EP0078866B1 - Formation of coatings on aluminium surfaces - Google Patents

Formation of coatings on aluminium surfaces Download PDF

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Publication number
EP0078866B1
EP0078866B1 EP81201255A EP81201255A EP0078866B1 EP 0078866 B1 EP0078866 B1 EP 0078866B1 EP 81201255 A EP81201255 A EP 81201255A EP 81201255 A EP81201255 A EP 81201255A EP 0078866 B1 EP0078866 B1 EP 0078866B1
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Prior art keywords
contact
brought
process according
solution
solution containing
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German (de)
French (fr)
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EP0078866A1 (en
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Nobuyuki Oda
Haruyoshi Terada
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Nihon Parkerizing Co Ltd
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Nihon Parkerizing Co Ltd
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Priority to JP55062539A priority Critical patent/JPS5839232B2/en
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Priority to EP81201255A priority patent/EP0078866B1/en
Priority to DE8181201255T priority patent/DE3172781D1/en
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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
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
    • C23C22/08—Orthophosphates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
    • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
    • C23C22/361—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing titanium, zirconium or hafnium compounds

Definitions

  • the invention relates to a process for the formation of coatings on surfaces of aluminum or aluminum alloys by means of aqueous acidic solutions which contain phosphate ions, at least one di-bis-hexaphosphoric acid ester of inosite or alkali or alkaline earth metal salts thereof and at least one titanium and / or zirconium compound.
  • Chromating solutions have so far gained the greatest importance as coating solutions.
  • due to the environmental impact and toxicity to the human body the use of chromates is increasingly associated with certain requirements.
  • a disadvantage associated with the use of chromates is that considerable expenditure is required for wastewater treatment.
  • the phosphating solutions based on alkali metal phosphate, zinc phosphate or manganese phosphate which are customary for producing phosphate layers have problems with regard to the stability of the phosphating solution and the machinability of the coating.
  • Anodized coatings have excellent properties, but relatively high costs for equipment and processing are required.
  • Another type of process consists in treating metal surfaces, especially aluminum, with an aqueous solution which contains phytic acid (inositol hexaphosphoric acid) and zirconium salts or di-bis-hexaphosphoric acid esters of myoinositol or its salts and titanium fluorides (US Pat. No. 3,076,734, JA- OS 25233/79).
  • phytic acid inositol hexaphosphoric acid
  • zirconium salts or di-bis-hexaphosphoric acid esters of myoinositol or its salts and titanium fluorides US Pat. No. 3,076,734, JA- OS 25233/79.
  • the object of the invention is to provide a process which avoids the disadvantages of the known processes, in particular leads to coatings which are good with regard to moisture resistance and paint adhesion, is simple to use and is not associated with higher costs than the known processes.
  • the object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that the surfaces are brought into contact with a solution which has a pH of 2 to 6 and an additional content of at least one pyrazole of the formula where X, Y and Z are identical or different functional groups, such as hydrogen, hydroxyl, alkyl, acyl, amino or nitro groups.
  • the solutions to be used to carry out the method according to the invention have considerable stability and lead to coatings of low porosity and good gloss properties.
  • the mixed organic / inorganic coatings obtained impart excellent paint adhesion and are themselves and in connection with a subsequent painting of high corrosion resistance.
  • the phosphate ions can be introduced via phosphoric acid or phosphates, such as alkali or ammonium phosphates.
  • the surfaces are preferably brought into contact with a solution which contains 0.1 to 20 g / l of phosphate ions.
  • a further advantageous embodiment of the invention consists in bringing the surface into contact with a solution which contains 0.05 to 10 g / 1 pyrazole compound. If the concentration is less than 0.05 g / l, the corrosion resistance of the coating decreases, possibly due to insufficient complex formation between titanium and / or zirconium and the pyrazole compound, and the stability of the coating solution is reduced. A concentration higher than 10 g / I is practically not associated with any further increase in corrosion resistance and is therefore not very economical.
  • Particularly suitable pyrazole compounds are 3,5-dimethylpyrazole, 3-methyl-5-hydroxypyrazole and 3-methyl-4-amino-5-hydroxypyrazole.
  • Another preferred embodiment of the invention consists in bringing the metal surface into contact with a solution containing 0.05 to 10 g / l of di-bis-hexaphosphoric ester of the inositol or whose salts contain.
  • esters are essentially obtained by hydrolysis of the hexaphosphoric ester of inositol (phytic acid).
  • Phytic acid is a substance commonly found in cereals, is obtained on an industrial scale and is therefore most suitable for carrying out the process according to the invention. Like its salt (phytin), phytic acid is harmless.
  • the salts of the 2- to 6-fold phosphoric acid ester of inositol are usually the sodium, potassium, lithium, magnesium, calcium, strontium and barium salts. They are water-soluble and therefore particularly suitable for the process according to the invention.
  • concentrations of the esters or the salts to be used it should be taken into account that, at contents below 0.05 g / l, the corrosion resistance of the coating obtained decreases, and in particular the resistance to discoloration in boiling water also decreases.
  • the coating solution can also become unstable.
  • a concentration higher than 10 g / l leads to practically no improvement in the corrosion resistance or the other advantages of the coating obtained.
  • Titanium hydrofluoric acid H 2 TiF 6
  • Suitable zirconium compounds are e.g. B. zirconium hydrofluoric acid (H 2 ZrF 6 ) and its alkali metal salts, the ammonium salt, zirconium sulfate, zirconyl sulfate, zirconium hydroxide and zirconium oxalate.
  • hydrofluoric acid In order to easily detach these titanium or zirconium compounds, it is advisable to use hydrofluoric acid.
  • boron fluorides such as borofluorohydric acid or water-soluble salts thereof.
  • a suitable salt of borofluoric acid is e.g. B. ammonium borofluoride.
  • the addition of the boron fluoride accelerates the formation of the coating.
  • An additional preferred embodiment of the invention consists in bringing the surfaces into contact with a solution which additionally contains sulfate and / or fluoride ions.
  • the sulfate ions can be introduced using sulfuric acid, sodium sulfate, ammonium sulfate. Sulphate ions suppress corrosion during coating formation. They also give the coating even better gloss properties.
  • the fluoride addition serves in particular to stabilize aluminum that has gone into solution.
  • Suitable cleaning agents are e.g. B. organic solvents such as trichlorethylene, or alkaline or acidic aqueous degreasing agents.
  • the surfaces to be treated can be brought into contact with the coating solutions in any way. Suitable forms of application are spraying, dipping, flooding and rolling up.
  • the duration of the application of the solution to the workpieces varies depending on the type of aluminum surface or the nature of the alloy or the shape of the workpiece, etc.
  • the treatment time is generally between 1 sec. And 10 minutes.
  • the workpiece is then rinsed with water in the usual way and finally dried with hot air at 50 to 200 ° C. It is also possible to omit the water rinse and to dry the coating solution directly.
  • the coating solution can be applied at normal temperature. However, it is particularly advantageous if, according to a further embodiment of the invention, the surface is brought into contact with a solution heated to 40 to 90 ° C. This further improves corrosion resistance, adhesive strength and adhesion for a well-applied varnish.
  • the pH range of the coating solution used is between 2 and 6 in order to achieve a coating with excellent tightness and corrosion resistance with very good adhesive properties. If the pH value exceeds 6, insoluble titanium hydroxide and / or zirconium hydroxide are formed in the coating solution. If the pH is below 2, there is a strong pickling attack on the metal to be treated and a coating with very good corrosion resistance is practically impossible to achieve.
  • the pH can be adjusted with alkaline substances, e.g. B. caustic alkali, such as caustic soda, with ammonia water, sodium carbonate, and optionally acids, such as phosphoric acid, hydrofluoric acid, sulfuric acid.
  • the coating solutions used in the process according to the invention contain - as explained above - no toxic metals, such as. As chrome and the like., And cause little or practically no sewage or sludge problems.
  • the solution is stable. Thankss to its contact with the surface of aluminum or aluminum alloys, an organic-inorganic complex coating containing titanium / aluminum phosphate and / or zircon / aluminum phosphate is formed, which, even after the workpiece has been deformed, has a high salt water spray and moisture resistance as well as color stability in boiling Has water and in high temperature steam.
  • Aluminum plates (A 5052) measuring 0.4 x 70 x 150 mm were cleaned with an aqueous 1.5% alkaline degreasing agent, for 7 seconds with a coating solution which contained and had a pH of 4.0 and a temperature of 60 ° C, sprayed, then rinsed with tap water and finally with deionized water. Drying was carried out in a hot air oven at 200 ° C within 2 minutes.
  • Aluminum plates (A 5082) with the dimensions 0.4 x 70 x 150 mm were cleaned as in Example 1 and for 10 seconds with a coating solution which contained and had a pH of 4.5 and a temperature of 65 ° C, sprayed. The coating was then rinsed with water, again with deionized water, and dried in a hot air oven at 200 ° C for 2 minutes.
  • Plates treated in this way were subjected to the pasteurization test, i. H. Exposed to high pressure steam in a pressure vessel at 125 ° C for 30 minutes and checked for a color change on its surface.
  • the test results were subjected to the same evaluation procedure as the cooking water test of Example 1.
  • treated plates were coated with a commercially available epoxy paint for hollow vessels (XJ-K 190 A) for 3 to 4 J.Lm, baked for 8 minutes at 205 ° C, 1 hour in a boiling aqueous solution of 3% citric acid and 3% table salt dipped and at up to 80 ° C dried. Then, with a sharp knife, crosses were scratched into the paint surface down to the metal surface, cellophane adhesive strips were pressed on firmly, these were torn off violently and the detachment of the paint layer was checked.
  • the adhesive strength of the paint layer was evaluated in accordance with:
  • Example 2 A comparison test was carried out, which was carried out under the conditions of Example 1.
  • the coating was formed using a solution that contained a pH of 3.8 and a temperature of 40 ° C.
  • the coating quality was assessed by boiling water test, salt spray test and moisture test. The results were as follows:

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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Description

Die Erfindung betrifft ein Verfahren zur Ausbildung von Überzügen auf Oberflächen von Aluminium oder Aluminiumlegierungen mittels wässriger saurer Lösungen, die Phosphationen, mindestens einen Di-bis-Hexaphosphorsäureester des Inosits bzw. Alkali- oder Erdalkalisalze hiervon sowie mindestens eine Titan- und/oder Zirkonverbindung enthalten.The invention relates to a process for the formation of coatings on surfaces of aluminum or aluminum alloys by means of aqueous acidic solutions which contain phosphate ions, at least one di-bis-hexaphosphoric acid ester of inosite or alkali or alkaline earth metal salts thereof and at least one titanium and / or zirconium compound.

Als Maßnahmen zur Behandlung der Oberfläche von Erzeugnissen aus Aluminium oder Aluminiumlegierungen, z. B. von Hohlgefäßen, wie abstrecktiefgezogenen Hohlgefäßen, Deckeln, Metallzungen oder plattenförmigem Material zur Verwendung an Bauten, in Automobilen oder Elektrogeräten zum Zwecke der Verbesserung der Korrosionsbeständigkeit und der Haftfähigkeit von Farbschichten ist insbesondere die Erzeugung von Chromat-, Phosphat- sowie Eloxalschichten bekannt.As measures to treat the surface of products made of aluminum or aluminum alloys, e.g. B. hollow vessels, such as deep-drawn hollow vessels, lids, metal tongues or plate-shaped material for use in buildings, in automobiles or electrical appliances for the purpose of improving the corrosion resistance and the adhesiveness of layers of paint, in particular the generation of chromate, phosphate and anodized layers is known.

Als Überzugslösungen haben bisher Chromatierungslösungen die größte Bedeutung erlangt. Wegen der Umweltbelastung und der Toxizität für den menschlichen Körper wird jedoch der Gebrauch von Chromaten mehr und mehr mit bestimmten Auflagen verbunden. Ein mit der Verwendung von Chromaten verbundener Nachteil ist schließlich, daß erhebliche Aufwendungen für die Abwasserreinigung erforderlich sind.Chromating solutions have so far gained the greatest importance as coating solutions. However, due to the environmental impact and toxicity to the human body, the use of chromates is increasingly associated with certain requirements. Finally, a disadvantage associated with the use of chromates is that considerable expenditure is required for wastewater treatment.

Die zur Erzeugung von Phosphatschichten üblichen Phosphatierungslösungen auf Basis Alkaliphosphat, Zinkphosphat oder Manganphosphat besitzen Probleme hinsichtlich Stabilität der Phosphatierungslösung und Bearbeitbarkeit des Überzuges.The phosphating solutions based on alkali metal phosphate, zinc phosphate or manganese phosphate which are customary for producing phosphate layers have problems with regard to the stability of the phosphating solution and the machinability of the coating.

Eloxalschichten bringen zwar hervorragende Eigenschaften, jedoch sind verhältnismäßig hohe Aufwendungen für Ausrüstung und Verarbeitung erforderlich.Anodized coatings have excellent properties, but relatively high costs for equipment and processing are required.

Eine weitere Verfahrensart besteht darin, Metalloberflächen, speziell Aluminium, mit einer wässrigen Lösung zu behandeln, die Phytinsäure (Inositolhexaphosphorsäure) und Zirkonsalze bzw. Di-bis-Hexaphosphorsäureester des Myoinositols oder dessen Salze und Titanfluoride enthält (US-PS 3 076 734, JA-OS 25233/79). Die so gewonnenen Überzüge sind zwar von guter Haftfestigkeit der nachfolgend aufgebrachten Lackschicht, jedoch von schlechter Feuchtigkeitsbeständigkeit, wenn auf eine anschließende Lackierung verzichtet wird.Another type of process consists in treating metal surfaces, especially aluminum, with an aqueous solution which contains phytic acid (inositol hexaphosphoric acid) and zirconium salts or di-bis-hexaphosphoric acid esters of myoinositol or its salts and titanium fluorides (US Pat. No. 3,076,734, JA- OS 25233/79). Although the coatings obtained in this way have good adhesive strength in the subsequently applied lacquer layer, they are poor in moisture resistance if subsequent lacquering is dispensed with.

Aufgabe der Erfindung ist es, ein Verfahren bereitzustellen, das die Nachteile der bekannten Verfahren vermeidet, insbesondere zu hinsichtlich Feuchtigkeitsbeständigkeit und Lackhaftung guten Überzügen führt, einfach anwendbar ist und nicht mit höheren Kosten als die bekannten Verfahren verbunden ist.The object of the invention is to provide a process which avoids the disadvantages of the known processes, in particular leads to coatings which are good with regard to moisture resistance and paint adhesion, is simple to use and is not associated with higher costs than the known processes.

Die Aufgabe wird gelöst, indem das Verfahren der eingangs genannten Art entsprechend der Erfindung derart ausgestaltet wird, daß man die Oberflächen mit einer Lösung in Berührung bringt, die einen pH-Wert von 2 bis 6 und einen zusätzlichen Gehalt mindestens eines Pyrazols der Formel

Figure imgb0001
wobei X, Y und Z gleiche oder verschiedene funktionelle Gruppen, wie Wasserstoff, Hydroxy-, Alkyl-, Acyl-, Amino- oder Nitrogruppen sind, aufweist.The object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that the surfaces are brought into contact with a solution which has a pH of 2 to 6 and an additional content of at least one pyrazole of the formula
Figure imgb0001
 where X, Y and Z are identical or different functional groups, such as hydrogen, hydroxyl, alkyl, acyl, amino or nitro groups.

Die zur Durchführung des erfindungsgemäßen Verfahrens einzusetzenden Lösungen weisen eine beträchtliche Stabilität auf, führen zu Überzügen von geringer Porosität und guten Glanzeigenschaften. Die erhaltenen gemischt organisch/anorganischen Überzüge vermitteln eine hervorragende Lackhaftung und sind selbst sowie in Verbindung mit einer nachfolgenden Lackierung von hoher Korrosionsbeständigkeit.The solutions to be used to carry out the method according to the invention have considerable stability and lead to coatings of low porosity and good gloss properties. The mixed organic / inorganic coatings obtained impart excellent paint adhesion and are themselves and in connection with a subsequent painting of high corrosion resistance.

Die Phosphationen können über Phosphorsäure oder Phosphate, wie Alkali- oder Ammonphosphate, eingebracht werden. Vorzugsweise bringt man die Oberflächen mit einer Lösung in Berührung, die 0,1 bis 20 g/I Phosphationen enthält.The phosphate ions can be introduced via phosphoric acid or phosphates, such as alkali or ammonium phosphates. The surfaces are preferably brought into contact with a solution which contains 0.1 to 20 g / l of phosphate ions.

Eine weitere vorteilhafte Ausgestaltung der Erfindung besteht darin, die Oberfläche mit einer Lösung in Berührung zu bringen, die 0,05 bis 10 g/1 Pyrazolverbindung enthält. Ist die Konzentration geringer als 0,05 g/I sinkt die Korrosionsbeständigkeit des Überzuges gegebenenfalls infolge unzureichender Komplexbildung zwischen Titan und/oder Zirkon und der Pyrazolverbindung und die Stabilität der Überzugslösung wird geringer. Eine höhere Konzentration als 10 g/I ist praktisch mit keiner weiteren Erhöhung der Korrosionsbeständigkeit verbunden und somit wenig wirtschaftlich. Besonders geeignete Pyrazolverbindungen sind 3,5 Dimethylpyrazol, 3-Methyl-5-hydroxypyrazol und 3-Methyl-4-amino-5-hydroxypyrazol.A further advantageous embodiment of the invention consists in bringing the surface into contact with a solution which contains 0.05 to 10 g / 1 pyrazole compound. If the concentration is less than 0.05 g / l, the corrosion resistance of the coating decreases, possibly due to insufficient complex formation between titanium and / or zirconium and the pyrazole compound, and the stability of the coating solution is reduced. A concentration higher than 10 g / I is practically not associated with any further increase in corrosion resistance and is therefore not very economical. Particularly suitable pyrazole compounds are 3,5-dimethylpyrazole, 3-methyl-5-hydroxypyrazole and 3-methyl-4-amino-5-hydroxypyrazole.

Eine andere bevorzugte Ausgestaltung der Erfindung besteht darin, die Metalloberfläche mit einer Lösung in Berührung zubringen, die 0,05 bis 10 g/I Di-bis-Hexaphosphorsäureester des Inosit bzw. dessen Salze enthält. Diese Ester werden im wesentlichen durch Hydrolyse des Hexaphosphorsäureesters des Inosit (der Phytinsäure) gewonnen. Phytinsäure ist ein in den Getreidearten verbreitet vorhandener Stoff, wird großtechnisch gewonnen und ist daher zur Durchführung des erfindungsgemäßen Verfahrens am geeignetsten. Phytinsäure ist wie ihr Salz (das Phytin) unschädlich.Another preferred embodiment of the invention consists in bringing the metal surface into contact with a solution containing 0.05 to 10 g / l of di-bis-hexaphosphoric ester of the inositol or whose salts contain. These esters are essentially obtained by hydrolysis of the hexaphosphoric ester of inositol (phytic acid). Phytic acid is a substance commonly found in cereals, is obtained on an industrial scale and is therefore most suitable for carrying out the process according to the invention. Like its salt (phytin), phytic acid is harmless.

Als Salze des 2- bis 6-fachen Phosphorsäureesters von Inosit werden üblicherweise die Natrium-, Kalium-, Lithium-, Magnesium-, Calcium-, Strontium- und Bariumsalze eingesetzt. Sie sind wasserlöslich und daher für das erfindungsgemäße Verfahren besonders geeignet. Hinsichtlich der anzuwendenden Konzentrationen der Ester bzw. der Salze ist zu berücksichtigen, daß bei Gehalten unter 0,05 g/I die Korrosionsbeständigkeit des erhaltenen Überzuges sinkt, insbesondere auch die Verfärbungsbeständigkeit in kochendem Wasser nachläßt. Auch kann die Überzugslösung instabil werden. Eine höhere Konzentration als 10 g/I führt praktisch zu keiner Verbesserung der Korrosionsbeständigkeit bzw. der sonstigen Vorzüge des erhaltenen Überzuges.The salts of the 2- to 6-fold phosphoric acid ester of inositol are usually the sodium, potassium, lithium, magnesium, calcium, strontium and barium salts. They are water-soluble and therefore particularly suitable for the process according to the invention. With regard to the concentrations of the esters or the salts to be used, it should be taken into account that, at contents below 0.05 g / l, the corrosion resistance of the coating obtained decreases, and in particular the resistance to discoloration in boiling water also decreases. The coating solution can also become unstable. A concentration higher than 10 g / l leads to practically no improvement in the corrosion resistance or the other advantages of the coating obtained.

Als Titanverbindungen können beispielsweise Titanfluorwasserstoffsäure (H2TiF6), deren Alkalisalze, das Ammonsalz, Titansulfat, Titanylsulfat, Titanhydroxid und/oder Titanoxalat eingesetzt werden. Geeignete Zirkonverbindungen sind z. B. Zirkonfluorwasserstoffsäure (H2ZrF6) und deren Alkalisalze, das Ammonsalz, Zirkonsulfat, Zirkonylsulfat, Zirkonhydroxyd und Zirkonoxalat. Um diese Titan- oder Zirkonverbindungen einfach zu lösen, ist es zweckmäßig, Flußsäure zu verwenden.Titanium hydrofluoric acid (H 2 TiF 6 ), its alkali metal salts, the ammonium salt, titanium sulfate, titanium sulfate, titanium hydroxide and / or titanium oxalate can be used as titanium compounds. Suitable zirconium compounds are e.g. B. zirconium hydrofluoric acid (H 2 ZrF 6 ) and its alkali metal salts, the ammonium salt, zirconium sulfate, zirconyl sulfate, zirconium hydroxide and zirconium oxalate. In order to easily detach these titanium or zirconium compounds, it is advisable to use hydrofluoric acid.

Es empfiehlt sich, die Metalloberfläche mit einer Lösung in Berührung zu bringen, die 0,005 bis 10 g/I Titan- und/oder Zirkonverbindung (ber. als Titan- bzw. Zirkonmetall) enthält. Bei weniger als 0,005 g/l verschlechtert sich die Korrosionsbeständigkeit. Eine höhere Konzentration als 10 g/I ist mit keiner nennenswerten Verbesserung der Korrosionsbeständigkeit und der sonstigen Eigenschaften des Überzuges verbunden.It is advisable to bring the metal surface into contact with a solution containing 0.005 to 10 g / l titanium and / or zirconium compound (calculated as titanium or zirconium metal). At less than 0.005 g / l, the corrosion resistance deteriorates. A concentration higher than 10 g / l is not associated with any significant improvement in the corrosion resistance and the other properties of the coating.

Weiterhin ist es vorteilhaft, die Oberflächen mit einer Lösung in Berührung zu bringen, die zusätzlich Borfluoride, wie Borfluorwasserstoffsäure bzw. wasserlösliche Salze hiervon enthält. Ein geeignetes Salz der Borfluorwasserstoffsäure ist z. B. Ammoniumborfluorid. Durch den Zusatz der Borfluoride wird die Bildung des Überzuges beschleunigt.It is also advantageous to bring the surfaces into contact with a solution which additionally contains boron fluorides, such as borofluorohydric acid or water-soluble salts thereof. A suitable salt of borofluoric acid is e.g. B. ammonium borofluoride. The addition of the boron fluoride accelerates the formation of the coating.

Eine zusätzliche vorzugsweise Ausgestaltung der Erfindung besteht darin, die Oberflächen mit einer Lösung in Berührung zu bringen, die zusätzlich Sulfat- und/oder Fluoridionen enthält. Die Einbringung der Sulfationen kann mittels Schwefelsäure, Natriumsulfat, Ammoniumsulfat erfolgen. Sulfationen unterdrücken die Korrosion während der Überzugsbildung. Außerdem verleihen sie dem Überzug noch bessere Glanzeigenschaften. Die Fluoridzugabe dient insbesondere dazu, in Lösung gegangenes Aluminium zu stabilisieren.An additional preferred embodiment of the invention consists in bringing the surfaces into contact with a solution which additionally contains sulfate and / or fluoride ions. The sulfate ions can be introduced using sulfuric acid, sodium sulfate, ammonium sulfate. Sulphate ions suppress corrosion during coating formation. They also give the coating even better gloss properties. The fluoride addition serves in particular to stabilize aluminum that has gone into solution.

Vor der Behandlung mit der Überzugslösung sind die Oberflächen wie üblich zu reinigen. Geeignete Reinigungsmittel sind z. B. organische Lösungsmittel, wie Trichloräthylen, oder alkalische oder saure wässrige Entfettungsmittel.Before treatment with the coating solution, the surfaces should be cleaned as usual. Suitable cleaning agents are e.g. B. organic solvents such as trichlorethylene, or alkaline or acidic aqueous degreasing agents.

Die zu behandelnden Oberflächen können in beliebiger Weise mit den Überzugslösungen in Berührung gebracht werden. Geeignete Applikationsformen sind Spritzen, Tauchen, Fluten und Aufrollen. Die Dauer des Lösungsauftrages auf die Werkstücke ist je nach Art der Aluminiumoberfläche bzw. der Beschaffenheit der Legierung bzw. der Form des Werkstückes usw. verschieden. Im allgemeinen liegt die Behandlungsdauer zwischen 1 sec. und 10 Minuten. Anschließend wird das Werkstück in üblicher Weise mit Wasser gespült und schließlich mit Heißluft von 50 bis 200 °C getrocknet. Es ist auch möglich, die Wasserspülung fortzulassen und die Überzugslösung direkt aufzutrocknen.The surfaces to be treated can be brought into contact with the coating solutions in any way. Suitable forms of application are spraying, dipping, flooding and rolling up. The duration of the application of the solution to the workpieces varies depending on the type of aluminum surface or the nature of the alloy or the shape of the workpiece, etc. The treatment time is generally between 1 sec. And 10 minutes. The workpiece is then rinsed with water in the usual way and finally dried with hot air at 50 to 200 ° C. It is also possible to omit the water rinse and to dry the coating solution directly.

Die Überzugslösung kann bei Normaltemperatur aufgebracht werden. Besonders vorteilhaft ist es jedoch, wenn gemäß einer weiteren Ausgestaltung der Erfindung die Oberfläche mit einer auf 40 bis 90°C erwärmten Lösung in Berührung gebracht wird. Hierdurch werden Korrosionsbeständigkeit, Haftfestigkeit und Haftvermittlung für einen naohfoIgend aufgebrachten Lack noch verbessert.The coating solution can be applied at normal temperature. However, it is particularly advantageous if, according to a further embodiment of the invention, the surface is brought into contact with a solution heated to 40 to 90 ° C. This further improves corrosion resistance, adhesive strength and adhesion for a well-applied varnish.

Der pH-Bereich der zum Einsatz kommenden Überzugslösung liegt für die Erzielung eines Überzuges von hervorragender Dichtigkeit und Korrosionsbeständigkeit bei sehr guten Hafteigenschaften zwischen 2 und 6. Geht der pH-Wert über 6 hinaus, so entstehen in der Überzugslösung unlösliches Titanhydroxyd und/oder Zirkonhydroxyd. Liegt der pH-Wert unterhalb 2, so erfolgt ein starker Beizangriff auf das zu behandelnde Metall und ein Überzug von sehr guter Korrosionsbeständigkeit ist praktisch nicht zu erzielen. Der pH-Wert kann mit alkalisch reagierenden Substanzen, z. B. Ätzalkali, wie Ätznatron, mit Ammoniakwasser, Natriumkarbonat, und gegebenenfalls Säuren, wie Phosphorsäure, Flußsäure, Schwefelsäure, eingestellt werden.The pH range of the coating solution used is between 2 and 6 in order to achieve a coating with excellent tightness and corrosion resistance with very good adhesive properties. If the pH value exceeds 6, insoluble titanium hydroxide and / or zirconium hydroxide are formed in the coating solution. If the pH is below 2, there is a strong pickling attack on the metal to be treated and a coating with very good corrosion resistance is practically impossible to achieve. The pH can be adjusted with alkaline substances, e.g. B. caustic alkali, such as caustic soda, with ammonia water, sodium carbonate, and optionally acids, such as phosphoric acid, hydrofluoric acid, sulfuric acid.

Die innerhalb des erfindungsgemäßen Verfahrens zum Einsatz kommenden Überzugslösungen enthalten - wie oben erläutert - keine toxischen Metalle, wie z. B. Chrom und dergl., und verursachen auch nur wenig oder praktisch keine Abwasser- bzw. Schlammprobleme. Die Lösung ist stabil, durch ihren Kontakt mit der Oberfläche von Aluminium oder Aluminiumlegierungen wird ein Titan/Aluminiumphosphat und/oder Zirkon/Aluminiumphosphat enthaltender organisch-anorganisch komplexer Überzug gebildet, der selbst nach Verformung des Werkstückes eine hohe Salzwassersprüh- und Feuchtigkeitsbeständigkeit sowie Farbbeständigkeit in kochendem Wasser und in Hochtemperaturdampf aufweist.The coating solutions used in the process according to the invention contain - as explained above - no toxic metals, such as. As chrome and the like., And cause little or practically no sewage or sludge problems. The solution is stable.Thanks to its contact with the surface of aluminum or aluminum alloys, an organic-inorganic complex coating containing titanium / aluminum phosphate and / or zircon / aluminum phosphate is formed, which, even after the workpiece has been deformed, has a high salt water spray and moisture resistance as well as color stability in boiling Has water and in high temperature steam.

Bei Einhaltung der vorerwähnten Verfahrensbedingungen wird der Glanz der Oberfläche des behandelten Werkstückes durch die Überzugsreaktion nicht beeinträchtigt.If the aforementioned process conditions are observed, the gloss of the surface of the treated workpiece is not affected by the coating reaction.

Die Erfindung wird anhand der nachfolgenden Beispiele beispielsweise und näher erläutert.The invention is illustrated by the following examples, for example and in more detail.

Beispiel 1example 1

Aluminiumplatten (A 5052) mit den Abmessungen 0,4 x 70 x 150 mm wurden mit einem wässrigen 1,5%-igen alkalischen Entfettungsmittel gereinigt, 7 Sekunden lang mit einer Überzugslösung, die

Figure imgb0002
enthielt und einen pH-Wert von 4,0 sowie eine Temperatur von 60 °C aufwies, besprüht, dann mit Leitungswasser und schließlich mit vollentsalztem Wasser gespült. Die Trocknung erfolgte in einem Heißluftofen bei 200 °C innerhalb von 2 Minuten.Aluminum plates (A 5052) measuring 0.4 x 70 x 150 mm were cleaned with an aqueous 1.5% alkaline degreasing agent, for 7 seconds with a coating solution which
Figure imgb0002
 contained and had a pH of 4.0 and a temperature of 60 ° C, sprayed, then rinsed with tap water and finally with deionized water. Drying was carried out in a hot air oven at 200 ° C within 2 minutes.

Die so behandelten Platten wurden 15 Minuten in kochendes Leitungswasser getaucht und auf Farbveränderungen ihrer Oberfläche hin überprüft. Die Bewertung erfolgte nach folgender Abstufung :

  • 5 = ohne jede Farbveränderung, ohne sichtbare Verminderung des Glanzes,
  • 4 = äußerst geringfügige Gelbverfärbung, ohne Verminderung des Glanzes,
  • 3 = schwache gelb-bräunliche Verfärbung, etwas verminderter Glanz,
  • 2 = Braunfärbung und verminderter Glanz,
  • 1 = insgesamt erhebliche Schwarverfärbung, verminderter Glanz.
The plates treated in this way were immersed in boiling tap water for 15 minutes and checked for changes in the color of their surface. The rating was based on the following grading:
  • 5 = without any color change, without a visible reduction in gloss,
  • 4 = extremely slight yellowing, without reducing the gloss,
  • 3 = weak yellow-brown discoloration, slightly reduced gloss,
  • 2 = brown color and reduced gloss,
  • 1 = overall considerable black discoloration, reduced gloss.

Parallel zum Kochwassertest wurden behandelte Platten um 180° gebogen (Radius der Biegung 0,6 mm) und 120 Stunden lang einerseits einem Salzwassersprühtest (JIS Z-2371) und andererseits 120 Stunden lang dem Feuchtigkeitstest (JIS Z-0228) unterworfen. Knickstellen und ebene Flächen wurden auf Korrosion untersucht und die Teststücke bewertet entsprechend :

Figure imgb0003
In parallel to the boiling water test, treated plates were bent through 180 ° (radius of the bend 0.6 mm) and subjected to a salt water spray test (JIS Z-2371) for 120 hours and the moisture test (JIS Z-0228) for 120 hours. Kinks and flat surfaces were examined for corrosion and the test pieces were evaluated accordingly:
Figure imgb0003

Die erzielten Ergebnisse waren wie folgt :

Figure imgb0004
The results obtained were as follows:
Figure imgb0004

Beispiel 2Example 2

Aluminiumplatten (A 5082) mit den Abmessungen 0,4 x 70 x 150 mm wurden wie in Beispiel 1 gereinigt und 10 Sekunden lang mit einer Überzugslösung, die

Figure imgb0005
enthielt und einen pH-Wert von 4,5 sowie eine Temperatur von 65 °C aufwies, besprüht. Der Überzug wurde alsdann mit Wasser, nochmals mit vollentsalztem Wasser gespült und in einem Heißluftofen bei 200 °C 2 Minuten lang getrocknet.Aluminum plates (A 5082) with the dimensions 0.4 x 70 x 150 mm were cleaned as in Example 1 and for 10 seconds with a coating solution which
Figure imgb0005
 contained and had a pH of 4.5 and a temperature of 65 ° C, sprayed. The coating was then rinsed with water, again with deionized water, and dried in a hot air oven at 200 ° C for 2 minutes.

So behandelte Platten wurden dem Pasteurisiertest unterworfen, d. h. 30 Minuten lang in einem Druckkessel bei 125 °C Hochdruckdampf ausgesetzt und auf eine Farbveränderung ihrer Oberfläche geprüft. Die Versuchsergebnisse wurden nach dem gleichen Bewertungsverfahren wie dem Kochwassertest des Beispiels 1 unterworfen.Plates treated in this way were subjected to the pasteurization test, i. H. Exposed to high pressure steam in a pressure vessel at 125 ° C for 30 minutes and checked for a color change on its surface. The test results were subjected to the same evaluation procedure as the cooking water test of Example 1.

Parallel zum Pasteurisiertest wurden behandelte Platten mit einem handelsüblichen Epoxidlack für Hohlgefäße (XJ-K 190 A) 3 bis 4 J.Lm beschichtet, 8 Minuten lang bei 205 °C eingebrannt, 1 Stunde in eine kochende wässrige Lösung von 3 %-iger Zitronensäure und 3 %-igem Kochsalz getaucht und bei bis zu 80°C getrocknet. Anschließend wurden mit einem scharfen Messer in die Lackfläche bis zum Metalluntergrund Kreuze eingeritzt, Zellophanklebstreifen fest aufgepreßt, diese heftig abgerissen und das Ablösen der Farbschicht geprüft.In parallel to the pasteurization test, treated plates were coated with a commercially available epoxy paint for hollow vessels (XJ-K 190 A) for 3 to 4 J.Lm, baked for 8 minutes at 205 ° C, 1 hour in a boiling aqueous solution of 3% citric acid and 3% table salt dipped and at up to 80 ° C dried. Then, with a sharp knife, crosses were scratched into the paint surface down to the metal surface, cellophane adhesive strips were pressed on firmly, these were torn off violently and the detachment of the paint layer was checked.

Die Bewertung der Haftfestigkeit der Lackschicht erfolgte gemäß :

Figure imgb0006
The adhesive strength of the paint layer was evaluated in accordance with:
Figure imgb0006

Die Ergebnisse waren wie folgt :

Figure imgb0007
The results were as follows:
Figure imgb0007

Beispiel 3Example 3

Es wurde ein Vergleichsversuch durchgeführt, der unter den Bedingungen des Beispiels 1 erfolgte. Der Überzug wurde mit Hilfe einer Lösung gebildet, die

Figure imgb0008
enthielt einen pH-Wert von 3,8 sowie eine Temperatur von 40 °C, aufwies.A comparison test was carried out, which was carried out under the conditions of Example 1. The coating was formed using a solution that
Figure imgb0008
 contained a pH of 3.8 and a temperature of 40 ° C.

Die Bewertung der Überzugsqualität erfolgte durch Kochwassertest, Salzsprühtest und Feuchtigkeitstest. Die Ergebnisse waren wie folgt :

Figure imgb0009
The coating quality was assessed by boiling water test, salt spray test and moisture test. The results were as follows:
Figure imgb0009

Claims (8)

1. Process for the formation of coatings on surfaces of aluminum and alloys thereof by means of aqueous acidic solutions containing phosphate ions, at least one di-to-hexaester of phosphoric acid and inositol and/or alkali metal or alkaline earth metal salts thereof as well as at least one titanium and/or zirconium compound, characterized in that the surface is brought in contact with a solution having a pH- value from 2 to 6 and containing in addition at least one pyrazole of the formula
Figure imgb0011
wherein X, Y and Z are the same or different functional groups, such as hydrogen hydroxy-, alkyl-, acyl-, amino- or nitro groups.
2. Process according to claim 1, characterized in that the surface is brought in contact with a solution containing 0.1 to 20 g/I phosphate ions.
3. Process according to claim 1 or 2, characterized in that the surface is brought in contact with a solution containing 0.05 to 10 g/I pyrazole compound.
4. Process according to claim 1, 2 or 3, characterized in that the surface is brought in contact with a solution containing 0.05 to 10 g/l of di-to-hexaester of phosphoric acid and inositol and/or salts thereof.
5. Process according to one or more of the claims 1 to 4, characterized in that the surface is brought in contact with a solution containing 0.005 to 10 g/I titanium and/or zirconium compound (calculated as titanium and zirconium metal respectively).
6. Process according to one or more of the claims 1 to 5, characterized in that the surface is brought in contact with a solution containing in addition boron fluorides, such as fluoboronic acid and/or water soluble salts thereof.
7. Process according to one or more of the claims 1 to 6, characterized in that the surface is brought in contact with a solution containing in addition sulfate and/or fluoride ions.
8. Process according to one or more of the claims 1 to 7, characterized in that the surface is brought in contact with a solution heated to 40 to 90 °C.
EP81201255A 1980-05-12 1981-11-10 Formation of coatings on aluminium surfaces Expired EP0078866B1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP55062539A JPS5839232B2 (en) 1980-05-12 1980-05-12 Film chemical conversion treatment solution for aluminum and aluminum alloy surfaces
EP81201255A EP0078866B1 (en) 1980-05-12 1981-11-10 Formation of coatings on aluminium surfaces
DE8181201255T DE3172781D1 (en) 1981-11-10 1981-11-10 Formation of coatings on aluminium surfaces

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JP55062539A JPS5839232B2 (en) 1980-05-12 1980-05-12 Film chemical conversion treatment solution for aluminum and aluminum alloy surfaces
EP81201255A EP0078866B1 (en) 1980-05-12 1981-11-10 Formation of coatings on aluminium surfaces

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EP0078866A1 EP0078866A1 (en) 1983-05-18
EP0078866B1 true EP0078866B1 (en) 1985-10-30

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DE3236247A1 (en) * 1982-09-30 1984-04-12 Metallgesellschaft Ag, 6000 Frankfurt METHOD FOR SURFACE TREATMENT OF ALUMINUM
US4992116A (en) * 1989-04-21 1991-02-12 Henkel Corporation Method and composition for coating aluminum
US5209788A (en) * 1990-11-21 1993-05-11 Ppg Industries, Inc. Non-chrome final rinse for phosphated metal
US5147472A (en) * 1991-01-29 1992-09-15 Betz Laboratories, Inc. Method for sealing conversion coated metal components
US5226976A (en) * 1991-04-15 1993-07-13 Henkel Corporation Metal treatment
US5514478A (en) * 1993-09-29 1996-05-07 Alcan International Limited Nonabrasive, corrosion resistant, hydrophilic coatings for aluminum surfaces, methods of application, and articles coated therewith
EP1221497A3 (en) * 1998-06-19 2003-12-03 Alcoa Inc. Method for inhibiting stains on aluminum product surfaces
BR9912174A (en) * 1998-06-19 2001-04-10 Alcoa Inc Method to prevent stains on the surfaces of aluminum products
AU5970499A (en) * 1998-08-24 2000-03-14 Akzo Nobel N.V. Anti-skinning agent for coating compositions
US10329674B2 (en) * 2016-12-01 2019-06-25 Vitech International, Inc. Fluorinated acid compounds, compositions and methods of use

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US3076734A (en) * 1960-07-01 1963-02-05 Acme Steel Co Protective coatings on metals
US3695942A (en) * 1970-12-02 1972-10-03 Amchem Prod Zirconium rinse for phosphate coated metal surfaces
JPS535622B2 (en) * 1973-02-12 1978-03-01
CA1083335A (en) * 1976-05-10 1980-08-12 Chemed Corporation Composition and method of inhibiting corrosion

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