US3622471A - Production of inorganically colored coatings on aluminum - Google Patents

Production of inorganically colored coatings on aluminum Download PDF

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US3622471A
US3622471A US742000A US3622471DA US3622471A US 3622471 A US3622471 A US 3622471A US 742000 A US742000 A US 742000A US 3622471D A US3622471D A US 3622471DA US 3622471 A US3622471 A US 3622471A
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current
alternating current
elements
electrode
workload
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William Ernest Cooke
Paul John Sajben
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Alcan Research and Development Ltd
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Alcan Research and Development Ltd
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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
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/20—Electrolytic after-treatment
    • C25D11/22—Electrolytic after-treatment for colouring layers
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S204/00—Chemistry: electrical and wave energy
    • Y10S204/07—Current distribution within the bath

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  • inorganically colored coatings are produced by first anodizing an aluminum article, as in sulfuric acid solution, to form an anodic coating, and then subjecting the anodized article to electrolytic treatment with alternating current in an acidic bath containing metal ions selected from the group consisting of the following cations and anions: Ni, Co, F e, Cu, Agfi Cd, Zn, Pb, and anions consisting of oxygen combined with one of the metals Se, Te and Mn.
  • metal ions selected from the group consisting of the following cations and anions: Ni, Co, F e, Cu, Agfi Cd, Zn, Pb, and anions consisting of oxygen combined with one of the metals Se, Te and Mn.
  • the patent further states that by the described process there is deposited in the anodic coating the oxide or hydroxide of metal of the selected ions, i.e. such metal in chemical combination with oxygen, resulting in a colored coating which can be sealed and which has good permanence.
  • the present improvements are specifically related to the step of electrolytic treatment with alternating current passing between the anodized work and a couterelectrode, e.g. a metal electrode, whereby a colored deposit is effected in the anodic coating, resulting from metal of the selected ions, and important aims of the improved method and apparatus are to promote achievement of selected colors or tones, without defects and in a reproducible manner, and to attain a new and simplified mode of control for applying any desired shade of a given color or metal oxide deposit.
  • a couterelectrode e.g. a metal electrode
  • Requisite control has sometimes been found very delicate, notably in making voltage adjustment in the case of copper; for example in utilizing a bath containing copper ions and passing AC between the anodized work and a copper sheet electrode, it has been difficult even to obtain a medium shade, e.g. maroon or the like, as distinguished from a pale tone or a near-black or black.
  • a medium shade e.g. maroon or the like
  • a primary object of the present invention is to improve the operation in one or more or indeed all of these respects, so as to facilitate the attainment of desired colors, in a consistent manner.
  • Another significant object is to provide improvement in control, and in a different manner than by the selection or adjustment of both the voltage of the applied alternating current and the time of treatment as heretofore practiced. the ef fect of the improved control being to obviate or minimize situations of poor matching or nonreproducibility where such may tend to occur, and also, in presently preferred operation, to permit achievement of a selected shade of color essentially only in accordance with duration of treatment.
  • the actual effective, current-passing area of the counterelectrode is only a minor fraction of the total area over which such electrode elements are distributed or the corresponding total external area of the anodized workload surface that more or less faces the counterelectrode (or is affected by flow of current to and from the electrode) and that is to be colored.
  • the electrode assembly which may appropriately be made of the same metal as the selected ions in the bath, can be fashioned in various ways to afford the spaced, distributed structure.
  • a convenient arrangement consists of an array of parallel, vertical strips, rods or tubes of the stated metal, or like pieces such as the connected elements of a continuous grid, screen or the like, disposed in the tank so as to define a selected vertical plane and having relatively wide spacing, i.e. a distance between successive pieces which may be as much as several times the transverse dimension of the effective, current-passing surface of each piece, conveniently at least four times and most preferably more.
  • This arrangement is especially adapted for use in establishments having conventional anodizing operations, the coloring step being effected in an elongated tank similar to the tanks used for such operations, and constructed to receive workloads, for treatment, in submerged relation at one or more longitudinal regions parallel to the sides of the tank.
  • a workload which has been previously anodized
  • a workload consisting of a sheet or sheets of aluminum, or a collection of rods, bars or various shapes or other articles of aluminum (e.g. as carried on a rack)
  • an electrode structure consisting of the novel assembly or array of spaced, narrow, metallic elements.
  • a very important aspect of the invention resides in the complete process or procedural combination that involves a mode of electrical control which is novel for the described AC coloring step and is cooperatively related to the above concept of employing a multiplicity of counterelectrode elements or surfaces, indeed in being available or feasible, according to present understanding, only when such arrangement or feature respecting the counterelectrode is employed. Specifically it has been discovered that under such circumstances, an unusually effective control of the coloring step is achieved by controlling the electrical current so as to maintain a selected value or values thereof.
  • a mode of operation presently found of special advantage is to regulate the electrical system so that for a given workload a selected value of current is maintained throughout the interval of treatment. More particularly, the stated electrical control is directed to the current density at the surface of the work, i.e. whether for designed change, program or preferably a single constant value; it will be appreciated that for each workload the actual current value condition, or each such condition, to be maintained is determined upon merely multiplying the total work surface area under treatment by the desired current density, or each such density, as measured for instance in amperes per unit area.
  • the results of treatment are exceptionally reliable and reproducible, and indeed can in most cases be such that a given shade or color, in a given metal-containing bath, is attained simply in accordance with the duration of treatment. It appears, for example, that nonuniformity previously encountered among different workloads is probably occasioned by variation in polarization at the counterelectrode; tests in the case of AC treatment with a nickel bath using a nickel electrode have shown mismatch of color between workloads with different surface areas, even though the externally applied voltage and time of operation were the same.
  • FIG. 1 is a simplified view, in perspective, of a tank for the coloring step, with parts broken away, and with accompanying diagram of electrical supply and control;
  • FIG. 2 is a transverse vertical section as on the plane 2-2, of FIG. 1, including the coloring bath;
  • FIG. 3 is a schematic plan view of a tank and operation as in FIG. 1, utilizing a different workload
  • FIG. 4 is a vertical section similar to FIG. 2, but of apparatus for handling two workloads in parallel;
  • FIG. 5 is a schematic plan view of the tank and operation of FIG. 4;
  • FIG. 6 is a partial view, in perspective, of a portion of tank such as in preceding figures, showing electrode-supporting means;
  • FIG. 7 is a fragmentary vertical section on line 7-7 of FIG. 6;
  • FIG. 8 is a fragmentary vertical section on line 8-8 of FIG. 6.
  • the work is first anodized in a conventional manner to produce an anodic oxide coating, for example of a sort customarily employed for protective or like purposes. While any of a considerable variety of known operations for this purpose may be employed, as with various electrolytes of which aqueous solutions of sulfuric acid, chromic acid, sulfonic acid such as sulfosalicyclic acid, and suitable mixtures of these with other acids or compounds are examples, and while in some cases AC anodizing treatment may be feasible, effective results are obtained by anodizing the work with direct current, as for periods of 20 to 60 minutes, in an aqueous solution of sulfuric acid, e.g. 15 percent acid by weight.
  • the conditions of the anodizing step do not appear to be critical, being selected largely to suit the thickness and other characteristics of anodic coating needed for protective function, the requirements of the subsequent coloring step being satisfied over a considerable range of thicknesses of porous oxide coating on aluminum.
  • a suitable tank 22 for the AC treatment to effect a colored deposit in the oxide coating on the sheet, e.g. a colored oxide or equivalent deposit of a selected metal.
  • the bath 23 in the tank 22 may contain ions of the selected metal, as for instance nickel, and the bath may be prepared in appropriate fashion, as set forth in the above-cited U.S. Pat. No. 3,382,160.
  • this should be an aqueous acidic solution and may comprise boric acid, nickel sulfate and ammonium sulfate, all in low concentration, and very preferably having a pH value, below neutrality, of at least about 4.
  • a pair of electrode assemblies 26, 27 are disposed inside the tank and in facing relation to the workload.
  • Each of these counterelectrodes may consist of an array of narrow metal electrode strips or like elements 28 carried respectively by and connected to bus bars 30, 31, whereby these electrode strips 28 extend vertically into the bath and are spaced, on each side, along a plane parallel to the work 20.
  • bus bars 30, 31 are connected together to one conductor 33 and the bus bar 24 of the work 20 is connected to another conductor 34, these conductors ultimately extending through conductors 35, 36 to receive alternating current from an electrical power source 37.
  • an electrical power source 37 As will be seen from FIGS. 1 and 2, such current is thus passed through the bath to and from the anodized work load 20 from and to the electrode assemblies 26, 27, and as has been explained above, the effect of such treatment, for instance with nickel ions in the bath, is to produce a characteristic colored deposit, presumably nickel oxide, in the anodic coating on the sheet 20.
  • the system includes provision for electrical control, to maintain a constant current between the workload and the counterelectrodes, thereby enabling the maintenance of a selected, constant current density at the surface of the workload 20.
  • FIG. 1 schematically shows current-controlling instrumentalities connected between the conductors 33, 34 and the conductors 35, 36 from the alternating current source 37.
  • control means may comprise an ammeter 40 of type suitable for the purpose and a current adjusting means 41, the ammeter having appropriate means (not shown) settable to be effective on departure from a selected current value for adjusting the instrumentality 41 to restore the current in the circuit 33, 34 to the selected value when it has departed therefrom in either direction.
  • the device 41 may be of the nature of a variable autotransformer that actually changes the output voltage in the supplied circuit, the control system is nevertheless related to current and functions to maintain the predetermined current as governed by the setting of the meter device 40.
  • the value of current to be maintained in the circuit 33, 34 is detennined by multiplying the total area of the work, being here both sides together, by the desired current density; the ammeter device 40 is then set to maintain the selected current.
  • the work may consist of a plurality of objects, possibly even or irregular shape, as carried on a rack which the central bus bar 24 supports, it is usually sufficient to make an approximate calculation of the total area of such work and of submerged parts of the anodized aluminum rack, for computation of the selected current value.
  • an optimum and notable useful value of current density for treatment with nickelcontaining baths is about 3 amperes per square foot; more generally, it appears that preferred results are attained under these circumstances by selecting a current density above about 2.5 amp./sq.ft. No advantage has been apparent for operation above about 3.5 amp./sq.ft. or indeed even that high, while substantially larger values may even be deleterious.
  • the basic value of 3 amp./sq.ft. appears to to have reasonable tolerance, in that as mentioned above departures within about 10 percent, as in calculating the area of a given workload, still provide a good color match between successive loads treated for the same length of time.
  • mismatch problems arising when control has been effected by voltage setting or settings may have been caused by polarization effects, e.g. at the counterelectrode especially in that such effects differ with different areas of workload, and possibly also in other ways.
  • the described current control appears to have a more direct relation to the coloring action of the treatment, and coacts in overcoming the problems, apparently in the sense that voltage difficulties due to polarization are automatically compensated.
  • the complete system involving the multiplicity of electrode elements and the described current control afl'ords optimum results in ameliorating or obviating such difficulty.
  • a setting of current is achieved, to provide a selected or optimum current density, and each shade or type of color is reproducibly obtained by choice of duration of treatment. It is conceived, of course, that in some cases a predetermined variation of current, or a program of current density control may be found desirable, for example two or more successive intervals of mutually different current density values; such mode of operation nevertheless realizes the basic advantages, described above, of using current conditions as the point of control.
  • FIGS. 6 to 8 illustrate, in somewhat simplified manner, one way of attaching the electrode strips 28.
  • the wall 42 of the tank 22 has an upper flange 43 to which the bus bar 30 may be secured by appropriate clamps 44.
  • the tank is suitably nonconducting and chemically inert as exposed to the electrolyte; for example, it may be constructed of mild steel or acid-resistant concrete, with an interior insulating lining (not here shown) of suitable resin, plastic or the like, e.g. synthetic rubber or polyvinyl chloride.
  • the upper ends of the metal electrode strips 28 are fastened to the bus bar, as by bolts and nuts as indicated at 46 in FIG. 7, while the lower ends of the strips extend through suitable openings in an angle member 48 having one of its webs 49 secured to the tank wall.
  • This member is preferably made of electrically and chemically resistant material, e.g. a plastic such as polyvinyl chloride, which permits fastening of the web 49 to the tank lining of like material by welding or fusion.
  • the ends of the strips 28 are held by a suitable pin or key 50 set in an opening in the strip and bearing on the underside of the flange of the angle 48.
  • rod or tubular electrode members can be similarly supported, and may have a nut (not shown) threaded below the flange 48 for similar retaining function. It will also be understood that where a central array of electrode elements, i.e. along the middle of the tank is used, as in FIGS. 4 and described below, a like supporting structure for hanging the strips from the bus bar and carrying their bottom ends by a longitudinal member supported on legs or other means above the tank bottom, may be utilized.
  • FIG. 3 is a diagrammatic plan view of a tank 22 such as shown in FIG. 1, with strip electrodes 28 along the sides, this figure showing a collection of anodized aluminum objects 52, 53 to be treated, these being supported by an appropriate rack or the like, indicated by the connecting bus bar 24a.
  • a number of dotted lines as at 54, 55 have been shown fanning out from the electrodes 28 toward the workpieces 52, 53, as an approximate representation of the manner in which it is understood that current flows between the work and the electrodes, in paths of substantial intensity. While these areas of current travel are probably not in practice as sharply defined as shown, it will be appreciated that the electrode structure thus distributes the current with considerable uniformity over the workload, whether such load comprises separate pieces 52, 53 as in FIG.
  • FIGS. 4 and 5 the latter being in diagram, show a tank 58, including its insulating lining 59, arranged to accommodate two workloads 60, 61, lengthwise thereof, with an array of metal electrode strips 62 down the middle between the localities occupied by the workloads.
  • Spaced metal electrode strips 28 are provided along the sidewalls, exactly as with the tank 22 of FIG.
  • the spacing of the electrode strips 62 is closer together than the side strips 28.
  • the central strips must deliver current from the respective faces in opposite directions to the workloads 60 and 61.
  • the side strips 28 can be considered as delivering current from both faces, including paths that bend around the strip, for travel to a single opposing face of the workload.
  • the spacing of the central elements 62 should be approximately one-half that of the outer elements and that each workload 60 or 61 can then be situated midway between the central and outer electrodes, it being understood that other adjustment for maintaining a uniform, effective current-passing area in the electrode systems, as by employing wider electrode strips along the middle, can be utilized.
  • the design of FIG. 5, with twice as many similar-sized strips in the center, is especially appropriate, tests indicating that with a full load of work 60, 61, the current is practically identical in each of the strips 28, 62, wherever located.
  • the electrode structures shown afford exceptionally good compensation or correction for the effects, presumably including edge effect, that now appear to have been responsible for some difficulty in certain applications of this electrolytic coloring step.
  • Rods, tubes or like elongated elements or corresponding grids of variously shaped pieces, preferably with large openings, may alternatively constitute the electrode structure.
  • the open arrangement illustrated is exceptionally simple and satisfactory, with advantages of economy as well as of a mechanical sort and of demonstrated ease of control. For instance, with widely spaced, narrow metal strips forming a central counterelectrode as at 62 in FIGS.
  • the supporting bus bar 64 can be much smaller in cross section (yet still have ample current capacity) than would be required to support a full sheet or plate electrode; economy of material results and likewise better clearance for insertion of workloads, especially racks of same.
  • the strips, e.g. of nickel or copper as appropriate, are also replaced with unusual ease and convenience when necessary, i.e. when consumed as a result of their function of supplying metal ions into the bath.
  • an important feature of all presently contemplated arrangements is that the above-mentioned edge efiect is nullified either by essentially eliminating sharp edges or by maximizing their composite action, e.g. in having so many of them that the radially directed current paths either collectively cover all areas of the work side-byside, or have a multiple overlap, the net result in all cases being substantial uniformity of current density throughout the faces of the workload.
  • the current paths 54, 55 in FIG. 3 show, approximately, how the edges of the individual strips can be considered as one, e.g. each strip 28 being roughly a line source of current, and how the spacing of the strips distributes the current over the work 20.
  • the spacing between work and counterelectrode is not especially critical and may conveniently agree with spacing used in conventional anodizing operations, e.g. from 6-inches to 2 feet, a distance of 9 to 12 inches or so affording a convenient balance between shortness of current paths and room to get workloads in and out of the tank.
  • the number of separate elements of the counterelectrode should be coordinated with the work-electrode distance, at least to insure substantially uniform and complete coverage of the workload region with paths of significant current flow from the electrode.
  • Some latitude of larger center-tocenter element spacing is possible in some instances, conceivably to as much as 50 percent more than the distance to the work, but for superior results the spacing of element centers should not in most cases be substantially more than about 1 foot, and generally less than 18 inches.
  • the actual, effective, i.e. current-passing area of the total of an array of elements should preferably be at least about 3 percent, and with special preference at least about 5 percent of the total space or area (measured as one side of it) over which the electrode elements are distributed.
  • the efiective area of an electrode element is generally intended to mean the total surface area from which current significantly flows to and from one facing workload; under such definition for example in FIG.
  • the total effective area of one of the arrays of outside strips 28 is the sum of the areas of both faces of such strips, while the total effective area of the center array of strips 62 relative to a single facing workload is the sum of the areas of one face of each of the latter strips.
  • the special advantages of an open counterelectrode assembly would appear to be best realized only when the total, effective, currentpassing area of the assembly relative to a facing workload is not more than 50 percent and with special preference nor more than about 25 percent of the total space, measured as the product of length by height, in which the elements are distributed.
  • the AC coloring step was practiced in a 4-foot-wide tank, a size conventional for anodizing and similar operations, using an acidic, nickel-containing, aqueous bath of the following composition, maintained at a pH of about 4 or above, eg 4 to 4.5:
  • Operation was first effected using counterelectrodes of essentially complete metallic nickel sheets, at the sides of the tank and along the center.
  • alternating current was passed through the bath between work and counterelectrodes, first at l 1 volts for 2 minutes, and then at 17 volts for minutes. The dark tone was reached, but the coating spalled, leaving small or minute bright spots, and other tests indicated that it was practically impossible to obtain more than a medium bronze color without spalling.
  • the sheet counterelectrodes were replaced with metallic nickel strips each xi-inch wide, arranged vertically as in the drawings, and with reference to FIG. 5, on 9-inch centers along the sides (strips 28) and on 4-l/2-inch centers along the center (strips 62). Operation was controlled to maintain a constant current, specifically to provide a density of 3 amperes per square foot of anodized surface of the workloads, such as anodized aluminum sheet. Under such conditions a highly desirable dark bronze color was obtained after a treatment time of 12 minutes and slightly darker (maximum) after minutes, with no spalling or other defect in either case. Tests also indicated that lighter shades were obtainable, reproducibly, at selected shorter times of treatment.
  • metal electrode elements especially nickel elements for nickel baths, copper for copper baths, and the like, as being a specific novel aspect of the invention
  • similar principles of providing uniform current distribution on the work are applicable to counterelectrodes of carbon, i.e. graphite, which can likewise be employed as widely spaced elements.
  • arrays of graphite rods or bars are governed by substantially the same criteria. provide effective operating conditions for the described novel current control
  • said electrode elements are metal electrode elements having a total efiective surface area for passage of current to said anodized surface equal to not more than about 25 percent of the area of said re gion in which said elements are distributed.
  • a method as defined in claim 4, which includes controlling said alternating current passing between said anodized surface and said electrode elements to provide a predetermined substantially constant current value during the time said current is passed, for maintaining a substantially constant current density at said anodized surface of about 3 amperes per square foot, to produce a colored deposit in said coating, of a shade dependent upon the duration of said time, and effecting said passage of alternating current for a time selected to produce a colored deposit of selected color shade in said coating.
  • a method as defined in claim 6, which includes controlling said alternating current passing between said anodized surface and said electrode elements to provide a predetermined substantially constant current value during the time said current is passed, for maintaining a substantially constant current density as said anodized surface of about 5 amperes per square foot, to produce a colored deposit in said coating, of a shade dependent upon the duration of said time, and effecting said passage of alternating current for a time selected to produce a colored deposit of selected shade in said coating.
  • said electrode elements are spaced apart by distances which are at least several times the transverse dimension of the effective current-passing surface of each element, said elements having a total effective current-passing area equal to not more than about 25 percent of the area of said region.

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Cited By (5)

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US3878056A (en) * 1973-08-24 1975-04-15 Sumitomo Chemical Co Process for electrolytic coloring of the anodic oxide film on a aluminum or aluminum base alloys
US3891517A (en) * 1973-03-20 1975-06-24 Sumitomo Chemical Co Process for electrolytic coloring of aluminum cr aluminum alloy articles
US20030112916A1 (en) * 2000-02-25 2003-06-19 Keeney Franklin W. Cold nuclear fusion under non-equilibrium conditions
US20100122908A1 (en) * 2008-11-18 2010-05-20 Spansion Llc Electroplating apparatus and method with uniformity improvement
US9975372B2 (en) 2016-06-21 2018-05-22 Charles White Multi-dimensional art works and methods

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IT1142650B (it) * 1981-12-31 1986-10-08 Grace Italiana Spa Impianto e procedimento perfezionato di elettrocolorazione dell'alluminio
CZ2023379A3 (cs) * 2023-10-09 2025-01-01 Acl Technology S.R.O. Zařízení pro elektrolytické barvení hliníku a jeho slitin

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GB190314823A (en) * 1903-07-03 1903-08-06 Harry Ellis Starrett Improvements in Metal Anodes.
US3382160A (en) * 1960-03-31 1968-05-07 Asada Tahei Process for inorganically coloring aluminum

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GB190200118A (en) * 1902-01-02 1902-03-20 Maurice D Andrimont Improvements in, or relating to Anodes for Electrolytic Operations
GB190314823A (en) * 1903-07-03 1903-08-06 Harry Ellis Starrett Improvements in Metal Anodes.
US3382160A (en) * 1960-03-31 1968-05-07 Asada Tahei Process for inorganically coloring aluminum

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3891517A (en) * 1973-03-20 1975-06-24 Sumitomo Chemical Co Process for electrolytic coloring of aluminum cr aluminum alloy articles
US3878056A (en) * 1973-08-24 1975-04-15 Sumitomo Chemical Co Process for electrolytic coloring of the anodic oxide film on a aluminum or aluminum base alloys
US20030112916A1 (en) * 2000-02-25 2003-06-19 Keeney Franklin W. Cold nuclear fusion under non-equilibrium conditions
US20100122908A1 (en) * 2008-11-18 2010-05-20 Spansion Llc Electroplating apparatus and method with uniformity improvement
US9334578B2 (en) * 2008-11-18 2016-05-10 Cypress Semiconductor Corporation Electroplating apparatus and method with uniformity improvement
US9975372B2 (en) 2016-06-21 2018-05-22 Charles White Multi-dimensional art works and methods

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CS166239B2 (enrdf_load_stackoverflow) 1976-02-27
AT325368B (de) 1975-10-27
FI47116B (enrdf_load_stackoverflow) 1973-05-31
SE357582B (enrdf_load_stackoverflow) 1973-07-02
NO121574B (enrdf_load_stackoverflow) 1971-03-15
IE33150L (en) 1970-01-02
IL32384A (en) 1973-05-31
BR6910340D0 (pt) 1973-04-10
DE1931730C3 (de) 1979-12-06
DE1931730A1 (de) 1970-06-18
CH486565A (fr) 1970-02-28
DK137653C (enrdf_load_stackoverflow) 1978-09-18
NL6909930A (enrdf_load_stackoverflow) 1970-01-06
ES369013A1 (es) 1971-05-16
IL32384A0 (en) 1969-08-27
IE33150B1 (en) 1974-04-03
DE1931730B2 (de) 1974-05-02
FI47116C (fi) 1973-09-10
DK137653B (da) 1978-04-10
BE735277A (enrdf_load_stackoverflow) 1969-12-29
FR2014478A1 (enrdf_load_stackoverflow) 1970-04-17
MY7300158A (en) 1973-12-31
LU58989A1 (enrdf_load_stackoverflow) 1969-11-12
GB1271303A (en) 1972-04-19

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