Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/069—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of at least one single element and at least one compound; consisting of two or more compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds

Definitions

• the present invention relates, in general, to electrolysis cells and relates more particularly to an anode electrode stable in dimensions, of the type comprising a core of electroconductive material and an electrocatalytic conductive coating.
• the invention also relates to a method of manufacturing such an electrode.
• electrolytic cells in which the anode is constituted by a core of a metal called stop metal, of the type used for rectifiers with stop layer are expensive and require difficult and expensive machining.
• stop metals which include in particular titanium, tantalum, columbium, zirconium, moybdenum and tungsten, are expensive and require difficult and expensive machining.
• the core of the anode can also be produced from oxides of stop metals.
• the anode electrodes of the aforementioned type consisting almost entirely of stop metals, noble metals or oxides of these metals, are particular stable in size over time.
• a drawback results from the difficulty of treatment, in particular of mechanical treatment, of such materials.
• One of the aims of the present invention consists precisely in making it possible to produce anodes at a reduced cost and in a simplified manner, while offering the possibility of improving the shape of the anodes constructed, without appreciably affecting their electrical properties.
• an anode electrode stable in dimensions of the type comprising a core of electroconductive material and an electrocatalytic conductive coating, characterized in that an electroconductive core is first produced by molding. starting from a common metal melting at high temperature, such as iron, an iron alloy, aluminum, copper, in that said core is then introduced into a first electrolytic bath melted at high temperature, temperature, consisting of a mixture of alkali halides and stop metal halides, to form a first conductive coating on the core, and in that said core provided with its first coating is then introduced into a second electrolytic bath comprising noble metals to form a second electrocatalytic conductive coating on the core provided with its first conductive coating.
• a common metal melting at high temperature such as iron, an iron alloy, aluminum, copper
• the second electrolytic bath can advantageously be constituted by a molten electrolytic bath at high temperature, consisting of a mixture of halides alkali and noble metal halides or a mixture of alkali halides and noble metal halides and stop metals.
• the second electrolytic bath can also optionally consist of an aqueous solution of noble metal, such as platinum, ruthenium, iridium, palladium.
• noble metal such as platinum, ruthenium, iridium, palladium.
• the core is made of iron or ferrous alloy, aluminum or aluminum alloy, copper or copper alloy, a coating of stop metals or metal oxides d 'stop, then a second coating of noble metals such as platinum or oxides of these noble metals or noble metals associated with stop metals such as titanium, the mechanical and electrical qualities of the anode remain excellent compared to anode electrodes, the core of which is made entirely of stop metal such as titanium or tantalum.
• the advantageous characteristic is the formation of the molded core based on iron or ferrous alloy by molding molten metals.
• the second electrocatalytic conductive coating can be produced from a mixture of alkali halides and either halides of a noble metal or of several noble metals, or halides of noble metals and stop metals.
• stop metal is meant a metal of the type used for rectifiers with a stop layer. Titanium, tantalum, columbium, zirconium, molybdenum and tungsten belong to this family.
• the operations of coating the electroconductive core are carried out in an inert atmosphere such as an argon or helium atmosphere.
• the temperature of the molten electrolytic baths is between 300 and 1000 ° C, this temperature naturally depending on the type of core and the metals to be treated.
• the electrode provided with its two coatings is then subjected to an oxidation heat treatment.
• an anode core is produced by melting and molding inexpensive common metals, such as iron or an iron alloy, aluminum, copper or alloys of these metals.
• the core could also be made from a metal such as. iron, for example semi-worked.
• the molding technique makes it easier to produce anodes of very different geometries.
• the core of the anode then receives a cathodic electrolytic deposit of a stop metal, such as titanium, tantalum or tungsten.
• a stop metal such as titanium, tantalum or tungsten.
• This deposit makes it possible to coat the core of the anode with a layer of stop metal, the thickness of which can be very reduced, for example less than 3 mm.
• stop metal used are thus very reduced, although the electrode is coated over its entire surface and therefore has interesting electrical and mechanical qualities.
• the molten electrolytic bath allowing the deposition of a stop metal is a high temperature bath comprising a mixture of alkali chlorides, such as sodium chloride, potassium chloride, lithium chloride, or alkaline fluorides, such that sodium florure and potassium fluoride or fluorides and chlorides of stop metals or compounds of stop metals, such as tungsten compounds.
• alkali chlorides such as sodium chloride, potassium chloride, lithium chloride, or alkaline fluorides, such that sodium florure and potassium fluoride or fluorides and chlorides of stop metals or compounds of stop metals, such as tungsten compounds.
• Anodic corrosion of the stop metal and of the mixture of molten chlorides can thus take place with the intervention of tetrachloride of the stop metal and the intervention of fluorinated compounds of the stop metal.
• the coating of the iron-based core is carried out in an inert atmosphere of rare gases such as argon or helium.
• the melting temperature of the electrolytic bath can be between approximately 300 and 1000 ° C.
• the density of the anode currents can reach 10 kA / m 2 using for the cathodic deposition of stop metal a soluble anode having the same composition as that of the stop metal to be deposited.
• the deposit is obtained at anode and cathode potentials controlled and at anode and cathode current density always controlled with cell voltages between 0 and 7 volts.
• the current densities can be, for example, from 100 to 700 A / m 2 at the cathode and from 10 to 90 A / m 2 at the anode.
• the second coating can be carried out using the same technique as for the first coating, that is to say using a molten electrolytic bath at high temperature, a mixture of alkali halides and noble metal halides, which may optionally be combined with stop metal halides.
• the noble metal can still be deposited by aqueous baths, ie galvanic.
• the present invention lends itself well to the manufacture of anodes of very diverse shapes, in particular of anodes provided with several electrode connections coupled to the anode barrier, since in particular the molding technique makes it possible to form cores with the most varied shapes. .
• An anode produced according to the present invention has excellent mechanical and chemical resistance, especially to corrosion, including for temperatures above normal.

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Publications (3)

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Cited By (5)

Citations (4)

• 1978
  • 1978-05-19 FR FR7814920A patent/FR2426095A1/fr active Granted
• 1979
  • 1979-05-18 DE DE7979400313T patent/DE2964788D1/de not_active Expired
  • 1979-05-18 EP EP79400313A patent/EP0005674B1/de not_active Expired

Patent Citations (4)

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