EP0320952A2 - Process for the electrolytic colouring of anodically obtained oxide layers on aluminium or aluminium alloys - Google Patents

Process for the electrolytic colouring of anodically obtained oxide layers on aluminium or aluminium alloys Download PDF

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EP0320952A2
EP0320952A2 EP88121038A EP88121038A EP0320952A2 EP 0320952 A2 EP0320952 A2 EP 0320952A2 EP 88121038 A EP88121038 A EP 88121038A EP 88121038 A EP88121038 A EP 88121038A EP 0320952 A2 EP0320952 A2 EP 0320952A2
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stage
current
alternating current
minutes
direct current
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EP0320952B1 (en
EP0320952A3 (en
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Gartner Co Josef
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Josef Gartner and 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
    • 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

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  • the invention relates to a process for the electrolytic coloring of anodically produced oxide layers on aluminum and aluminum alloys by alternating and direct current treatment in an acid bath containing metal salts.
  • DE-AS 22 09 135 shows such a method in which the direct current treatment under cathodic switching is carried out alternately at a current density of 0.2 to 2 A / dm 2 and the alternating current treatment at a voltage of 1 to 5 volts.
  • DE-PS 24 44 398 shows such a method, in which pulsating direct current is applied in a sulfuric acid bath and the polarity of the pulse voltage applied to the aluminum parts is reversed after certain times which are longer than a pulse period.
  • DE-AS 19 30 288 uses an asymmetrical alternating voltage composed of two half-wave trains obtained by appropriate rectification and separately regulated.
  • DE-AS 26 09 146 shows the application of an anodic direct current treatment of the oxide layer in the dye bath before dyeing, whereupon dyeing is carried out with alternating current.
  • DE-PS 25 38 622 shows dyeing with direct current, the material being anode with direct current in an anodic electrolytic bath, which contains the same water, before dyeing in the electrolyte dye bath soluble metal ion such as the electrolyte dye bath contains, is treated electrolytically.
  • DE-AS 20 34 950 shows dyeing by means of alternating current superimposed on direct current at special temperatures and current densities, the direct current density being between 1/10 and 1/2 of the alternating current density, and circuit arrangements or systems for the electrolytic coloring of anodized aluminum are shown, for example, by DE-AS 26 07 543 and DE-PS 29 41 191.
  • Such dyeings which are carried out with various metal salts that can be separated in the strongly acidic range, in particular tin and copper, are used particularly frequently in facade construction, where very irregularly shaped profiles of sometimes considerable length and large areas are to be colored very uniformly. Especially here there are still considerable problems regarding the uniformity of the color.
  • the first stage in which worked with a partially rectified alternating current expediently takes 0.5 to 5, in particular 1 to 4 minutes, at voltages of 6 to 20, in particular 8 to 18 volts and currents of 0.2 to 2 A / dm 2, in particular 0.4 to 1.2 A. / dm2, followed by a pause of 10 to 60, especially 20 to 50 seconds.
  • the AC treatment takes 0.5 - 15, especially 1 - 12 minutes at a voltage of 15 - 25, especially 16 - 22 volts and initial current densities of 0.2 - 1.2 A / dm2 and final current densities of 0.05 - 0 , 5 A / dm2
  • the ratio between the initial current density and the final current density in the second step is preferably 4: 1 to 8: 1, but can also be higher for blackening.
  • the modified alternating current is rectified to such an extent that the ratio of the anodic component to the cathodic component (i.e. the integral of the wave above the zero line or below the zero line) is approximately 10: 1 to 50: 1, especially 20-40: 1.
  • Such partially rectified alternating currents can be obtained technically via a thyristor with a suitable circuit and are also referred to below as direct current.
  • the treatment times depend on the desired shade, whereby the times for the DC treatment hardly change, but those for the AC treatment do.
  • tin coloring with 2 minutes of direct current treatment and 0.5 minutes of alternating current treatment results in champagne coloring, while 12 minutes with alternating current treatment results in black coloring.
  • the pause between treatments is 40 seconds.
  • Pretreatment with only partially rectified alternating current has no significant oxidation effect. Obviously, it causes an activation of the surface to be colored, but only a very limited oxidation, which is particularly evident when coloring with tin, where hardly any tin dioxide is formed. It is also unclear why there should be a break between the two treatment stages, but the results will be significantly worse without this break.
  • the experimental set-up according to the attached FIG. 6 was used to measure the effect.
  • One of the profile developments shown in FIGS. 7a and 7b was placed in the middle of the circuit.
  • Profile processing 7a had a processing length of 230 mm and an area of 9.1 dm2 with a length of 400 mm
  • profile processing 7b had a processing length of 145 mm and an area of 5.8 dm2 with a length of 400 mm.
  • the counter electrode was made of 4301 stainless steel and dipped into the bathroom at one end.
  • the composition of the dye bath was as follows: 8.5 g / l Sn (approx. 16 g / l SnSo4) 24 g / l H2SO4 conc.
  • the bath also contained the stabilizers customary for such baths (in the present case KBEL2 and KBEL3 from Bihlmaier) in the usual amounts which are also well known (10 ml / l KBEL3 and 20 ml / l KBEL2).
  • the bath temperature was around 20 ° C.
  • the piece was colored under the conditions given in the following examples using the current curves shown in the accompanying figures. After dyeing, a reflection measurement was carried out using three measuring points according to the experimental setup.
  • the reflectometer UAE1 from Dr. Lange, Berlin
  • a scatter value of at most 10 points was considered to be still satisfactory for this test arrangement. A scatter value of less than 5 points can no longer be distinguished with the unarmed eye.
  • the reflection measurement in which the measuring point 2 was set to 100, gave a value of 108 for point 1 and a value of 100 for point 3, so that the scatter is 8 points. This means only a slightly stronger coloration in the area of the test plate initially lying on the counterelectrode and therefore a practically uniform coloration up to the most distant part at measurement point 3.
  • the example was repeated with profile 1b, working for 16 minutes at 16 V and 2 A in the first stage and after a break of 40 seconds in the second stage for 4 minutes at 19 V and an initial current of 2 A and a final current of 0 , 5 A was worked.
  • the reflection measurement gave a value of 107 for point 1 and a value of 101 for point 3, i.e. a scatter of 7 points.
  • the reflection measurement in which the measuring point 2 was set to 100, gave a value of 103 for point 1 and a value of 101 for point 2, so that the scatter is 3 points.
  • the example was repeated with profile 1b, working in stage 1 for 2 minutes at 12.5 V and 12.5 A and after a break of 40 seconds for 4 minutes at 19 V with an initial current of 2 A and a final current of 0. 5 A was worked.
  • the reflection measurement gave a value of 103 for point 1 and a value for 101 for point 3, i.e. a scatter of 3 points.
  • the reflection measurement in which the measuring point 2 was set to 100, gave a value of 103 for point 1 and a value of 102 for point 3, so that the scatter is 3 points.
  • the example was repeated with profile 1b, working in the first stage for 2 minutes at 9 V and 2A and after a 40 second pause in the second stage for 4 minutes at 19 V with an initial current of 2A and a final current of 0.5 A was worked on.
  • the result was 103 points for measuring point 1 and 102 for measuring point 3, ie a scatter of 3 points.
  • the reflection measurement in which the measuring point 2 was set to 100, gave a value of 130 for point 1 and a value of 101 for point 3, so that the scatter is 30 points.
  • the reflection measurement in which measuring point 2 was set to 100, gave a value of 92 for point 1 and for point 3 a value of 115, so that the scatter is 15 points to the O value, but a total of 23 points, which gives a clear difference in color between the beginning and end of the sheet.

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Abstract

The invention discloses a process for electrolytically colouring anodic oxide layers on aluminium or its alloys by means of alternating current in electrolytes containing metal salt. The process comprises two stages, direct current being applied in the first stage and alternating current in the second stage and a notable feature is that, instead of direct current, a modified alternating current which contains a marked cathodic component is applied in the first stage and an off-time of 10 to 60 seconds is inserted between direct current and alternating current treatment, a longer time and/or higher voltage being employed in the second stage than in the first stage.

Description

Die Erfindung betrifft ein Verfahren zum elektrolytischen Färben von anodisch erzeugten Oxidschichten auf Aluminium und Aluminiumlegierungen durch Wechsel- und Gleichstrombe­handlung in einem Metallsalze enthaltenden sauren Bad.The invention relates to a process for the electrolytic coloring of anodically produced oxide layers on aluminum and aluminum alloys by alternating and direct current treatment in an acid bath containing metal salts.

Es gibt zahlreiche Verfahren, Aluminium oder Aluminiumle­gierungen, auf die ein anodisch erzeugter Oxidfilm aufgebracht ist, in einem Metallsalze enthaltenden Elektrolyten zu färben, und zwar mit Wechselstrom oder Gleichstrom oder einer Kombination davon. Ein besonderes Problem bei der elektrolytischen Färbung ist die Gleichmäßigkeit der Färbung über das ganze Werkstück hinweg, und zahlreiche Verfahren und Vorrichtungen sollen diese Gleichmäßigkeit der Färbung verbessern, insbesondere durch Kombination von pulsierenden Gleich- bzw. Wechselströmen.There are numerous methods of coloring aluminum or aluminum alloys to which an anodized oxide film is applied in an electrolyte containing metal salts, using alternating current or direct current or a combination thereof. A particular problem with electrolytic coloring is the uniformity of the coloring across the entire workpiece, and numerous methods and devices are intended to improve this uniformity of the coloring, in particular by combining pulsating direct or alternating currents.

So zeigt die DE-AS 22 09 135 ein solches Verfahren, bei dem die Gleichstrombehandlung unter kathodischer Schaltung bei einer Stromdichte von 0,2 bis 2 A/dm² und die Wechselstrombehandlung bei einer Spannung von 1 bis 5 Volt abwechselnd vorgenommen werden. Die DE-PS 24 44 398 zeigt ein solches Verfahren, wobei pulsierender Gleichstrom in einem schwefelsauren Bad angelegt wird und die Polarität der an die Aluminiumteile angelegten Impulsspannung nach bestimmten Zeiten, die länger sind als eine Impulsperiode, jeweils umgekehrt wird. Die DE-AS 19 30 288 verwendet eine unsymmetrische, aus zwei durch entsprechende Gleichrichtung gewonnenen und getrennt geregelten Halbwellenzügen zusammengesetzte Wechselspannung. Die DE-AS 26 09 146 zeigt die Anwendung einer anodischen Gleichstrombehandlung der Oxidschicht im Färbebad vor dem Färben, worauf dann mit Wechselstrom gefärbt wird. Die DE-PS 25 38 622 schließlich zeigt das Färben mit Gleichstrom, wobei vor dem Färben im Elektrolyt-Färbebad der Werkstoff als Anode mit Gleichstrom in einem anodischen Elektolysebad, das das gleiche wasser­ lösliche Metallion wie das Elektrolyt-Färbebad enthält, elektrolytisch behandelt wird. Die DE-AS 20 34 950 zeigt das Färben mittels gleichstromüberlagertem Wechselstrom bei speziellen Temperaturen und Stromdichten, wobei die Gleichstromdichte zwischen 1/10 und 1/2 der Wechselstrom­dichte liegt, und Schaltungsanordnungen oder Systeme zum elektrolytischen Einfärben von eloxiertem Aluminium zeigen z.B. die DE-AS 26 07 543 und die DE-PS 29 41 191.For example, DE-AS 22 09 135 shows such a method in which the direct current treatment under cathodic switching is carried out alternately at a current density of 0.2 to 2 A / dm 2 and the alternating current treatment at a voltage of 1 to 5 volts. DE-PS 24 44 398 shows such a method, in which pulsating direct current is applied in a sulfuric acid bath and the polarity of the pulse voltage applied to the aluminum parts is reversed after certain times which are longer than a pulse period. DE-AS 19 30 288 uses an asymmetrical alternating voltage composed of two half-wave trains obtained by appropriate rectification and separately regulated. DE-AS 26 09 146 shows the application of an anodic direct current treatment of the oxide layer in the dye bath before dyeing, whereupon dyeing is carried out with alternating current. Finally, DE-PS 25 38 622 shows dyeing with direct current, the material being anode with direct current in an anodic electrolytic bath, which contains the same water, before dyeing in the electrolyte dye bath soluble metal ion such as the electrolyte dye bath contains, is treated electrolytically. DE-AS 20 34 950 shows dyeing by means of alternating current superimposed on direct current at special temperatures and current densities, the direct current density being between 1/10 and 1/2 of the alternating current density, and circuit arrangements or systems for the electrolytic coloring of anodized aluminum are shown, for example, by DE-AS 26 07 543 and DE-PS 29 41 191.

Allerdings ist das Problem der gleichmäßigen Färbung, insbesondere bei größeren Werkstücken, immer noch nicht ganz befriedigend gelöst, so daß weiterhin ein Bedarf an einer Methode besteht, welche die Färbung über das gesamte Werkstück hinweg, insbesondere bei unregelmäßig geformten Werkstücken, gleichmäßiger macht, also eine bessere Streuung bewirkt.However, the problem of uniform coloring, especially in the case of larger workpieces, is still not entirely satisfactorily resolved, so that there is still a need for a method which makes the coloring more uniform over the entire workpiece, in particular with irregularly shaped workpieces, i.e. one causes better dispersion.

Derartige Färbungen, die mit verschiedenen Metallsalzen durchgeführt werden, die im stark sauren Bereich abscheidbar sind, insbesondere Zinn und Kupfer, werden besonders häufig im Fassadenbau eingesetzt, wo sehr unregelmäßig geformte Profile von zum Teil erheblicher Länge und große Flächen sehr einheitlich gefärbt werden sollen. Vor allem hier gibt es derzeit noch erhebliche Probleme bezüglich der Gleichmäßigkeit der Färbung.Such dyeings, which are carried out with various metal salts that can be separated in the strongly acidic range, in particular tin and copper, are used particularly frequently in facade construction, where very irregularly shaped profiles of sometimes considerable length and large areas are to be colored very uniformly. Especially here there are still considerable problems regarding the uniformity of the color.

Es wurde nun gefunden, daß eine gleichmäßigere Färbung dann erzielt werden kann, wenn eine ganz spezielle Kombination eines modifizierten Wechselstroms, nämlich eines teilweise gleichgerichteten Wechselstroms, als Vorschaltung mit anschließender Behandlung in Wechselstrom, in ein und demselben Bad angewandt wird. Zwischen diesen beiden Stufen ist eine Pause einzuschieben. Die erste Stufe, bei der mit einem teilweise gleichgerichteten Wechselstrom gearbeitet wird, dauert zweckmäßig 0,5 bis 5, insbesondere 1 bis 4 Minuten, bei Spannungen von 6 bis 20, insbes. 8 - 18 Volt und Stromstärken von 0,2 bis 2 A/dm², insbesondere 0,4 bis 1,2 A/dm², worauf eine Pause von 10 bis 60, insbesondere 20 bis 50 Sekunden folgt. Die Wechselstrombehandlung benötigt 0,5 - 15, insbesondere 1 - 12 Minuten, bei einer Spannung von 15 - 25, insb. 16 - 22 Volt und Anfangsstromdichten von 0,2 - 1,2 A/dm² und Endstromdichten von 0,05 - 0,5 A/dm² Vorzugsweise beträgt das Verhältnis zwischen Anfangsstromdichte und Endstromdichte beim zweiten Schritt 4 : 1 bis 8 : 1, kann jedoch bei Schwarzfärbungen auch noch höher liegen..It has now been found that a more uniform coloring can be achieved if a very special combination of a modified alternating current, namely a partially rectified alternating current, is used as a preliminary circuit with subsequent treatment in alternating current, in one and the same bath. A break should be inserted between these two levels. The first stage, in which worked with a partially rectified alternating current expediently takes 0.5 to 5, in particular 1 to 4 minutes, at voltages of 6 to 20, in particular 8 to 18 volts and currents of 0.2 to 2 A / dm 2, in particular 0.4 to 1.2 A. / dm², followed by a pause of 10 to 60, especially 20 to 50 seconds. The AC treatment takes 0.5 - 15, especially 1 - 12 minutes at a voltage of 15 - 25, especially 16 - 22 volts and initial current densities of 0.2 - 1.2 A / dm² and final current densities of 0.05 - 0 , 5 A / dm² The ratio between the initial current density and the final current density in the second step is preferably 4: 1 to 8: 1, but can also be higher for blackening.

Der modifizierte Wechselstrom ist soweit gleichgerichtet, daß das Verhältnis des anodischen Anteils zum kathodischen Anteil (also das Integral der Welle über der Nullinie bzw. unter der Nullinie) etwa 10 : 1 bis 50 : 1, insb. 20 - 40 : 1 beträgt. Solche teilweise gleichgerichteten Wechselströme lassen sich technisch über einen Thyristor bei geeigneter Schaltung erhalten und werden im folgenden auch Gleichstrom genannt.The modified alternating current is rectified to such an extent that the ratio of the anodic component to the cathodic component (i.e. the integral of the wave above the zero line or below the zero line) is approximately 10: 1 to 50: 1, especially 20-40: 1. Such partially rectified alternating currents can be obtained technically via a thyristor with a suitable circuit and are also referred to below as direct current.

Die Behandlungszeiten hängen vom gewünschten Farbton ab, wobei sich die Zeiten für die Gleichstrombehandlung kaum verändern, wohl aber die für die Wechselstrombehandlung. Im typischen Fall ergibt sich bei einer Zinnfärbung bei 2 Minuten Gleichstrombehandlung und 0,5 Minuten Wechselstrombehandlung eine Champagnerfärbung, während bei 12 Minuten Wechselstrombehandlung eine Schwarzfärbung erfolgt. Die Pause zwischen den Behandlungen beträgt dabei 40 Sekunden.The treatment times depend on the desired shade, whereby the times for the DC treatment hardly change, but those for the AC treatment do. Typically, tin coloring with 2 minutes of direct current treatment and 0.5 minutes of alternating current treatment results in champagne coloring, while 12 minutes with alternating current treatment results in black coloring. The pause between treatments is 40 seconds.

Es ist überraschend, daß das Vorschalten eines derart modifizierten Wechselstroms und die Einschaltung einer Pause nach dieser Behandlung eine wesentlich gleichmäßigere Streuung zur Folge hat als dies nach dem Stand der Technik möglich war. Wie Vergleichsversuche zeigen, ergibt das seit langem bekannte Färben mit nur Wechselstrom einerseits und das Färben mit einer vorgeschalteten Gleichstromstufe gemäß DE-AS 26 09 146 andererseits deutlich weniger Streuung, also ungleichmäßigere Färbung als das erfindungsgemäße Verfahren.It is surprising that the switching on of such an alternating current and the switching on of a pause after this treatment are much more uniform Scattering has resulted than was possible according to the prior art. As comparative experiments show, the long-known dyeing with only alternating current on the one hand and dyeing with an upstream direct current stage according to DE-AS 26 09 146 on the other hand results in significantly less scattering, that is to say more uneven coloring than the process according to the invention.

Dies ist umso überraschender als der Fachmann gerade durch die letztgenannte DE-AS 26 09 146, deren Vorschaltung einer Gleichstromstufe eine deutliche Verbesserung des Färbens mit ausschließlich Wechselstrom ergibt, davon abgehalten wurde, eine Vorstufe anzuwenden, die weniger stark anodisch ist oder gar ins Kathodische geht.This is all the more surprising as the person skilled in the art, precisely because of the last-mentioned DE-AS 26 09 146, whose connection of a direct current stage results in a significant improvement in dyeing with only alternating current, was prevented from using a preliminary stage which is less strongly anodic or even cathodic .

Die Vorbehandlung mit nur teilweise gleichgerichtetem Wechselstrom hat keine wesentliche Oxidationswirkung. Sie bewirkt offenbar zwar eine Aktivierung der zu färbenden Fläche aber nur eine sehr begrenzte Oxidation, was sich insbesondere beim Färben mit Zinn zeigt, wo kaum Zinndioxid gebildet wird. Es ist auch ungeklärt, warum eine Pause zwischen die beiden Behandlungsstufen gelegt werden muß, jedoch werden die Ergebnisse ohne diese Pause deutlich schlechter.Pretreatment with only partially rectified alternating current has no significant oxidation effect. Obviously, it causes an activation of the surface to be colored, but only a very limited oxidation, which is particularly evident when coloring with tin, where hardly any tin dioxide is formed. It is also unclear why there should be a break between the two treatment stages, but the results will be significantly worse without this break.

Die folgenden Beispiele erläutern die Erfindung.The following examples illustrate the invention.

Zur Messung des Effektes wurde der Versuchsaufbau gemäß beiliegender Figur 6 benutzt. Eine der in Fig. 7a und 7b dargestellten Profilabwicklungen wurde in der Mitte an den Stromkreis gelegt. Profilabwicklung 7a hatte 230 mm Abwicklungslänge und bei einer Länge von 400 mm eine Fläche von 9,1 dm² während Profilabwicklung 7b 145 mm Profilabwicklungslänge und bei einer Länge von 400 mm eine Fläche von 5,8 dm² hatte. Die Gegenelektrode bestand aus Edelstahl 4301 und tauchte an einem Ende ins Bad. Die Zusammensetzung des Färbebades war wie folgt:
8,5 g/l Sn (ca. 16 g/l SnSo₄)
24 g/l H₂SO₄ konz.The experimental set-up according to the attached FIG. 6 was used to measure the effect. One of the profile developments shown in FIGS. 7a and 7b was placed in the middle of the circuit. Profile processing 7a had a processing length of 230 mm and an area of 9.1 dm² with a length of 400 mm, while profile processing 7b had a processing length of 145 mm and an area of 5.8 dm² with a length of 400 mm. The counter electrode was made of 4301 stainless steel and dipped into the bathroom at one end. The composition of the dye bath was as follows:
8.5 g / l Sn (approx. 16 g / l SnSo₄)
24 g / l H₂SO₄ conc.

Weiter enthielt das Bad die für solche Bäder üblichen Stabilisatoren (im vorliegenden Fall KBEL2 und KBEL3 der Firma Bihlmaier) in den ebenfalls wohl bekannten üblichen Mengen (10 ml/l KBEL3 und 20 ml/l KBEL2).The bath also contained the stabilizers customary for such baths (in the present case KBEL2 and KBEL3 from Bihlmaier) in the usual amounts which are also well known (10 ml / l KBEL3 and 20 ml / l KBEL2).

Die Badtemperatur betrug Umgebungstemperatur, also ca. 20°C.The bath temperature was around 20 ° C.

Das Stück wurde unter den in den folgenden Beispielen angegebenen Bedingungen unter Anwendung der in den beigefügten Figuren gezeigten Stromkurven gefärbt. Nach dem Färben wurde eine Reflexionsmessung vorgenommen, wobei drei Meßpunkte gemäß Versuchsaufbau benutzt wurden. Das Reflektometer (UME1 der Firma Dr. Lange, Berlin) wurde beim Meßpunkt 2, der sich der Stromzuführung am nächsten befand, auf 100 eingestellt und dann wurden die beiden Enden, also die Meßpunkte 1 und 3 gemessen. Der Unterschied zwischen den Endmeßpunkten und dem O-Punkt (Meßpunkt 2) oder, falls dieser Wert größer war, zwischen den Meßpunkten 1 und 3, wurde in Punkten ausgedrückt. Je geringer der Unterschied ist, desto gleichmäßiger ist die Färbung und somit desto besser die Streuung. Ein Streuwert von höchstens 10 Punkten wurde für diese Versuchsanordnung als noch zufriedenstellend betrachtet. Ein Streuwert von unter 5 Punkten ist mit dem unbewaffneten Auge nicht mehr zu unterscheiden.The piece was colored under the conditions given in the following examples using the current curves shown in the accompanying figures. After dyeing, a reflection measurement was carried out using three measuring points according to the experimental setup. The reflectometer (UME1 from Dr. Lange, Berlin) was set to 100 at measuring point 2, which was closest to the power supply, and then the two ends, measuring points 1 and 3, were measured. The difference between the final measuring points and the O point (measuring point 2) or, if this value was larger, between measuring points 1 and 3 was expressed in points. The smaller the difference, the more uniform the coloring and thus the better the scatter. A scatter value of at most 10 points was considered to be still satisfactory for this test arrangement. A scatter value of less than 5 points can no longer be distinguished with the unarmed eye.

Beispiel 1aExample 1a Profil aProfile a

  • 1. Stufe: Zeit 2 Minuten, Spannung 16 V, Strom 5 A Pause: 40 Sekunden1st stage: time 2 minutes, voltage 16 V, current 5 A break: 40 seconds
  • 2. Stufe: Zeit 4 Minuten, Spannung 19 V, Anfangsstrom 4 A2nd stage: time 4 minutes, voltage 19 V, initial current 4 A

Die Reflexionsmessung, bei der der Meßpunkt 2 auf 100 eingestellt wurde, ergab für Punkt 1 einen Wert von 108 und für Punkt 3 einen Wert von 100, so daß die Streuung 8 Punkte beträgt. Dies bedeutet eine nur geringfügig stärkere Färbung bei dem der Gegenelektrode zunächst liegenden Bereich des Prüfbleches und daher eine praktisch gleichmäßige Färbung bis zum entferntest liegenden Teil beim Meßpunkt 3.The reflection measurement, in which the measuring point 2 was set to 100, gave a value of 108 for point 1 and a value of 100 for point 3, so that the scatter is 8 points. This means only a slightly stronger coloration in the area of the test plate initially lying on the counterelectrode and therefore a practically uniform coloration up to the most distant part at measurement point 3.

Beispiel 1bExample 1b

Das Beispiel wurde mit Profil 1b wiederholt, wobei in der ersten Stufe 2 Minuten lang bei 16 V und 2 A gearbeitet und nach einer Pause von 40 Sekunden in der zweiten Stufe 4 Minuten bei 19 V und einer Anfangsstromstärke von 2 A und einer Endstromstärke von 0,5 A gearbeitet wurde. Die Reflexionsmessung ergab für Punkt 1 einen Wert von 107 und für Punkt 3 einen Wert von 101, also eine Streuung von 7 Punkten.The example was repeated with profile 1b, working for 16 minutes at 16 V and 2 A in the first stage and after a break of 40 seconds in the second stage for 4 minutes at 19 V and an initial current of 2 A and a final current of 0 , 5 A was worked. The reflection measurement gave a value of 107 for point 1 and a value of 101 for point 3, i.e. a scatter of 7 points.

Beispiel 2aExample 2a

  • 1. Stufe: Zeit 2 Minuten, Spannung 12,5 V, Strom 4 A, Pause 40 Sekunden1st stage: time 2 minutes, voltage 12.5 V, current 4 A, pause 40 seconds
  • 2. Stufe: Zeit 4 Minuten, Spannung 19 V, Anfangsstrom 4 A2nd stage: time 4 minutes, voltage 19 V, initial current 4 A

Die Reflexionsmessung, bei der der Meßpunkt 2 auf 100 eingestellt wurde, ergab für Punkt 1 einen Wert von 103 und für Punkt 2 einen Wert von 101, so daß die Streuung 3 Punkte beträgt. Dies bedeutet eine nur sehr geringfügige stärkere Färbung bei dem der Gegenelektrode zunächst liegenden Bereich des Prüfbleches, also Meßpunkt 1 und daher eine praktisch gleichmäßige Färbung über die ganze Fläche des Bleches, deren Unterschiede für das Auge nicht mehr sichtbar sind.The reflection measurement, in which the measuring point 2 was set to 100, gave a value of 103 for point 1 and a value of 101 for point 2, so that the scatter is 3 points. This means only a very slight, more intense coloring in the area of the test sheet lying next to the counterelectrode, ie measuring point 1, and therefore a practically uniform coloring over the entire area of the sheet, the differences of which are no longer visible to the eye.

Beispiel 2bExample 2b

Das Beispiel wurde mit Profil 1b wiederholt, wobei in Stufe 1 2 Minuten bei 12,5 V und 12,5 A gearbeitet und nach einer Pause von 40 Sekunden 4 Minuten lang bei 19 V bei einem Anfangsstrom von 2 A und einem Endstrom von 0,5 A gearbeitet wurde. Die Reflexionsmessung ergab für Punkt 1 einen Wert von 103 und für Punkt 3 einen Wert für 101, also eine Streuung von 3 Punkten.The example was repeated with profile 1b, working in stage 1 for 2 minutes at 12.5 V and 12.5 A and after a break of 40 seconds for 4 minutes at 19 V with an initial current of 2 A and a final current of 0. 5 A was worked. The reflection measurement gave a value of 103 for point 1 and a value for 101 for point 3, i.e. a scatter of 3 points.

Beispiel 3aExample 3a Profil aProfile a

  • 1. Stufe: Zeit 2 Minuten, Spannung 9 V, Strom 4 A, Pause 40 Sekunden1st stage: time 2 minutes, voltage 9 V, current 4 A, pause 40 seconds
  • 2. Stufe: Zeit 4 Minuten, Spannung 19 V, Anfangsstrom 5 A2nd stage: time 4 minutes, voltage 19 V, initial current 5 A.

Die Reflexionsmessung, bei der der Meßpunkt 2 auf 100 eingestellt wurde, ergab für Punkt 1 einen Wert von 103 und für Punkt 3 einen Wert von 102, so daß die Streuung 3 Punkte beträgt. Dies bedeutet eine nur sehr geringfügige stärkere Färbung bei dem der Gegenelektrode zunächst liegenden Bereich des Prüfbleches, also Meßpunkt 1 und daher eine praktisch gleichmäßige Färbung über die ganze Fläche des Bleches Die Färbungsunterschiede sind für das Auge nicht mehr sichtbar.The reflection measurement, in which the measuring point 2 was set to 100, gave a value of 103 for point 1 and a value of 102 for point 3, so that the scatter is 3 points. This means only a very slight stronger coloring in the area of the test sheet lying next to the counterelectrode, ie measuring point 1 and therefore a practically uniform coloring over the entire area of the sheet. The color differences are no longer visible to the eye.

Beispiel 3bExample 3b

Das Beispiel wurde mit Profil 1b wiederholt, wobei in der ersten Stufe 2 Minuten bei 9 V und 2 A gearbeitet und nach 40 Sekunden Pause in der zweiten Stufe 4 Minunten lang bei 19 V bei einem Anfangsstrom von 2 A und einem Endstrom von 0,5 A gearbeitet wurde. Es ergaben sich 103 Punkte für Meßpunkt 1 und 102 für Meßpunkt 3, also eine Streuung von 3 Punkten.The example was repeated with profile 1b, working in the first stage for 2 minutes at 9 V and 2A and after a 40 second pause in the second stage for 4 minutes at 19 V with an initial current of 2A and a final current of 0.5 A was worked on. The result was 103 points for measuring point 1 and 102 for measuring point 3, ie a scatter of 3 points.

Vergleichsbeispiel 1Comparative Example 1 Profil aProfile a

Hier wurde zuerst mit Gleichstrom und dann nach Pause mit Wechselstrom gearbeitet.

  • 1. Stufe: Zeit 2 Minunten, Spannung 16 V, Strom 5 A, Pause 40 Sekunden
  • 2. Stufe: Zeit 4 Minunten, Spannung 19 V, Strom 4 A
Here they worked first with direct current and then after a break with alternating current.
  • 1st stage: time 2 minutes, voltage 16 V, current 5 A, pause 40 seconds
  • 2nd stage: time 4 minutes, voltage 19 V, current 4 A

Die Reflexionsmessung, bei der der Meßpunkt 2 auf 100 eingestellt wurde, ergab für Punkt 1 einen Wert von 130 und für Punkt 3 einen Wert von 101, so daß die Streuung 30 Punkte beträgt. Dies bedeutet eine deutlich stärkere Färbung bei dem der Gegenelektrode zunächst liegenden Bereich des Prüfbleches und daher eine nicht mehr zufriedenstellende Färbung über die Länge des Prüfbleches im Vergleich zum bezüglich der Stromdaten vergleichbaren erfindungsgemäßen Beispiels 1a beim gleichen ProfilThe reflection measurement, in which the measuring point 2 was set to 100, gave a value of 130 for point 1 and a value of 101 for point 3, so that the scatter is 30 points. This means a significantly stronger coloration in the area of the test plate initially lying on the counterelectrode and therefore a no longer satisfactory coloration over the length of the test plate in comparison with Example 1a according to the invention, which is comparable in terms of current data, with the same profile

Vergleichsbeispiel 2Comparative Example 2 Profil bProfile b

Hier wurde mit Profil b gearbeitet und ein reiner Gleichstrom angewandt.

  • 1. Stufe: Zeit 2 Minuten, Spannung 16 V, Strom 1 A, Pause 40 Sekunden
  • 2. Stufe: Zeit 4 Minunten, Spannung 19 V, Anfangsstrom 2 A, Endstrom 0,5 A.
Profile b was used here and a pure direct current was used.
  • 1st stage: time 2 minutes, voltage 16 V, current 1 A, pause 40 seconds
  • 2nd stage: time 4 minutes, voltage 19 V, start current 2 A, end current 0.5 A.

Die Reflexionsmessung, bei der der Meßpunkt 2 auf 100 eingestellt wurde, ergab für Punkt 1 einen Wert von 92 und für Punkt 3 einen Wert von 115, so daß die Streuung 15 Punkte zum O-Wert, aber insgesamt 23 Punkte beträgt, was zwischen Anfang und Ende des Bleches einen deutlichen Unterschied in der Färbung ergibt.The reflection measurement, in which measuring point 2 was set to 100, gave a value of 92 for point 1 and for point 3 a value of 115, so that the scatter is 15 points to the O value, but a total of 23 points, which gives a clear difference in color between the beginning and end of the sheet.

Claims (4)

1. Verfahren zum elektrolytischen Färben von anodischen Oxidschichten auf Aluminium oder dessen Legierungen mittels Wechselstrom in Metallsalz enthaltenden saueren Elektrolyten in zwei Stufen, wobei in der ersten Stufe Gleichstrom und in der zweiten Stufe Wechselstrom angelegt wird, dadurch gekennzeichnet, daß in der ersten Stufe statt Gleichstrom ein modifizierter Wechselstrom angelegt wird, der einen deutlichen kathodischen Anteil enthält und zwischen Gleichstrom und Wechselstrombehand­lung eine Pause von 10 bis 60 Sekunden eingelegt wird, wobei in der zweiten Stufe eine längere Zeit und/oder bei höherer Spannung als in der ersten Stufe gearbeitet wird.1. Process for the electrolytic coloring of anodic oxide layers on aluminum or its alloys by means of alternating current in acidic electrolytes containing metal salt in two stages, direct current being applied in the first stage and alternating current being applied in the second stage, characterized in that instead of direct current in the first stage a modified alternating current is applied, which contains a clear cathodic component and a pause of 10 to 60 seconds is inserted between direct current and alternating current treatment, the longer stage and / or a higher voltage being used than in the first stage. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß in der ersten Stufe 0,5 bis 5 Minuten mit Spannungen von 5 bis 20 V und Stromdichten von 0,2 bis 2 A/dm² und in der zweiten Stufe 0,5 bis 15 Minuten bei einer Spannung von 15 bis 25 V, einer Anfangsstromdichte von 0,2 bis 1,2 A/dm² und einer Endstromdichte von 0,05 bis 0,5 A/dm² und bei einer Pause von 20 bis 50 Sekunden gearbeitet wird.2. The method according to claim 1, characterized in that in the first stage 0.5 to 5 minutes with voltages of 5 to 20 V and current densities of 0.2 to 2 A / dm² and in the second stage 0.5 to 15 minutes at a voltage of 15 to 25 V, an initial current density of 0.2 to 1.2 A / dm² and a final current density of 0.05 to 0.5 A / dm² and a break of 20 to 50 seconds. 3. Verfahren nach Anspruch 1 oder 2 dadurch gekennzeichnet, daß in der ersten Stufe ein modifizierter Wechselstrom angelegt wird, der soweit gleichgerichtet ist, daß das Verhältnis des anodischen Anteils zum kathodischen Anteil 10 : 1 bis 50 : 1 beträgt.3. The method according to claim 1 or 2, characterized in that a modified alternating current is applied in the first stage, which is rectified to the extent that the ratio of the anodic portion to the cathodic portion is 10: 1 to 50: 1. 4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß in der zweiten Stufe das Verhältnis der Anfangsstromdichte zur Endstromdichte 4 : 1 bis 8 : 1 beträgt.4. The method according to any one of the preceding claims, characterized in that in the second stage the ratio of the initial current density to the final current density is 4: 1 to 8: 1.
EP88121038A 1987-12-18 1988-12-15 Process for the electrolytic colouring of anodically obtained oxide layers on aluminium or aluminium alloys Expired - Lifetime EP0320952B1 (en)

Priority Applications (1)

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AT88121038T ATE89338T1 (en) 1987-12-18 1988-12-15 PROCESS FOR ELECTROLYTIC COLORING OF ANODICALLY PRODUCED OXIDE COATINGS ON ALUMINUM AND ALUMINUM ALLOYS.

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DE3743113 1987-12-18
DE19873743113 DE3743113A1 (en) 1987-12-18 1987-12-18 METHOD FOR ELECTROLYTICALLY CARBONIZING ANODICALLY PRODUCED OXIDIVE LAYERS ON ALUMINUM AND ALUMINUM ALLOYS

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0487754A1 (en) * 1990-11-25 1992-06-03 BEFELD SYSTEME GmbH Process for the electrolytic colouring of anodically obtained oxide layers on aluminium or aluminium alloys
EP0605354A1 (en) * 1992-12-31 1994-07-06 Novamax Technologies Holdings Inc. A process for obtaining a range of colours of the visible spectrum using electrolysis on anodized aluminium

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2053972A (en) * 1979-07-04 1981-02-11 Empresa Nacional Aluminio Electrolytic colouring of anodized aluminium
EP0239944A1 (en) * 1986-04-01 1987-10-07 Fujisash Company Method for electrolytic coloring of aluminum or aluminum alloys
EP0279146A1 (en) * 1987-01-16 1988-08-24 Alusuisse-Lonza Services Ag Process for electrolytically colouring an anodic oxide layer on aluminium or aluminium alloys

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1902983C3 (en) * 1968-06-21 1978-06-22 Keller, Eberhard, 7121 Freudental Process for the electrolytic coloring of anodic oxide layers on aluminum or aluminum alloys
FR2052100A5 (en) * 1969-07-16 1971-04-09 Cegedur Gp
JPS5014623B1 (en) * 1971-02-22 1975-05-29
JPS547267B2 (en) * 1973-09-21 1979-04-05
JPS5423664B2 (en) * 1975-03-06 1979-08-15
ES437604A1 (en) * 1975-05-12 1977-01-16 Empresa Nacional Aluminio System for autocontrolling and regulating the average value of the voltage applied to processes for the electrolytic coloring of anodized aluminum
ES474736A1 (en) * 1978-10-31 1979-04-01 Empresa Nacional Aluminio System for generating and autocontrolling the voltage or current wave form applicable to processes for the electrolytic coloring of anodized aluminium
ES498578A0 (en) * 1981-01-16 1981-12-01 Ronain Sa ELECTROLYTIC COLORING PROCEDURE OF AN ALUMINUM PART OR ALUMINUM ALLOY

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2053972A (en) * 1979-07-04 1981-02-11 Empresa Nacional Aluminio Electrolytic colouring of anodized aluminium
EP0239944A1 (en) * 1986-04-01 1987-10-07 Fujisash Company Method for electrolytic coloring of aluminum or aluminum alloys
EP0279146A1 (en) * 1987-01-16 1988-08-24 Alusuisse-Lonza Services Ag Process for electrolytically colouring an anodic oxide layer on aluminium or aluminium alloys

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0487754A1 (en) * 1990-11-25 1992-06-03 BEFELD SYSTEME GmbH Process for the electrolytic colouring of anodically obtained oxide layers on aluminium or aluminium alloys
EP0605354A1 (en) * 1992-12-31 1994-07-06 Novamax Technologies Holdings Inc. A process for obtaining a range of colours of the visible spectrum using electrolysis on anodized aluminium

Also Published As

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DE3743113A1 (en) 1989-06-29
EP0320952B1 (en) 1993-05-12
EP0320952A3 (en) 1990-01-31
ATE89338T1 (en) 1993-05-15
DE3743113C2 (en) 1992-05-07
DE3880990D1 (en) 1993-06-17

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