Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/0053—Details of the reactor
• • 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
  • C25D3/60—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of tin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00182—Controlling or regulating processes controlling the level of reactants in the reactor vessel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00186—Controlling or regulating processes controlling the composition of the reactive mixture

Definitions

• the novel process of this invention for electroplating a tin-bismuth alloy plate may comprise immersing an article to be plated in an aqueous plating bath containing alkali metal stannate, free alkali metal hydroxide, and an alkali metal bismuthate; and electrodepositing a. tin-bismuth alloy onto said article as cathode in said bath.
• This invention relates to a novel technique for electroplating. More specifically it relates to a process for plating tin-bismuth alloys.
• metallic tin may be electrodeposited onto the surface of various basis metals including steel, brass, bronze, copper, etc.
• products bearing an electrodeposit of tin may find use because of the superior properties arising from the excellent resistance of tin to oxidation and/ or the ability of tin to serve as a lubricant as, e.g., on threads.
• Products which have been plated with tin have been found to be satisfactory under normal conditions of use and/or storage; and when maintained under satisfactory, ambient conditions, including temperature typically above 18 C., the electrodeposited tin may retain its superior properties, including lubricity, for indefinitely long periods of time.
• tin pest on tin may be recognized firstly by the development of a dull lustre on a formerly shiny surface. Furthermore, especially after extended periods of time at temperatures below 18 C., tin pest, as formed in and on an electrodedeposit of tin is observed as a fine nonadherent powder, and spots on the surface may have a corroded appearance. This loose tin powder, during its formation, separates from the surface of the basis metal and thereby loses its ability to protect that basis metal. As the tin pest continues to develop, the apparently loose, fine powder may form flakes which, in due course, may drop off from the basis metal thereby exposing the basis metal to corrosion and simultaneously removing therefrom the bulk of the tin plate. When this happens, the part becomes less attractive in appearance, loses its lubricity, and becomes much less able to withstand the effect of corrosion both before and after use.
• the novel process of this invention for electrodepositing a tin-bismuth alloy plate may comprise immersing an article to 3,522,155 Patented July 28, 1970 be plated in an aqueous plating bath containing alkali metal stannate, free alkali metal hydroxide, and and alkali metal bismuthate; and electrodepositing a tin-bismuth alloy onto said article as cathode in said bath.
• the basis metal which may be plated in practice of this invention may be any suitable metal on which it is desired to produce an electrodeposited tin-containing plate.
• Typical basis metals which may be plated in accordance with the process of this invention may include steel, iron, brass, bronze, copper, etc. This invention may find particular use when used to electrodeposit a tincontaining plate onto the threads of, e.g., pipes or couplings, or when used to electrodeposit a tin-containing plate on the surface of, e.g., copper wire.
• the preferred basis metal with which the process of this invention may find use may be mild steel.
• the aqueous plating baths used in the process of this invention may contain alkali metal stannate, e.g., sodium stannate or preferably potassium stannate.
• alkali metal stannate e.g., sodium stannate or preferably potassium stannate.
• the aqueous plating baths may contain alkali metal stannate in amount (expressed as grams per liter of tin contained therein) of 10-300 g./l., preferably 50-200 g./ 1., most preferably 150 g./l. Typically this may be attained when using the preferred potassium stannate by use of a bath containing about 375 g./l. of potassium stannate.
• the aqueous baths may also contain free alkali metal hydroxide, typically potassium hydroxide or sodium hydroxide, most preferably potassium hydroxide.
• the bath It will be apparent that, when the aqueous bath is formed from and contains potassium stannate, the alkali metal hydroxide will preferably be potassium hydroxide; and that when the aqueous bath is formed from and con tains sodium stannate, the alkali metal hydroxide Will preferably be sodium hydroxide.
• novel aqueous baths of this invention contain an alkali metal bismuthate, preferably sodium bismuthate, potassium bismuthate, etc.
• alkali metal bismuthate preferably sodium bismuthate, potassium bismuthate, etc.
• Sodium bismuthate may be the most readily available alkali metal bismuthate and may be preferred.
• bismuth metal may be added to the aqueous electroplating bath (in the form of alkali metal bismuthate) in amount of 005-1 g./l., preferably 0.20.75 g./l., say 0.6 g./l.
• baths of this invention may contain the following components in solution:
• this may correspond to:
• the soluble anode may typically be tin, preferably commercial tin metal, or a high-speed tin alloy which may contain minor amounts of metals such as aluminum.
• Electrodeposition of tin plate onto the cathode in such a system may preferably be effected at temperature of 60 C. to the boiling point, e.g. 105 C., and preferably at about 95 C. Electroplating may be effected using a cathode current density of about 1 a.s.d. to 40 a.s.d., preferably 8 a.s.d.
• Elimination of the danger of tin pest from the electrodeposits formed in accordance with this invention may be effected by formation of an electrodeposited tin plate containing 0.l%0.6%, say 0.2%, by Weight of bismuth in the tin deposit. It is found that formation of the electrodeposited tin-bismuth alloy having a bismuth content within this range permits attainment of a desirable product characterized by a minimum occurrence of tin pest.
• Electrodeposits containing bismuth in the desired range in the tin deposit may be effected by maintaining the article to be plated as cathode for l-60 minutes, preferably 20 minutes. During this period of time, using the baths of this invention, it is readily possible to produce electrodeposits containing bismuth in the desired range in the tin deposit.
• the bismuth and tin content of the bath may preferably be maintained at the desired level, which typically is one wherein the concentration of bismuth in the bath may be 501000, say 600 milligrams per liter which yields a ratio of bismuth to tin (each expressed as metal) of 0.00l-0.006, preferably 0.002 in the plate. It will be noted that these ratios of bismuth to tin in the bath may yield deposits containing bismuth and tin wherein the bismuth may be present in amount of 0.1%- O.6%, typically 0.2%.
• tin When the system is used with an insoluble anode, tin will also be depleted from the bath, and the tin depleted may be replenished by addition to the bath of appropriate amounts of alkali metal stannate typically in amount of 1.107 grams of tin per ampere hour. Maintenance of the level of bismuth in insoluble anode systems may be effected by addition of the alkali metal bismuthate in the same manner as noted for the soluble anode systems.
• both the tin content and the bismuth content may be replenished-by adding to the bath a maintenance composition containing alkali metal stannate and alkali metal bismuthate.
• these two components may be present in a ratio equivalent to the bismuth: tin ratio of the desired electrodeposit.
• these maintenance compositions may have a bismuth: tin ratio of 0.00l0.006:1 and preferably 0.00211.
• the use of these novel maintenance compositions may permit attainment of uniform tin-bismuth alloy plate during operation without the necessity of adjusting additions of the two separate components.
• These novel maintenance compositions are also highly convenient for the initial make-up of the plating bath.
• this invention may include a make-up and maintenance composition which comprises 10300 parts, preferably 50-200 parts,
• tin metal added as alkali metal stannate
• bismuth metal added as alkali metal bismuthate
• This composition may be employed for make-up of a bath preferably when the bath contains a soluble anode. The tin loss from the bath is minimal when soluble anodes are used.
• the makeup and maintenance composition may also be used in connection with a bath containing insoluble anodes.
• EXAMPLE 1 A 3-liter tin-bismuth alloy plating bath was made up to contain 0.75 g./l. sodium bismuthate (0.6 g./1. Bi), 22.5 g./l. KOH and 150 g./l. tin metal added as potassium stannate. The bath was maintained at 88 C. and steel panels were plated at a cathode current density of 6.45 amperes per square decimeter using steel anodes for a period of about one hour, after which a deposit having a thickness of 0.05 mm. of tin-bismuth alloy was obtained. The deposit had a bismuth content of 0.12-0.20%.
• the plated panels Were inoculated with grey tin by placing a small amount of powdered grey tin (tin pest) on the surface thereof and stored at a temperature between 15 and 18 C. for six weeks. At the end of this time no grey tin (tin pest) developed on the deposit. Tin plated panels plated from identical baths which did not contain sodium bismuthate developed grey tin in objectionable quantities in only 24 hours storage under the same conditions.
• the method of electrodepositing a tin-bismuth alloy plate comprising immersing an article to be plated in an aqueous plating bath containing alkali metal stannate, free alkali metal hydroxide, and alkali metal bismuthate; and electrodepositing a tin-bismuth alloy plate onto said article as cathode in said bath.
• the method of electrodepositing a tin-bismuth alloy plate comprising immersing an article to be plated in an aqueous plating bath containing potassium stannate, free potassium hydroxide, and 0.05-1 g./l. of bismuth metal as sodium bismuthate; and electrodepositing a tinbismuth alloy plate onto said article as cathode in said bath.
• a novel bath for the electrodeposition of a tin-bismuth alloy plate which comprises an aqueous plating bath containing alkali metal stannate, free alkali metal hydroxide, and alkali metal bismuthate.
• a novel bath for the electrodeposition of a tinbismuth alloy plate which comprises an aqueous plating bath containing potassium stannate, free potassium hydroxide, and 0.05-1.0 gram per liter of sodium bismuthate expressed as bismuth metal.
• a novel maintenance composition for aqueous tin-bismuth alloy electroplating baths which consists essentially of alkali metal bismuthate and alkali metal stannate.
• a novel maintenance composition for aqueous tinbismuth alloy electroplating baths which consists essentially of 10-300 parts of tin metal as alkali metal UNITED STATES PATENTS 2,318,592 5/1943 Cupery 20449 2,424,472 7/1947 Lowenheim et al. 20454 FOREIGN PATENTS 526,037 9/1940 Great Britain. 126,343 5/ 1961 Russia.

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

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Cited By (8)

Citations (3)

• 0
  • GB GB1051927D patent/GB1051927A/en active Active
• 1964
  • 1964-07-10 US US381895A patent/US3522155A/en not_active Expired - Lifetime
• 1965
  • 1965-07-07 SE SE8987/65A patent/SE306863B/xx unknown
  • 1965-07-09 ES ES0315147A patent/ES315147A1/es not_active Expired
  • 1965-07-09 DE DE1496913A patent/DE1496913C3/de not_active Expired
  • 1965-07-09 NL NL656508910A patent/NL151448B/xx not_active IP Right Cessation

Patent Citations (3)

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