EP1207219A1 - Equipement et procédé pour couvrir un element métallique avec une couche de cuivre - Google Patents

Equipement et procédé pour couvrir un element métallique avec une couche de cuivre Download PDF

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Publication number
EP1207219A1
EP1207219A1 EP00830763A EP00830763A EP1207219A1 EP 1207219 A1 EP1207219 A1 EP 1207219A1 EP 00830763 A EP00830763 A EP 00830763A EP 00830763 A EP00830763 A EP 00830763A EP 1207219 A1 EP1207219 A1 EP 1207219A1
Authority
EP
European Patent Office
Prior art keywords
copper
tank
cathode
dissolving tank
anode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00830763A
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German (de)
English (en)
Inventor
Pietro Cavallotti
Federico Pavan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pirelli and C SpA
Pirelli Tyre SpA
Original Assignee
Pirelli Pneumatici SpA
Pirelli SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Pirelli Pneumatici SpA, Pirelli SpA filed Critical Pirelli Pneumatici SpA
Priority to EP00830763A priority Critical patent/EP1207219A1/fr
Publication of EP1207219A1 publication Critical patent/EP1207219A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/12—Process control or regulation
    • C25D21/14—Controlled addition of electrolyte components
    • 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
    • C25D3/38—Electroplating: Baths therefor from solutions of copper
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/06—Wires; Strips; Foils
    • C25D7/0607—Wires

Definitions

  • the present invention relates to an equipment and a method for covering a metallic element with a layer of copper.
  • the present invention relates to the electrolytic deposition of a layer of metallic copper on a metallic element.
  • said metal structure is made of steel wires, with a carbon content between 0.6% and 0.95%, either individual or grouped in steel cords.
  • steel which is the material of choice on account of its mechanical properties, has the disadvantage that it does not adhere sufficiently to the vulcanized elastomeric material.
  • a suitable material for example brass.
  • brass indicates a metallic composition, as homogeneous as possible, comprising from 10 to 50 wt.% of zinc and from 90 to 50 wt.% of copper, preferably from 20 to 40 wt.% of zinc and from 80 to 60 wt.% of copper and, even-more preferably, from 30 to 40 wt.% of zinc and from 70 to 60 wt.% of copper.
  • cord indicates a cord obtained by rope-making, according to traditional techniques, from drawn steel wires covered with a layer of brass which, before drawing, is from 1 to 3 ⁇ m thick, whereas after drawing it is from 0.1 to 0.4 ⁇ m thick.
  • the diameter of said wires is of about 1.3 mm before drawing and 0.1-0.5 mm after drawing.
  • a cord commonly used in reinforcing structures for giant tyres consists of 7 strands, each of 4 wires with a diameter of about 0.175 mm, around which a wire is wound, the so-called filament, with a diameter of 0.15 mm.
  • the currently most-used technique envisages the electrodeposition, on a steel wire, of a layer of copper and a layer of zinc in two separate stages, followed by a third stage of thermal diffusion carried out at a temperature above 450°C, preferably at a temperature from 450 to 500°C. During this stage, the aforesaid layers diffuse into one another forming a layer of brass that has excellent characteristics of drawability and adhesiveness.
  • the electrolytic cells used for depositing a layer of copper on steel wire were equipped with soluble anodes of copper.
  • the steel wire was given a negative charge so that it acted as cathode and was made to pass through an electrolyte containing copper ions, preferably in the form of copper pyrophosphate.
  • the copper ions were deposited on the wire, covering it with the desired layer.
  • the copper anodes dissolved and supplied the electrolyte with more copper ions. Therefore the shape of the anodes changed as the copper dissolved and this led to variations in current density at the steel cathode with corresponding non-uniformity of the copper layer deposited on the steel wire. This non-uniformity could only be contained by frequent replacement of the anodes, but in their turn these replacements were the cause of undesirable interruptions of the process and reduced its productivity.
  • the patent US-A-5 516 414 describes a method and an equipment in which the concentration of copper ions is restored by supplying cupric hydroxide to the electrolytic solution of pyrophosphates.
  • the diaphragm method is described, for example, in the patent EP-B-0 508 212 and comprises the following stages:
  • the dissolving tank is divided into two sections by a diaphragm consisting of a conductive porous membrane in which the pore size is smaller than that of the Cu 2+ ions but larger than that of KOH, H 2 O and OH - ions.
  • a diaphragm consisting of a conductive porous membrane in which the pore size is smaller than that of the Cu 2+ ions but larger than that of KOH, H 2 O and OH - ions.
  • the first section there is a copper anode
  • an insoluble cathode dissolves and the Cu 2+ ions move towards the cathode but cannot reach it because they are held back by the membrane.
  • the concentration of Cu 2+ ions therefore increases in the first section.
  • the electric charges (e - ) split the water into gaseous H 2 and OH - ions.
  • the OH - ions pass through the membrane into the first section.
  • the KOH and the H 2 O that are consumed by each electrode are replaced via the membrane by a process of reverse osmosis.
  • a first drawback of the aforementioned method is that, to effect the desired selectivity with respect to the species present in the solutions of the two sections of the dissolving tank, the size of the pores of the aforesaid conductive membrane (NafionTM, column 7, lines 37-58) must be accurately calibrated. It is therefore very expensive.
  • a second drawback is that the aforesaid method requires the use of an equipment provided with several groups of pumps and pipe (EP-B-0 508 212, see the numerical references 22, 29, 31 and 34 in Fig. 1) involving complex management and programming for successfully keeping the compositions and the pH of the solutions in the two electrolytic cells within the desired values.
  • a third drawback arises from the fact that proper operation of the whole plant is dependent on the ability of the aforementioned conductive membrane to remain efficient over time, maintaining the aforesaid high degree of selectivity.
  • the second method that makes use of a deposition tank and a dissolving tank is the so-called oxygen method.
  • This method is described, for example, in an article by M.Kikuchi et al. (Proceedings of the 66th Annual Conference of the Wire Association International 1996; Charlotte, NC, USA, pages 30-35).
  • the dissolving tank consists of a pressure reactor containing copper plates, an electrolyte, pressurized gaseous oxygen and an injector.
  • the method envisages constant monitoring of the pH of the electrolyte in the dissolving tank because its value is indicative of the concentration of Cu 2+ .
  • the system commands the injector to supply gaseous oxygen and thus to increase the amount of oxygen dissolved in the electrolyte and this, in its turn, promotes the dissolution of the copper according to the following reaction scheme: Cu + 1 ⁇ 2 O 2 + H 2 O ⁇ Cu 2+ + 2OH -
  • the Cu 2+ concentration can thus be maintained within predetermined limits by adjusting the pressure of the gaseous oxygen.
  • the pressure required by the system is of about 1 kg/cm 2 .
  • the pressure required by the system is of about 1 kg/cm 2 .
  • the inventors realized that it is not necessary to use a conductive membrane possessing the high degree of selectivity indicated above but it can be advantageous to use a porous diaphragm that is scarcely permeable to copper ions provided that:
  • a first aspect of the present invention relates to an equipment for covering a metallic element with a layer of copper, said equipment including an electrodeposition tank and a dissolving tank, in which
  • the aqueous solution of the electrodeposition tank is obtained from copper pyrophosphate and potassium pyrophosphate.
  • the quantity of copper pyrophosphate in said solution is between 80 and 120 g/l. Even more preferably it is equal to about 100 g/l.
  • the quantity of potassium pyrophosphate trihydrate in said solution is preferably between 350 and 450 g/l and, even more preferably, it is equal to about 400 g/l.
  • Said insoluble anode of said electrodeposition tank consists advantageously of any metallic compound that does not oxidize in the operating conditions of the electrodeposition tank.
  • it can consist of titanium coated with oxides of noble metals such as iridium, tantalum and the like; or it can consist of platinized titanium.
  • said anode When the metallic element is a steel wire, said anode preferably has an elongated shape and is positioned parallel to the steel wire to ensure good current distribution.
  • the solution sent from the electrodeposition tank to the said first section of the said dissolving tank has, on average, the following characteristics: copper pyrophosphate trihydrate 98.00-99.9 g/l potassium pyrophosphate 400 g/l temperature 50°C pH 8.4-8.7
  • This cycle is repeated continuously for the whole duration of the process.
  • the insoluble anode is preferably in the shape of a basket. Typically, it is a basket of titanium or of any other metallic compound that does not oxidize in the operating conditions of said first section of said dissolving tank.
  • the current density of said anode varies with variation of the quantity and shape of the small pieces of copper that it contains.
  • it is maintained within the range from 1 to 5 A/dm 2 .
  • the solution (catholyte) contained in said second section of said dissolving tank has, on average, the following characteristics: copper pyrophosphate trihydrate 0.0-5 g/l potassium pyrophosphate 400 g/l temperature 50°C pH 8.7-9.2
  • the insoluble cathode immersed in this solution is, advantageously, formed of wires or strips of platinum or of some other material possessing a hydrogen overpotential which, in 2N sulphuric acid and at current density of 10E-3 A/dm 2 , is preferably between 0.3 and 0.001 V and, even more preferably, between 0.05 and 0.02 V. Typically, in these conditions, platinum has a hydrogen overpotential of 0.024 V.
  • the total area of said cathode is such that the cathode current density is equal to at least 100 A/dm 2 .
  • the porous diaphragm interposed between said first and second sections of said dissolving tank can consist of a vitreous, ceramic or polymeric material, for example a polyester.
  • the dissolving tank will contain one or more first and second sections separated by respective interposed elements possessing the aforesaid characteristics and properties.
  • the water lost by evaporation and in the reaction of reduction is replaced continuously by supplying fresh water to the electrodeposition tank via a suitable pipe (not shown).
  • an aqueous potassium pyrophosphate solution or even a solution possessing the same composition as that of deposition tank 1 is placed in section 8.
  • the quantity of copper in the catholyte solution 12 decreases until it reaches, in normal operation, a level ⁇ 5 g/l.
  • a second aspect of the present invention relates to a method for covering a metallic element with a layer of metallic copper, in which
  • the equipment includes an electrodeposition tank 1 and a dissolving tank 2.
  • Tank 1 contains an aqueous solution 3 of (i) copper ions in the form of a copper salt of an acid and of (ii) at least one basic compound suitable for adjusting the pH of the solution 3.
  • Insoluble anodes 4 and a cathode consisting of a steel wire 5 are immersed in said solution 3. Deposition of metallic copper on said steel wire 5 tends to lower the concentration of copper ions in the solution 3, while the evolution of oxygen at the anodes 4 tends to lower the pH of said solution.
  • the insoluble anodes 4 and the cathode 5 are connected electrically to a first source of direct current (not shown).
  • Tank 2 is divided into sections (7, 8) by a porous diaphragm 6.
  • the first section 7 contains an anolyte 9 consisting of the electrolytic solution obtained from the electrodeposition tank 1.
  • An insoluble anode 10 in the shape of a basket containing granules 11 of metallic copper is immersed in said anolyte 9.
  • the second section 8 contains a catholyte 12 consisting of components of said electrolysis solution 3 being able of passing through said porous glass diaphragm 6 that has a permeability to copper ions of about 1%/hour.
  • a cathode 13 is immersed in said catholyte 12. Said cathode 13 and anode 10 are connected electrically to a second source of direct current (not shown).
  • Said tanks 1 and 2 are connected by a pipe 15 for sending the electrolyte 3 to the first section 7 of tank 2.
  • said tanks 1 and 2 are also connected together by a pipe 14 for feeding the anolyte 9 and the catholyte 12 from tank 2 to tank 1.
  • the anolyte 9 and the catholyte 12 are fed from tank 2 to tank 1 via two separate pipes 14 and 16 respectively.
  • Circulation in lines 14, 15, 16 and 17 is provided by pumps (not shown).
  • a steel wire 5 with diameter of 1.6 mm had previously been pickled electrolytically in sulphuric acid and was then covered with a layer of copper in an equipment like that shown in Fig. 1.
  • the test lasted 160 hours.
  • the wire 5 travelled at a speed of 1920 m/hour.
  • the solution 3 in tank 1 had the following initial characteristics: copper pyrophosphate trihydrate 100 g/l potassium pyrophosphate 400 g/l temperature 50°C pH 8.7 whereas, at outlet, it had the following characteristics: copper pyrophosphate trihydrate 99.62 g/l potassium pyrophosphate 400 g/l temperature 50°C pH 8.6
  • the current supplied was 35 A and the corresponding cathode current density at the wire 5 was 10 A/dm 2 .
  • Pellets of electrolytic copper with diameter of about 2.5 cm were placed in the anode basket 10 and a current of 35 A was supplied.
  • the surface area of this anode varies over time with variation of the quantity of copper present in the basket and of the diameter of the pellets as they dissolve.
  • the total surface area of the cathodes 13 was 0.25 dm 2 and the cathode current density was therefore 140 A/dm 2 .
  • the solution 3 leaving the electrodeposition tank 1 passed to the first section 7 of the dissolving tank 2 and from there it passed to section 8 through porous diaphragms 6 of glass grade 4 ISO 4793 produced by the company Schott Mainz that had a permeability to copper ions of only about 1%/hour.
  • Anolyte copper pyrophosphate trihydrate 111.4 g/l potassium pyrophosphate 400 g/l temperature 50°C pH 8.7
  • Catholyte copper pyrophosphate trihydrate 1 g/l potassium pyrophosphate 4 g/l temperature 50°C pH 8.9

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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)
  • Automation & Control Theory (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Electrolytic Production Of Metals (AREA)
EP00830763A 2000-11-20 2000-11-20 Equipement et procédé pour couvrir un element métallique avec une couche de cuivre Withdrawn EP1207219A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP00830763A EP1207219A1 (fr) 2000-11-20 2000-11-20 Equipement et procédé pour couvrir un element métallique avec une couche de cuivre

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EP00830763A EP1207219A1 (fr) 2000-11-20 2000-11-20 Equipement et procédé pour couvrir un element métallique avec une couche de cuivre

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EP1207219A1 true EP1207219A1 (fr) 2002-05-22

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0508212A1 (fr) * 1991-04-08 1992-10-14 The Goodyear Tire & Rubber Company Procédé pour appliquer une couche de cuivre sur un fil d'acier
EP0550002A1 (fr) * 1991-12-26 1993-07-07 Nkk Corporation Procédé d'étamage électrolytique
US5516414A (en) * 1992-09-15 1996-05-14 Atr Wire & Cable Co., Inc. Method and apparatus for electrolytically plating copper
US5804053A (en) * 1995-12-07 1998-09-08 Eltech Systems Corporation Continuously electroplated foam of improved weight distribution
EP0915190A2 (fr) * 1997-10-30 1999-05-12 Daiki Engineering Co., Ltd. Procédé et appareil pour l'alimentation des ions métalliques à un bain pour l'électroplacage des alliages

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0508212A1 (fr) * 1991-04-08 1992-10-14 The Goodyear Tire & Rubber Company Procédé pour appliquer une couche de cuivre sur un fil d'acier
EP0550002A1 (fr) * 1991-12-26 1993-07-07 Nkk Corporation Procédé d'étamage électrolytique
US5516414A (en) * 1992-09-15 1996-05-14 Atr Wire & Cable Co., Inc. Method and apparatus for electrolytically plating copper
US5804053A (en) * 1995-12-07 1998-09-08 Eltech Systems Corporation Continuously electroplated foam of improved weight distribution
EP0915190A2 (fr) * 1997-10-30 1999-05-12 Daiki Engineering Co., Ltd. Procédé et appareil pour l'alimentation des ions métalliques à un bain pour l'électroplacage des alliages

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