PURPOSE: To form hot melt type fluorine resin coat on the inside of steel pipe, etc. without causing swell, exfoliation, etc. by coating a specific fluorine resin primer on the inside of steel pipe, a hot melt tupe fluorine resin layer being formed on the primer coat followed by coating by heated flyidized body of a hot melt type fluorine resin.

CONSTITUTION: A primer composed of an aqueous tetrafluoroethylene resin dispersion containing chromic acid, chromium fluoride, and phosphoric acid is coated on the inside of a steel pipe, etc., and then a hot melt-type fluorine resin of tetrafluoroethylene-perfluoroalkylvinylether copolymer is uniformly spread on the primer layer in a nondrying state and heated to the decomposition temperature of the foresaid resin to form a baked adhesive layer on the inside of the steel pipe. Then, a heated fluid of a hot melt type fluorine resin is forced into the pipe by using a metal core to cause the film to be adhered to the inside. Thus, a strongly adhered film can be formed without being affected by various restrictions as in the conventional methods.