WO1991013191A1 - Electrolytic removal of tin oxide or titanium nitride from a coater - Google Patents

Electrolytic removal of tin oxide or titanium nitride from a coater Download PDF

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Publication number
WO1991013191A1
WO1991013191A1 PCT/US1991/001191 US9101191W WO9113191A1 WO 1991013191 A1 WO1991013191 A1 WO 1991013191A1 US 9101191 W US9101191 W US 9101191W WO 9113191 A1 WO9113191 A1 WO 9113191A1
Authority
WO
WIPO (PCT)
Prior art keywords
tin oxide
coater
titanium nitride
electrolyte
anode
Prior art date
Application number
PCT/US1991/001191
Other languages
French (fr)
Inventor
Roy G. Gordon
Original Assignee
Gordon Roy G
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 Gordon Roy G filed Critical Gordon Roy G
Priority to DE69127073T priority Critical patent/DE69127073T2/en
Priority to JP3506007A priority patent/JP2952787B2/en
Priority to EP91906380A priority patent/EP0516757B1/en
Publication of WO1991013191A1 publication Critical patent/WO1991013191A1/en
Priority to FI923782A priority patent/FI96874C/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F5/00—Electrolytic stripping of metallic layers or coatings

Definitions

  • Glass and other transparent materials can be coated with transparent semi-conductor films such as tin oxide in order to reflect infra-red radiation. Such materials are useful in providing windows with enhanced insulating value
  • titanium nitride Another important glass coating is titanium nitride, which has optical properties that make it very efficient in controlling undesired solar heat gain through windows of buildings in warm climates.
  • a coater When a glass surface is coated with tin oxide, a coater deposits the tin oxide on a moving glass surface.
  • tin oxide When the tin oxide is formed by reaction of stannic chloride vapor with water vapor, a hard glossy deposit of tin oxide forms on the coater surface, which can be made of graphite or other corrosion-resistant materials such as nickel-based metal alloys (e.g. Inconel
  • Hastelloy (trademark of Huntington Alloys, Inc.) or Hastelloy
  • the coater surface After a production run, the coater surface must be cleaned before it is used again. Generally the tin oxide is removed by scraping. This procedure suffers from certain disadvantages. The contour of the graphite or metal is distorted because it is softer than the tin oxide and areas free of tin oxide are scraped more than areas where the tin oxide is attached. Patches of adherent tin oxide remain on the surface and an uneven surface still results. A similar problem is found with the removal of titanium nitride from its coating apparatus.
  • titanium nitride cannot be dissolved in any solvents or acids. Titanium nitride does dissolve slowly in boiling mixtures of concentrated hydrochloric and nitric acid (aqua regia) , but such a treatment of a large coater would be impractically dangerous to workers and destructive of the coater.
  • the invention comprises electrochemically removing a tin oxide or titanium nitride coating from a coater surface. This ensures that the coater surface is not injured because of the removal of the tin oxide or titanium nitride.
  • one embodiment of the invention comprises placing the tin oxide coated coater in an electrolytic bath to function as the cathode of a pair of cell electrodes.
  • the tin oxide is electrolytically removed by either reducing the tin oxide to tin metal and then dissolving the tin, or by creating a bubble of hydrogen gas at the coater surface/tin oxide interface.
  • the pressure of the hydrogen gas forces the tin oxide to break away from the coater at the coater surface/tin oxide interface. Either mechanism can occur, but preferably both mechanisms are used in combination.
  • the titanium nitride coated coater surface is placed as the anode in an electrolytic cell.
  • the titanium nitride is removed electrolytically by either being oxidized and dissolved, or by breaking off in flakes probably dislodged by bubbles of oxygen and/or other gases evolving at the coater surface.
  • Figure 1 illustrates an electrolytic cell used for the removal of tin oxide
  • Figure 2 illustrates an electrolytic cell used for the removal of titanium nitride.
  • a graphite coater section 10 having a surface covered by a tin oxide layer 12 between 0.5 to 2.0 mm thick and about 3 m 2 in area is placed in a bath 14 of dilute hydrochloric acid (one volume concentrated 37% by weight HC1, ten volumes of water) .
  • the coated graphite functions as the cathode.
  • Another electrode 16, which is also graphite, functions as the anode.
  • the electromotive force from power source 18 is about 12 volts direct current.
  • the anode of this preferred embodiment is graphite because most metals would be anodically corroded into solution.
  • the tin oxide is removed from the graphite: (1) The tin oxide is reduced at the cathode to metallic tin while the oxygen forms water with the hydrogen. The metallic tin is subsequently dissolved by the hydrochloric acid. (2) The graphite may be wetted with the electrolyte through cracks in the tin oxide. Then, hydrogen gas forms in the region adjacent to the graphite surface/tin oxide interface, and there is a pressure increase of the hydrogen gas. The increase in pressure tends to force or break away the tin oxide from the surface of the graphite.
  • Acid electrolytes such as hydrochloric acid
  • neutral salt electrolytes such as sodium or ammonium salts
  • gas bubbles In general, conditions which favor hydrogen gas formation at the coater surface will enhance the gas bubble mechanism.
  • FIG. 2 A second embodiment of the invention illustrated in Figure 2, which shows the bottom surface of a Hastelloy coater 20 covered with a layer 22 of titanium nitride placed in an electrolyte bath 24.
  • the electrolyte is dilute hydrochloric acid (one volume concentrated hydrochloric, 37% by weight in water, diluted with ten volumes of water) .
  • the titanium nitride-coated coater functions as the anode (positive electrode) of the cell.
  • Another electrode 26, made of graphite serves as the cathode. Any acid- resistant, electrically conducting material can serve as the cathode. About 12 volts direct current is applied to the cell by power source 28, which is a battery charger.
  • Dilute sulfuric acid also functions as an effective electrolyte (one part concentrated sulfuric acid to ten parts of water by volume) .
  • An advantage of the sulfuric bath is that it produces no volatile acid fumes (in contrast to the hydrochloric acid fumes) , and the anode produces only pure oxygen gas and no chlorine.
  • a disadvantage of the sulfuric acid bath is it is more hazardous to personnel.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Engineering & Computer Science (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Surface Treatment Of Glass (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Physical Vapour Deposition (AREA)
  • Cold Cathode And The Manufacture (AREA)

Abstract

A method for the removal of tin oxide (12) or titanium nitride (22) from a coater surface (10). The coater (10) is used to apply the tin oxide (12) or titanium nitride (22) to a glass substrate. When the build-up of tin oxide (12) or titanium nitride (22) on the surface (10) reaches a certain thickness, it must be removed. The coated surface (10) is used as a cathode in an electrolyte (14) having an anode (16). The tin oxide (12) or titanium nitride (22) is electrochemically removed from the surface (10).

Description

TITLE
Electrolytic removal of tin oxide or titanium nitride from a coater
BACKGROUND OF THE INVENTION Glass and other transparent materials can be coated with transparent semi-conductor films such as tin oxide in order to reflect infra-red radiation. Such materials are useful in providing windows with enhanced insulating value
(lower heat transport) for use in architectural windows, etc.; see for example, RE 31,708. Coatings on glass of tin oxide in combination with other coatings, such as iridescence - suppression coatings, are now enjoying commercial acceptance.
Another important glass coating is titanium nitride, which has optical properties that make it very efficient in controlling undesired solar heat gain through windows of buildings in warm climates.
When a glass surface is coated with tin oxide, a coater deposits the tin oxide on a moving glass surface. Ideally, it would be desirable to control the fluid flow characteristics of the reactants which form the tin oxide and the spatial relationship between the coater surface overlying the moving glass surface, such that the tin oxide which is formed, would only deposit on the moving glass surface. As a practical matter this has not been possible to achieve with the result that the tin oxide also coats the coater surface overlying the glass surface on which the tin oxide is deposited. When the tin oxide is formed by reaction of stannic chloride vapor with water vapor, a hard glossy deposit of tin oxide forms on the coater surface, which can be made of graphite or other corrosion-resistant materials such as nickel-based metal alloys (e.g. Inconel
(trademark of Huntington Alloys, Inc.) or Hastelloy
(trademark of Haynes International, Inc.)).
A similar effect occurs when glass is coated with titanium nitride by the reaction of titanium tetrachloride with ammonia, according to U.S. Patent No. 4,535,000. A hard layer of titanium nitride forms on the coater, as well as on the glass.
After a production run, the coater surface must be cleaned before it is used again. Generally the tin oxide is removed by scraping. This procedure suffers from certain disadvantages. The contour of the graphite or metal is distorted because it is softer than the tin oxide and areas free of tin oxide are scraped more than areas where the tin oxide is attached. Patches of adherent tin oxide remain on the surface and an uneven surface still results. A similar problem is found with the removal of titanium nitride from its coating apparatus.
It is known to use zinc powder and hydrochloric acid to etch tin oxide. However, this method is not convenient for thick layers of tin oxide, say ranging between 0.5 to 2.0 mm thick nor is it easily practiced over large areas, say for example 3 m2. Similarly, titanium nitride cannot be dissolved in any solvents or acids. Titanium nitride does dissolve slowly in boiling mixtures of concentrated hydrochloric and nitric acid (aqua regia) , but such a treatment of a large coater would be impractically dangerous to workers and destructive of the coater.
SUMMARY OF THE INVENTION
Briefly the invention comprises electrochemically removing a tin oxide or titanium nitride coating from a coater surface. This ensures that the coater surface is not injured because of the removal of the tin oxide or titanium nitride.
Broadly one embodiment of the invention comprises placing the tin oxide coated coater in an electrolytic bath to function as the cathode of a pair of cell electrodes. The tin oxide is electrolytically removed by either reducing the tin oxide to tin metal and then dissolving the tin, or by creating a bubble of hydrogen gas at the coater surface/tin oxide interface. The pressure of the hydrogen gas forces the tin oxide to break away from the coater at the coater surface/tin oxide interface. Either mechanism can occur, but preferably both mechanisms are used in combination.
The relative importance of the two removal mechanisms varies with such conditions as the electrolyte, voltage, current and temperature used.
In another embodiment of the invention, the titanium nitride coated coater surface is placed as the anode in an electrolytic cell. The titanium nitride is removed electrolytically by either being oxidized and dissolved, or by breaking off in flakes probably dislodged by bubbles of oxygen and/or other gases evolving at the coater surface.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates an electrolytic cell used for the removal of tin oxide; and
Figure 2 illustrates an electrolytic cell used for the removal of titanium nitride.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In Figure 1, a graphite coater section 10 having a surface covered by a tin oxide layer 12 between 0.5 to 2.0 mm thick and about 3 m2 in area is placed in a bath 14 of dilute hydrochloric acid (one volume concentrated 37% by weight HC1, ten volumes of water) . The coated graphite functions as the cathode. Another electrode 16, which is also graphite, functions as the anode. The electromotive force from power source 18 is about 12 volts direct current. The anode of this preferred embodiment is graphite because most metals would be anodically corroded into solution.
There are two mechanisms by which the tin oxide is removed from the graphite: (1) The tin oxide is reduced at the cathode to metallic tin while the oxygen forms water with the hydrogen. The metallic tin is subsequently dissolved by the hydrochloric acid. (2) The graphite may be wetted with the electrolyte through cracks in the tin oxide. Then, hydrogen gas forms in the region adjacent to the graphite surface/tin oxide interface, and there is a pressure increase of the hydrogen gas. The increase in pressure tends to force or break away the tin oxide from the surface of the graphite.
Acid electrolytes, such as hydrochloric acid, tend to emphasize dissolution, while neutral salt electrolytes, such as sodium or ammonium salts, favor delamination by gas bubbles. In general, conditions which favor hydrogen gas formation at the coater surface will enhance the gas bubble mechanism.
A second embodiment of the invention illustrated in Figure 2, which shows the bottom surface of a Hastelloy coater 20 covered with a layer 22 of titanium nitride placed in an electrolyte bath 24. The electrolyte is dilute hydrochloric acid (one volume concentrated hydrochloric, 37% by weight in water, diluted with ten volumes of water) . The titanium nitride-coated coater functions as the anode (positive electrode) of the cell. Another electrode 26, made of graphite, serves as the cathode. Any acid- resistant, electrically conducting material can serve as the cathode. About 12 volts direct current is applied to the cell by power source 28, which is a battery charger. Some of the titanium nitride is dissolved, while the rest falls off in flakes dislodged by bubbles of oxygen and chlorine gas formed at the coater surface. Dilute sulfuric acid also functions as an effective electrolyte (one part concentrated sulfuric acid to ten parts of water by volume) . An advantage of the sulfuric bath is that it produces no volatile acid fumes (in contrast to the hydrochloric acid fumes) , and the anode produces only pure oxygen gas and no chlorine. A disadvantage of the sulfuric acid bath is it is more hazardous to personnel.
Although described in reference to specific process conditions and specific electrodes, those skilled in the art will recognize that other electrolytes and electrodes may be used and are within the scope of the invention.
Having described my invention, what I now claim is:

Claims

Claim 1. A method for the electrolytic removal of tin oxide from a coater surface which comprises: providing an electrolytic cell having electrolyte and a pair of electrodes, the tin oxide coated surface functioning as a cathode and the other electrode functioning as the anode; and applying a voltage across the electrodes sufficient to remove tin oxide from the surface.
Claim 2. The method of Claim 1 which includes: reducing the tin oxide on the surface to form metallic tin; and dissolving the metallic tin.
Claim 3. The method of Claims 1 or 2 which includes: forming hydrogen gas in the region adjacent the coater surface/tin oxide interface; and increasing the pressure of the hydrogen gas to force the tin oxide to break away from the coater surface.
Claim 4. The method of Claim 1 wherein the anode is graphite.
Claim 5. A method for the electrolytic removal of titanium nitride from a coater surface which comprises: providing an electrolytic cell having an electrolyte and a pair of electrodes, the titanium nitride coated coater surface functioning as an anode and the other electrode functioning as the cathode; and applying a voltage across the electrodes sufficient to remove the titanium nitride from the surface of the coater.
Claim 6. The method of Claims 1 or 5 wherein the electrolyte is an aqueous solution of hydrochloric acid.
Claim 7. The method of Claims 1 or 5 wherein the electrolyte is an aqueous solution of sulfuric acid.
PCT/US1991/001191 1990-02-23 1991-02-15 Electrolytic removal of tin oxide or titanium nitride from a coater WO1991013191A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
DE69127073T DE69127073T2 (en) 1990-02-23 1991-02-15 ELECTROLYTIC REMOVAL OF TIN NOXIDE FROM A COATING SYSTEM
JP3506007A JP2952787B2 (en) 1990-02-23 1991-02-15 Electrolytic removal of tin oxide or titanium nitride from coater
EP91906380A EP0516757B1 (en) 1990-02-23 1991-02-15 Electrolytic removal of tin oxide from a coater
FI923782A FI96874C (en) 1990-02-23 1992-08-21 Electrolytic removal of tin oxide or titanium nitride from the coating

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/484,129 US5227036A (en) 1990-02-23 1990-02-23 Electrolytic removal of tin oxide from a coater
US484,129 1990-02-23

Publications (1)

Publication Number Publication Date
WO1991013191A1 true WO1991013191A1 (en) 1991-09-05

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PCT/US1991/001191 WO1991013191A1 (en) 1990-02-23 1991-02-15 Electrolytic removal of tin oxide or titanium nitride from a coater

Country Status (9)

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US (1) US5227036A (en)
EP (1) EP0516757B1 (en)
JP (1) JP2952787B2 (en)
AT (1) ATE156202T1 (en)
CA (1) CA2075943A1 (en)
DE (1) DE69127073T2 (en)
ES (1) ES2104694T3 (en)
FI (1) FI96874C (en)
WO (1) WO1991013191A1 (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4303137A1 (en) * 1993-02-04 1994-08-11 Mtu Muenchen Gmbh Method for removing ceramic layers on metal components
WO1998003702A1 (en) * 1996-07-19 1998-01-29 Sandvik Ab (Publ) Method for obtaining a high surface finish on titanium based coatings
WO2003085174A2 (en) * 2002-04-08 2003-10-16 Siemens Aktiengesellschaft Device and method for removing surface areas of a component
DE10259364A1 (en) * 2002-12-18 2004-07-08 Siemens Ag Method for removing at least one surface area of a bag
DE10259363A1 (en) * 2002-12-18 2004-07-08 Siemens Ag Method for removing at least one surface area of a component
US9333623B2 (en) 2010-08-14 2016-05-10 Mtu Aero Engines Gmbh Method and device for removing a layer from a surface of a body

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6045686A (en) * 1997-03-18 2000-04-04 The University Of Connecticut Method and apparatus for electrochemical delacquering and detinning
WO2011044340A1 (en) * 2009-10-08 2011-04-14 First Solar, Inc. Electrochemical method and apparatus for removing coating from a substrate
WO2011075416A1 (en) * 2009-12-18 2011-06-23 First Solar, Inc. Film removal

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63186899A (en) * 1987-01-28 1988-08-02 Asahi Glass Co Ltd Method for dissolving tin oxide

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT943166B (en) * 1971-12-03 1973-04-02 Olivetti & Co Spa PROCEDURE FOR THE ELECTRO-LITHIC ATTACHMENT OF SAGNO OXIDE OR INDIUM OXIDE DEPOSITED ON GLASS
US4135989A (en) * 1978-04-27 1979-01-23 E-Systems, Inc. Electrolytic etching of tin oxide films
DE3048083C2 (en) * 1980-12-19 1983-09-29 Ludwig 8900 Augsburg Fahrmbacher-Lutz Process for the chemical removal of oxide layers from objects made of titanium or titanium alloys
DD230811A1 (en) * 1983-06-22 1985-12-11 Blechbearbeitungsmaschinenwerk PROCESS AND DEVICE FOR SURFACE MACHINING COATED WORKSTUECKE
JPS63171900A (en) * 1987-01-09 1988-07-15 Asahi Glass Co Ltd Production of transparent electrode

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63186899A (en) * 1987-01-28 1988-08-02 Asahi Glass Co Ltd Method for dissolving tin oxide

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4303137A1 (en) * 1993-02-04 1994-08-11 Mtu Muenchen Gmbh Method for removing ceramic layers on metal components
WO1998003702A1 (en) * 1996-07-19 1998-01-29 Sandvik Ab (Publ) Method for obtaining a high surface finish on titanium based coatings
WO2003085174A2 (en) * 2002-04-08 2003-10-16 Siemens Aktiengesellschaft Device and method for removing surface areas of a component
WO2003085174A3 (en) * 2002-04-08 2004-12-23 Siemens Ag Device and method for removing surface areas of a component
EP1632589A2 (en) * 2002-04-08 2006-03-08 Siemens Aktiengesellschaft Device and method for removing surface areas of a component
EP1632589A3 (en) * 2002-04-08 2006-04-05 Siemens Aktiengesellschaft Device and method for removing surface areas of a component
DE10259364A1 (en) * 2002-12-18 2004-07-08 Siemens Ag Method for removing at least one surface area of a bag
DE10259363A1 (en) * 2002-12-18 2004-07-08 Siemens Ag Method for removing at least one surface area of a component
US9333623B2 (en) 2010-08-14 2016-05-10 Mtu Aero Engines Gmbh Method and device for removing a layer from a surface of a body

Also Published As

Publication number Publication date
EP0516757A4 (en) 1993-06-30
FI923782A (en) 1992-08-21
US5227036A (en) 1993-07-13
FI96874C (en) 1996-09-10
FI96874B (en) 1996-05-31
DE69127073T2 (en) 1998-01-22
CA2075943A1 (en) 1991-08-24
ATE156202T1 (en) 1997-08-15
EP0516757B1 (en) 1997-07-30
DE69127073D1 (en) 1997-09-04
JPH05506694A (en) 1993-09-30
ES2104694T3 (en) 1997-10-16
FI923782A0 (en) 1992-08-21
EP0516757A1 (en) 1992-12-09
JP2952787B2 (en) 1999-09-27

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