substrates with oxidized surfaces, as e.g. SiO2 layers on silicon semiconductors and aluminum surfaces, are wetted with an organic silicon compound, for example, γ-aminopropyltriethoxysilane dissolved in an organic solvent such as trichlorotrifluoro ethane. The solvent is then removed in a dry atmosphere. The evaporation step can be carried out by suspending the substrate in volvent vapor over a supply of refluxing solvent while cooling the solvent vapor such that fresh, dry solvent vapor continuously passes along the substrate and absorbs traces of moisture. Subsequently, a coating is applied from a solution of a polyamido carbon acid formed of pyromellitic acid anhydride and an aromatic amino component and the polyamido carbon acid is heated to form an adherent layer of polyimide.