EP1097255A1 - Process for the preliminary treatment of a metallic workpiece before coating - Google Patents

Process for the preliminary treatment of a metallic workpiece before coating

Info

Publication number
EP1097255A1
EP1097255A1 EP99931072A EP99931072A EP1097255A1 EP 1097255 A1 EP1097255 A1 EP 1097255A1 EP 99931072 A EP99931072 A EP 99931072A EP 99931072 A EP99931072 A EP 99931072A EP 1097255 A1 EP1097255 A1 EP 1097255A1
Authority
EP
European Patent Office
Prior art keywords
workpiece
solution
polyaspartic acid
acid
painted
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.)
Granted
Application number
EP99931072A
Other languages
German (de)
French (fr)
Other versions
EP1097255B1 (en
Inventor
Johannes Lindemann
Karl Manderscheid
Rainer Kluth
Dirk Bohnes
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.)
Aware Chemicals LLC
Original Assignee
Aware Chemicals LLC
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Filing date
Publication date
Application filed by Aware Chemicals LLC filed Critical Aware Chemicals LLC
Publication of EP1097255A1 publication Critical patent/EP1097255A1/en
Application granted granted Critical
Publication of EP1097255B1 publication Critical patent/EP1097255B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
    • C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
    • C23F11/173—Macromolecular compounds
    • 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
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/50—Treatment of iron or alloys based thereon
    • 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
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/53—Treatment of zinc or alloys based thereon
    • 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
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/48—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates
    • C23C22/56—Treatment of aluminium or alloys based thereon
    • 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
    • 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
    • C23G1/24—Cleaning or pickling metallic material with solutions or molten salts with neutral solutions

Definitions

  • the invention relates to a method for pretreating a metallic workpiece for painting, the surface to be painted is cleaned with the aid of a solution containing degreasing agent and coated with a corrosion-inhibiting layer.
  • the surfaces of metallic workpieces to be painted must be cleaned and degreased before painting in order to create the conditions necessary for permanent painting to ensure good paint adhesion to the workpiece surface.
  • the surfaces of the workpiece to be painted are treated with a corresponding degreasing agent solution, which is either sprayed onto the surfaces to be painted or which serves as an immersion bath for the workpiece.
  • the workpieces are phosphated after rinsing to improve the corrosion resistance.
  • the workpiece surface is oxidatively attacked by the phosphating, which results in a slight removal of a surface cover layer.
  • the associated roughening of the surface improves the adhesion of the varnish applied later.
  • the workpiece surface is passivated in a further treatment step, so that there is an overall complex pretreatment of the workpiece.
  • the invention is therefore based on the object of designing a method for pretreating a metallic workpiece for painting of the type described at the outset in such a way that the process expenditure can be reduced considerably without impairing paint adhesion or endangering corrosion protection.
  • the invention relates to a method for pretreating a metallic workpiece for painting, the surface to be painted is cleaned with a degreasing agent-containing solution and coated with a corrosion-inhibiting layer, characterized in that the surface of the workpiece to be painted is coated with a corrosion-inhibiting layer Solution of polyaspartic acid is treated.
  • the solution containing a degreasing agent is preferably an aqueous solution of a so-called neutral cleaner or an alkaline cleaner.
  • Neutral cleaners generally have a pH in the range between about 7 and about 9 and contain nonionic surfactants as degreasing agents.
  • Alkaline cleaners are adjusted to pH values above 8.5 by adding alkalis or alkaline builders. They preferably contain anionic surfactants as degreasing agents.
  • a solution of polyaspartic acid or an aspartic acid-containing copolymer is mentioned here and below, it is meant that the solution contains the free acid and / or acid anions. As is known, it is a question of the pH of the solution, which ratio of free acid to acid anions is obtained.
  • the aspartic acid units in polyaspartic acid can be connected to one another by so-called ⁇ or so-called ⁇ -linkage.
  • ⁇ or so-called ⁇ -linkage As a rule, both types of linkage are present side by side within a polymer strand.
  • the ratio of ⁇ to ⁇ linkages is immaterial.
  • An aspartic acid-containing copolymer is a copolymer which, in addition to aspartic acid units, contains further monomeric assemblies. These can be other amino acids, but also polymerizable other carboxylic acids. It is preferred to use copolymers which consist of at least 50 mol%, preferably at least 80 mol%, of aspartic acid.
  • polyaspartic acid means both polyaspartic acid and a copolymer containing aspartic acid.
  • the workpiece surface can be covered with a thin organic film made of an organic polymer, the branched structure of which not only ensures a good connection to the substrate, but also good adhesion to the paint.
  • a polyaspartic acid for the pretreatment of a metallic workpiece to be painted which can be treated with the polyaspartic acid solution in a conventional manner in a dipping or spraying process, thus has the advantage that, compared to phosphating, a treatment step corresponding to the passivation does not apply, so that the risk of corrosion due to insufficient passivation can be excluded.
  • the metal surface covered with a layer of polyaspartic acid can be painted immediately.
  • This can be, for example, phosphating, treatment with a solution of chromium compounds, a solution of complex fluorides of boron, silicon, titanium and / or zirconium and / or a solution or dispersion of further organic polymers.
  • the workpiece can be cleaned again before this post-treatment.
  • the surface of the workpiece to be painted is treated with a solution of polyaspartic acid or a polymer containing aspartic acid and a degreasing agent for simultaneous degreasing and coating.
  • a solution of polyaspartic acid or a polymer containing aspartic acid and a degreasing agent for simultaneous degreasing and coating In this case, both degreasing and appropriate corrosion protection can be provided in a single treatment step.
  • the solution preferably contains a degreasing agent based on iminodisuccinic acid sodium salt.
  • the polyaspartic acid acts as a dispersing agent for the fat particles detached from the workpiece surface by the iminodisuccinic acid sodium salt, so that the detached fat particles are kept in dispersion by this dispersant and prevented from settling again on the workpiece surface.
  • the polyaspartic acid not only brings about a dispersing action for the fat particles, but also requires a corrosion-inhibiting surface layer, which is particularly advantageous with regard to the imparting of adhesion, which is advantageous for a creates permanent paintwork, especially since the iminodisuccinic acid sodium salt ensures a corresponding roughening of the workpiece surface.
  • the weight ratio of polyaspartic acid to sodium iminodisuccinic acid salt should be between 10: 1 and 1:10, a minimum concentration of polyaspartic acid of 2% in the solution having to be set in order to achieve the desired effects.
  • Corresponding additives can of course be added to the iminodisuccinic acid sodium salt, e.g. B. wetting agents or the like.
  • the detached fats and impurities can be separated off and the solution of the iminodisuccinic acid sodium salt and the polyaspartic acid can be returned to the workpiece treatment.
  • the solution of the organic degreasing agent and the polyaspartic acid penetrate the membrane filter as permeate, while the fats and impurities can be separated and disposed of as retentate.
  • the metal ions released from the workpiece surface by the iminodisuccinic acid sodium salt can then be separated from the permeate in order to avoid concentration of these metal ions.
  • the corrosion protection achieved in degreasing with iminodisuccinic acid sodium salt can be increased if necessary by subjecting the surface of the workpiece to be painted after degreasing to a further treatment in a 10 to 40 percent solution of the polyaspartic acid in order to coat it with the polyaspartic acid to improve conditional organic polymer.
  • the solution obtained from this aftertreatment can also be subjected to membrane filtration in order to be able to use the polyaspartic acid again for the workpiece treatment after separation of undesired loads.
  • the system for pretreating a metallic workpiece in particular made of sheet metal, has a plunge pool 1 for workpiece treatment, which is filled with an aqueous solution of a degreasing agent based on sodium iminodisuccinate and a polyaspartic acid.
  • the workpieces to be treated are immersed in this basin 1 in order to clean and degrease them on the one hand and to coat them with a corrosion-inhibiting, organic polymer layer on the other hand.
  • the fats and impurities dissolved by the use of sodium iminodisuccinic acid are kept in dispersion in the bath by the polyaspartic acid, because the polyaspartic acid acts as a dispersing agent.
  • a membrane filter device 2 is connected to the immersion basin 1, via which the fat particles in particular can be separated from the solution.
  • the retentate is removed from the membrane filter device 2 via a discharge line 3, while the permeate, which contains the organic degreasing agent and the polyaspartic acid, is returned to the immersion tank 1 in a circuit via a return line 4.
  • the ongoing bath losses are replaced via a feed line 5, through which fresh solution of the degreasing agent and the polyaspartic acid can be replenished.
  • Membrane filter device 2 is connected.
  • the metals bound in the ion exchanger 6 can be disposed of via the line 7.
  • the invention is not limited to the illustrated embodiment.
  • a conventional spray treatment can be used, the only thing that is decisive is that a polyaspartic acid is used for corrosion protection and to improve the adhesion of the paint, advantageously in combination with a degreasing agent based on sodium iminodisuccinate.
  • the treatment of the metal surface with polyaspartic acid or a copolymer containing aspartic acid is used as a measure for temporary corrosion protection.
  • processing processes such as forming or joining (welding, flanging) can be carried out before the final corrosion protection treatment. Forming processes are facilitated by the polymer layer on the metal surface. After such processes, the metal surface is usually dirty, so that it must be cleaned again before the final anti-corrosion treatment.
  • the previous coating with polyaspartic acid or a polymer containing polyaspartic acid has the advantage that the impurities can be removed more easily in such a subsequent cleaning step.
  • the surface to be painted is then treated with another solution before painting, which creates a conversion layer on the surface.
  • this can be a layer-forming phosphating, as is particularly common in the automotive industry and in the household appliance industry.
  • phosphating chromating, treatment with a solution of complex fluorides, in particular of the elements boron, silicon, titanium and / or zirconium, and / or a solution of other organic polymers.
  • These other organic polymers can be, for example, polymers or copolymers of acrylic acid or methacrylic acid or polyvinylphenols.
  • workpieces made of metals are workpieces made of steel, galvanized or alloy-galvanized steel or of aluminum or its alloys.
  • workpieces made of magnesium or magnesium alloys are also suitable.

Abstract

A process for the preliminary treatment of a metallic workpiece before coating is disclosed. The surface to be coated is cleaned with a solution containing a degreasing agent and coated with a corrosion-inhibiting layer. In order to obtain particularly advantageous conditions, the invention proposes treating the surface of the workpiece to be coated with a solution of polyaspartic acid for applying a corrosion-inhibiting layer.

Description

"Verfahren zur Vorbehandlung eines metallischen Werkstücks für eine Lackierung""Process for pretreating a metallic workpiece for painting"
Die Erfindung bezieht sich auf ein Verfahren zur Vorbehandlung eines metallischen Werkstücks für eine Lackierung, dessen zu lackierende Oberfläche mit Hilfe einer Entfettungsmittel enthaltenden Lösung gereinigt und mit einer korrosionshemmenden Schicht überzogen wird.The invention relates to a method for pretreating a metallic workpiece for painting, the surface to be painted is cleaned with the aid of a solution containing degreasing agent and coated with a corrosion-inhibiting layer.
Die zu lackierenden Oberflächen metallischer Werkstücke sind vor einer Lackierung zu reinigen und zu entfetten, um die für eine dauerhafte Lackierung notwendigen Voraussetzungen für eine gute Lackhaftung auf der Werkstückoberfläche zu schaffen. Zu diesem Zweck werden die zu lackierenden Oberflächen des Werkstücks mit einer entsprechende Entfettungsmittel enthaltenden Lösung behandelt, die entweder auf die zu lackierenden Oberflächen aufgespritzt wird oder die als Tauchbad für das Werkstück dient. Im Anschluß an diese Entfettung werden die Werkstücke nach einer Spülung zur Verbesserung der Korrosionsbeständigkeit phosphatiert. Durch die Phosphatierung wird die Werkstückoberfläche oxidativ angegriffen, wobei es zu einem geringfügigen Abtrag einer Oberflächendeckschicht kommt. Die damit verbundene Aufrauhung der Oberfläche verbessert die Haftung des später aufgebrachten Lackes. Um die oxidative Oberflächenreaktion zu beenden, wird die Werkstückoberfiäche in einem weiteren Behandlungsschritt passiviert, so daß sich eine insgesamt aufwendige Vorbehandlung des Werkstücks ergibt.The surfaces of metallic workpieces to be painted must be cleaned and degreased before painting in order to create the conditions necessary for permanent painting to ensure good paint adhesion to the workpiece surface. For this purpose, the surfaces of the workpiece to be painted are treated with a corresponding degreasing agent solution, which is either sprayed onto the surfaces to be painted or which serves as an immersion bath for the workpiece. Following this degreasing, the workpieces are phosphated after rinsing to improve the corrosion resistance. The workpiece surface is oxidatively attacked by the phosphating, which results in a slight removal of a surface cover layer. The associated roughening of the surface improves the adhesion of the varnish applied later. In order to end the oxidative surface reaction, the workpiece surface is passivated in a further treatment step, so that there is an overall complex pretreatment of the workpiece.
Um Weicheisenoberflächen vor einem Korrosionsangriff durch Salzwasser zu schützen, ist es bekannt (WO 96/27696), dem Salzwasser vergleichsweise geringe Mengen an Polyasparaginsäure zuzumischen. Die korrosionshemmende Wirkung von Polyasparaginsäure und Polyasparaginpolymeren aus Polyasparaginsäure sowie deren Salz oder Amid wird auch bei Kühl- und Schmiermitteln für die spanabhebende Bearbeitung von Werkstücken ausgenützt (WO 95/10583, WO 95/24456). Solche korrosionshemmenden Zusätze zu Flüssigkeiten, die metallische Oberflächen korrosiv angreifen, können jedoch keine Lehre dafür geben, wie Oberflächen metallischer Werkstücke für eine dauerhafte Lackierung behandelt werden müssen.In order to protect soft iron surfaces from corrosion by salt water, it is known (WO 96/27696) to mix comparatively small amounts of polyaspartic acid into the salt water. The corrosion-inhibiting effect of polyaspartic acid and polyaspartic polymers made of polyaspartic acid and their salt or amide is also used for coolants and lubricants for the Machining of workpieces used (WO 95/10583, WO 95/24456). However, such corrosion-inhibiting additives to liquids that corrosively attack metallic surfaces cannot give any teaching as to how surfaces of metallic workpieces have to be treated for permanent painting.
Schließlich ist es bekannt (WO 95/24456), zur Reinigung einer metallischen Oberfläche eine wäßrige Lösung einer Polyaminosäure vorzusehen, deren Aminosäure-Gruppe unter anderem Asparaginsäure enthalten kann. Bei Einhaltung eines vergleichsweise niedrigen pH-Wertes von höchstens 7 können zwar die mit einer solchen Lösung behandelten metallischen Oberfläche von Korrosionen gereinigt werden, doch wird dadurch kein für eine spätere Lackierung erforderlicher Korrosionsschutz erreicht.Finally, it is known (WO 95/24456) to provide an aqueous solution of a polyamino acid for cleaning a metallic surface, the amino acid group of which may contain, among other things, aspartic acid. If a comparatively low pH value of at most 7 is observed, the metallic surface treated with such a solution can be cleaned of corrosion, but this does not provide any corrosion protection required for subsequent painting.
Der Erfindung liegt somit die Aufgabe zugrunde, ein Verfahren zur Vorbehandlung eines metallischen Werkstücks für eine Lackierung der eingangs geschilderten Art so auszugestalten, daß der Verfahrensaufwand erheblich herabgesetzt werden kann, ohne die Lackhaftung zu beeinträchtigen oder den Korrosionsschutz zu gefährden.The invention is therefore based on the object of designing a method for pretreating a metallic workpiece for painting of the type described at the outset in such a way that the process expenditure can be reduced considerably without impairing paint adhesion or endangering corrosion protection.
Die Erfindung betrifft ein Verfahren zur Vorbehandlung eines metallischen Werkstücks für eine Lackierung, dessen zu lackierende Oberfläche mit Hilfe einer Entfettungsmittel enthaltenden Lösung gereinigt und mit einer korrosionshemmenden Schicht überzogen wird, dadurch gekennzeichnet, daß die zu lackierende Oberfläche des Werkstücks zum Auftragen einer korrosionshemmenden Schicht mit einer Lösung von Polyasparaginsäure behandelt wird.The invention relates to a method for pretreating a metallic workpiece for painting, the surface to be painted is cleaned with a degreasing agent-containing solution and coated with a corrosion-inhibiting layer, characterized in that the surface of the workpiece to be painted is coated with a corrosion-inhibiting layer Solution of polyaspartic acid is treated.
Bei der ein Entfettungsmittel enthaltenden Lösung handelt es sich vorzugsweise um eine wäßrige Lösung eines sogenannten Neutralreinigers oder eines alkalischen Reinigers. Neutralreiniger weisen in der Regel einen pH-Wert im Bereich zwischen etwa 7 und etwa 9 auf und enthalten als Entfettungsmittel nichtionische Tenside. Alkalische Reiniger sind durch Zugabe von Alkalien oder alkalisch wirkenden Buildersubstanzen auf pH-Werte oberhalb von 8,5 eingestellt. Als Entfettungsmittel enthalten Sie vorzugsweise anionische Tenside. Wenn hier und im folgenden von einer Lösung von Polyasparaginsäure oder eines Asparaginsäure-enthaltenden Copolymers die Rede ist, so ist damit gemeint, daß die Lösung die freie Säure und/oder Säureanionen enthält. Bekanntermaßen ist es eine Frage des pH-Wertes der Lösung, welches Verhältnis von freier Säure zu Säureanionen sich einstellt. Die Asparaginsäure-Einheiten in Polyasparaginsäure können durch sogenannte α- oder sogenannte ß-Verknüpfung miteinander verbunden sein. In der Regel liegen innerhalb eines Polymerstrangs beide Verknüpfungstypen nebeneinander vor. Für die vorliegende Erfindung ist das Verhältnis von α- zu ß-Verknüpfungen unwesentlich. Ein Asparaginsäure- enthaltendes Copolymer ist ein Copolymer, das neben Asparaginsäure-Einheiten weitere monomere Baugruppen enthält. Diese können andere Aminosäuren, jedoch auch polymerisierbare andere Carbonsäuren darstellen. Vorzugsweise setzt man Copolymere ein, die zu mindestens 50 Mol.-%, vorzugsweise zu mindestens 80 Mol- % aus Asparaginsäure bestehen.The solution containing a degreasing agent is preferably an aqueous solution of a so-called neutral cleaner or an alkaline cleaner. Neutral cleaners generally have a pH in the range between about 7 and about 9 and contain nonionic surfactants as degreasing agents. Alkaline cleaners are adjusted to pH values above 8.5 by adding alkalis or alkaline builders. They preferably contain anionic surfactants as degreasing agents. When a solution of polyaspartic acid or an aspartic acid-containing copolymer is mentioned here and below, it is meant that the solution contains the free acid and / or acid anions. As is known, it is a question of the pH of the solution, which ratio of free acid to acid anions is obtained. The aspartic acid units in polyaspartic acid can be connected to one another by so-called α or so-called β-linkage. As a rule, both types of linkage are present side by side within a polymer strand. For the present invention, the ratio of α to β linkages is immaterial. An aspartic acid-containing copolymer is a copolymer which, in addition to aspartic acid units, contains further monomeric assemblies. These can be other amino acids, but also polymerizable other carboxylic acids. It is preferred to use copolymers which consist of at least 50 mol%, preferably at least 80 mol%, of aspartic acid.
Wenn in der folgenden Beschreibung kurz von Polyasparaginsäure die Rede ist, so ist damit sowohl Polyasparaginsäure als auch ein Asparaginsäure-enthaltendes Copolymer gemeint.When the following description refers briefly to polyaspartic acid, it means both polyaspartic acid and a copolymer containing aspartic acid.
Durch die Behandlung der zu lackierenden Oberfläche des Werkstücks mit einer Lösung von Polyasparaginsäure kann die Werkstückoberfläche mit einem dünnen organischen Film aus einem organischen Polymer belegt werden, dessen verzweigte Struktur nicht nur eine gute Verbindung zum Untergrund, sondern auch eine gute Haftvermittlung zum Lack sicherstellt. Der Einsatz einer Polyasparaginsäure für die Vorbehandlung eines zu lackierenden, metallischen Werkstücks, das in üblicher Weise in einem Tauch- bzw. Spritzverfahren mit der Polyasparaginsäurelösung behandelt werden kann, bringt somit den Vorteil mit sich, daß im Vergleich zu einer Phosphatierung ein der Passivierung entsprechender Behandlungsschritt entfällt, so daß die durch eine unzureichende Passivierung gegebene Korrosionsgefährdung ausgeschlossen werden kann. Die mit einer Schicht von Polyasparaginsäure überzogene Metalloberfläche kann unmittelbar lackiert werden. Damit ist gemeint, daß zwischen der Behandlung mit der Asparaginsäure-enthaltenden Lösung und der Lackierung allenfalls Spülschritte, jedoch keine weiteren Vorgänge wie beispielsweise Transport der Werkstücke zu einer weiteren Verarbeitungsstätte, Umformungs- oder Fügeprozesse stattfinden. Die beschriebene Behandlung mit der Polyasparaginsäure-enthaltenden Lösung kann jedoch auch als temporäre Korrosionsschutzmaßnahme eingesetzt werden. Dies heißt, daß sie der Metalloberfläche auch ohne unmittelbare Lackierung einen hinreichenden Korrossionsschutz verleiht, um die metallischen Werkstücke vor der Lackierung zu transportieren, zu lagern, umzuformen oder zu fügen. Finden solche Prozesse statt, ist unmittelbar vor der endgültigen Lackierung eine Nachbehandlung mit einer weiteren Lösung zur Verstärkung oder Verlängerung der im Teilschritt b) erzielten Korrosionsschutzwirkung vorzuziehen. Hierbei kann es sich beispielsweise handeln um eine Phosphatierung, eine Behandlung mit einer Lösung von Chromverbindungen, einer Lösung von komplexen Fluoriden von Bor, Silizium, Titan und/oder Zirkon und/oder einer Lösung oder Dispersion weiterer organischer Polymere. Dabei kann das Werkstück vor dieser Nachbehandlung nochmals gereinigt werden.By treating the surface of the workpiece to be painted with a solution of polyaspartic acid, the workpiece surface can be covered with a thin organic film made of an organic polymer, the branched structure of which not only ensures a good connection to the substrate, but also good adhesion to the paint. The use of a polyaspartic acid for the pretreatment of a metallic workpiece to be painted, which can be treated with the polyaspartic acid solution in a conventional manner in a dipping or spraying process, thus has the advantage that, compared to phosphating, a treatment step corresponding to the passivation does not apply, so that the risk of corrosion due to insufficient passivation can be excluded. The metal surface covered with a layer of polyaspartic acid can be painted immediately. This means that between the treatment with the aspartic acid-containing solution and the lacquering, at most rinsing steps, but no further processes such as, for example, transporting the workpieces to a further processing site, forming or joining processes take place. However, the treatment described with the solution containing polyaspartic acid can also be used as a temporary corrosion protection measure. This means that it gives the metal surface sufficient protection against corrosion even without immediate painting in order to transport, store, reshape or join the metallic workpieces before painting. If such processes take place, an aftertreatment with a further solution to reinforce or extend the corrosion protection effect achieved in sub-step b) is preferable immediately before the final painting. This can be, for example, phosphating, treatment with a solution of chromium compounds, a solution of complex fluorides of boron, silicon, titanium and / or zirconium and / or a solution or dispersion of further organic polymers. The workpiece can be cleaned again before this post-treatment.
Besonders vorteilhafte Verhältnisse ergeben sich in diesem Zusammenhang, wenn in weiterer Ausbildung der Erfindung die zu lackierende Oberfläche des Werkstücks zum gleichzeitigen Entfetten und Beschichten mit einer Lösung von Polyasparaginsäure oder einem Asparaginsäure-enthaltenden Polymer und einem Entfettungsmittel behandelt wird. In diesem Fall kann nämlich in einem einzigen Behandlungsschritt sowohl für die Entfettung als auch für einen entsprechenden Korrosionsschutz gesorgt werden. Vorzugsweise enthält die Lösung ein Entfettungsmittel auf der Basis von Iminodibernsteinsäure-Natriumsalz. Die Polyasparaginsäure wirkt für die durch das Iminodibernsteinsäure-Natriumsalz von der Werkstückoberfläche abgelösten Fetteilchen als Dispergiermittel, so daß die abgelösten Fetteilchen durch diesen Dispergator in Dispersion gehalten und daran gehindert werden, sich erneut auf der Werkstückoberfläche abzusetzen. Die Polyasparaginsäure bringt aber nicht nur eine Dispergierwirkung für die Fetteilchen mit sich, sondern bedingt auch eine insbesondere hinsichtlich der Haftvermittlung besonders vorteilhafte, korrosions- hemmende Oberflächenschicht, was vorteilhafte Voraussetzungen für eine dauerhafte Lackierung schafft, zumal das Iminodibemsteinsäure-Natriumsalz für eine entsprechende Aufrauhung der Werkstückoberfläche sorgt.Particularly advantageous conditions result in this connection if, in a further embodiment of the invention, the surface of the workpiece to be painted is treated with a solution of polyaspartic acid or a polymer containing aspartic acid and a degreasing agent for simultaneous degreasing and coating. In this case, both degreasing and appropriate corrosion protection can be provided in a single treatment step. The solution preferably contains a degreasing agent based on iminodisuccinic acid sodium salt. The polyaspartic acid acts as a dispersing agent for the fat particles detached from the workpiece surface by the iminodisuccinic acid sodium salt, so that the detached fat particles are kept in dispersion by this dispersant and prevented from settling again on the workpiece surface. However, the polyaspartic acid not only brings about a dispersing action for the fat particles, but also requires a corrosion-inhibiting surface layer, which is particularly advantageous with regard to the imparting of adhesion, which is advantageous for a creates permanent paintwork, especially since the iminodisuccinic acid sodium salt ensures a corresponding roughening of the workpiece surface.
Das Gewichtsverhältnis von Polyasparaginsäure zu Iminodibemsteinsäure- Natriumsalz soll dabei zwischen 10 : 1 und 1 : 10 betragen, wobei eine Mindestkonzentration an Polyasparaginsäure von 2 % in der Lösung einzustellen ist, um die angestrebten Wirkungen zu erzielen. Dem Iminodibernsteinsäure-Natriumsalz können selbstverständlich entsprechende Zusätze beigemischt werden, z. B. Benetzungsmittel od. dgl.The weight ratio of polyaspartic acid to sodium iminodisuccinic acid salt should be between 10: 1 and 1:10, a minimum concentration of polyaspartic acid of 2% in the solution having to be set in order to achieve the desired effects. Corresponding additives can of course be added to the iminodisuccinic acid sodium salt, e.g. B. wetting agents or the like.
Wird die mit den von der Werkstückoberfläche abgelösten Fetten belastete Lösung des Iminodibernsteinsäure-Natriumsalzes und der Polyasparaginsäure einer Membranfiltration unterworfen, so können die abgelösten Fette und Verunreinigungen abgeschieden und die Lösung des Iminodibemsteinsäure-Natriumsalzes und der Polyasparaginsäure zur Werkstückbehandlung rückgeführt werden. Die Lösung des organischen Entfettungsmittels und der Polyasparaginsäure durchsetzen nämlich die Membranfilter als Permeat, während die Fette und Verunreinigungen als Retentat abgeschieden und entsorgt werden können. Die vom Iminodibernsteinsäure- Natriumsalz aus der Werkstückoberfläche gelösten Metallionen können dann aus dem Permeat abgeschieden werden, um eine Aufkonzentrierung dieser Metallionen zu vermeiden.If the solution of the iminodisuccinic acid sodium salt and the polyaspartic acid loaded with the fats detached from the workpiece surface is subjected to membrane filtration, the detached fats and impurities can be separated off and the solution of the iminodisuccinic acid sodium salt and the polyaspartic acid can be returned to the workpiece treatment. The solution of the organic degreasing agent and the polyaspartic acid penetrate the membrane filter as permeate, while the fats and impurities can be separated and disposed of as retentate. The metal ions released from the workpiece surface by the iminodisuccinic acid sodium salt can then be separated from the permeate in order to avoid concentration of these metal ions.
Der bei der Entfettung mit Iminodibernsteinsäure-Natriumsalz erreichte Korrosionsschutz kann bei Bedarf dadurch verstärkt werden, daß die zu lackierende Oberfläche des Werkstücks nach dem Entfetten einer weiteren Behandlung in einer 10 bis 40 prozentigen Lösung der Polyasparaginsäure unterworfen wird, um die Beschichtung mit dem durch die Polyasparaginsäure bedingten organischen Polymer zu verbessern. Selbstverständlich kann die aus dieser Nachbehandlung anfallende Lösung ebenfalls einer Membranfiltration unterworfen werden, um die Polyasparaginsäure nach einem Abscheiden von unerwünschten Belastungen wieder für die Werkstückbehandlung einsetzen zu können. Anhand der Zeichnung wird das erfindungsgemäße Verfahren näher erläutert, und zwar wird eine Anlage zur Durchführung des Verfahrens in einem schematischen Blockschaltbild gezeigt.The corrosion protection achieved in degreasing with iminodisuccinic acid sodium salt can be increased if necessary by subjecting the surface of the workpiece to be painted after degreasing to a further treatment in a 10 to 40 percent solution of the polyaspartic acid in order to coat it with the polyaspartic acid to improve conditional organic polymer. Of course, the solution obtained from this aftertreatment can also be subjected to membrane filtration in order to be able to use the polyaspartic acid again for the workpiece treatment after separation of undesired loads. The method according to the invention is explained in more detail with reference to the drawing, namely a system for carrying out the method is shown in a schematic block diagram.
Gemäß dem dargestellten Ausführungsbeispiel weist die Anlage zur Vorbehandlung eines metallischen Werkstückes, insbesondere aus Blech, ein Tauchbecken 1 für die Werkstückbehandlung auf, das mit einer wäßrigen Lösung eines Entfettungsmittels auf der Basis von Iminodibernsteinsäure-Natriumsalz und einer Polyasparaginsäure gefüllt ist. In dieses Becken 1 werden die zu behandelnden Werkstücke eingetaucht, um sie einerseits zu reinigen und zu entfetten und anderseits mit einer korrosionshemmenden, organischen Polymerschicht zu überziehen. Die durch den Einsatz von Iminodibernsteinsäure-Natriumsalz gelösten Fette und Verunreinigungen werden im Bad durch die Polyasparaginsäure in Dispersion gehalten, weil die Polyasparaginsäure als Dispergiermittel wirkt. Damit wird ein neuerliches Absetzen dieser Teilchen auf der Werkstückoberfläche verhindert, die nach der Entnahme des Werkstücks aus dem Tauchbad 1 und einer anschließenden Spülung lackiert werden kann, falls nicht in einem weiteren Behandlungsschritt die korrosionshemmende Schicht durch ein weiteres Bad in einer Polyasparaginsäure-Lösung verstärkt wird.According to the illustrated embodiment, the system for pretreating a metallic workpiece, in particular made of sheet metal, has a plunge pool 1 for workpiece treatment, which is filled with an aqueous solution of a degreasing agent based on sodium iminodisuccinate and a polyaspartic acid. The workpieces to be treated are immersed in this basin 1 in order to clean and degrease them on the one hand and to coat them with a corrosion-inhibiting, organic polymer layer on the other hand. The fats and impurities dissolved by the use of sodium iminodisuccinic acid are kept in dispersion in the bath by the polyaspartic acid, because the polyaspartic acid acts as a dispersing agent. This prevents a new deposit of these particles on the workpiece surface, which can be painted after the workpiece has been removed from the immersion bath 1 and then rinsed, unless the corrosion-inhibiting layer is strengthened by a further bath in a polyaspartic acid solution in a further treatment step .
Um die Wirkung des Tauchbades nicht durch die Zunahme der Konzentration der von der Werkstückoberfläche abgelösten Teilchen zu beeinträchtigen, ist an das Tauchbecken 1 eine Membranfiltereinrichtung 2 angeschlossen, über die insbesondere die Fetteilchen aus der Lösung abgeschieden werden können. Das Retentat wird aus der Membranfiltereinrichtung 2 über eine Ableitung 3 abgeführt, während das Permeat, das das organische Entfettungsmittel und die Polyasparaginsäure enthält über eine Rückleitung 4 im Kreislauf wieder dem Tauchbecken 1 zugeführt wird. Die laufenden Badverluste werden über eine Zuleitung 5 ersetzt, über die frische Lösung des Entfettungsmittels und der Polyasparaginsäure nachgefüllt werden können.In order not to impair the effect of the immersion bath by the increase in the concentration of the particles detached from the workpiece surface, a membrane filter device 2 is connected to the immersion basin 1, via which the fat particles in particular can be separated from the solution. The retentate is removed from the membrane filter device 2 via a discharge line 3, while the permeate, which contains the organic degreasing agent and the polyaspartic acid, is returned to the immersion tank 1 in a circuit via a return line 4. The ongoing bath losses are replaced via a feed line 5, through which fresh solution of the degreasing agent and the polyaspartic acid can be replenished.
Da der Einsatz von Iminodibemsteinsäure-Natriumsalz auch das Ablösen von Metallionen von der Werkstückoberfläche bewirkt, ist auch für ein entsprechendes Abscheiden dieser Metallionen zu sorgen. Dies ist in dem Blockschaltbild der Zeichnung durch einen lonentauscher 6 angedeutet, der an dieSince the use of iminodisuccinic acid sodium salt also causes metal ions to detach from the workpiece surface, it is also necessary to ensure that these metal ions are separated accordingly. This is in the block diagram of the Drawing indicated by an ion exchanger 6 to the
Membranfiltereinrichtung 2 angeschlossen ist. Die im lonentauscher 6 abgebundenen Metalle können über die Leitung 7 entsorgt werden.Membrane filter device 2 is connected. The metals bound in the ion exchanger 6 can be disposed of via the line 7.
Es braucht wohl nicht besonders hervorgehoben zu werden, daß die Erfindung nicht auf das dargestellte Ausführungsbeispiel beschränkt ist. Anstelle einer Tauchbehandlung kann beispielsweise eine übliche Spritzbehandlung treten, entscheidend ist ja lediglich, daß für den Korrosionsschutz und die Verbesserung der Haftfähigkeit des Lackes eine Polyasparaginsäure eingesetzt wird, und zwar vorteilhaft im Zusammenwirken mit einem Entfettungsmittel auf der Basis von Iminodibernsteinsäure-Natriumsalz.Needless to say, the invention is not limited to the illustrated embodiment. Instead of an immersion treatment, for example, a conventional spray treatment can be used, the only thing that is decisive is that a polyaspartic acid is used for corrosion protection and to improve the adhesion of the paint, advantageously in combination with a degreasing agent based on sodium iminodisuccinate.
In einer speziellen Ausführungsform der vorliegenden Erfindung wird die Behandlung der Metalloberfläche mit Polyasparaginsäure oder einem Asparaginsäure- enthaltendem Copolymer als Maßnahme für einen temporären Korrosionsschutz eingesetzt. Dies heißt, daß das Werkstück vor der endgültigen Korrosionsschutzbehandlung für einen längeren Zeitraum (Tage bis Wochen) gelagert und/oder transportiert wird. Weiterhin können vor der endgültigen Korrosionsschutzbehandlung Verarbeitungsprozesse wie beispielsweise Umformen oder Fügen (Schweißen, Bördeln) durchgeführt werden. Dabei werden Umformprozesse durch die Polymerschicht auf der Metalloberfläche erleichtert. Nach derartigen Prozessen ist die Metalloberfläche in der Regel verschmutzt, so daß sie vor der endgültigen Korrosionsschutzbehandlung nochmals gereinigt werden muß. Dabei hat die vorausgegangene Beschichtung mit Polyasparaginsäure oder einem Polyasparaginsäure- enthaltendem Polymer den Vorteil, daß in einem solchen nachfolgenden Reinigungsschritt die Verunreinigungen leichter entfernt werden können.In a special embodiment of the present invention, the treatment of the metal surface with polyaspartic acid or a copolymer containing aspartic acid is used as a measure for temporary corrosion protection. This means that the workpiece is stored and / or transported for a longer period (days to weeks) before the final corrosion protection treatment. Furthermore, processing processes such as forming or joining (welding, flanging) can be carried out before the final corrosion protection treatment. Forming processes are facilitated by the polymer layer on the metal surface. After such processes, the metal surface is usually dirty, so that it must be cleaned again before the final anti-corrosion treatment. The previous coating with polyaspartic acid or a polymer containing polyaspartic acid has the advantage that the impurities can be removed more easily in such a subsequent cleaning step.
Die zu lackierende Oberfläche wird dann vor dem Lackieren mit einer weiteren Lösung behandelt, die auf der Oberfläche eine Konversionsschicht erzeugt. Insbesondere kann es sich hierbei um eine schichtbildende Phosphatierung handeln, wie sie insbesondere im Automobilbau und in der Haushaltsgeräteindustrie gebräuchlich ist. Statt einer Phosphatierung können jedoch auch eine Chromatierung, eine Behandlung mit einer Lösung komplexer Fluoride, insbesondere der Elemente Bor, Silizium, Titan und/oder Zirkon, und/oder einer Lösung anderer organischer Polymere erfolgen. Bei diesen anderen organischen Polymeren kann es sich beispielsweise handeln um Polymere oder Copolymere von Acrylsäure oder Methacrylsäure oder um Polyvinylphenole.The surface to be painted is then treated with another solution before painting, which creates a conversion layer on the surface. In particular, this can be a layer-forming phosphating, as is particularly common in the automotive industry and in the household appliance industry. Instead of phosphating, chromating, treatment with a solution of complex fluorides, in particular of the elements boron, silicon, titanium and / or zirconium, and / or a solution of other organic polymers. These other organic polymers can be, for example, polymers or copolymers of acrylic acid or methacrylic acid or polyvinylphenols.
Wenn im vorstehenden allgemein von metallischen Werkstücken die Rede war, so sind hiermit insbesondere Werkstücke aus Metallen gemeint, wie sie in der Fahrzeug-, Möbel- oder Haushaltsgeräteindustrie gebräuchlich sind. Insbesondere handelt es sich um Werkstücke aus Stahl, verzinktem oder legierungsverzinktem Stahl oder aus Aluminium oder dessen Legierungen. Weiterhin kommen Werkstücke aus Magnesium oder Magnesiumlegierungen in Frage. If in the foregoing there was generally talk of metallic workpieces, this means in particular workpieces made of metals, as are common in the vehicle, furniture or household appliance industry. In particular, they are workpieces made of steel, galvanized or alloy-galvanized steel or of aluminum or its alloys. Workpieces made of magnesium or magnesium alloys are also suitable.

Claims

P a t e n t a n s p r ü c h e : Patent claims:
1. Verfahren zur Vorbehandlung eines metallischen Werkstücks für eine Lackierung, dessen zu lackierende Oberfläche mit Hilfe einer Entfettungsmittel enthaltenden Lösung gereinigt und mit einer korrosionshemmenden Schicht überzogen wird, dadurch gekennzeichnet, daß die zu lackierende Oberfläche des Werkstücks zum Auftragen einer korrosionshemmenden Schicht mit einer Lösung von Polyasparaginsäure behandelt wird.1. A method for pretreating a metallic workpiece for painting, the surface to be painted is cleaned with the aid of a degreasing agent solution and coated with a corrosion-inhibiting layer, characterized in that the surface of the workpiece to be painted is coated with a solution of a corrosion-inhibiting layer Polyaspartic acid is treated.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die zu lackierende Oberfläche des Werkstücks zum gleichzeitigen Entfetten und Beschichten mit einer Lösung von Polyasparaginsäure und einem Entfettungsmittel auf der Basis von Iminodibernsteinsäure-Natriumsalz behandelt wird.2. The method according to claim 1, characterized in that the surface to be painted of the workpiece is treated for simultaneous degreasing and coating with a solution of polyaspartic acid and a degreasing agent based on sodium iminodisuccinate.
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß das Gewichtsverhältnis von Polyasparaginsäure zu Iminodibernsteinsäure-Natriumsalz zwischen 10 : 1 und 1 : 10 liegt, wobei eine Mindestkonzentration an Polyasparaginsäure von 2 % in der Lösung eingestellt wird.3. The method according to claim 2, characterized in that the weight ratio of polyaspartic acid to iminodisuccinic acid sodium salt is between 10: 1 and 1:10, a minimum concentration of polyaspartic acid of 2% being set in the solution.
4. Verfahren nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß die mit den von der Werkstückoberfläche abgelösten Fetten belastete Lösung einer Membranfiltration unterworfen wird, wobei das Permeat in einem Kreislauf zur Oberflächenbehandlung des Werkstücks rückgeführt und das Retentat entsorgt wird.4. The method according to claim 2 or 3, characterized in that the solution loaded with the fats detached from the workpiece surface is subjected to membrane filtration, the permeate being recycled in a circuit for surface treatment of the workpiece and the retentate being disposed of.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß aus dem Permeat freie Metallionen abgeschieden werden, bevor es zur Werkstückbehandlung rückgeführt wird.5. The method according to claim 4, characterized in that free metal ions are deposited from the permeate before it is returned to the workpiece treatment.
6. Verfahren nach einem der Ansprüche 2 bis 5, dadurch gekennzeichnet, daß die zu lackierende Oberfläche des Werkstücks nach dem Entfetten einer weiteren Behandlung in einer 10 bis 40 %igen Lösung der Polyasparaginsäure unterworfen wird. 6. The method according to any one of claims 2 to 5, characterized in that the surface of the workpiece to be painted after degreasing another Treatment in a 10 to 40% solution of polyaspartic acid is subjected.
EP99931072A 1998-06-24 1999-06-15 Process of pre-treating a metallic workpiece before painting Expired - Lifetime EP1097255B1 (en)

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DE59902585D1 (en) 2002-10-10
WO1999067442A1 (en) 1999-12-29
US6432220B1 (en) 2002-08-13
CA2335987A1 (en) 1999-12-29
AT408103B (en) 2001-09-25
JP2002518602A (en) 2002-06-25
BR9912205A (en) 2001-04-10
ATA109198A (en) 2001-01-15
AU4772499A (en) 2000-01-10
EP1097255B1 (en) 2002-09-04

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