US3502563A - Control of electrodeposits - Google Patents

Control of electrodeposits Download PDF

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Publication number
US3502563A
US3502563A US470330A US3502563DA US3502563A US 3502563 A US3502563 A US 3502563A US 470330 A US470330 A US 470330A US 3502563D A US3502563D A US 3502563DA US 3502563 A US3502563 A US 3502563A
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Prior art keywords
deposit
suspension
pigment
strip
voltage
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Expired - Lifetime
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US470330A
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English (en)
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Francis J Schmidt
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General Electric Co
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General Electric Co
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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
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/22—Servicing or operating apparatus or multistep processes

Definitions

  • This invention pertains to the art of depositing materials by the action of an applied electric field, and generally to the coating art. It is a continuation-in-part of my application for United States patent entitled Control ofComposition of Electrodeposits, filed Dec. 19, 1963, Ser. No. 331,766, and now abandoned, which application is assigned to the assignee of the present application.
  • the prior art generally is concerned with the deposition only of particles of a single kind (as in coating and spray painting) or with the most complete possible deposition of all the material, of whatever kind, in a given suspension (as in dust precipitation).
  • One of the benefits of such control in a coating operation is that a dispersion of pigments of different colors may be employed to produce coatings. whose color is adjustable at will within limits determined by the colors of the different components.
  • any desired characteristics of an electrodeposit may be controlled by the ratio of different components, such control is useful.
  • it is useful to control the appearance of the deposit either to produce deposits of somewhat different appearances from a suspension of given characteristics, or to produce on successively coated work pieces deposits of like appearance despite the depletion of the suspension, or variations in the temperature of the suspension, or other changes which may occur during the course of Work.
  • My invention depends upon the discovery that for different materials dispersed in the same fluid medium, the velocities with which the different materials move in an applied electric field are apparently dilferent non-linear functions of the magnitude of the field.
  • my invention I have found that, if deposition in a given electric field from a mixture of two different colloidal materials produces a deposit containing a given proportion of the two materials, an increase in the electric field will increase the rate of deposition of one material more than the rate of deposition of the other material and so change that given proportion.
  • FIG. 1 there is represented a container 12,which may conveniently be of glass for small samples, or of any mechanically suitable non-conductor which is not attacked by the suspending medium, for large work.
  • Two electrical connectors 14 and 16 which may conveniently be conventional busbars, are represented located at the upper end of container 12.
  • counterelectrode 18, which may be of any convenient metal not attacked by the suspending medium, is represented suspended from connector 14.
  • From connector 16 there are suspended one or more clips 20 which serve to hold and make connection to work piece 22.
  • Conductors 24 and 26 connect connectors 14 and 16, respectively, to a conventional polarityreversing double-pole double-throw switch 28.
  • Switch 28 is further connected by conductors 30 and 32 to an adjustable constant-potential source 34 whose output potential may be observed by voltmeter 36.
  • counterelectrode 18 should ordinarily be so shaped as to produce a substantially uniform field normal to the workpiece 22. This has been achieved, for planar workpiece 22, by making counterelectrode 18 also planar. If, however, special decorative or other efiects are sought, it is possible to produce variation in the color or other characteristics of the deposit over the face of the workpiece by so shaping the counterelectrode as to produce different field intensities over the surface of the workpiece.
  • the effect of electrode shape upon field density is, of course, part of the well-known art of electricity.
  • Pieces three inches square and one-sixteenth of an inch thick were anodized for forty-five minutes in a twentyfive percent by weight aqueous solution of sulphuric acid at a current density of 50 amperes per square foot at 20 C., the bath being cooled to maintain the temperature. These were then rinsed in water and allowed to dry.
  • FIG. 2 there'is represented a supply reel 38 of anodized strip 40.
  • a tank or container 42 of somesuitable insulating material, is represented in section to permit viewing of its interior.
  • Supported across the top of tank '42 are busbars 44 and which support counterelectrode 48.
  • This counterelectrode 48 is so shaped as to provide an approximately constant gap between its inner surface and strip 40 as the latter passes from supply reel 38 down into the tank 42, around roller 50, and-back up out of the tank around roller 52.
  • the tank 42 is represented .aslfilled with a suspension 54 which is here represented, for convenience, as transparent, although it will infact probably, be opaque or translucent.
  • Suspension 54 immersesroller 50: and partsof counterelectrode 48 and strip 40.
  • a schematic representation of a scraper blade assembly56 is provided to indicate a convenient means of assuring that the surface of roller 50 will not acquire, anobjectionably thick layer of deposited mate rial.
  • roller 50 is of electrically conductive material, there :will be'a certaiii tendency forelectrophoreticdeposition to occur upon it; but thefield at its surface will be very much weaker than that at the surface of strip 40, and the deposition will be at a very low rate. Since the surface of roller may be smooth, such a deposit will easily be removed by a scraper such as is represented by assembly 56.
  • roller 50 is made with a thick surface of electrically nonconductive material, the tendency to deposition will be even more reduced. If roller 50 is of metal, scraper assembly 56 might be used to make. electrical contact to the roller 50, which would then afford electrical connection to strip 40; but I have represented instead a roller 58 which is maintained in contact with the edge of strip 40, and which rotates in pillow blocks 60 which may be graphite-lubricated and thus can provide electrical connection to the roller 50 and thence to strip 40. If necessary, a thin sliver may be slit from the edge of strip 40, after anodizing, to expose the base metal. Alternatively, brush connections may be made at supply reel 38 to the end of strip 40. The currents involved in electrophoresis are quite small and the problems of making adequate contact to the workpiece are not nearly so severe as in conventional electroplating.
  • Bus bar 46 is connected to conductor 62, and pillow block 60 is connected to conductor 64. These conductors 62 and 64 are connected to the output of controllable potential supply 66, the term potential supply being used as in connection with FIG. 1, to emphasize the importance of potential as the primary parameter. While it is evident that the connections described will cause electrophoresis to occur in tank 42, detailed description will be deferred pending completion of the description of the apparatus train through which strip 40 passes.
  • strip 40 passes to a sealing-and-washing installation comprising a washer 68 (represented as comprising a housing 70 and a plurality of nozzles 72) and a tunnel furnace 74 (represented as comprising a refractory housing 76 and heating elements 78).
  • a washer 68 represented as comprising a housing 70 and a plurality of nozzles 72
  • a tunnel furnace 74 represented as comprising a refractory housing 76 and heating elements 78.
  • the strip After passing first through the furnace 74 for sealing and then through the washer 68 for removal of adherent excess pigment, the strip passes a spectroreflectometer assembly 80, which is schematically represented as comprising: a light source 82 and a condensing lens 84 which focusses the light from source 82 upon the under side of strip 40; and a converging lens 86 which, through a filter 88, focusses light reflected from the under side of strip 40 upon the sensitive surface of a photosensitive element 90, which may be a ph0todiode, barrier-layer photocell, vacuum photocell, or other conventional device.
  • Photosensitive element 90 is connected by conductors 92 and 94 to the input of control amplifier 96, whose output is connected by conductors 98 and 100 to the control terminals of controllablepotential supply 66.
  • the strip 40 passes to storage reel 104.
  • Mechanical mounting means, such as bearings, for the various rollers, and drive means such as electric .motors have not been represented because these are part of a very old and wellknown art, and to represent them would merely divert attention from the more significant features of the drawing.
  • the particular arrangement of bearings and motors will depend very largely upon the designers choice, and a particular arbitrary representationof bearings, brackets, and motors would be most unlikely to bear, the design chosen in a particular,
  • Anodized strip 40 from the store on supply reel 38 passes roller 58 and descends into tank 42, entering suspension 54 and passinginproximity to counterelectrode 48, moving aroundroller 50.
  • Controllae ble potential supply 66 via conductor 62 and busbar 46 on the one side, and via conductor 64, pillow block 60, and roller 58 on the other side, maintains a potential difference between counterelectrode 48 and substrate electrode strip 40 of proper sign to producean electrodeposit in the anodized surface of strip 40. With the counterelectrode geometry represented, this deposition will occur primarily upon the face of strip nearer to counterelectrode 48.
  • Strip 4% now passes sensing station 102, where light from source 82 is focussed by lens 84 upon the surface of strip 40 which was nearer to counterelectrode 48 during the strips passage through tank 42 and is therefore more heavily coated. Light reflected from the strip is focussed by lens 86 upon photosensitive device 90; but filter 88 transmits only a part of the spectrum.
  • suspension 54 contains a mixture of blue and yellow pigments, and that it is desired to deposit a particular shade of green coating. in the example given in connection with the description of FIG. I, it was indicated that increasing the voltage used for electrophoresis increased the proportion of blue pigment deposited.
  • control amplifier 96 must be so designed that, responsively to such an input signal, it applies via conductors 98 and 100, a signal to controllable potential supply 66 such as to decrease its output potential, which is applied to the electrophoretic process. If filter 88 had been chosen to transmit primarily yellow light, the phasing or other interconnection of amplifier 96 and potential supply 66 would have to be such that increased illumination on photosensitive device 90 would cause an increase in the output potential of supply 66.
  • the apparatus will still function as follows: Let the pigment be, for example, Indofast brilliant scarlet pigment, which (as has been shown) produces a darker colored deposit the higher the voltage used to deposit it. If filter 88 is omitted entirely, the light falling upon photosensitive device 90 will decrease if the voltage front controllable potential supply 66 is increased, since there will result a darker deposit which will reflect less light. If, for any other reason, the density of the deposit of pigment should increase the light falling upon photosensitive device 90 will similarly decrease. This will increase the electrical output applied from device 90 via conductors 92 and 94 to the input of control amplifier 96.
  • the pigment for example, Indofast brilliant scarlet pigment, which (as has been shown) produces a darker colored deposit the higher the voltage used to deposit it. If filter 88 is omitted entirely, the light falling upon photosensitive device 90 will decrease if the voltage front controllable potential supply 66 is increased, since there will result a darker deposit which will reflect less light. If, for any other reason, the density of the deposit of pigment should increase the
  • filter 85 may be replaced by one having a different spectral characteristic; or the initial voltage setting of controllable potential supply 66 and/or the gain of control amplifier 96 may be varied.
  • auxiliaries which maybe useful in particular instances. For instance, it may be convenient to provide a circulator in tank 42 to prevent extreme local depletion of suspension 54 in the vicinity of the electrodes; or it may be useful to provide automatic me'ansfor monitoring the concentration of suspension 54 and for adding more pigments in an auxiliary tank connected with tank 42 and provided with a suitablesuspending device such as an ultrasonic oscillator.
  • auxilia'ries are part' of known art, and not necessary to be shown to disclose my teachings. i
  • the effect of variation in the current density employed in the anodizing process is not particularly a deterrent in the application of the process, as it is conventional in anodizing to control the anodizing current at a fixed value to produce the desired physical characteristics in the anodized surface, and minor variations in the anodizing current may be compensated by varying the voltage used in electrophoresis. It is hypothesized that the change in porosity produced by major changes in the anodizing current causes changes in the color observed in the electrophoretic deposit through altering the electric field existing at the outer part of the anodized surface where pigment deposition occurs, or by altering the size of the pores, with consequent alteration in the size of the aggregates of pigment formed therein.
  • any material suitable for electrophoretic deposition may be used with any suitable substrate electrode.
  • apparatus for controlled electrophoresis of colloidally dispersed material comprising:
  • (0) means to support a substrate electrode in said container
  • adjustable potential supply means connected to said counterelectrode means and adapted to be connected to said substrate electrode to apply a potential therebetween;
  • sensing means adapted to sense a parameter characteristic of the light reflectivity of an electrophoretically produced deposit of the said material which parameter is a function of the potential used to produce the said deposit;
  • the improvement comprising (f) connecting means connecting the said sensing means to the said adjustable potential supply means to adjust the said potential responsively to the value of the said parameter sensed by the said sensing means.
  • apparatus for controlled electrophoresis of colloidally dispersed material comprising:
  • adjustable potential supply means connected to said counterelectrode means and adapted to be connected to said substrate electrode to apply a potential therebetween;
  • sensing means adapted to sense a parameter characteristic of the color of an electrophoretically produced deposit of the said material which parameter is a function of the potential used to produce the said deposit;
  • sensing means adapted to sense a parameter characteristic of the color of an electrophoretically deposited mixture of the said materials which parameter is a function of the relative proportion in the said mixture of the materials comprised in the said plurality;

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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)
  • Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
  • Paints Or Removers (AREA)
US470330A 1965-06-29 1965-06-29 Control of electrodeposits Expired - Lifetime US3502563A (en)

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NO (1) NO117100B (pm)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3627661A (en) * 1969-02-13 1971-12-14 Ransburg Electro Coating Corp Electronic apparatus and method
US4102771A (en) * 1974-10-28 1978-07-25 Vianova Kunstharz, A.G. Measuring device and process for recording on electrodeposition parameters of throwing power
US4210505A (en) * 1978-11-14 1980-07-01 Shinto Paint Co., Ltd. Method and apparatus for electrodeposition coating
US4270317A (en) * 1978-10-10 1981-06-02 Midland-Ross Corporation Apparatus used in the treatment of a continuous strip of metal and method of use thereof
US4306958A (en) * 1979-11-13 1981-12-22 Olympus Optical Co., Ltd. Coloring-decoloring-drying apparatus for electrophoresis
US4317710A (en) * 1979-10-18 1982-03-02 Olympus Optical Co., Ltd. Coloring-decoloring-drying apparatus for electrophoresis
US6607645B1 (en) 2000-05-10 2003-08-19 Alberta Research Council Inc. Production of hollow ceramic membranes by electrophoretic deposition
US20080311362A1 (en) * 2007-03-16 2008-12-18 Suddeutsche Aluminium Manufaktur Gmbh Partial pigmentation of a coating layer to prevent interference on aluminum components or components comprising aluminum

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2898279A (en) * 1956-06-14 1959-08-04 Commw Of Australia Coating surfaces by employing an electrostatic field
US2956905A (en) * 1956-06-22 1960-10-18 British Cotton Ind Res Assoc Method and means for the automatic regulation of the continuous application of specified amounts of solids or liquids to a moving sheet of material
US2973686A (en) * 1957-10-11 1961-03-07 Gen Precision Inc Apparatus for spectrophotometric monitoring of thin film coatings
US3067123A (en) * 1958-12-17 1962-12-04 Huber Willy Apparatus for regulating current density and other factors in an electrolytic bath
US3077858A (en) * 1960-03-17 1963-02-19 Gen Electric Canada Apparatus for controlling and measuring the thickness of thin electrically conductive films
US3081194A (en) * 1959-08-07 1963-03-12 Gen Motors Corp Plating thickness indicating apparatus and method
US3145156A (en) * 1961-11-15 1964-08-18 Carter S Ink Co Electrophoretic printing
US3157535A (en) * 1962-01-15 1964-11-17 Lear Siegler Inc Monitoring apparatus for automatic production of microcircuits

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2898279A (en) * 1956-06-14 1959-08-04 Commw Of Australia Coating surfaces by employing an electrostatic field
US2956905A (en) * 1956-06-22 1960-10-18 British Cotton Ind Res Assoc Method and means for the automatic regulation of the continuous application of specified amounts of solids or liquids to a moving sheet of material
US2973686A (en) * 1957-10-11 1961-03-07 Gen Precision Inc Apparatus for spectrophotometric monitoring of thin film coatings
US3067123A (en) * 1958-12-17 1962-12-04 Huber Willy Apparatus for regulating current density and other factors in an electrolytic bath
US3081194A (en) * 1959-08-07 1963-03-12 Gen Motors Corp Plating thickness indicating apparatus and method
US3077858A (en) * 1960-03-17 1963-02-19 Gen Electric Canada Apparatus for controlling and measuring the thickness of thin electrically conductive films
US3145156A (en) * 1961-11-15 1964-08-18 Carter S Ink Co Electrophoretic printing
US3157535A (en) * 1962-01-15 1964-11-17 Lear Siegler Inc Monitoring apparatus for automatic production of microcircuits

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3627661A (en) * 1969-02-13 1971-12-14 Ransburg Electro Coating Corp Electronic apparatus and method
US4102771A (en) * 1974-10-28 1978-07-25 Vianova Kunstharz, A.G. Measuring device and process for recording on electrodeposition parameters of throwing power
US4270317A (en) * 1978-10-10 1981-06-02 Midland-Ross Corporation Apparatus used in the treatment of a continuous strip of metal and method of use thereof
US4210505A (en) * 1978-11-14 1980-07-01 Shinto Paint Co., Ltd. Method and apparatus for electrodeposition coating
US4317710A (en) * 1979-10-18 1982-03-02 Olympus Optical Co., Ltd. Coloring-decoloring-drying apparatus for electrophoresis
US4306958A (en) * 1979-11-13 1981-12-22 Olympus Optical Co., Ltd. Coloring-decoloring-drying apparatus for electrophoresis
US6607645B1 (en) 2000-05-10 2003-08-19 Alberta Research Council Inc. Production of hollow ceramic membranes by electrophoretic deposition
US20080311362A1 (en) * 2007-03-16 2008-12-18 Suddeutsche Aluminium Manufaktur Gmbh Partial pigmentation of a coating layer to prevent interference on aluminum components or components comprising aluminum
US8747641B2 (en) * 2007-03-16 2014-06-10 Suddeutsche Aluminium Manufaktur Gmbh Partial pigmentation of a coating layer to prevent interference on aluminum components or components comprising aluminum

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Publication number Publication date
CH489615A (de) 1970-04-30
NO117100B (pm) 1969-06-30
NL6601626A (pm) 1966-12-30
BE683379A (pm) 1966-12-01

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