US3522166A - Electrical system for anodizing - Google Patents

Electrical system for anodizing Download PDF

Info

Publication number
US3522166A
US3522166A US632632A US3522166DA US3522166A US 3522166 A US3522166 A US 3522166A US 632632 A US632632 A US 632632A US 3522166D A US3522166D A US 3522166DA US 3522166 A US3522166 A US 3522166A
Authority
US
United States
Prior art keywords
cathode
elements
anodizing
anodized
current
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
US632632A
Other languages
English (en)
Inventor
Garth Sanford Jones
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.)
Reynolds Metals Co
Original Assignee
Reynolds Metals Co
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 Reynolds Metals Co filed Critical Reynolds Metals Co
Application granted granted Critical
Publication of US3522166A publication Critical patent/US3522166A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • 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
    • C25D11/005—Apparatus specially adapted for electrolytic conversion coating
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/12—Process control or regulation

Definitions

  • anodization is proportional to the current density utilized.
  • the resistivity of a portion of the surface being anodized varies, as for example due to thermal, metallurgical or chemical anomalies at the metal surface, the resultant change in current density causes localized thickness variations in the anodized layer. More particularly, when the resistivity of a particular area is less than its surroundings, the current flow concentrates in that area increasing the current density, with a corresponding decrease in current density occurring in the surrounding areas. Such an effect results in localized build up of the anodized layer to exceed that of the surrounding metal from which anodizing current has been diverted.
  • the increase in current density just described generates heat in the affected localized area. This heat tends to further increase the electrical conductivity of the area, as well as to increase the solubility of the anodized layer in the anodization electrolyte.
  • the increased anodizer layer thickness caused by higher current density insuiciently increases the resistivity of the localized area so as to compensate for the eiects brought on by the aforementioned heat generation, burning occurs on the anodized surface. This burning is in the form of thermochemical attack on the anodized layer.
  • the principal object of the present invention is to provide an anodizing system which is operable at high cur- Lce rent densities and which reduces the problems of localized thickness variations and burning of the anodized surface.
  • the attainment of this object permits the system to be used in a continuous, high speed anodizing operation with resultant improvements in quality, productivity and economy.
  • the invention comprises an anodizing system in which a plurality of spaced, electrically isolated cathode elements are positioned in close proximity with respect to the metal being anodized.
  • Each cathode element is dimensioned so as to afrect the anodization of only a portion of the metal.
  • the spacing between cathode elements is greater than 4between the elements and the surface being arnodized thereby eiiectively preventing the concentration of current paths from several cathode elements to a localized anode area.
  • FIG. l is a diagrammatic representation of an anodizing system according to the invention illustrating a typical cathode arrangement
  • FIG. 2 is a cross-sectional representation of an electrolytic cell for anodizing illustrating, according to the invention, the spacing relationship between adjacent cathode elements and between the cathode elements and the surface being anodized;
  • FIG. 3 is a schematic diagram illustrating a circuit arrangement for providing each of the plurality of cathode elements with a constant current density
  • FIG. 4 is a schematic diagram of a circuit capable of functioning as the series isolation element illustrated in FIG. 3.
  • FIG. l there is diagrammatically illustrated an anodizing system comprising a metal strip 10, such as aluminum, which is connected to a suitable voltage source (-l) so as to serve as an anode.
  • a suitable voltage source -l
  • the strip 10 is the material to be anodized.
  • a plurality of spaced cathode elements 12 are positioned in close proximity to the surface of strip 10.
  • yElements 12 are individually connected to a source of constant current as is schematically depicted by each element being connected to a separate voltage source
  • An electrolyte is passed between strip lil and the cathode elements 12 as indicated by the arrowheads. In the present invention, the electrolyte must flow at high velocity in order to remove the heat generated by the large current densities employed.
  • the cathode elements 12 are individually dimensioned so as to cover only a portion of the strip 10. Since these elements are closely spaced with respect to the strip, each element participates in the anodizing of only a particular localized area of the strip. Thus, as the strip and the cathode elements are moved relative to one another, the strip is completely anodized by the cumulative effect of the separate anodizations involving each of the elements 12.
  • the cathode elements are arranged in staggered groups, these groups being indicated by the dash lines extending transversely of the length of strip l. In the illustrative embodiment, ve such groups are shown.
  • FIG. 2 depicts the relative spacing relationship which exists between adjacent cathode elements and between the anode and cathode elements so as to achieve electrical isolation of each element.
  • this gure depicts the anodizing system as part of a complete electrolytic cell.
  • the cell includes a tank structure 14 having side walls and a bottom formed of suitable material to resist attack by the electrolyte which is passed at high velocity through the tank.
  • Tank 14 includes a cover member 16 within which the cathode elements 12 are embedded such that a surface of each cathode is exposed to the electrolyte within the tank. Only one group of cathode elements is viewable in FIG. 2.
  • the individual elements 12 are spaced from one another by a distance x which is .greater than the distance y between the cathode elements and the anode 'within the cell. Similarly the spacing between cathode elements of adjacent groups is greater than the distance y.
  • each element is substantially independent of the anodizing activity of adjacent cathodes. Consequently, by proper selective positioning of cathode elements relative to one another, an anodized layer of constant thickness can be developed as the anode and cathode elements are moved relative to one another.
  • a cathode element may have a linear size in the range of 1/2l in the major dimensions forming the cathodic surface.
  • the spacing of such an element from the anode should be less than 1A". In practice, a distance of approximately s" has proved satisfactory. A spacing of approximately 1/2 between adjacent cathode elements is also appropriate in systems utilizing the dimensions just cited.
  • the invention requires that each of the cathode elements be electrically isolated from one another. This prevents chtesirable results experienced by prior art arrangements wherein the current path from a large cathode area is directed to a localized anode area having a lower resistivity than the surrounding anode portions with the resultant adverse effect that a disproportionate current density condition exists causing uneven anodization and burning problems.
  • the present invention provides constant current density for each cathode element. Since these elements are selectively positioned with respect to the anode and one another, anode current flow via a cathode element other than that immediately adjacent the area being anodized is prevented, thereby contributing to constant anodization thickness and reduction of burning.
  • FIG. 3 One type of circuit capable of providing constant current density for each cathode element 12 is illustrated in FIG. 3.
  • This circuit includes a constant voltage supply 18 across which a potentiometer 20 is connected.
  • potentiometer is at the apex of a pyramid of voltage dividers.
  • the voltage taken from potentiometer 20 serves as the total voltage across potentiometers 22, 24 and 26 at a level in the pyramid below potentiometer 20.
  • the voltages picked off each of the potentiometers 22, 24 and 26 serve as the respective total voltages across separate groups of three additional potentiometers at the next lower level of the pyramid.
  • the voltage taken from potentiometer 22 is connected across potentiometers 28, 30 and 32.
  • the output circuits of potentiometers 20, 22, 24 and 26 shown in FIG. 3 includes buffer arrangements. These are conventional unit-gain, non-inverting isolators, the purpose of which is to prevent the operation of portions of the overall arrangement of FIG. 3 from overloading other portions of the circuit. ln each of the output circuits from potentiometers 28, 30, 32, etc., a series isolation element (SIE) has been provided. This circuit insures the operation of its associated cathode element at a prescribed current regardless of variations in anodizing voltage at the cathode, or of voltage variations at the power supply. The details of a typical series isolation element will hereinafter be described with reference to FIG. 4.
  • SIE series isolation element
  • FIG. 4 illustrates a circuitry arrangement which may be utilized as the series isolation element of FIG. 3.
  • the circuit includes a driver transistor TR-1 of the NPN type to the base of which the top of its associated voltage divider pyramid potentiometer is connected.
  • a PNP type transistor TR-Z is interconnected with transistor TR-l. More particularly7 the emitter and collector of TR-l are respectively joined to the collector and base of TR-Z.
  • the collector of transistor TR-2 is connected through a resistor R-1 to the negative terminal of the power supply illustrated in FIG. 3. This terminal is also joined through a resistor R-2 to the base of transistor T R-l.
  • Suitable resistors R-3 and R-4 are interposed between the emitter and base, respectively, of transistor TR-2 and a cathode element 12.
  • the circuit of FIG. 4 operates so as to maintain the voltage across resistor R-l constant. This is accomplished 'by the compensating operation of transistor TR-2 to changes in the conduction of transistor TR-l.
  • the operating details of this circuit are well known and therefore need not be described further. It is sufficient to say that the output current to the cathode element 12 is maintained substantially constant by the series isolation element independently of changes in the supply voltage of the cathode-to-anode resistance.
  • circuitry described with respect to FIGS. 3 and 4 has been presented for illustrative purposes only. A number of other conventional circuit arrangements may be employed so as to regulate and distribute the anodizing current such that the current is unaffected by voltage variations at the cathode elements or at the power supply.
  • said cathode comprises a plurality of elements spaced from one another and from said surface, said elements being positioned so that moving strip Will be closer to said elements than the spacing between said elements, the elements being dimensioned to substantially restrict each elment to participation in the anodization of only a portion of said surface; and means individual to each of said elements for supplying current at adjustable constant current density between an element and the portion of said surface proximate said element whereby the cumulative 6 effect of anodizing the portions of said surface is 3,240,685 3/ 1966 Maissel 204-224 XR the uniform anodization of said surface. 3,361,662 1/ 1968 Sutch 2.04-224 2.
  • Gerhard 204--224 XR said elements are arranged in groups, the elements of one group being positioned in staggered relationship JOHN H. M ACK, primary Examiner with respect to elements of an adjacent group.

Landscapes

  • 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)
  • Electrolytic Production Of Metals (AREA)
US632632A 1967-04-21 1967-04-21 Electrical system for anodizing Expired - Lifetime US3522166A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US63263267A 1967-04-21 1967-04-21

Publications (1)

Publication Number Publication Date
US3522166A true US3522166A (en) 1970-07-28

Family

ID=24536302

Family Applications (1)

Application Number Title Priority Date Filing Date
US632632A Expired - Lifetime US3522166A (en) 1967-04-21 1967-04-21 Electrical system for anodizing

Country Status (2)

Country Link
US (1) US3522166A (enrdf_load_stackoverflow)
GB (1) GB1229423A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969211A (en) * 1974-06-08 1976-07-13 Pilot Man-Nen-Hitsu Kabushiki Kaisha Continuous apparatus for electrolytic treatment on a long structure of aluminum or its alloys
US4177127A (en) * 1973-08-13 1979-12-04 Swiss Aluminium Ltd. Device for the production of anodized material
US4604341A (en) * 1983-08-03 1986-08-05 Hoechst Aktiengesellschaft Process for the one-stage anodic oxidation of aluminum bases for offset printing plates and product thereof
US4721554A (en) * 1984-10-31 1988-01-26 Inovan-Stroebe Gmbh & Co. Kg. Electroplating apparatus
US5322614A (en) * 1989-01-21 1994-06-21 May Hans J Device for electrolytic deposition of metals on one or both sides of strips

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3008892A (en) * 1957-09-10 1961-11-14 United States Steel Corp Apparatus for coating selected portions of the surface of a base material
US3132080A (en) * 1960-10-26 1964-05-05 Thompson Ramo Wooldridge Inc Electroplating method and apparatus
US3240685A (en) * 1962-02-23 1966-03-15 Ibm Method and device for selective anodization
US3361662A (en) * 1964-02-20 1968-01-02 Western Electric Co Anodizing apparatus
US3391065A (en) * 1966-02-09 1968-07-02 Western Electric Co Method and apparatus for selective anodizing of metallized substrates

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3008892A (en) * 1957-09-10 1961-11-14 United States Steel Corp Apparatus for coating selected portions of the surface of a base material
US3132080A (en) * 1960-10-26 1964-05-05 Thompson Ramo Wooldridge Inc Electroplating method and apparatus
US3240685A (en) * 1962-02-23 1966-03-15 Ibm Method and device for selective anodization
US3361662A (en) * 1964-02-20 1968-01-02 Western Electric Co Anodizing apparatus
US3391065A (en) * 1966-02-09 1968-07-02 Western Electric Co Method and apparatus for selective anodizing of metallized substrates

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4177127A (en) * 1973-08-13 1979-12-04 Swiss Aluminium Ltd. Device for the production of anodized material
US3969211A (en) * 1974-06-08 1976-07-13 Pilot Man-Nen-Hitsu Kabushiki Kaisha Continuous apparatus for electrolytic treatment on a long structure of aluminum or its alloys
US4604341A (en) * 1983-08-03 1986-08-05 Hoechst Aktiengesellschaft Process for the one-stage anodic oxidation of aluminum bases for offset printing plates and product thereof
US4721554A (en) * 1984-10-31 1988-01-26 Inovan-Stroebe Gmbh & Co. Kg. Electroplating apparatus
US5322614A (en) * 1989-01-21 1994-06-21 May Hans J Device for electrolytic deposition of metals on one or both sides of strips

Also Published As

Publication number Publication date
GB1229423A (enrdf_load_stackoverflow) 1971-04-21

Similar Documents

Publication Publication Date Title
US3862891A (en) Uniform plating current apparatus and method
US4534832A (en) Arrangement and method for current density control in electroplating
KR100866821B1 (ko) 전해 처리 시스템을 위한 분할된 상대전극
ES339386A1 (es) Aparato para utilizar en la fabricacion de vidrio plano.
EP0030227A2 (en) Method and apparatus for electrolytically treating a metal strip
US3522166A (en) Electrical system for anodizing
GB1504332A (en) Method and apparatus for the electrodeposition of metal
US3798407A (en) Process for welding sheet metal coated with layers
US3470082A (en) Electroplating method and system
JPH04143299A (ja) 電解メッキ方法
US4347115A (en) Electroplating apparatus
US6217736B1 (en) Method and apparatus for electrolytically treating a board-shaped substrate comprising shielding edge regions of the substrate during electrolytic treatment
JPS56102597A (en) Plating device
CN201016123Y (zh) 用于柔性电路板电镀工艺的阴极挡板结构
JPH01119699A (ja) 電解浴中の部分電流を調整する方法および装置
US3743881A (en) Self stabilizing electrodes
GB1081858A (en) A method of testing the continuity of a layer of electrically resistive material
US3880721A (en) Method for reducing (pseudo-) ohmic overpotential at gas-evolving electrodes
AU2013492A (en) Electrolysis cell for gas-emitting or gas-dissipating electrolytic processes and process for running the electrolysis cell
US4459194A (en) Electroplating apparatus
US3445371A (en) Anode structure for continuous strip electroplating
US2974098A (en) Rod and plate electrode assembly
ATE108839T1 (de) Elektrodenanordnung für elektrolytische zwecke.
US2761830A (en) Wiring arrangement for a series of electrolytic cells
SE443477B (sv) Med ljus tendbar tyristor bestaende av huvud- och en for tendforsterkning integrerad hjelptyristor