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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc

Definitions

• One of the objects of the invention is to provide a new and improved method for extending the range of current densities employed in electrodepositing white alloys of zinc and copper from cyanide-zinc-copper plating baths.
• Another object of the invention is to prepare new and useful cyanide-zinc-copper plating baths.
• An additional object of the invention is to provide a new and improved method for electrodepositing bright zinc-copper alloy plates.
• Still another object of the'invention is to provide a method of electroplating. alloys of Zinc and copper whereby a bright zinc-copper alloy plate is obtained on polished steel which can be lacquered or chrome plated directly without bufiing. Other objects will appear hereinafter.
• Dithiobiuret has the following chemical formula Certain methods are known in the art for electrodepositing white alloys of zinc and copper but in order to obtain a bright plate it has heretofore been necessary to use current densities not exceeding about 20 amperes per square foot. One reason for this appears to be that the amount of copper electrodeposited onto the article to be plated increases as the current density increases. When the relative proportion of copper, as compared with that of zinc in the electrodeposited plate, exceeds a certain amount the desired result is not obtained.
• a purifier for example, sodium sulfide, sodium polysulfide, ammonium sulfide or ammonium polysulfides.
• a brightening agent preferably the reaction product of an oxyaldehyde and an amine containing primary and/ or secondary amino groups and a water solubilizing radical such as hydroxy, carboxy or sulfonic radicals or salts thereof.
• Example An electrolyte is prepared by dissolving zinc cyanide, sodium hydroxide and sodium copper cyanide Na2Cu(CN) a in water to produce a bath containing .99 ounce per gallon of'Cu, 4.50 ounces per gallon of Zn, 13 ounces per gal- Ion of total NaCN and 7 ounces per gallon of NaOH. This bath has a pH of about 11.95.
• a brightening agent for example, the product obtained by reacting 10% anisic aldehyde, 5% heliotropin and of mixed isopropanol amines.
• the residue is placed in dry1ng trays Where it may be washed with ice water to remove traces of residual glucose.
• the product is then dried by heating at temperatures below 250 F. until it becomes dry and hard, at which time it is ground in a hammer mill or in some other suitable manner.
• The'sodium polysulfide solution employed in the foregolng example can be prepared by mixing 1200 pounds of sodium sulfide with 480 pounds of powdered sulfur and making up to 480 gallons with water.
• the brightening agent used in the foregoing example is prepared by reacting the anisic aldehyde, heliotropin and the mixedisopropanol amines by heating them together in approximately equimolecular proportions of aldehyde to amine at moderate temperatures up to about F. A slight excess of the amine is preferably employed and the reaction will take place at room temperatures around 75 F.
• the mixed isopropanol amines conslst essentially of 43% tertiary isopropanol amine, 43% secondary isopropanol propanol amine.
• the zinc is present in the electroplatmg bath as complex ions in the form of sodium zinc cyanide, sodium zincate, and zinc gluconate.
• the copper is present as sodium copper cyanide NazCu(CN)s.
• the zinc gluconate and the dithiobiuret may be considered to be carriers, that is, they function to influence gram refinement in the electrodeposited metal and to extend the range of current densities at which the electrodeposition may be effected without burning the metal.
• the anodes employed in electrodepositing an alloy of z nc and copper from a plating bath of the type previously described can be alloys of zinc and copper, for example, an alloy containing 82% zinc and 18% copper.
• a zinc anode can be used and the copper can be added to the bath chemically.
• an external dialysis cell can be used to supply the copper 1ons or both copper and zinc. Because copper dissolves faster than zinc it is also possible to use mixtures of zinc and copper with split anode circuits so that less current is used in dissolving the copper.
• the bath preferably contains 82 parts of zinc to 18 parts of copper, the range may be varied from about 15 to 30 parts of and still obtain a white alloy of zinc and copper.
• the essential feature of the invention is the discovery that dithiobiuret is very effective in making it possible to use higher current densities without burning the electrodepositedplate.
• the aldonic acid derivatives such as zin'c gluco'nate
• the aldonic acid derivatives have an anti-burning effect and make it possible to operate at current densities as high as 25 amper'es per square foot without the addition of the dithiobiuret
• the usable current density is extended to 80 amperes per square foot.
• the brightening agent may be omitted from the bath where the article to be plated is to be subjected to a subsequent butfing operation. in general, however, it is preferable to employ a brightening agent in order to obtain a plated article that has sufficient brightness directly out of the bath to permit lacquering 'or the application of a chromium plate Without the necessity of bufiing.
• Preferred brightening agents for the purpose of the invention are the condensation product of furfural and anthranilic acid, piperonal and anthranilic acid, anisic aldehyde and 2-methyl 'Z-arnino l-propanol, anisic aldehyde and mixed iso'propanol amines, mixtures of piperonal and anisic aldehyde condensed with mixed isopropa'uol amines, mixtures of anisic aldehyde and piperonal condensed with Z-methyl Z-amino l-prop'anol, furfural dispersed with gluconic acid, ani'sic aldehyde dispersed with gluconic acid, piperonal dispersed with gluconic acid, reaction products of gelatin, an aldoriic acid and furfural, reaction products of protein rich seed meals, an aldonic acid and furfural, and other products of a similar nature.
• the plating bath described in the foregoing example represents a preferred manner of practicing the invention.
• other additives may be employed in the bath.
• additional. carriers may be added such as, for example, the protein-aldonicacid reaction products described in U. S. Patent No. 2,458,504.
• protein carriers are reaction products of gelatin or vegetable protein rich seed meals with aldonic acids, i. e., gluconic, mannonic, galactonic and arabonic, or the lactones of these acids.
• the invention is applicable primarily to the plating of predominantly zinc alloys of zinc and copper which have a silvery or whitish appearance it will be understood that the invention can be applied to the plating of brass generally.
• the most important advantage of the invention is the provision of a method and a plating bath which make it possible to plate whitealloys of zinc and copper at much higher current densities than heretofore used. As a result, a plate of a given thickness can be obtained in a much-shorter period of time, thereby speeding up the entire plating operation and greatly increasing the capacity or output of the plating plant.
• a plating bath comprising an alkaline zinc copper cyanide bath containing in solution dithiobiuret, the quantity of dithiobinret being suflicientto extend the usable range of current densities at which white alloys of zinc and copper can be electrodeposite'd from said b'ath.
• a plating bath comprising an alkaline zinc copper cyanide bath containing in solution a zinc" aldonateand dithiobiuret, the: quantity of dithiobiuretbeing sufiicient to extend the usable range of current densities atwhich "from an alkaline zinc copper cyani can be electrodeposite'd from said bath.
• a plating bath comprising an alkaline 'zinc copper cyanide bath containing in solution dithiobiuret, the weight ratio of zinc to copper in said bath being within the range of 85 to 70 parts of zinc to 15 to 30 parts of copper, and the quantity of, dithiobiuret being sufiicient to extend the usable range of current densities atwhich white alloys of zinc and copper can be electrodeposited from said bath.
• a plating bath comprising an alkaline zinc copper cyanide bath containing in solution 0.5 to 12 grams per gallon of dithiobiuret.
• a plating bath comprisingan alkaline zinc copper cyanide bath containing in solution zinc gluconate, a bath soluble condensation product of an oxyaldehyde, and an amine containing amino groups from the grou consisting of primary and secondary amino groups and a water solubilizing radical from the group consisting" of hydroxy, carboxy and sulfonic radicals arid salts thereof effective as a brightening agent for said bath, and a quantity of dithiobiuret, said quantity being 'siifficier'itto extend the usable range of currentdensities at which white alloys of zinc and copper can be electro'deptisited from said bath.
• a plating bath consisting essentially of an alkaline aqueous zinc copper cyanide" bath containing 1-5 to 35 grams per gallon of ziiic "luc'onate, 0.5- to 12 grams per gallon of dithiobiuret, 5 to 30 cc. er gallon of the reaction product of by weight anisic aldehyde, 5% by weight heliotrop'in' and 85% by weightmixed isopropanol amines, a weight ratio of total cyanide to total plating metal within therar'ige of 2.35 to 2.55 and a'weight ratio of zinc to copper within the range from 85 to 70 parts of zinc to to parts of copper.
• a method of electrodepo's'itir'ig an allo'y of zinc and copper which comprises dissolving dithiobiuret in an alka line zinc copper cyanide bath andelectrodepositir'ig an alloy of zinc and copper from said bath onto an object to be plated, the quantity ofdithiobiure't being sufficient to extend the usable range of current densities at which white alloys of Zinc and copper can be electrodeposited from said bath.
• a method ofincrea'sing' the usable current density of an alkaline zinc copper cyanide bath which comprise's'dissolving in said bath 0.5 to 12 grams per gallon of dithiobiuret.
• a method of electrodepositing a white alloy of zinc and copper which comprises electrodep'o'siting said alloy 'de'liath' containing in solution Zinc gluconate and dithiobiuret, the quantity of dithiobiuret being sufiicient toeXtend-the usable range of current densities at which white alloysof zine and copper 11.
• a method of electrodep'ositirig awhile alloy of Zinc and copper which comprises electrode'positing said alloy from an alkaline zinc copper cyanide bath containing'in solution zinc gluconate,dithiobiuret, and a reaction prod net of an oxyaldehyde and an amine containing amino p consitingpt primary and sec ondary amino groups and a water solubilizing radical from the group consisting of hydroxy, carboxy, anc1; sulfonic radicals andsalts thereof, the;quantity of dithiobiuret being suflicient to extend the usable'range'ofeurrentjdensities at which white alloy sot zincand copper can be electrodeposit'ed from saidbath 12.
• a method of electrodepositing a white alloy of zinc and copper which comprises electrodepositing said alloy from an alkaline zincledpper cyajide bathcontaining in solution Zinc gluconate, dithiobiuretand 8 5" to 70 parts of zinc to 15 to 30' partsof copper, the quantity of dithiobiuret being sufiicient to extend the usable range of current densities at which white alloys of zinc and copper can be electrodepo'sited from said-bath;
• a method of electrodepositi'ng awhite alloy of Zinc and copper which comprises electrodepositing said alloy from an alkaline zinc c'opper'-'cyanide bath containing in solution 15 to grams per gallon of zinc gluconate,

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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)

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Cited By (4)

Citations (3)

• 0
  • BE BE511230D patent/BE511230A/xx unknown
  • BE BE511188D patent/BE511188A/xx unknown
• 1951
  • 1951-12-07 US US260578A patent/US2700646A/en not_active Expired - Lifetime
• 1952
  • 1952-03-24 GB GB7566/52A patent/GB716212A/en not_active Expired
  • 1952-04-25 FR FR1056428D patent/FR1056428A/fr not_active Expired
  • 1952-04-26 FR FR1055212D patent/FR1055212A/fr not_active Expired

Patent Citations (3)

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