US3864219A - Process and electrolyte for applying barrier layer anodic coatings - Google Patents

Process and electrolyte for applying barrier layer anodic coatings Download PDF

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Publication number
US3864219A
US3864219A US431818A US43181874A US3864219A US 3864219 A US3864219 A US 3864219A US 431818 A US431818 A US 431818A US 43181874 A US43181874 A US 43181874A US 3864219 A US3864219 A US 3864219A
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United States
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metal
current
electrolyte
group
aluminum
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US431818A
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English (en)
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Robert G Dosch
Thomas S Prevender
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US Atomic Energy Commission (AEC)
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US Atomic Energy Commission (AEC)
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Priority to US431818A priority Critical patent/US3864219A/en
Priority to GB5154774A priority patent/GB1449080A/en
Priority to CA214,971A priority patent/CA1030096A/en
Priority to FR7500365A priority patent/FR2256969B3/fr
Priority to DE19752500541 priority patent/DE2500541A1/de
Priority to JP50004528A priority patent/JPS50100570A/ja
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation

Definitions

  • Barrier anodization generally refers to anodic coatings that are essentially pore free and are generally of the order of about 10' meters in thickness whereas conventional anodic coatings are about l meters in thickness. Barrier anodization using prior art processes and electrolytes has been successful in barrier anodizing high purity aluminum but has generally been unsuccessful in attempting to barrier anodize either aluminum alloys or large areas of pure aluminum with pore free anodized films.
  • barrier anodizing electrolytes for aluminum such as (a) aqueous boric acid-borax solutions, (b) aqueous or semi-aqueous solutions containing citrate or tartrate ions, and (c) solutions of ammonium pentaborate decahydrate in ethylene glycol may be suitable for high-purity aluminum, but are generally unsuitable for barrier anodizing of aluminum alloys such as 7075 aluminum. Alluminum alloys referred to herein are designated by the four-digit designation system established by the Aluminum Association and generally known in the art.
  • the invention comprises a novel anodizing, and especially barrier anodizing, electrolyte and the method for using this electrolyte, which electrolyte includes a quaternary ammonium compound having a compex metal anion dissolved in a solvent.
  • electrolyte includes a quaternary ammonium compound having a compex metal anion dissolved in a solvent.
  • metals which may be barrier anodized using this electrolyte include tantalum, tungsten, niobium, titanium beryllium, uranium, aluminum and alloys thereof.
  • FIG. 1 represents a electrical schematic for anodizing.
  • FIG. 2 illustrates current-voltage curves derived in barrier anodizing of pure aluminum.
  • FIG. I representsan electrical schematic of an anod- 0 izing apparatus which may be used with this invention.
  • the electrolyte 12 described hereinbelow is disposed within a container 14 and may be stirred or agitated using a magnetic or the like stirrer 15 together with stirring means such as a plastic coated magnet 16.
  • the anode l8 and cathode may be electrically connected by means of electrical conductors 22, 24 to a power supply such as a variable voltage power supply 30.
  • an ammeter 36 and a voltmeter 38 may be disposed in the circuit as shown in order to measure current flow through the circuit.
  • R N represents an alkyl group generally containing from I to 4 carbon atoms, an aryl group, or a mixture ofthese to form the quaternary ammonium ion
  • 0 oxygen
  • H represents hydrogen
  • M represents a metal such as niobium, tantalum, or titanium
  • the complex ion contains two or more atoms of metal.
  • Compounds having this formula such as tetramethylammonium niobate, tetramethylammonium titanate and tetramethylammonium tantalate, may be formed by reacting quaternary ammonium hydroxide with a metal alkoxide. It is believed that the following equation accurately represents the portion of a reaction that is pertinent to this invention, but the invention is not to be bound or restricted by this belief:
  • R and R may be alkyl or other organic groups containing from 1 to about 4 carbon atoms
  • n is the valence of the metal M
  • M may be such as niobium, tantalum and titanium.
  • the metal alkoxide is then mixed and thereby reacted with the quaternary ammonium hydroxide to form the desired quaternary ammonium compound having a complex metal anion.
  • This compound may be separated from the reaction products by precipitation with a less polar solvent such as acetone and subsequently separating by suitable processes such as filtration or decantation. 1
  • This compound is dissolved in a suitable solvent com prising water and a polar, water soluble organic liquid such as alcohol or ethylene glycol wherein the alcohol volume percent may be from about I to about 80 per cent andpreferably from about 20 to about 80, and
  • Typical alcohols which may be used are such as ethanol, methanol, propanol, etc. and which have the general formula ROH where R may contain 1 to about 3 carbon atoms.
  • ROH where R may contain 1 to about 3 carbon atoms.
  • the amount of compound to be dissolved in the solvent is dependent upon many factors such as the extent of use to be made of the electrolyte, but may generally be from about 1 to about grams per about 1,000 milliliters of solvent. It may be generally desirable to dissolve the compound in water and thereafter add a sufficient amount of a polar, water soluble organic material to bring to the desired volume.
  • the resultant solution confilms which were formed on 606] aluminum with the present invention.
  • the electrolyte was prepared by dissolving 5 grams of tetramethylammonium niobate compound in about 500 milliliters of water and thereafter diluting to a volume of about 2,000 milliliters with ethyl alcohol.
  • the samples to be anodized which were about 3 inch squares (about 18 square inches surface area) of about 90 mil thickness of 6,061 aluminum alloy, were cleaned by scrubbing the surface with an alkaline solution, immersing thereafter in an ultrasonic bath containing trichloroethylene, and thereafter rinsing with ethyl alcohol:
  • taining the dissolved compound is used as the barrier anodizing electrolyte and may be at a temperature of from about 0 to about 60C, and preferably at from about to about C.
  • the materials to be anodized may be suitably cleaned or given a cleaning pretreatment through various means.
  • barrier anodic films can be formed on a 6,061 aluminum alloy after a cleaning pretreatment involving a detergent scrub and a vapor degreasing of the surface.
  • Other cleaning procedures may involve cleaning the asreceived surface with a suitable alkaline material, thereafter immersing the sample in an ultrasonic bath containing a suitable solvent such as trichloroethylene, and finally rinsing the sample with a suitable alcohol such as ethyl alcohol.
  • An alternative and preferred cleaning pretreatment sequence to be used for aluminum and aluminum alloys may involve degreasing the surface with a suitable solvent such as trichloroethylene, contacting the sample surface with an about 5 weight percent sodium hydroxide solution at a temperature of about 160F for about 5 minutes, rinsing the etched sample with deionized water, contacting the sample with a 50 volume percent nitric acid solution which may be at about 90F for about 5 minutes, thereafter rinsing again in deionized water, immersing the sample in a 20 volume percent sulfuric acid solution at about 80F until such time as gas bubbles form on the aluminum surface such as about 5 minutes, and then applying an anodizing electrical current for about 90 seconds at a current density of 5 milliamps per square centimeter using a platinum, stainless steel or tantalum cathode, thereafter soaking the sample in said sulfuric acid bath for about 5 to 10 minutes after bubbles form on the aluminum surface, and thereafter rinsing with deionized water followed by a suitable
  • the following table illustrates various properties of The cleaned samples were then immersed in the electrolyte and appropriately connected to electrical anodic leads.
  • the cathode may be any suitable material such as platinum, tantalum, and stainless steel.
  • the samples were anodized at a constant current of 2 milliamps per square centimeter until the voltage increased to a preset value as shown in the table.
  • the voltage used is a function of the thickness of the anodic coating desired as described below. 300 and 500 volts were used as a preset value for these samples. When the desired voltage was reached, the voltage was held constant and the current was allowed to decrease to approximately 10 percent of its initial value. Current and voltage curves have been plotted against time and the results are similar to the FIG.
  • Curve A represents voltage increase as a function of time to a preset voltage.
  • Curve B represent current change as a function of time while the voltage increases to a preset value and is maintained constant thereafter.
  • the anodizing procedure employed maintained the current constant until a preset voltage was attained, it may be seen that the same coating may be achieved by retaining the voltage constant and varying the current, or combination of these where the current or the voltage may be retained constant in increments until the desired results are achieved.
  • the voltage was held constant after the desired voltage was attained and the current was allowed to decrease to a percentage of the initial value, it may be desirable to remove the barrier anodized material immediately upon attaining the .preset voltage. This is to be done at the discretion of the operator.
  • the thickness of the barrier anodic film has been shown to be proportional to voltage with film thickness in angstroms approximately equal to 12 times the final adodizing voltage.
  • the 300 V anodizing voltage yielded a thickness of about 3,6OOA and the 500 V setting yielded a thickness of about 6,000A.
  • Film thicknesses of 6,500 A have also been applied to pure aluminum and aluminum alloys such as 6,061 A] and 7075 Al.
  • a gold counter electrode was deposited over a centimeter square area of the barrier anodic film obtained by the above process and tested.
  • the above table illustrates the electrical properties deteremined on one set of samples.
  • This invention demonstrates that the novel electrolyte of this invention can be used to form barrier anodic films on materials which are not commonly amenable to prior art electrolytes, and the method for using this electrolyte.
  • other aluminum base metals which have been anodized include 5,457 Al, 7,075 Al, 4,043 Al and pure aluminum. Except for 4,043 A] which was not tested, these had leakage currents at 2 volts of about 4 X 10 amperes per square centimeter. Areas as large as 575 square inches of 6,061 Al have been barrier anodized at 500 V to a thickness of about 6,000A using this electrolyte and process.
  • Voltages used in barrier anodizing other metals using the process and electrolyte of this invention include uranium alloys 400 volts, beryllium- 300 volts, tantalum 300 volts, tungsten 150 volts, niobium 200 volts and titanium 400 volts. These voltages are merely exemplary and could be larger or smaller depending upon film properties desired.
  • said solvent comprises from about I to about volume percent water and from about 99 to about 20 volume percent alcohol.
  • said quaterenary ammonium compound comprises from about 1 to about l0 grams of said compound per liter of solvent.
  • said quaternary ammonium compound is a reaction product of a quaternary alkyl ammonium hydroxide and a metal alkoxide.
  • said quaternary ammonium compound is selected from the group consisting of tetramethylammonium niobate, tetramethylammonium titanate, tetramethylammonium tantalate.
  • said cleaning comprises degreasing the metal, etching the surface by contacting said surface in an alkaline bath, rinsing said etched surface with deionized water, contacting said surface with an about 50 volume percent nitric acid solution to desmut said surface, rinsing said surface with deionized water, immersing said surface in an about 20 volume percent sulfuric acid solution, attaching an electrical lead to said metal to make it an anode, applying current to said anode for about seconds, thereafter soaking said surface for from about 5 to about 10 minutes in said sulfuric acid bath, rinsing said surface with deionized water and rinsing said surface with an alcohol.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Electrochemical Coating By Surface Reaction (AREA)
  • Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
US431818A 1974-01-08 1974-01-08 Process and electrolyte for applying barrier layer anodic coatings Expired - Lifetime US3864219A (en)

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Application Number Priority Date Filing Date Title
US431818A US3864219A (en) 1974-01-08 1974-01-08 Process and electrolyte for applying barrier layer anodic coatings
GB5154774A GB1449080A (en) 1974-01-08 1974-11-28 Electrolyte for applying barrier anodic coatings
CA214,971A CA1030096A (en) 1974-01-08 1974-11-29 Electrolyte for applying barrier anodic coatings
FR7500365A FR2256969B3 (enrdf_load_stackoverflow) 1974-01-08 1975-01-07
DE19752500541 DE2500541A1 (de) 1974-01-08 1975-01-08 Elektrolyt zum aufbringen von anodischen sperrueberzuegen
JP50004528A JPS50100570A (enrdf_load_stackoverflow) 1974-01-08 1975-01-08

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JP (1) JPS50100570A (enrdf_load_stackoverflow)
CA (1) CA1030096A (enrdf_load_stackoverflow)
DE (1) DE2500541A1 (enrdf_load_stackoverflow)
FR (1) FR2256969B3 (enrdf_load_stackoverflow)
GB (1) GB1449080A (enrdf_load_stackoverflow)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4717455A (en) * 1985-11-25 1988-01-05 Swiss Aluminium Ltd. Process for manufacturing a microfilter
US5716511A (en) * 1996-08-07 1998-02-10 Kemet Electronics Corporation Anodizing electrolyte and its use
US5733420A (en) * 1992-11-10 1998-03-31 Casio Computer Co., Ltd. Anodizing apparatus and an anodizing method
GB2343681A (en) * 1998-11-16 2000-05-17 Agfa Gevaert Nv Lithographic printing plate support
US20060191796A1 (en) * 2004-12-06 2006-08-31 Greatbatch, Inc. Anodizing Valve Metals By Controlled Power
WO2006050401A3 (en) * 2004-10-29 2007-07-26 Medtronic Inc Processes and systems for formation of high voltage, anodic oxide on a valve metal anode
US20080169200A1 (en) * 2007-01-17 2008-07-17 Thomas David Burleigh Method of Anodizing Steel
US20080250621A1 (en) * 2005-03-30 2008-10-16 Showa Denko K.K. Solid Electrolytic Capacitor Element, Method for Manufacturing Same, and Solid Electrolytic Capacitor
US20090205970A1 (en) * 2003-03-17 2009-08-20 John Tony Kinard Capacitor containing aluminum anode foil anodized in low water content glycerine-phosphate electrolyte without a pre-anodizing hydaration step
US20090286385A1 (en) * 2008-05-19 2009-11-19 Advanced Micro Devices, Inc. Methods for removing a photoresist from a metal-comprising material
US20090315062A1 (en) * 2008-06-24 2009-12-24 Wen-Herng Su Light Emitting Diode Submount With High Thermal Conductivity For High Power Operation
CN1908245B (zh) * 2006-07-24 2010-08-11 北京航空航天大学 基于酒石酸铵体系的钛合金阳极氧化工艺
US20110284390A1 (en) * 2007-01-17 2011-11-24 Thomas David Burleigh Method of anodizing steel
US20120247961A1 (en) * 2005-06-17 2012-10-04 Mitsubishi Chemical Corporation Metal oxide film, laminate, metal member and process for producing the same
US8696767B2 (en) 2007-05-21 2014-04-15 Showa Denko K.K. Dipping method of forming cathode of solid electrolytic capacitor
US9478587B1 (en) 2015-12-22 2016-10-25 Dicon Fiberoptics Inc. Multi-layer circuit board for mounting multi-color LED chips into a uniform light emitter

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5376848A (en) * 1976-12-20 1978-07-07 Toshiba Corp Electrochromic display device
JPS6045008A (ja) * 1983-08-22 1985-03-11 松下電器産業株式会社 薄膜コンデンサの製造方法
RU2123546C1 (ru) * 1997-06-17 1998-12-20 Тюменский государственный нефтегазовый университет Способ твердого оксидирования алюминия и его сплавов
RU2124588C1 (ru) * 1997-12-30 1999-01-10 Закрытое акционерное общество "Техно-ТМ" Способ микроплазменного оксидирования вентильных металлов и их сплавов и устройство для его осуществления

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524799A (en) * 1969-06-13 1970-08-18 Reynolds Metals Co Anodizing aluminum
US3796644A (en) * 1972-05-03 1974-03-12 Sprague Electric Co Electrolytic formation process for aluminum capacitor electrodes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524799A (en) * 1969-06-13 1970-08-18 Reynolds Metals Co Anodizing aluminum
US3796644A (en) * 1972-05-03 1974-03-12 Sprague Electric Co Electrolytic formation process for aluminum capacitor electrodes

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4717455A (en) * 1985-11-25 1988-01-05 Swiss Aluminium Ltd. Process for manufacturing a microfilter
US5733420A (en) * 1992-11-10 1998-03-31 Casio Computer Co., Ltd. Anodizing apparatus and an anodizing method
US5716511A (en) * 1996-08-07 1998-02-10 Kemet Electronics Corporation Anodizing electrolyte and its use
GB2343681A (en) * 1998-11-16 2000-05-17 Agfa Gevaert Nv Lithographic printing plate support
EP1002644A3 (en) * 1998-11-16 2004-01-14 Agfa-Gevaert Production of support for lithographic printing plate.
US20090205970A1 (en) * 2003-03-17 2009-08-20 John Tony Kinard Capacitor containing aluminum anode foil anodized in low water content glycerine-phosphate electrolyte without a pre-anodizing hydaration step
US7780835B2 (en) * 2003-03-17 2010-08-24 Kemet Electronics Corporation Method of making a capacitor by anodizing aluminum foil in a glycerine-phosphate electrolyte without a pre-anodizing hydration step
WO2006050401A3 (en) * 2004-10-29 2007-07-26 Medtronic Inc Processes and systems for formation of high voltage, anodic oxide on a valve metal anode
US20060191796A1 (en) * 2004-12-06 2006-08-31 Greatbatch, Inc. Anodizing Valve Metals By Controlled Power
US20080250621A1 (en) * 2005-03-30 2008-10-16 Showa Denko K.K. Solid Electrolytic Capacitor Element, Method for Manufacturing Same, and Solid Electrolytic Capacitor
US7811338B2 (en) 2005-03-30 2010-10-12 Murata Manufacturing Co., Ltd. Solid electrolytic capacitor element, method for manufacturing same, and solid electrolytic capacitor
US20120247961A1 (en) * 2005-06-17 2012-10-04 Mitsubishi Chemical Corporation Metal oxide film, laminate, metal member and process for producing the same
US9476137B2 (en) * 2005-06-17 2016-10-25 Tohoku University Metal oxide film, laminate, metal member and process for producing the same
CN1908245B (zh) * 2006-07-24 2010-08-11 北京航空航天大学 基于酒石酸铵体系的钛合金阳极氧化工艺
US20080169200A1 (en) * 2007-01-17 2008-07-17 Thomas David Burleigh Method of Anodizing Steel
US20110284390A1 (en) * 2007-01-17 2011-11-24 Thomas David Burleigh Method of anodizing steel
US8696767B2 (en) 2007-05-21 2014-04-15 Showa Denko K.K. Dipping method of forming cathode of solid electrolytic capacitor
US20090286385A1 (en) * 2008-05-19 2009-11-19 Advanced Micro Devices, Inc. Methods for removing a photoresist from a metal-comprising material
US8044427B2 (en) * 2008-06-24 2011-10-25 Dicon Fiberoptics, Inc. Light emitting diode submount with high thermal conductivity for high power operation
US20090315062A1 (en) * 2008-06-24 2009-12-24 Wen-Herng Su Light Emitting Diode Submount With High Thermal Conductivity For High Power Operation
US9478587B1 (en) 2015-12-22 2016-10-25 Dicon Fiberoptics Inc. Multi-layer circuit board for mounting multi-color LED chips into a uniform light emitter

Also Published As

Publication number Publication date
GB1449080A (en) 1976-09-08
FR2256969A1 (enrdf_load_stackoverflow) 1975-08-01
JPS50100570A (enrdf_load_stackoverflow) 1975-08-09
FR2256969B3 (enrdf_load_stackoverflow) 1977-09-30
DE2500541A1 (de) 1975-07-17
CA1030096A (en) 1978-04-25

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