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
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F3/00—Electrolytic etching or polishing
• • 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
  • 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
  • C23F1/10—Etching compositions
  • C23F1/14—Aqueous compositions
  • C23F1/16—Acidic compositions
  • C23F1/26—Acidic compositions for etching refractory metals
• • 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.
• Treatment with fluorine compounds may produce a smooth surface.
• Cleaning might include chemical degreasing, electrolytic degreasing or treatment with an oxidizing acid.
• the metal can be treated for coating removal.
• such treatment may be with a melt containing a basic material used in the presence of an oxidant or oxygen. Such can be followed by pickling to reconstitute the original surface for coating.
• a molten alkali metal hydroxide bath is used containing an alkali metal hydride, this is preferably followed by a hot mineral acid treatment.
• U.S. Patent No. 3,706,600 It has also been Proposed to prepare the surface without stripping the old Coating.
• U.S. Patent No. 3,684,543 More recently, this procedure has been improved by activation of the 01d coating, prior to application of the new.
• 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.
• the invention may provide for lower effective current densities and also achieve substrate metal grains desirably stabilized against passivation.
• the invention is directed to a metal article having a surface adapted for enhanced coating adhesion, such surface being free from deleterious affects of abrasive treatment while having desirable surface grain size, which surface has three-dimensional grains with deep grain boundaries, such surface having been etched including the etching of impurities located in the grain boundaries at the surface of the metal, which intergranular etching provides a profilometer-measured average surface roughness of at least about 250 microinches and an average surface peaks per inch of at least about 40, basis a profilometer upper threshold limit of 400 microinches and a profilometer lower threshold limit of 300 microinches.
• the invention is directed to a metal article having a surface adapted for enhanced coating adhesion, said surface having, as measured by profilometer, an average roughness of at least about 250 microinches and an average surface peaks per inch of at least about 40, basis the lower and upper threshold limits mentioned hereinbefore.
• Such surface most desirably also has an average distance between the maximum peak and the maximum valley of at least about 1,000 microinches and an average peak height of at least about 1,000 microinches.
• such electrodes can have highly desirable service life.
• metals as electrodes may provide an effectively lower current density, which will aid in prolonging the life of the electrode, when used as above discussed or, for example, in water or brine electrolysis.
• 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.
• 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.
• iron may be a usual impurity. Its maximum concentration can be expected to vary from 0.2 weight percent for grades 1 and 11 up to 0.5% for grades 4 and 6. Additional impurities that may be found throughout the grades of titanium include nitrogen, carbon, hydrogen and oxygen.
• beta-titanium located at the titanium grain boundaries can be susceptible to etching, such beta-titanium is considered herein for purposes of this discussion as an impurity.
• etching of an impurity as discussed herein may include etching of a phase of the metal itself.
• the titanium metal of particular interest may have beta-phase stabilizers, some of which may be present in extremely minor amounts in the manner of an impurity and include vanadium, niobium, tantalum, molybdenum, ruthenium, zirconium, tin, hafnium and mixtures thereof.
• 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, mechanical cleaning is typically minimized and preferably avoided. Thus the usual cleaning procedures of degreasing, either chemical or electrolytic, or other chemical cleaning operation may be used to advantage.
• etching it is important to aggressively etch the metal surface to provide deep grain boundaries providing well exposed, three-dimensional grains. It is preferred that such operation will etch impurities located at such grain boundaries.
• a metal having etchable grain boundary impurities may be referred to herein as a metal having a correct "metallurgy”.
• an important aspect of the invention involves the enhancement of impurities of the metal at the grain boundaries. This is advantageously done at an early stage of the overall process of metal preparation.
• One manner of this enhancement that is contemplated is the inducement at, or introduction to, the grain-boundaries of one or more impurities for the metal.
• the impurities of the metal might include iron, nitrogen, carbon, hydrogen, oxygen, and beta-titanium.
• impurities introduction procedures that might be used can include surface deposition, e.g., vapor deposition, which might be followed by a heat treatment for surface impurity diffusion
• one particular manner contemplated for impurity enhancement is to subject the titanium metal to a hydrogen-containing treatment. This can be accomplished by exposing the metal to a hydrogen atmosphere at elevated temperature. Or the metal might be subjected to an electrochemical hydrogen treatment, with the metal as a cathode in a suitable electrolyte evolving hydrogen at the cathode.
• etching Another consideration for the aspect of the invention involving etching, which aspect can lead to impurity enhancement at the grain boundaries, involves the heat treatment history of the metal.
• a metal such as titanium
• 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.
• Annealing times at such more elevated temperatures will typically be on the order of 15 minutes to 4 hours.
• a short, high temperature anneal e.g., on the order of 800°C. for a few minutes such as 5-10 minutes, may be continued, after rapid or slow cooling, at a quite low temperature, with 200°-400°C. being representative, for several hours, with 10-20 hours being typical.
• Suitable conditions can include annealing in air, or under vacuum, or with an inert gas such as argon.
• Subsequent cooling of the annealed metal can appropriately stabilize the grain boundaries for etching. Stabilization may be achieved by controlled or rapid cooling of the metal or by other usual metal cooling technique including quenching,
• a metal having such stabilization may be referred to herein as a metal having a desirable "heat history".
• a metal surface having a correct grain boundary metallurgy as above-discussed with an advantageous grain size.
• a metal surface having a correct grain boundary metallurgy as above-discussed with an advantageous grain size.
• at least a substantial amount of the grains having grain size within the range of from about 3 to about 7 is advantageous.
• Grain size as referred to herein is in accordance with the designation provided in ASTM E 112-84. Size for titanium grains below about 3 produce a high percentage of brad grains which detract from advantageous coating adhesion. Grain sizes above about 7 are not desired for best three-dimensional grain structure development.
• the grains will have size within the range from about 4 to about 6.
• the metal surface is then ready for continuing operation.
• etching it will be with a sufficiently active etch solution to develop aggressive grain boundary attack.
• Typical etch solutions are acid solution. These can be provided by hydrochloric, sulfuric, perchloric, nitric oxalic, tartaric, and phosphoric acids as well as mixtures thereof, e.g., aqua regia.
• 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.
• the etched metal surface can then be subjected to rinsing and drying steps to prepare the surface for coating.
• the metal surface have an average roughness (Ra) of at least about 250 microinches and an average number of surface peaks per inch (Nr) of at least about 40.
• the surface peaks per inch can be typically measured at a lower threshold limit of 300 microinches and an upper threshold limit of 400 microinches.
• a surface having an average roughness of below about 250 microinches will be undesirably smooth. as will a surface having an average number of surface peaks per inch of below about 40., for providing the needed, substantially enhanced, coating adhesion.
• Ra average roughness
• Nr average number of surface peaks per inch
• the surface will have an average roughness of on the order of about 250 microinches or more, e.g., ranging up to about 750-1500 microinches, with no low spots of less than about 200 microinches.
• the surface will be free from low spots that are less than about 210 to 220 microinches. It is preferable that the surface have an average roughness of from about 300 to about 500 microinches.
• the surface has an average number of peaks per inch of at least about 60, 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.
• the surface prefferably has an average distance between the maximum peak and the maximum valley (Rm) of at least about 1,000 microinches and to have an average peak height (Rz) of at least about 1,000 microinches. All of such foregoing surface characteristics are as measured by a profilometer. More desirably, the surface for coating will have an Rm value of at least about 1,500 microinches to about 3500 microinches and have a maximum valley characteristic of at least about 1,500 microinches up to about 3500 microinches.
• 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.
• 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.
• titanium plate measuring 2 inches by 6 inches by 3/8 inch and being an unalloyed grade 1 titanium, as determined in accordance with the specifications of ASTM B 265-79. This titanium sheet thus contained 0.20 Percent, maximum, iron impurity.
• This plate which was a fresh grade 1 titanium plate, was degreased in perchloroethylene vapors, rinsed with deionized water and air dried. It was then etched for approximately 1 hour by immersion in 20 weight percent hydrochloric acid aqueous solution heated to 95°C. After removal from the hot hydrochloric acid, the plate was again rinsed with deionized water and air dried. By this etching, the plate achieves a weight loss of 500-600 grams per square meter of plate surface area. This weight loss is determined by pre and post etching weighing of the plate sample and then calculating the loss per square meter by straight forward calculation on the basis of the surface area of both large flat faces of the plate.
• the surface structure of the sample plate, on both broad surfaces, is then examined under a stereo microscope under magnification varying during the study from 40X to 60X.
• Such plate surface can be seen to have a well defined, three dimensional, grain boundary etch.
• the etched surface was then subjected to surface profilometer measurement using a Hommel model T1000 C instrument manufactured by Hommelwerk GmbH.
• the plate surface profilometer measurements as average values computed from eight separate measurements conducted by running the instrument in random orientation across on large flat face of the plate. This gave average values for surface roughness (Ra) of 393 microinches, peaks per inch (Nr) of 86 and an average distance between the maximum peak and the maximum valley (Rz) of 2104.
• the peaks per inch were measured within the threshold limits of 300 microinches (lower) and 400 microinches (upper).
• a second sample plate from the same batch of unalloyed titanium as was used for the plate sample of Comparative Example 2 was subjected to annealing operation. In this operation, the sample was placed in an oven and the oven was heated until the air temperature reached 700°C. This air temperature was then held for 15 minutes, cooled to 450°C., and held for 30 minutes. Thereafter, while the sample was maintained in the oven, the oven air temperature was permitted to cool to about 200°C in a period of 1.5 hours. The sample was then removed for cooling to room temperature.
• Example 1 The resulting test sample was then etched in boiling 18 weight percent HCl for one hour, then rinsed and dried as described in Example 1. Subsequently, under visual examination in the manner of Example 1, the etched sample plate was seen to have a highly desirable, three dimensional grain boundary etch. This was confirmed by profilometer measurements which provided average values of 398 (Ra), 76 (Nr) and 2040 (Rz).
• the resulting sample was tested as an anode in an electrolyte that was a mixture of 285 grams per liter (g/l) of sodium sulfate and 60 g/l of magnesium sulfate.
• the test cell was maintained at 65°C and operated at a current density of 15 kiloamps per square meter (kA/m2).
• the coated titanium plate anode was removed from the electrolyte, rinsed in deionized water, air dried and then cooled to ambient temperature. There was then applied to the coated plate surface, by firmly manually pressing onto the coating, a strip of self-adhesive, pressure sensitive tape. This tape was then removed from the surface by quickly pulling the tape away from the plate. After 3000 hours of operation, including approximately 18 tape tests, the coated anode continued to exhibit excellent coating adhesion to the underlying titanium substrate.
• a sample of 2 mm thick, grade 1 titanium sheet was etched in 20% HCl at 90-95°C. After etching, the profilimeter measurements were found to be 124 (Ra), 12 (Nr) and 765 (Rz).
• a coating was applied to the etched sheet as described in Example 3.
• a sample of the sheet was tested in the electrolyte and under the conditions as described in Example 3. After 424 hours of operation, a tape test was performed on the sample resulting in the nearly complete removal of the coating from the tested area, exposing the underlying substrate and effectively terminating the testing.
• Example 1 A sample of titanium which had been previously coated with an electrochemically active coating, was blasted with alumina powder to remove the previous coating. By this abrasive method, it was determined by X-­ray fluoroescence that the previous coating had been removed. After removal of any residue of the abrasive treatment, the resulting sample plate was etched in the composition of Example 1 in the manner of Example 1. Under visual inspection as described in Example 1, it was seen that there was no evidence of desirable grain boundary etching. Furthermore, under profilometer measurement, the resulting average values were found to be 137 (Ra), 12 (Nr) and 841 (Rz).
• Example 3 The sample was nevertheless coated with the electrocatalytic coating of Example 3 in the manner as described in Example 3 and utilized as an anode also in the manner as described in Example 3. After 91 hours of operation, the sample was removed and the coating adhesion tested utilizing the tape test of Example 3. In this test, and after only the 91 hours of testing, the tape removed the majority of the coating exposing the underlying substrate and thus terminating further testing.
• coated metal electrodes especially coated titanium electrodes used as oxygen evolving anodes in high speed electrogalvanizing, electrotinning, electroforming or electrowinning
• the performance of coated titanium anodes is particularly erratic because the characteristics of the titanium vary substantially from one production batch to another and from one titanium sheet to another because of different heat histories and handling. This applies even to different specimens of titanium from the same batch. It was thus not possible to reliably predict anode performance based solely on careful control of the production conditions because the same etching/annealing procedure could lead to different results for different specimens.
• the invention is based on the insight that the failure mechanism of such electrodes was related to the surface morphology of the substrates. It was found that satisfactory electrodes were those whose substrate surface before coating conformed to the aforementioned specification. Electrodes made with substrates which did not meet up to this specification tended to fail prematurely. It follows that by employing the described inspection procedures it is possible to control whether or not the surface has achieved an optimum condition for receiving a coating so that when the surface is coated the risk of premature failure is practically completely eliminated.
• the intergranularly etched surface is then inspected by profilometer to determine whether the three-dimensional grains having deep grain boundaries correspond across the surface to a profilometer-measured average surface roughness (Ra) of at least about 250 microinches (about 635 micrometers), and an average surface peaks per inch (Nr) of at least about 40 (about 15.15 peaks per cm) based on a profilometer upper threshold limit of 400 microinches (1016 micrometers) and a profilometer lower threshold limit of 300 microinches (792 micrometers). If after the optical or profilometer inspection the surface does not meet said specifications, the surface may be subjected to further strong acid or strong caustic etching and to optical and/or profilometer inspection again after the further treatment.
• Ra surface roughness
• Nr average surface peaks per inch
• another substrate from the same batch may be subjected to annealing (different to the annealing of the first substrate) followed by etching and inspection, with further etching and inspection if necessary.
• annealing different to the annealing of the first substrate
• etching and inspection with further etching and inspection if necessary.
• the electrocatalytic coating is applied to the treated metal surface, but only after optical and profilometer inspection has revealed that the surface meets said specifications.
• the electrocatalytic coating can be applied directly or it is possible to perform a final "clean up" etch to present a stain-free chemically clean surface for coating, for example by etching for up to 5 minutes in fresh hot hydrochloric acid, followed by rinsing and drying.
• the optical inspection by microscope should scan the entire surface to be coated to ensure that the three-­dimensional grain boundaries extend over the entire surface.
• Profilometer measurements can be carried out at selected points across the surface. To reduce the number of profilometer measurements, it is convenient to measure with settings above the minimum values given.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
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• Electrochemistry (AREA)
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• Plasma & Fusion (AREA)
• General Chemical & Material Sciences (AREA)
• ing And Chemical Polishing (AREA)
• Chemically Coating (AREA)
• Electrolytic Production Of Metals (AREA)
• Secondary Cells (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Laminated Bodies (AREA)
• Electroplating Methods And Accessories (AREA)

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• 1990
  • 1990-06-05 TW TW079104580A patent/TW214570B/zh active
  • 1990-06-11 CA CA002018670A patent/CA2018670A1/fr not_active Abandoned
  • 1990-06-28 AT AT90810492T patent/ATE122735T1/de not_active IP Right Cessation
  • 1990-06-28 DE DE69019424T patent/DE69019424T2/de not_active Expired - Fee Related
  • 1990-06-28 EP EP90810492A patent/EP0407349B1/fr not_active Expired - Lifetime
  • 1990-06-28 ES ES90810492T patent/ES2071803T3/es not_active Expired - Lifetime
  • 1990-06-29 AU AU58041/90A patent/AU632591B2/en not_active Ceased
  • 1990-06-29 KR KR1019900009758A patent/KR100196661B1/ko not_active IP Right Cessation
  • 1990-06-29 JP JP2174335A patent/JP2721739B2/ja not_active Expired - Fee Related
  • 1990-06-29 NO NO90902922A patent/NO902922L/no unknown
  • 1990-06-29 BR BR909003037A patent/BR9003037A/pt not_active IP Right Cessation
• 1995
  • 1995-08-02 GR GR950402135T patent/GR3017014T3/el unknown

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