EP0791084B1 - Arrangement and method for electrophoretic enamelling by the 2-coat 1-bake method - Google Patents

Arrangement and method for electrophoretic enamelling by the 2-coat 1-bake method Download PDF

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Publication number
EP0791084B1
EP0791084B1 EP96931069A EP96931069A EP0791084B1 EP 0791084 B1 EP0791084 B1 EP 0791084B1 EP 96931069 A EP96931069 A EP 96931069A EP 96931069 A EP96931069 A EP 96931069A EP 0791084 B1 EP0791084 B1 EP 0791084B1
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EP
European Patent Office
Prior art keywords
processing bath
bath
enamel
rinsing
workpiece
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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.)
Expired - Lifetime
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EP96931069A
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German (de)
French (fr)
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EP0791084A1 (en
Inventor
Karl Wiengarten
Mario Sprickmann
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Miele und Cie KG
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Miele und Cie KG
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/02—Electrophoretic coating characterised by the process with inorganic material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/02—Electroplating of selected surface areas

Definitions

  • the invention relates to an arrangement for electrophoretic enamelling the 2-layer-1 fire process with a process bath for basic enamel application, at least one subsequent rinsing bath before a process bath for the cover enamel application with at least one subsequent rinsing bath and a stoving oven.
  • the invention further relates to a method for enamelling in the above. Arrangement.
  • ETE electrophoretic enamelling plant
  • 2-layer-1 fire method It is well known to metal parts in an electrophoretic enamelling plant (ETE) to be enamelled using the 2-layer-1 fire method.
  • ETE electrophoretic enamelling plant
  • Such System is usually with two process baths, several rinsing baths and one Process furnace equipped.
  • the basic email order is placed in the first process bath. It then connect two rinsing baths, with the first rinsing bath being physically more adherent Slurry is rinsed off. This can be done via an enamel recovery system be fed back to the first process bath.
  • the cover email After in a second If the rinsing bath is rinsed again, the order follows in a further process bath the cover email. This is usually followed by at least one rinsing bath, before the two enamel layers applied are baked together in the process furnace become.
  • the Slip component which adjusts the wrap, also separated.
  • the amount the email order is proportional to the current and thus also to the current density.
  • the current density is not over with irregularly shaped workpieces the entire surface is constant preferably at the points with the greatest current density (edges and curves) difficult and there are increasing enamelling errors.
  • From DE-PS 37 07 401 is a method for emailing in white or lighter Color known by the 2 layers - 1 fire method, in order to avoid a special basic enamel frit is selected from enamelling defects must have very special properties.
  • the disadvantage of such a method is that only a very specific composition of the basic enamel frit Can be used. The individual percentages of the Ingredients must be determined in previous tests. That requires are a lot of effort when putting together the frit and enamelling errors nonetheless cannot be ruled out at the problem areas of the workpiece to be coated.
  • DE-PS 36 26 424 discloses a method for the electrophoretic enamelling of aluminum-free enamel layers.
  • the base enamel is applied with a layer thickness of 80 - 120 ⁇ m and the specific conductivity of the cover enamel is set to a value below 2000 ⁇ S / cm -1 .
  • this method can only be used for catalytic cover enamel, since, in contrast to white enamel, this only represents an unmelted raw material mixture. This makes the cover email order easier.
  • the invention is therefore based on the object of an apparatus and a method for electrophoretic enamelling according to the 2-layer-1 fire process develop in which, regardless of the frit compositions of the basic and cover emails and the shape of the workpieces Cover emails are sent.
  • the advantages that can be achieved with the invention are, in particular, that when retained of the frits previously used creates an enamelled workpiece, which no more enamel defects.
  • This is achieved in particular by that an additional process bath between the basic and the cover email order is arranged.
  • This process bath contains a solution with a chemical substance, which has a high affinity for aluminum ions.
  • This substance is effective
  • Aluminum hydroxide goes on and / or goes undissociated with aluminum ions Connection.
  • Aluminum is part of the basic email and that's how you are able to take hold of the process in an additional process basin Improve procedures.
  • At least one rinse bath in which one is carried over Basic enamel slip or the chemical substance contained in the second process basin be rinsed off again before in a subsequent process the cover email order is placed. It is particularly advantageous if the first Rinsing bath after the basic email order a filter device is coupled in which entrained slip can be separated as a solid. This Slurry is either returned directly to the process pool for the basic email order supplied or disposed of separately. This saves valuable raw materials and the environment is less polluted. It proves to be particularly advantageous if the process bath temperature is kept constant and the substance to reduce the layer resistance of the basic enamel in the additional process bath in one defined constant concentration is present.
  • FIG. 1 shows an apparatus for electrophoretic enamelling after the second Layers 1 fire process shown schematically.
  • Each Process bath (1; 3; 5) should preferably have at least 1 rinse bath (2; 4; 6; 7) be subordinate.
  • the basic enamel slip (10) is located in the process bath (1), with which the workpiece (9) to be enamelled is coated. Subsequently loosely adhering is rinsed off in the first sink (2) Basic email (10).
  • This sink (2) is advantageously a Filter device (12) coupled, which entrained basic enamel slip (10) as Solid deposits. This can completely the first process bath (1) again be fed.
  • a conventional filter device (12) Solid filter or a settling tower can be used. Such filter devices (12) allow it, both the collected basic enamel slip (10) and the filtrate feed the corresponding baths (1 or 2) of the arrangement again or separately dispose.
  • a process bath (3) adjoins the sink (2) which is an addition of at least one substance, which is the aluminum hydroxide attacks and / or forms undissociated compounds with aluminum ions.
  • the chemical substance added to the process bath (3) reduces the electrical one Resistance of the separated enamel bisque. He will be in a subsequent Rinsing bath (4) rinsed off the workpiece (9) again. Then takes place in the last Process bath (5) a cover email order (11), which was pretreated by the corresponding Workpiece (9) can be done very evenly.
  • This process bath (5) close at least one, but preferably two rinsing baths (6, 7) before the two enamel layers (10, 11) are baked together in the process furnace (8) become.
  • Chemical substances are added to the process bath (3) which are capable of are attacking the aluminum hydroxide or the stable with aluminum ions Can enter into a connection.
  • acidic or basic substances are sufficient the requirements, which also react complexly, such as citric acid.
  • phosphoric acid is also suitable as Additive to the process bath (3).
  • the pH of the bath (3) can range from acidic to alkaline range vary.
  • the total phosphate content should be ISO 6878 T1 from 1986 (or according to DIN 38405 - Part 11) larger than 100 mg / l.
  • the substance to reduce the Sheet resistance in the process bath (3) in a defined constant concentration is available. Since the process bath temperature is also kept constant only the immersion time in this process bath (3) should define the treatment intensity.
  • the diving times should be for each new shape of a workpiece (9) be empirically determined beforehand. There is then the possibility of being different shaped workpieces (9) in an arbitrary order in the enamelling arrangement to send. The diving times are according to a previously made Determination assigned to the respective workpiece (9). The enamelling results are therefore equally good for all shapes of workpieces (9).
  • FIG. 2 shows a coated workpiece (9) in which the sheet resistance of the base enamel (10) is not reduced. At the ends of the workpiece (9) less cover enamel (11) is applied due to the increased application of base enamel (10) ( h 1 ⁇ h 2 ), so that there is not sufficient opacity of the cover enamel.
  • h 1 denotes the layer thickness of the cover enamel (11) in the edge areas and h 2 the layer thickness of the cover enamel (11) on the straight surfaces.
  • FIG. 3 shows an enamelled workpiece (9) in which the sheet resistance of the base enamel (10) has been reduced in a process bath (3) arranged after the process bath (1).
  • the electrical layer resistance was reduced by a chemical attack of the enamel bisque.
  • the process bath (3) contains substances which react both acid-base-buffering and complexing and / or form compounds which are undissociated with aluminum ions.
  • Citric acid or phosphates are particularly suitable as additives in this process bath (3).
  • An orthophosphate, for example, must have at least a PO 4 3 content of 100 mg / l in the solution in the process bath (3) in accordance with existing standards (ISO, DIN). By reducing the resistance, an almost even cover enamel application (11) is possible on the entire workpiece.
  • This equally thick layer (11) (h 1 ⁇ h 2 ) prevents the base enamel (10) from shimmering through, which is mostly dark due to the adhesive oxides necessarily contained therein.
  • the cover enamel (11) adapts continuously to the shape of the base enamel (10). With such an enamelling arrangement, it is irrelevant which shape the workpiece (9) has, whether there are curved edge regions or not
  • Figure 4 shows a lifting device (13), for example with the process bath (3) can be coupled.
  • a lifting device (13) workpieces (9) of the most varied Leave the shape of the variably set diving times in the bathroom (3).
  • treatment times are given for the different workpiece shapes determined empirically, for compliance with a correspondingly controlled operation the lifting device (13) as part of the lifting device (13)
  • an air cylinder can be used which is controlled in this way is that he the carrier with the workpiece (9) thereon accordingly raises or lowers.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Chemical Treatment Of Metals (AREA)

Description

Die Erfindung betrifft eine Anordnung zum elektrophoretischen Emaillieren nach dem 2 Schichten-1 Brand-Verfahren mit einem Prozeßbad zum Grundemailauftrag, mindestens einem nachfolgenden Spülbad vor einem Prozeßbad zum Deckemailauftrag mit mindestens einem nachfolgenden Spülbad und einem Einbrennofen. Die Erfindung betrifft weiterhin ein Verfahren zum Emaillieren in der o.g. Anordnung.The invention relates to an arrangement for electrophoretic enamelling the 2-layer-1 fire process with a process bath for basic enamel application, at least one subsequent rinsing bath before a process bath for the cover enamel application with at least one subsequent rinsing bath and a stoving oven. The invention further relates to a method for enamelling in the above. Arrangement.

Es ist allgemein bekannt, metallische Teile in einer Elektrophoretischen-Emaillieranlage (ETE) nach dem 2 Schichten-1 Brand-Verfahren zu emaillieren. Eine solche Anlage ist üblicherweise mit zwei Prozeßbädem, mehreren Spülbädem und einem Prozeßofen ausgestattet. Im ersten Prozeßbad erfolgt der Grundemailauftrag. Es schließen sich dann zwei Spülbäder an, wobei im ersten Spülbad physikalisch anhaftender Schlicker abgespült wird. Dieser kann über eine Emailrückgewinnungsanlage dem ersten Prozeßbad wieder zugeführt werden. Nachdem in einem zweiten Spülbad nochmals gespült wird, folgt in einem weiteren Prozeßbad der Auftrag des Deckemails. Diesem schließt sich üblicherweise mindestens ein Spülbad an, bevor die beiden aufgetragenen Emailschichten im Prozeßofen gemeinsam eingebrannt werden.It is well known to metal parts in an electrophoretic enamelling plant (ETE) to be enamelled using the 2-layer-1 fire method. Such System is usually with two process baths, several rinsing baths and one Process furnace equipped. The basic email order is placed in the first process bath. It then connect two rinsing baths, with the first rinsing bath being physically more adherent Slurry is rinsed off. This can be done via an enamel recovery system be fed back to the first process bath. After in a second If the rinsing bath is rinsed again, the order follows in a further process bath the cover email. This is usually followed by at least one rinsing bath, before the two enamel layers applied are baked together in the process furnace become.

Während des Abscheidens des Grundemails im ersten Prozeßbad wird auch die Schlickerkomponente, welche den Umgriff einstellt, mit abgeschieden. Die Menge des Emailauftrages ist proportional zur Stromstärke und somit auch zur Stromdichte. Die Stromdichte ist jedoch bei unregelmäßig geformten Werkstücken nicht über die gesamte Oberfläche konstant Daher wird eine Abscheidung des Deckemails bevorzugt an den Stellen mit der größten Stromdichte (Kanten und Rundungen) erschwert und es treten dort verstärkt Emaillierfehler auf.During the deposition of the basic enamel in the first process bath, the Slip component, which adjusts the wrap, also separated. The amount the email order is proportional to the current and thus also to the current density. However, the current density is not over with irregularly shaped workpieces the entire surface is constant preferably at the points with the greatest current density (edges and curves) difficult and there are increasing enamelling errors.

Aus der DE-PS 37 07 401 ist ein Verfahren zum Emailauftrag in weißer oder heller Farbe nach dem 2 Schichten- 1 Brand-Verfahren bekannt, bei dem zur Vermeidung von Emaillierfehlem eine spezielle Grundemailfritte ausgewählt wird, welche ganz besondere Eigenschaften aufweisen muß. Der Nachteil eines derartigen Verfahrens besteht darin, daß nur eine ganz bestimmte Zusammensetzung der Grundemailfritte Verwendung finden kann. Die einzelnen prozentualen Bestandteile der Inhaltsstoffe müssen in vorhergehenden Versuchen ermittelt werden. Das erfordert einen hohen Aufwand bei der Zusammenstellung der Fritte und Emaillierfehler sind an den Problemstellen des zu beschichtenden Werkstückes trotzdem nicht auszuschließen.From DE-PS 37 07 401 is a method for emailing in white or lighter Color known by the 2 layers - 1 fire method, in order to avoid a special basic enamel frit is selected from enamelling defects must have very special properties. The disadvantage of such a method is that only a very specific composition of the basic enamel frit Can be used. The individual percentages of the Ingredients must be determined in previous tests. That requires are a lot of effort when putting together the frit and enamelling errors nonetheless cannot be ruled out at the problem areas of the workpiece to be coated.

Die DE-PS 36 26 424 offenbart ein Verfahren zum elektrophoretischen Emaillieren Alfreier Emailschichten. Das Grundemail wird mit einer Schichtdicke von 80 - 120 µm aufgebracht und die spezifische Leitfähigkeit des Deckemails ist auf einen Wert unter 2000 µS/cm-1 eingestellt. Dieses Verfahren ist jedoch nur auf katalytisches Deckemail anwendbar, da dieses im Gegensatz zum Weißemail nur ein unerschmolzenes Rohstoffgemisch darstellt. Dadurch gestaltet sich der Deckemailauftrag einfacher.DE-PS 36 26 424 discloses a method for the electrophoretic enamelling of aluminum-free enamel layers. The base enamel is applied with a layer thickness of 80 - 120 µm and the specific conductivity of the cover enamel is set to a value below 2000 µS / cm -1 . However, this method can only be used for catalytic cover enamel, since, in contrast to white enamel, this only represents an unmelted raw material mixture. This makes the cover email order easier.

Der Erfindung liegt daher die Aufgabe zugrunde, eine Vorrichtung und ein Verfahren zum elektrophoretischen Emaillieren nach dem 2 Schichten-1 Brand Verfahren zu entwickeln, bei dem unabhängig von den Frittenzusammensetzungen des Grund- und Deckemails und der Form der Werkstücke eine gleichmäßige Abscheidung des Deckemails erfolgt.The invention is therefore based on the object of an apparatus and a method for electrophoretic enamelling according to the 2-layer-1 fire process develop in which, regardless of the frit compositions of the basic and cover emails and the shape of the workpieces Cover emails are sent.

Die Aufgabe wird durch die Merkmale der Patentansprüche 1 und 5 gelöst. Vorteilhafte Ausgestaltungen und Weiterbildungen ergeben sich aus den nachfolgenden Ansprüchen.The object is achieved by the features of claims 1 and 5. advantageous Refinements and developments result from the following Claims.

Die mit der Erfindung erzielbaren Vorteile liegen insbesondere darin, daß bei Beibehaltung der bisher eingesetzten Fritten ein emailliertes Werkstück entsteht, welches keine Emaillierfehler mehr aufweist. Dieses wird insbesondere dadurch erreicht, daß zwischen dem Grund- und dem Deckemailauftrag ein zusätzliches Prozeßbad angeordnet ist. Dieses Prozeßbad enthält eine Lösung mit einem chemischen Stoff, welcher eine hohe Affinität zu Aluminiumionen besitzt. Dieser Stoff greift Aluminiumhydroxid an und/oder geht mit Aluminiumionen eine undissoziierte Verbindung ein. Aluminium ist ein Bestandteil des Grundemails und so ist man imstande, den Umgriff durch das in einem zusätzlichen Prozeßbecken ablaufende Verfahren zu verbessern. Vor und nach diesem zusätzlichen Prozeßbad ist vorzugsweise jeweils mindestens ein Spülbad anzuordnen, in welchen verschleppter Grundemailschlicker bzw. der im zweiten Prozeßbecken enthaltene chemische Stoff wieder abgespült werden, bevor in einem nachfolgenden Prozeß becken der Deckemailauftrag erfolgt. Besonders vorteilhaft ist es, wenn dem ersten Spülbad nach dem Grundemailauftrag eine Filtereinrichtung angekoppelt wird, in welcher verschleppter Schlicker als Feststoff abgeschieden werden kann. Dieser Schlicker wird entweder direkt dem Prozeßbad für den Grundemailauftrag wieder zugeführt oder gesondert entsorgt Dadurch können wertvolle Rohstoffe eingespart und die Umwelt weniger belastet werden. Als besonders vorteilhaft erweist es sich, wenn die Prozeßbadtemperatur konstant gehalten wird und der Stoff zum Verringem des Schichtwiderstandes des Grundemails im zusätzlichen Prozeßbad in einer definierten konstanten Konzentration vorhanden ist.The advantages that can be achieved with the invention are, in particular, that when retained of the frits previously used creates an enamelled workpiece, which no more enamel defects. This is achieved in particular by that an additional process bath between the basic and the cover email order is arranged. This process bath contains a solution with a chemical substance, which has a high affinity for aluminum ions. This substance is effective Aluminum hydroxide goes on and / or goes undissociated with aluminum ions Connection. Aluminum is part of the basic email and that's how you are able to take hold of the process in an additional process basin Improve procedures. Before and after this additional process bath is preferred to arrange at least one rinse bath, in which one is carried over Basic enamel slip or the chemical substance contained in the second process basin be rinsed off again before in a subsequent process the cover email order is placed. It is particularly advantageous if the first Rinsing bath after the basic email order a filter device is coupled in which entrained slip can be separated as a solid. This Slurry is either returned directly to the process pool for the basic email order supplied or disposed of separately. This saves valuable raw materials and the environment is less polluted. It proves to be particularly advantageous if the process bath temperature is kept constant and the substance to reduce the layer resistance of the basic enamel in the additional process bath in one defined constant concentration is present.

Die Erfindung soll anhand des nachfolgenden Ausführungsbeispiels näher beschrieben werden. Es zeigen:

Figur 1
eine schematische Darstellung der Anordnung zum elektrophoretischen Emaillieren nach dem 2 Schichten-1 Brand- Verfahren
Figur 2
ein mit Grund- und Deckemail beschichtetes Werkstück bei Beibehaltung des elektrischen Widerstandes der Grundemailschicht in Schnittdarstellung
Figur 3
ein mit Grund- und Deckemail beschichtetes Werkstück bei Zurücknahme des elektrischen Widerstandes im Grundemail im Schnitt
Figur 4
ein schematisch dargestelltes Prozeßbad mit Hebevorrichtung.
The invention will be described in more detail using the following exemplary embodiment. Show it:
Figure 1
a schematic representation of the arrangement for electrophoretic enamelling according to the 2-layer-1 fire process
Figure 2
a workpiece coated with base and top enamel while maintaining the electrical resistance of the base enamel layer in a sectional view
Figure 3
a workpiece coated with base and cover enamel when the electrical resistance in the base enamel is reduced
Figure 4
a schematically illustrated process bath with lifting device.

In der Figur 1 ist eine Vorrichtung zum elektrophoretischen Emaillieren nach dem 2 Schichten 1 Brand- Verfahren schematisch dargestellt. Beim Emaillieren nach diesem Verfahren werden Prozeßbäder und Spülbäder in bekannter Weise abwechselnd in einer bestimmten Reihenfolge nacheinander angeordnet. Jedem Prozeßbad (1; 3; 5) sollte vorzugsweise mindestens 1 Spülbad (2; 4; 6; 7) nachgeordnet sein. Im Prozeßbad (1) befindet sich der Grundemailschlicker (10), mit welchem das zu emaillierende Werkstück (9) beschichtet wird. Anschließend erfolgt im ersten Spülbecken (2) ein Abspülen von lose anhaftendem Grundemail (10). An dieses Spülbecken (2) ist vorteilhafterweise eine Filtereinrichtung (12) gekoppelt, welche verschleppten Grundemailschlicker (10) als Feststoff abscheidet. Dieser kann dem ersten Prozeßbad (1) vollständig wieder zugeführt werden. Als Filtereinrichtung (12) sind beispielsweise ein herkömmlicher Feststoffilter oder ein Absetzturm einsetzbar. Derartige Filtereinrichtungen (12) erlauben es, sowohl den aufgefangenen Grundemailschlicker (10) als auch das Filtrat wieder den entsprechenden Bädern (1 bzw. 2) der Anordnung zuzuführen oder getrennt zu entsorgen. An das Spülbecken (2) schließt sich ein Prozeßbad (3) an, in welchem sich ein Zusatz von mindestens einem Stoff befindet, welcher das Aluminiumhydroxid angreift und/oder mit Aluminiumionen undissoziierte Verbindungen bildet. Der dem Prozeßbad (3) zugegebene chemische Stoff verringert den elektrischen Widerstand des abgeschiedenen Emailbisquits. Er wird in einem nachfolgenden Spülbad (4) wieder vom Werkstück (9) abgespült. Anschließend erfolgt im letzten Prozeßbad (5) ein Deckemailauftrag (11), welcher durch das entsprechend vorbehandelte Werkstück (9) sehr gleichmäßig erfolgen kann. Diesem Prozeßbad (5) schließen sich mindestens ein, vorzugsweise jedoch zwei Spülbäder (6, 7) an, bevor die beiden Emailschichten (10, 11) gemeinsam im Prozeßofen (8) eingebrannt werden.FIG. 1 shows an apparatus for electrophoretic enamelling after the second Layers 1 fire process shown schematically. When enamelling after this Process baths and rinsing baths are known processes alternately arranged in a certain order one after the other. Each Process bath (1; 3; 5) should preferably have at least 1 rinse bath (2; 4; 6; 7) be subordinate. The basic enamel slip (10) is located in the process bath (1), with which the workpiece (9) to be enamelled is coated. Subsequently loosely adhering is rinsed off in the first sink (2) Basic email (10). This sink (2) is advantageously a Filter device (12) coupled, which entrained basic enamel slip (10) as Solid deposits. This can completely the first process bath (1) again be fed. For example, a conventional filter device (12) Solid filter or a settling tower can be used. Such filter devices (12) allow it, both the collected basic enamel slip (10) and the filtrate feed the corresponding baths (1 or 2) of the arrangement again or separately dispose. A process bath (3) adjoins the sink (2) which is an addition of at least one substance, which is the aluminum hydroxide attacks and / or forms undissociated compounds with aluminum ions. The chemical substance added to the process bath (3) reduces the electrical one Resistance of the separated enamel bisque. He will be in a subsequent Rinsing bath (4) rinsed off the workpiece (9) again. Then takes place in the last Process bath (5) a cover email order (11), which was pretreated by the corresponding Workpiece (9) can be done very evenly. This process bath (5) close at least one, but preferably two rinsing baths (6, 7) before the two enamel layers (10, 11) are baked together in the process furnace (8) become.

Es werden dem Prozeßbad (3) chemische Stoffe zugegeben, die in der Lage sind, das Aluminiumhydroxid anzugreifen oder die mit Aluminiumionen eine stabile Verbindung eingehen können. Beispielsweise genügen saure oder basische Stoffe den Anforderungen, welche auch komplexierend reagieren, wie zum Beispiel Zitronensäure. Weiterhin ist es möglich, einen Stoff dem Prozeßbad (3) zuzusetzen, welcher den abgeschiedenen Emailbisquit nur anlöst, um den elektrischen Widerstand dieser Schicht zu verringern. Daher eignet sich auch Phosphorsäure gut als Zusatzstoff zum Prozeßbad (3). Der pH-Wert des Bades (3) kann vom sauren bis alkalischen Bereich variieren. Der Gesamtphosphatgehalt sollte dabei nach ISO 6878 T1 von 1986 (bzw. entsprechend DIN 38405 - Teil 11) größer als 100 mg/l sein.Chemical substances are added to the process bath (3) which are capable of are attacking the aluminum hydroxide or the stable with aluminum ions Can enter into a connection. For example, acidic or basic substances are sufficient the requirements, which also react complexly, such as citric acid. It is also possible to add a substance to the process bath (3) which only triggers the deposited enamel bisquit to reduce the electrical resistance decrease this layer. Therefore, phosphoric acid is also suitable as Additive to the process bath (3). The pH of the bath (3) can range from acidic to alkaline range vary. The total phosphate content should be ISO 6878 T1 from 1986 (or according to DIN 38405 - Part 11) larger than 100 mg / l.

Versuche haben gezeigt, daß ein zusätzliches Prozeßbad (3) eine deutliche Verbesserung der Kantenbeschichtung des Werkstückes (9) bewirkt. Die Emailhaftung ist sowohl bei der Verwendung von Zitronensäure als auch beim Zusatz von Phosphorsäure zu diesem Prozeßbad (3) sehr gut. Beim fertig emaillierten Werkstück (9) sind farblich keine Unterschiede feststellbar. Die Schichtdicken des Deckemails (11) sind bei Anwendung von einem der genannten Zusatzstoffe im Prozeßbad (3) jeweils gleichmäßig.Tests have shown that an additional process bath (3) is a significant improvement the edge coating of the workpiece (9). The email liability is both when using citric acid and when adding phosphoric acid to this process bath (3) very well. With the finished enamelled workpiece (9) there are no differences in color. The layer thickness of the cover enamel (11) are each when using one of the additives mentioned in the process bath (3) evenly.

Als besonders vorteilhaft erweist es sich, wenn der Stoff zum Verringern des Schichtwiderstandes im Prozeßbad (3) in einer definierten konstanten Konzentration vorhanden ist. Da die Prozeßbadtemperatur ebenfalls konstant gehalten werden sollte, definiert nur noch die Tauchzeit in diesem Prozeßbad (3) die Behandlungsintensität. Die Tauchzeiten sollten für jede neue Form eines Werkstückes (9) zuvor empirisch ermittelt werden. Es besteht dann die Möglichkeit, die unterschiedlich geformten Werkstücke (9) in einer wahlloser Reihenfolge in die Emaillieranordnung zu schicken. Die Tauchzeiten werden entsprechend einer vorher getroffenen Festlegung dem jeweiligen Werkstück (9) zugeordnet. Die Emaillierergebnisse sind dadurch bei allen Formen der Werkstücke (9) gleich gut.It proves to be particularly advantageous if the substance to reduce the Sheet resistance in the process bath (3) in a defined constant concentration is available. Since the process bath temperature is also kept constant only the immersion time in this process bath (3) should define the treatment intensity. The diving times should be for each new shape of a workpiece (9) be empirically determined beforehand. There is then the possibility of being different shaped workpieces (9) in an arbitrary order in the enamelling arrangement to send. The diving times are according to a previously made Determination assigned to the respective workpiece (9). The enamelling results are therefore equally good for all shapes of workpieces (9).

In der Figur 2 ist ein beschichtetes Werkstück (9) dargestellt, bei dem der Schichtwiderstand des Grundemails (10) nicht verringert ist An den Enden des Werkstücks (9) wird durch den verstärkten Auftrag von Grundemail (10) weniger Deckemail (11) aufgetragen (h1 < h2), so daß eine ausreichende Deckkraft des Deckemails nicht durchgängig gegeben ist Mit h1 wird dabei die Schichtdicke des Deckemails (11) in den Randbereichen und mit h2 die Schichtdicke des Deckemails (11) an den geraden Flächen bezeichnet.FIG. 2 shows a coated workpiece (9) in which the sheet resistance of the base enamel (10) is not reduced. At the ends of the workpiece (9) less cover enamel (11) is applied due to the increased application of base enamel (10) ( h 1 <h 2 ), so that there is not sufficient opacity of the cover enamel. h 1 denotes the layer thickness of the cover enamel (11) in the edge areas and h 2 the layer thickness of the cover enamel (11) on the straight surfaces.

Die Figur 3 zeigt dagegen ein emailliertes Werkstück (9) bei dem der Schichtwiderstand des Grundemails (10) in einem nach dem Prozeßbad (1) angeordneten Prozeßbad (3) verringert wurde. Die Verringerung des elektrischen Schichtwiderstandes ist durch einen chemischen Angriff des Emailbisquits erfolgt. Dazu enthält das Prozeßbad (3) Stoffe, die sowohl sauer-basisch-puffernd als auch komplexierend reagieren und/oder mit Aluminiumionen undissoziierte Verbindungen eingehen. Als Zusatzstoffe in diesem Prozeßbad (3) eignen sich insbesondere Zitronensäure oder Phosphate. Ein ortho-Phosphat muß beispielsweise entsprechend vorhandener Normen (ISO, DIN) in der Lösung im Prozeßbad (3) mindestens einen PO4 3- -Gehalt von 100 mg/l aufweisen. Durch die Zurücknahme des Widerstandes wird auf dem gesamten Werkstück ein annähernd gleichmäßiger Deckemailauftrag (11) möglich. Diese gleichstarke Schicht (11) (h1 ≈ h2) verhindert ein Durchschimmern des Grundemails (10), welches durch darin notwendigerweise enthaltene Haftoxide meistens dunkel ist. Das Deckemail (11) paßt sich durchgängig der Form des Grundemails (10) an. Es ist bei einer derartigen Emaillieranordnung also unerheblich, welche Form das Werkstück (9) aufweist, ob gekrümmte Randbereiche vorhanden sind oder nichtFIG. 3, on the other hand, shows an enamelled workpiece (9) in which the sheet resistance of the base enamel (10) has been reduced in a process bath (3) arranged after the process bath (1). The electrical layer resistance was reduced by a chemical attack of the enamel bisque. For this purpose, the process bath (3) contains substances which react both acid-base-buffering and complexing and / or form compounds which are undissociated with aluminum ions. Citric acid or phosphates are particularly suitable as additives in this process bath (3). An orthophosphate, for example, must have at least a PO 4 3 content of 100 mg / l in the solution in the process bath (3) in accordance with existing standards (ISO, DIN). By reducing the resistance, an almost even cover enamel application (11) is possible on the entire workpiece. This equally thick layer (11) (h 1 ≈ h 2 ) prevents the base enamel (10) from shimmering through, which is mostly dark due to the adhesive oxides necessarily contained therein. The cover enamel (11) adapts continuously to the shape of the base enamel (10). With such an enamelling arrangement, it is irrelevant which shape the workpiece (9) has, whether there are curved edge regions or not

Figur 4 zeigt eine Hebevorrichtung (13), welche beispielsweise mit dem Prozeßbad (3) gekoppelt werden kann. Bei konstanter Konzentration in diesem Prozeßbad (3) erlaubt eine derartige Hebevorrichtung (13) Werkstücke (9) unterschiedlichster Form entsprechend variabel eingerichteter Tauchzeiten im Bad (3) zu belassen. Vorher werden für die unterschiedlichen Werkstückformen Behandlungszeiten empirisch ermittelt, für deren Einhaltung eine entsprechend gesteuerte Betätigung der Hebevorrichtung (13) sorgt Als Bestandteil der Hebevorrichtung (13) kann beispielsweise ein Luftzylinder zum Einsatz gelangen, welcher so angesteuert wird, daß er die Tragvorrichtung mit dem daran befindlichen Werkstück (9) entsprechend anhebt bzw. absenkt.Figure 4 shows a lifting device (13), for example with the process bath (3) can be coupled. With constant concentration in this process bath (3) allows such a lifting device (13) workpieces (9) of the most varied Leave the shape of the variably set diving times in the bathroom (3). Before that, treatment times are given for the different workpiece shapes determined empirically, for compliance with a correspondingly controlled operation the lifting device (13) as part of the lifting device (13) For example, an air cylinder can be used which is controlled in this way is that he the carrier with the workpiece (9) thereon accordingly raises or lowers.

Claims (10)

  1. Arrangement for electrophoretic enamelling in accordance with the 2-coat 1-bake method, having a processing bath for the base enamel coating, at least one subsequent rinsing bath upstream of a processing bath for the top enamel coating, with at least one rinsing bath subsequent thereto and one baking oven, characterised in that, downstream of the processing bath (1) containing the base enamel dross and upstream of the processing bath (5) containing the top enamel dross, there is disposed a processing bath (3), to which is added at least one substance which chemically attacks aluminium hydroxide, said substance reacting in an acidic-basic buffering and complexing manner and/or reducing compounds undissociated with aluminium ions.
  2. Arrangement according to claim 1, characterised in that at least one rinsing bath (2) is disposed downstream of the processing bath (1) containing the base enamel dross and upstream of the processing bath (3), and/or at least one rinsing bath (4) is disposed downstream of the processing bath (3) and upstream of the processing bath (5) containing the top enamel dross.
  3. Arrangement according to at least one of claims 1 or 2, characterised in that the rinsing bath (2) is connected to a filtering means (12).
  4. Arrangement according to at least one of claims 1 to 3, characterised in that a lifting apparatus (13) is associated with the processing bath (3) for handling the workpieces (9).
  5. Method of electrophoretic enamelling according to the 2-coat 1-bake method, wherein a workpiece to be treated, after being coated with the base enamel layer, is rinsed at least once before the top enamel coating is applied and, after a fresh rinsing process, both layers are baked together, characterised in that, subsequent to the base enamel coating in the processing bath (1) and prior to the top enamel coating in the processing bath (5), the workpiece is subjected to a treatment in a processing bath (3), this processing bath (3) containing at least one chemical substance which reacts in an acidic-basic buffering and complexing manner and attacks aluminium hydroxide and/or reduces compounds undissociated with aluminium ions.
  6. Method according to claim 5, characterised in that, subsequent to the base enamel coating and prior to the treatment in the processing bath (3) and/or subsequent to the treatment in the processing bath (3), the workpiece is rinsed at least once before the top enamel coating is applied.
  7. Method according to at least one of claims 5 or 6, characterised in that entrained base enamel dross is rinsed from the workpiece (9) during the rinsing process (2) and is filtered-out by a filtering means (12) and re-supplied to the processing bath (1) or collected separately, and/or the filtrate is conducted into a rinsing bath (2; 4) or a separate collecting vessel.
  8. Method according to at least one of claims 5 or 6, characterised in that a solution, which has complexing properties and reacts in an acidic or alkaline manner, is contained in the processing bath (3).
  9. Method according to claim 8, characterised in that citric acid or phosphate is contained in the processing bath (3).
  10. Method according to at least one of claims 5 to 9, characterised in that the processing bath (3) has a constant temperature, and the chemical substance is contained therein in a constant, specific concentration, and in that the treatment of the workpiece (9) is effected in the processing bath (3) in a treatment time dependent on its configuration.
EP96931069A 1995-09-13 1996-09-11 Arrangement and method for electrophoretic enamelling by the 2-coat 1-bake method Expired - Lifetime EP0791084B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19533668 1995-09-13
DE19533668A DE19533668A1 (en) 1995-09-13 1995-09-13 Arrangement and method for electrophoretic enamelling according to the 2-layer-1 fire method
PCT/EP1996/003974 WO1997010371A1 (en) 1995-09-13 1996-09-11 Arrangement and method for electrophoretic enamelling by the 2-coat 1-bake method

Publications (2)

Publication Number Publication Date
EP0791084A1 EP0791084A1 (en) 1997-08-27
EP0791084B1 true EP0791084B1 (en) 2000-03-15

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US (1) US5855754A (en)
EP (1) EP0791084B1 (en)
DE (2) DE19533668A1 (en)
WO (1) WO1997010371A1 (en)

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US7704895B2 (en) * 2008-04-02 2010-04-27 Intel Corporation Deposition method for high-k dielectric materials

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4208262A (en) * 1978-05-11 1980-06-17 Shinto Paint Co., Ltd. Electrodeposition coating
DE3203101A1 (en) * 1982-01-30 1983-08-04 Bayer Ag, 5090 Leverkusen Enamel slip, and a process for two- and multicoat enamelling in one batch
JPH0686674B2 (en) * 1985-12-04 1994-11-02 関西ペイント株式会社 Electrodeposition coating method
DE3707401A1 (en) * 1987-03-07 1988-09-15 Bayer Ag METHOD FOR ELECTROPHORETIC WHITE AND COLOR MAILING
US4904365A (en) * 1988-02-29 1990-02-27 Trinity Industrial Corporation Electrodeposition coating facility

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DE59604682D1 (en) 2000-04-20
WO1997010371A1 (en) 1997-03-20
US5855754A (en) 1999-01-05
DE19533668A1 (en) 1997-03-20
EP0791084A1 (en) 1997-08-27

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