The invention relates to method of coating the surface of an inorganic substrate of glass, silicon dioxide, ceramics or carbon, which method comprises a step of cleaning the surface of the substrate by subjecting the surface to a reducing gas plasma, a step of activating the surface by generating radicals on the surface of the substrate by subjecting the surface to a reducing gas plasma and forming a first layer on the substrate surface using a plasma enhanced polymerization process employing one or more monomers comprising monomers with a sufficient low molecular weight for them to be in their gaseous state in the gas plasma, selected from the group consisting of C.sub.1-C.sub.16 alkanes, C.sub.2-C.sub.16 alkanes, C.sub.2-C.sub.16 alkynes, C.sub.2-C.sub.16 alkynes, styrene, aromatic monomers of styrene compounds, monomers of vinyl- and acrylate-compounds.