Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/06—Metallic material
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/02—Pretreatment of the material to be coated
• • 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
  • C23F1/00—Etching metallic material by chemical means
• • 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
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/02—Electrodes; Connections thereof

Definitions

• a coating applied directly to a base metal is an electrocatalytic coating, often containing a precious metal from the platinum metal group, and applied directly onto a metal such as a valve metal.
• the metal may be simply cleaned to give a very smooth surface.
• U.S. Patent No, 4,797,182. Treatment with fluorine compounds may produce a smooth surfacc.
• Cleaning might include chemical degreasing, electrolytic degreasing or treatment with an oxidizing acid.
• Another procedure for anchoring the fresh coating to the substrate that has found utility in the application of an electrocatalytic coating to a valve metal, is to provide a porous oxide layer which can be formed on the base metal.
• titanium oxide can be flame or plasma sprayed onto substrate metal before application of electrochemically active substance, as disclosed in U.S. Patent No. 4,140,813.
• the thermally sprayed material may consist of a metal oxide or nitride or so forth, to which electrocatalytically active particles have been pre-applied, as taught in U.S. Patent No. 4,392,927.
• the coated metal substrate can have highly desirable extended lifetime even in most rigorous industrial environments.
• the invention can provide for well anchored coatings of uniform planarity, even when utilizing gouged and similarly disfigured substrate metal.
• the invention is directed to a method of producing a metallic article comprising a substrate having a metal-containing surface adapted for enhanced coating adhesion by melt spraying valve metal particles having a size within the range from 20 to 100 micrometers to produce a surface having a profilometer-measured average surface roughness of about 6.35 micrometers (about 250 microinches), or more, and an average surface peaks per cm of about 15.7 (about 40 peaks per inch), or more, basis a profilometer upper threshold limit of 10.16 micrometers (400 microinches) and a profilometer lower threshold limit of 7.62 micrometers (300 microinches).
• the invention is directed to the method of preparing a metal surface for enhanced coating adhesion which surface has been gouged and thereby exhibits loss of planarity, which method comprises: plasma spraying the gouges of such surface with a valve metal to establish metal surface planarity, and then plasma spraying the surface to be coated, including the plasma sprayed gouges to provide a surface roughness of enhanced coating adhesion, as defined above.
• the invention is directed to a metallic article coated with an intermediate layer and an electrochemically active surface coating, particularly for use as an electrode in electrochemical processes.
• the metal articles are electrocatalytically coated and used as oxygen evolving electrodes, even under the rigorous commercial operations including continuous electrogalvanizing, electrotinning, copper foil plating, electroforming or electrowinning, and including sodium sulfate electrolysis such electrodes can have highly desirable service life.
• the invention is also directed to such metal articles as are utilized as electrodes.
• the metals of the substrate are broadly contemplated to be any coatable metal.
• the substrate metals might be such as nickel or manganese, but will most always be valve metals, including titanium, tantalum, aluminum, zirconium and niobium. Of particular interest for its ruggedness, corrosion resistance and availability is titanium.
• the suitable metals of the substrate can include metal alloys and intermetallic mixtures, as well as ceramics and cermets such as contain one or more valve metals.
• titanium may be alloyed with nickel, cobalt, iron, manganese or copper.
• Grade 5 titanium may include up to 6.75 weight% aluminum and 4.5 weight% vanadium, grade 6 up to 6% aluminum and 3% tin, grade 7 up to 0.25 weight% palladium, grade 10, from 10 to 13 weight% molybdenum plus 4.5 to 7.5 weight% zirconium and so on.
• metals in their normally available condition, i.e., having minor amounts of impurities.
• metal of particular interest i.e., titanium
• various grades of the metal are available including those in which other constituents may be alloys or alloys plus impurities. Grades of titanium have been more specifically set forth in the standard specifications for titanium detailed in ASTM B 265-79.
• the substrate metal advantageously is a cleaned surface. This may be obtained by any of the treatments used to achieve a clean metal surface, but with the provision that unless called for to remove an old coating, and if etching might be employed, as more specifically detailed hereinbelow, mechanical cleaning is typically minimized. Thus the usual cleaning procedures of degreasing, either chemical or electrolytic, or other chemical cleaning operation may be used to advantage.
• plasma spraying the metal is melted and sprayed in a plasma stream generated by heating with an electric arc to high temperatures an inert gas, such as argon or nitrogen, optionally containing a minor amount of hydrogen.
• inert gas such as argon or nitrogen
• the spraying parameters such as the volume and temperature of the flame or plasma spraying stream, the spraying distance, the feed rate of particulate metal constituents and the like, are chosen so that the particulate metal components are melted by and in the spray stream and deposited on the metal substrate while still substantially in melted form so as to provide an essentially continuous coating (i.e. one in which the sprayed particles are not discernible) having a foraminous structure.
• spray parameters like those used in the examples give satisfactory coatings.
• the metal substrate during melt spraying is maintained near ambient temperature. This may be achieved by means such as streams of air impinging on the substrate during spraying or allowing the substrate to air cool between spray passes.
• the particulate metal employed e.g., titanium powder
• the metallic constituency of the particulates may be as above-described for the metals of the substrate, e.g., the titanium might be one of several grades most usually grade 1 titanium. It is also contemplated that mixtures may be applied, e.g., mixtures of metals or of metals with other subsituents, which can include metal oxides, for example a predominant amount of metal with a minor amount of other substituents.
• plasma spray applications may be used in combination with etching of the substrate metal surface, with each treatment most always being applied to different portions of a surface. If etching is used, it is important to aggressively etch the metal surface to provide deep grain boundaries and well exposed, three-dimensional grains. It is preferred that such operation will etch impurities located at such grain boundaries.
• the metal article can be disfigured and can have lost surface planarity.
• disfiguring will be in nicks and gouges of the surface.
• all such surface disfigurement, including nicks, scrapes, and gouges, and burns where metal may actually be melted and resolidify will generally be referred to herein simply as "gouges.”
• gouges may or may not be filled with a metal filling. If the overall surface were to be subsequently etched before recoating, the filled zones can be expected to yield poor etch results.
• gouging of the substrate may be extensive, or the substrate from its heat history and/or chemistry may not achieve desirable results in etching. It may, therefore, be especially desirable to simply plasma spray the entire surface which can overcome these substrate deficiencies. It is also contemplated that it may be useful to combine plasma spray application with etching in some situations.
• gouges and the like may be filled by plasma spray technique. Usually, the areas of the surface which are not disfigured will first be etched, then the planar, etched areas can be masked, and the gouges remaining will be filled and/or surface treated by plasma spray application. That is, plasma spray can be used to fill and reactivate a gouge, or it simply can be used to just reactivate gouges without necessarily restoring surface planarity. By reactivation is meant the plasma spray application to prepare the gouge for subsequent treatment. Hence, the entire surface will have the needed roughness for coating, and if desired it may in the same processing be refurbished to desirable planarity.
• the heat treatment history of the metal can be important.
• a metal such as titanium for etching
• annealing proper annealing of grade 1 titanium will enhance the concentration of the iron impurity at grain boundaries.
• the suitable preparation includes annealing, and the metal is grade 1 titanium
• the titanium can be annealed at a temperature of at least about 500°C. for a time of at least about 15 minutes.
• a more elevated annealing temperature e.g., 600°-800°C. is advantageous.
• etching it will be with a sufficiently active etch solution to develop aggressive grain boundary attack.
• Typical etch solutions are acidic solutions. These can be provided by hydrochloric, sulfuric, perchloric, nitric, oxalic, tartaric, and phosphoric acids as well as mixtures thereof, e.g., aqua regia.
• Other etchants that may be utilized include caustic etchants such as a solution of potassium hydroxide/hydrogen peroxide in combination, or a melt of potassium hydroxide with potassium nitrate.
• the etch solution is advantageously a strong, or concentrated solution such as an 18-22 weight% solution of hydrochloric acid.
• the solution is advantageously maintained during etching at elevated temperature such as at 80°C. or more for aqueous solutions, and often at or near boiling condition or greater, e.g., under refluxing condition.
• elevated temperature such as at 80°C. or more for aqueous solutions, and often at or near boiling condition or greater, e.g., under refluxing condition.
• the etched metal surface can then be subjected to rinsing and drying steps to prepare the surface for coating.
• a more detailed discussion of the etching and annealing can be found in EP-A-0 407 349.
• the metal surface For the plasma spray applied surface roughness, it is necessary that the metal surface have an average roughness (Ra) about 6.35 micrometers (about 250 microinches), or more, and an average number of surface peaks per cm (Nr) of at least about 15.7 (about 40 peaks per inch).
• the surface peaks per cm can be typically measured at a lower threshold limit of 7.62 micrometers (300 microinches) and an upper threshold limit of 10.16 micrometers (400 microinches).
• a surface having an average roughness of below about 6.35 micrometers (about 250 microinches) will be undesirably smooth, as will a surface having an average number of surface peaks per cm of below about 15.7 (about 40 peaks per inch) for providing the needed, substantially enhanced, coating adhesion.
• the surface will have an average roughness of on the order of about 10.16 micrometers (about 400 microinches) or more, e.g., ranging up to about 19-38.1 micrometers (about 750-1500 microinches), with no low spots of less than about 5.08 micrometers (about 200 microinches).
• the surface will be free from low spots that are less than about 5.33 to 5.59 micrometers (about 210 to 220 microinches). It is preferable that the surface have an average roughness of from about 7.62 to 12.7 micrometers (about 300 to about 500 microinches).
• the surface has an average number of peaks per cm of at least about 23.25 (about 60 peaks per inch), but which might be on the order of as great as about 130 or more, with an average from about 80 to about 120 being preferred. It is further advantageous for the surface to have an average distance between the maximum peak and the maximum valley (Rm) of at least about 25.37 ⁇ m (1,000 microinches) and to have an average peak height (Rz) of at least about 25.37 ⁇ m (1,000 microinches). All of such foregoing surface characteristics are as measured by a profilometer.
• the surface for coating will have an Rm value of at least about 38.1 ⁇ m (1,500 microinches) to about 53.34 ⁇ m (3500 microinches) and have a maximum valley characteristic of at least about 38.1 ⁇ m (1,500 microinches) up to about 53.34 ⁇ m (3500 microinches).
• the surface may then proceed through various operations, including pretreatment before coating.
• the surface may be subjected to a cleaning operation, e.g., a solvent wash.
• a subsequent etching or hydriding or nitriding treatment Prior to coating with an electrochemically active material, it has been proposed to provide an oxide layer by heating the substrate in air or by anodic oxidation of the substrate as described in U.S. Patent No. 3,234,110.
• European patent application No. 0,090,425 proposes to platinum electroplate the substrate to which then an oxide of ruthenium, palladium or iridium is chemideposited.
• electrochemically active coatings that may then be applied to the etched surface of the metal, are those provided from platinum or other platinum group metals or they can be represented by active oxide coatings such as platinum group metal oxides, magnetite , ferrite, cobalt spinel or mixed metal oxide coatings.
• active oxide coatings such as platinum group metal oxides, magnetite , ferrite, cobalt spinel or mixed metal oxide coatings.
• Such coatings have typically been developed for use as anode coatings in the industrial electrochemical industry. They may be water based or solvent based, e.g., using alcohol solvent. Suitable coatings of this type have been generally described in one or more of the U.S. Patent Nos. 3,265,526, 3,632,498, 3,711,385 and 4,528,084.
• the mixed metal oxide coatings can often include at least one oxide of a valve metal with an oxide of a platinum group metal including platinum, palladium, rhodium, iridium and ruthenium or mixtures of themselves and with other metals.
• Further coatings in addition to those enumerated above include manganese dioxide, lead dioxide, platinate coatings such as M x Pt 3 O 4 where M is an alkali metal and X is typically targeted at approximately 0.5, nickel-nickel oxide and nickel plus lanthanide oxides.
• coatings will be applied to the metal by any of those means which are useful for applying a liquid coating composition to a metal substrate. Such methods include dip spin and dip drain techniques, brush application, roller coating and spray application such as electrostatic spray. Moreover spray application and combination techniques, e.g., dip drain with spray application can be utilized. With the above-mentioned coating compositions for providing an electrochemically active coating, a modified dip drain operation can be most serviceable. Following any of the foregoing coating procedures, upon removal from the liquid coating composition, the coated metal surface may simply dip drain or be subjected to other post coating technique such as forced air drying.
• Typical curing conditions for electrocatalytic coatings can include cure temperatures of from about 300°C. up to about 600°C. Curing times may vary from only a few minutes for each coating layer up to an hour or more, e.g., a longer cure time after several coating layers have been applied. However, cure procedures duplicating annealing conditions of elevated temperature plus prolonged exposure to such elevated temperature, are generally avoided for economy of operation.
• the curing technique employed can be any of those that may be used for curing a coating on a metal substrate.
• oven curing including conveyor ovens may be utilized.
• infrared cure techniques can be useful.
• oven curing is used and the cure temperature used for electrocatalytic coatings will be within the range of from about 450°C. to about 550°C. At such temperatures, curing times of only a few minutes, e.g., from about 3 to 10 minutes, will most always be used for each applied coating layer.
• a titanium nut is welded to the back of each sample plate having an approximate 7.5 cm 2 sample face and each being unalloyed grade 1 titanium.
• the sample plates were then mounted to a large back plate to provide a mosaic of sample plates. This mounting scheme served to provide a large array of sample plates which could be handled as a unit in ensuing operations.
• the sample plates were grit blasted with aluminum oxide, then rinsed in acetone and dried.
• a coating on the sample plates of titanium powder was produced using a powder having average particle size of 50 - 60 ⁇ m (microns).
• the sample plates were coated with this powder using a Metco plasma spray gun equipped with a GH spray nozzle.
• the spraying conditions were: a current of 500 amps; a voltage of 45 - 50 volts; a plasma gas consisting of argon and helium; a titanium feed rate of 1.36 kg (3 pounds) per hour; a spray bandwidth of 6.7 millimeters (mm); and a spraying distance of 64 mm, with the resulting titanium layer on the titanium sample plates having a thickness of about 150 micrometers.
• the coated surface of the sample plates were then subjected to surface prolifilometer measurement using a Hommel model T1000 C instrument manufactured by Hommelwerk GmbH.
• the plate surface profilometer measurements were determined from three separate measurements conducted by running the instrument in random orientation across the coated flat face of the plate. This gave average values as measured on three sample plates for surface roughness (Ra) of 11.38, 12.45 and 13.9 micrometers (448, 490 and 548 microinches), respectively for the three plates, and peaks per cm (Nr) of 29.8, 24.7 and 29.8 (76, 63 and 76 peaks per inch), respectively for the three plates.
• the peaks per cm were measured within the threshold limits of 7.62 micrometers (300 microinches) (lower) and 10.16 micrometers (400 microinches) (upper).
• the sample then received a coating of plasma spray applied titanium using the titanium powder and the application procedure as described in Example 1. Under profilometer measurement conducted in the manner of Example 1, the resulting average values for a flat surface of the sample were found to be 650 (Ra) and 69 (Nr).

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• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• Plasma & Fusion (AREA)
• Physics & Mathematics (AREA)
• General Chemical & Material Sciences (AREA)
• Coating By Spraying Or Casting (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Electrolytic Production Of Metals (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
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• 1991
  • 1991-12-03 TW TW080109498A patent/TW197475B/zh active
  • 1991-12-04 CA CA002056943A patent/CA2056943C/en not_active Expired - Fee Related
  • 1991-12-11 MX MX9102511A patent/MX9102511A/es unknown
  • 1991-12-20 DE DE69126656T patent/DE69126656T2/de not_active Expired - Lifetime
  • 1991-12-20 AU AU89954/91A patent/AU643350B2/en not_active Ceased
  • 1991-12-20 AT AT91810992T patent/ATE154834T1/de not_active IP Right Cessation
  • 1991-12-20 EP EP91810992A patent/EP0493326B1/en not_active Expired - Lifetime
  • 1991-12-20 DK DK91810992.7T patent/DK0493326T3/da active
  • 1991-12-20 ES ES91810992T patent/ES2104684T3/es not_active Expired - Lifetime
  • 1991-12-26 JP JP3344634A patent/JP2825383B2/ja not_active Expired - Lifetime
  • 1991-12-26 KR KR1019910024456A patent/KR100235378B1/ko not_active Expired - Lifetime
• 1997
  • 1997-09-10 GR GR970402323T patent/GR3024677T3/el unknown

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