Method for coating metal surfaces of substrates and objects coated according to said method

A method for coating metallic surfaces of substrates, comprising the steps of:

• I. supplying a substrate having a cleaned metallic surface,
• II. coating the cleaned metallic surface with an aqueous composition in the form of a dispersion, suspension or a combination thereof of film-forming polymers consisting of a mixture of at least one stabilized polymer dispersion with a solids content of 30 to 80 wt % with a gelling agent in an amount of 0.001 to 20.0 wt %, based on the total mass of the resulting mixture as well as with cations, forming a coating based on an ionogenic gel,
• III. optionally rinsing the coating, drying the coating, baking the coating or a combination thereof, and
• IV. optionally forming another coating having a similar or additional coating composition before drying, baking, or a combination thereof,
• wherein
• between step I and step II, a coating is applied with an aqueous composition in the form of a dispersion, suspension, or a combination thereof based on a colloidal silicatic sol incorporating polyvalent metal cations and optionally a rinsing operation, wherein the polyvalent metal cations, when the aqueous composition includes a demineralized water, are added before the following other constituents:
• 0.725 g/L to 1.45 g/L of zinc nitrate and 0.22 g/L to 0.55 g/L of hexafluorozirconic acid and 0.66 g/L to 1.1 g/L of manganese nitrate adjusted to about pH 4.5 with sodium carbonate and 25 g/L of amorphous silica.