Process for coating metallic surfaces with an aqueous composition, and this composition

A process comprising coating a plurality of metallic surfaces in a bath of a composition consisting of

• a) at least one compound selected from the group consisting of a silane, a silanol, a siloxane and a polysiloxane ranging from 0.02 to 1 g/L and wherein the silane, the silanol, the siloxane or the polysiloxane has at least one member selected from the group consisting of an amino group, a urea group GP and a ureido group;
• b) at least two complex fluorides of formula MeF6 wherein Me is a metal selected from the group consisting of titanium, hafnium, zirconium, aluminum and boron;
• water,
• c) at least one cation selected from the group consisting of cerium, chromium, iron, calcium cobalt, copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum, yttrium, zinc, and tin, and
• d) at least one organic compound selected from monomers, oligomers, polymers, copolymers and block copolymers based on acrylic or urethane in a weight ratio of from 1:0.05 to 1:2 of compounds based on silane, silanol, siloxane or polysiloxane, calculated on the basis of the corresponding silanols, to compounds based on organic polymers, calculated as added solids, in the composition, and
• and
• rinsing the coating when freshly applied and prior to thorough drying;
• wherein said plurality of metallic surfaces comprise at least two different metals and said plurality of surfaces are coated in the same said bath, wherein the composition has a free fluoride content in the range of from 0.01 to 1 g/L, and wherein the total amount of the complex fluorides ranges from 0.01 to 100 g/L.

A process comprising coating a metallic surface with a composition, wherein said composition consists of

• at least one silane, siloxane or polysiloxane having at least one member selected from the group consisting of an amino group, a urea group and a ureido group;
• at least two compounds complex fluorides of formula MeF6 wherein Me is a metal selected from the group consisting of titanium, hafnium, zirconium, aluminum and boron;
• water, and
• at least one cation selected from the group consisting of cerium, chromium, iron, calcium cobalt, copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum, yttrium, zinc, and tin,
• wherein the total amount of the complex fluorides ranges from 0.01 to 100 g/L.