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
  • C25D3/30—Electroplating: Baths therefor from solutions of tin
• • 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

Definitions

• the present invention relates to a method of electrodeposition at high current densities of between 100 and 400 A / dm 2 , preferably between 200 and 300 A / dm 2 , in an electrolysis, tin and / or of tin alloys, in particular of Sn-Pb, Sn-Co, Sn-Ni alloys, on a metallic support, such as a steel strip, according to which an electrolysis bath is used containing at least a metal halide, to be deposited on the metal support, such as chloride, bromide, iodide, and stannous and stannic ions.
• the method according to the invention is characterized in that an electrolysis bath is used, the metal ion content of which is maintained between 60 and 150 g / l and is preferably of the order of 115 to 125 g / I for tinning, and of the order of 135 to 145 g / I for the deposition of tin alloys and in that the electrolyte is circulated with respect to the steel strip at a speed between 2 and 9 m / sec and preferably between 3 and 6 m / sec.
• the aforementioned support is formed from a steel strip
• the latter acts as a cathode which is displaced opposite an insoluble anode at a distance of between 0.75 and 1.5 cm while the electrolyte is circulated between this cathode and the anode in the form of a substantially turbulent flow.
• the electrolysis bath is regenerated by bringing the latter into contact with granules of the metal to be deposited, so as to thus constantly maintain a bath sufficiently rich in metal ions to deposit on the aforementioned support.
• the method according to the invention consists in carrying out an electrolytic deposition of tin and / or tin alloys, preferably Sn-Pb, Sn-Co or Sn-Ni alloys on a support.
• tin and / or tin alloys preferably Sn-Pb, Sn-Co or Sn-Ni alloys
• metallic and in particular on one or two sides of a steel strip which moves in an electrolysis bath opposite an insoluble anode and which preferably acts as a cathode while the electrolyte is circulated between this cathode and the anode at a sufficiently high speed to obtain a substantially turbulent flow.
• This speed is generally between 1 and 9 m / sec and preferably between 3 and 6 m / sec, an ideal speed being of the order of 5 m / sec.
• the high current density implies relatively high concentrations of metal cations.
• an electrolytic bath the metal ion content of which is maintained between 60 and 150 g / l, preferably of the order of 115 to 125 g / l for l tinning, and of the order of 135 to 145 g / I for the deposit of tin alloys.
• the content of the metal or other metals of this alloy is generally maintained between 10 and 80 g / l.
• the lead content of the electrolysis bath is advantageously maintained between 20 and 30 g / I, and is preferably of the order of 25 g / I.
• the cobalt content of the electrolysis bath is advantageously between 45 and 55 g / I and is preferably of the order of 50 g / I.
• the ratio R 1 Sn 4+ / (Sn 4+ + Sn 2+ ) in the electrolysis bath is advantageously maintained between 0.1 and 0.95.
• the pH of the electrolysis bath to avoid hydrolysis of metal ions, the pH is advantageously maintained between -0.2 and 0.3 and is preferably of the order of 0.
• the temperature of the electrolysis bath is advantageously maintained between 30 and 50 ° C and is preferably of the order of 40 ° C.
• bromide is preferably used which makes it possible to avoid the release of harmful gases into the atmosphere.
• reaction 1 For a halide mixture of molarity advantageously between 3M and 5M and for a current density between 50 and 400 A / dm 2 , the yield of reaction 1 is 100
• the concentration of halide Y- in the bath is preferably of the order of 4M.
• the ratio R2 Br / (Br + 1 + CI) is advantageously between 0 and 1.
• This ratio is preferably of the order of 0 if it is desired to avoid any risk of release of chlorine and precipitation of stannous iodide.
• the anodic potential of this electrode when polarized in the tinning cell, should preferably be maintained between 1.5 and 2.5 volts relative to the normal hydrogen electrode (ENH) and is preferably of the order of 2 volts.
• the invention also relates to a particular process for regenerating a tin plating bath and tin alloys, in particular Sn-Pb, Sn-Co and Sn-Ni alloys, rich in stannic ions by the bringing the electrolysis bath in which this electrodeposition takes place into contact with tin, lead, cobalt and nickel granules of moderate specific surfaces.
• the regeneration reaction is carried out in a regeneration reactor known per se according to the following reaction scheme:
• the tinning bath is therefore a mixture of Sn4 + and Sn2 + ions, i.e. a mixture of the regeneration reagent Sn4 + and the regeneration product Sn2 +.
• the main reactions in the tinning cell are: at the anode at the cathode Z 1 represents the fraction of the cathodic current used to reduce stannous tin to metallic tin and Z 2 the fraction of cathodic current used to reduce stannous tin to stannic tin.
• reaction 6 + reaction 7 or reaction 6 + reaction 7 + reaction 8 The overall cathodic reaction (reaction 6 + reaction 7 or reaction 6 + reaction 7 + reaction 8) added to the anode reaction (reaction 5) perfectly balances the regeneration reaction (reaction 4a or reaction 4a + reaction 4b), which allows the system consisting of the tinning cell and the regeneration reactor to operate without the addition of external reagents other than tin, nickel, cobalt and lead, all in metallic form.
• the concentration in the electrolyte of metal ions Sn4 + + Sn2 + + X2 + is advantageously maintained between 60 and 150 g / I and is preferably of the order of 120 g / I for tinning. and 140 g / l for depositing alloys.
• the electrolyte was prepared by the action of hydrobromic acid at 47% P.A. and hydrogen peroxide at 30% P.A. on granules of pure metallic tin.
• the Br2 electrogeneration yield at 300 A / dm 2 and 40 ° C was 100% on the Ti / Ru0 2 anode.
• the conductivity of the electrolytic bath was of the order of 0.4 S / cm and the voltage U A / C across the terminals of the cell was of the order of 10 volts.
• the specific energy consumption was around 9 KWhr / kg.
• the regeneration speed was of the order of 27.5 A / dm 2 at 40 ° C and 55 A / dm 2 at 60 ° C (respectively 600 and 1200 mg / cm 2 .hr.).
• the volume of the regeneration reactor was 200 1 to 40 ° C and 110 1 to 60 ° C for an hourly consumption of tin of the order from 220 kg.
• the electrolytes were prepared by dissolving metal halides to be deposited in an Sn4 + / Sn2 + electrolyte prepared as in Example 1.
• the regeneration reaction was carried out by the action of the electrolyte thus prepared on granules of tin, lead, nickel and cobalt.
• bromide Br-, chloride CI- and iodide I-ions allow the easy solubilization in acid medium of the cations Sn2 +, Sn4 +, Co2 +, Ni2 + and Pb2 +.
• amphoterization reaction between stannic tin and metallic tin in the form of granules makes it possible to regenerate the bath at moderate temperature and specific surface of liquid / solid contact.
• this regeneration scheme makes it possible to couple the electrodeposition unit with a regeneration unit of moderate size.
• insoluble Ti / Ru02 or Ti / lr0 2 anodes minimizes the release of oxygen.
• the process according to the invention relates, on the one hand, to a process for the electrodeposition of tin or a tin alloy on a metal support with high current density by making use of an anode. insoluble in an electrolysis bath containing as metal salt essentially bromide of the metal to be deposited and preferably only bromide, and, on the other hand, a process for the regeneration of an electrolysis bath containing a metal halide or metals to be deposited, these halides can be chlorides, bromides, and iodides.

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Citations (4)

• 1992
  • 1992-04-15 BE BE9200346A patent/BE1005730A4/fr not_active IP Right Cessation
• 1993
  • 1993-03-08 DE DE69314990T patent/DE69314990T2/de not_active Expired - Fee Related
  • 1993-03-08 AT AT93200646T patent/ATE159991T1/de active
  • 1993-03-08 EP EP93200646A patent/EP0570033B1/de not_active Expired - Lifetime

Patent Citations (4)

Non-Patent Citations (2)

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