EP0187917B1 - Process for improving the protection against corrosion of resin layers autophoretically deposited on metal surfaces - Google Patents
Process for improving the protection against corrosion of resin layers autophoretically deposited on metal surfaces Download PDFInfo
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- EP0187917B1 EP0187917B1 EP85114639A EP85114639A EP0187917B1 EP 0187917 B1 EP0187917 B1 EP 0187917B1 EP 85114639 A EP85114639 A EP 85114639A EP 85114639 A EP85114639 A EP 85114639A EP 0187917 B1 EP0187917 B1 EP 0187917B1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
- B05D7/142—Auto-deposited coatings, i.e. autophoretic coatings
- B05D7/144—After-treatment of auto-deposited coatings
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- the invention relates to a method with which the corrosion protection can be significantly improved autophoretically on metal surfaces of resin layers compared to previously known methods.
- barium, strontium, zinc or lead compounds are used as corrosion protection pigments, the chromates of the metals mentioned being preferably used. Without exception, these chromates are poorly soluble in water.
- the inorganic pigments mentioned which are to ensure improved corrosion protection, directly to the coating bath.
- the autophoretic coating process is based on the fact that the acidic aqueous resin dispersion stains the metal surface to be coated and metal ions of the metal layer to be coated thereby dissolve. These positive charge carriers coagulate the stabilized resin dispersion in the vicinity of the metal surface, which causes a homogeneous coating of the metal surface with the organic resin. Due to the low pH value of this coating process (between 1.5 and 4.0), the corrosion protection pigments mentioned, which have only a low solubility in water, are more or less quickly converted into a soluble form.
- the object of the invention was to overcome the disadvantage of using such anti-corrosion pigments in autophoretic coating baths. Surprisingly, it was found that stable organic layers with excellent corrosion protection properties can be obtained on metal surfaces if the metal surfaces are immersed in an aqueous metal salt solution after the actual coating reaction before the organic resin film dries and the metal salts remaining in the organic film are subsequently dried Immersed in an aqueous, hexavalent and possibly also trivalent chromium-containing rinsing solution converted into chromates and then the chromate-containing coating of the metal surface dries and burns.
- metals such as aluminum, zinc, iron, nickel, tin, lead and chromium or their alloys can be used as metal surfaces for the process according to the invention. This also includes metal surfaces that are coated with one of the metals mentioned or one of their alloys.
- the metal surfaces mentioned are mechanically and / or chemically, e.g. by treatment with an alkaline cleaning solution, cleaned and thus prepared for the process step of autophoretic coating.
- the cleaned metal surfaces are autophoretically coated by treatment with an aqueous acidic dispersion of an organic resin.
- the organic resins that can be used for this coating step are generally known and commercially available.
- dispersions of styrene-butadiene copolymers, acrylic acid copolymers, acrylonitrile-butadiene copolymers, ethylene-vinyl acetate copolymers, polyethylene homopolymeric or other resins known from the prior art can be used.
- the metal surfaces autophoretically coated with an organic resin are rinsed with water before further treatment.
- the metal surfaces coated with an organic resin and not yet dried are then brought into contact with an aqueous solution of a readily water-soluble salt of a metal from the group of strontium, barium, lead, nickel, copper and zinc.
- a readily water-soluble salt of a metal from the group of strontium, barium, lead, nickel, copper and zinc.
- Lead or nickel salts are preferably used.
- the anions of the salts which can be used according to the invention are subject, on the one hand, to the requirement that salts with the respective metal cations be readily soluble in water. In addition, they must not belong to the group of those anions which in any way have a detrimental effect on the result of the process according to the invention.
- salts of hydrohalic acids or sulfuric acid are not suitable according to the invention, since the anions, for example CI and SO 4 2 , are known to have a corrosive effect on metal surfaces and their solutions therefore at least partially compensate for the purpose of improving corrosion protection on metal surfaces.
- Salts of the metals mentioned with anions of organic carboxylic acids have proven particularly useful for use in the process according to the invention.
- the ethanates (acetates), propanates (propionates) or salts of higher carboxylic acids or dicarboxylic acids can be used.
- the ethanates (acetates) of the metals mentioned are preferred, since when the deposited coating is baked in the presence of Cr (VI) ions it can be assumed that the anions decompose to C0 2 and H 2 0. These decomposition products do not negatively affect the corrosion protection of the metal surfaces.
- the content of metal salts in the aqueous solutions with which the autophoretically coated metal surfaces are treated according to the invention can vary within wide limits. It is between 1 and 10 g of metal ion per liter of application solution, preferably 2.5 to 7 g of metal ion per liter of application solution.
- the aqueous solutions When treating the metal surfaces, the aqueous solutions have a pH in the range from 4.5 to 8.5. If necessary, using the acid, the salt of which is used to improve corrosion protection, the pH can be lowered within the range mentioned. Solutions containing lead or nickel ethanate are adjusted to a pH in the range from 4.9 to 5.3 using ethanoic acid (acetic acid).
- the metal surfaces prepared as described above and coated with an organic resin are brought into contact with the salt solutions mentioned according to methods known per se. This can consist in immersing the coated metal plates in the metal salt solutions, spraying them with these solutions or treating them in combined immersion / spray processes.
- the treatment time is 30 to 120 sec, preferably 90 sec.
- the salt solutions have temperatures in the range from 4 to 50 ° C; treatment at 20 ° C. is preferred.
- the salts are in the still soft organic. African layer installed. However, they are accessible to further chemical reactions and are treated according to the invention in a subsequent step with an aqueous solution containing chromium, the respective organic metal salts being converted into the corresponding chromates.
- the aqueous solution required for the step of converting the water-soluble metal salts into the corresponding chromates contains water-soluble hexavalent chromium compounds.
- examples of such compounds are chromic acid, potassium dichromate, magnesium dichromate, potassium chromate and sodium chromate.
- any chromium-containing compound can be used which forms chromium (VI) ions in an acidic aqueous medium.
- Preferred sources of chromium (VI) are dichromates, for example calcium dichromate.
- Such solutions can also be prepared by mixing aqueous chromic acid solutions with appropriate salts, e.g. Calcium carbonate, added.
- Solutions that contain trivalent chromium in addition to hexavalent are preferred. Such solutions can be produced according to the prior art by partially reducing Cr (VI) -containing solutions with suitable reducing agents. A known possibility is e.g. in adding formaldehyde to chromic acid solutions and thereby reducing some of the Cr (VI) to Cr (III).
- the molar ratio of Cr (III) to Cr (VI) in the solutions mentioned is in the range from 0.3 to 3: 1.
- the solutions contain a total of 1 to 20 g of chromium per liter of application solution, preferably 5 to 15 g of chromium per liter of application solution.
- the conversion of the metal salts introduced into the organic resin layer in the first process step into the corresponding chromates also takes place according to methods known from the prior art.
- the metal surfaces can either be immersed in the chromium-containing aqueous solutions or sprayed with them, or they can also be treated by combined immersion / spray processes.
- the treatment time is in the range from 30 to 120, preferably 90 seconds, at temperatures from 4 to 50 ° C., preferably 20 ° C.
- Metal autophoretically coated with an organic resin and additionally protected against corrosion with a metal chromate Surfaces are then dried in a manner known per se, elevated temperatures of from 90 to 150 ° C., preferably of 110 ° C., being used where appropriate. The temperature used in each case depends on the organic resin used for the coating. A completely closed organic resin surface is formed which, due to its metal chromate content, protects the metal surface against corrosion much better than non-post-treated or only post-treated metal surfaces with chromic acid.
- test sheets were immersed in the metal salt solution for 90 seconds at 20 ° C. - see Table 1 - and then for 90 seconds at 20 ° C. in a solution containing 6.15 g / l Chromium (III) and 10.9 g / I chromium (VI) contained, rinsed. Then the test panels were 30 min. dried at 110 ° C in the oven.
- the corrosion protection according to DIN 5316 and VW test specification No. 3.17.1 from January 6th, 1981 was tested on the test sheets produced in this way.
- the test panels were loaded for 240 hours and 480 hours, respectively, and assessed after a recovery time of 1 hour.
- the test sheets were shot with steel shot, the salt spray test was carried out in accordance with DIN 50021, the test sheets were shot again with steel shot after a rest period of 1 hour, and the number and size of the breakthroughs were evaluated.
- Table 2 contains the assessment of the test panels.
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Abstract
Description
Die Erfindung betrifft ein Verfahren, mit dem der Korrosionsschutz autophoretisch auf Metalloberflächen abgeschiedener Harzschichten im Vergleich mit bisher bekannten Verfahren deutlich verbessert werden kann.The invention relates to a method with which the corrosion protection can be significantly improved autophoretically on metal surfaces of resin layers compared to previously known methods.
Der verbessernde Einfluss anorganischer Pigmente auf den Korrosionsschutz autophoretisch abgeschiedener organischer Beschichtungen auf verschiedenen Metalloberflächen ist seit langer Zeit bekannt. So wird in der US-PS 4 030 945 vorgeschlagen, mit organischen Harzen autophoretisch beschichtete Metalloberflächen im Anschluss an die eigentliche Beschichtungsreaktion mit verdünnten wässrigen Lösungen zu spülen, die sechswertiges Chrom allein oder sechswertiges Chrom neben reduzierten Chrom-Verbindungen enthalten. Für die Spüllösungen werden wasserlösliche, sechswertiges Chrom enthaltende Verbindungen, z.B. Chromsäure, Kaliumdichromat, Magnesiumdichromat, Kaliumchromat oder Natriumchromat eingesetzt, wobei auch der Einsatz wässriger Lösungen von Chromsäure zusammen mit wasserlöslichen Salzen der jeweiligen Metalle möglich ist. Das Spülen von mit organischen Schichten überzogenen Metalloberflächen mit derartigen Lösungen wird auch in der US-PS 4 186 226 beschrieben. wobei als Quelle für Chrom in den Lösungen bevorzugt Natriumdichromat verwendet wird.The improving influence of inorganic pigments on the corrosion protection of autophoretically deposited organic coatings on various metal surfaces has been known for a long time. It is proposed in US Pat. No. 4,030,945 to rinse metal surfaces autophoretically coated with organic resins after the actual coating reaction with dilute aqueous solutions which contain hexavalent chromium alone or hexavalent chromium in addition to reduced chromium compounds. Water-soluble compounds containing hexavalent chromium, e.g. Chromic acid, potassium dichromate, magnesium dichromate, potassium chromate or sodium chromate are used, it also being possible to use aqueous solutions of chromic acid together with water-soluble salts of the respective metals. The rinsing of metal surfaces coated with organic layers with such solutions is also described in US Pat. No. 4,186,226. sodium dichromate is preferably used as the source of chromium in the solutions.
In weiteren bekannten Verfahren zur Verbesserung des Korrosionsschutzes autophoretisch beschichteter Metalloberflächen werden als Korrosionsschutzpigmente Barium-, Strontium-, Zink-oder Bleiverbindungen eingesetzt, wobei man bevorzugt die Chromate der genannten Metalle verwendet. Diese Chromate sind ausnahmslos schlecht in Wasser löslich.In other known processes for improving the corrosion protection of autophoretically coated metal surfaces, barium, strontium, zinc or lead compounds are used as corrosion protection pigments, the chromates of the metals mentioned being preferably used. Without exception, these chromates are poorly soluble in water.
Grundsätzlich ist es jedoch möglich, die genannten anorganischen Pigmente, die für einen verbesserten Korrosionsschutz Sorge tragen sollen, unmittelbar in das Beschichtungsbad zu geben. Das autophoretische Beschichtungsverfahren basiert, wie aus zahlreichen Publikationen bekannt ist, darauf, dass die saure wässrige Harzdispersion die zu beschichtende Metalloberfläche anbeizt und dabei Metallionen der zu beschichtenden Metallschicht in Lösung gehen. Diese positiven Ladungsträger koagulieren die stabilisierte Harzdispersion in der Nähe der Metalloberfläche, wodurch eine homogene Beschichtung der Metalloberfläche mit dem organischen Harz bewirkt wird. Durch den niedrigen pH-Wert dieses Beschichtungsverfahrens (zwischen 1,5 und 4,0) werden auch die genannten Korrosionsschutzpigmente, die in Wasser nur eine geringe Löslichkeit aufweisen, mehr oder weniger schnell in eine lösliche Form umgewandelt. Sie können zwar in dieser Form gleichzeitig mit den organischen Harzteilchen abgeschieden werden, tragen aber andererseits in unerwünschter Weise zu einer vermehrten Koagulation der Harzdispersion bei, die unter Umständen sogar zu einem Zusammenbruch der stabilen Harzdispersion durch vollständige Koagulation führt.In principle, however, it is possible to add the inorganic pigments mentioned, which are to ensure improved corrosion protection, directly to the coating bath. As is known from numerous publications, the autophoretic coating process is based on the fact that the acidic aqueous resin dispersion stains the metal surface to be coated and metal ions of the metal layer to be coated thereby dissolve. These positive charge carriers coagulate the stabilized resin dispersion in the vicinity of the metal surface, which causes a homogeneous coating of the metal surface with the organic resin. Due to the low pH value of this coating process (between 1.5 and 4.0), the corrosion protection pigments mentioned, which have only a low solubility in water, are more or less quickly converted into a soluble form. Although they can be deposited in this form at the same time as the organic resin particles, on the other hand they undesirably contribute to an increased coagulation of the resin dispersion, which under certain circumstances even leads to a breakdown of the stable resin dispersion by complete coagulation.
Die Erfindung stellte sich die Aufgabe, den Nachteil der Anwendung derartiger Korrosionsschutzpigmente in autophoretischen Beschichtungsbädern zu überwinden. Es wurde nämlich überraschenderweise gefunden, dass stabile organische Schichten mit ausgezeichneten Korrosionsschutz-Eigenschaften auf Metalloberflächen erhalten werden können, wenn man die Metalloberflächen nach der eigentlichen Beschichtungsreaktion vor einem Trocknen des organischen Harzfilms in eine wässrige Metallsalzlösung taucht und die in dem organischen Film verbliebenen Metallsalze durch anschliessendes Tauchen in eine wässrige, sechswertiges und gegebenenfalls auch dreiwertiges Chrom enthaltende Spüllösung in Chromate überführt und anschliessend die Chromate enthaltende Beschichtung der Metalloberfläche trocknet und einbrennt.The object of the invention was to overcome the disadvantage of using such anti-corrosion pigments in autophoretic coating baths. Surprisingly, it was found that stable organic layers with excellent corrosion protection properties can be obtained on metal surfaces if the metal surfaces are immersed in an aqueous metal salt solution after the actual coating reaction before the organic resin film dries and the metal salts remaining in the organic film are subsequently dried Immersed in an aqueous, hexavalent and possibly also trivalent chromium-containing rinsing solution converted into chromates and then the chromate-containing coating of the metal surface dries and burns.
Gegenstand der Erfindung ist somit ein Verfahren zur Verbesserung des Korrosionsschutzes autophoretisch abgeschiedener Harzschichten auf Metalloberflächen, bei dem man die nach an sich bekannten Methoden gereinigten, mit einem beliebigen organischen Harz autophoretisch beschichteten und gegebenenfalls mit Wasser gespülten Metalloberflächen
- a) mit einer wässrigen Lösung eines gut in Wasser löslichen Salzes eines Metalles aus der Gruppe Strontium, Barium, Blei, Nickel, Kupfer und Zink bei einem pH-Wert im Bereich von 4,5 bis 8,5 in Kontakt bringt,
- b) die in dem organischen Film verbleibenden Metallsalze durch Behandlung mit einer sechswertiges und gegebenenfalls auch dreiwertiges Chrom enthaltenden wässrigen Lösung in Chromate überführt und
- c) die Metallchromate enthaltende organische Schicht in an sich bekannter Weise trocknet und/ oder bei erhöhter Temperatur einbrennt.
- a) in contact with an aqueous solution of a readily water-soluble salt of a metal from the group of strontium, barium, lead, nickel, copper and zinc at a pH in the range from 4.5 to 8.5,
- b) converting the metal salts remaining in the organic film into chromates by treatment with an aqueous solution containing hexavalent and optionally also trivalent chromium and
- c) drying the organic layer containing metal chromates in a manner known per se and / or baking at elevated temperature.
Als Metalloberflächen können für das erfindungsgemässe Verfahren Oberflächen von Metallen wie Aluminium, Zink, Eisen, Nickel, Zinn, Blei und Chrom oder deren Legierungen verwendet werden. Darunter fallen auch Metalloberflächen die mit einem der genannten Metalle oder einer ihrer Legierungen überzogen sind.Surfaces of metals such as aluminum, zinc, iron, nickel, tin, lead and chromium or their alloys can be used as metal surfaces for the process according to the invention. This also includes metal surfaces that are coated with one of the metals mentioned or one of their alloys.
Die genannten Metalloberflächen werden nach an sich bekannten Methoden mechanisch und/ oder chemisch, z.B. durch Behandlung mit einer alkalischen Reinigerlösung, gereinigt und damit für den Verfahrensschritt des autophoretischen Beschichtens vorbereitet.The metal surfaces mentioned are mechanically and / or chemically, e.g. by treatment with an alkaline cleaning solution, cleaned and thus prepared for the process step of autophoretic coating.
Nachfolgend werden die gereinigten Metalloberflächen durch Behandlung mit einer wässrigen sauren Dispersion eines organischen Harzes autophoretisch beschichtet. Die für diesen Beschichtungsschritt verwendbaren organischen Harze sind allgemein bekannt und im Handel erhältlich. So sind beispielsweise Dispersionen von Styrol-Butadien-Copolymeren, Acrylsäurecopolymeren, Acrylnitril-Butadien-Copolymeren, Ethylen-Vinylacetat-Copolymeren, Polyethylenhomopolymeren oder anderer aus dem Stand der Technik bekannter Harze verwendbar.Subsequently, the cleaned metal surfaces are autophoretically coated by treatment with an aqueous acidic dispersion of an organic resin. The organic resins that can be used for this coating step are generally known and commercially available. For example, dispersions of styrene-butadiene copolymers, acrylic acid copolymers, acrylonitrile-butadiene copolymers, ethylene-vinyl acetate copolymers, polyethylene homopolymeric or other resins known from the prior art can be used.
Gegebenenfalls werden die mit einem organischen Harz autophoretisch beschichteten Metalloberflächen vor der Weiterbehandlung mit Wassergespült.If necessary, the metal surfaces autophoretically coated with an organic resin are rinsed with water before further treatment.
Erfindungsgemäss werden nun die mit einem organischen Harz beschichteten und noch nicht getrockneten Metalloberflächen mit einer wässrigen Lösung eines gut in Wasser löslichen Salzes eines Metalles aus der Gruppe Strontium, Barium, Blei, Nickel, Kupfer und Zink in Kontakt gebracht. Bevorzugt werden Blei- oder Nickelsalze verwendet.According to the invention, the metal surfaces coated with an organic resin and not yet dried are then brought into contact with an aqueous solution of a readily water-soluble salt of a metal from the group of strontium, barium, lead, nickel, copper and zinc. Lead or nickel salts are preferably used.
Die Anionen der erfindungsgemäss verwendbaren Salze unterliegen einerseits der Forderung, mit den jeweiligen Metallkationen gut in Wasser lösliche Salze zu bilden. Sie dürfen zudem nicht zur Gruppe derjenigen Anionen gehören, die in irgendeiner Weise schädlich auf das Ergebnis des erfindungsgemässen Verfahrens einwirken. Beispielsweise sind Salze der Halogenwasserstoffsäuren oder der Schwefelsäure erfindungsgemäss nicht geeignet, da die Anionen, z.B. CI- und SO4 2- bekanntermassen korrosiv auf Metalloberflächen wirken, und ihre Lösungen daher den Zweck, den Korrosionsschutz auf Metalloberflächen zu verbessern, zumindest zum Teil kompensieren.The anions of the salts which can be used according to the invention are subject, on the one hand, to the requirement that salts with the respective metal cations be readily soluble in water. In addition, they must not belong to the group of those anions which in any way have a detrimental effect on the result of the process according to the invention. For example, salts of hydrohalic acids or sulfuric acid are not suitable according to the invention, since the anions, for example CI and SO 4 2 , are known to have a corrosive effect on metal surfaces and their solutions therefore at least partially compensate for the purpose of improving corrosion protection on metal surfaces.
Zur Verwendung in dem erfindungsgemässen Verfahren haben sich Salze der genannten Metalle mit Anionen organischer Carbonsäuren besonders bewährt. Es können beispielsweise die Ethanate (Acetate), Propanate (Propionate) oder auch Salze höherer Carbonsäuren oder Dicarbonsäuren verwendet werden. Bevorzugt werden die Ethanate (Acetate) der genannten Metalle, da beim Einbrennen des abgeschiedenen Überzugs in Gegenwart von Cr(VI)-lonen davon ausgegangen werden kann, dass sich die Anionen zu C02 und H20 zersetzen. Diese Zersetzungsprodukte beeinflussen den Korrosionsschutz der Metalloberflächen nicht negativ.Salts of the metals mentioned with anions of organic carboxylic acids have proven particularly useful for use in the process according to the invention. For example, the ethanates (acetates), propanates (propionates) or salts of higher carboxylic acids or dicarboxylic acids can be used. The ethanates (acetates) of the metals mentioned are preferred, since when the deposited coating is baked in the presence of Cr (VI) ions it can be assumed that the anions decompose to C0 2 and H 2 0. These decomposition products do not negatively affect the corrosion protection of the metal surfaces.
Der Gehalt an Metallsalzen in den wässrigen Lösungen, mit denen erfindungsgemäss die autophoretisch beschichteten Metalloberflächen behandelt werden, kann in weiten Grenzen schwanken. Er liegt zwischen 1 und 10 g Metallion pro Liter Anwendungslösung, bevorzugt bei 2,5 bis 7 g Metallion pro Liter Anwendungslösung.The content of metal salts in the aqueous solutions with which the autophoretically coated metal surfaces are treated according to the invention can vary within wide limits. It is between 1 and 10 g of metal ion per liter of application solution, preferably 2.5 to 7 g of metal ion per liter of application solution.
Die wässrigen Lösungen weisen bei der Behandlung der Metalloberflächen einen pH-Wert im Bereich von 4,5 bis 8,5 auf. Gegebenenfalls kann unter Verwendung der Säure, deren Salz zur Verbesserung des Korrosionsschutzes eingesetzt wird, der pH-Wert innerhalb des genannten Bereiches erniedrigt werden. So werden Blei- oder Nickelethanat enthaltende Lösungen mit Ethansäure (Essigsäure) auf einen pH-Wert im Bereich von 4,9 bis 5,3 eingestellt.When treating the metal surfaces, the aqueous solutions have a pH in the range from 4.5 to 8.5. If necessary, using the acid, the salt of which is used to improve corrosion protection, the pH can be lowered within the range mentioned. Solutions containing lead or nickel ethanate are adjusted to a pH in the range from 4.9 to 5.3 using ethanoic acid (acetic acid).
Die wie oben beschrieben vorbereiteten und mit einem organischen Harz beschichteten Metalloberflächen werden nach an sich bekannten Methoden mit den genannten Salzlösungen in Kontakt gebracht. Dies kann darin bestehen, dass die beschichteten Metallplatten in die Metallsalzlösungen eingetaucht, mit diesen Lösungen besprüht oder auch in kombinierten Tauch-/Sprüh-Verfahren behandelt werden. Die Behandlungszeit liegt bei 30 bis 120 sec, bevorzugt bei 90 sec. Die Salzlösungen haben dabei Temperaturen im Bereich von 4 bis 50 °C; bevorzugt wird eine Behandlung bei 20 °C.The metal surfaces prepared as described above and coated with an organic resin are brought into contact with the salt solutions mentioned according to methods known per se. This can consist in immersing the coated metal plates in the metal salt solutions, spraying them with these solutions or treating them in combined immersion / spray processes. The treatment time is 30 to 120 sec, preferably 90 sec. The salt solutions have temperatures in the range from 4 to 50 ° C; treatment at 20 ° C. is preferred.
Im Verlauf der Behandlung der beschichteten Metalloberfläche mit einer wässrigen Metallsalzlösung werden die Salze in die noch weiche orga- . nische Schicht eingebaut. Sie sind jedoch weiteren chemischen Reaktionen zugänglich und werden erfindungsgemäss in einem nachfolgenden Schritt mit einer Chrom enthaltenden wässrigen Lösung behandelt, wobei die jeweiligen organischen Metallsalze in die entsprechenden Chromate überführt werden.In the course of the treatment of the coated metal surface with an aqueous metal salt solution, the salts are in the still soft organic. African layer installed. However, they are accessible to further chemical reactions and are treated according to the invention in a subsequent step with an aqueous solution containing chromium, the respective organic metal salts being converted into the corresponding chromates.
Die für den Schritt der Überführung der wasserlöslichen Metallsalze in die entsprechenden Chromate benötigte wässrige Lösung enthält wasserlösliche sechswertige Chromverbindungen. Beispiele solcher Verbindungen sind Chromsäure, Kaliumdichromat, Magensiumdichromat, Kaliumchromat und Natriumchromat. Grundsätzlich kann jede Chrom enthaltende Verbindung verwendet werden, die in saurem wässrigem Medium Chrom(VI)-lonen bildet. Bevorzugte Quellen von Chrom(VI) sind Dichromate, beispielsweise Calciumdichromat. Derartige Lösungen können ebenfalls dadurch hergestellt werden, dass man wässrige Chromsäure-Lösungen mit entsprechenden Salzen, z.B. Calciumcarbonat, versetzt.The aqueous solution required for the step of converting the water-soluble metal salts into the corresponding chromates contains water-soluble hexavalent chromium compounds. Examples of such compounds are chromic acid, potassium dichromate, magnesium dichromate, potassium chromate and sodium chromate. In principle, any chromium-containing compound can be used which forms chromium (VI) ions in an acidic aqueous medium. Preferred sources of chromium (VI) are dichromates, for example calcium dichromate. Such solutions can also be prepared by mixing aqueous chromic acid solutions with appropriate salts, e.g. Calcium carbonate, added.
Es werden bevorzugt Lösungen verwendet, die neben sechswertigem auch dreiwertiges Chrom enthalten. Derartige Lösungen können nach dem Stand der Technik dadurch hergestellt werden, dass man Cr(VI) enthaltende Lösungen mit geeigneten Reduktionsmitteln partiell reduziert. Eine bekannte Möglichkeit besteht z.B. darin, Chromsäure-Lösungen mit Formaldehyd zu versetzen und dadurch einen Teil des Cr(VI) zu Cr(III) zu reduzieren.Solutions that contain trivalent chromium in addition to hexavalent are preferred. Such solutions can be produced according to the prior art by partially reducing Cr (VI) -containing solutions with suitable reducing agents. A known possibility is e.g. in adding formaldehyde to chromic acid solutions and thereby reducing some of the Cr (VI) to Cr (III).
Das molare Verhältnis von Cr(llI) zu Cr (VI) in den genannten Lösungen liegt dabei im Bereich von 0,3 bis 3:1. Die Lösungen enthalten insgesamt 1 bis 20 g Chrom pro Liter Anwendungslösung, bevorzugt 5 bis 15 g Chrom pro Liter Anwendungslösung.The molar ratio of Cr (III) to Cr (VI) in the solutions mentioned is in the range from 0.3 to 3: 1. The solutions contain a total of 1 to 20 g of chromium per liter of application solution, preferably 5 to 15 g of chromium per liter of application solution.
Die Umwandlung der im ersten Verfahrensschritt in die organische Harzschicht eingebrachten Metallsalze in die entsprechenden Chromate geschieht ebenfalls nach aus dem Stand der Technik bekannten Methoden. Die Metalloberflächen können entweder in die Chrom enthaltenden wässrigen Lösungen eingetaucht oder mit ihnen besprüht oder auch nach kombinierten Tauch-/Sprüh-Verfahren behandelt werden. Die Behandlungszeit liegt im Bereich von 30 bis 120, bevorzugt bei 90 sec, bei Temperaturen von 4 bis 50 °C, bevorzugt bei 20 °C.The conversion of the metal salts introduced into the organic resin layer in the first process step into the corresponding chromates also takes place according to methods known from the prior art. The metal surfaces can either be immersed in the chromium-containing aqueous solutions or sprayed with them, or they can also be treated by combined immersion / spray processes. The treatment time is in the range from 30 to 120, preferably 90 seconds, at temperatures from 4 to 50 ° C., preferably 20 ° C.
Derart mit einem organischen Harz autophoretisch beschichtete und mit einem Metallchromat gegen Korrosion zusätzlich geschützte Metalloberflächen werden anschliessend in an sich bekannter Weise getrocknet, wobei gegebenenfalls erhöhte Temperaturen von 90 bis 150 °C, bevorzugt von 110 °C angewendet werden. Die jeweils eingesetzte Temperatur ist dabei von dem für die Beschichtung verwendeten organischen Harz abhängig. Es wird dabei eine vollständig geschlossene organische Harzoberfläche gebildet, die aufgrund ihres Metallchromat-Gehaltes die Metalloberfläche deutlich besser gegen Korrosion schützt als nicht nachbehandelte oder nur mit Chromsäure nachbehandelte autophoretisch beschichtete Metalloberflächen.Metal autophoretically coated with an organic resin and additionally protected against corrosion with a metal chromate Surfaces are then dried in a manner known per se, elevated temperatures of from 90 to 150 ° C., preferably of 110 ° C., being used where appropriate. The temperature used in each case depends on the organic resin used for the coating. A completely closed organic resin surface is formed which, due to its metal chromate content, protects the metal surface against corrosion much better than non-post-treated or only post-treated metal surfaces with chromic acid.
Die Erfindung wird durch die nachstehenden Beispiele näher erläutert.The invention is illustrated by the examples below.
Allgemeine Arbeitsvorschrift:General working instructions:
Prüfbleche aus Stahl-Werkstoff Nr. 1.1405 (nach DIN; unlegierter Stahl, kaltgewalzt Tiefziehqualität; dieser Werkstoff wird als Karosserieblech in der Automobilindustrie eingesetzt) wurden in einem Beschichtungsbad folgender Zusammensetzung während 90 sec bei 20 ± 2 °C beschichtet:
- 18,2 Gew.-% einer anionisch stabilisierten Harzdispersion mit 33% Bindemittel;
- 5,0 Gew.-% einer sauren wässrigen Eisen(III)-fluoridlösung ;
- 76,8 Gew.-% vollentsalztes Wasser.
- 18.2% by weight of an anionically stabilized resin dispersion with 33% binder;
- 5.0% by weight of an acidic aqueous ferric fluoride solution;
- 76.8% by weight of demineralized water.
Nach dem anschliessenden Spülen während 30 bis 60 sec in Wasser wurden die Prüfbleche während 90 sec bei 20°C in die Metallsalzlösung-siehe Tabelle 1 - getaucht und anschliessend 90 sec lang bei 20 °C in einer Lösung, welche 6,15 g/I Chrom(III) und 10,9 g/I Chrom(VI) enthielt, gespült. Danach wurden die Prüfbleche 30 min. bei 110 °C im Ofen getrocknet.
Erläuterungen:
- a) pH 6,3, mit Ethansäure eingestellt auf 4,9
- b) pH 7,8, mit Ethansäure eingestellt auf 5,3
- a) pH 6.3, adjusted to 4.9 with ethanoic acid
- b) pH 7.8, adjusted to 5.3 with ethanoic acid
An den so hergestellten Prüfblechen wurde der Korrosionsschutz gemäss DIN 5316 und VW-Prüfvorschrift Nr. 3.17.1 vom 06.01.1981 (Steinschlag-Salzsprühtest) geprüft. Die Prüfbleche wurden 240 Std. bzw. 480 Std. belastet und nach 1 Std. Erholungszeit beurteilt.The corrosion protection according to DIN 5316 and VW test specification No. 3.17.1 from January 6th, 1981 (stone chip salt spray test) was tested on the test sheets produced in this way. The test panels were loaded for 240 hours and 480 hours, respectively, and assessed after a recovery time of 1 hour.
Beim Salzsprühtest gemäss DIN 53167 wurde die Unterwanderung (in mm) an der Ritzspur bewertet.In the salt spray test according to DIN 53167, the infiltration (in mm) was evaluated on the scratch mark.
Bei der VW-Prüfvorschrift wurden die Testbleche mit Stahlschrot beschossen, der Salzsprühtest gemäss DIN 50021 durchgeführt, die Testbleche nach 1 Std. Ruhezeit erneut mit Stahlschrot beschossen und die Anzahl und Grösse der entstandenen Durchschläge bewertet. Die Bewertung reichte von K 1 = 2% beschädigter Fläche bis K 10 = 90% beschädigter Fläche.In the VW test specification, the test sheets were shot with steel shot, the salt spray test was carried out in accordance with DIN 50021, the test sheets were shot again with steel shot after a rest period of 1 hour, and the number and size of the breakthroughs were evaluated. The rating ranged from K 1 = 2% damaged area to K 10 = 90% damaged area.
In Tabelle 2 ist die Beurteilung der Prüfbleche enthalten.
Claims (14)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT85114639T ATE39502T1 (en) | 1985-01-09 | 1985-11-18 | METHOD OF IMPROVING THE CORROSION PROTECTION OF AUTOPHORETIC RESIN COATINGS ON METAL SURFACES. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE3500443 | 1985-01-09 | ||
DE19853500443 DE3500443A1 (en) | 1985-01-09 | 1985-01-09 | METHOD FOR IMPROVING THE CORROSION PROTECTION OF AUTOPHORETICALLY DEPOSIT RESIN LAYERS ON METAL SURFACES |
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EP0187917A1 EP0187917A1 (en) | 1986-07-23 |
EP0187917B1 true EP0187917B1 (en) | 1988-12-28 |
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EP85114639A Expired EP0187917B1 (en) | 1985-01-09 | 1985-11-18 | Process for improving the protection against corrosion of resin layers autophoretically deposited on metal surfaces |
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US (1) | US4636264A (en) |
EP (1) | EP0187917B1 (en) |
JP (1) | JPS61174973A (en) |
CN (1) | CN1008527B (en) |
AT (1) | ATE39502T1 (en) |
BR (1) | BR8600052A (en) |
CA (1) | CA1245918A (en) |
DE (2) | DE3500443A1 (en) |
Families Citing this family (24)
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DE3442985A1 (en) * | 1984-11-26 | 1986-05-28 | Henkel KGaA, 4000 Düsseldorf | METHOD FOR IMPROVING THE CORROSION PROTECTION OF AUTOPHORETICALLY SEPARATED RESIN COATINGS ON METAL SURFACES |
IT1229206B (en) * | 1988-03-30 | 1991-07-25 | Nihon Parkerizing | METHOD TO FORM A BLACK COLOR COATING ON THE MATERIAL SURFACE. |
FR2685352A1 (en) * | 1991-12-24 | 1993-06-25 | Pont A Mousson | MULTILAYER COATING, WITH ITS OBTAINING METHOD AND APPLICATION |
US5441773A (en) * | 1992-01-21 | 1995-08-15 | Betz Laboratories, Inc. | Composition and method of forming a black no-rinse conversion coating on metal surfaces |
US5470613A (en) * | 1992-01-21 | 1995-11-28 | Betz Laboratories, Inc. | Composition and method of forming a black no-rinse conversion coating on metal surfaces |
US5385758A (en) * | 1992-12-30 | 1995-01-31 | Henkel Corporation | Method for applying autodeposition coating |
US5372853A (en) * | 1993-08-05 | 1994-12-13 | Henkel Corporation | Treatment to improve corrosion resistance of autodeposited coatings of metallic surfaces |
US5667845A (en) * | 1993-08-05 | 1997-09-16 | Henkel Corporation | Treatment to improve corrosion resistance of autodeposited coatings on metallic surfaces |
JP3515183B2 (en) * | 1994-08-30 | 2004-04-05 | 臼井国際産業株式会社 | Corrosion resistant resin coating structure on metal tube |
US5704995A (en) * | 1996-07-16 | 1998-01-06 | Globe Motors, A Division Of Labinal Components And Systems, Inc. | Method for forming a black, adherent coating on a metal substrate |
US5786030A (en) * | 1996-11-12 | 1998-07-28 | Henkel Corporation | Spotting resistant gloss enhancement of autodeposition coating |
US6410092B1 (en) * | 1999-05-21 | 2002-06-25 | Henkel Corporation | Autodeposition post-bath rinse process |
BR0010956A (en) * | 1999-05-26 | 2002-05-28 | Henkel Corp | Metal substrate, composite, process to produce an aqueous dispersion suitable for use in forming a self-deposited surface coating, and aqueous emulsion |
AU2001243166A1 (en) * | 2000-02-18 | 2001-08-27 | Penguinradio, Inc. | Internet wired audio device |
TW570842B (en) | 2000-11-22 | 2004-01-11 | Nihon Parkerizing | Protective reaction rinse for autodeposition coatings |
US6989411B2 (en) * | 2001-11-14 | 2006-01-24 | Henkel Kommanditgesellschaft Auf Aktien (Henkel Kgaa) | Epoxy dispersions for use in coatings |
BR0312495A (en) * | 2002-07-15 | 2005-05-10 | Henkel Kgaa | Process for making a self-depositing epoxy based dispersion, stable self-depositing epoxy dispersion, and self-depositing coating composition |
US7388044B2 (en) * | 2002-07-15 | 2008-06-17 | Henkel Kommanditgesellschaft Auf Aktien | Coatings with enhanced water-barrier and anti-corrosive properties |
DE102009029334A1 (en) * | 2009-09-10 | 2011-03-24 | Henkel Ag & Co. Kgaa | Two-stage process for the corrosion-protective treatment of metal surfaces |
BR112013015319A2 (en) | 2010-12-20 | 2017-07-04 | Henkel Ag & Co Kgaa | improved glossy-looking self-depositing coating, and methods of applying the same |
US9228109B2 (en) | 2010-12-20 | 2016-01-05 | Henkel Ag & Co. Kgaa | Glossy improved appearance auto-deposition coating, and methods of applying same |
CN103608393B (en) | 2011-06-17 | 2016-08-17 | 汉高股份有限及两合公司 | The mono bath autodeposition coatings of metal base and preparation and application thereof for combination |
US9115442B2 (en) | 2013-03-15 | 2015-08-25 | Henkel Ag & Co. Kgaa | Electrodeposition of an autodepositable polymer |
WO2017117169A1 (en) | 2015-12-31 | 2017-07-06 | Henkel Ag & Co. Kgaa | Low bake autodeposition coatings |
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Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4030945A (en) * | 1966-06-01 | 1977-06-21 | Amchem Products, Inc. | Rinsing coated metallic surfaces |
US3791431A (en) * | 1966-06-01 | 1974-02-12 | Amchem Prod | Process for coating metals |
US3647567A (en) * | 1969-11-28 | 1972-03-07 | Celanese Coatings Co | Post-dipping of acidic deposition coatings |
CA1089155A (en) * | 1975-08-29 | 1980-11-11 | Wilbur S. Hall | Treating autodeposited coatings with cr composition |
US4186219A (en) * | 1975-08-29 | 1980-01-29 | Union Carbide Corporation | Maintaining the effectiveness of a coating composition |
US4186226A (en) * | 1978-06-21 | 1980-01-29 | Union Carbide Corporation | Autodeposited coatings with increased surface slip |
US4411865A (en) * | 1979-04-05 | 1983-10-25 | Betz Laboratories, Inc. | Method of corrosion inhibition in aqueous mediums |
US4414350A (en) * | 1979-09-27 | 1983-11-08 | Amchem Products, Inc. | Ferrous complexing agent for autodeposition |
-
1985
- 1985-01-09 DE DE19853500443 patent/DE3500443A1/en not_active Withdrawn
- 1985-11-18 AT AT85114639T patent/ATE39502T1/en not_active IP Right Cessation
- 1985-11-18 DE DE8585114639T patent/DE3567035D1/en not_active Expired
- 1985-11-18 EP EP85114639A patent/EP0187917B1/en not_active Expired
- 1985-11-26 CA CA000496169A patent/CA1245918A/en not_active Expired
- 1985-11-26 US US06/802,635 patent/US4636264A/en not_active Expired - Fee Related
-
1986
- 1986-01-04 CN CN86100013A patent/CN1008527B/en not_active Expired
- 1986-01-08 BR BR8600052A patent/BR8600052A/en unknown
- 1986-01-09 JP JP61003375A patent/JPS61174973A/en active Pending
Also Published As
Publication number | Publication date |
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CN86100013A (en) | 1986-07-09 |
US4636264A (en) | 1987-01-13 |
DE3500443A1 (en) | 1986-09-11 |
CA1245918A (en) | 1988-12-06 |
BR8600052A (en) | 1986-09-23 |
JPS61174973A (en) | 1986-08-06 |
EP0187917A1 (en) | 1986-07-23 |
DE3567035D1 (en) | 1989-02-02 |
CN1008527B (en) | 1990-06-27 |
ATE39502T1 (en) | 1989-01-15 |
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