EP0347663B1 - Method for sealing-in anodised films on aluminium and aluminium alloys - Google Patents

Method for sealing-in anodised films on aluminium and aluminium alloys Download PDF

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Publication number
EP0347663B1
EP0347663B1 EP89110451A EP89110451A EP0347663B1 EP 0347663 B1 EP0347663 B1 EP 0347663B1 EP 89110451 A EP89110451 A EP 89110451A EP 89110451 A EP89110451 A EP 89110451A EP 0347663 B1 EP0347663 B1 EP 0347663B1
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Prior art keywords
solutions
acid
aluminium
aluminum
value
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German (de)
French (fr)
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EP0347663A1 (en
Inventor
Dieter Dr. Brodalla
Winfried Kirchhoff
Willi Dr. Wüst
Helmut Blum
Wolfgang Riedel
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Henkel AG and Co KGaA
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Henkel AG and Co KGaA
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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
    • 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
    • C25D11/24—Chemical after-treatment
    • C25D11/246—Chemical after-treatment for sealing layers

Definitions

  • the invention relates to an improved method for compacting decorative anodized oxide layers on aluminum and aluminum alloys in aqueous solutions at elevated temperatures.
  • the addition of certain phosphonic acids prevents the formation of disruptive aluminum hydroxide coatings (sealing coatings) on the surfaces.
  • anodically produced oxide layers are applied for the purpose of corrosion protection, which protect them from the effects of weather and other corrosive media. Furthermore, the anodized oxide layers are also applied in order to obtain a harder surface and thus to achieve increased wear resistance of the aluminum. Due to the intrinsic color of the oxide layers and their easy coloring, particularly decorative effects can be achieved.
  • the oxide layer is generated with direct current in solutions of sulfuric acid.
  • solutions of organic acids such as, for example, are also common Sulfophthalic acid or sulfanilic acid or mixtures thereof with sulfuric acid are used.
  • anodized oxide layers applied in this way do not meet all the requirements with regard to corrosion protection, since they have a very porous structure. For this reason, it is necessary to compact the oxide layers. This compression is often carried out with hot or boiling water and referred to as "sealing". This closes the pores and increases the protection against corrosion.
  • the surface pores in particular are closed, the oxide layer being restructured at the same time.
  • a more or less velvety, disruptive coating of hydrated aluminum oxide the so-called sealing coating, also forms on the entire surface. This is not touch-resistant, which greatly affects the decorative effect of the layer.
  • the sealing coating reduces the adhesive strength of the bonding of such aluminum parts and, due to the enlarged effective surface, promotes later contamination and corrosion.
  • DE-OS 22 11 553 describes a method for treating the surfaces of aluminum or aluminum alloys by anodic generation of oxide layers with subsequent densification in aqueous solutions at elevated temperatures.
  • the addition of certain phosphonic acids in conjunction with further additions of calcium ions largely prevents the formation of disruptive aluminum hydroxide deposits on the surfaces and avoids difficulties caused by hardness salts of the water.
  • the compression is carried out at temperatures between 90 ° C and the boiling temperature and a pH of 5.5 to 6.5.
  • Phosphonic acids or their water-soluble salts which form complexes with divalent metals are suitable for this process 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxyhexane-1,1-diphosphonic acid, 1-hydroxypropane-1,1-diphosphonic acid, 1-aminoethane-1,1-diphosphonic acid, dimethylaminomethane-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, Aminotrimethylenephosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid or 1-phosphono-1-methylsuccinic acid.
  • an optimal surface finish that meets decorative requirements cannot always be achieved on dark colored surfaces.
  • EP-OS 122 129 describes a method for compacting anodized aluminum surfaces with aqueous solutions with a pH of at least 7 in the presence of sealing deposit inhibitors.
  • Possible sealing coating inhibitors are: dextrins, acrylic acid, methacrylic acid, water-soluble polymers of acrylic or methacrylic acid lignin sulfonates, cycloaliphatic or aromatic polycarboxylic acids and cyclohexane-hexacarboxylic acid, water-soluble phosphonic acids complexing with divalent metals, reaction products with a sulfonated aromatic compound and sulfonated aromatic compounds or dimethylol urea or a mixture of formaldehyde and urea.
  • phosphonic acids preferably ethylenediamino-tetra- (methylenephosphonic acid), hexamethylenediamine-tetra (methylenephosphonic acid), n-propyliminobis (methylenephosphonic acid), benzene hexacarboxylic acid and salts thereof and the reaction products of sulfonated aromatic compounds with an aldehyde and / or dimethylol urea or a mixture of formaldehyde and urea.
  • no information is given about the anodizing conditions.
  • the classification of the surface layers in "Heavy Bloom" or "No Bloom” mentioned here is not suitable for adequately reproducing the finish assessment by a panel of experienced experts in the decoratively important architecture sector.
  • the object of the present invention is to provide an improved method for compacting decorative anodized oxide layers on surfaces of aluminum and aluminum alloys.
  • the above object is achieved with a method for compacting decorative anodized oxide layers on surfaces of aluminum and aluminum alloys in aqueous solutions containing phosphonic acids or their alkali metal salts and / or alkanolamine salts with a pH in the range from 5.5 to 8. 5 at temperatures between 80 ° C and the boiling temperature, characterized in that one selects the phosphonic acids from 1-phosphonopropane-1.2.3-tricarboxylic acid and / or 1.1-diphosphonopropane-2.3.-dicarboxylic acid.
  • water-soluble salts such as, in particular sodium, potassium, ammonium or alkanolamine salts, can also be used.
  • Normal water that is neither fully desalinated nor softened can be used to prepare the solutions. If demineralized or distilled or very soft water is used to prepare the solutions, it is not necessary, in contrast to the prior art known to date, to add calcium ions.
  • the process for compacting anodically produced oxide layers on aluminum and aluminum alloys in aqueous solutions containing phosphonic acids or their salt can be carried out at a pH of 5.5 to 8.5 at a temperature between 80 ° C. and the boiling point.
  • acids and / or alkalis can be used to adjust the pH of the solutions, which the person skilled in the art usually uses in such processes.
  • preferred are: acetic acid, sulfuric acid, ammonia, potassium hydroxide and triethanolamine.
  • Technical triethanolamine which usually contains small amounts of diethanolamine and monoethanolamine, can also be used.
  • the addition of strong acids is usually unnecessary, since the previous anodizing process usually leads to the introduction of sulfuric acid or acid sulfates into the compression bath.
  • the desired pH is usually stabilized by adding a buffer system, which is known to consist of the salt of a weak base and a strong acid, or a strong base and a weak acid, to the solutions.
  • solutions which have a pH in the range from 5.5 to 6.5.
  • the solutions acetic acid and ammonia and / or acetic acid and potassium hydroxide are added.
  • the buffer salts ammonium acetate and / or potassium acetate which are formed can also be added to the solutions as such.
  • solutions are used which have a pH in the range from above 6.5 to 8.5, particularly preferably in the range from 7.0 to 7.5.
  • solutions acetic acid and potassium hydroxide and / or acetic acid and triethanolamine are added.
  • the buffer salts potassium acetate and / or triethanolammonium acetate which are formed are additionally added to the solutions as such.
  • solutions used according to the invention must contain the PPT and / or DPD in a certain minimum amount. A certain maximum amount of phosphonic acid must also be observed, otherwise the surface quality will deteriorate.
  • the method for compacting anodically produced oxide layers on aluminum and aluminum alloys is characterized in that the solutions contain 0.003 to 0.1 g / l PPT and / or DPD.
  • the method is carried out with solutions which contain 0.005 to 0.025 g / l PPT and / or DPD.
  • At least about 1 ppm of aluminum ions in the form of a water-soluble aluminum compound are added to the solutions at the start of the compression process.
  • Suitable water-soluble aluminum compounds are, in particular, aluminum salts whose anions can be present in the compression solutions anyway, for example aluminum sulfate or aluminum acetate.
  • the amount of aluminum ions added is preferably 1 to 20 ppm, in particular 1 ppm. Such an addition significantly reduces the formation of iridescent phenomena on the surfaces.
  • the name of the aluminum alloy is given in accordance with DIN 1725; a profile AlMgSi 0.5 was used.
  • the profiles were degreased in an aqueous solution consisting of 5% P3-Almeco R 18 (alkaline cleaner containing borates, carbonates, phosphates and nonionic surfactants) at a temperature of 70 ° C. It was then pickled in a long-term pickle using 112 g / l of dissolved aluminum and 80 g / l of NaOH using P3-Almeco R 46 (pickling agent containing alkali, alcohols and salts of inorganic acids). P3-Almeco R 46 was dosed in a ratio of 1: 6 to NaOH. Pickling was carried out at 65 ° C. for about 15 minutes.
  • the subsequent anodization was carried out using the direct current sulfuric acid method; Bath composition: 200 g / l sulfuric acid, 10 g / l aluminum; Air injection 8 m3 / m. H; Temperature 20 ° C; DC voltage 15 V.
  • the anosidization time was about 3 min / ⁇ m layer build-up; ie the total anodizing times for the oxide layers of approximately 20 ⁇ m given in the examples below were approximately 45 to 55 minutes.
  • the profiles that were to be subjected to a visual inspection of the surface finish were still colored black. This was done in an electrolyte containing 18 g / l tin (II) sulfate, 25 g / l P3-Almecolor R S (iron (II) salts and organic sulfonic acids) and 20 g / l sulfuric acid with an alternating current of 16 V at 20 ° C in 10 min.
  • the profiles for the comparative examples were pretreated in an analogous manner and also compacted as described below.
  • the sealing layer preventers were used in concentrations of 2 g / l and compacted at temperatures of about 96 to 98 ° C.
  • the quality of the surface layer was determined by the so-called paint drop test with previous acid treatment in accordance with ISO standard 2143.
  • a removal test according to ISO 3210 was carried out.
  • the Y value was carried out in accordance with ISO standard 3913 using an anotest device Y-D from Fischer. The percentages below represent percentages by weight.
  • Examples 1 to 4 according to the invention were repeated, with sufficient aqueous aluminum sulfate solution being added to the solutions at the start of the compression process to give a concentration of 1 ppm of aluminum ions. In this way, iridescence of the surfaces treated in this way was effectively prevented.
  • the table shows that the compaction formulations according to the invention had an extremely good surface quality. It is also important that improved surface quality could be achieved with a shorter compaction time. This results in great energy savings since the compression was carried out in practically boiling aqueous solutions.

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  • Chemical & Material Sciences (AREA)
  • Metallurgy (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Liquid Crystal (AREA)
  • Laminated Bodies (AREA)
  • Catalysts (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Sealing Material Composition (AREA)
  • Detergent Compositions (AREA)

Abstract

The invention relates to a method for sealing-in decorative anodised films on aluminium and aluminium alloy surfaces in aqueous solutions containing phosphonic acids or their alkali metal and/or alkanolamine salts at elevated temperature in solutions containing 1-phosphonopropane-1,2,3-tricarboxylic acid and/or 1,1-3-diphosphonopropane-2,2-dicarboxylic acid as sealing coating inhibitor.

Description

Die Erfindung betrifft ein verbessertes Verfahren zum Verdichten von dekorativen anodisierten Oxidschichten auf Aluminium und Aluminiumlegierungen in wäßrigen Lösungen bei erhöhten Temperaturen. Dabei wird durch Zusatz bestimmter Phosphonsäuren die Bildung von störenden Aluminiumhydroxidbelägen (Sealingbelägen) auf den Oberflächen verhindert.The invention relates to an improved method for compacting decorative anodized oxide layers on aluminum and aluminum alloys in aqueous solutions at elevated temperatures. The addition of certain phosphonic acids prevents the formation of disruptive aluminum hydroxide coatings (sealing coatings) on the surfaces.

Auf dekorativen Aluminiumoberflächen, insbesondere in der Architektur, werden zum Zwecke des Korrosionsschutzes vielfach anodisch erzeugte Oxidschichten aufgebracht, die diese vor den Einflüssen der Witterung und anderer korrodierender Medien schützen. Des weiteren werden die anodisierten Oxidschichten auch aufgebracht, um eine härtere Oberfläche zu erhalten und damit eine erhöhte Verschleißfestigkeit des Aluminiums zu erreichen. Durch die Eigenfarbe der Oxidschichten bzw. ihre teilweise leichte Einfärbbarkeit lassen sich besonders dekorative Effekte erzielen.On decorative aluminum surfaces, particularly in architecture, anodically produced oxide layers are applied for the purpose of corrosion protection, which protect them from the effects of weather and other corrosive media. Furthermore, the anodized oxide layers are also applied in order to obtain a harder surface and thus to achieve increased wear resistance of the aluminum. Due to the intrinsic color of the oxide layers and their easy coloring, particularly decorative effects can be achieved.

Für das Aufbringen von dekorativen anodisierten Oxidschichten auf Oberflächen aus Aluminium sind eine Reihe von Verfahren bekannt. Beispielsweise erfolgt die Erzeugung der Oxidschicht mit Gleichstrom in Lösungen von Schwefelsäure. Häufig werden jedoch auch Lösungen organischer Säuren wie beispielsweise Sulfophthalsäure bzw. Sulfanilsäure oder deren Gemische mit Schwefelsäure verwendet. Derartig aufgebrachte anodisierte Oxidschichten erfüllen aber nicht alle Anforderungen im Hinblick auf den Korrosionsschutz, da sie eine sehr poröse Struktur aufweisen. Aus diesem Grunde ist es erforderlich, die Oxidschichten zu verdichten. Diese Verdichtung wird vielfach mit heißem bzw. siedendem Wasser vorgenommen und als "Sealing" bezeichnet. Hierdurch werden die Poren verschlossen und damit der Korrosionsschutz erhöht.A number of methods are known for applying decorative anodized oxide layers to aluminum surfaces. For example, the oxide layer is generated with direct current in solutions of sulfuric acid. However, solutions of organic acids such as, for example, are also common Sulfophthalic acid or sulfanilic acid or mixtures thereof with sulfuric acid are used. However, anodized oxide layers applied in this way do not meet all the requirements with regard to corrosion protection, since they have a very porous structure. For this reason, it is necessary to compact the oxide layers. This compression is often carried out with hot or boiling water and referred to as "sealing". This closes the pores and increases the protection against corrosion.

Bei der Verdichtung anodisch aufgebrachter Oxidschichten werden insbesondere die Oberflächenporen verschlossen, wobei gleichzeitig eine Umstrukturierung der Oxidschicht erfolgt. Daneben bildet sich aber auch auf der gesamten Fläche ein mehr oder weniger samtartiger, störender Belag aus hydratisiertem Aluminiumoxid, der sogenannte Sealingbelag. Dieser ist nicht griffest, wodurch der dekorative Effekt der Schicht stark beeinträchtigt wird. Ferner vermindert der Sealingbelag die Haftfestigkeit der Verklebung solcher Aluminiumteile und fördert durch die vergrößerte effektive Oberfläche spätere Verschmutzung und Korrosion.When anodically applied oxide layers are compacted, the surface pores in particular are closed, the oxide layer being restructured at the same time. In addition, a more or less velvety, disruptive coating of hydrated aluminum oxide, the so-called sealing coating, also forms on the entire surface. This is not touch-resistant, which greatly affects the decorative effect of the layer. Furthermore, the sealing coating reduces the adhesive strength of the bonding of such aluminum parts and, due to the enlarged effective surface, promotes later contamination and corrosion.

Die DE-OS 22 11 553 beschreibt ein Verfahren zur Behandlung der Oberflächen von Aluminium oder Aluminiumlegierungen durch anodische Erzeugung von Oxidschichten mit einer nachfolgenden Verdichtung in wäßrigen Lösungen bei erhöhten Temperaturen. Dabei wird durch Zusatz bestimmter Phosphonsäuren in Verbindung mit weiteren Zusätzen von Calciumionen die Bildung von störenden Aluminiumhydroxidbelägen auf den Oberflächen weitgehend verhindert sowie Schwierigkeiten durch Härtesalze des Wassers vermieden. Die Verdichtung wird bei Temperaturen zwischen 90 °C und der Siedetemperatur und einem pH-Wert von 5,5 bis 6,5 durchgeführt. Für dieses Verfahren kommen solche Phosphonsäuren, beziehungsweise deren wasserlösliche Salze in Betracht, die mit zweiwertigen Metallen Komplexe bilden, beispielsweise 1-Hydroxyethan-1,1-diphosphonsäure, 1-Hydroxyhexan-1,1-diphosphonsäure, 1-Hydroxypropan-1,1-diphosphonsäure, 1-Aminoethan-1,1-diphosphonsäure, Dimethylaminomethan-1,1-diphosphonsäure, Ethylendiamintetramethylenphosphonsäure, Aminotrimethylenphosphonsäure, 2-Phosphonobutan-1,2,4-tricarbonsäure oder 1-Phosphono-1-methylbernsteinsäure. Mit Hilfe dieses Verfahrens ist jedoch auf dunkelgefärbten Oberflächen ein optimales Oberflächenfinish, das dekorativen Ansprüchen genügt, nicht immer zu erzielen.DE-OS 22 11 553 describes a method for treating the surfaces of aluminum or aluminum alloys by anodic generation of oxide layers with subsequent densification in aqueous solutions at elevated temperatures. The addition of certain phosphonic acids in conjunction with further additions of calcium ions largely prevents the formation of disruptive aluminum hydroxide deposits on the surfaces and avoids difficulties caused by hardness salts of the water. The compression is carried out at temperatures between 90 ° C and the boiling temperature and a pH of 5.5 to 6.5. Phosphonic acids or their water-soluble salts which form complexes with divalent metals, for example, are suitable for this process 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxyhexane-1,1-diphosphonic acid, 1-hydroxypropane-1,1-diphosphonic acid, 1-aminoethane-1,1-diphosphonic acid, dimethylaminomethane-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, Aminotrimethylenephosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid or 1-phosphono-1-methylsuccinic acid. With the help of this process, however, an optimal surface finish that meets decorative requirements cannot always be achieved on dark colored surfaces.

Die EP-OS 122 129 beschreibt ein Verfahren zur Verdichtung von anodisierten Aluminiumoberflächen mit wäßrigen Lösungen mit einem pH-Wert von wenigstens 7 in Anwesenheit von Sealingbelagverhinderern. Als Sealingbelagverhinderer kommen hierbei in Frage: Dextrine, Acrylsäure, Methacrylsäure, wasserlösliche Polymere von Acrylsäure- oder Methacrylsäure-Ligninsulfonaten, cycloaliphatische oder aromatische Polycarbonsäuren und Cyclohexan-hexacarbonsäure, wasserlösliche, mit zweiwertigen Metallen komplexbildende Phosphonsäuren, Reaktionsprodukte von sulfonierten aromatischen Verbindungen mit einem Aldehyd und/oder Dimethylolharnstoff oder einem Gemisch aus Formaldehyd und Harnstoff. Von diesen sind insbesondere bevorzugt: Phosphonsäuren, vorzugsweise Ethylendiamino-tetra-(methylenphosphonsäure), Hexamethylendiamin-tetra(methylenphosphonsäure), n-Propyliminobis(methylenphosphonsäure), die Benzolhexacarbonsäure sowie deren Salze und die Reaktionsprodukte von sulfonierten aromatischen Verbindungen mit einem Aldehyd und/oder Dimethylolharnstoff oder einem Gemisch aus Formaldehyd und Harnstoff. In den Beispielen werden jedoch keine Angaben über die Anodisierungsbedingungen gemacht. Zudem ist die hier genannte Klassifizierung der Oberflächenschichten in "Heavy Bloom" oder "No Bloom" nicht geeignet, die Finishbeurteilung durch ein Panel erfahrener Fachleute auf dem dekorativ bedeutsamen Architektursektor ausreichend bestimmt wiederzugeben.EP-OS 122 129 describes a method for compacting anodized aluminum surfaces with aqueous solutions with a pH of at least 7 in the presence of sealing deposit inhibitors. Possible sealing coating inhibitors are: dextrins, acrylic acid, methacrylic acid, water-soluble polymers of acrylic or methacrylic acid lignin sulfonates, cycloaliphatic or aromatic polycarboxylic acids and cyclohexane-hexacarboxylic acid, water-soluble phosphonic acids complexing with divalent metals, reaction products with a sulfonated aromatic compound and sulfonated aromatic compounds or dimethylol urea or a mixture of formaldehyde and urea. Of these, the following are particularly preferred: phosphonic acids, preferably ethylenediamino-tetra- (methylenephosphonic acid), hexamethylenediamine-tetra (methylenephosphonic acid), n-propyliminobis (methylenephosphonic acid), benzene hexacarboxylic acid and salts thereof and the reaction products of sulfonated aromatic compounds with an aldehyde and / or dimethylol urea or a mixture of formaldehyde and urea. In the examples, however, no information is given about the anodizing conditions. In addition, the classification of the surface layers in "Heavy Bloom" or "No Bloom" mentioned here is not suitable for adequately reproducing the finish assessment by a panel of experienced experts in the decoratively important architecture sector.

Demgemäß liegt der vorliegenden Erfindung die Aufgabe zugrunde, ein verbessertes Verfahren zum Verdichten von dekorativen anodisierten Oxidschichten auf Oberflächen von Aluminium und Aluminiumlegierungen zur Verfügung zu stellen.Accordingly, the object of the present invention is to provide an improved method for compacting decorative anodized oxide layers on surfaces of aluminum and aluminum alloys.

Die Lösung der vorstehend genannten Aufgabe wird erreicht mit einem Verfahren zum Verdichten von dekorativen anodisierten Oxidschichten auf Oberflächen von Aluminium und Aluminiumlegierungen in wäßrigen, Phosphonsäuren oder deren Alkalimetallsalze und/oder Alkanolaminsalze enthaltende Lösungen mit einem pH-Wert im Bereich von 5,5 bis 8,5 bei Temperaturen zwischen 80 °C und der Siedetemperatur, dadurch gekennzeichnet, daß man die Phosphonsäuren auswählt aus 1-Phosphonopropan-1.2.3-tricarbonsäure und/oder 1.1-Diphosphonopropan-2.3.-dicarbonsäure.The above object is achieved with a method for compacting decorative anodized oxide layers on surfaces of aluminum and aluminum alloys in aqueous solutions containing phosphonic acids or their alkali metal salts and / or alkanolamine salts with a pH in the range from 5.5 to 8. 5 at temperatures between 80 ° C and the boiling temperature, characterized in that one selects the phosphonic acids from 1-phosphonopropane-1.2.3-tricarboxylic acid and / or 1.1-diphosphonopropane-2.3.-dicarboxylic acid.

Der Vorteil bei der erfindungsgemäßen Verwendung von 1-Phosphonopropan-1.2.3-tricarbonsäure, nachstehend mit "PPT" bezeichnet, und/oder 1.1-Diphosphonopropan-2.3-dicarbonsäure, nachstehend mit "DPD" bezeichnet, in Verfahren zum Verdichten von dekorativen anodisch erzeugten Oxidschichten auf Aluminium und Aluminiumlegierungen besteht insbesondere darin, daß erfindungsgemäß hergestellte Oberflächen bei der Finish-Beurteilung, d.h. der visuellen Abmusterung des Oberflächenaussehens und des Verhaltens in der Freibewitterung, gegenüber nach dem Stand der Technik mit anderen Phosphonsäuren hergestellten dekorativen Oberflächen aus Aluminium und Aluminiumlegierungen deutlich verbessert sind. Auch bei erhöhten pH-Werten oberhalb von pH 7 sind dekorative Oberflächen ohne irisierende Erscheinungen herstellbar. Dabei werden gegenüber nach dem Stand der Technik hergestellten dekorativen Oberflächen bessere Werte in den üblichen Qualitätstests erzielt beziehungsweise die Qualitätskriterien in kürzeren Zeiten erfüllt.The advantage of the use according to the invention of 1-phosphonopropane-1.2.3-tricarboxylic acid, hereinafter referred to as "PPT", and / or 1.1-diphosphonopropane-2.3-dicarboxylic acid, hereinafter referred to as "DPD", in processes for compacting decorative anodically produced Oxide layers on aluminum and aluminum alloys consist, in particular, in the fact that surfaces produced according to the invention in the finish assessment, ie the visual matching of the surface appearance and behavior in outdoor weathering, are significantly improved compared to decorative surfaces made of aluminum and aluminum alloys produced with other phosphonic acids in the prior art are. Even at elevated pH values above pH 7, decorative surfaces can be produced without iridescent phenomena. Compared to decorative surfaces manufactured according to the state of the art, better values are achieved in the usual quality tests or the quality criteria are met in shorter times.

Anstelle der angeführten Phosphonsäuren können auch deren wasserlösliche Salze wie insbesondere Natrium-, Kalium-, Ammonium-, oder Alkanolaminsalze verwendet werden.Instead of the phosphonic acids mentioned, their water-soluble salts, such as, in particular sodium, potassium, ammonium or alkanolamine salts, can also be used.

Für den Ansatz der Lösungen kann normales Wasser verwendet werden, das weder vollentsalzt noch enthärtet ist. Wenn vollentsalztes bzw. destilliertes oder sehr weiches Wasser zum Ansatz der Lösungen verwendet wird, ist, im Gegensatz zum bisher bekannten Stand der Technik, ein Zusatz von Calciumionen nicht erforderlich.Normal water that is neither fully desalinated nor softened can be used to prepare the solutions. If demineralized or distilled or very soft water is used to prepare the solutions, it is not necessary, in contrast to the prior art known to date, to add calcium ions.

Erfindungsgemäß kann das Verfahren zum Verdichten von anodisch erzeugten Oxidschichten auf Aluminium und Aluminiumlegierungen in wäßrigen, Phosphonsäuren oder deren Salz enthaltenden Lösungen bei einem pH-Wert von 5,5 bis 8,5 bei einer Temperatur zwischen 80 °C und der Siedetemperatur durchgeführt werden. Zur Einstellung des pH-Wertes der Lösungen können - je nach dem gewünschten pH-Wert - Säuren und/oder Laugen Verwendung finden, die der Fachmann bei derartigen Verfahren üblicherweise einsetzt. Im Sinne des erfindungsgemäßen Verfahrens sind hierfür bevorzugt: Essigsäure, Schwefelsäure, Ammoniak, Kaliumhydroxid und Triethanolamin. Technisches Triethanolamin, des üblicherweise geringe Mengen an Diethanolamin und Monoethanolamin enthält, kann gleichfalls Verwendung finden. Die Zugabe einer starken Säuren erübrigt sich meist, da es aufgrund des vorangegangenen Anodisierprozesses in der Regel zur Einschleppung von Schwefelsäure beziehungsweise sauren Sulfaten in das Verdichtungsbad kommt. Die Stabilisierung des gewünschten pH-Wertes erfolgt üblicherweise durch Zugabe eines Puffersystems, das bekanntlich aus dem Salz einer schwachen Base und einer starken Säuren, beziehungsweise einer starken Base und einer schwachen Säure besteht, zu den Lösungen.According to the invention, the process for compacting anodically produced oxide layers on aluminum and aluminum alloys in aqueous solutions containing phosphonic acids or their salt can be carried out at a pH of 5.5 to 8.5 at a temperature between 80 ° C. and the boiling point. Depending on the desired pH value, acids and / or alkalis can be used to adjust the pH of the solutions, which the person skilled in the art usually uses in such processes. For the purposes of the process according to the invention, preferred are: acetic acid, sulfuric acid, ammonia, potassium hydroxide and triethanolamine. Technical triethanolamine, which usually contains small amounts of diethanolamine and monoethanolamine, can also be used. The addition of strong acids is usually unnecessary, since the previous anodizing process usually leads to the introduction of sulfuric acid or acid sulfates into the compression bath. The desired pH is usually stabilized by adding a buffer system, which is known to consist of the salt of a weak base and a strong acid, or a strong base and a weak acid, to the solutions.

Gemäß einer bevorzugten Ausführungsform der vorliegenden Erfindung wird mit Lösungen gearbeitet, die einen pH-Wert im Bereich von 5,5 bis 6,5 aufweisen. Zur Einstellung des pH-Wertes in diesem Bereich setzt man den Lösungen Essigsäure und Ammoniak und/oder Essigsäure und Kaliumhydroxid zu. Zur Stabilisierung des pH-Wertes in diesem Bereich können den Lösungen auch zusätzlich die sich bildenden Puffersalze Ammoniumacetat und/oder Kaliumacetat als solche zugefügt werden.According to a preferred embodiment of the present invention, solutions are used which have a pH in the range from 5.5 to 6.5. To adjust the pH in this range, the solutions acetic acid and ammonia and / or acetic acid and potassium hydroxide are added. To stabilize the pH in this range, the buffer salts ammonium acetate and / or potassium acetate which are formed can also be added to the solutions as such.

Gemäß einer weiteren bevorzugten Ausführungsform der vorliegenden Erfindung wird mit Lösungen gearbeitet, die einen pH-Wert im Bereich von oberhalb 6,5 bis 8,5, besonders bevorzugt im Bereich von 7,0 bis 7,5, aufweisen. Zur Einstellung des pH-Wertes in diesem Bereich setzt man den Lösungen Essigsäure und Kaliumhydroxid und/oder Essigsäure und Triethanolamin zu. Auch hierbei gilt, daß man zur Stabilisierung des pH-Wertes in diesem Bereich den Lösungen zusätzlich die sich bildenden Puffersalze Kaliumacetat und/oder Triethanolammoniumacetat als solche zusetzt.According to a further preferred embodiment of the present invention, solutions are used which have a pH in the range from above 6.5 to 8.5, particularly preferably in the range from 7.0 to 7.5. To adjust the pH in this range, the solutions acetic acid and potassium hydroxide and / or acetic acid and triethanolamine are added. It also applies here that in order to stabilize the pH in this range, the buffer salts potassium acetate and / or triethanolammonium acetate which are formed are additionally added to the solutions as such.

Die Durchführung des erfindungsgemäßen Verfahrens im Sinne der vorstehenden, bevorzugten Ausführungsformen führt zu einem besonders guten Finish der behandelten Oberflächen.Carrying out the method according to the invention in the sense of the above preferred embodiments leads to a particularly good finish of the treated surfaces.

Damit die erfindungsgemäß hergestellten anodisch erzeugten Oxidschichten die oben genannten Vorteile gegenüber dem Stand der Technik aufweisen, müssen erfindungsgemäß verwendete Lösungen die PPT und/oder DPD in einer gewissen Mindestmenge enthalten. Ebenso ist eine gewisse Höchstmenge an Phosphonsäure einzuhalten, da anderenfalls eine Verschlechterung der Oberflächenqualität auftritt. Gemäß der vorliegenden Erfindung ist das Verfahren zum Verdichten von anodisch erzeugten Oxidschichten auf Aluminium und Aluminiumlegierungen dadurch gekennzeichnet, daß die Lösungen 0,003 bis 0,1 g/l PPT und/oder DPD enthalten.In order for the anodically produced oxide layers produced according to the invention to have the abovementioned advantages over the prior art, solutions used according to the invention must contain the PPT and / or DPD in a certain minimum amount. A certain maximum amount of phosphonic acid must also be observed, otherwise the surface quality will deteriorate. According to the present invention, the method for compacting anodically produced oxide layers on aluminum and aluminum alloys is characterized in that the solutions contain 0.003 to 0.1 g / l PPT and / or DPD.

Gemäß einer bevorzugten Ausführungsform der vorliegenden Erfindung wird das Verfahren mit Lösungen durchgeführt, die 0,005 bis 0,025 g/l PPT und/oder DPD enthalten.According to a preferred embodiment of the present invention, the method is carried out with solutions which contain 0.005 to 0.025 g / l PPT and / or DPD.

Durch das neue Verfahren ist es nunmehr möglich, die Ausbildung von Sealingbelägen in verbesserter Weise zu verhindern, ohne daß die dekorative anodisch erzeugte Oxidschicht beeinträchtigt wird. Schwierigkeiten durch Härtebildner des Wassers treten nicht auf, so daß vorteilhafterweise auch nichtentsalztes oder nichtenthärtetes Wasser verwendet werden kann. Ausfällungen von Härtebildnern des Wassers werden weitgehend vermieden oder bei Wassern hoher Härte bilden sich nur flockige, schwere Niederschläge, die sich nicht auf die verdichteten Teile, sondern am Boden absetzen und aus den Bädern leicht ausgespült werden können.With the new method it is now possible to prevent the formation of sealing coatings in an improved manner without the decorative anodically produced oxide layer being impaired. Difficulties due to water hardness do not occur, so that non-demineralized or non-softened water can advantageously also be used. Precipitation of water hardness formers is largely avoided, or water with high hardness only forms flocculent, heavy precipitates, which do not settle on the compacted parts, but on the bottom and can be easily rinsed out of the baths.

Nach einer weiteren bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens setzt man den Lösungen zu Beginn des Verdichtungsprozesses mindestens etwa 1 ppm Aluminium-Ionen in Form einer wasserlöslichen Aluminiumverbindung zu. Als wasserlösliche Aluminiumverbindungen kommen hierbei insbesondere solche Aluminiumsalze in Frage, deren Anionen sich ohnehin in den Verdichtungslösungen befinden können, beispielsweise Aluminiumsulfat oder Aluminiumacetat. Vorzugsweise beträgt die Zugabemenge an Aluminium-Ionen 1 bis 20 ppm, insbesondere 1 ppm. Durch einen solchen Zusatz wird die Bildung von irisierenden Erscheinungen auf den Oberflächen signifikant vermindert.According to a further preferred embodiment of the process according to the invention, at least about 1 ppm of aluminum ions in the form of a water-soluble aluminum compound are added to the solutions at the start of the compression process. Suitable water-soluble aluminum compounds are, in particular, aluminum salts whose anions can be present in the compression solutions anyway, for example aluminum sulfate or aluminum acetate. The amount of aluminum ions added is preferably 1 to 20 ppm, in particular 1 ppm. Such an addition significantly reduces the formation of iridescent phenomena on the surfaces.

Insgesamt gesehen bedingt das erfindungsgemäße Verfahren eine deutliche Verbesserung des Aussehens der behandelten Oberflächen, es bleiben keine Ablaufspuren sichtbar.All in all, the method according to the invention results in a significant improvement in the appearance of the treated surfaces;

BeispieleExamples

In den nachfolgenden Beispielen erfolgt die Bezeichnung der Aluminiumlegierung gemäß DIN 1725; verwendet wurde ein Profil AlMgSi 0,5.In the following examples, the name of the aluminum alloy is given in accordance with DIN 1725; a profile AlMgSi 0.5 was used.

Die Profile wurden in einer wäßrigen Lösung, bestehend aus 5 % P₃-AlmecoR 18 (alkalischer Reiniger, enthaltend Borate, Carbonate, Phosphate und nichtionische Tenside) bei einer Temperatur von 70 °C entfettet. Anschließend wurde in einer Langzeitbeize unter Verwendung von 112 g/l gelöstes Aluminium und 80 g/l NaOH unter Verwendung von P₃-AlmecoR 46 (Beizmittel, enthaltend Alkali, Alkohole und Salze anorganischer Säuren) gebeizt. P₃-AlmecoR 46 wurde im Verhältnis 1 : 6 zu NaOH dosiert. Bei 65 °C wurde etwa 15 min gebeizt.The profiles were degreased in an aqueous solution consisting of 5% P₃-Almeco R 18 (alkaline cleaner containing borates, carbonates, phosphates and nonionic surfactants) at a temperature of 70 ° C. It was then pickled in a long-term pickle using 112 g / l of dissolved aluminum and 80 g / l of NaOH using P₃-Almeco R 46 (pickling agent containing alkali, alcohols and salts of inorganic acids). P₃-Almeco R 46 was dosed in a ratio of 1: 6 to NaOH. Pickling was carried out at 65 ° C. for about 15 minutes.

Anschließend wurde unter Verwendung einer wäßrigen Lösung, enthaltend 5 % P₃-AlmecoR 90 (Dekapiermittel, enthaltend Salze anorganischer Säuren sowie anorganische Säuren), bei Raumtemperatur im Verlauf von 5 min dekapiert.Subsequently, using an aqueous solution containing 5% P₃-Almeco R 90 (pickling agent, containing salts of inorganic acids and inorganic acids), was picked up at room temperature over a period of 5 minutes.

Nach jedem Verfahrensschritt wurden die Profile mit entionisiertem Wasser gründlich gespült.After each process step, the profiles were rinsed thoroughly with deionized water.

Die anschließende Anodisierung wurde nach dem Gleichstrom-Schwefelsäure-Verfahren vorgenommen;
Badzusammensetzung: 200 g/l Schwefelsäure, 10 g/l Aluminium; Lufteinblasung 8 m³/m . h; Temperatur 20 °C; Gleichspannung 15 V. Die Anosidierdauer betrug etwa 3 min/µm Schichtaufbau; d.h. die Gesamtanodisierzeiten für die in den nachstehenden Beispielen angegebene Oxidschichten von ca. 20 µm lagen bei etwa 45 bis 55 min.The subsequent anodization was carried out using the direct current sulfuric acid method;
Bath composition: 200 g / l sulfuric acid, 10 g / l aluminum; Air injection 8 m³ / m. H; Temperature 20 ° C; DC voltage 15 V. The anosidization time was about 3 min / µm layer build-up; ie the total anodizing times for the oxide layers of approximately 20 μm given in the examples below were approximately 45 to 55 minutes.

Die Profile, die einer visuellen Abmusterung des Oberflächenfinish unterzogen werden sollten, wurden noch schwarz gefärbt. Dies erfolgte in einem Elektrolyten, der 18 g/l Zinn(II)-sulfat, 25 g/l P3-AlmecolorRS (Eisen(II)-salze und organische Sulfonsäuren) und 20 g/l Schwefelsäure enthielt, mit Wechselstrom von 16 V bei 20 °C in 10 min.The profiles that were to be subjected to a visual inspection of the surface finish were still colored black. This was done in an electrolyte containing 18 g / l tin (II) sulfate, 25 g / l P3-Almecolor R S (iron (II) salts and organic sulfonic acids) and 20 g / l sulfuric acid with an alternating current of 16 V at 20 ° C in 10 min.

Nach erneutem gründlichem Spülen mit entionisiertem Wasser erfolgte nun die erfindungsgemäße Verdichtung.After thorough rinsing again with deionized water, the compaction according to the invention now took place.

Die Profile für die Vergleichsbeispiele wurden in analoger Weise vorbehandelt und ebenfalls wie nachstehend beschrieben verdichtet. Die Sealingbelag-Verhinderer wurden jeweils in Konzentrationen von 2 g/l eingesetzt und bei Temperaturen von etwa 96 bis 98 °C verdichtet.The profiles for the comparative examples were pretreated in an analogous manner and also compacted as described below. The sealing layer preventers were used in concentrations of 2 g / l and compacted at temperatures of about 96 to 98 ° C.

Die Qualität der Oberflächenschicht wurde durch den sogenannten Farbtropfentest mit vorheriger Säurebehandlung nach der Iso-Norm 2143 bestimmt. Zusätzlich wurde eine Abtragtest nach Iso-Norm 3210 durchgeführt. Der Y-Wert wurde nach der Iso-Norm 3913 mit einem Anotestgerät Y-D der Firma Fischer durchgeführt. Die Prozentangaben stehen nachfolgend für Gewichtsprozente.The quality of the surface layer was determined by the so-called paint drop test with previous acid treatment in accordance with ISO standard 2143. In addition, a removal test according to ISO 3210 was carried out. The Y value was carried out in accordance with ISO standard 3913 using an anotest device Y-D from Fischer. The percentages below represent percentages by weight.

Als wichtigstes und entscheidendes Kriterium zur Bestimmung der dekorativen Wirkung der Oberflächengüte von schwarzgefärbten Profilen wurden die verdichteten Oberflächen durch ein Panel erfahrener Fachleute visuell begutachtet. Die nachfolgende Tabelle gibt unter anderem die Oberflächengüte der Beurteilung durch das Panel von Fachleuten auf dem Gebiet der dekorativen Oberflächentechnik wieder (siehe "Beurteilung").As the most important and decisive criterion for determining the decorative effect of the surface quality of black colored profiles, the compacted surfaces were visually inspected by a panel of experienced experts. The table below shows, among other things, the surface quality of the assessment by the panel of experts in the field of decorative surface technology (see "Assessment").

Vergleichsbeispiel 1Comparative Example 1

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 0,7 % des Pentanatriumsalzes der Cyclohexan-hexacarbonsäure, wurde bei einem pH-Wert im Bereich von 5,8 bis 6 im Verlauf von 60, 40 und 20 min verdichtet. Die nachfolgende Tabelle gibt die erhaltenen Werte wieder.Using 2 g / l of an aqueous solution containing 0.7% of the pentasodium salt of cyclohexane-hexacarboxylic acid, the mixture was compacted at a pH in the range from 5.8 to 6 over the course of 60, 40 and 20 min. The table below shows the values obtained.

Vergleichsbeispiel 2Comparative Example 2

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 0,7 % des Pentanatriumsalzes der Cyclohexan-hexacarbonsäure, wurde bei einem pH-Wert im Bereich von 7,0 bis 7,5 im Verlauf von 60, 40 und 20 min verdichtet.Using 2 g / l of an aqueous solution containing 0.7% of the pentasodium salt of cyclohexane-hexacarboxylic acid, the mixture was compacted at a pH in the range from 7.0 to 7.5 over the course of 60, 40 and 20 min.

Beispiel 1example 1

Unter Verwendung von 2 g/l einer Lösung, enthaltend 0,8 % 1.1-Diphosphonopropan-2.3-dicarbonsäure (94,2 %ig) und 15 % Ammoniumacetat, wurde bei einem pH-Wert im Bereich von 5,8 bis 6,2 im Verlauf von 60, 40 und 20 min verdichtet. Die nachfolgende Tabelle gibt die erhaltenen Werte wieder.Using 2 g / l of a solution containing 0.8% of 1,1-diphosphonopropane-2,3-dicarboxylic acid (94.2%) and 15% of ammonium acetate, the pH was in the range from 5.8 to 6.2 compressed over the course of 60, 40 and 20 min. The table below shows the values obtained.

Beispiel 2Example 2

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 0,8 % 1.1-Diphosphonopropan-2.3-dicarbonsäure (94,2 %ig) und 5 % Triethanolamin, wurde wie oben angegeben verdichtet. Die erhaltenen Werte sind der Tabelle zu entnehmen.Using 2 g / l of an aqueous solution containing 0.8% of 1,1-diphosphonopropane-2,3-dicarboxylic acid (94.2%) and 5% of triethanolamine, the mixture was compacted as indicated above. The values obtained are shown in the table.

Beispiel 3Example 3

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 0,7 % 1-Phosphonopropan-1.2.3-tricarbonsäure und 15 % Ammoniumacetat, wurde wie oben beschrieben verdichtet. Die nachfolgende Tabelle gibt die erhaltenen Werte wieder.Using 2 g / l of an aqueous solution containing 0.7% 1-phosphonopropane-1.2.3-tricarboxylic acid and 15% ammonium acetate, was compacted as described above. The table below shows the values obtained.

Beispiel 4Example 4

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 0,7 % 1-Phosphonopropan-1.2.3-tricarbonsäure und 5 % Triethanolamin, wurde wie oben beschrieben verdichtet. Die nachstehende Tabelle gibt die erhaltenen Werte wieder.Using 2 g / l of an aqueous solution containing 0.7% 1-phosphonopropane-1.2.3-tricarboxylic acid and 5% triethanolamine, the mixture was compacted as described above. The table below shows the values obtained.

Vergleichsbeispiel 3Comparative Example 3

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 1,3 % 2-Phosphonobutan-1,2,4-tricarbonsäure (50 %ig) und 15 % Ammoniumacetat, wurde wie oben angegeben verdichtet. Die nachstehende Tabelle gibt die erhaltenen Werte wieder.Using 2 g / l of an aqueous solution containing 1.3% 2-phosphonobutane-1,2,4-tricarboxylic acid (50%) and 15% ammonium acetate, the mixture was compacted as indicated above. The table below shows the values obtained.

Vergleichsbeispiel 4Comparative Example 4

Unter Verwendung von 2 g/l einer wäßrigen Lösung, enthaltend 1,3 % 2-Phosphonobutan-1,2,4-tricarbonsäure (50 %ig) und 5 % Triethanolamin, wurde wie oben angegeben verdichtet. Die nachstehende Tabelle gibt die erhaltenen Werte wieder.Using 2 g / l of an aqueous solution containing 1.3% 2-phosphonobutane-1,2,4-tricarboxylic acid (50%) and 5% triethanolamine, the mixture was compacted as indicated above. The table below shows the values obtained.

Die erfindungsgemäßen Beispiele 1 bis 4 wurden wiederholt, wobei den Lösungen zu Beginn des Verdichtungsprozesses soviel einer wäßrigen Aluminiumsulfat-Lösung zugegeben wurde, daß eine Konzentration von 1 ppm an Aluminium-Ionen in denselben resultierte. Auf diese Weise wurde ein Irisieren der so behandelten Oberflächen wirksam verhindert.

Figure imgb0001
Figure imgb0002
 Examples 1 to 4 according to the invention were repeated, with sufficient aqueous aluminum sulfate solution being added to the solutions at the start of the compression process to give a concentration of 1 ppm of aluminum ions. In this way, iridescence of the surfaces treated in this way was effectively prevented.
Figure imgb0001
Figure imgb0002

Der Tabelle ist zu entnehmen, daß die erfindungsgemäßen Verdichtungsrezepturen eine ausgesprochen gute Oberflächengüte aufwiesen. Weiterhin ist bedeutsam, daß bei kürzerer Verdichtungszeit verbesserte Oberflächengüten erzielt werden konnten. Dies bewirkt eine große Energieeinsparung, da die Verdichtung in praktisch siedenden wäßrigen Lösungen durchgeführt wurde.The table shows that the compaction formulations according to the invention had an extremely good surface quality. It is also important that improved surface quality could be achieved with a shorter compaction time. This results in great energy savings since the compression was carried out in practically boiling aqueous solutions.

Claims (10)

  1. A process for sealing decorative anodized oxide coatings on surfaces of aluminium and aluminium alloys in aqueous solutions containing phosphonic acids or alkali metal and/or alkanolamine salts thereof with a pH value of 5.5 to 8.5 at temperatures between 80°C and the boiling temperature, characterized in that the phosphonic acids are selected from 1-phosphonopropane-1,2,3-tricarboxylic acid and/or 1,1-diphosphonopropane-2,3-dicarboxylic acids.
  2. A process as claimed in claim 1, characterized in that the solutions have a pH value of 5.5 to 6.5.
  3. A process as claimed in claim 2, characterized in that the pH value of the solutions is adjusted by addition of acetic acid and ammonia and/or acetic acid and potassium hydroxide.
  4. A process as claimed in claim 2 or 3, characterized in that ammonium acetate and/or potassium acetate is/are added to the solutions.
  5. A process as claimed in claim 1, characterized in that the solutions have a pH value in the range above 6.5 to 8.5 and preferably in the range from 7.0 to 7.5.
  6. A process as claimed in claim 5, characterized in that the pH value of the solutions is adjusted by addition of acetic acid and triethanolamine and/or acetic acid and potassium hydroxide.
  7. A process as claimed in claim 5 or 6, characterized in that triethanolammmonium acetate and/or potassium acetate is/are added to the solutions.
  8. A process as claimed in any of claims 1 to 7, characterized in that the solutions contain 0.003 to 0.1 g/l 1-phosphonopropane-1,2,3-tricarboxylic acid and/or 1,1-diphosphonopropane-2,3-dicarboxylic acid.
  9. A process as claimed in any of claims 1 to 7, characterized in that the solutions contain 0.005 to 0.025 g/l 1-phosphonopropane-1,2,3-tricarboxylic acid and/or 1,1-diphosphonopropane-2,3-dicarboxylic acid.
  10. A process as claimed in any of claims 1 to 9, characterized in that at least 1 ppm aluminium ions are added to the solutions at the beginning.
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NO892509L (en) 1989-12-19
NO176928C (en) 1995-06-21
ZA894616B (en) 1990-02-28
JPH0243397A (en) 1990-02-13
NO892509D0 (en) 1989-06-16
US4939001A (en) 1990-07-03
DE58905303D1 (en) 1993-09-23
ATE93281T1 (en) 1993-09-15
AU609313B2 (en) 1991-04-26
AU3647889A (en) 1989-12-21
EP0347663A1 (en) 1989-12-27
CA1338442C (en) 1996-07-09
TR23838A (en) 1990-09-25
ES2058394T3 (en) 1994-11-01
DE3820650A1 (en) 1989-12-21
KR900000509A (en) 1990-01-30
NO176928B (en) 1995-03-13

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