Abstract: A method of applying a protective coating to the inner surface of a pipeline includes the steps of adhering a porous flexible hose to the pipeline inner surface, an end of the hose of which is turned inside out and attached to the pipeline. The hose is moved inside the pipeline by progressively turning it inside out and pressing it to the inner surface of the pipeline by providing an excess pressure in a cavity formed by the portion of the hose turned inside out, and producing a counter-pressure before the hose as the same travels lengthwise of the pipeline. The magnitude of the counter-pressure is maintained at a predetermined level in the course of the hose travel. A piston having a passage for the hose is placed in the cavity formed by the portion of the hose turned inside out, and a binder is placed between the piston and the portion of the hose turned inside out. The binder soaks through the pores of the hose to facilitate the formation of a bond between the hose and the inner surface of the pipeline.