Process for coating metallic surfaces with a passivating agent, the passivating agent and its use

Abstract

The invention relates to a process for coating metal surfaces with an aqueous composition in the form of a solution or in the form of a dispersion, the composition comprising at least one phosphate, at least 3 g/l of at least one titanium or/and zirconium compound and at least one complexing agent, and also to corresponding aqueous compositions. The coatings prepared thereby have very good bare corrosion protection in the NSS salt spray test and in the condensation-water/constant-climate test

What is claimed is: 
     
         1 . A process for coating and passivating metal surfaces with an aqueous composition in the form of a solution or in the form of a dispersion, wherein the composition comprises
 12 to 400 g/L of at least one phosphate,   3 to 200 g/L of at least one titanium or zirconium compound,   1 to 200 g/L of at least one complexing agent, selected from the group of compounds based on phosphonic acid, phytin and tannin, wherein content of compounds based on phosphonic acid amounts to 0 or 1 to 200 g/L, and wherein the content of compounds based on phytin or tannin amounts to 0 or 0.05 to 30 g/L, and also   3 to 100 g/L of cations of aluminum, chromium(III) or zinc or at least one compound having a content of aluminum, chromium(III) or zinc in the range from 1 to 100 g/L, calculated as metal, wherein the content of zinc is at least 3 g/L,   in that the composition has values of the free acid FA in the range from 2 to 25 points, values of total acid TA in the range from 20 to 45 points, and values of total acid Fischer TAF in the range from 12 to 20 points, and   in that a wet film of the aqueous composition is dried on metal strips or sheets without the wet film or the dried film being rinsed with water.   
     
     
         2 . The process according to  claim 1 , wherein the composition further comprises cations of iron or manganese or at least one compound having a content of iron or manganese. 
     
     
         3 . The process according to  claim 1 , wherein the composition comprises a total content of cations of aluminum, chromium(III), iron, manganese or zinc or of at least one compound having a content of aluminum, chromium(III), iron, manganese or zinc in the range from 3 to 100 g/L, calculated as metal. 
     
     
         4 . The process according to  claim 1 , wherein the composition substantially contains only cations of aluminum, iron, manganese, titanium, zinc or zirconium. 
     
     
         5 . The process according to  claim 1 , wherein the composition comprises a total content of at least one titanium or zirconium compound based on complex fluoride in the range from 1 to 200 g/L. 
     
     
         6 . The process according to  claim 1 , wherein the composition comprises a content of free fluoride F free  in the range from 0.01 to 5 g/L or a content of total fluoride F total  in the range from 3 to 180 g/L. 
     
     
         7 . The process according to  claim 1 , wherein the composition further comprises at least one silane/silanol/siloxane/polysiloxane. 
     
     
         8 . The process according to  claim 7 , wherein the composition contains a content of at least one silane/silanol/siloxane/polysiloxane in the range from 0.1 to 200 g/L, calculated on the basis of silane or polysiloxane in the particular starting compound in question. 
     
     
         9 . The process according to  claim 1 , wherein the composition further comprises at least one additive selected from the group consisting of a wetting agent, a demulsifying agent, an emulsifier, an antifoam, a corrosion inhibitor, and a wax. 
     
     
         10 . The process according to  claim 1 , wherein the composition has a pH value in the range from 0 to 10. 
     
     
         11 . A process according to  claim 1 , wherein the metal surface treated with the aqueous composition is a metal surface comprising at least one member selected from the group consisting of aluminum, iron, magnesium, titanium, zinc, and tin, in strips or sheets. 
     
     
         12 . A coating prepared by the process according to  claim 1 . 
     
     
         13 . A metal component coated by the process according to  claim 1 . 
     
     
         14 . A motor vehicle comprising the metal component of  claim 13 . 
     
     
         15 . An architectural element comprising the metal component of  claim 13 . 
     
     
         16 . A domestic appliance coated by the process according to  claim 1 .