EP0289459A1 - Process for the electrolytic grey coloring of anodic oxide layers on aluminium or aluminium alloys - Google Patents

Process for the electrolytic grey coloring of anodic oxide layers on aluminium or aluminium alloys Download PDF

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Publication number
EP0289459A1
EP0289459A1 EP88810254A EP88810254A EP0289459A1 EP 0289459 A1 EP0289459 A1 EP 0289459A1 EP 88810254 A EP88810254 A EP 88810254A EP 88810254 A EP88810254 A EP 88810254A EP 0289459 A1 EP0289459 A1 EP 0289459A1
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EP
European Patent Office
Prior art keywords
gray
electrolytic
aluminium
coloring
anodic oxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP88810254A
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German (de)
French (fr)
Inventor
Fritz Schneeberger
Heinz Steup
Jean-François Paulet
Bruno Boetsch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcan Holdings Switzerland AG
Original Assignee
Alusuisse Holdings AG
Schweizerische Aluminium AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alusuisse Holdings AG, Schweizerische Aluminium AG filed Critical Alusuisse Holdings AG
Publication of EP0289459A1 publication Critical patent/EP0289459A1/en
Withdrawn legal-status Critical Current

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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

Definitions

  • the invention relates to a method for the electrolytic gray coloring of anodic oxide layers on aluminum or aluminum alloys.
  • gray tones can be produced by a combination dyeing, in which an electrolytic metal salt dyeing and subsequently an immersion treatment in an aqueous solution of a heteropolyacid made of silicon or phosphorus with molybdenum or tungsten is used.
  • an electrolytic metal salt dyeing and subsequently an immersion treatment in an aqueous solution of a heteropolyacid made of silicon or phosphorus with molybdenum or tungsten is used.
  • the electrolytic dye bath mentioned in DE-AS 25 20 955 also leads, among other things, to gray coloring.
  • the bath contains metal salts and barrier layer formers such as phosphonic acids and / or aminocarboxylic acids.
  • the barrier layer should improve the quality of the oxide layer with coloring.
  • Example 26 specifies a dyeing process with gray tone formation, in which an electrolyte with ammonium molybdate, tin sulfate, sulfuric acid, phosphonic acid, glycerol and cresol sulfuric acid is used.
  • the electrolyte bath guidance is again very difficult, since the electrolyte is already built up in a complicated manner and the electrochemical reactions are therefore difficult to control. For example, precipitation cannot be prevented.
  • the inventors have set themselves the task of creating a method of the type mentioned at the outset, which can be achieved using a simple, i.e. Electrolytes consisting of a few compounds are built up and produce reproducible shades of gray that practically show no fluctuations over the entire workpiece surface.
  • Another aim of the inventors, which is independent of the above task, is to choose the composition of the electrolyte in such a way that it meets today's general environmental protection regulations.
  • the object is achieved by a method which is distinguished by the wording of claim 1.
  • At least one aliphatic and / or aromatic carbon and / or dicarboxylic acid and / or aminocarboxylic acid and / or alkanolamine can be used.
  • the method according to the invention has the advantage that, due to the uniform coloring, large-area or large-sized aluminum or aluminum alloy objects are provided with a gray color shade that meets the highest aesthetic requirements. For example, facade panels in the architectural sector can then be produced without a color effect that varies in gray. Or after the process, long - several meters long - profile strips can be provided with a gray tone that remains the same over the entire length. This is advantageous, for example, if several colored profile strips from different color batches are attached to an object. A tedious search for profile strips from different batches of dye with approximately the same shade of gray, as is at least partially necessary according to the previously known dyeing methods, is therefore unnecessary in the method according to the invention.
  • the method according to the invention acts in the same and uniform manner, ie without a difference being discernible, in the case of rolled and pressed aluminum or aluminum alloy material.
  • Anodic oxide layers that are only a few ⁇ m thick can be provided with a uniform shade of gray using the method according to the invention. It has been shown in particular that colored layers of approximately 10 to 25 ⁇ m are particularly suitable for the most common application purposes.
  • Layers of this thickness in particular if they are produced in a dyebath which, in addition to at least one molybdenum and / or vanadium salt and at least one organically complex copper salt, additionally contain copper in a non-complex-bound form, have proven advantageous, for example when the temperature is influenced, in particular by exposure to sunlight where temperatures of 65 to 75 ° C or more have been measured. Under such stress, the colored oxide layer did not crack, the gray tone did not discolour, and yet this anodically produced, colored oxide layer forms sufficient protection against corrosive weather influences.

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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)
  • Other Surface Treatments For Metallic Materials (AREA)

Abstract

In processes for electrolytically colouring anodic oxide layers on aluminium or its alloys grey, grey colorations are obtained which are either not fast or whose hue cannot be reproducibly produced. In addition, electrolyte baths of complicated composition are used. Such disadvantages can be avoided if the electrolytic colouring bath contains at least one copper salt in the form of an organic complex and at least one molybdenum and/or vanadium salt. Using such a process it is possible to produce large-area parts made of aluminium or aluminium alloys having a uniform, tint-free grey tone which meet all the aesthetic requirements.

Description

Die Erfindung betrifft ein Verfahren zur elektrolytischen Graufärbung von anodischen Oxidschichten auf Aluminium oder Aluminiumlegierungen.The invention relates to a method for the electrolytic gray coloring of anodic oxide layers on aluminum or aluminum alloys.

Gleichzeitige elektrochemische Einlagerung von Metallen und organischen Farbstoffen im Anodisierbad führt nach der DE-OS 32 48 472 zu Färbungen der anodischen Oxidschicht. Durch Wahl komplementärer Farben von Metall und organischem Farbstoff lassen sich danach unbunte Farbtöne, unter ande­rem auch Grautöne, erzeugen. Nachteilig bei einem derarti­gen Färbeverfahren ist, dass die Färbung unter Lichteinwir­kung an Farbkraft verliert. Ein weiterer wesentlicher Nach­teil besteht darin, dass sich der organische Farbstoff wäh­rend der Abscheidung im Elektrolyt, insbesondere bei nied­rigen pH-Werten des Bades -- z.B. bei zinnhaltigem Bad mit einem ph-Wert um 1 -- zersetzt.Simultaneous electrochemical storage of metals and organic dyes in the anodizing bath leads to colorations of the anodic oxide layer according to DE-OS 32 48 472. By choosing complementary colors of metal and organic dye, achromatic colors, including gray tones, can be created. A disadvantage of such a dyeing process is that the dyeing loses its color under the influence of light. Another major disadvantage is that the organic dye is deposited in the electrolyte during the deposition, especially at low pH values of the bath - e.g. in a tin-containing bath with a pH value of 1 - decomposed.

Nach der DE-OS 23 64 405 lassen sich Grautöne durch eine Kombina­tionsfärbung, bei der eine elektrolytische Metallsalzfär­bung und nachfolgend eine Tauchbehandlung in wässriger Lö­sung einer Heteropolysäure aus Silizium oder Phosphor mit Molybdän oder Wolfram angewendet wird, erzeugen. Bei diesem Verfahren ist es schwierig, die zweite Stufe kontrolliert durchzuführen, was zur Folge hat, dass der erhaltene Grau­farbton nicht über das gesamte einzufärbende Aluminium- oder Aluminiumlegierungshalbzeug gleichmässig verteilt ist, und dass der Farbton nicht reproduzierbar getroffen werden kann, denn während des Sealings treten immer wieder Farb­tonveränderungen auf. Zudem ist die angeführte bevorzugte Zugabe von NaCl zum Färbebad korrosionstechnisch bedenk­lich.According to DE-OS 23 64 405, gray tones can be produced by a combination dyeing, in which an electrolytic metal salt dyeing and subsequently an immersion treatment in an aqueous solution of a heteropolyacid made of silicon or phosphorus with molybdenum or tungsten is used. With this method, it is difficult to carry out the second stage in a controlled manner, with the result that the gray color tone obtained is not distributed uniformly over the entire aluminum or aluminum alloy semi-finished product to be colored, and the color tone cannot be reproducibly achieved because during the sealing process changes in color again and again. In addition, the above-mentioned preferred addition of NaCl to the dyebath is questionable in terms of corrosion.

Das in der DE-AS 25 20 955 angeführte elektrolytische Fär­bebad führt unter anderem ebenfalls zu Graufärbungen. Das Bad enthält Metallsalze und Sperrschichtbildner wie Phos­phonsäuren und/oder Aminocarbonsäuren. Der Sperrschicht­bildner soll die Qualität der Oxidschicht unter Farbgebung verbessern. Mit Beispiel 26 wird ein Färbeverfahren unter Grautonbildung angegeben, bei dem ein Elektrolyt mit Amo­niummolybdat, Zinnsulfat, Schwefelsäure, Phosphonsäure, Glyzerin und Kresolschwefelsäure verwendet wird. Die Elek­trolytbadführung ist bei diesem vorgeschlagenen Verfahren wiederum sehr schwierig, da der Elektrolyt bereits kompli­ziert aufgebaut ist und damit die elektrochemisch ablaufen­den Reaktionen nur schwer beherrschbar sind. So können bei­spielsweise Ausfällungen nicht verhindert werden.The electrolytic dye bath mentioned in DE-AS 25 20 955 also leads, among other things, to gray coloring. The bath contains metal salts and barrier layer formers such as phosphonic acids and / or aminocarboxylic acids. The barrier layer should improve the quality of the oxide layer with coloring. Example 26 specifies a dyeing process with gray tone formation, in which an electrolyte with ammonium molybdate, tin sulfate, sulfuric acid, phosphonic acid, glycerol and cresol sulfuric acid is used. In this proposed method, the electrolyte bath guidance is again very difficult, since the electrolyte is already built up in a complicated manner and the electrochemical reactions are therefore difficult to control. For example, precipitation cannot be prevented.

Angesichts dieser Gegebenheiten haben sich die Erfinder die Aufgabe gesetzt, ein Verfahren der eingangs erwähnten Art zu schaffen, welches bei Anwendung eines einfachen, d.h. aus wenigen Verbindungen bestehenden Elektrolyten aufgebaut ist und reproduzierbare Grautonfärbungen erzeugt, die über die gesamte Werkstücksoberfläche von Auge praktisch keine Schwankungen erkennen lassen. Ein weiteres, von obiger Auf­gabenstellung an sich unabhängiges Ziel der Erfinder ist es, die Zusammensetzung des Elektrolyten so zu wählen, dass diese den heutigen allgemeinen Umweltschutzvorschriften ge­nügt.In view of these circumstances, the inventors have set themselves the task of creating a method of the type mentioned at the outset, which can be achieved using a simple, i.e. Electrolytes consisting of a few compounds are built up and produce reproducible shades of gray that practically show no fluctuations over the entire workpiece surface. Another aim of the inventors, which is independent of the above task, is to choose the composition of the electrolyte in such a way that it meets today's general environmental protection regulations.

Erfindungsgemäss wird die gestellte Aufgabe durch ein Ver­fahren gelöst, welches sich nach dem Wortlaut des Anspruchs 1 auszeichnet.According to the invention, the object is achieved by a method which is distinguished by the wording of claim 1.

Weitere Ausführungsformen des erfindungsgemässen Verfahrens sind durch die Merkmale der Ansprüche 2 bis 10 gekennzeich­net.Further embodiments of the method according to the invention are characterized by the features of claims 2 to 10.

Zur Bildung des/der organische(n) Komplex(e) können minde­stens eine aliphatische und/oder aromatische Carbon- und/oder Dicarbonsäure und/oder Aminocarbonsäure und/oder Alkanolamin verwendet werden.To form the organic complex (s), at least one aliphatic and / or aromatic carbon and / or dicarboxylic acid and / or aminocarboxylic acid and / or alkanolamine can be used.

Neben der Behebung der vorerwähnten Nachteile hat das er­findungsgemässe Verfahren den Vorteil, dass aufgrund der gleichmässigen Einfärbung grossflächige oder grossdimen­sionierte Aluminium oder Aluminiumlegierungsgegenstände mit einem Graufarbton versehen werden, der höchsten ästheti­schen Anforderungen genügt. So können beispielsweise Fas­sadenbleche im Architekturbereich danach gefertigt werden, ohne dass ein im Grauton variierender Farbeffekt auftritt. Oder es können nach dem Verfahren lange -- mehrere Meter lange -- Profilleisten mit einem über die ganze Länge gleichbleibenden Grauton versehen werden. Dies ist bei­spielsweise dann von Vorteil, wenn mehrere eingefärbte Pro­filleisten aus verschiedenen Färbechargen an einem Objekt angebracht werden. Ein mühsames Zusammensuchen von Profil­leisten aus verschiedenen Färbechargen mit etwa gleicher Grautonfärbung, wie es zumindest teilweise nach den vorbe­kannten Färbeverfahren notwendig ist, ist beim erfindungs­gemässen Verfahren somit entbehrlich.In addition to eliminating the aforementioned disadvantages, the method according to the invention has the advantage that, due to the uniform coloring, large-area or large-sized aluminum or aluminum alloy objects are provided with a gray color shade that meets the highest aesthetic requirements. For example, facade panels in the architectural sector can then be produced without a color effect that varies in gray. Or after the process, long - several meters long - profile strips can be provided with a gray tone that remains the same over the entire length. This is advantageous, for example, if several colored profile strips from different color batches are attached to an object. A tedious search for profile strips from different batches of dye with approximately the same shade of gray, as is at least partially necessary according to the previously known dyeing methods, is therefore unnecessary in the method according to the invention.

Darüber hinaus wirkt das erfindungsgemässe Verfahren in gleicher und einheitlicher Weise, d.h. ohne dass ein Unter­schied erkennbar ist, bei gewalztem und gepressten Alumi­nium oder Aluminiumlegierungsmaterial. Bereits wenige µm dicke anodische Oxidschichten können nach dem erfindungsge­mässen Verfahren mit einem einheitlichen Grauton versehen werden. Es hat sich insbesondere gezeigt, dass gefärbte Schichten von etwa 10 bis 25 µm für die gebräuchlichsten Anwendungszwecke besonders geeignet sind. Schichten dieser Dicke, insbesondere wenn sie in einem Färbebad erzeugt werden, welches neben mindestens einem Molybdän- und/oder Vanadiumsalz und mindestens einem organisch komplex gebun­denen Kupfersalz noch zusätzlich Kupfer in nicht komplex gebundener Form enthält, haben sich vorteilhaft bewährt, beispielsweise bei Temperaturbeeinflussung, insbesondere durch die Einstrahlung von Sonnenlicht, wo Temperaturen von 65 bis 75 °C oder mehr gemessen wurden. Unter derartiger Beanspruchung riss die eingefärbte Oxidschicht nicht auf, der Grauton verfärbte sich nicht und dennoch bildet diese anodisch erzeugte, eingefärbte Oxidschicht genügend Schutz vor korrosiven Witterungseinflüssen.In addition, the method according to the invention acts in the same and uniform manner, ie without a difference being discernible, in the case of rolled and pressed aluminum or aluminum alloy material. Anodic oxide layers that are only a few μm thick can be provided with a uniform shade of gray using the method according to the invention. It has been shown in particular that colored layers of approximately 10 to 25 μm are particularly suitable for the most common application purposes. Layers of this thickness, in particular if they are produced in a dyebath which, in addition to at least one molybdenum and / or vanadium salt and at least one organically complex copper salt, additionally contain copper in a non-complex-bound form, have proven advantageous, for example when the temperature is influenced, in particular by exposure to sunlight where temperatures of 65 to 75 ° C or more have been measured. Under such stress, the colored oxide layer did not crack, the gray tone did not discolour, and yet this anodically produced, colored oxide layer forms sufficient protection against corrosive weather influences.

Claims (10)

1. Verfahren zur elektrolytischen Graufärbung von anodi­schen Oxidschichten auf Aluminium oder Aluminiumlegie­rungen,

dadurch gekennzeichnet,

dass das elektrolytische Färbebad mindestens ein orga­nisch komplex gebundenes Kupfersalz sowie mindestens ein Molybdän- und/oder Vanadiumsalz enthält.1. Process for the electrolytic gray coloring of anodic oxide layers on aluminum or aluminum alloys,

characterized,

that the electrolytic dyebath contains at least one organically complex copper salt and at least one molybdenum and / or vanadium salt. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass das Bad zusätzlich Kupfer in nicht komplex gebundener Form enthält.2. The method according to claim 1, characterized in that the bath additionally contains copper in a non-complex bound form. 3. Verfahren nach einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, dass zur elektrolytischen Färbung Gleichstrom oder gleichgerichteter Wechselstrom verwen­det wird.3. The method according to any one of claims 1 or 2, characterized in that direct current or rectified alternating current is used for electrolytic coloring. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch ge­kennzeichnet, dass zur elektrolytischen Färbung Wech­selstrom verwendet wird.4. The method according to any one of claims 1 to 3, characterized in that alternating current is used for the electrolytic coloring. 5. Verfahren nach Anspruch 3 oder 4, dadurch gekennzeich­net, dass zur elektrolytischen Färbung Impulsstrom ver­wendet wird.5. The method according to claim 3 or 4, characterized in that pulse current is used for electrolytic coloring. 6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch ge­kennzeichnet, dass vor der Färbung eine anodische Vor­behandlung mittels Gleichstrom oder Impulsstrom im Elektrolytfärbebad durchgeführt wird.6. The method according to any one of claims 1 to 5, characterized in that an anodic pretreatment is carried out by means of direct current or pulse current in the electrolyte dye bath before the coloring. 7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch ge­kennzeichnet, dass die Grautonintensität und/oder Farb­verschiebung in Richtung rotgrau, braungrau, grüngrau oder blaugrau durch die Höhe der angelegten Spannung beeinflusst wird.7. The method according to any one of claims 1 to 6, characterized in that the gray tone intensity and / or color shift in the direction of red-gray, brown-gray, green-gray or blue-gray is influenced by the level of the applied voltage. 8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass die Spannung im Bereich von 5 bis 25 Volt liegt.8. The method according to claim 7, characterized in that the voltage is in the range of 5 to 25 volts. 9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch ge­kennzeichnet, dass als Gegenelektrodenmaterial Graphit verwendet wird.9. The method according to any one of claims 1 to 8, characterized in that graphite is used as the counter electrode material. 10. Verfahren nach einem der Ansprüche 1 bis 8, dadurch ge­kennzeichnet, dass als Gegenelektrodenmaterial rost­freier Stahl oder Kupfer verwendet wird.10. The method according to any one of claims 1 to 8, characterized in that stainless steel or copper is used as the counter electrode material.
EP88810254A 1987-04-30 1988-04-21 Process for the electrolytic grey coloring of anodic oxide layers on aluminium or aluminium alloys Withdrawn EP0289459A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH165187 1987-04-30
CH1651/87 1987-04-30

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EP0289459A1 true EP0289459A1 (en) 1988-11-02

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2111674A1 (en) * 1970-10-16 1972-06-09 Blasberg Gmbh & Co Kg Friedr
DE2128194A1 (en) * 1971-06-07 1973-01-04 Metalloxyd Gmbh Colouring oxide-coated aluminium - in electrolyte contg hexamethylene tetramine salts, and ammonium hypophosphite or phosphor
GB2053972A (en) * 1979-07-04 1981-02-11 Empresa Nacional Aluminio Electrolytic colouring of anodized aluminium
DE3522117A1 (en) * 1985-06-20 1987-01-02 Metall Und Oberflaechenchemie Surface treatment process for aluminium and its alloys

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2111674A1 (en) * 1970-10-16 1972-06-09 Blasberg Gmbh & Co Kg Friedr
DE2128194A1 (en) * 1971-06-07 1973-01-04 Metalloxyd Gmbh Colouring oxide-coated aluminium - in electrolyte contg hexamethylene tetramine salts, and ammonium hypophosphite or phosphor
GB2053972A (en) * 1979-07-04 1981-02-11 Empresa Nacional Aluminio Electrolytic colouring of anodized aluminium
DE3522117A1 (en) * 1985-06-20 1987-01-02 Metall Und Oberflaechenchemie Surface treatment process for aluminium and its alloys

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
GALVANOTECHNIK, Band 77, Nr. 9, 1986, Seiten 2123-2127, Saulgau, DE; T.L. SHARMA et al.: "Ein schnelles Verfahren zum elektrolytischen F{rben von Aluminium und seinen Legierungen" *

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