Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
  • C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
  • C23F13/08—Electrodes specially adapted for inhibiting corrosion by cathodic protection; Manufacture thereof; Conducting electric current thereto
  • C23F13/12—Electrodes characterised by the material
• • 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
• • 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
  • C25B11/093—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 at least one noble metal or noble metal oxide and at least one non-noble metal oxide
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/26—Anodisation of refractory metals or alloys based thereon

Definitions

• an electrode for use in electrolytic processes comprises an electrically conductive base of which at least the surface is formed of a filmforming metal or a film-forming" alloy, and an electrically conductive coating on at least part of the surface of the base, the coating comprising a mixture containing at least one chemical compound of the film-forming metal or at least one chemical compound of at least one metallic constituent of the alloy and at least one chemical compound of the or each of at least one other metal.
• the tenn film-forming refers to the type of metal or alloy which will form an oxide film when immersed in the electrolyte to which it is to be subjected, the oxide film preventing further corrosive attack upon the metal or alloy.
• film-forming metals are titanium, tantalum, niobium and zirconium.
• mixture as used in this specification includes within its ambit compounds and solid solutions of the constituents concerned.
• a method of manufacturing an electrode for use in electrolytic processes comprises taking an electrically conductive base of which at least the surface is formed of a film-forming metal or a film-forming alloy, and applying to at least part of the surface of the base an electrically conductive coating comprising a mixture containing at least one chemical compound of the film-forming metal or at least one chemical compound of at least one metallic constituent of the alloy and at least one chemical compound of the or each of at least one other metal.
• the mixture comprises at least 50 percent of at least one chemical compound of the film-forming metal or of at least one metallic constituent of the alloy, with not more than 50 percent of at least one chemical compound of the or each of at least one other metal.
• the film-forming metal or alloy is titanium or a titanium-base alloy whereby said at least one chemical compound of the film-forming metal or of at least one metallic constituent of the alloy is at least one chemical compound of titanium.
• the film-forming metal or alloy can be tantalum or niobium or film-forming alloys including those elements. Zirconium can also be used provided that, in service, it will not contact halides.
• a suitable film-forming alloy is titanium-0. wt. percent palladium.
• the whole of the base is formed of the filmforming metal or alloy, but if required the base may comprise an electrically conductive core which is protected from corrosion by the electrolyte by an impervious layer of the film-forming metal or alloy which thereby provides the surface of the base.
• the core can be provided to enhance the electrical con ductivity of the base, or to reduce its cost.
• a suitable core material is copper.
• said at least one chemical compound of the or each of at least one other metal is at least one chemical compound of at least one of the Group VIII metals.
• the Group VIII metal can be a metal of the platinum group, by which is meant ruthenium, rhodium, palladium, osmium, iridium and platinum, or it can be iron, cobalt or nickel. If more than one metal of Group VIII are used, examples are platinum with iridium or ruthenium, platinum with iron, and iron with cobalt and nickel. Other metals then those of Group VIII can be used, for example manganese.
• the mixture may also comprise the metals concerned as well as chemical compounds of each of them.
• the metals are the film-forming metal titanium and ruthenium
• the mixture will comprise at least one chemical compound of titanium with at least one chemical compound of ruthenium, and can include some titanium metal and some ruthenium metal.
• the chemical compounds are preferably all oxides, although one or more of them may be borides, carbides, nitrides, fluorides, sulphides, aluminides, or silicides.
• the coating also comprises an underlayer beneath said mixture, at least percent of said underlayer consisting of at least one chemical compound of the filmforming metal or of at least one metallic constituent of the alloy.
• said at least one chemical compound of the underlayer is the same chemical compound or compounds as the chemical compound or compounds of that metal or those metals in the mixture.
• Each chemical compound of at least one other metal may also be a chemical compound of the said film-forming metal or of at least one metallic constituent of the film-forming alloy.
• the base of the electrode was chosen to be wholly a film-forming metal.
• examples are commercially pure titanium and commercially pure tantalum.
• the chosen metal was fabricated into the form of the required specimen electrodes.
• Stage 2 various alternatives can be used, and it must be borne in mind that titanium normally has a surface film of titanium dioxide having a rutile structure. A satisfactory method of removing substantially all of this rutile film is an etch in a 10 percent solution of oxalic acid for 16 hours at 80 C. Thus, the term etching as used in this specification refers to this treatment with oxalic acid.
• the oxide film can be prepared for coating by vapor blasting.
• Treatments (c) and (d) produce a titanium dioxide film of up to 2,000 A. in thickness, the anatase modification being usually formed.
• e. A heat-treatment of titanium in air at about 450 C. for about 30 minutes.
• f. A heat-treatment of titanium in air at about 600 C. for about 30 minutes.
• the air heat-treatment increases the thickness of the naturally occuring rutile-type coating, but it probably does not exceed 2,000 A.
• For titanium no treatment except a degreasing operation.
• tantalum a vapor-blasting treatment.
• Stage 3 can be carried out with deposition onto different specimen electrode bases, of any one of aluminum, chromium, cobalt, germanium, iridium, iron, lead, manganese, nickel, palladium, platinum, ruthenium, selenium, tin and tungsten metals.
• This metal deposition can be carried out by vaporizing the coating metal in vacuum alongside the titanium or tantalum specimen.
• the thicknesses achieved can be varied, but preferably each treatment is carried out with the intention of producing a thickness of about 100 A.
• platinum metal coatings on titanium measurements were taken on specimen electrodes which showed thicknesses of 25, 100 and 300 A., and for nickel a thickness of 400 A.
• nickel, cobalt and iron can be deposited on a single titanium specimen as successive layers in that order, each of about 100 A. in thickness.
• Coatings of the platinum group metals can also be applied by the use of suitable organic metal paints.
• suitable organic metal paints For ruthenium, an alcohol solution of ruthenium chloride with a suitable reducing agent can be used. This is referred to as RuCl paint.
• RuCl paint an alcohol solution of ruthenium chloride with a suitable reducing agent.
• these paints can be used as a mixture with organic titanium paint for titanium specimens.
• coatings can be applied as mixed resinate paints of tantalum and ruthenium with tantalum metal to ruthenium metal ratios of 1:1, 2:1 and 3: 1.
• this treatment can be one of the following:
• each paint layer can be subjected to a heat-treatment in air for 10 minutes at 250 C., and then minutes at 450 C. Two coats of paint are preferably applied in each case with this heat-treatment applied after each coat.
• alternate paint layers of titanium paint and RuCl paint can be applied to titanium bases, the same heattreatments being used. Four layers are preferably applied altogether.
• Another last stage treatment which can be given is immersion in an oxidizing bath of molten commercial grade sodium nitrate at from 450 C. up to about 600 C. Typically immersion is extended for about 30 minutes, although times of up to about 60 hours can be used.
• an electrically conductive base of which at least the surface is of a film-forming metal or alloy is first subjected to a preparation process and then has precipitated thereon the required mixture of chemical compounds.
• This may be carried into effect by treating the film-forming metal or alloy with an acid corrosive thereto for sufi'rcient time to dissolve some of the film-forming metal or alloy, adding to the acid a source of ions of the required other metal or metals, and causing precipitation of a mixed oxide of the film-forming metal or one constituent of the film-forming alloy and of the other metal or metals on to the base.
• a titanium-base can be treated with boiling sulphuric acid for at least 1 hour, and ferric chloride is then addedto the solution followed immediately by an oxidizing agent such as potassium chlorate.
• the sulphuric acid prepares the titanium surface for coating, and dissolves some titanium as Ti ions. Oxidation converts the Ti" and the F e"" ions to Ti and Fe' ions which are unstable and will coprecipitate as a mixed titanium and iron oxide.
• Example 1 A commercially pure titanium base was fabricated and then subjected to a vacuum treatment at about 700 C. for about 30 minutes. After exposure of the base to air, a metallic coating of manganese was applied by vaporizing a manganese sample in vacuum alongside the base.
• the coated base was treated in air at about 450 C. for about 30 minutes to produce a specimen electrode provided with a coating containing a mixture of titanium and manganese oxides.
• the coating contained more titanium oxide than manganese oxide and may contain some manganese metal.
• the electrode thus produced was given a conductance test by being connected as an anode in a 22 percent by weight solution of brine at room temperature.
• a titanium cathode was located 5 cm. from the anode, and 5 volts of direct current were applied.
• the specimen electrode was electrically conductive, initially passing a current of 2.5 kiloamperes/ml
• the average current density between 5 and 60 minutes operation was 0.6 ka/mF.
• Example 2 The materials and processes of Example 1 were followed with the use of a nickel layer about 400 A. in thickness instead of manganese.
• the resulting coating contained a mixture of titanium and nickel oxides.
• the electrode initially passed a current of 2.5 ka/m
• the average current density between 5 and 60 minutes operation was 2.1 ka/mF, and between 1 and 10 hours 0.9 ka/m.
• Example 3 A titanium base was anodized at 20 volts in a 5 percent sulphuric acid electrolyte for a few seconds to produce an oxide film of about 2,000 A. in thickness. The base was then provided with a cobalt coating and heat-treated as described for manganese in Example 1 to produce mixed coating containing titanium and cobalt oxides.
• the described conductance tests were used, the current densities being 1.8, 1.4 and 1.2 ka/m. initially, from 5-60 minutes and from 1-10 hours respectively.
• the initial value of the potential between the brine solutio and the specimen electrode was also measured and was found to be 2,150 millivolts.
• Example 4 A titanium base was oxidized in air at about 450 C. for about 30 minutes. This produces a thickened oxide film up to about 2,000 A. thick. The base was then provided with an iron coating about 100 A. in thickness by vacuum deposition, as described in Example 1.
• the coated base was subjected to vacuum at about 450 C. for about 30 minutes to diffuse some of the oxygen content of the titanium oxide film into the iron coating.
• a specimen electrode having an underlayer of which at least percent was a titanium oxide, and a coating on the underlayer comprising a mixture of oxides of iron and titanium.
• Example 5 A titanium base was etched in oxalic acid using the etching procedure described above, and was then provided with subsequent layers of nickel, cobalt and iron, each layer being about A. in thickness. The layers were each deposited in turn by vacuum deposition as described in Example 1. The
• Example 1 heat-treatment at 450 C. of Example 1 was then applied to produce a coating on the titanium base comprising a mixture of oxides of titanium, nickel, cobalt and iron.
• the described conductance tests were used, the current densities being 3.1 and 1.9 ka/m. initially and from 5-60 minutes respectively.
• the initial overpotential was found to be 350 millivolts.
• Example 6 The procedures of Example 5 were followed with the substitution of platinum for the vacuum deposition.
• the coating After air oxidation, the coating comprises a mixture of oxides of titanium and platinum, and some platinum metal.
• Example 7 A titanium base was air oxidized as described in Example 4 and was then coated with platinum and air oxidized as described in Example 6.
• Example 8 A titanium base was anodized as described in Example 3, and then provided with a platinum coating and air oxidized as described in Example 6.
• Example 10 A titanium base was etched as described in Example and was provided with a palladium coating by the evaporation of a palladium sample alongside the base in vacuum.
• the coating was oxidized in air at about 450 C. as described in Example 1. This produced a mixed oxide coating on the surface of the base of titanium and palladium, the coating containing some palladium metal.
• Example 11 A titanium base was provided with a coating as described in Example 10, except that air treatment was carried out at 350 C. The initial overpotential was found to be 340 millivolts.
• Example 12 A titanium base was etched as described in Example 5, and was then provided with two coats of an organic palladium paint. For each coat of paint the base wassubjected to a heattreatment in air for 10 minutes at 250 C. and then 20 minutes at 450 C. This produced a coating on the titanium base comprising a mixture of titanium and palladium oxides.
• Example 13 A titanium base was etched as described in Example 5 and was then provided with two coats of an organic palladium paint mixed with an organic titanium paint. For each coat of paint, the base was subjected to a heat-treatment in air for 10 minutes at 250 C. and then 20 minutes at 450 C. This produced a coating on the titanium base comprising a mixture of titanium and palladium oxides.
• Example 14 In this example the same processes as those described in Example 12 were followed, except that each paint layer was provided with a single heat-treatment in air at 650 C. for about 20 minutes.
• Example 15 In this example the same processes as those described in Example 12 were followed, except that a ruthenium organic paint was used instead of a palladium organic paint.
• Example 16 A titanium base was oxidized as described in Example 4, and was provided with a painted coating as described in Example 15 of ruthenium organic paint.
• the specimen electrode was then subjected to a 20 minutes treatment in an equal parts ammoniabutane mixture at 450 C.
• the initial overpotential was found to be 28 millivolts.
• Example 18 In this example the processes of Example 17 were followed except that prior to the ammonia-butane treatment, the electrode was immersed in an oxidizing bath of molten commercial grade sodium nitrate at about 450 C. for about 30 minutes.
• the initial overpotential was found to be millivolts.
• Example 19 In this example the processes of Example 17 were followed, except that, as an organic paint, there was used an alcohol solution of ruthenium chloride with a reducing agent.
• an organic paint there was used an alcohol solution of ruthenium chloride with a reducing agent.
• the initial overpotential was found to be 1 l5 millivolts.
• Example 20 in this example, the processes of Example 19 were followed, there being an additional oxidizing stage in the immersion of the electrode in the sodium nitrate bath described in Example 18.
• the initial overpotential was found to be 27 millivolts.
• Example 21 A titanium base, after being degreased, was provided with two coats of a mixed paint of organic titanium and an alcohol solution of ruthenium chloride with a reducing agent. Each coat was treated in air at 450 C. for about 20 minutes.
• the resulting electrode had a coating comprising a mixture of oxides of ruthenium and titanium.
• the initial overpotential was found to be 54 millivolts.
• Example 22 In this example the processes of Example 21 were followed with the addition of a sodium nitrate bath treatment at 450 C. for 30 minutes.
• the initial overpotential was millivolts.
• Example 23 A titanium base was degreased and was provided with alternate coats of ruthenium chloride paint described above and an organic titanium paint. Each coat was subjected to an air treatment at 450 C. for about 20 minutes. The first coat was of titanium paint, and four coats were applied altogether.
• the initial overpotential was found to be 20 millivolts.
• Example 24 In this example, the processes of Example 23 were followed with the addition of a final treatment in a molten sodium nitrate bath at 450 C. for about 30 minutes.
• the initial overpotential was found to be 17 millivolts.
• Example 25 A tantalum base was degreased and vapor blasted, and was then provided with four coats of a mixture of equal parts of ruthenium and tantalum organic paints.
• the metal to metal ratio of ruthenium to tantalum was approximately 1:1.
• Each coat was subjected to an air treatment at about 250 C. for about 10 minutes and further treatment at about 450 C. for about 20 minutes.
• a conductance test was carried out between the specimen electrode as an anode and a titanium cathode, and with an applied potential of 6 volts the initial current passed was 1.5 amps and measurements taken after 10 hours and 100 hours showed currents of 1.43 and 1.12 amps.
• Example 26 In this example the processes of Example 25 were followed except that the paint was a 2:1 ratio of tantalum to ruthenium paints. Thus the metal to metal ratio was about 2: 1.
• Examples 25 and 26 were compared with a control of a platinum electroplated titanium base of the same dimensions as the electrodes of Examples 25 and 26. in the same conductance test the control initially passed a current of 1.3 amps, and the same current was still flowing after 10 hours.
• the initial overpotentials of the electrodes of Examples 25 and 26 compared favorably with the initial overpotential of the control at the usual current densities of about 6 ka/mfi.
• Example 27 A titanium base was degreased and treated in boiling 7 percent sulphuric acid for about 1 hour. This dissolved some titanium as Ti ions, and prepared the titanium surface for coating.
• the sulphuric acid solution was then provided with ml. of 0.5 molar solution in water of ferric chloride to provide a source of Fe ions in the solution, and this was immediately followed by the addition of 75 ml. of a 0.1 molar solution in water of potassium chlorate to the solution.
• the oxidizing effect of potassium chlorate is believed to convert the Ti"" and the Fe"" ions to Ti'' and Fe"" which, because of their instability react with water from the solution to coprecipitate as the relatively insoluble mixed titanium and iron oxide on the titanium base.
• the electrode so formed was tested in a saturated sodium chloride solution at room temperature, current passing with an applied voltage of 8 volts being 1.5 amps.
• a platinum electrode plated titanium electrode of the same dimensions used as a control passed a current of 1.2 amps.
• the current passed by the electrode of this example was still at the same level after more than 70 hours, and there was no loss in weight which indicated that no dissolution of the electrode was taking place.
• the coating produced upon the electrode comprises a mixture of oxides of titanium or tantalum and oxides of the metal concerned.
• the portion of oxide of the nontitanium metal varied between 5 and 50 percent of the overall oxide composition of the coating.
• the coating also comprises the metal concerned as a metal and not an oxide.
• the mixture of oxides was provided with an underlayer consisting almost entirely of rutile titanium. Any other substances in this underlayer were present by way of contamination, for example because of original impurity, or by diffusion from the mixture, or were titanium metal.
• a method of manufacturing an electrode for use in electrolytic processes comprising providing an electrically conductive base of which the surface is formed of a film-forming metal or alloy selected from the group consisting of titanium, tantalum, niobium and zirconium and alloys based upon at least one of these metals, treating the base with an acid which is corrosive to the film-forming metal or alloy to dissolve some of the film-forming metal or alloy from the base to provide ions of the film-forming metal, adding to the acid a source of ions of at least one other metal, providing an oxidizing means for producing oxides of said film-forming metal and of said other metals andprecipitating upon the base a mixture of oxides of said film-forming metal and of said other metal.
• a method according to claim 2 wherein the oxidizing means is the use of potassium chlorate.

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• Mechanical Engineering (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
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• 1967
  • 1967-09-26 GB GB43678/67A patent/GB1246447A/en not_active Expired
• 1968
  • 1968-09-23 LU LU56937D patent/LU56937A1/xx unknown
  • 1968-09-24 DE DE1796220A patent/DE1796220B2/de active Pending
  • 1968-09-25 US US762621A patent/US3645862A/en not_active Expired - Lifetime
  • 1968-09-25 SE SE12942/68A patent/SE344020B/xx unknown
  • 1968-09-26 BE BE721448D patent/BE721448A/xx unknown
  • 1968-09-26 NL NL686813812A patent/NL143437B/xx unknown
  • 1968-09-26 FR FR1583370D patent/FR1583370A/fr not_active Expired
  • 1968-09-26 CA CA031019A patent/CA929487A/en not_active Expired
  • 1968-09-26 AT AT939968A patent/AT299261B/de not_active IP Right Cessation
  • 1968-09-26 ES ES358533A patent/ES358533A1/es not_active Expired
  • 1968-09-26 CH CH1439668A patent/CH530222A/de not_active IP Right Cessation

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