Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D209/00—Heterocyclic compounds containing five-membered rings, condensed with other rings, with one nitrogen atom as the only ring hetero atom
  • C07D209/56—Ring systems containing three or more rings
  • C07D209/80—[b, c]- or [b, d]-condensed
  • C07D209/82—Carbazoles; Hydrogenated carbazoles
  • C07D209/86—Carbazoles; Hydrogenated carbazoles with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to carbon atoms of the ring system

Definitions

• Chromium is one of the more difiicult metals to electrodeposit satisfactorily. Chromium is conventionally electrodeposited from a hot aqueous electroplating bath contaming chromic and sulfuric acid. Such a bath is both corrosive and very oxidizing at the temperatures at which it is usually employed. Many metals, when immersed in such an acid solution, are corroded or etched to produce a rough, uneven surface, poorly suited as an undercoat for a bright electrodeposit of chromium.
• a bright, adherent, corrosion resistant coating of chromium may be electrodeposited over an article having 'an outer surface of antimony or of an antimony base alloy if, instead of immediately applying the plating current when the article to be plated is immersed in the chromium plating bath, the application of th plating current is delayed for a predetermined time.
• the practice of my invention involves exposing an article, having an outer surface of antimony or an antimony base alloy, upon which chromium is to be electrodeposited, to a chromium plating bath for a period of time not exceeding sixty seconds before any plating current is applied to the bath and then electrodepositing chromium on the article by passing a plating current through the bath.
• the article is immersed in a hot chromium plating bath and the delay in the application of the plating current is from about five to thirty seconds.
• any suitable chromic acid chromium plating bath may be used.
• the bath may contain, for example, from about 33 to 53 ounces per gallon of chromic acid (CrOs) and a small amount of sulfuric acid.
• CrOs chromic acid
• the ratio of chromic acid to sulfuric acid may of course be varied.
• an aqueous chromium plating bath containing 53 ounces per gallon of chromic acid (OrOs) and 0.53 ounces per gallon of surfuric acid may be used.
• Such a plating bath may be operated at temperatures ranging from F.
• the article to be plated may be exposed separately to a first hot chromium plating bath through which no plating current is passed and then chromium plated using a second :chromium plating bath where the full plating current is applied when the article is immersed in the bath.
• the method of my invention is readily adaptable for use in commercial electroplating procedures which employ a continuous conveyor system.
• an article to be chromium plated may be moved by an automatic conveyor system through the entire cleaning, treating and plating sequence.
• a bright antimony or antimony alloy surface may also be obtained without the necessity of bufling or polishing.
• the article is immersed in a chromic acid chromium plating bath having a temperature of about 115 F. to 130 F. and maintained there for about seconds before any plating current is applied to the bath.
• the full current preferably a current sufhcient to provide a cathodic current density of about 180' to 220 amperes per square foot is applied.
• the article is then maintained in the chromium plating bath for a length of time suflicient to plate th desired thickness of chromium which, in a preferred embodiment, does not exceed about 0.000015 inch.
• a method of electrodepositing a bright coating of chromium on an article having an outer surface of a metal selected from the class consisting of antimony and antimony base alloys which comprises immersing said article for a period of time not in excess of one minute in a chromic acid base chromium plating bath maintained at a temperature of from 115 F. to 130 F. while no electrical current is passing through the bath and then electrodepositing bright chromium on the article in a chromic acid base chromium plating bath.
• a method of electrod'epositing a bright coating of chromium on an article having an outer surface of antimony which comprises immersing said article for a period of time not in excess'of one minute in achromic acid base chromium plating bath maintained at a temperature of from 110 F. to 160 F. while no electrical current is passing through the bath and then electrodepositing bright chromium on the antimony in a chromic acid base chromium plating bath, said bright chromium electrodeposit having a thickness not in excess of 0.0001 inch.
• a method of electrodepositing a bright coating of chromium on an article having an outer surface of antimony which comprises immersing said article for a period of time within the range of 5 to 30 seconds in a chromic acid base chromium plating bath containing about 33 to 53 ounces of chromic acid per gallon while no electrical current is passing through the bath, said bath being maintained at a temperature of from F. to about F. and then electrodepositing bright chromium on the antimony in a chromium plating bath containing about 33 to 53 ounces of chromic acid per gallon, said bright chromium having a thickness within the range of 0.00001 to 0.000015 inch.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electroplating Methods And Accessories (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23204658

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (1)

Citations (2)

• 1952
  • 1952-09-22 US US310929A patent/US2764538A/en not_active Expired - Lifetime
• 1953
  • 1953-09-03 GB GB24349/53A patent/GB738236A/en not_active Expired
  • 1953-09-17 FR FR1083800D patent/FR1083800A/fr not_active Expired
  • 1953-09-22 DE DEG12673A patent/DE929103C/de not_active Expired

Patent Citations (2)

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