EP0157190A1 - Etching process for aluminium - Google Patents

Etching process for aluminium Download PDF

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Publication number
EP0157190A1
EP0157190A1 EP85102400A EP85102400A EP0157190A1 EP 0157190 A1 EP0157190 A1 EP 0157190A1 EP 85102400 A EP85102400 A EP 85102400A EP 85102400 A EP85102400 A EP 85102400A EP 0157190 A1 EP0157190 A1 EP 0157190A1
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EP
European Patent Office
Prior art keywords
bath
pickling
aluminum
pickling bath
aluminum hydroxide
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EP85102400A
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German (de)
French (fr)
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EP0157190B1 (en
Inventor
Prof. Dr. E. Plattner
Ch. Dr. Comninellis
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Cessione metallgesellschaft AG
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Individual
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Priority claimed from CH1325/84A external-priority patent/CH660201A5/en
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Priority to AT85102400T priority Critical patent/ATE54679T1/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/10—Etching compositions
    • C23F1/14—Aqueous compositions
    • C23F1/32—Alkaline compositions
    • C23F1/36—Alkaline compositions for etching aluminium or alloys thereof
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/46—Regeneration of etching compositions
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
    • C23G1/22—Light metals
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/36—Regeneration of waste pickling liquors

Definitions

  • the invention relates to a pickling process for aluminum in an alkali bath.
  • Dissolving 27 g of aluminum (1 mol) consumes 40 g of sodium hydroxide solution (1 mol) and 18 g of water (1 mol) to form 82 g of dissolved sodium aluminate (1 mol) and 3 g of hydrogen (1.5 mol).
  • the bath concentration of sodium aluminate increases, the sodium hydroxide solution and the corresponding pickling power decrease.
  • the bath activity can be maintained by periodically adding additional sodium hydroxide solution.
  • a complexing agent is added to avoid the formation of solid adherent crusts from aluminum hydroxide.
  • the periodic removal of the worn pickling baths can be avoided by letting the concentration of dissolved aluminum rise to about 110 g / l. At this concentration, the bath liquid carried along with the treated pieces contains as much dissolved aluminum as was produced by pickling the corresponding pieces in the bath. A steady state is reached; the sodium hydroxide and complexing agent consumption must be supplemented by adding appropriate fresh chemicals; the total amount of dissolved aluminum gets into the wastewater with the rinse water and must be removed from a dilute solution.
  • the practically constant pickling bath composition ensures a constant quality of the treated pieces, but the high salt concentration often leads to the formation of stains on the pickled pieces during their transport from the pickling to the rinsing bath (see JH Dailey, Plating and surfaces finishing, July 1982 p 44)
  • Another way to solve the problem of worn pickling baths is to transfer part of the pickling bath into a separate container and to cause the precipitation of the aluminum hydroxide from the sodium hydroxide solution by changing the temperature and adding considerable amounts of aluminum hydroxide as inoculants according to the equation :
  • the object of the present invention was therefore to provide a pickling process for aluminum which largely avoids the disadvantages outlined above and leads in a simple and economical manner to a pickled aluminum of as constant a quality as possible.
  • the invention relates to a pickling process for aluminum in an alkali lye bath, which is characterized in that the aluminum hydroxide formed is precipitated in the bath in situ with simultaneous regeneration of the used alkali.
  • Sodium or potassium hydroxide solution is preferably used as the alkali hydroxide solution. It is expedient to work with a dilute pickling bath, and the pickling bath used according to the invention preferably contains less than 10 g / l, particularly preferably 1 to 10 g / 1 and in particular 3 to 6 g / 1 sodium or potassium hydroxide solution; the concentration of dissolved aluminum is less than 20 g / l, preferably less than 15 g / l, in particular 2 to 20 g / l, preferably 2 to 15 g / l, particularly preferably 4 to 8 g / l. These low alkali concentrations enable the precipitation of an easily filterable aluminum hydroxide and an easy generation of lye directly in the pickling bath.
  • he low concentration of the pickling bath in dissolved material fen also helps to keep the chemical loss caused by entrainment at a low level. The loss is further reduced if the pickled pieces are drained properly and the rinsing water is recycled.
  • the temperature of the pickling bath is preferably between 50 and 75 ° C.
  • the concentration of dissolved substances remains essentially constant during the pickling of the aluminum, because the aluminum hydroxide continuously fails, and should preferably be in the concentration range given above as preferred. This enables a regular pickling rate of 3 to 7 g aluminum per m 2 and minute at a bath temperature of 50 to 75 ° C. The quality of the treated pieces is consistently good.
  • the aluminum hydroxide formed during pickling accumulates in the pickling bath without disturbing the pickling. But it is desirable to keep the solids content of the bath between 10 and 30 g / 1 by the solid z. B. is separated by decanting and / or filtering.
  • the solids separation can be carried out batchwise or continuously, and is expediently carried out in part of the pickling bath.
  • the filtration form (filtration residue) obtained by the process according to the invention is good;
  • the filtration cake is easy to wash and contains more than 50% solids, which makes it easier to evaluate the aluminum hydroxide.
  • the precipitation of aluminum hydroxide can be done by adding alkali salts, e.g. B. of sodium carbonate, preferably in an amount of 5 to 100 g / 1, in particular 20 to 60 g / 1.
  • alkali salts e.g. B. of sodium carbonate
  • the state of matter and thus the filterability of the precipitated aluminum hydroxide is also affected by the presence of complexing agents, e.g. B. influenced by sodium gluconate. It is therefore advisable to add such complexing agents, e.g. B. sodium gluconate in an amount such that its concentration in the bath is between 0.01 to 1.0 g / 1, in particular 0.1 to 0.5 g / 1.
  • the lifetime of the pickling bath according to the invention is practical - table indefinitely if the losses caused by entrainment be supplemented by adding the appropriate amounts of fresh chemicals. These losses and the corresponding chemical costs can be kept to a minimum if the filtrate and washing water from the aluminum hydroxide filtration and the rinsing water of the pickled pieces are returned in whole or in part to the pickling bath. This return of the washing and rinsing water also serves to supplement the water loss caused by the formation of the aluminum hydroxide and the evaporation.
  • the replacement and removal of the worn pickling baths is no longer necessary, which means that a considerable saving in pickling costs can be achieved.
  • the necessary for carrying out the pickling process according to the invention Z usatzinvestitionen are small and consist essentially of the cost of a filtration plant.
  • the bath is loaded with about 120 kg of dissolved aluminum.
  • the precipitation of the aluminum hydroxide begins and is continued in accordance with the treatment of further pieces of aluminum.
  • the solids content is allowed to rise to about 350 kg (corresponding to the treatment of a further 5000 m 2 of aluminum) and is kept between 250 and 500 kg by continuous or batchwise filtration of part of the bath.
  • the filter cake is washed with 2 to 4 times its weight of water. The solids content depends on the filter type, but is at least 50%.
  • the filtrate and wash water are returned to the pickling bath.
  • the losses that occur during operation are supplemented by periodic addition of water, 100 kg sodium carbonate, 50 kg caustic soda (or equivalent amounts of sodium hydroxide solution) and 2 kg sodium gluconate.
  • the above consumption relates to the pickling of approximately 5000 m 2 of aluminum, corresponding to the formation of 350 kg of aluminum hydroxide. These are maximum values that were measured in a system without returning the washing and rinsing water.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

1. Pickling process for aluminium in an alkali lye bath with simultaneous precipitation of aluminium hydroxide in situ and regeneration of the alkali lye consumed during pickling, wherein a pickling bath is used which contains less than 10 g/l caustic soda or caustic potash solution and also contains sodium gluconate as the complexing agent, and is free of sulphides, sulphates, phosphates and thiosulphates, and wherein the aluminium hydroxide occurring in the pickling bath is precipitated without alteration of the temperature of the pickling bath.

Description

Die Erfindung betrifft ein Beizverfahren für Aluminium in einem Alkalilaugebad.The invention relates to a pickling process for aluminum in an alkali bath.

Die meisten Oberflächenveredelungsverfahren für Aluminium, z. B. die Eloxierung, setzen ein chemisches Beizen des Metalls voraus. Zur Durchführung des Beizens werden die entfetteten Aluminiumstücke z. B. in ein Natrönlaugebad bei 50°C bis 70°C während 5 bis 15 Minuten getaucht. Dabei löst sich das Metall unter Bildung von Natriumaluminat und Wasserstoff auf nach der Gleichung:

Figure imgb0001
Most surface finishing processes for aluminum, e.g. B. the anodization, require chemical pickling of the metal. To carry out the pickling, the degreased aluminum pieces are z. B. immersed in a sodium hydroxide solution at 50 ° C to 70 ° C for 5 to 15 minutes. The metal dissolves with the formation of sodium aluminate and hydrogen according to the equation:
Figure imgb0001

Das Lösen von 27 g Aluminium (1 mol) verbraucht 40 g Natronlauge (1 mol) und 18 g Wasser (1 mol) unter Bildung von 82 g gelöstem Natriumaluminat (1 mol) und 3 g Wasserstoff (1,5 mol).Dissolving 27 g of aluminum (1 mol) consumes 40 g of sodium hydroxide solution (1 mol) and 18 g of water (1 mol) to form 82 g of dissolved sodium aluminate (1 mol) and 3 g of hydrogen (1.5 mol).

Die Badkonzentration an Natriumaluminat nimmt dabei zu, die Natronlauge und die entsprechende Beizkraft nehmen ab.The bath concentration of sodium aluminate increases, the sodium hydroxide solution and the corresponding pickling power decrease.

Die Badaktivität kann durch periodische Zugabe von zusätzlicher Natronlauge aufrechterhalten werden. Um die Bildung von festen anhaftenden Krusten von Aluminiumhydroxid zu vermeiden, wird ein Komplexbildner zugegeben.The bath activity can be maintained by periodically adding additional sodium hydroxide solution. A complexing agent is added to avoid the formation of solid adherent crusts from aluminum hydroxide.

Normalerweise ist ein mit 70 g/1 Aluminium beladenes Bad abgenützt und muß durch ein frisches Bad ersetzt werden. Dieser Ersatz ist kostspielig und stellt ein Abwasserproblem dar, dessen Lösung erhebliche Kosten verursachen kann. Die stets sich verändernde Badzusammensetzung und

  • -aktivität führen außerdem zu einer unregelmäßigen Qualität der gebeizten Aluminiumstücke.
A bath loaded with 70 g / 1 aluminum is normally worn out and must be replaced by a fresh bath. This replacement is costly and is a wastewater problem, the solution of which can be costly. The constantly changing bathroom composition and
  • -activity also leads to an irregular quality of the pickled aluminum pieces.

Die periodische Beseitigung der abgenützten Beizbäder kann vermieden werden, indem man die Konzentration an gelöstem Aluminium bis auf etwa 110 g/1 steigen läßt. Bei dieser Konzentration enthält die mit den behandelten Stücken mitgeschleppte Badflüssigkeit so viel gelöstes Aluminium wie durch Beizen der entsprechenden Stücke im Bad entstanden ist. Ein stationärer Zustand wird erreicht; der Natronlauge- und Komplexbildnerverbrauch muß durch Zugabe entsprechender frischer Chemikalien ergänzt werden; die Gesamtmenge an gelöstem Aluminium gelangt mit dem Spülwasser in das Abwasser und muß aus einer verdünnten Lösung entfernt werden. Die praktisch konstante Beizbad-Zusammensetzung sorgt zwar für eine konstante Qualität der behandelten Stücke, die hohe Salzkonzentration führt aber oft zu Fleckenbildung auf den gebeizten Stücken während ihres Transports vom Beiz- zum Spülbad (vgl. J.H. Dailey, Plating and surfaces finishing, July 1982 S 44)The periodic removal of the worn pickling baths can be avoided by letting the concentration of dissolved aluminum rise to about 110 g / l. At this concentration, the bath liquid carried along with the treated pieces contains as much dissolved aluminum as was produced by pickling the corresponding pieces in the bath. A steady state is reached; the sodium hydroxide and complexing agent consumption must be supplemented by adding appropriate fresh chemicals; the total amount of dissolved aluminum gets into the wastewater with the rinse water and must be removed from a dilute solution. The practically constant pickling bath composition ensures a constant quality of the treated pieces, but the high salt concentration often leads to the formation of stains on the pickled pieces during their transport from the pickling to the rinsing bath (see JH Dailey, Plating and surfaces finishing, July 1982 p 44)

Ein weiterer Weg, das Problem der abgenützten Beizbäder zu lösen, besteht darin, einen Teil des Beizbades in einen separaten Behälter zu überführen und dort durch Temperaturänderung und Zugabe von beträchtlichen Mengen an Aluminiumhydroxid als Impfkeime die Fällung des Aluminiumhydroxids aus der Natronlaugelösung zu bewirken nach der Gleichung:

Figure imgb0002
Another way to solve the problem of worn pickling baths is to transfer part of the pickling bath into a separate container and to cause the precipitation of the aluminum hydroxide from the sodium hydroxide solution by changing the temperature and adding considerable amounts of aluminum hydroxide as inoculants according to the equation :
Figure imgb0002

Dabei wird Natronlauge in gleicher Menge regeneriert wie sie beim Beizen des Aluminiums verbraucht wurde. Nach Filtration und Waschung des Aluminiumhydroxids wird die so erhaltene alkalische Lösung wieder in das Beizbad rezyklisiert. Der Nachteil dieses Verfahrens liegt darin, daß eine aus Fäll- und Dekantierbehältern sowie Filterapparaten bestehende aufwendige Anlage in der Nähe des Beizbades installiert werden muß (vgl. C.J. Brown, Plating and surfaces finishing, June 1982, S 102).Sodium hydroxide solution is regenerated in the same amount as was used when pickling the aluminum. After filtration and washing of the aluminum hydroxide, the so the alkaline solution obtained is recycled back into the pickling bath. The disadvantage of this method is that a complex system consisting of precipitation and decanting containers and filter apparatus must be installed in the vicinity of the pickling bath (cf. CJ Brown, Plating and surface finishing, June 1982, p. 102).

Aufgabe der vorliegenden Erfindung war deshalb die Bereitstellung eines Beizverfahrens für Aluminium, das die vorstehend aufgezeigten Nachteile weitestgehend vermeidet und auf einfache und wirtschaftliche Weise zu einem gebeizten Aluminium von möglichst gleichbleibender Qualität führt.The object of the present invention was therefore to provide a pickling process for aluminum which largely avoids the disadvantages outlined above and leads in a simple and economical manner to a pickled aluminum of as constant a quality as possible.

Diese Aufgabe wird mit der vorliegenden Erfindung gelöst.This object is achieved with the present invention.

Gegenstand der Erfindung ist ein Beizverfahren für Aluminium in einem Alkalilaugebad, das dadurch gekennzeichnet ist, daß man entstehendes Aluminiumhydroxid im Bad in situ unter gleichzeitiger Regenerierung des verbrauchten Alkalis ausfällt.The invention relates to a pickling process for aluminum in an alkali lye bath, which is characterized in that the aluminum hydroxide formed is precipitated in the bath in situ with simultaneous regeneration of the used alkali.

Als Alkalilauge wird vorzugsweise Natron- oder Kalilauge verwendet. Zweckmäßigerweise wird mit einem verdünnten Beizbad gearbeitet, und vorzugsweise enthält das erfindungsgemäß eingesetzte Beizbad weniger als 10 g/l, besonders bevorzugt 1 bis 10 g/1 und insbesondere 3 bis 6 g/1 Natron- oder Kalilauge; die Konzentration an gelöstem Aluminium liegt unter 20 g/l, bevorzugt unter 15 g/l, insbesondere bei 2 bis 20 g/l, vorzugsweise 2 bis 15 g/l, besonders bevorzugt bei 4 bis 8 g/l. Diese geringen Alkali-Konzentrationen ermöglichen die Ausfällung eines leicht iltrierbaren Aluminiumhydroxids und eine leichte Laugenegeneration direkt im Beizbad.Sodium or potassium hydroxide solution is preferably used as the alkali hydroxide solution. It is expedient to work with a dilute pickling bath, and the pickling bath used according to the invention preferably contains less than 10 g / l, particularly preferably 1 to 10 g / 1 and in particular 3 to 6 g / 1 sodium or potassium hydroxide solution; the concentration of dissolved aluminum is less than 20 g / l, preferably less than 15 g / l, in particular 2 to 20 g / l, preferably 2 to 15 g / l, particularly preferably 4 to 8 g / l. These low alkali concentrations enable the precipitation of an easily filterable aluminum hydroxide and an easy generation of lye directly in the pickling bath.

ie geringe Konzentration des Beizbades an gelösten Stoffen trägt außerdem dazu bei, den durch Mitschleppen verursachten Chemikalienverlust auf einem geringen Wert zu halten. Der Verlust nimmt noch weiter ab, wenn man die gebeizten Stücke richtig abtropfen läßt und das Spülwasser rezyklisiert.he low concentration of the pickling bath in dissolved material fen also helps to keep the chemical loss caused by entrainment at a low level. The loss is further reduced if the pickled pieces are drained properly and the rinsing water is recycled.

Die Temperatur des Beizbades liegt vorzugsweise zwischen 50 und 75°C.The temperature of the pickling bath is preferably between 50 and 75 ° C.

Die Konzentration an gelösten Stoffen bleibt während des Beizens des Aluminiums im wesentlichen konstant, weil das Aluminiumhydroxid laufend ausfällt, und soll vorzugsweise in dem oben als bevorzugt angegebenen Konzentrationsbereich liegen. Dies ermöglicht eine regelmäßige Beizgeschwindigkeit von 3 bis 7 g Aluminium pro m2 und Minute bei einer Badtemperatur von 50 bis 75°C. Die Qualität der behandelten Stücke ist gleichbleibend gut.The concentration of dissolved substances remains essentially constant during the pickling of the aluminum, because the aluminum hydroxide continuously fails, and should preferably be in the concentration range given above as preferred. This enables a regular pickling rate of 3 to 7 g aluminum per m 2 and minute at a bath temperature of 50 to 75 ° C. The quality of the treated pieces is consistently good.

Das während des Beizens gebildete Aluminiumhydroxid reichert sich im Beizbad an, ohne das Beizen zu stören. Es ist aber wünschenswert, den Feststoffgehalt des Bades zwischen 10 und 30 g/1 zu halten, indem der Feststoff z. B. durch Dekantieren und/oder Filtrieren abgetrennt wird. Die Feststoffabtrennung kann chargenweise oder kontinuierlich durchgeführt werden, und wird zweckmäßigerweise jeweils in einem Teil des Beizbades durchgeführt. Die nach dem erfindungsgemäßen Verfahren erhaltene Filtrierform (Filtrationsrückstand) ist gut; der Filtrationskuchen ist leicht zu waschen und enthält mehr als 50 % Feststoff, was die Auswertung des Aluminiumhydroxids erleichtert.The aluminum hydroxide formed during pickling accumulates in the pickling bath without disturbing the pickling. But it is desirable to keep the solids content of the bath between 10 and 30 g / 1 by the solid z. B. is separated by decanting and / or filtering. The solids separation can be carried out batchwise or continuously, and is expediently carried out in part of the pickling bath. The filtration form (filtration residue) obtained by the process according to the invention is good; The filtration cake is easy to wash and contains more than 50% solids, which makes it easier to evaluate the aluminum hydroxide.

Die Ausfällung von Aluminiumhydroxid kann durch Zugabe von Alkalisalzen, z. B. von Natriumcarbonat, vorzugsweise in einer Menge von 5 bis 100 g/1, insbesondere 20 bis 60 g/1, begünstigt werden. Der Aggregatzustand und damit die Filtrierbarkeit des gefällten Aluminiumhydroxids wird auch durch die Anwesenheit von Komplexbildnern, z. B. von Natriumgluconat, beeinflußt. Es ist deshalb zweckmäßig, solche Komplexbildner zuzugeben, z. B. Natriumgluconat in einer Menge, daß seine Konzentration im Bad zwischen 0,01 bis 1,0 g/1, insbesondere 0,1 bis 0,5 g/1 beträgt.The precipitation of aluminum hydroxide can be done by adding alkali salts, e.g. B. of sodium carbonate, preferably in an amount of 5 to 100 g / 1, in particular 20 to 60 g / 1. The state of matter and thus the filterability of the precipitated aluminum hydroxide is also affected by the presence of complexing agents, e.g. B. influenced by sodium gluconate. It is therefore advisable to add such complexing agents, e.g. B. sodium gluconate in an amount such that its concentration in the bath is between 0.01 to 1.0 g / 1, in particular 0.1 to 0.5 g / 1.

Die Lebensdauer des erfindungsgemäßen Beizbades ist prak- tisch unbegrenzt, wenn die durch Mitschleppen verursachten Verluste durch Zugabe der entsprechenden Mengen an frischen Chemikalien ergänzt werden. Diese Verluste und die entsprechenden Chemikalienkosten lassen sich auf einem Minimum halten, wenn man Filtrat und Waschwasser der Aluminiumhydroxid-Filtration sowie das Spülwasser der gebeizten Stücke in das Beizbad ganz oder teilweise zurückführt. Dieses Rückführen des Wasch- und Spülwassers dient ebenfalls zur Ergänzung des durch die Bildung des Aluminiumhydroxids und des durch Verdampfung entstandenen Wasserverlusts.The lifetime of the pickling bath according to the invention is practical - table indefinitely if the losses caused by entrainment be supplemented by adding the appropriate amounts of fresh chemicals. These losses and the corresponding chemical costs can be kept to a minimum if the filtrate and washing water from the aluminum hydroxide filtration and the rinsing water of the pickled pieces are returned in whole or in part to the pickling bath. This return of the washing and rinsing water also serves to supplement the water loss caused by the formation of the aluminum hydroxide and the evaporation.

Der Ersatz und die Beseitigung der abgenützten.Beizbäder ist nicht mehr erforderlich, wodurch eine beträchtliche Einsparung der Beizkosten erreicht werden kann. Die zur Durchführung des erfindungsgemäßen Beizverfahrens nötigen Zusatzinvestitionen sind gering und bestehen im wesentlichen aus den Kosten für eine Filtrationsanlage.The replacement and removal of the worn pickling baths is no longer necessary, which means that a considerable saving in pickling costs can be achieved. The necessary for carrying out the pickling process according to the invention Z usatzinvestitionen are small and consist essentially of the cost of a filtration plant.

Das nachfolgende Beispiel erläutert die Erfindung näher, ohne sie darauf zu beschränken.The following example explains the invention in more detail without restricting it.

Beispielexample Herstellung des BeizbadesManufacture of the pickling bath

In einem Behälter mit Heizröhren und Drucklufteinleitung (zum Rühren) werden 12 m3 Wasser (40 bis 60°C) vorgelegt, in dem 1000 kg Natriumcarbonat (techn.), 280 kg Äztnatron (oder die äquivalente Menge Natronlauge) und 6 kg Natriumgluconat gelöst werden. Es wird mit Wasser auf ein Volumen von 20 m3 aufgefüllt, durchgemischt und auf etwa 70°C aufgeheizt.In a container with heating tubes and compressed air inlet (for stirring) 12 m 3 of water (40 to 60 ° C.) are placed in which 1000 kg of sodium carbonate (technical), 280 kg of caustic soda (or the equivalent amount of sodium hydroxide solution) and 6 kg of sodium gluconate are dissolved. It is made up to a volume of 20 m 3 with water, mixed and heated to about 70 ° C.

Betriebsbedingungen:

  • Badtemperatur 70 bis 75°C
  • Periodisches Durchmischen mittels Druckluft
  • pH-Wert 11,7 ± 0,1 (75°C)
  • Dichte (Be) 6 + 1 (75°C)
  • Dauer des Beizens 1 bis 10 Minuten (je nach gewünschtem Angriff)
Operating conditions:
  • Bath temperature 70 to 75 ° C
  • Periodic mixing using compressed air
  • pH 11.7 ± 0.1 (75 ° C)
  • Density (Be) 6 + 1 (75 ° C)
  • Pickling time 1 to 10 minutes (depending on the desired attack)

Diese Bedingungen bewirken eine Lösegeschwindigkeit von 6,5 + 0,5 g Al/m2/min.These conditions result in a dissolving rate of 6.5 + 0.5 g Al / m 2 / min.

Filtration des AluminiumhydroxidsFiltration of the aluminum hydroxide

Nach einer gewissen Betriebszeit, entsprechend der Behandlung von z. B. 5000 m2 Aluminium, ist das Bad mit etwa 120 kg gelöstem Aluminium beladen. Die Fällung des Aluminiumhydroxids setzt ein und wird entsprechend der Behandlung weiterer Aluminiumstücke fortgesetzt. Man läßt den Feststoffgehalt bis auf etwa 350 kg steigen (entsprechend der Behandlung von weiteren 5000 m2 Aluminium) und hält ihn zwischen 250 und 500 kg durch kontinuierliche oder chargenweise Filtration eines Teils des Bades. Der Filterkuchen wird mit dem 2-bis 4-fachen seines Gewichts Wasser gewaschen. Der Feststoffgehalt hängt vom Filtertyp ab, beträgt aber mindestens 50 %. Filtrat und Waschwasser werden in das Beizbad zurückgeführt.After a certain operating time, corresponding to the treatment of e.g. B. 5000 m 2 of aluminum, the bath is loaded with about 120 kg of dissolved aluminum. The precipitation of the aluminum hydroxide begins and is continued in accordance with the treatment of further pieces of aluminum. The solids content is allowed to rise to about 350 kg (corresponding to the treatment of a further 5000 m 2 of aluminum) and is kept between 250 and 500 kg by continuous or batchwise filtration of part of the bath. The filter cake is washed with 2 to 4 times its weight of water. The solids content depends on the filter type, but is at least 50%. The filtrate and wash water are returned to the pickling bath.

Aufrechterhaltung der BadzusammensetzungMaintaining the bath composition

Die während des Betriebs aufgetretenen Verluste (chemischer Wasserverbrauch, Verdampfung, Mitschleppen der Beizflüssigkeit) werden durch periodische Zugabe von Wasser, 100 kg Natriumcarbonat, 50 kg Ätznatron (oder äquivalenter Mengen an Natronlauge) und 2 kg Natriumgluconat ergänzt.The losses that occur during operation (chemical water consumption, evaporation, entrainment of the pickling liquid) are supplemented by periodic addition of water, 100 kg sodium carbonate, 50 kg caustic soda (or equivalent amounts of sodium hydroxide solution) and 2 kg sodium gluconate.

Der obige Verbrauch bezieht sich auf das Beizen von etwa 5000 m2 Aluminium, entsprechend der Bildung von 350 kg Aluminiumhydroxid. Es handelt sich um maximale Werte, die in einer Anlage ohne Rückführung des Wasch- und Spülwassers gemessen wurden.The above consumption relates to the pickling of approximately 5000 m 2 of aluminum, corresponding to the formation of 350 kg of aluminum hydroxide. These are maximum values that were measured in a system without returning the washing and rinsing water.

Claims (15)

1. Beizverfahren für Aluminium in einem Alkalilaugebad unter gleichzeitiger Ausfällung von Aluminiumhydroxid und Regenerierung der beim Beizen verbrauchten Alkalilauge, dadurch gekennzeichnet , daß das Beizbad weniger als 10 g/1 Natron- und/oder Kalilauge enthält und das im Beizbad entstehende Aluminiumhydroxid in situ ohne Änderung der Temperatur ausgefällt wird.1. pickling process for aluminum in an alkali lye bath with simultaneous precipitation of aluminum hydroxide and regeneration of the alkali lye consumed during pickling, characterized in that the pickling bath contains less than 10 g / 1 sodium and / or potassium hydroxide solution and the aluminum hydroxide formed in the pickling bath in situ without change the temperature is precipitated. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet , daß das Beizbad 1 bis 10 g/1 insbesondere 3 bis 6 g/1 Natronlauge oder Kalilauge und weniger als 20 g/l, bevorzugt weniger als 15 g/1, insbesondere 2 bis 20 g/1, vorzugsweise 2 bis 15 g/l, besonders bevorzugt 4 bis 8 g/1 gelöstes Aluminium enthält.2. The method according to claim 1, characterized in that the pickling bath 1 to 10 g / 1 in particular 3 to 6 g / 1 sodium hydroxide solution or potassium hydroxide solution and less than 20 g / l, preferably less than 15 g / 1, in particular 2 to 20 g / 1, preferably 2 to 15 g / l, particularly preferably 4 to 8 g / 1 dissolved aluminum. 3. Verfahren nach Anspruch 1 oder 2,
dadurch gekennzeichnet, daß man dem Beizbad ein Alkalisalz zusetzt.3. The method according to claim 1 or 2,
characterized in that an alkali salt is added to the pickling bath. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet , daß man als Alkalisalz Natriumcarbonat zusetzt.4. The method according to claim 3, characterized in that sodium carbonate is added as the alkali salt. 5. Verfahren nach Anspruch 4, dadurch gekennzeichnet , daß man das Natriumcarbonat in einer Menge von 5 bis 100 g/l, insbesondere 20 bis 60 g/1 zusetzt.5. The method according to claim 4, characterized in that the sodium carbonate is added in an amount of 5 to 100 g / l, in particular 20 to 60 g / 1. 6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet , daß man dem Beizbad ein komplexbildendes Mittel zusetzt.6. The method according to any one of the preceding claims, characterized in that a complexing agent is added to the pickling bath. 7. Verfahren nach Anspruch 6, dadurch gekennzeichnet , daß man als komplexbildendes Mittel Natriumgluconat zusetzt.7. The method according to claim 6, characterized in that sodium gluconate is added as a complexing agent. 8. Verfahren nach Anspruch 7, dadurch gekennzeichnet , daß man das Natriumgluconat in einer Menge von 0,01 bis 1,0 g/1, insbesondere 0,1 bis 0,5 g/1 zusetzt.8. The method according to claim 7, characterized in that the sodium gluconate is added in an amount of 0.01 to 1.0 g / 1, in particular 0.1 to 0.5 g / 1. 9. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet , daß die Temperatur des Bades 50 bis 75°C beträgt.9. The method according to any one of the preceding claims, characterized in that the Temperature of the bath is 50 to 75 ° C. 10. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet , daß das ausgefällte Aluminiumhydroxid kontinuierlich oder chargenweise aus dem Beizbad entfernt wird.10. The method according to any one of the preceding claims, characterized in that the precipitated aluminum hydroxide is removed continuously or in batches from the pickling bath. 11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß man das Aluminiumhydroxid entfernt, wenn der Feststoffgehalt des Beizbads 10 bis 30 g/1 übersteigt.11. The method according to claim 10, characterized in that the aluminum hydroxide is removed when the solids content of the pickling bath exceeds 10 to 30 g / 1. 12. Verfahren nach Anspruch 10 oder 11, dadurch gekennzeichnet , daß man die Entfernung des Aluminiumhydroxids aus einem Teil des Bades vornimmt.12. The method according to claim 10 or 11, characterized in that one carries out the removal of the aluminum hydroxide from a part of the bath. 13. Verfahren nach einem der Ansprüche 10 bis 12, dadurch gekennzeichnet , daß man die Abtrennung durch Dekantieren und/oder Filtrieren vornimmt.13. The method according to any one of claims 10 to 12, characterized in that the separation is carried out by decanting and / or filtering. 14. Verfahren nach einem der vorhergehenden Ansprüche; dadurch gekennzeichnet , daß man das bei der Abtrennung des Aluminiumhydroxids anfallende Filtrat und Waschwasser sowie das Spülwasser der gebeizten Aluminiumstücke in das Beizbad ganz oder teilweise zurückführt.14. The method according to any one of the preceding claims; characterized in that all or part of the filtrate and wash water obtained in the removal of the aluminum hydroxide and the rinse water of the pickled aluminum pieces are returned to the pickling bath. 15. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet , daß die Chemikalienverluste des Beizbades durch Zugabe der entsprechenden Mengen an frischen Chemikalien ergänzt werden.15. The method according to any one of the preceding claims, characterized in that the chemical losses of the pickling bath are supplemented by adding the appropriate amounts of fresh chemicals.
EP19850102400 1984-03-16 1985-03-04 Etching process for aluminium Expired - Lifetime EP0157190B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85102400T ATE54679T1 (en) 1984-03-16 1985-03-04 PICKLING PROCESS FOR ALUMINUM.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CH1325/84 1984-03-16
CH1325/84A CH660201A5 (en) 1984-03-16 1984-03-16 PROCESS FOR STRIPPING ALUMINUM IN AN ALKALINE LAUNDRY BATH.
DE3426114 1984-07-16
DE19843426114 DE3426114A1 (en) 1984-03-16 1984-07-16 Pickling process for aluminium

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Cited By (4)

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DE4008379A1 (en) * 1990-03-15 1991-09-19 Gartner & Co J METHOD AND SYSTEM FOR REGENERATING ALUMINUM ALUMINUM SOLUTIONS WITH ALKALINE
US5512129A (en) * 1990-03-15 1996-04-30 Josef Gartner & Co. Method for regenerating alkaline solutions for pickling aluminum
DE102013108375A1 (en) * 2013-01-31 2014-07-31 Thomas König Process for the preparation of a pickling and / or anodizing bath and anodizing arrangement
CN112921316A (en) * 2021-01-20 2021-06-08 福建省闽发铝业股份有限公司 Green environment-friendly aluminum profile spraying pretreatment process

Families Citing this family (3)

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ITMO20060401A1 (en) * 2006-12-07 2008-06-08 Italtecno S R L PLANT FOR THE RECOVERY OF CAUSTIC SODA FROM CAUSTIC SOLUTIONS AND ITS PROCEDURE.
EP2352859B1 (en) 2008-11-03 2018-06-27 Thomas König Pickling method and pickling plant
DE102008063729A1 (en) * 2008-11-03 2010-05-06 König, Thomas Process for pickling workpiece made of aluminum or aluminum alloy that is subjected to a sting bath with an alkaline pickling solution, comprises continuous or sectional drawing-off a partial quantity of the pickling solution from the bath

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DE1073272B (en) * 1960-01-14 Amchem Products Ine Ambler Pa (V St A) andsdale Mounted Route Pa (V St A) I solution and means for etching aluminum
US2653861A (en) * 1953-03-09 1953-09-29 Enthone Etching aluminum using hexahydroxyheptanoic acid as a modifier
US2884728A (en) * 1954-08-16 1959-05-05 Turco Products Inc Apparatus and method for removing metal from the surface of a metal object
FR1582144A (en) * 1968-06-24 1969-09-26
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DE4008379A1 (en) * 1990-03-15 1991-09-19 Gartner & Co J METHOD AND SYSTEM FOR REGENERATING ALUMINUM ALUMINUM SOLUTIONS WITH ALKALINE
US5512129A (en) * 1990-03-15 1996-04-30 Josef Gartner & Co. Method for regenerating alkaline solutions for pickling aluminum
DE102013108375A1 (en) * 2013-01-31 2014-07-31 Thomas König Process for the preparation of a pickling and / or anodizing bath and anodizing arrangement
CN112921316A (en) * 2021-01-20 2021-06-08 福建省闽发铝业股份有限公司 Green environment-friendly aluminum profile spraying pretreatment process

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