Abstract: Metal substrates, such as steel sheeting or steel plates of large containers and similar structures, are coated in a continuous operation by arranging a polymer stratum that comprises a heat or melt bonding composition in contact with the metal substrate and by directing electromagnetic radiation in the radio frequency range through the polymer stratum without substantially heating the latter onto the substrate for briefly heating a surface area of the substrate to a temperature where the heat or melt bonding composition in contact with the substrate is activated to form a heat or melt bonded connection between the polymer stratum and the metal substrate. The heated surface area is moved continuously so as to bondingly coat the surface of the substrate, e.g. the fuel-receiving compartments of a tanker, with the polymer stratum. An apparatus for the coating process is disclosed and comprises an inductor loop for directing radio-frequency radiation through the polymer stratum onto the metal substrate.