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

• ABSTRACT This invention relates to a method of producing bright zinc electrodeposits over a wide current density range, free of spores and/or striations, which comprises passing current from an anode to a metal cathode for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode; the current passing through an aqueous bath composition containing at .least one zinc compound providing zinc ions for elec- 18 Claims, No Drawings ZINC ELECTROPLATING PROCESS AND ELECTROLYTE
• This invention relates to the electrodeposition of bright zinc, and is especially useful for plating from non-cyanide baths. More particularly this invention relates to improved zinc plating bath compositions, to methods of using and preparing such bath compositions and to improved surfaces having bright zinc'electrodeposits thereon.
• Alkaline solutions containing complex compounds of zinc and alkaline metal pyrophosphates have been proposed as a replacement for cyanide baths and cyanide processes for the electrodeposition of bright zinc.
• the electrodeposition of zinc using a pyrophosphate bath may give relatively poor low current density coverage, spore" formation, roughness, insufficient brightness, and relatively non-uniform deposits.
• passivation of the anodes may produce undesirable precipitates which in turn can clog filter systems and sometimes results in intermittent operation necessitated by frequent changes of filter media.
• phosphates may also produce waste disposal problems since phosphates are not easily removed and may promote the growth of undesirable aquatic plant life if discharged into streams. These disposal disadvantages further limit the acceptance of pyrophosphate zinc plating bath compositions in industrial applications.
• Non-cyanide zincate zinc plating baths have also been proposed as substitutes for cyanide containing systems.
• the bright plating current density range of these baths is quite limited, making the plating of articles of complex shape difficult, if not impossible. Since the addition of cyanide to these non-cyanide zincate baths greatly improves the bright plate current density range of the deposits, platers tend to add cyanides to their zincate systems, thus negating the noncyanide feature of the original bath.
• neutral, mildly alkaline or mildly acidic noncyanide zinc plating baths containing large amounts of buffering and complexing agents to stabilize both pH and solubilize the zinc ions at the pH values involved have been employed to overcome the objections of using cyanide-based zinc plating processes.
• these zinc baths consist of an aqueous solution containing at least one simple zinc salt, (for example zinc sulfate, zinc chloride, zinc acetate), and an ammonium salt (for example an ammonium halide, or ammonium sulfate).
• the zinc bath may additionally contain an organic zinc complexing agent such as a hydroxy carboxylic acid or salts thereof, ethylenediamine tetraacetic acid or salts thereof, and/or similar materi als to prevent the precipitation of zinc from the bath as' 50 g/l gll 60 g/l ZnCl, NH,CI Citric Acid NH4OH to adjust the pH to some value between eg 4 and 8.
• an organic zinc complexing agent such as a hydroxy carboxylic acid or salts thereof, ethylenediamine tetraacetic acid or salts thereof, and/or similar materi als to prevent the precipitation of zinc from the bath as' 50 g/l gll 60 g/l ZnCl, NH,CI Citric Acid NH4OH to adjust the pH to some value between eg 4 and 8.
• Suitable bath soluble polyoxyalkylene surfactant 6 gll in order to improve and increase the brightness, luster and throwing power of zinc deposits from these baths, certain organic aromatic carbonyl compounds
• mildly acidic, neutral, or mildly alkaline zinc plating baths which may or may not additionally contain organic complexing agents; said deposits being free of objectionable spores and/or striations.
• This invention relates to a method of producing bright to brilliant zinc electrodeposits over a wide current density range, free of spores and/or striations, which comprises passing current from an anode to a metal cathode for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode; the current passing through an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, a suitable bath-soluble surfactant as a support or carrier and at least one compound selected from the class of compounds consisting of aromatic non-carbonyl nitrogen heterocycles.
• aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, a suitable bath-soluble surfactant as a support or carrier and at least one compound selected from the class of compounds consisting of aromatic non-carbonyl nitrogen heterocycles.
• each R is independently hydrogen, alkyl, alkenyl, alkoxy, alkylamine, alkylsulfonic acid and/or salt thereof, sulfonic acid and/or salt thereof, halogen, amine, hydroxyl, mercapto, nitrile, benzyl, or phenylal- (where m is an integer 0 to 4); n is an integer t) to 3; R is a divalent alkylene, divalent alkeneylene, secondary amine.
• R' is a bifunctional radical such as z is 0 or 1
• Y is oxygen, allyl, propargyl, benzyl, an alkoxy group, alkyl sulfonic acid -(CH ),,-SO (where p is an integer of from I to 4), an oxyalkylsulfonic acid, quinaldinyl, halogenated alkeneyl radicals such as omatic non-carbonyl nitrogen heterocyclic compounds which'may be employed according to this invention and the radical p-phenoxybenzyl and which illustrate the generalized structural formulae given above.
• N-(2 3-dichioro-Z-D ropeny C1 C1 guinolinlum O N CH. H iodide.
• N-propargyluinolinlum gromide N-propargyluinolinlum gromide
• the amount of heterocyclic nitrogen compound or mixtures thereof employed in the compositions of this invention is an amount sufficient to provide improved bright zinc electroplate when compared with a bath composition which is identical'lnall respects save that said bath composition contains no heterocyclic nitro gen compounds of the invention herein.
• the improved bright zinc electroplate deposits of the invention herein are generally characterized as showing improvement in at least one of the properties such as freedom from dullness or skip in lower current density areas, improved ductility, uniformity of lustrous deposit throughout the plating current density range and freedom from spores and/or striations.
• amounts of heterocyclic nitrogen compounds of about 0.001 g/l-4.0 g/l (preferably about 0.005 025 g/l) may be used.
• aromatic non-carbonyl containing nitrogen 'heterocyclic compounds of this invention are employed in mildly acidic, neutral, or mildly basic zinc electroplating baths, they are preferably used in combination with carrier and/or support compounds known to those skilled in the art of zinc plating.
• carrier and/or support compounds are typically bath soluble polyethers, substituted polyethers and/or substituted nonaromatic nitrogen heterocyclic surfactants.
• a bath soluble surfactant which may be employed in amounts of about 10-25 3/! (preferably about 2-10 g/l) in combination with the nitrogen heterocyclic compounds in amounts of about 0.001 g/l-4.0 g/l (preferably about 0.0050.25 g/l) may include aromatic ethers of aliphatic polyethers.
• the polyether is a polyalkoxylated alkyl phenol.
• Typical polyalkoxylated alkyljphenols include polyethoxylated alkyl phenols havingthe' formula:
• R represents an alkyl group of from 8 to 16 carbon atoms (preferably 8 or 9 carbon atoms) and j is an integer of from to 50 (preferably from about 10 to 30), and Q is hydrogen or methyl.
• polyethers which may be employed in amounts of about 10-25 g/l (preferably about 2-10 g/l) in combination with the nitrogen heterocyclic compounds in amounts of about 0.00l-4.0 g/l (preferably about 0.005-025 g/l) may include aliphatic polyethers characterized by the following general formula:
• Q represents hydrogen or methyl and k is an integer of from about 7 to 100 (preferably from about 12 to 50).
• polyethers which may be employed include alkyl polyethers of the general formula:
• Q represents hydrogenor methyl and R5 isan alkyl group of from about 5 to 25 carbon atoms and h is an integer from about 10 to 50 (preferably about 12 to 25).
• bath soluble surfactants which may be employed include quaternary imidazolinium compounds with the following generalized structural formula:
• N -H-CHI where q is an integer of from about 50 to 5000 (preferably from about to 3500).
• the nitrogen heterocyclic compounds and the polyether compounds used in combination in the novel bright zinc electroplating baths of the invention may contain inert substituents.
• an inert substituent as the term is used herein is meant any bath compatible group which does not destroy, reduce, interfere with, or hinder the formation of the bright zinc electrodeposits described herein.
• Typical examples of inert substituents include the halogens (chloride, bromide, iodide, and fluoride); hydroxy groups, alkoxy groups (such as methoxy, ethoxy, propoxy, etc.), alkyl groups, sulfate, etc.
• a mixture of the nitrogen heterocyclic compounds and the carrier and/or support compounds may be employed in combination with other additives.
• examples of such cooperating mixtures include a 50:1 (parts by weight) combination of the reaction products of nonyl phenol with about 15 moles of ethylene oxide and a nitrogen-containing heterocyclic compound.
• Other suitable weight ratios of carrier and- /or support compounds (polyether) and nitrogencontaining heterocyclic compounds include weight ratios of about [00:1 to l/2:l, respectively.
• Mixtures of nitrogen heterocyclic compounds may also be used and wherever mixtures of nitrogen heterocycliccompounds are employed, the weight ratios referred to herein refer to the total weight of all of the nitrogen heterocyclic compounds combined.
• the basis metal onto which the bright zinc deposits of this invention may be applied may include ferrous metals such as steel and cast iron; copper including its alloys such as brass, bronze, etc.; die cast metals which may bear a plate of another metal such as copper; thin coatings, e.g. of silver, nickel, or copper, on a nonconductive "mime” (sifchasa- "r'rgra offfexible plastic) which coating may be applied by chemical reductive techniques, such as electroless plating, etc.
• the preferred operating conditions such as pH, temperature, and current density may vary depending upon the par ticular bath composition and the nature of the article receiving the layer of bright zinc electrodeposit.
• good, bright, zinc electrodeposits may be obtained within a specific range of operating conditions.
• a zinc electrodeposit may attain maximum brightness and the current efficiency may also be optimized.
• the bright zinc electroplating processes using the compositions of the invention may be carried out at temperatures of about l0C.-60C. (preferably 15C.-35C.) either with or without agitation.
• average current densities of 0.5-5.0 amperes per square decimeter (ASD) bright zinc electrodeposits having average thicknesses of 025-25 microns may be obtained using plating times which may average 0.5- minutes.
• agitation of the plating bath composition may be provided either by mechanical movement of the article being plated or by solution agitation during the electrodeposition. Such agitation may permit the use of high plating current densities on the article being plated.
• Some of the nitrogen heterocyclic compounds of this invention may have only limited solubility in aqueous solutions.
• a suitable bath soluble solvent include methanol, ethanol, isopropanol, ethylene glycol-monoethyl ether (i.e., cellosolve), acetone, etc.
• a concentration of about 25 to 50 g/l of the nitrogen heterocyclic compounds in a suitable solvent provides a satisfactory stock solution for addition to the plating bath. In this manner the nitrogen heterocyclic compounds of this invention can be easily added to the plating solution while obtaining rapid dispersion and optimum miscibility.
• ZnCl 32 g/l NH Cl 200 g/l pH Reaction product of a mixture of linear secondary alcohols exhibiting ll to 16 carbon atoms with l2 moles of ethylene oxide 4 g/l 2-mercapto-4-methylpyridine 0.04 g/l N-(2.3-dichloro-2-propenyllisoquinolinium iodide 0.025 g/l
• This bath composition was operated in a 267 ml Hull cell at room temperature, using 1 ampere cell current,
• EXAMPLE VII A four liter aqueous bright zinc electroplating bath composition containing the following ingredients in the amounts indicated was prepared:
• the resulting zinc deposits were brilliant and lustrous as plated, free of any haziness, spores and/or striations.
• the deposits were subsequently rinsed and given a clear chromate conversion coating to improve their corrosion resistance as is normal in the zinc plating industry.
• a method of producing bright, or brilliant zinc electrodeposits free of spores" and/or striations over a wide current density range which comprises passing current from an anode to a metal cathode through an aqueous bath composition having a pH of 1.0 to 10.0 and containing at least one zinc compound providing zinc ions for electroplating zinc,
• bath soluble surfactant selected from the group consisting of bath soluble polyethers, substituted polyethers, and substituted non-aromatic nitrogen heterocyclic surfactants selected from the group consisting of quaternary imidazolinium compounds and polyvinylpyrrolidone polymers;
• At least one nitrogen-containing heterocyclic compound is of the formula wherein each R is independently hydrogen, alkyl, alkenyl, alkoxy, alkylamine, alkysulfonic acid or salts thereof, sulfonic acid or salts thereof, halogen, amine, hydroxyl, mercapto, nitrile, benzyl, or phenylalkyl (where m is an integer 0 to 4 nis anin teger 0 to 3; z is 0 or 1; Y is oxygemallyl, propargyl.
• benzyl an alkoxy group, alkyl sulfonic acid -(CH ),,-SO (where p is an integer of from 1 to 4), an oxyalkylsulfonic acid, quinaldinyl.
• p-phenoxybenzyl, or a halogenated alkeneyl radical and X represents an anionic radical or the anionic moiety of Y or R-provided that when Y is oxygen X is'absent.
• At least one bath-soluble surfactant is a polyether of the formula:
• R is an alkyl group of 8-16 carbon atoms.
• j is an integer 5-50 and Q is hydrogen or methyl.
• At least one bath-soluble surfactant is a polyvinylpyrrolidone of the formula:
• q is an integer of from about 50 to 5000.
• a composition for providing bright, or brilliant zinc electrodeposits free of spores and/or striations 1 over a wide current density range which comprises an aqueous bath composition having a pH of 1.0 to 10.0 and containing at least one zinc compound providing zinc ions for electroplating zinc,
• bath-soluble surfactant selected from the group consisting of bath-soluble polyethers, substituted polyethers, and substituted non-aromatic nitrogen heterocyclic surfactants selected from the group consisting of quaternary imidazolinium compounds and polyvinylpyrrolidone polymers;
• composition as claimed in claim wherein at least one nitrogen-containing heterocyclic compound is of the formula:
• each R is independently hydrogen, alkylfalk enyl, alkoxy, alkylamine, alkylsulfonic acid or salts thereof, sulfonic acid or salts thereof, halogen, amine, hydroxyl, mercapto, nitrile, benzyl, or phenylalkyl (where m is an integer O to 4)j n is an integer 0 to 3 z is 0 or 1; Y is oxygen, allyl, propargyl, benzyl, an alkoxy group, alkyl sulfonic acid (CH ),,SO p is an integer of from 1 to 4), and oxyalkylsulfonic acid,
• X represents an anionic radical or the anionic moiety of Y or R provided that when Y is oxygen X is absent.
• composition as claimed in claim 11 wherein at least one nitrogen-containing heterocyclic compound is isoquinoline.
• a composition as claimed in claim 11 wherein at least one nitrogen-containing heterocyclic compound is N-allylisoquinolinium bromide.
• a composition as claimed in claim 11 wherein at least one nitrogen-containing heterocyclic compound is N-(2,3-dichloro-2-propenyl)-isoquinolinium iodide.
• a composition as claimed in claim 11 wherein at least one nitrogen-containing heterocyclic compound is N-benzylisoquinolinium chloride.
• composition as claimed in claim 10 wherein at least one bath-soluble surfactant is a polyether of the formula:
• At least one bath-soluble surfactant is a polyvinylpyrrolidone of the formula:

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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)
• Pyridine Compounds (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Compositions Of Oxide Ceramics (AREA)

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• 1972
  • 1972-09-26 US US00293659A patent/US3821095A/en not_active Expired - Lifetime
• 1973
  • 1973-07-31 ZA ZA735205A patent/ZA735205B/xx unknown
  • 1973-08-01 IL IL42867A patent/IL42867A/en unknown
  • 1973-08-23 CA CA179,523A patent/CA1020901A/en not_active Expired
  • 1973-09-07 FR FR7332382A patent/FR2200370B1/fr not_active Expired
  • 1973-09-11 BE BE135556A patent/BE804733A/xx not_active IP Right Cessation
  • 1973-09-21 NO NO3715/73A patent/NO134529C/no unknown
  • 1973-09-24 GB GB4471573A patent/GB1394637A/en not_active Expired
  • 1973-09-25 CH CH1373973A patent/CH601501A5/xx not_active IP Right Cessation
  • 1973-09-25 ES ES419035A patent/ES419035A1/es not_active Expired
  • 1973-09-25 IT IT9627/73A patent/IT1005144B/it active
  • 1973-09-25 CS CS6595A patent/CS166677B2/cs unknown
  • 1973-09-25 DE DE19732348190 patent/DE2348190A1/de not_active Ceased
  • 1973-09-26 JP JP48108318A patent/JPS4972138A/ja active Pending
  • 1973-09-26 NL NL7313268A patent/NL7313268A/xx not_active Application Discontinuation

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