Abstract: A method for applying a single-layer or multi-layer anti-corrosion coating on a metallic substrate being part of a pipe or a duct accessory to be buried or submerged for conveying a fluid such as water, petroleum products, gas or sanitizing products. including a) preparing the surface of the substrate by mechanical means only; b) applying an adhesion promoter on the prepared surface comprising an aqueous solution of at least one silane without any further chemical process; C) applying a layer of an epoxy-resin powdery paint on the surface coated with the adhesion promoter; and d) applying at least one thermal process to the surface at least of the substrate, wherein at least one step d) for thermal processing is carried out between steps a) and b) or between steps b) and c).