Scratch-resistant and stretchable corrosion protective coating for aluminum substrates

The present invention relates to a method for coating the surface of a light metal substrate, comprising the steps of: A. providing the light metal substrate and, optionally, cleaning the substrate surface to be coated, B. coating the optionally cleaned in step A substrate surface in a plasma polymerization reactor by means of plasma, in which - as a precursor in Step B (s) for the plasma, one or more organosilicon as well as (a) no further, or (b) other compounds are used, and the light metal substrate in the plasma polymerization reactor is arranged so in step B, it is located (i) between in which the plasma is formed of the zone, and the cathode, or (ii) acts as the cathode, characterized in that the process is conducted so that the coating produced by the process - a determinable by measurement using XPS carbon content of 5 to 20 atomic%, preferably 10 to 15 atomic%, based on the total number of carbon contained in the coating, silicon and oxygen atoms, - an ASTM D 1925 yellowness index (Yellow Index) of 3, preferably ≦ 2.5 and - a means of Nanoindentation hardness in the range to be measured of 2.5 to 6 GPa, preferably 3.1 to 6 GPa having.