US3761313A - Stripping of coated titanium electrodes - Google Patents

Stripping of coated titanium electrodes Download PDF

Info

Publication number
US3761313A
US3761313A US00147608A US14760871A US3761313A US 3761313 A US3761313 A US 3761313A US 00147608 A US00147608 A US 00147608A US 14760871 A US14760871 A US 14760871A US 3761313 A US3761313 A US 3761313A
Authority
US
United States
Prior art keywords
coating
titanium
stripping
acid
electrodes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00147608A
Other languages
English (en)
Inventor
J Entwisle
K Moss
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Imperial Chemical Industries Ltd
Original Assignee
Imperial Chemical Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Imperial Chemical Industries Ltd filed Critical Imperial Chemical Industries Ltd
Application granted granted Critical
Publication of US3761313A publication Critical patent/US3761313A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/10—Other heavy metals
    • C23G1/106—Other heavy metals refractory metals

Definitions

  • the present invention relates to stripping of coated titanium electrodes for .re-coat-ing. More particularly it relates to a method for the removal'of a coating compris- "ing one or more platinum metal oxides from a titanium support which carries the coating, in'a manner which renders the titanium surface suitable for re-coating and without excessive loss oftitanium fromthe support.
  • Electrodes particularly as anodes in cells electrolysing aqueous solutions of alkali metal chloride, a combination of a filmforming metal support and a .coating thereon comprising oxides of one or more of the platinum group metals in admixture with an oxide of a film-forming metal.
  • a film-forming metal support and a .coating thereon comprising oxides of one or more of the platinum group metals in admixture with an oxide of a film-forming metal.
  • the film-forming metal of both the support and the oxide coating mixture is most suitably titanium.
  • Electrodes of the aforesaid type have advantages over prior art electrodes when empolyed as anodes in the electrolysis of alkali metal chloride solution in that they have both low chlorine overpotential characteristics and high resistance to electrochemical attack in use.
  • the electrodes have avery low wear rate in the cell, their useful lives are not infinite and in time they must be replaced or re-coated in order to maintain optimum performance. When the electrodes are taken out of service they still retain an appreciable amount of the original coating and this must be removed if the titanium support is to be used as a support for a new coating. This presents the problem of removing the old coating cheaply and easily without at the same time removing an unacceptable amount of titanium metal from the support. Also, the method used for removing the old coating should desirably leave the surface of the titanium support in a suitable condition for re-coating without (further treatments, such as the conventional etching treatments, which necessarily remove further amounts of titanium metal.
  • the present invention provides a solution to these problems of stripping oxide-coated titanium electrodes of the aforesaid type.
  • a method for stripping the coating from an electrode comprising a titanium support and a coating comprising a platinum metal oxide thereon which comprises immersing the electrode in an aqueous mixture comprising at least one strong 3,761,313 Patented Sept. 25, 1973 mineral acid, other than nitric acid, with hydrofluoric acid and/or a precursor compound that will react with the mineral acid to give hydrofluoric acid, at a temperature and for a time sufiicient for the coating to become detached from the titanium support.
  • the preferred mineral acid is hydrochloric acid or sulphuric acid.
  • hydrochloric acid When hydrochloric acid is used it is preferably such that it comprises 20% to 40% hydrogen chloride by weight of the total of hydrogen chloride and water.
  • sulphuric acid When sulphuric acid is used it is preferably 25%. to 100% by weight of the total of sulphuric acid and Water.
  • the hydrofluoric acid is preferably present in a concentration of 0.01% to 8% hydrogen fluoride by weight of the mixture, particularly 0.02% to 4%. If a compound is used instead to react with the hydrochloric or sulphuric acid to give the hydrofluoric acid its concentration should be such that it will give the desired hydrofluoric acid concentration.
  • the precursor is a fluoride which is preferably soluble in hydrochloric or sulphuric acid. Examples of such compounds include ammonium fluoride which is particularly preferred and alkali metal fluorides, e.g. sodium or potassium fluoride.
  • the temperature of the mixture in which the stripping is carried out may be for example from 25 C. to 100 C., preferably 60 C. to 100 C.
  • the time of immersion is not critical but generally the immersion need be no longer than one hour.
  • the electrodes to be treated in accordance with the invention may have coatings in which the whole of the platinum metal content is in the form of platinum metal oxides.
  • the method of the invention is, however, also applicable to coatings wherein a minor amount of the platinum metal content is in the form of free platinum metals, the remainder and major amount being in the form of oxides.
  • the platinum metal content thus defined may consist of any one or more of the metals platinum, iridium, rhodium, osmium, ruthenium and palladium.
  • the invention is applicable to electrodes in which the coating consists entirely of platinum group metals, mainly in the oxidised state, and also to electrodes in which the coating consists of platinum group metals, mainly in the oxidised state, in association with oxides of other metals, e.g. oxides of the film-forming metals and in particular titanium as well as other film-forming metals including zirconium, niobium, tantalum and tungsten.
  • oxides with which the platinum group metal oxides may be associated include tin dioxide, germanium dioxide and oxides of antimony.
  • Specific examples of these types of coatings are coatings of ruthenium dioxide in association with titanium dioxide and coatings of ruthenium dioxide in association with mixtures of tin dioxide and oxides of antimony.
  • the invention is further illustrated by the following examples on the stripping of coatings consisting substantially of ruthenium oxide in admixture with titanium dioxide on titanium support.
  • the weight of the coatings was in the range 15-20 g./m. of the titanium surface. All percentages are by weight.
  • EXAMPLE 1 A section from a coated titanium electrode blade having the coating on both faces of the blade was immersed in a solution consisting of 80 ml. of 35% hydrochloric acid; 20 ml. of water and 0.08% ammonium fluoride (which results in an approximate HF concentration of 0.04%) at a temperature of C. After 45 minutes the coating had fallen away from the titanium support leaving a titanium surface suitable for re-coating. The loss of titanium was 9.4%.
  • EXAMPLE 2 Another section from the coated titanium electrode blade as in Example 1 was immersed in a solution consisting of 100 vols. of 35 hydrochloric acid and 0.4% ammonium fluoride (which results in an approximate HF concentration of 0.2%) at a temperature of 85 C.
  • EXAMPLE 3 EXAMPLE 4
  • another section of the coated titanium electrode blade as in Example 1 was immersed in 80 vols. of 35% hydrochloric acid and 20 vols. of water but containing no fluoride. After 13 hours the coating had only been partly removed and the surface was unsuitable for re-coating.
  • EXAMPLE 5 Another section of a coated titanium electrode blade was immersed in a solution consisting of 30 ml. of concentrated (98%) sulphuric acid, 70 ml. of water and 0.2% ammonium fluoride (which results in an approximate HF concentration of 0.1%) at a temperature of 80 C. After 53 minutes the coating had fallen away from the titanium support leaving a titanium surface suitable for re-coating. The loss of titanium was 8.1%.
  • a method for stripping the coating from an electrode comprising a titanium support and a coating comprising a platinum metal oxide thereon which comprises immersing the electrode in an aqueous mixture comprising (1) hydrochloric acid in a range of 20%40%. hydrogen chloride by weight of the total of hydrogen chloride and water or (2) sulphuric acid in a range of 25 %100% by weight of the total of sulphuric acid and water mixed with (3) hydrofluoric acid in a concentration of 0.01% to 8% hydrogen fluoride by weight of the mixture, said immersing being carried out at a temperature and for a time suflicient for the coating to become detached from the titanium support.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • ing And Chemical Polishing (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Cleaning Or Drying Semiconductors (AREA)
US00147608A 1970-06-04 1971-05-27 Stripping of coated titanium electrodes Expired - Lifetime US3761313A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2706770 1970-06-04

Publications (1)

Publication Number Publication Date
US3761313A true US3761313A (en) 1973-09-25

Family

ID=10253625

Family Applications (1)

Application Number Title Priority Date Filing Date
US00147608A Expired - Lifetime US3761313A (en) 1970-06-04 1971-05-27 Stripping of coated titanium electrodes

Country Status (9)

Country Link
US (1) US3761313A (enrdf_load_stackoverflow)
AU (1) AU2965471A (enrdf_load_stackoverflow)
BE (1) BE767908A (enrdf_load_stackoverflow)
CA (1) CA919561A (enrdf_load_stackoverflow)
FR (1) FR2094044B1 (enrdf_load_stackoverflow)
GB (1) GB1290752A (enrdf_load_stackoverflow)
IL (1) IL36914A0 (enrdf_load_stackoverflow)
SU (1) SU426351A3 (enrdf_load_stackoverflow)
ZA (1) ZA713542B (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017368A (en) * 1974-11-11 1977-04-12 General Electric Company Process for electroplating zirconium alloys
US4052253A (en) * 1976-09-27 1977-10-04 Motorola, Inc. Semiconductor-oxide etchant
US4132569A (en) * 1977-10-25 1979-01-02 Diamond Shamrock Corporation Ruthenium recovery process
US4322264A (en) * 1975-12-09 1982-03-30 U.S. Philips Corporation Method for selective etching of titaniumdioxide relative to aluminum
US4889589A (en) * 1986-06-26 1989-12-26 United Technologies Corporation Gaseous removal of ceramic coatings
US5141563A (en) * 1989-12-19 1992-08-25 Eltech Systems Corporation Molten salt stripping of electrode coatings
US6444010B1 (en) * 1999-11-11 2002-09-03 Nec Corporation Platinum group impurity recovery liquid and method for recovering platinum group impurity
US20110017608A1 (en) * 2009-07-27 2011-01-27 Faraday Technology, Inc. Electrochemical etching and polishing of conductive substrates
CN102560514A (zh) * 2012-01-16 2012-07-11 南昌航空大学 一种用于退除钛及钛合金阳极氧化膜的弱酸性悬浮液
DE102007037246B4 (de) 2006-08-10 2018-05-17 GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) Verfahren zum recyceln einer beschichteten bipolaren platte aus rostfreiem stahl

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4874434A (en) * 1988-05-16 1989-10-17 Kerr-Mcgee Chemical Corporation Method of treating a titanium structure

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3562013A (en) * 1967-10-23 1971-02-09 Diversey Corp Process of deoxidizing titanium and its alloys

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4017368A (en) * 1974-11-11 1977-04-12 General Electric Company Process for electroplating zirconium alloys
US4322264A (en) * 1975-12-09 1982-03-30 U.S. Philips Corporation Method for selective etching of titaniumdioxide relative to aluminum
US4052253A (en) * 1976-09-27 1977-10-04 Motorola, Inc. Semiconductor-oxide etchant
US4132569A (en) * 1977-10-25 1979-01-02 Diamond Shamrock Corporation Ruthenium recovery process
US4889589A (en) * 1986-06-26 1989-12-26 United Technologies Corporation Gaseous removal of ceramic coatings
US5141563A (en) * 1989-12-19 1992-08-25 Eltech Systems Corporation Molten salt stripping of electrode coatings
US6444010B1 (en) * 1999-11-11 2002-09-03 Nec Corporation Platinum group impurity recovery liquid and method for recovering platinum group impurity
DE102007037246B4 (de) 2006-08-10 2018-05-17 GM Global Technology Operations LLC (n. d. Ges. d. Staates Delaware) Verfahren zum recyceln einer beschichteten bipolaren platte aus rostfreiem stahl
US20110017608A1 (en) * 2009-07-27 2011-01-27 Faraday Technology, Inc. Electrochemical etching and polishing of conductive substrates
CN102560514A (zh) * 2012-01-16 2012-07-11 南昌航空大学 一种用于退除钛及钛合金阳极氧化膜的弱酸性悬浮液

Also Published As

Publication number Publication date
BE767908A (fr) 1971-12-01
ZA713542B (en) 1973-01-31
AU2965471A (en) 1972-12-07
FR2094044A1 (enrdf_load_stackoverflow) 1972-02-04
GB1290752A (enrdf_load_stackoverflow) 1972-09-27
FR2094044B1 (enrdf_load_stackoverflow) 1975-07-04
SU426351A3 (enrdf_load_stackoverflow) 1974-04-30
CA919561A (en) 1973-01-23
IL36914A0 (en) 1971-07-28

Similar Documents

Publication Publication Date Title
US3761313A (en) Stripping of coated titanium electrodes
FI57132C (fi) Elektrod avsedd foer anvaendning vid elektrokemiska processer
US5587058A (en) Electrode and method of preparation thereof
EP2486171B1 (en) Cathode for electrolytic processes
RU2446235C2 (ru) Катод для электролитических процессов
KR102524693B1 (ko) 전해 공정용 전극
US3725224A (en) Composition for electrolytic descaling of titanium and its alloys
CA1173303A (en) Recoating of electrodes
JPS622038B2 (enrdf_load_stackoverflow)
JPH0138873B2 (enrdf_load_stackoverflow)
US3706600A (en) Stripping of coated titanium electrodes for re-coating
US3761312A (en) Stripping of coated titanium electrodes
CA2018670A1 (en) Metal substrate of improved surface morphology
SE433624B (sv) Elektrod for anvendning vid elektrolys av en vattenlosning av metallhalogenid, forfarande for framstellning av elektroden samt anvendning av densamma
US5167788A (en) Metal substrate of improved surface morphology
US3684577A (en) Removal of conductive coating from dimensionally stable electrodes
NO129580B (enrdf_load_stackoverflow)
US3468774A (en) Electrolytic descaling of titanium and its alloys
US2408424A (en) Pickling steels
USRE28849E (en) Surface preparation process for recoating of used coated metallic electrodes
US3841983A (en) Surface preparation process for recoating of used coated metallic electrodes
US4802962A (en) Treatment of cathodes for use in electrolytic cell
US3632490A (en) Method of electrolytic descaling and pickling
US4153742A (en) Manufacture of electrodes
JPH03188291A (ja) 電解触媒被覆