Coating Method

Abstract

The invention relates to a method for coating objects, particularly plumbing fixtures, having metallic surfaces. According to the method, at least one organosilane is applied during the so-called sol-gel process after an optionally provided pretreatment step that serves to activate the metallic surfaces, and the coating obtained thereby is transformed into a polysiloxane coating. This transformation of the coating into a polysiloxane coating preferably ensues by a thermal treatment effected at temperatures of <100° C., preferably <70° C.

Description

EXAMPLES

For coating sanitary fittings, in each case two bodies of a so-called single-lever mixer (without head and control part) comprising brass or comprising the plastics material ABS (acrylonitrile-butadiene-styrene copolymer) are provided. A nickel coat is applied to these bodies by chemical nickel plating in a manner known to the person skilled in the art. Commercial chemical nickel solutions can be used for this purpose.

The nickel-coated bodies thus obtained are divided into two groups, each group consisting of a nickel-coated ABS body and a nickel-coated brass body. The two bodies of one group are coated directly according to the invention, whereas the two bodies of the second group are provided with a silver coat prior to this coating.

For coating with silver, the nickel-coated bodies of the second group are electrolytically coated with a commercially available silver electrolyte (type Arguna 621, from OMG, Germany). The coat thickness of the silver is 2 μm.

The silver surface thus obtained is rinsed with demineralized water and then with ethanol. This silver-coated substrate is immersed in a 1 mmol ethanolic solution of 11-mercapto-1-undecanol and left in this solution for 24 h. Thereafter, the substrate thus treated is rinsed first with ethanol and then with demineralized water and is then dried.

Both the bodies of the first group (nickel-coated bodies) and the bodies of the second group (silver-coated bodies) can then be further coated according to the invention.

For this purpose, an organosilane mixture comprising two organosilanes in the ratio 1:1 is first provided. The first organosilane is a 5% strength aqueous solution of a modified fluoroalkylsilane (Dynasylan 8800, Degussa, Germany). This product is obtained as an ethanolic solution and can be diluted with water in a corresponding manner. The second organosilane is a solution of 5 g of 1,2-bistriethoxysilylethane (BTSE, Merck, Germany) in 30 ml of ethanol.

For the preparation of the composition according to the invention (organosilane mixture), the solution of BTSE in ethanol is prehydrolyzed for 1 h. This prehydrolysis product is slowly added dropwise with stirring to about 50 ml of dilute acetic acid (pH=3.5). The solution thus obtained is stirred for a further 1 h and mixed with the 5% strength solution of Dynasylan 8800. The final composition thus obtained is sprayed onto the metallic surfaces of the four bodies, in particular at a spray admission pressure of 2 bar and with a minimum metering opening of the spray nozzle (diameter 0.7 mm) of the spray gun. The coating thus obtained is allowed to partly dry and is then subjected to a thermal aftertreatment at a temperature of 70° C. This aftertreatment is carried out over a period of 45 minutes.

In the case of all four bodies, a firmly adhering cohesive polysiloxane coating having outstanding properties is obtained. The visual appearance of the overcoated metallic surfaces (nickel or silver) is fully retained. Scratch-resistant surfaces of high transparency and low reflectivity which are easy to clean are formed. Even over longer periods, outstanding corrosion resistance is present and, in the case of the silver-coated bodies, reliable antitarnish properties.

Claims

1. A method for coating articles, in particular sanitary articles, such as sanitary fittings, having at least partly metallic surfaces, comprising the steps of: providing metallic surfacesapplying at least one organosilane to the metallic surfaces by a sol-gel method thus obtaining a coating, andconverting the coating thus obtained into a polysiloxane coating.

2. The method as claimed in claim 1, wherein the conversion of the coating into the polysiloxane coating is carried out by thermal treatment at temperatures of less than about 70° to 100° C.

3. The method as claimed in claim 1, wherein the polysiloxane coating has a thickness less than about 1 to 5 μm.

4. The method as claimed in claim 1, wherein an organosilane mixture comprising at least two organosilanes, is applied to the metallic surfaces.

5. The method as claimed in claim 1, wherein one of the organosilane and an organosilane mixture is applied as a colloidal aqueous solution with a solids content.

6. The method as claimed in claim 1, wherein the organosilane comprises a fluoroalkylsilane.

7. The method as claimed in claim 6, wherein organosilane comprises one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

8. The method as claimed in claim 1, the organosilane comprises a (poly)alkoxysilylalkane.

9. The method as claimed in claim 8, comprising applying an organosilane mixture comprising a modified fluoroalkylsilane and a (poly)alkoxysilylalkane.

10. The method as claimed in claim 1, wherein the metallic surfaces are provided on a plastics body.

11. The method as claimed in claim 1, wherein the metallic surfaces are provided on a body comprising at least one of stainless steel, aluminum, die cast zinc and brass.

12. The method as claimed in claim 1, wherein the metallic surfaces comprise at least one of nickel, palladium-nickel (PdNi), nickel-tungsten (NiW) and chromium.

13. The method as claimed in claim 1, wherein the metallic surfaces comprise at least one of copper and a noble metal.

14. The method as claimed in claim 13, comprising applying a primer to the metallic surfaces before application of the organosilane.

15. The method as claimed in claim 14, wherein the primer comprises a long-chain, ω-functionalized mercaptan.

16. The method as claimed in claim 15, wherein the chain of the primer comprises at least one of methylene units and ethylene glycol units.

17. The method as claimed in claim 16, wherein the primer comprises 11-mercapto-1-undecanol.

18. An article produced by the method of claim 1.

19. A sanitary article comprising: a body comprising at least one of brass and plastic, at least one metal coat on the body, and a polysiloxane coating on the metal coat.

20. The article of claim 19, further comprising: a coat comprising at least one of silver and gold on the metal coat,a primer coat on the coat comprising at least one of silver and gold, preferably comprising a long-chain, ω-functionalized mercaptan, anda polysiloxane coating present on the primer coat.

21 . The article of claim 19, comprising: a plastics body,a nickel coat on the plastics body, anda polysiloxane coating on the nickel coat.

22. The article of claim 19, comprising: a brass body,a nickel coat on the brass body, anda polysiloxane coating on the nickel coat.

23. The article of claim 19, comprising: a plastics body,a nickel coat on the plastics body,a silver coat on the nickel coat,a primer coat on the silver coat, anda polysiloxane coating on the primer coat.

24. The article of claim 19, comprising: a brass body,a nickel coat on the brass body,a silver coat on the nickel coat,a primer coat on the silver coat, anda polysiloxane coating on the primer coat.

25. The article of claim 19, wherein the polysiloxane coating has a coat thickness of less than about 1 to 5 μm.

26. A composition for coating sanitary articles, comprising an organosilane mixture including at least one fluoroalkyl-silane and a (poly)alkoxysilylalkane.

27. The method of claim 1, further comprising at least one pretreatment step for activating the metallic surfaces prior to application of the organosilane to the metallic surfaces.

28. The method of claim 5, wherein the solids content is about 1% to 30% by weight.

29. The method of claim 8, wherein the organosilane comprises 1,2-bistriethoxysilylethane.

30. The method of claim 9, wherein the fluoroalkylsilane comprises one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

31. The method of claim 9, wherein the (poly)alkoxysilylalkane comprises 1,2-bistriethoxysilylethane, is used.

32. The method of claim 10, wherein the plastics body comprises ABS.

33. The article of claim 19, wherein the metal coat comprises at least one of nickel, palladium-nickel (PdNi), nickel-tungsten (NiW), and chromium.

34. The article of claim 20, wherein the primer coat on the coat comprising at least one of silver and gold, comprises a long-chain, ω-functionalized mercaptan.

35. The article of claim 23, wherein the primer coat comprises a long-chain, ω-functionalized mercaptan.

36. The composition of claim 26, wherein the fluoroalkyl-silane comprises one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane

37. The composition of claim 26, wherein the (poly)alkoxysilylalkane comprises 1,2-bistriethoxysilylethane.