CA1058563A - Anode for electrolytic processes - Google Patents
Anode for electrolytic processesInfo
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- CA1058563A CA1058563A CA230,660A CA230660A CA1058563A CA 1058563 A CA1058563 A CA 1058563A CA 230660 A CA230660 A CA 230660A CA 1058563 A CA1058563 A CA 1058563A
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- oxide
- tin oxide
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- 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
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- Organic Chemistry (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
- Chemically Coating (AREA)
Abstract
ANODE FOR ELECTROLYTIC PROCESSES
Abstract of the Disclosure An electrode, for use in electrolytic processes, comprises a valve metal substrate, such as titanium, a coating thereon of conductive tin oxide, and an outer coating of a noble metal or noble metal oxide.
Abstract of the Disclosure An electrode, for use in electrolytic processes, comprises a valve metal substrate, such as titanium, a coating thereon of conductive tin oxide, and an outer coating of a noble metal or noble metal oxide.
Description
~[)SB563 BACKGROUMD OF THE INVENTION
The present invention relates to improved electrodes particularly adapted for use as anodes in electrochemical pro-cess involving the electrolysis of brines.
A variety of materials have been tested and used as chlorine anodes in electrolytic cells~ In the past, the material most commonly used for this purpose has been graphite. However, the problems associated with the use of graphite anodes are several. The chlorine overvoltage of graphite is relatively high, in comparison for example with the noble metals. Further-more, in the corrosive media of an electrochemical cell graphite wears readily, resulting in substantial loss of graphite and the ultimate expense of replacement as well as continued main-tenance problems resulting from the need for frequent adjustment of spacing between the anode and cathode as the graphite wears away. The use of noble metals and noble metal oxides as anode materials provides substantial advantages over the use of graphlte. The elec~rical conductivity of the noble metals is substantially higher and the chlorine overvoltage substan-tially lower than that of graphite. In addition, the dimen-sional stability of tha noble metals and noble metal oxides represents a substantial improvement over graphite. However, the use of noble metals as a ma~or material of construction in anodes results~in an economic disadvantage due to the ex-cessively high cost of such materials.
In a~tempts to avoid the use of the expensive noble metals various other anode materials have been proposed for
The present invention relates to improved electrodes particularly adapted for use as anodes in electrochemical pro-cess involving the electrolysis of brines.
A variety of materials have been tested and used as chlorine anodes in electrolytic cells~ In the past, the material most commonly used for this purpose has been graphite. However, the problems associated with the use of graphite anodes are several. The chlorine overvoltage of graphite is relatively high, in comparison for example with the noble metals. Further-more, in the corrosive media of an electrochemical cell graphite wears readily, resulting in substantial loss of graphite and the ultimate expense of replacement as well as continued main-tenance problems resulting from the need for frequent adjustment of spacing between the anode and cathode as the graphite wears away. The use of noble metals and noble metal oxides as anode materials provides substantial advantages over the use of graphlte. The elec~rical conductivity of the noble metals is substantially higher and the chlorine overvoltage substan-tially lower than that of graphite. In addition, the dimen-sional stability of tha noble metals and noble metal oxides represents a substantial improvement over graphite. However, the use of noble metals as a ma~or material of construction in anodes results~in an economic disadvantage due to the ex-cessively high cost of such materials.
In a~tempts to avoid the use of the expensive noble metals various other anode materials have been proposed for
- 2 -~L~5~3S63 use as coatings over valve metal substrates. In U.S. patent
3,627,669, it is disclosed that mixtures of tin dioxide and oxides of antimony can be formed as adherent coatings on a valve metal substrate to form an anode useful in electro-chemical processes. In the electrolytic production of chlorine, anodes of this type provide the advantage of economy in the elimination of the use of expensive noble metals or noble metal oxides. In addition the tin oxide coa~ing provides an effective protection or the substrate. However, the tin oxide compositions, although useful as an anode material, exhibit a chlorine overvoltage that is substantially higher than that of the noble metals or noble metal oxides. Thus, despite the elimination of expensive noble metals, the cost of chlorine production, in processes using such anodes, is rela-tively high.
Considerable effort has been expended in recent years in attempts to develop improved anode materials and structures utilizing the advantages of noble metals or noble metal oxides.
A great amount of effort has been directed to the development of anodes having a high operative surface area of noble metal or noble metal oxide in comparison with the total quantity of the material employed. This may be done, for example, by employing the noble metal as a thin film or coating over an electrically conductive substrate. However, when it is at-tempted to minimize the aforementioned economic disadvantage of the noble metals by applying them in the form of very thin films over a metal substrate, it has heen found that such ~S~35~3 very thin films are often porous. The result is an exposure of the substrate to the anode environment, through the pores in the outer layer. In addition, in normal use in an electro-lytic cell, a small amount of wear, spalling or flaking off of portions of the noble metal or noble metal oxide is likely to occur, resulting in urther exposure of the substrate.
Many materials, otherwise suitable for use as a substrate are susceptible to chemical attack and rapid deterioration upon exposure to the anode environment~ In an attempt to assure minimum deterioration of the substrate under such circumstances, anode manufacturers commonly utilize a valve metal such as titanium as the substrate material. Upon ex-posure to the anodic environment, ti~anium, as well as other valve metals, will form a surface layer of oxide which serves to protect the substrate from further chemical attack. The oxide thus formed, however, is not catalytically active and as a result the operative surface area of the anode is decreased.
Accordingly, it is an object of the present invention to provide improved electrodes for use as anodes in electrolytic processes. It is a further object to provide such anodes having an operative surface of noble metal or noble metal oxide and having improved efficiency and maintenance charac-teristics.
ST~TEMENT OF INVENTION
This invention provides a novel electrode, especially suited for use as an anode in chlor-alkali cells; the novel electrode comprising a valve metal substrate having a pro-tective coating of conductive tin oxide on the surface ~L~5~i563 thereof and an outer, thin layer of a noble metal or noble metal oxide. Electrodes of this type exhibit a high degree of durability in addition ~o the relatively low overvoltage characteristics of a noble metal or noble metal oxide, making them well-suited for use as anodes in the electrolytic pro-duction of chorine.
Amvng the advantages of such construction is the pro-tection afforded the metal substrate by the coating of con ductive tin oxide. The preferred substrate materials of the anodes of the invention are the valve metals, such as titanium tantalum, niobium or zirconium, especially titanium. However, where suitably thick intermediate layers of tin oxide are employed, other more conductive metals may be considered for use as substrates. The tin oxide coating, which may range in coating weight from about 0.1 grams per square meter to 100 grams per squar~ meter or more, depending on the degree of protectlon desired, prevents contact of the substrate and the electrolyte, thus preventing or minimizing corrosion or surface oxidation and the attendant deterioration or passi-vation of the substrate. At the same time, the outer layer provides the advantageous catalytic properties of the noble metals or noble metal oxides. In addition, the protective layer of conductive tin oxide permits the use of a relatively thin layer of the noble metal or noble metal oxide and a consequent savings resulting from a minimal use of the pre-cious metal. Typically, the layer of noble metal or noble metal oxide will have a coating weight in the range of about 0.1 grams per square meter to about 20 grams per square meter or higher and preferably about 3 to 10 grams per square meter ~OS8563 in thickness. The disadvantage of pores or pinholes in the noble metal layer common in extremely thin layers is obviated by the presence of ~he intermediate layer of conductive tin oxide. Pores or pinholes in the noble metal layer, or wear-ing away of that outer layer over long periods of use result in the gradual exposure of ~he tin oxide layer. The inter-mediate layer of tin oxide will continue to provide a cata-lytically active sur~ace in those exposed areas. The cata-lytic characteristics o~ tin oxide, although not as high as the noble metals or noble metal oxides, is quite substantially higher than the valve metal oxide. Thus, the overall deter-ioration of the catalytic properties of the anode is more gradual and maintenance problems are accordingly lesse~ed.
In additionr it has been found that the intermediate layer of tin oxide provides an increase in surface area of the anode with a consequent improvement in overvoltage.
It has further been found that the adhesion of the noble metal or noble metal oxide to the substrate is increased by the presence of the intermediate layer of tin oxide and the problem of spalling of the surface layer is thereby reduced.
DE5CRIPTION OF THE :PREF RRED EMBODIMENTS
The valve metal substrate which forms the inner or base component of the electrode is an electroconductive metal having sufficient mechanical strength to serve as a support for the coating and having a high degree of chemical resistivity, es-pecially to the anodic environment of electrolytic cells.
Typical valve metals include, for example, Ti, Ta, Nb, Zr, and 5~3 alloys thereof. The valve metals are well known for their tendency to form an inert oxide film upon exposure to an anodic environment. The preferred valve metal, based on cost and availability as well as electrical and chemical properties is titanium. The conductivity of the substrate may be improved, if desired, by providing a central core of a highly conductive metal such as copper. In such an arrange-mentr the core must be electrically connected to and completely protected by the valve metal substrate.
Tin oxide can be readily formed as an adherent coatiny on a valve metal substrate, in a manner described hereinafter, to provide a protective, electrically conductive layer which is especially resistant to chemical attack in anodic environ ments. Pure tin oxide however has a relatively high electrical resistivity in comparison to metals and exhibits undesireble change in electrical resistivity as a function of temper-ature. It is well known that the electrical stability of tin oxide coatings may be substantially improved and the electrical resistivity lowered through the introduction of a minor prop-ortion of a suitable inorganic material (commonly referred to as a "dopant"). A variety of materials, especially various metal oxides and other metal compounds and mixtures thereof, have been disclosed in the prior art as suitable dopants for stabilizing and lowering the electrical resistivity of tin oxide compositions. Among the materials shown in the prior art to be useful as dopants in conductive tin oxide compositions and which may be employed in the tin oxide coat-ing compositions of the anodes of this invention are included, for example, fluorine compounds, especially the metal salts 10585~;3 of fluorine, such as sodium fluoride, potassium fluoride, lithium fluoride, berylium fluoride, aluminum fluoride, lead fluoride, chromium fluoride, calcium fluoride, and other metal fluorides; hydrazine, phenylhydrazine; phos-phorus compounds such as phosphorus chloride, phosphorus oxychloride, ammoni~ phosphate, organic phosphorus esters such as tricresyl phosphate; as well as compounds of tel-luriumr tungsten, antimony, molybdenum, arsenic, and others and mixtures thereof. The conductive tin oxide coatings of this invention comprise tin oxide, preferably containing a minor amount of a suitable dopant. The preferred dopant is an antimony compound which may be added to the tin oxide coating composition either as an oxide or as a compound such as SbC13 which may form the oxide when heated in an oxidizing atmosphere. Although the exact form o the antimony in the final coatinq is not certain, it is assumed to be present as Sb2O3 and data and proportions in this specification and the appended claims are based on that assumption. The pre~erred compositions of this invention comprise mixtures of tin oxide and a minor amount of antimony oxide, the latter being present preferably in an amount of between about 0.1 and 20 weight per-cent (calculated on the basis of total weight of SnO2 and Sb203 ) .
Conductive tin oxide coatings may be adherently formed on the surface of the valve metal substrate by various methods known in the art. Typically such coatings may be formed by first chemically cleaning the substrate, for example, by degreasing and etching the surface in a suitable :~S85~;3 acid, e.g., oxalic acid, then applying a solution of appro-priate thermally decomposable salts, drying and heating in an oxidizing atmosphere. The salts that may be employed include, in general, any thermally decomposable inoxganic or organic salt or ester of tin and dopant, e.g., antimony, including for example their chlorides, alkoxides, alkoxy halides, resinates, amines and the like. Typical salts in-clude for example, stannic chloride, dibutyltin dichloride, tin tetraethoxide, antimony trichloride, antimony penta-chloride and the like. Suitable solvents include for ex-ample, ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, amyl alcohol, toluene, benzene and other organic solvents as well as water.
The solution of thermally decomposable salts, containing for example, a salt of tin and a salt of antimony, or other dopant, in the desired proportions, may be applied to the cleaned surface of the valve metal substrate by painting, brushing, dipping~ rolling, spraying or other method. The coating is then dried by heating for example at about 100 to 200 C for several minutes to evaporate the solvent, and then heating at a higher temperature, e.g., 250 to 800 C
in oxidizing atmosphere to convert the tin and antimony com-pounds to their respective oxides. The procedure may be re-peated as many times as necessary to achieve a desired coat-ing weight or thickness. The final coating weight of this conductive tin oxide coating may vary considerably, but is preferably in the range of about 3 to about 30 grams per square meter.
_ g _ ~L~S~3S63 Optionally, a small amount, such as up to 3 percent by weight of a chlorine discharge catalyst such as at least one of the difluorides of manganese, iron~ cobalt or nickel may by included in the tin oxide coating to lower the overpoten-tial required for chlorine gas liberation in a chlor-alkali cell. The chorine discharge catalyst may be added to the tin oxide coating by suspending a fine particulate preformed sinter of tin dioxide and the catalyst in the solution of thermally decomposable salts. Such chlorine discharge catalysts in the tin oxide coating is not essential to the anodes of this inven-tion but may be employed if desired in a known manner such as disclosed in U.S. patent 3,627,669.
The outer coating of the anode comprises a noble metal or noble metal oxide such as platinum, iridium, rhodium, pal-ladium ruthenium or somium or mixtures or alloys of these metals or the oxides or mixtures of the oxides of these metals.
An outer coating of a noble metal may be applied by known methods such as electroplating, chemical deposition from a platinum coating solution, spraying, or other methods.
Preferably, the outer coating of the anode comprises a noble metal oxide. Noble metal oxide coating may be applied by first depositing the noble metal in the metallic state and then oxidizing the noble metal coating, for example, by gal-vanic oxidation or chemical oxidation by means of an oxidant such as an oxidizing salt melt, or by heating to an elevated temperature, e.g., 300 C to 600 C or higher in an oxidizing atmosphere such as air oxygen, at atmospheric or superatmos-pheric pressures to convert the noble metal coating to a 5~ ;3 coating of the corresponding noble metal oxide. Other suit-able methods include, for example, electrophoretic deposition of the noble metal oxide; or application of a dispersion of the noble metal oxide in a carrier, such as alcohol, by spraying, brushing, rolling, dipping, painting, or other method on to the tin oxide surface followed by heating at an elevated temperature to evaporate the carrier and sinter the oxide coating. A preferred method for the formation of the noble metal oxide coating involves coating the conductive tin oxide surface with a solution of a noble metal compound, evaporating the solvent and converting the coating of noblP
metal compound to the oxide by chemical or electrochemical reaction. For example, the conductive tin oxide surface may be coated with a solution of a thermally decomposable salt of a noble metal, such as a solution of a noble metal halide in an alcohol, evaporation of the solvent, followed by heat-ing at an elevated temperature such as between about 300 C
and 800 C in an oxidizing atmosphere such as air or oxygen for a period of time sufficient to convert the noble metal halide to a noble metal oxide. The procedure for formation of a noble metal or noble metal oxide coating may be repeated as often as necessary to achieve the desired thickness. The foregoing and other methods for the preparation of coatings of noble metals and noble metal oxides are well known in the art and may be found for example in U.S~ patent 3,711,385.
The following specific examples will serve to further illustrate this invention. In the examples and elsewhere in this specification and claims~ all temperatures are in degrees ~5~35~;3 Celsius and all parts and percentages are by weight unless otherwise indicated.
EXAMPLE I
IA. Pre~ration of conductive tin oxide coating A strip of titanium plate was prepared by immersion in hot oxalic acid for several hours to etch the surface, then washed and dried. The titanium was then coated with a compo-sition of tin oxide doped with antimony oxide, following the procedure of Example 4 of U.S. patent 3,627,669, in the fol-lowing manner:
Tin dioxide was prepared by dissolving metallic tin (84 parts) in concentrated nitric acid and heating until tin di-oxide was precipitated. Antimony trioxide (18 parts) was boiled in concentrated nitric acid until evolution of nitrogen oxides ceased, then thoroughly mixed with the precipitated tin oxide. The mixture was further treated with hot nitric acid, then washed free of acid and air dried at about 200 C. About 3 percent by weight of manganese difluoride was added and mixed with the dried mixed oxides. The mixture was then compressed into pellets, heated in air at about 800 C for 24 hours~ then crushed and reduced to a particle size of less than 60 microns.
The crushed mixed oxide composition was again pelletized and heated as before and then crushed and ball-milled to a par-ticle size of less than 5 mcirons.
An antimony trichloride-alkoxy-tin solution was prepared by boiling at reflux conditions for 24 hours a mixture of 15 parts of stannic chloride and S5 parts of n-amyl alcohol then ~5~5~i3 dissolving therein 2.13 parts of antimony trichoride.
A suspension of 0.17 parts of the mixed oxide compo-sition in 3.6 parts of the antimony trichloride-alkoxy-tin solution was prepared and painted on to the cleaned titanium surface and the coating was oven-dried at 150 C. Two addi-tional coats of the same composition were similarly applied and dried after which the coated strip was heated in air at 450 C for about 15 minutes to convert the coating substan-tially to oxides of tin and antimony with manganese fluoride.
The coating operation, including the final heating at 450 C
was repeated three times to increase the thickness of the coating.
The theoretical composition of the conductive coating thus prepared, was 85.6 percent SnO2; 13.7 percent antimony oxides ~calculated as Sb~03); and 0.7 percent MnF2. The coating weight of the finished coating was 21.2 grams per square meter.
IB. Preparation of RuO~ Coating The conductive tin oxide coated titanium was further coated in the following manner:
A solution of 1 gram of ruthenium trichloride in 0.4 cubic centimeters-of 36% hydrochloric acid and 6.2 cubic centimeters of butyl alcohol was brushed several times on to the tin oxide surface and then allowed to dry in air at room temperature. After drying, the samples were heated in air at 560 C for 25 minutes to decompose the RuC13 and form Ru02.
An additional coating of RuC13 was similarily applied, dried and thermally treated, to yield a final coating of Ru02 ~8S~
having a coating weight of about 6.0 grams of ruthenium per square meter.
In the foxegoing Example, a minor proportion of a chlorine discharge agent, manganese difluoride was incorporated in ~he conductive tin oxide coating. An anode may also be prepared in accordance with this invention, following the procedure of Example I except that no chlorine discharge agent is added.
EXAMPLE II - Chlorine Cell Test The anode, prepared as describèd in Example IB, was in-stalled and-tested as an anode in a chlorine cell having a steel cathode separated from the anode by a cationic membrane.
The anode compartment was supplied with preheated brine having a composition of about 310 g/l NaCl and pH of about 4.5. The anolyte was maintained at about 95 C. The test was conducted at a constant current density of 310 ma!cm2 (2.0 ASI). The anode exhibited a potential of 1.19 volts (v~ a saturated calomel electrode) which potential remained stable during an extended test period.
For purposes of comparison, a commercially available anode composed of a titanium substrate leaving a coating of ruthenium oxide directly on the surface thereof was installed and tested under identical conditlons. The anode exhibited a potential of 1.26 volts (v. a saturated calomel electrode).
Thus, it will be seen that an improvement in overvoltage is achieved in anodes, such as the anode of Example IB, where the outer coating of noble metal oxide is deposited on the surface of a layer of conductive tin oxide rather than directly ~L~S~5~3 on the surface of the valve metal substrate.
EXAMPLE I I I
An anode prepared in accordance with Example IB, that is, an anode consisting of a titanium substxate, an outer coating of ruthenium oxide, and an intermediate layer of conductive tin oxide, was tested in comparison with an anode prepared in accordance with Example IA, that is t an anode consisting of a titanium substrate and a coating of conductive tin oxide. The anodes were installed and tested under iden-tical conditions in a chlorine cell having a steel cathode, separated from the anode by a cationic membrane. The anode compartment was supplied with preheated brine having a con-centration of abou~ 310 grams of NaCl per liter and a pH of ~ about 4.5. The anolyte was maintained at about 95 C and the test was conducted at a constant current density of 310 ma/cm2 (2.0 ASI). The anode of Example IB exhibited an initial potential of about 1.20 ~olts (v. a saturated calomel elec-trode), the potential remaining essentially constant over a 127 hour test period. Under identical test conditions, the anode of Example IA exhibited an initial potential of about 1.52 volts (v. a saturated calomel electrode), the potential rising to 1.76 volts over the 128 hour test period.
EXAMPLE IV
A. A sample of titanium mesh was coated with a layer of conductive tin oxide following the procedure of Example IA.
B. A sample of titanium mesh coated with conductive tin oxide as described in Example IVA was further coated with ~D58S~i3 an outer layer of ruthenium dioxide following the procedure of Example IB.
The mesh anodes, prepared as described in A and B above, were installed and tested as anodes in chlorine cells wherein the electrode gap between the anode and a steel cathode was 1/8 inch, and the anode and cathode were separated by a cat-ionic membrane. The cells were operated with anolyte con-centrations ranging from ~50 to 310 grams NaCl/liter at a pH
of 4.5, and temperatures ranging from 8a C to 90 C. rrhe tests were conducted at a constant current density of 310 ma/cm2 (2.0 ASI). The anode of Example IVB exhibited an initial potential of about 1.32 v and remained substantially stable over a 60 day period of operation whereas the anode of Example IVA exhibited an intial potential of about 1.50 volts, and the potential rose gradually to about 1.90 on the 50th day of operation, then rose very rapidly on the 52nd day and achleved complete passivation on the 55th day.
EXAMPLE V
Anode plates (5" x 6") prepared in accordance with the procedures of Examples IA and IB, were installed and tested in a chlorate cell which employs two anode plates surrounded by a mild steel cathode shell. The gap between the anode and cathode was 1/8 inch. The cell was operated at a current density of 4.0 ASI and maintained at about 70 C. The electrolyte compos$tion ranged from 400 to 550 grams of NaClO3 and 120 to 150 grams NaCl and 1.0 to 1.5 grams sodium dichromate per liter and a pH of about 6.7.
5~35i63 The anode of Example IA, having an outer coating of conductive tin oxide, exhibited an initial potential of
Considerable effort has been expended in recent years in attempts to develop improved anode materials and structures utilizing the advantages of noble metals or noble metal oxides.
A great amount of effort has been directed to the development of anodes having a high operative surface area of noble metal or noble metal oxide in comparison with the total quantity of the material employed. This may be done, for example, by employing the noble metal as a thin film or coating over an electrically conductive substrate. However, when it is at-tempted to minimize the aforementioned economic disadvantage of the noble metals by applying them in the form of very thin films over a metal substrate, it has heen found that such ~S~35~3 very thin films are often porous. The result is an exposure of the substrate to the anode environment, through the pores in the outer layer. In addition, in normal use in an electro-lytic cell, a small amount of wear, spalling or flaking off of portions of the noble metal or noble metal oxide is likely to occur, resulting in urther exposure of the substrate.
Many materials, otherwise suitable for use as a substrate are susceptible to chemical attack and rapid deterioration upon exposure to the anode environment~ In an attempt to assure minimum deterioration of the substrate under such circumstances, anode manufacturers commonly utilize a valve metal such as titanium as the substrate material. Upon ex-posure to the anodic environment, ti~anium, as well as other valve metals, will form a surface layer of oxide which serves to protect the substrate from further chemical attack. The oxide thus formed, however, is not catalytically active and as a result the operative surface area of the anode is decreased.
Accordingly, it is an object of the present invention to provide improved electrodes for use as anodes in electrolytic processes. It is a further object to provide such anodes having an operative surface of noble metal or noble metal oxide and having improved efficiency and maintenance charac-teristics.
ST~TEMENT OF INVENTION
This invention provides a novel electrode, especially suited for use as an anode in chlor-alkali cells; the novel electrode comprising a valve metal substrate having a pro-tective coating of conductive tin oxide on the surface ~L~5~i563 thereof and an outer, thin layer of a noble metal or noble metal oxide. Electrodes of this type exhibit a high degree of durability in addition ~o the relatively low overvoltage characteristics of a noble metal or noble metal oxide, making them well-suited for use as anodes in the electrolytic pro-duction of chorine.
Amvng the advantages of such construction is the pro-tection afforded the metal substrate by the coating of con ductive tin oxide. The preferred substrate materials of the anodes of the invention are the valve metals, such as titanium tantalum, niobium or zirconium, especially titanium. However, where suitably thick intermediate layers of tin oxide are employed, other more conductive metals may be considered for use as substrates. The tin oxide coating, which may range in coating weight from about 0.1 grams per square meter to 100 grams per squar~ meter or more, depending on the degree of protectlon desired, prevents contact of the substrate and the electrolyte, thus preventing or minimizing corrosion or surface oxidation and the attendant deterioration or passi-vation of the substrate. At the same time, the outer layer provides the advantageous catalytic properties of the noble metals or noble metal oxides. In addition, the protective layer of conductive tin oxide permits the use of a relatively thin layer of the noble metal or noble metal oxide and a consequent savings resulting from a minimal use of the pre-cious metal. Typically, the layer of noble metal or noble metal oxide will have a coating weight in the range of about 0.1 grams per square meter to about 20 grams per square meter or higher and preferably about 3 to 10 grams per square meter ~OS8563 in thickness. The disadvantage of pores or pinholes in the noble metal layer common in extremely thin layers is obviated by the presence of ~he intermediate layer of conductive tin oxide. Pores or pinholes in the noble metal layer, or wear-ing away of that outer layer over long periods of use result in the gradual exposure of ~he tin oxide layer. The inter-mediate layer of tin oxide will continue to provide a cata-lytically active sur~ace in those exposed areas. The cata-lytic characteristics o~ tin oxide, although not as high as the noble metals or noble metal oxides, is quite substantially higher than the valve metal oxide. Thus, the overall deter-ioration of the catalytic properties of the anode is more gradual and maintenance problems are accordingly lesse~ed.
In additionr it has been found that the intermediate layer of tin oxide provides an increase in surface area of the anode with a consequent improvement in overvoltage.
It has further been found that the adhesion of the noble metal or noble metal oxide to the substrate is increased by the presence of the intermediate layer of tin oxide and the problem of spalling of the surface layer is thereby reduced.
DE5CRIPTION OF THE :PREF RRED EMBODIMENTS
The valve metal substrate which forms the inner or base component of the electrode is an electroconductive metal having sufficient mechanical strength to serve as a support for the coating and having a high degree of chemical resistivity, es-pecially to the anodic environment of electrolytic cells.
Typical valve metals include, for example, Ti, Ta, Nb, Zr, and 5~3 alloys thereof. The valve metals are well known for their tendency to form an inert oxide film upon exposure to an anodic environment. The preferred valve metal, based on cost and availability as well as electrical and chemical properties is titanium. The conductivity of the substrate may be improved, if desired, by providing a central core of a highly conductive metal such as copper. In such an arrange-mentr the core must be electrically connected to and completely protected by the valve metal substrate.
Tin oxide can be readily formed as an adherent coatiny on a valve metal substrate, in a manner described hereinafter, to provide a protective, electrically conductive layer which is especially resistant to chemical attack in anodic environ ments. Pure tin oxide however has a relatively high electrical resistivity in comparison to metals and exhibits undesireble change in electrical resistivity as a function of temper-ature. It is well known that the electrical stability of tin oxide coatings may be substantially improved and the electrical resistivity lowered through the introduction of a minor prop-ortion of a suitable inorganic material (commonly referred to as a "dopant"). A variety of materials, especially various metal oxides and other metal compounds and mixtures thereof, have been disclosed in the prior art as suitable dopants for stabilizing and lowering the electrical resistivity of tin oxide compositions. Among the materials shown in the prior art to be useful as dopants in conductive tin oxide compositions and which may be employed in the tin oxide coat-ing compositions of the anodes of this invention are included, for example, fluorine compounds, especially the metal salts 10585~;3 of fluorine, such as sodium fluoride, potassium fluoride, lithium fluoride, berylium fluoride, aluminum fluoride, lead fluoride, chromium fluoride, calcium fluoride, and other metal fluorides; hydrazine, phenylhydrazine; phos-phorus compounds such as phosphorus chloride, phosphorus oxychloride, ammoni~ phosphate, organic phosphorus esters such as tricresyl phosphate; as well as compounds of tel-luriumr tungsten, antimony, molybdenum, arsenic, and others and mixtures thereof. The conductive tin oxide coatings of this invention comprise tin oxide, preferably containing a minor amount of a suitable dopant. The preferred dopant is an antimony compound which may be added to the tin oxide coating composition either as an oxide or as a compound such as SbC13 which may form the oxide when heated in an oxidizing atmosphere. Although the exact form o the antimony in the final coatinq is not certain, it is assumed to be present as Sb2O3 and data and proportions in this specification and the appended claims are based on that assumption. The pre~erred compositions of this invention comprise mixtures of tin oxide and a minor amount of antimony oxide, the latter being present preferably in an amount of between about 0.1 and 20 weight per-cent (calculated on the basis of total weight of SnO2 and Sb203 ) .
Conductive tin oxide coatings may be adherently formed on the surface of the valve metal substrate by various methods known in the art. Typically such coatings may be formed by first chemically cleaning the substrate, for example, by degreasing and etching the surface in a suitable :~S85~;3 acid, e.g., oxalic acid, then applying a solution of appro-priate thermally decomposable salts, drying and heating in an oxidizing atmosphere. The salts that may be employed include, in general, any thermally decomposable inoxganic or organic salt or ester of tin and dopant, e.g., antimony, including for example their chlorides, alkoxides, alkoxy halides, resinates, amines and the like. Typical salts in-clude for example, stannic chloride, dibutyltin dichloride, tin tetraethoxide, antimony trichloride, antimony penta-chloride and the like. Suitable solvents include for ex-ample, ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, amyl alcohol, toluene, benzene and other organic solvents as well as water.
The solution of thermally decomposable salts, containing for example, a salt of tin and a salt of antimony, or other dopant, in the desired proportions, may be applied to the cleaned surface of the valve metal substrate by painting, brushing, dipping~ rolling, spraying or other method. The coating is then dried by heating for example at about 100 to 200 C for several minutes to evaporate the solvent, and then heating at a higher temperature, e.g., 250 to 800 C
in oxidizing atmosphere to convert the tin and antimony com-pounds to their respective oxides. The procedure may be re-peated as many times as necessary to achieve a desired coat-ing weight or thickness. The final coating weight of this conductive tin oxide coating may vary considerably, but is preferably in the range of about 3 to about 30 grams per square meter.
_ g _ ~L~S~3S63 Optionally, a small amount, such as up to 3 percent by weight of a chlorine discharge catalyst such as at least one of the difluorides of manganese, iron~ cobalt or nickel may by included in the tin oxide coating to lower the overpoten-tial required for chlorine gas liberation in a chlor-alkali cell. The chorine discharge catalyst may be added to the tin oxide coating by suspending a fine particulate preformed sinter of tin dioxide and the catalyst in the solution of thermally decomposable salts. Such chlorine discharge catalysts in the tin oxide coating is not essential to the anodes of this inven-tion but may be employed if desired in a known manner such as disclosed in U.S. patent 3,627,669.
The outer coating of the anode comprises a noble metal or noble metal oxide such as platinum, iridium, rhodium, pal-ladium ruthenium or somium or mixtures or alloys of these metals or the oxides or mixtures of the oxides of these metals.
An outer coating of a noble metal may be applied by known methods such as electroplating, chemical deposition from a platinum coating solution, spraying, or other methods.
Preferably, the outer coating of the anode comprises a noble metal oxide. Noble metal oxide coating may be applied by first depositing the noble metal in the metallic state and then oxidizing the noble metal coating, for example, by gal-vanic oxidation or chemical oxidation by means of an oxidant such as an oxidizing salt melt, or by heating to an elevated temperature, e.g., 300 C to 600 C or higher in an oxidizing atmosphere such as air oxygen, at atmospheric or superatmos-pheric pressures to convert the noble metal coating to a 5~ ;3 coating of the corresponding noble metal oxide. Other suit-able methods include, for example, electrophoretic deposition of the noble metal oxide; or application of a dispersion of the noble metal oxide in a carrier, such as alcohol, by spraying, brushing, rolling, dipping, painting, or other method on to the tin oxide surface followed by heating at an elevated temperature to evaporate the carrier and sinter the oxide coating. A preferred method for the formation of the noble metal oxide coating involves coating the conductive tin oxide surface with a solution of a noble metal compound, evaporating the solvent and converting the coating of noblP
metal compound to the oxide by chemical or electrochemical reaction. For example, the conductive tin oxide surface may be coated with a solution of a thermally decomposable salt of a noble metal, such as a solution of a noble metal halide in an alcohol, evaporation of the solvent, followed by heat-ing at an elevated temperature such as between about 300 C
and 800 C in an oxidizing atmosphere such as air or oxygen for a period of time sufficient to convert the noble metal halide to a noble metal oxide. The procedure for formation of a noble metal or noble metal oxide coating may be repeated as often as necessary to achieve the desired thickness. The foregoing and other methods for the preparation of coatings of noble metals and noble metal oxides are well known in the art and may be found for example in U.S~ patent 3,711,385.
The following specific examples will serve to further illustrate this invention. In the examples and elsewhere in this specification and claims~ all temperatures are in degrees ~5~35~;3 Celsius and all parts and percentages are by weight unless otherwise indicated.
EXAMPLE I
IA. Pre~ration of conductive tin oxide coating A strip of titanium plate was prepared by immersion in hot oxalic acid for several hours to etch the surface, then washed and dried. The titanium was then coated with a compo-sition of tin oxide doped with antimony oxide, following the procedure of Example 4 of U.S. patent 3,627,669, in the fol-lowing manner:
Tin dioxide was prepared by dissolving metallic tin (84 parts) in concentrated nitric acid and heating until tin di-oxide was precipitated. Antimony trioxide (18 parts) was boiled in concentrated nitric acid until evolution of nitrogen oxides ceased, then thoroughly mixed with the precipitated tin oxide. The mixture was further treated with hot nitric acid, then washed free of acid and air dried at about 200 C. About 3 percent by weight of manganese difluoride was added and mixed with the dried mixed oxides. The mixture was then compressed into pellets, heated in air at about 800 C for 24 hours~ then crushed and reduced to a particle size of less than 60 microns.
The crushed mixed oxide composition was again pelletized and heated as before and then crushed and ball-milled to a par-ticle size of less than 5 mcirons.
An antimony trichloride-alkoxy-tin solution was prepared by boiling at reflux conditions for 24 hours a mixture of 15 parts of stannic chloride and S5 parts of n-amyl alcohol then ~5~5~i3 dissolving therein 2.13 parts of antimony trichoride.
A suspension of 0.17 parts of the mixed oxide compo-sition in 3.6 parts of the antimony trichloride-alkoxy-tin solution was prepared and painted on to the cleaned titanium surface and the coating was oven-dried at 150 C. Two addi-tional coats of the same composition were similarly applied and dried after which the coated strip was heated in air at 450 C for about 15 minutes to convert the coating substan-tially to oxides of tin and antimony with manganese fluoride.
The coating operation, including the final heating at 450 C
was repeated three times to increase the thickness of the coating.
The theoretical composition of the conductive coating thus prepared, was 85.6 percent SnO2; 13.7 percent antimony oxides ~calculated as Sb~03); and 0.7 percent MnF2. The coating weight of the finished coating was 21.2 grams per square meter.
IB. Preparation of RuO~ Coating The conductive tin oxide coated titanium was further coated in the following manner:
A solution of 1 gram of ruthenium trichloride in 0.4 cubic centimeters-of 36% hydrochloric acid and 6.2 cubic centimeters of butyl alcohol was brushed several times on to the tin oxide surface and then allowed to dry in air at room temperature. After drying, the samples were heated in air at 560 C for 25 minutes to decompose the RuC13 and form Ru02.
An additional coating of RuC13 was similarily applied, dried and thermally treated, to yield a final coating of Ru02 ~8S~
having a coating weight of about 6.0 grams of ruthenium per square meter.
In the foxegoing Example, a minor proportion of a chlorine discharge agent, manganese difluoride was incorporated in ~he conductive tin oxide coating. An anode may also be prepared in accordance with this invention, following the procedure of Example I except that no chlorine discharge agent is added.
EXAMPLE II - Chlorine Cell Test The anode, prepared as describèd in Example IB, was in-stalled and-tested as an anode in a chlorine cell having a steel cathode separated from the anode by a cationic membrane.
The anode compartment was supplied with preheated brine having a composition of about 310 g/l NaCl and pH of about 4.5. The anolyte was maintained at about 95 C. The test was conducted at a constant current density of 310 ma!cm2 (2.0 ASI). The anode exhibited a potential of 1.19 volts (v~ a saturated calomel electrode) which potential remained stable during an extended test period.
For purposes of comparison, a commercially available anode composed of a titanium substrate leaving a coating of ruthenium oxide directly on the surface thereof was installed and tested under identical conditlons. The anode exhibited a potential of 1.26 volts (v. a saturated calomel electrode).
Thus, it will be seen that an improvement in overvoltage is achieved in anodes, such as the anode of Example IB, where the outer coating of noble metal oxide is deposited on the surface of a layer of conductive tin oxide rather than directly ~L~S~5~3 on the surface of the valve metal substrate.
EXAMPLE I I I
An anode prepared in accordance with Example IB, that is, an anode consisting of a titanium substxate, an outer coating of ruthenium oxide, and an intermediate layer of conductive tin oxide, was tested in comparison with an anode prepared in accordance with Example IA, that is t an anode consisting of a titanium substrate and a coating of conductive tin oxide. The anodes were installed and tested under iden-tical conditions in a chlorine cell having a steel cathode, separated from the anode by a cationic membrane. The anode compartment was supplied with preheated brine having a con-centration of abou~ 310 grams of NaCl per liter and a pH of ~ about 4.5. The anolyte was maintained at about 95 C and the test was conducted at a constant current density of 310 ma/cm2 (2.0 ASI). The anode of Example IB exhibited an initial potential of about 1.20 ~olts (v. a saturated calomel elec-trode), the potential remaining essentially constant over a 127 hour test period. Under identical test conditions, the anode of Example IA exhibited an initial potential of about 1.52 volts (v. a saturated calomel electrode), the potential rising to 1.76 volts over the 128 hour test period.
EXAMPLE IV
A. A sample of titanium mesh was coated with a layer of conductive tin oxide following the procedure of Example IA.
B. A sample of titanium mesh coated with conductive tin oxide as described in Example IVA was further coated with ~D58S~i3 an outer layer of ruthenium dioxide following the procedure of Example IB.
The mesh anodes, prepared as described in A and B above, were installed and tested as anodes in chlorine cells wherein the electrode gap between the anode and a steel cathode was 1/8 inch, and the anode and cathode were separated by a cat-ionic membrane. The cells were operated with anolyte con-centrations ranging from ~50 to 310 grams NaCl/liter at a pH
of 4.5, and temperatures ranging from 8a C to 90 C. rrhe tests were conducted at a constant current density of 310 ma/cm2 (2.0 ASI). The anode of Example IVB exhibited an initial potential of about 1.32 v and remained substantially stable over a 60 day period of operation whereas the anode of Example IVA exhibited an intial potential of about 1.50 volts, and the potential rose gradually to about 1.90 on the 50th day of operation, then rose very rapidly on the 52nd day and achleved complete passivation on the 55th day.
EXAMPLE V
Anode plates (5" x 6") prepared in accordance with the procedures of Examples IA and IB, were installed and tested in a chlorate cell which employs two anode plates surrounded by a mild steel cathode shell. The gap between the anode and cathode was 1/8 inch. The cell was operated at a current density of 4.0 ASI and maintained at about 70 C. The electrolyte compos$tion ranged from 400 to 550 grams of NaClO3 and 120 to 150 grams NaCl and 1.0 to 1.5 grams sodium dichromate per liter and a pH of about 6.7.
5~35i63 The anode of Example IA, having an outer coating of conductive tin oxide, exhibited an initial potential of
4.0 volts. The potential rose gradually to 5.4 volts during the first 40 hours of operation and the anode failed com-pletely in less than two days of operation~ Under identical conditions the anode of Example IB exhibited a lower initial potential (3.50 volts) and excellent stability, rising to about 4.05 volts over an operating time of 91 days.
The foregoing s~ecification is intended to illustrate ~ the invention with certain preferred embodiments, but it is understood that the details disclosed herein can be modified without departing from the spirit and scope of the invention.
The foregoing s~ecification is intended to illustrate ~ the invention with certain preferred embodiments, but it is understood that the details disclosed herein can be modified without departing from the spirit and scope of the invention.
Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
An electrolytic anode comprising a valve metal substrate, a coating thereon of conductive tin oxide, and an outer coating of at least one of a noble metal or noble metal oxide.
An electrolytic anode according to Claim 1 wherein the substrate is titanium.
An electrolytic anode according to Claim 2 wherein the conductive tin oxide comprises a mixture of tin dioxide and a minor amount of antimony oxide.
An electrolytic anode according to Claim 2 wherein the outer coating is a noble metal oxide.
An electrolytic anode according to Claim 4 wherein the outer coating is ruthenium oxide.
An electrolytic anode according to Claim 5 wherein the conductive tin oxide comprises a mixture of tin oxide and between about 0.1 and about 20 percent by weight of antimony oxide, based on the total weight of said mixture when calculated as SnO2 and Sb2O3.
In an electrolytic cell for electrolyzing aqueous alkali metal chloride solutions wherein chlorine is liberated at the anode, the improvement which comprises using as said anode a composite structure comprising a valve metal substrate, a coating of conductive tin oxide on the surface thereof, and an outer coating, on the surface of the conductive tin oxide, of at least one of a noble metal or noble metal oxide.
The cell of claim 7 wherein the anode comprises a titanium sub-strate, a coating thereon of conductive tin oxide, and an outer coating of ruthenium oxide.
A cell of claim 8 wherein the conductive tin oxide comprises a mixture of tin oxide and between about 0.1 and 20% by weight of antimony oxide, based on the total weight of the mixture when calculated as SnO2 and Sb2O3.
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
An electrolytic anode comprising a valve metal substrate, a coating thereon of conductive tin oxide, and an outer coating of at least one of a noble metal or noble metal oxide.
An electrolytic anode according to Claim 1 wherein the substrate is titanium.
An electrolytic anode according to Claim 2 wherein the conductive tin oxide comprises a mixture of tin dioxide and a minor amount of antimony oxide.
An electrolytic anode according to Claim 2 wherein the outer coating is a noble metal oxide.
An electrolytic anode according to Claim 4 wherein the outer coating is ruthenium oxide.
An electrolytic anode according to Claim 5 wherein the conductive tin oxide comprises a mixture of tin oxide and between about 0.1 and about 20 percent by weight of antimony oxide, based on the total weight of said mixture when calculated as SnO2 and Sb2O3.
In an electrolytic cell for electrolyzing aqueous alkali metal chloride solutions wherein chlorine is liberated at the anode, the improvement which comprises using as said anode a composite structure comprising a valve metal substrate, a coating of conductive tin oxide on the surface thereof, and an outer coating, on the surface of the conductive tin oxide, of at least one of a noble metal or noble metal oxide.
The cell of claim 7 wherein the anode comprises a titanium sub-strate, a coating thereon of conductive tin oxide, and an outer coating of ruthenium oxide.
A cell of claim 8 wherein the conductive tin oxide comprises a mixture of tin oxide and between about 0.1 and 20% by weight of antimony oxide, based on the total weight of the mixture when calculated as SnO2 and Sb2O3.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US494110A US3882002A (en) | 1974-08-02 | 1974-08-02 | Anode for electrolytic processes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1058563A true CA1058563A (en) | 1979-07-17 |
Family
ID=23963089
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA230,660A Expired CA1058563A (en) | 1974-08-02 | 1975-07-03 | Anode for electrolytic processes |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US3882002A (en) |
| JP (1) | JPS592753B2 (en) |
| AR (1) | AR205045A1 (en) |
| BE (1) | BE832010A (en) |
| BR (1) | BR7504830A (en) |
| CA (1) | CA1058563A (en) |
| DE (1) | DE2532553A1 (en) |
| FR (1) | FR2280718A1 (en) |
| GB (1) | GB1485884A (en) |
| IT (1) | IT1040223B (en) |
| NL (1) | NL7508764A (en) |
| SE (1) | SE7508697L (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US3986942A (en) * | 1974-08-02 | 1976-10-19 | Hooker Chemicals & Plastics Corporation | Electrolytic process and apparatus |
| US3940323A (en) * | 1974-08-02 | 1976-02-24 | Hooker Chemicals & Plastics Corporation | Anode for electrolytic processes |
| US3943042A (en) * | 1974-08-02 | 1976-03-09 | Hooker Chemicals & Plastics Corporation | Anode for electrolytic processes |
| US3956083A (en) * | 1974-08-02 | 1976-05-11 | Hooker Chemicals & Plastics Corporation | Electrochemical anode and process using the anode |
| US4028215A (en) * | 1975-12-29 | 1977-06-07 | Diamond Shamrock Corporation | Manganese dioxide electrode |
| JPS586786B2 (en) * | 1976-03-15 | 1983-02-07 | ダイヤモンド・シヤムロツク・コ−ポレ−シヨン | Improved electrode manufacturing method |
| JPS53153736U (en) * | 1977-05-11 | 1978-12-04 | ||
| US4223049A (en) * | 1978-05-23 | 1980-09-16 | Research Triangle Institute | Superficially mixed metal oxide electrodes |
| JPS5544514A (en) * | 1978-09-22 | 1980-03-28 | Permelec Electrode Ltd | Electrode for electrolysis and production thereof |
| JPS5597486A (en) * | 1979-01-21 | 1980-07-24 | Tdk Corp | Electrode for electrolysis and its manufacture |
| US4378406A (en) * | 1979-03-28 | 1983-03-29 | University Of Florida | Thin platinum films on tin oxide substrates |
| US4233148A (en) * | 1979-10-01 | 1980-11-11 | Great Lakes Carbon Corporation | Electrode composition |
| CA1175883A (en) * | 1980-06-30 | 1984-10-09 | Joseph W. Mitchell | Electrolytic printing electrode |
| JPS60184690A (en) * | 1984-03-02 | 1985-09-20 | Permelec Electrode Ltd | Durable electrode and its manufacture |
| JPS60184691A (en) * | 1984-03-02 | 1985-09-20 | Permelec Electrode Ltd | Durable electrode and its manufacture |
| IL73536A (en) * | 1984-09-13 | 1987-12-20 | Eltech Systems Corp | Composite catalytic material particularly for electrolysis electrodes,its manufacture and its use in electrolysis |
| JPS61196056A (en) * | 1985-02-26 | 1986-08-30 | 篠田 和殷 | Roof snow falling apparatus |
| JPS6233965A (en) * | 1985-04-09 | 1987-02-13 | 高口 博行 | Apparatus for conveying and removing snow |
| JPH0240690Y2 (en) * | 1985-07-04 | 1990-10-30 | ||
| JPH0312115Y2 (en) * | 1986-01-17 | 1991-03-22 | ||
| JPS62274087A (en) * | 1986-05-22 | 1987-11-28 | Permelec Electrode Ltd | Durable electrode for electrolysis and its production |
| JPS6311778A (en) * | 1986-07-01 | 1988-01-19 | 山口 肇 | Snow removing apparatus |
| US5324407A (en) * | 1989-06-30 | 1994-06-28 | Eltech Systems Corporation | Substrate of improved plasma sprayed surface morphology and its use as an electrode in an electrolytic cell |
| US5314601A (en) * | 1989-06-30 | 1994-05-24 | Eltech Systems Corporation | Electrodes of improved service life |
| JP2885913B2 (en) * | 1990-09-04 | 1999-04-26 | ペルメレック電極株式会社 | Anode for chromium plating and method for producing the same |
| US6527939B1 (en) | 1999-06-28 | 2003-03-04 | Eltech Systems Corporation | Method of producing copper foil with an anode having multiple coating layers |
| KR100407710B1 (en) * | 2001-11-08 | 2003-12-01 | (주) 테크윈 | Catalytic oxide anode manufacturing method by high temperature sintering |
| EP1620582B1 (en) * | 2003-05-07 | 2016-12-21 | De Nora Tech, Inc. | Smooth surface morphology anode coatings |
| US20070261968A1 (en) * | 2005-01-27 | 2007-11-15 | Carlson Richard C | High efficiency hypochlorite anode coating |
| GB0612094D0 (en) * | 2006-06-19 | 2006-07-26 | Clarizon Ltd | Electrode, method of manufacture and use thereof |
| CN102443818B (en) | 2010-10-08 | 2016-01-13 | 水之星公司 | Multi-layer mixed metal oxide electrode and manufacture method thereof |
| DE102010043085A1 (en) | 2010-10-28 | 2012-05-03 | Bayer Materialscience Aktiengesellschaft | Electrode for electrolytic chlorine production |
| CN102464382B (en) * | 2010-11-05 | 2013-10-23 | 同济大学 | High oxygen evolution potential and electrode preparation method for treating fluorine containing organic waste water |
| CN102689948B (en) * | 2011-03-24 | 2013-11-13 | 同济大学 | SnO2 electrode for treating fluorine-containing organic pollutants |
| ES2676493T3 (en) * | 2014-07-17 | 2018-07-20 | Industrie De Nora S.P.A. | Electrocatalytic generation of chlorine dioxide |
| US11668017B2 (en) | 2018-07-30 | 2023-06-06 | Water Star, Inc. | Current reversal tolerant multilayer material, method of making the same, use as an electrode, and use in electrochemical processes |
| CN116573728B (en) * | 2023-06-05 | 2024-04-16 | 江阴米尔克电解设备有限公司 | Preparation method of titanium anode plate for water treatment |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3616445A (en) * | 1967-12-14 | 1971-10-26 | Electronor Corp | Titanium or tantalum base electrodes with applied titanium or tantalum oxide face activated with noble metals or noble metal oxides |
| GB1244650A (en) * | 1968-10-18 | 1971-09-02 | Ici Ltd | Electrodes for electrochemical processes |
| GB1277033A (en) * | 1968-12-13 | 1972-06-07 | Ici Ltd | Electrodes for electrochemical cells |
| US3775284A (en) * | 1970-03-23 | 1973-11-27 | J Bennett | Non-passivating barrier layer electrodes |
| US3711385A (en) * | 1970-09-25 | 1973-01-16 | Chemnor Corp | Electrode having platinum metal oxide coating thereon,and method of use thereof |
| US3776834A (en) * | 1972-05-30 | 1973-12-04 | Leary K O | Partial replacement of ruthenium with tin in electrode coatings |
-
1974
- 1974-08-02 US US494110A patent/US3882002A/en not_active Expired - Lifetime
-
1975
- 1975-01-01 AR AR259713A patent/AR205045A1/en active
- 1975-07-03 CA CA230,660A patent/CA1058563A/en not_active Expired
- 1975-07-16 GB GB29900/75A patent/GB1485884A/en not_active Expired
- 1975-07-21 DE DE19752532553 patent/DE2532553A1/en not_active Withdrawn
- 1975-07-23 NL NL7508764A patent/NL7508764A/en unknown
- 1975-07-28 BR BR7504830*A patent/BR7504830A/en unknown
- 1975-07-31 IT IT25973/75A patent/IT1040223B/en active
- 1975-07-31 FR FR7523984A patent/FR2280718A1/en active Granted
- 1975-07-31 SE SE7508697A patent/SE7508697L/en unknown
- 1975-07-31 BE BE158853A patent/BE832010A/en unknown
- 1975-08-02 JP JP50094673A patent/JPS592753B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5140381A (en) | 1976-04-05 |
| BE832010A (en) | 1976-02-02 |
| BR7504830A (en) | 1976-08-03 |
| AR205045A1 (en) | 1976-03-31 |
| DE2532553A1 (en) | 1976-02-19 |
| GB1485884A (en) | 1977-09-14 |
| FR2280718A1 (en) | 1976-02-27 |
| SE7508697L (en) | 1976-02-03 |
| JPS592753B2 (en) | 1984-01-20 |
| US3882002A (en) | 1975-05-06 |
| NL7508764A (en) | 1976-02-04 |
| FR2280718B1 (en) | 1978-10-13 |
| IT1040223B (en) | 1979-12-20 |
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