Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
  • C25F1/02—Pickling; Descaling
  • C25F1/04—Pickling; Descaling in solution

Definitions

• the invention relates to a method and arrangement, defined in the independent claims, for improving the quality of an object made of a copper-based metal alloy.
• Oxide layers are difficult to observe or measure on the copper surface, and they are not necessarily distinguished without specific equipment.
• the removal of thick oxide layers from the copper surface is relatively simple, but on the other hand, the removal of the last molecular layers has turned out to be more troublesome.
• Oxide layers on the surface of copper disturb for instance extrusion, so that when removing the oxide layers, there is created harmful extrusion scrap. The treatment and recirculation of extrusion scrap lead to extra expenses.
• etching In the cleaning of copper metal surfaces, there is generally applied etching, i.e. the metal surface is chemically cleaned of the oxide layer by means of dissolution. It is generally known that all grease and oil should be removed from the product surface before etching. Normally the etching of copper metals is carried out in a sulfuric acid - water solution, and it removes the major part of the oxides created on the surface. In conventional sulfuric acid etching, there is achieved a low oxide layer level immediately after the etching process, but in practice the dissolved oxygen of the acid and the slowness of the final washing may double the oxide layer after drying.
• One way of preventing the creation of oxides on the surface of a copper object is to insulate the copper object by a protective gas atmosphere in order to prevent oxidation.
• the object of the present invention is to avoid the drawbacks of the prior art and to introduce a new solution for improving the quality of an object made of a copper- based metal alloy.
• a particular object of the invention is to improve the quality of an object made of a copper-based metal alloy by removing oxides from the surface thereof by means of cathodic reduction.
• the method according to the invention has many advantages.
• the invention relates to a method for improving the quality of an object made of a copper-based metal alloy, according to which method the object is treated at least in an oxide removal unit, so that in the oxide removal unit, oxides are removed from the object surface by means of cathodic reduction.
• cathodic reduction By applying cathodic reduction, the oxides present on the copper surface are reduced to copper, so that the oxide layer is eliminated from the surface of the copper object.
• the employed electrolyte in cathodic reduction is sodium carbonate solution.
• the employed electrolyte in cathodic reduction is sulfuric acid solution.
• the employed cathode in cathodic reduction is the object made of a copper-based metal alloy, and the employed anode is a non-soluble material, such as a platinum anode or a platinum-coated titanium anode.
• a non-soluble material such as a platinum anode or a platinum-coated titanium anode.
• Other suitable anode materials are for example lead or titanium coated with iridium oxide.
• oxygen on the anode there is created oxygen, and on the cathode there is created copper.
• an ion-selective membrane that is impermeable to oxygen.
• the membrane is advantageously placed between the anode and the cathode in order to prevent the oxygen from being transferred from the anode to the cathode. From the space between the anode and the membrane, oxygen is exhausted along with the solution circulation, or through oxygen exhaustion apertures.
• the membrane is arranged symmetrically around the cathode, so that it surrounds the whole cathode. In this fashion, the oxidation and reduction reactions are made to proceed smoothly, and the voltage is distributed evenly in the whole cell.
• an object made of a copper-based metal alloy is subjected to preliminary washing prior to the cathodic reduction.
• an object made of a copper-based metal alloy is subjected to etching by sulfuric acid before the cathodic reduction.
• the thickest oxide films are removed rapidly prior to the cathodic reduction.
• sulfuric acid films are removed by mechanical drying.
• the object is subjected to a rapid pressurized water washing after the cathodic reduction.
• the remaining oxide layer after a treatment performed in the oxide removal unit is preferably left at a degree of 0.001 - 0.01 nanometers, i.e. advantageously the oxide film is nearly completely removed.
• the object is after the oxide removal unit conducted into a working process, such as a continuously operated extrusion treatment.
• the oxide removal unit and the working process are insulated from the surroundings by protective gas.
• the invention also relates to an arrangement for realizing the method according to claim 1 for improving the quality of an object made of a copper-based metal alloy, said arrangement comprising at least an oxide removal unit and elements for realizing cathodic reduction, such as an anode, a cathode and an electrolyte, so that the access of the oxygen created on the anode to the cathode is prevented by a membrane that is impermeable to oxygen.
• FIG. 1 A diagram of the principle of the method according to the invention
• Figure 1 illustrates the method according to the invention in the form of a block diagram.
• a round wire-like object 1 made of copper is conducted to an oxide removal unit 3.
• the oxide removal unit 3 includes a cathodic reduction arrangement.
• the oxide-free copper wire 2 obtained from the oxide removal unit is conducted to a working process, such as a continuously operated extrusion treatment 4.
• the oxide removal unit and the working process unit are insulated from the surroundings by protective gas.
• FIG. 2 shows a cross-section of the cathodic reduction process carried out in an oxide removal unit.
• copper wire is washed prior to the oxygen removal proper. Thereafter the copper wire is subjected to preliminary etching by sulfuric acid, so that the thickest oxides layers are removed. Sulfuric acid films left after etching are removed for instance by mechanical drying. Then the cathodic reduction is performed.
• the copper wire 5 is placed in a chamber 9 containing sodium carbonate solution 11 , and electric current is conducted to said chamber.
• the copper wire 5 serves as a cathode, on which copper oxide is reduced to copper, and thus the oxides are eliminated nearly completely from the copper surface.
• the employed anode 6 is a non-soluble platinum anode, on which oxygen is created.
• the solution 11 fills the chamber 9 all over.
• the access of the oxygen created on the anode is prevented by an ion selective membrane 8 that is impermeable to oxygen, which preferably surrounds the whole cathode.
• the employed housing for the membrane is an insulated, perforated tube 10 in order to maintain the liquid connection.
• the membrane is symmetrically arranged around the cathode, which helps the reduction and oxidation reactions to proceed evenly.
• an oxygen exhaust aperture 7, through which the oxygen created on the anode is removed from the system.

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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)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• ing And Chemical Polishing (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2002
  • 2002-07-31 FI FI20021425A patent/FI114871B/fi not_active IP Right Cessation
• 2003
  • 2003-07-17 EP EP03740525A patent/EP1552042A1/en not_active Withdrawn
  • 2003-07-17 WO PCT/FI2003/000572 patent/WO2004011699A1/en not_active Application Discontinuation
  • 2003-07-17 JP JP2004523829A patent/JP2006501362A/ja not_active Abandoned
  • 2003-07-17 US US10/523,552 patent/US20060091021A1/en not_active Abandoned
  • 2003-07-17 BR BR0313009-6A patent/BR0313009A/pt not_active IP Right Cessation
  • 2003-07-17 AU AU2003281678A patent/AU2003281678A1/en not_active Abandoned
  • 2003-07-17 PL PL03373766A patent/PL373766A1/xx not_active Application Discontinuation
  • 2003-07-17 CN CN03818395.1A patent/CN1671890A/zh active Pending
  • 2003-07-17 MX MXPA05001196A patent/MXPA05001196A/es unknown
  • 2003-07-17 EA EA200500075A patent/EA006828B1/ru unknown
  • 2003-07-22 TW TW092119934A patent/TW200403360A/zh unknown

Non-Patent Citations (1)

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