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EP0229115B1 - Device for the cathodic protection of metal parts from corrosion - Google Patents

Device for the cathodic protection of metal parts from corrosion Download PDF

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Publication number
EP0229115B1
EP0229115B1 EP86904027A EP86904027A EP0229115B1 EP 0229115 B1 EP0229115 B1 EP 0229115B1 EP 86904027 A EP86904027 A EP 86904027A EP 86904027 A EP86904027 A EP 86904027A EP 0229115 B1 EP0229115 B1 EP 0229115B1
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EP
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Prior art keywords
electrode
protected
metal parts
metal
electrolyte
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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.)
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EP86904027A
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German (de)
French (fr)
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EP0229115A1 (en
Inventor
Reinhold Herzog
Reinhard Padinger
Hans-Peter Rainer
Heimo Schober
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D 3 Cathodic Products-Korrosionsschutzprodukte GmbH
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D 3 Cathodic Products-Korrosionsschutzprodukte GmbH
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    • 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
    • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions

Definitions

  • the invention relates to a device for cathodic corrosion protection of metal parts that are not buried in the ground, e.g. of metal parts of vehicles in which a potential difference between the metal parts to be protected and an electrolyte, if any, on the metal part, with which the electrode comes into electrical contact, is generated using at least one exposed electrode that is electrically insulated from the metal parts to be protected and at least one voltage source is so that a direct current from the electrolyte enters the metal surface at points to be protected on the metal surface, which counteracts the migration of positive metal ions from the metal surface.
  • the metal parts to be protected against corrosion in particular vehicle parts, can simply be connected to the negative pole of a voltage source and the positive pole of this voltage source connected to the named electrode.
  • the electrode is attached in such a way that it creates an electrically conductive connection to an electrolyte (moist dust, salt water, slush and the like) which may be on the surface of the metal parts to be protected, with a direct electrical connection of the electrodes to the metal parts to be protected by a corresponding insulating layer (lacquer) is avoided.
  • an electrolyte moist dust, salt water, slush and the like
  • lacquer a corresponding insulating layer
  • the potential of the electrolyte in the vicinity of the point to be protected measured against a Cu / CuS0 4 electrode, must be at least approximately 0.85 volt more positive than the potential of the point to be protected Metal.
  • the electrode which is to produce an electrically conductive connection to the electrolyte layer located on the metal surface to be protected, is a plate-like exposed structure, the dimensions of which are compared to the dimensions of the metal surface to be protected are small.
  • This electrode is held with a clamp at a short distance above the metal surface and comes into an electrically conductive connection when the electrolyte layer becomes wet.
  • the comparatively small surface area of the electrode and the small differences between its length and width result in a high current density in the electrolyte layer in the vicinity of the electrode; in order to achieve a protective effect at a greater distance from the electrode, a relatively large voltage must be applied, and this leads, inter alia, to the formation of acid-forming conditions in the immediate vicinity of the electrode, which in itself can lead to corrosive effects there.
  • the electrode of this known device is metallic, preferably a material is selected which gives a low consumption rate under anodic conditions.
  • a corrosion protection technique is known from US Pat. No. 3,498,898, in which the metal surfaces to be protected are coated with a first lacquer layer are coated, on which a thin nickel layer is applied, to which further layers of lacquer are then applied; the metal object to be protected on the one hand and the nickel layer on the other hand are connected to the two poles of a direct current source.
  • the Nikkei layer thus forms a covered electrode. If the electrically insulating lacquer layers are damaged, a cathodic or anodic protective effect can develop when an electrolyte is present at the fault location. Since such injuries are generally small in size, there is increasing difficulty in providing corrosion protection outside of the coated area, and this technique is difficult to apply in view of the multiple coating required on complex multi-part surfaces.
  • the device according to the invention of the type mentioned above is characterized in that the electrode is designed as an electrically conductive strip or electrically conductive flexible strip or as an electrically conductive coating which extends linearly and / or over a large part of the dimensions of the metal surface to be protected attached to this metal surface in an electrically insulated manner.
  • the electrode is designed as an electrically conductive strip or electrically conductive flexible strip or as an electrically conductive coating which extends linearly and / or over a large part of the dimensions of the metal surface to be protected attached to this metal surface in an electrically insulated manner.
  • the electrodes used in the previously known devices are designed in such a way that the cathodic protective current essentially enters the electrolyte centrally from the electrodes and spreads along it along essentially centric current lines, thereby increasing current densities in the vicinity of the electrodes and thus increasing them Voltage drops occur.
  • FIG. 1 shows the flow field and potential course in the vicinity of an electrode A which is applied to an extended surface conductor and is kept small compared to the surface conductor with counter electrodes which are far away.
  • the occurrence of increased current densities and thus increased voltage drops is avoided, and the range of action of the electrodes compared to conventional electrodes is thereby significantly increased.
  • electrodes 1 used which are linearly extended in at least one direction over wide areas of the metal surface to be protected, for example conductive adhesive tapes or conductive decorative strips, so that the current which emerges from them is illustrated in FIG. 2, spreads in the vicinity of the electrodes along essentially parallel current lines in the electrolyte and, as a result, there are no increased current densities and therefore no increased voltage drops.
  • electrodes 9 are used in FIG. 5, which are extended over large areas of the metal surface to be protected, for example conductive coatings, in particular conductive underbody protection or conductive cavity protection, or according to FIG. 6 electrodes 10, which are spatially extended and which Touch metal parts to be protected over large areas, for example conductive fillers for cavities in the vehicle body.
  • the device according to the invention has at least one electrode which can be brought into contact with the metal surface to be protected, preferably glued on or applied as a coating or introduced into cavities.
  • the electrode is designed so that it is on the metal surface to be protected or on a coating (lacquer) on the metal surface can be brought into abutment in at least one direction over wide areas. Electrodes 1 that extend in a line, or electrodes 9 that extend in a flat area or electrodes 10 that are spatially extended are possible.
  • the device also has an electrical connecting line 4, with which the electrode can be connected to the positive pole of a voltage source 2.
  • the electrode is preferably made of a material which has no ionic conductivity at the interface with the electrolyte 3, for example made of graphite or a graphitized carrier material, for example graphitized rubber, so that they are not degraded by the current like they are known or "sacrificial anodes" are, for example, metallic and surrounded by such a non-ion-conductive material.
  • the electrodes can preferably be designed as flexible, easily cut-to-length adhesive tapes, which can be attached to the surface of vehicles in a simple manner, whereby they can adapt to the contours of the vehicle and in this way can extend linearly over large areas of the metal surface to be protected .
  • connection 5 to the electrode takes place, as shown in FIG. 3, by a preferably insulated connecting line 4, which can be connected at one end to the positive pole of a voltage source 2 and can be connected to the electrode at the other end, whereby the connection 5 to the electrode is preferably made via a conductor already described, which has no ionic conductivity at the interface with the electrolyte 3.
  • the device is optionally provided with a current limiting device 6 known per se, preferably an electrical resistor or an electrical fuse, optionally with a voltage limiting device 7 known per se, preferably a voltage divider, and optionally with an operating display device 8 known per se, preferably a control lamp.
  • a current limiting device 6 known per se, preferably an electrical resistor or an electrical fuse
  • a voltage limiting device 7 known per se, preferably a voltage divider
  • an operating display device 8 known per se, preferably a control lamp.
  • FIG. 3 shows how a device according to the invention can be provided on a vehicle body.
  • FIG. 4 illustrates the attachment of a linearly extended electrode to a vehicle underbody
  • FIG. 5 illustrates the attachment of an areally extended electrode to a vehicle underbody.
  • Fig. 6 illustrates the placement of a spatially extended electrode 10 in a cavity of a vehicle body, e.g. an entry beam 11, the electrode 10 touching the metal parts that delimit the cavity over a large area.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Prevention Of Electric Corrosion (AREA)
  • Buildings Adapted To Withstand Abnormal External Influences (AREA)

Abstract

PCT No. PCT/AT86/00048 Sec. 371 Date Apr. 24, 1987 Sec. 102(e) Date Apr. 24, 1987 PCT Filed Jul. 14, 1986 PCT Pub. No. WO87/00558 PCT Pub. Date Jan. 29, 1987.A device for the cathodic protection of metal parts in which electrodes and a voltage source are used to charge positively an electrolyte in relation to the metal surface which is to be protected. The electrodes (1) are so designed that they extend linearly and/or superficially over extensive areas of the metal surface to be protected.

Description

Die Erfindung bezieht sich auf eine Vorrichtung zum kathodischen Korrosionsschutz von Metallteilen, die nicht im Erdboden verlegt sind, z.B. von Metallteilen von Fahrzeugen, bei der mit Hilfe zumindest einer freiliegenden und von den zu schützenden Metallteilen elektrisch isolierten Elektrode und zumindest einer Spannungsquelle eine Potentialdifferenz zwischen den zu schützenden Metallteilen und einem allenfalls am Metallteil befindlichen Elektrolyten, mit dem die Elektrode elektrisch in Verbindung kommt, erzeugt wird, so daß an zu schützenden Stellen der Metalloberfläche ein Gleichstrom vom Elektrolyten in die Metalloberfläche eintritt, welcher dem Abwandern positiver Metallionen von der Metalloberfläche entgegenwirkt.The invention relates to a device for cathodic corrosion protection of metal parts that are not buried in the ground, e.g. of metal parts of vehicles in which a potential difference between the metal parts to be protected and an electrolyte, if any, on the metal part, with which the electrode comes into electrical contact, is generated using at least one exposed electrode that is electrically insulated from the metal parts to be protected and at least one voltage source is so that a direct current from the electrolyte enters the metal surface at points to be protected on the metal surface, which counteracts the migration of positive metal ions from the metal surface.

Seit Beginn der Salzstreuung auf den Straßen zur Vermeidung von Schnee- und Eisglätte sind die Fahrzeuge einer erheblichen Korrosionsbelastung ausgesetzt. Durchgerostete Karrosserie-und Rahmenteile gefährden die Verkehrs- und Betriebssicherheit des Fahrzeuges und verkürzen erheblich dessen Nutzungsdauer. Durch entsprechende Anstriche oder Beschichtungen (Unterbodenschutz, Hohlraumschutz) wird heute versucht, dem Korrosionsvorgang entgegenzuwirken. Neben diesen "passiven" Korrosionsschutzmaßnahmen gibt es die Möglichkeit des "aktiven" Korrosionsschutzes durch einen der Korrosion entgegenwirkenden Gleichstrom, welche Technik oft "Kathodischer Korrosionsschutz" genannt wird und bei stationären Anlagen (Stahlbehälter, Stahlrohrleitungen etc.) sowie auch bei Fahrzeugen bereits seit längerem angewendet wird. Vorrichtungen eingangs erwähnter Art arbeiten nach dieser Technik.Since the beginning of salt spreading on the roads to avoid snow and ice, the vehicles have been exposed to considerable corrosion. Rusted body and frame parts endanger the traffic and operational safety of the vehicle and significantly shorten its service life. Appropriate coatings or coatings (underbody protection, cavity protection) are used today to counteract the corrosion process. In addition to these "passive" corrosion protection measures, there is the possibility of "active" corrosion protection by means of a direct current that counteracts the corrosion, which technology is often called "cathodic corrosion protection" and has been used for a long time in stationary systems (steel tanks, steel pipes, etc.) and in vehicles becomes. Devices of the type mentioned initially work according to this technique.

Bei einer solchen Vorrichtung kann man die vor Korrosion zu schützenden Metallteile, insbesondere Fahrzeugteile, einfach an den negativen Pol einer Spannungsquelle anschließen und den positiven Pol dieser Spannungsquelle mit der genanten Elektrode verbinden. Die Elektrode wird so angebracht, daß sie zu einem gegebenenfalls an der Oberfläche der zu schützenden Metallteile befindlichen Elektrolyten (feuchter Staub, Salzwasser, Schneematsch und dergl.) eine elektrisch leitende Verbindung herstellt, wobei eine direkte elektrische Verbindung der Elektroden zu den zu schützenden Metallteilen durch eine entsprechend isolierende Schicht (Lack) jedoch vermieden wird. Mit einer solchen Elektrode kann man so den an der Oberfläche der zu schützenden Metallteile befindlichen Elektrolyten auf positives potential gegenüber den zu schützenden Metallteilen anheben. Dies hat zur Folge, daß z.B. an schadhaften Stellen einer Lackierung, wie sie beispielsweise durch mechanische Einwirkungen, insbesondere durch das Aufprallen von Streusand oder dergl., entstehen können, ein Gleichstrom vom Elektrolyten in die Metalloberfläche fließt, welcher dem Abwandern positiver Metallionen von der Metalloberfläche entgegenwirkt und damit den sogenannten "Kathodischen Korrosionsschutz" bewirkt.In such a device, the metal parts to be protected against corrosion, in particular vehicle parts, can simply be connected to the negative pole of a voltage source and the positive pole of this voltage source connected to the named electrode. The electrode is attached in such a way that it creates an electrically conductive connection to an electrolyte (moist dust, salt water, slush and the like) which may be on the surface of the metal parts to be protected, with a direct electrical connection of the electrodes to the metal parts to be protected by a corresponding insulating layer (lacquer) is avoided. With such an electrode, the electrolyte on the surface of the metal parts to be protected can be raised to a positive potential compared to the metal parts to be protected. As a result, e.g. At defective areas of a coating, such as those that can arise, for example, from mechanical influences, in particular from the impact of scattered sand or the like, a direct current flows from the electrolyte into the metal surface, which counteracts the migration of positive metal ions from the metal surface and thus the so-called "cathodic" Corrosion Protection "causes.

Hierzu ist bekannt, daß für ein Wirksamwerden des kathodischen Korrosionsschutzes das potential des Elektrolyten in der Umgebung der zu schützenden Stelle, gemessen gegen eine Cu/CuS04-Elektrode um mindestens ca. 0,85 Volt positiver sein muß, als das Potential des zu schützenden Metalls.For this it is known that for the cathodic corrosion protection to take effect, the potential of the electrolyte in the vicinity of the point to be protected, measured against a Cu / CuS0 4 electrode, must be at least approximately 0.85 volt more positive than the potential of the point to be protected Metal.

Während diese Forderung für Metallteile, die von einem Elektrolyten mit großem elektrischen Strömungsquerschnitt umgeben sind (dies gilt insbesondere für erdverlegte Metallteile) relativ leicht erfüllbar ist, besteht bei Metallteilen, die nur mit einer dünnen elektrolytischen Schicht bedeckt sind, das Problem, daß das Potential infolge des geringen elektrischen Strömungsquerschnittes bzw. des dadurch bedingten hohen elektrischen Widerstandes des Elektrolyten mit der Entfernung zur Elektrode sehr rasch abnimmt und bereits in geringer Entfernung von der Elektrode den für ein Wirksamwerden des kathodischen Korrosionsschutzes erforderlichen Wert unterschreitet. Zwar könnte eine Vergrößerung des Wirkungsbereiches durch Erhöhung der Spannung der Elektrode ereicht werden, doch ist diese Maßnahme aus Gründen der elektrischen Beeinflussung sowie aus Sicherheitsgründen nur beschränkt durchführbar.While this requirement can be met relatively easily for metal parts which are surrounded by an electrolyte with a large electrical flow cross-section (this applies in particular to underground metal parts), there is the problem with metal parts which are only covered with a thin electrolytic layer that the potential arises as a result of the small electrical flow cross section or the resulting high electrical resistance of the electrolyte decreases very rapidly with the distance to the electrode and falls below the value required for the cathodic corrosion protection to become effective even at a short distance from the electrode. An increase in the effective range could be achieved by increasing the voltage of the electrode, but this measure can only be carried out to a limited extent for reasons of electrical interference and for safety reasons.

Es ist aus der DE-OS 27 36 693 eine Vorrichtung eingangs genannter Art bekannt, bei der die Elektrode, welche eine elektrisch leitende Verbindung zu der auf der zu schützenden Metalloberfläche befindlichen Elektrolytschicht herstellen soll, ein plattenartiges freiliegenden Gebilde ist, dessen Abmessungen im Vergleich zu den Abmessungen der zu schützenden Metalloberfläche klein sind. Es wird diese Elektrode mit einer Klammer in geringem Abstand über der Metalloberfläche festgehalten und kommt beim Nasswerden der Elektrolytschicht mit dieser in elektrisch leitende Verbindung. Durch die vergleichsweise geringe Flächengröße der Elektrode und durch die geringen Unterschiede zwischen Länge und Breite derselben, ergibt sich in Elektrodennähe eine hohe Stromdichte in der Elektrolytschicht; es muß, um in größerer Entfernung von der Elektrode noch eine Schutzwirkung zu erzielen, eine verhältnismäßig große Spannung angewendet werden und dies führt unter anderem dazu, daß in der näheren Umgebung der Elektrode säurebildende Bedingungen entstehen, was an sich dort korrosive Wirkungen herbeiführen kann.From DE-OS 27 36 693 a device of the type mentioned is known, in which the electrode, which is to produce an electrically conductive connection to the electrolyte layer located on the metal surface to be protected, is a plate-like exposed structure, the dimensions of which are compared to the dimensions of the metal surface to be protected are small. This electrode is held with a clamp at a short distance above the metal surface and comes into an electrically conductive connection when the electrolyte layer becomes wet. The comparatively small surface area of the electrode and the small differences between its length and width result in a high current density in the electrolyte layer in the vicinity of the electrode; in order to achieve a protective effect at a greater distance from the electrode, a relatively large voltage must be applied, and this leads, inter alia, to the formation of acid-forming conditions in the immediate vicinity of the electrode, which in itself can lead to corrosive effects there.

Die Elektrode dieser bekannten Vorrichtung ist metallisch, wobei vorzugsweise ein Material gewählt wird, das eine niedrige Verbrauchsgeschwindigkeit unter anodischen Bedingungen ergibt.The electrode of this known device is metallic, preferably a material is selected which gives a low consumption rate under anodic conditions.

Aus der US-PS 3 498 898 ist eine Korrosionsschutztechnik bekannt, bei der die zu schützenden Metalloberflächen mit einer ersten Lackschicht überzogen werden, auf die eine dünne Nickelschicht aufgebracht wird, auf welche dann weitere Lackschichten aufgebracht werden; der die zu schützende Metalloberfläche aufweisende Metallgegenstand einerseits und die Nickelschicht andererseits werden an die beiden pole einer Gleichstromquelle angeschlossen. Die Nikkeischicht bildet somit eine abgedeckte Elektrode. Wenn die elektrisch isolierenden Lackschichten verletzt werden, kann sich beim Vorliegen eines Elektrolyts an der Fehlerstelle eine kathodische oder eine anodische Schutzwirkung entwickeln. Da solche Verletzungen im allgemeinen eine geringe Größe haben, ergeben sich hinsichtlich des Erzielens eines Korrosionsschutzes außerhalb des beschichteteten Bereiches in vermehrtem Maß Schwierigkeiten, und es ist diese Technik im Hinblick auf die erforderliche mehrfache Beschichtung bei komplizierten Oberflächen mit mehreren Einzelteilen schwer anwendbar.A corrosion protection technique is known from US Pat. No. 3,498,898, in which the metal surfaces to be protected are coated with a first lacquer layer are coated, on which a thin nickel layer is applied, to which further layers of lacquer are then applied; the metal object to be protected on the one hand and the nickel layer on the other hand are connected to the two poles of a direct current source. The Nikkei layer thus forms a covered electrode. If the electrically insulating lacquer layers are damaged, a cathodic or anodic protective effect can develop when an electrolyte is present at the fault location. Since such injuries are generally small in size, there is increasing difficulty in providing corrosion protection outside of the coated area, and this technique is difficult to apply in view of the multiple coating required on complex multi-part surfaces.

Es ist ein Ziel der Erfindung, eine Vorrichtung eingangs genannter Art zu schaffen, mit der bei verhältnismäßig niedrigen Werten der angewendeten Spannung auch in größeren Entfernungen von der bzw. den Elektrode(n) eine gute Schutzwirkung erzielbar ist.It is an object of the invention to provide a device of the type mentioned at the outset, with which a good protective effect can be achieved at relatively low values of the applied voltage, even at greater distances from the electrode (s).

Die erfindungsgemäße Vorrichtung vorstehend genannter Art ist dadurch gekennzeichnet, daß die Elektrode als elektrisch leitfähige Leiste oder elektrisch leitfähiger flexibler Streifen oder als elektrisch leitfähige Beschichtung ausgebildet ist, welche(r) linienhaft und/oder flächenhaft über einen großen Teil der Abmessungen der zu schützenden Metalloberfläche reichend an dieser Metalloberfläche elektrisch isoliert anliegend angebracht ist. Es kann so der vorstehend angeführten Zielsetzung gut entsprochen werden. Es ergibt sich in der fallweise auftretenden Elektrolytschicht, über die die an der Metalloberfläche elektrisch isoliert anliegende Elektrode mit der zu schützenden Metalloberfläche elektrisch leitend in Verbindung kommt, auch in der Umgebung der Elektrode keine nachteilig erhöhte Stromdichte. über weite Bereiche reichend an der zu schützenden Metallfläche anliegend angebracht ist. Es kann so der vorstehend angeführten Zielsetzung gut entsprochen werden.The device according to the invention of the type mentioned above is characterized in that the electrode is designed as an electrically conductive strip or electrically conductive flexible strip or as an electrically conductive coating which extends linearly and / or over a large part of the dimensions of the metal surface to be protected attached to this metal surface in an electrically insulated manner. In this way, the objective stated above can be met well. There is no disadvantageously increased current density in the occasionally occurring electrolyte layer, via which the electrode, which is electrically insulated on the metal surface and electrically conductively connects to the metal surface to be protected, in the vicinity of the electrode. is attached to the metal surface to be protected, extending over wide areas. In this way, the objective stated above can be met well.

Im Rahmen der Erfindung sind weitere vorteilhafte Ausbildungen vorgesehen, deren Merkmale in den Unteransprüchen angeführt sind.Within the scope of the invention, further advantageous designs are provided, the features of which are set out in the subclaims.

Die Erfindung wird nun unter Bezugnahme auf Beispiele, welche in der Zeichnung schematisch dargestellt sind, weiter erläutert, wobei auch weitere Merkmale und Vorteile der Erfindung dargelegt werden.The invention will now be further explained with reference to examples, which are shown schematically in the drawing, further features and advantages of the invention also being set out.

In der Zeichnung zeigen:

  • Fig. 1 Strömungsfeld und Potentialverlauf, wie sie bei bisher eingesetzten Vorrichtungen auftreten,
  • Fig. 2 Strömungsfeld und Potentialverlauf bei einer erfindungsgemäß ausgebildeten Vorrichtung,
  • Fig. 3 ein Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung, und die
  • Figuren 4, 5 und 6 weitere Ausführungsbeispiele mit linienhaft ausgedehnter Elektrode, flächenhaft ausgedehnter Elektrode und räumlich ausgedehnter Elektrode.
The drawing shows:
  • 1 flow field and potential curve, as they occur in previously used devices,
  • 2 flow field and potential profile in a device designed according to the invention,
  • Fig. 3 shows an embodiment of a device according to the invention, and the
  • FIGS. 4, 5 and 6 further exemplary embodiments with a linearly extended electrode, a two-dimensionally extended electrode and a spatially extended electrode.

Die bei den bisher bekannten Vorrichtungen eingesetzten Elektroden sind so gestaltet, daß der kathodische Schutzstrom im wesentlichen zentral von den Elektroden ausgehend in den Elektrolyten eintritt und sich in diesem entlang im wesentlichen zentrisch verlaufender Stromlinien ausbreitet und dadurch in der Umgebung der Elektroden erhöhte Stromdichten und damit erhöhte Spannungabfälle auftreten. Es liegen also Verhältnisse vor, wie sie in Fig. 1 dargestellt sind, welche Strömungsfeld und Potentialverlauf in der Umgebung einer an einen ausgedehnten Flächenleiter angelegten, gegenüber dem Flächenleiter klein gehaltenen Elektrode A bei weit entfernten Gegenelektroden zeigt. Infolge der erhöhten Stromdichte in der Umgebung der Elektrode nimmt das Potential des Flächenleiters in der Umgebung der Elektrode A sehr rasch ab.The electrodes used in the previously known devices are designed in such a way that the cathodic protective current essentially enters the electrolyte centrally from the electrodes and spreads along it along essentially centric current lines, thereby increasing current densities in the vicinity of the electrodes and thus increasing them Voltage drops occur. There are therefore conditions, as shown in FIG. 1, which shows the flow field and potential course in the vicinity of an electrode A which is applied to an extended surface conductor and is kept small compared to the surface conductor with counter electrodes which are far away. As a result of the increased current density in the vicinity of the electrode, the potential of the surface conductor in the vicinity of electrode A decreases very quickly.

Bei der erfindungsgemäßen Vorrichtung wird das Auftreten erhöhter Stromdichten und damit erhöhter Spannungsabfälle vermieden und dadurch der Wirkungsbereich der Elektroden gegenüber herkömmlichen Elektroden wesentlich vergrößert. Es werden hiezu, wie z.B. die Fig 3 und 4 zeigen, Elektroden 1 eingesetzt, die in zumindest einer Richtung über weite Bereiche der zu schützenden Metalloberfläche linienhaft ausgedehnt sind, beispielsweise leitfähige Klebebänder oder leitfähige Zierleisten, sodaß sich der Strom, der aus ihnen austritt, wie Fig. 2 verdeutlicht, in der Umgebung der Elektroden entlang im wesentlichen parallel verlaufender Stromlinien im Elektrolyten ausbreitet und dadurch keine erhöhten Stromdichten und damit keine erhöhten Spannungsabfälle auftreten. Fig. 2 zeigt dabei Strömungsfeld und potentialverlauf in der Umgebung einer an einen ausgedehnten Flächenleiter angelegten, über einen weiten Bereich des Flächenleiters linienhaft ausgedehnten Elektrode 1, bei weit entfernten Gegenelektroden. In der Umgebung der Elektrode 1 (die Enden der Elektrode ausgenommen) tritt keine erhöhte Stromdichte und somit kein erhöhter Spannungsabfall auf.In the device according to the invention, the occurrence of increased current densities and thus increased voltage drops is avoided, and the range of action of the electrodes compared to conventional electrodes is thereby significantly increased. For this purpose, e.g. 3 and 4 show electrodes 1 used which are linearly extended in at least one direction over wide areas of the metal surface to be protected, for example conductive adhesive tapes or conductive decorative strips, so that the current which emerges from them is illustrated in FIG. 2, spreads in the vicinity of the electrodes along essentially parallel current lines in the electrolyte and, as a result, there are no increased current densities and therefore no increased voltage drops. 2 shows the flow field and the potential profile in the vicinity of an electrode 1 which is applied to an extended area conductor and extends linearly over a wide area of the area conductor, with counter electrodes being distant. In the vicinity of the electrode 1 (excluding the ends of the electrode) there is no increased current density and therefore no increased voltage drop.

In ähnlicher Weise werden in Fig. 5 Elektroden 9 eingesetzt, die über weite Bereiche der zu schützenden Metalloberfläche flächenhaft ausgedehnt sind, beispielsweise leitfähige Beschichtungen, insbesondere leitfähiger Unterbodenschutz oder leitfähiger Hohlraumschutz, oder gemäß Fig. 6 Elektroden 10, die räumlich ausgedehnt sind und die die zu schützenden Metallteile über weite Bereiche flächenhaft berühren, beispielsweise leitfähige Füllstoffe für Hohlräume der Fahrzeugkarosserie.Similarly, electrodes 9 are used in FIG. 5, which are extended over large areas of the metal surface to be protected, for example conductive coatings, in particular conductive underbody protection or conductive cavity protection, or according to FIG. 6 electrodes 10, which are spatially extended and which Touch metal parts to be protected over large areas, for example conductive fillers for cavities in the vehicle body.

Die erfindungsgemäße Vorrichtung weist mindestens eine Elektrode auf, die an der zu schützenden Metalloberfläche in Anlage gebracht, vorzugsweise angeklebt oder als Beschichtung aufgebracht oder in Hohlräume eingebracht werden kann. Die Elektrode ist so ausgebildet, daß sie an die zu schützende Metalloberfläche bzw. an eine auf der Metalloberfläche befindliche Beschich- tung (Lack) in zumindest einer Richtung über weite Bereiche ausgedehnt in Anlage gebracht werden kann. Es kommen linienhaft ausgedehnte Elektroden 1, oder flächenhaft ausgedehnte Elektroden 9 oder räumlich ausgedehnte Elektroden 10 in Frage. Die Vorrichtung weist weiter eine elektrische Anschlußleitung 4 auf, mit welcher die Elektrode an den positiven pol einer Spannungsquelle 2 angeschlossen werden kann.The device according to the invention has at least one electrode which can be brought into contact with the metal surface to be protected, preferably glued on or applied as a coating or introduced into cavities. The electrode is designed so that it is on the metal surface to be protected or on a coating (lacquer) on the metal surface can be brought into abutment in at least one direction over wide areas. Electrodes 1 that extend in a line, or electrodes 9 that extend in a flat area or electrodes 10 that are spatially extended are possible. The device also has an electrical connecting line 4, with which the electrode can be connected to the positive pole of a voltage source 2.

Die Elektrode ist vorzugsweise aus einem Material ausgeführt, welches an der Grenzfläche zum Elektrolyten 3 keine lonenleitfähigkeit aufweist, beispielsweise aus Graphit oder einem graphitierten Trägermaterial, beispielsweise graphitierter Gummi, sodaß sie durch den Strom nicht wie die bekannten sogenannten "Opferanoden" abgebaut werden, oder sie sind beispielsweise metallisch ausgeführt und von einem derartigen, nicht ionenleitfähigen Material umgeben.The electrode is preferably made of a material which has no ionic conductivity at the interface with the electrolyte 3, for example made of graphite or a graphitized carrier material, for example graphitized rubber, so that they are not degraded by the current like they are known or "sacrificial anodes" are, for example, metallic and surrounded by such a non-ion-conductive material.

Die Elektroden können vorzugsweise als flexible, leicht ablängbare Klebebänder ausgeführt sein, welche auf einfache Weise an der Oberfläche von Fahrzeugen angebracht werden können, wobei sie sich den Konturen des Fahrzeuges anpassen können und sich auf diese Weise über weite Bereiche der zu schützenden Metalloberfläche iinienhaft erstrecken können.The electrodes can preferably be designed as flexible, easily cut-to-length adhesive tapes, which can be attached to the surface of vehicles in a simple manner, whereby they can adapt to the contours of the vehicle and in this way can extend linearly over large areas of the metal surface to be protected .

Der elektrische Anschluß der Elektrode an den positiven Pol einer Spannungsquelle erfolgt, wie Fig. 3 zeigt, durch eine vorzugsweise isolierte Anschlußleitung 4, welche am einen Ende an den positiven Pol einer Spannungsquelle 2 anschließbar ist und am anderen Ende an die Elektrode anschließbar ist, wobei der Anschluß 5 an die Elektrode vorzugsweise über einen bereits beschriebenen Leiter erfolgt, welcher an der Grenzfläche zum Eletrolyten 3 keine lonenleitfähigkeit aufweist.The electrical connection of the electrode to the positive pole of a voltage source takes place, as shown in FIG. 3, by a preferably insulated connecting line 4, which can be connected at one end to the positive pole of a voltage source 2 and can be connected to the electrode at the other end, whereby the connection 5 to the electrode is preferably made via a conductor already described, which has no ionic conductivity at the interface with the electrolyte 3.

Die Vorrichtung ist gegebenenfalls mit einer an sich bekannten Strombegrenzungseinrichtung 6, vorzugsweise einem elektrischen Widerstand oder einer elektrischen Sicherung, gegebenenfalls mit einer an sich bekannten Spannungsbegrenzungseinrichtung 7, vorzugsweise einem Spannungsteiler, sowie gegebenenfalls mit einer an sich bekannten Betriebsanzeigeeinrichtung 8, vorzugsweise einer Kontrollampe, versehen.The device is optionally provided with a current limiting device 6 known per se, preferably an electrical resistor or an electrical fuse, optionally with a voltage limiting device 7 known per se, preferably a voltage divider, and optionally with an operating display device 8 known per se, preferably a control lamp.

Fig. 3 zeigt, wie eine erfindungsgemäße Vorrichtung an einer Fahrzeugkarosserie vorgesehen werden kann. Fig. 4 verdeutlicht die Anbringung einer linienhaft ausgedehnten Elektrode an einem Fahrzeugunterboden, und Fig. 5 verdeutlicht die Anbringung einer flächenhaft ausgedehnten Elektrode an einem Fahrzeugunterboden. Fig. 6 verdeutlicht die Anbringung einer räumlich ausgedehnten Elektrode 10 in einem Hohlraum einer Fahrzeugkarosserie, z.B. einem Einstiegsbalken 11, wobei die Elektrode 10 die Metallteile, die den Hohlraum begrenzen, großflächig berührt.3 shows how a device according to the invention can be provided on a vehicle body. FIG. 4 illustrates the attachment of a linearly extended electrode to a vehicle underbody, and FIG. 5 illustrates the attachment of an areally extended electrode to a vehicle underbody. Fig. 6 illustrates the placement of a spatially extended electrode 10 in a cavity of a vehicle body, e.g. an entry beam 11, the electrode 10 touching the metal parts that delimit the cavity over a large area.

Claims (18)

1. Device for the cathodic protection from corrosion of metal parts which are not laid in the ground e.g. metal parts of vehicles, wherein with the use of at least one exposed electrode electrically insulated from the metal parts to be protected and of at least one voltage source a potential difference is produced between the metal parts to be protected and an electrolyte which may be present on the metal part and with which the electrode comes into electrical contact, so that at regions of the metal surface which are to be protected a direct current passes from the electrolyte into the metal surface, counteracting the migration of positive metal ions from the metal surface, characterised in that the electrode (1, 9, 10) is constructed as an electrically conductive rail or electrically conductive flexible strip or an electrically conductive coating, which extends linearly and/or superficially over a considerable portion of the dimensions of the metal surface to be protected and is arranged in electrically insulated manner adjacent to this metal surface.
2. Device according to claim 1, characterised in that the electrode is made of a material which has no ion conductivity at the interface with the electrolyte, so that the electrode is not degraded by the direct current in the manner of a sacrificial anode.
3. Device according to claim 2, characterised in that the electrode is made of graphite or a graphitised carrier material, or is surrounded by such a material.
4. Device according to claim 3, characterised in that the electrode is made of graphitised rubber or is surrounded by graphitised rubber.
5. Device according to one of claims 2 to 4, characterised in that the electrical connection of the electrode to the positive pole of a voltage source (2) is made via a connecting line (4) which is connectable at one end to the positive pole of the voltage source and at the other end is connectable to the electrode, and the connection to the electrode may be made if appropriate via a connector (5) made of a material which has no ion conductivity at the interface to the electrolyte.
6. Device according to claim 1, characterised in that a current-limiting device (6) is provided in the circuit.
7. Device according to claim 6, characterised in that an electrical resistor or an electrical fuse is provided as the current-limiting device.
8. Device according to claim 1, characterised in that a voltage-limiting device (7) precedes the electrode.
9. Device according to claim 8, characterised in that a voltage divider is the voltage-limiting device.
10. Device according to claim 1, characterised in that the device has an operation-indicating device (8).
11. Device according to claim 10, characterised in that the operation-indicating device is a monitoring lamp.
12. Device according to claim 1, characterised in that the electrode (1) is constructed as a conductive adhesive tape.
13. Device according to claim 1, characterised in that the electrode (1, 9) is provided in the form of a conductive lacquer or as a conductive protective layer on the vehicle underside or as a conductive protective layer in hollow spaces.
14. Device according to claim 1, characterised in that the electrode (10) is provided in the form of a conductive filler material for hollow spaces.
15. Device according to claim 1, characterised in that the electrode is bendable or is bent-over, or bends-over elastically independently and is arranged on angular structures of the metal parts being protected.
16. Device according to claim 15, characterised in that the electrode is arranged on edges of the metal parts to be protected or on folded connection regions of the metal parts.
17. Device according to claim 15 or 16, characterised in that the electrode is adapted to be secured by means of clips on angular structures of the metal parts.
18. Device according to claim 1, characterised in that the electrode consists of an element which in the first instance serves predominantly other purposes, for example a protective fillet or a cladding of a metal part.
EP86904027A 1985-07-12 1986-07-14 Device for the cathodic protection of metal parts from corrosion Expired - Lifetime EP0229115B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT2063/85 1985-07-12
AT0206385A AT384626B (en) 1985-07-12 1985-07-12 DEVICE FOR APPLYING CATHODIC CORROSION PROTECTION TO NON-GROUND SYSTEMS

Publications (2)

Publication Number Publication Date
EP0229115A1 EP0229115A1 (en) 1987-07-22
EP0229115B1 true EP0229115B1 (en) 1990-11-28

Family

ID=3526986

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86904027A Expired - Lifetime EP0229115B1 (en) 1985-07-12 1986-07-14 Device for the cathodic protection of metal parts from corrosion

Country Status (7)

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US (1) US4798658A (en)
EP (1) EP0229115B1 (en)
JP (1) JPS63500312A (en)
AT (2) AT384626B (en)
CA (1) CA1298568C (en)
DE (1) DE3675912D1 (en)
WO (1) WO1987000558A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5167785A (en) * 1989-10-07 1992-12-01 Mccready David F Thin electrodes
DE10319607B3 (en) * 2003-05-02 2004-10-14 Saint-Gobain Sekurit Deutschland Gmbh & Co. Kg Corrosion protection circuit for conductor structure of automobile windscreen antenna using electrical passivation voltage as supply voltage for HF component
US8287285B2 (en) * 2010-10-22 2012-10-16 Johnson Controls Technology Company System and method for reducing electromagnetic interference from a conductive interior trim component
DE102017131188A1 (en) 2017-12-22 2019-06-27 KM Innopat GmbH Corrosion protection and corrosion protection monitoring
US20210230752A1 (en) * 2020-01-24 2021-07-29 Richard L. Klopp Corrosion Inhibitor Apparatus for Land Vehicles

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498898A (en) * 1967-07-25 1970-03-03 Ford Motor Co Method for providing corrosion protection for automobile bodies
BE779914R (en) * 1972-01-14 1972-06-16 Degeest Willy Cathodic protection for road vehicles - provides effective anti corrosive means for metal bodywork
US3957008A (en) * 1974-03-28 1976-05-18 Mccormick Michael E Drag reduction of water vehicles using gas created by electrolysis on electrodes attached to the hull
US4226694A (en) * 1976-08-16 1980-10-07 Texas Instruments Incorporated Cathodic protection system for a motor vehicle
DE3226146A1 (en) * 1982-07-13 1984-01-19 Lebar, Robert, Dipl.-Ing., 4100 Duisburg Corrosion protection
AT378207B (en) * 1983-10-25 1985-07-10 Padinger Reinhard ELECTRIC CORROSION PROTECTION DEVICE FOR VEHICLES
FR2555517B1 (en) * 1983-11-29 1988-04-08 Citroen Sa SLIDING GLASS VEHICLE DOOR

Also Published As

Publication number Publication date
WO1987000558A1 (en) 1987-01-29
ATA206385A (en) 1987-05-15
EP0229115A1 (en) 1987-07-22
DE3675912D1 (en) 1991-01-10
CA1298568C (en) 1992-04-07
AT384626B (en) 1987-12-10
ATE58758T1 (en) 1990-12-15
US4798658A (en) 1989-01-17
JPS63500312A (en) 1988-02-04

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