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

• X is S- or A is independently selected from the group consisting n is or 1; when n is 0, nitrogen is doubly bonded to carbon in A; with the proviso that when n is 0, A is R and R are independently selected from the group consisting of hydrogen, alkyl of l to 4 carbon atoms, phenyl; and may be joined to form a six membered aromatic carbocyclic ring and R is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl.
• Zincate plating baths have been used as a means of electrodepositing zinc without employing cyanide ions due to the difficulty in disposing of cyanide ions in waste efiluent.
• Some conventional zinc brighteners produce a bright deposit but only over a narrow current density range.
• the high current density areas generally resulted in a spongy or burnt deposit. It has been found through the combination of brighteners employed in the present case to obtain not only a bright deposit, but also a deposit over a wide current density area.
• a method for obtaining a bright zinc electrodeposit over a wide current density area from a zincate electroplating bath by employing a combination of additives, the first being a polyethyleneimine and the second one being a heterocyclic nitrogen containing compound.
• X is S or I NR,
• A is independently selected from the group consisting n is 0 or 1; when n is 0, nitrogen is doubly bonded to carbon in A; with the proviso that when n is 0, A is R and R are independently selected from the group consisting of hydrogen, alkyl of 1 to 4 carbon atoms, phenyl; and may be joined to form a six membered aromatic carbocyclic ring and R is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl.
• Zincate plating baths are those which generally contain zinc oxide and caustic, such as sodium hydroxide.
• the amount of sodium hydroxide that may be employed ranges from 50 to 250 grams/liter, preferably from about to about 200 grams/liter, while the amount of zinc oxide ranges from 5 to 50 grams/liter, preferably from about 8 to about 30 grams/liter.
• the processing parameters are such that normally atmospheric temperature and pressure is employed, although temperatures up to 55 C. may also be employed, and even more preferably 15 to about 45 C.
• the cathode current density ranges from about 5 to 25 amps per sq. ft. while the anode current density ranges from about 10 to 35 amps per sq. ft. where the zinc deposition can occur with agitation.
• agents may also be present in the bath, such as those described in the above patents.
• suitable agents may be anisaldehyde, glue, polyvinyl alcohol and the glycerol ester of polyvinyl alcohol wherein these alcohols have a molecular weight of 5,000 to 20.- 000.
• Other polymers that may be employed are gelatin, peptone, and the like.
• chelating agents or agents which can form a complex with the metal zinc in the bath may also be employed, such as nitrilotriacetic acid and the various alkali metal salts, such as the sodium salt, ethylenediaminetetraacetic acid, and its water soluble salts, such as sodium, and the like.
• the polyethyleneimine that may be used in the present case has a molecular weight ranging from 1,000 to 400,- 000, preferably 600 to 60,000 where the percentage of primary, secondary and tertiary nitrogen atoms is about 25, 50, and 25% respectively.
• a zincate bath that may be employed in the present invention is as follows:
• the bath pH may be adjusted by adding NaOl-I.
• Some of the nitrogen heterocylic compounds that may be employed in the present invention are as follows.
• water solubilizing group any substituent on the six membered carbocyclic ring which will improve the water solubility of the compound.
• Such groups are hydroxy, alkoxy, such as methoxy or ethoxy and the like, carboxy, amino, and the like.
• R may be other groups which are not detrimental to the electrodeposition of zinc such as chloro, bromo, cyano (CN), nitro and the like.
• EXAMPLE 1 A zincate plating bath was formulated containing the following components and was used to electrodeposit zinc onto a steel substrate at a cathode current density of ASP and a temperature of 75 F.
• the initial bath pH is about 14.
• EXAMPLE 2 Zincate plating bath similar to the above was also prepared but further including 0.1 g./l. of polyvinyl alcohol. A bright zinc deposit was obtained over a broad current density range following the procedure of Example #1.
• Example 3 The procedure of Example #1 was followed, except that the bath also contained 0.1 grams/liter of anisaldehyde with equivalent results being obtained.
• Example 4 The procedure of Example #1 was followed, except that the bath also contained 0.1 grams/liter of anisaldehyde and 0.1 grams/liter of polyvinyl alcohol with equivalent results being obtained.
• An aqueous alkaline electroplating bath comprising inc oxide, alkali metal hydroxide, polyethyleneimine having a molecular weight of from 1,000 to 400,000 and being present in a concentration of 0.2 to grams per liter and a zinc brightening amount of a nitrogen heterocyclic compound of the formula:
• A is independently selected from the group consisting of 11 is 0 or 1; when n is 0, nitrogen is doubly bonded to carbon in A; with the proviso that when n is O, A is R and R are independently selected from the group consisting of hydrogen, alkyl of 1 to 4 carbons, phenyl; and may be joined to form a six membered aromatic carbocyclic ring which may be substituted and R is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl.
• a method of depositing bright zinc from a zincate electroplating bath comprising electrolyzing the bath of Claim 1 for a period of time suflicient to form a bright zinc deposit onto a cathodic surface.
• a cyanide free alkaline zincate electroplating bath comprising zinc oxide, alkali metal hydroxide, polyethyleneimine having a molecular weight of from 1,000 to 400,000 and being present in a concentration from 0.2 to 100 grams per liter and a zinc brightening amount of a nitrogen heterocyclic compound of the formula:
• X is S- or l lR and A is independently selected from the group consisting of n is O or 1; when n is 0, nitrogen is doubly bonded to carbon in A; with the proviso that when n is 0, A is R and R are independently selected from the group consisting of hydrogen, alkyl of 1 to 4 carbon atoms, phenyl; and may be joined to form a six membered aromatic carbocyclic ring which may be substituted and R is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl.

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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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Publications (1)

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Cited By (4)

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• 1973
  • 1973-02-20 US US00333927A patent/US3841982A/en not_active Expired - Lifetime
  • 1973-03-27 NL NL7304246A patent/NL7304246A/xx unknown
  • 1973-03-29 FR FR7311420A patent/FR2180708B1/fr not_active Expired
  • 1973-04-14 DE DE2318984A patent/DE2318984C2/de not_active Expired
  • 1973-04-16 CA CA169,009A patent/CA1009178A/en not_active Expired
  • 1973-04-16 IT IT49467/73A patent/IT983031B/it active
  • 1973-04-16 GB GB1826373A patent/GB1387529A/en not_active Expired
  • 1973-04-17 JP JP48042757A patent/JPS4917324A/ja active Pending
  • 1973-04-17 AR AR247599A patent/AR197894A1/es active

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