc baths have technically been used for special purposes.
  • the waste solutions remaining after electro- Patented Nov. 3, 1970 ploting with such acid zinc baths can be treated without difficulty in the neutralization step in such a manner that the zinc content of the used solutions to be discharged meets the legal requirements with respect to their disposal.
  • the heretofore known technically useful acid zinc baths have the disadvantage that matte zinc deposits are obtained, on the one hand, while, on the other hand, the throwing power is much lower than that of the known alkaline zinc baths.
  • Another object of the present invention is to provide a simple and effective electroplating process whereby bright to fully bright zinc deposits are obtained under economic conditions.
  • Still another object of the present invention are zinc electroplated articles of bright appearance which articles are obtained by electroplating in an acid electroplating bath of a specific composition to produce bright zinc deposlts.
  • the acid electroplating bath for depositing semi-bright to fully bright zinc plates comprises an aqueous solution of zinc salts, especially of simple, i.e. not complex inorganic zinc salts and preferably of zinc sulfate, zinc chloride, or zinc fluoborate, and others, which may contain, if required, the conductivity improving agents, i.e. so-called conducting salts.
  • the bath according to the present invention contains:
  • the desired efiect i.e. the formation of bright zinc deposits within a wide range of current densities and with a technically satisfactory throwing power is achieved only when adding to the acid zinc bath not only the primary amines but also the condensation products of naphthalene sulfonic acids with formaldehyde.
  • Useful primary amines or polyamines are aliphatic as well as aromatic amines.
  • Preferred amines of this type are, for instance, n-amylamine, n-hexylamine, diethylene triamine, triethylene tetramine, aniline, pand o-toluidine, pand m-amino phenol, oand p-anisidine, and others.
  • the amines start to exhibit their brightening effect when added to the bath in amounts of about 0.5 g./ 1. to about 1.0 g./l. bath.
  • amines of a lower molecular weight usually larger amounts are required than with amines of a higher molecular weight in order to deposit fully bright zinc plates.
  • the primary amines and polyamines are preferably added to the electroplating zinc bath in the form of their acid addition salts such as their hydrochlorides, sulfates and the like.
  • their acid addition salts such as their hydrochlorides, sulfates and the like.
  • an acid preferably a mineral acid is to be added to the bath.
  • the second brightening component is the condensation product of a naphthalene sulfonic acid with formaldehyde containing two or more naphthalene monoor disulfonic acids which are connected with each other by means of methylene bridges.
  • These condensation products are produced according to known methods as they are described, for instance, in Houben-Weyl Methoden der organischen Chemie, vol. XIV/2, page 316; in German Pat. No. 292,531, and in other literature references.
  • the condensation products are added in amounts between about 0.2 g./l. and about 20 g./l. Higher concentrations, although not required, are usually not harmful.
  • the acid zinc electroplating baths according to the present invention are preferably operated at a temperature between about 10 C. and about 40 C. at a pH between about 2.5 and about 5.5. Bright zinc deposits are also obtained at a lower pH-value.
  • the current yield or current efficiency gradually decreases under such con ditions.
  • a further disadvantage is that the anodes start to dissolve even if no current is passed through the bath. As a result thereof the zinc concentration in the bath increase continually. This is not desirable on continuous electroplating operation. At a higher pH-value than about 5.5, basic zinc salts precipitate in the electrolyte.
  • the electroplating bath When adding aliphatic amines, the electroplating bath usually remains colorless even on prolonged operation.
  • Bright zinc deposits or plates obtained by using electroplating baths according to the present invention can be subjected to a postplating treatment whereby they are provided with chromate conversion coatings which convert the zinc surface from the naturally occurring oxide to the one containing hexavalent chromium.
  • Chromate conversion coatings may be colorless or may impart various colors to the zinc deposits such as yellow, brown, or blive. The brightness of the zinc deposit is even enhanced especially by colorless or bluish chromate treatment.
  • the following examples serve to illustrate bright electroplating zinc baths according to the present invention.
  • Semibright to fully bright zinc coatings are deposited from such baths at current densities between about 0.5 amp./ sq. dm. and about 5 amp./ sq. dm. and a bath temperature between about 15 C. and about 30 C.
  • the baths have a throwing power which is good enough to employ them for zinc plating of technical articles in place of alkaline zinc electroplating baths.
  • EXAMPLE 2 One liter of electroplating bath contains:
  • EXAMPLE 3 One liter of electroplating bath contains:
  • EXAMPLE 4 One liter of electroplating bath contains:
  • EXAMPLE 5 One liter of electroplating bath contains:
  • EXAMPLE 6 One liter of electroplating bath contains:
  • hydrochloric acid added to adjust the baths to the indicated pH-value. This adjustment is especially required when the amines are used in the form of the bases and not in the form of their salts.
  • the electroplating baths according to the present invention yield fully bright deposits at the current densities and bath temperatures as given hereinabove.
  • the throlwing power of the bath is highly satisfactory.
  • condensation products of naphthalene sulfonic acids and formaldehyde mentioned hereinabove are those prepared by condensing naphthalene monosulfonic acids with formaldehyde.
  • the amounts of said salt or of the above mentioned condensation products are not dependent on the amounts of the amines added. An addition of 0.5 g. of said salt or said condensation products for each liter of electroplating bath is sufficient. However, preferably larger amounts are added.
  • the conducting salts mentioned hereinabove are alkali metal, ammonium, or magnesium sulfates or chlorides.
  • An acid electroplating bath for depositing semibright to fully bright zinc plate, said bath comprising an aqueous solution of a zinc salt, a primary amine selected from the group consisting of a primary monoamine With at least four carbon atoms in its molecule and a polyamine with at least four carbon atoms in its molecule, and a water-soluble condensation product of a naphthalene sulfonic acid or salt thereof with formaldehyde, said condensation product containing at least two naphthalene sulfonic acid radicals connected with each other by methylene bridges, the primary amine being present in the bath in an amount of at least 0.5 g./l. and the water soluble reaction product being present in an amount of at least 0.2 g./l.
  • the acid electroplating bath according to claim 1 containing, in addition, a conductivity increasing salt selected from the group consisting of an alkali metal sulfate, ammonium sulfate, magnesium sulfate, an alkali metal chloride, ammonium chloride, and magnesium chloride in amount sufiicient to increase the conductivity of said bath.
  • a conductivity increasing salt selected from the group consisting of an alkali metal sulfate, ammonium sulfate, magnesium sulfate, an alkali metal chloride, ammonium chloride, and magnesium chloride in amount sufiicient to increase the conductivity of said bath.
  • the acid electroplating bath according to claim 2 containing, in addition, dimethyl formamide in an amount between about 5 mL/l. and about 100 rnl./ l.
  • the acid electroplating bath according to claim 1 containing, in addition, dimethyl formamide in an amount between about 5 ml./l. and about ml./l.
  • condensation product is the sodium salt of methylene bis-(naphthalene sulfonic acid).
  • a zinc bath comprising an aqueous acidic solution of a zinc salt, a primary amine selected from the group consisting of a primary monoamine with at least four carbon atoms in its molecule and a polyamine with at least four carbon atoms in its molecule, and a water soluble condensation product of a naphthalene sulfonic acid or salt thereof with formaldehyde, said condensation product containing at least two naphthalene sulfonic acid radicals connected (with each other by methylene bridges, the primary amine being present in the bath in an amount of at least 0.5 g./l. and the water soluble reaction product being present in an amount of at least 0.2 g./l.
  • condensation product is the sodium salt of methylene bis- (naphthalene sulfonic acid).

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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)
  • Chemically Coating (AREA)
US640383A 1966-05-26 1967-05-22 Electroplating baths and process for producing bright zinc deposits Expired - Lifetime US3537959A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DESCH39032A DE1253986B (de) 1966-05-26 1966-05-26 Saures galvanisches Glanzzinkbad

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US3537959A true US3537959A (en) 1970-11-03

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US (1) US3537959A (de)
AT (1) AT268806B (de)
BE (1) BE699084A (de)
CH (1) CH489614A (de)
DE (1) DE1253986B (de)
GB (1) GB1145619A (de)
NL (1) NL6706918A (de)
SE (1) SE310297B (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3878069A (en) * 1970-08-15 1975-04-15 Todt Hans Gunther Acid zinc galvanic bath
US4135992A (en) * 1976-12-24 1979-01-23 Basf Aktiengesellschaft Zinc electroplating bath
US5718818A (en) * 1995-02-15 1998-02-17 Atotech Usa, Inc. High current density zinc sulfate electrogalvanizing process and composition

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US905837A (en) * 1906-08-20 1908-12-08 J W Meaker Jr Electrolyte.
US2245086A (en) * 1938-01-10 1941-06-10 Purdue Research Foundation Electrodeposition of zinc
US2355505A (en) * 1941-10-03 1944-08-08 Purdue Research Foundation Electrodeposition of bright zinc
US2384300A (en) * 1937-07-03 1945-09-04 Little Inc A Electrolytic deposition of zinc
US2393741A (en) * 1941-10-03 1946-01-29 Purdue Research Foundation Electrodeposition of bright zinc
US2543545A (en) * 1948-04-02 1951-02-27 Meaker Company Electrodeposition bath for bright zinc
US3219559A (en) * 1958-04-23 1965-11-23 Barnet D Ostrow Additive for level nickel plating

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US905837A (en) * 1906-08-20 1908-12-08 J W Meaker Jr Electrolyte.
US2384300A (en) * 1937-07-03 1945-09-04 Little Inc A Electrolytic deposition of zinc
US2245086A (en) * 1938-01-10 1941-06-10 Purdue Research Foundation Electrodeposition of zinc
US2355505A (en) * 1941-10-03 1944-08-08 Purdue Research Foundation Electrodeposition of bright zinc
US2393741A (en) * 1941-10-03 1946-01-29 Purdue Research Foundation Electrodeposition of bright zinc
US2543545A (en) * 1948-04-02 1951-02-27 Meaker Company Electrodeposition bath for bright zinc
US3219559A (en) * 1958-04-23 1965-11-23 Barnet D Ostrow Additive for level nickel plating

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3878069A (en) * 1970-08-15 1975-04-15 Todt Hans Gunther Acid zinc galvanic bath
US4135992A (en) * 1976-12-24 1979-01-23 Basf Aktiengesellschaft Zinc electroplating bath
US5718818A (en) * 1995-02-15 1998-02-17 Atotech Usa, Inc. High current density zinc sulfate electrogalvanizing process and composition
US6365031B1 (en) 1995-02-15 2002-04-02 Atotech U.S. A., Inc. High current density zinc sulfate electrogalvanizing process and composition
US6585812B2 (en) * 1995-02-15 2003-07-01 Atotech Usa, Inc. High current density zinc sulfate electrogalvanizing process and composition

Also Published As

Publication number Publication date
SE310297B (de) 1969-04-21
DE1253986B (de) 1967-11-09
NL6706918A (de) 1967-11-27
BE699084A (de) 1967-11-03
AT268806B (de) 1969-02-25
GB1145619A (en) 1969-03-19
CH489614A (de) 1970-04-30

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