PURPOSE: To improve the adhesion between a metal pipe and a resin layer by a method wherein a primer compsn. is applied to the inner surface of a strip like metal panel when the metal panel is molded so as to have a U-shape cross section and a thin metal panel to which primer treatment is applied is bonded to the formed metal pipe after welding but before the coating with a resin at the inner surface weld bead part thereof and in the vicinity thereof.
CONSTITUTION: A strip like metal panel 10 is molded into a metal panel 11 having a U-shape cross section by a metal forming device 3 to be guided to a primer coating device 4. Next, both side edge parts of the metal panel 11 are mutually abutted by a round pipe molding machine 5 to be formed into a metal pipe 12 by a welding machine 6. Next, a thin strip like metal panel 13 having a primer layer 13a formed on the single surface thereof and a layer of an adhesive 13b formed to the other surface thereof is bonded to the inner surface of the metal pipe 12 so as to cover the weld bead part 12a thereof and the vicinity of the weld bead part and the entire inner surface of the metal pipe 12 is coated with the resin extruded from a resin coating device 8. By this constitution, a composite pipe 15 wherein the primer layer 12b is formed to the entire inner surface of the metal pipe excepting the bonded part and the entire inner peripheral surface of the metal pipe is coated with a resin layer 14 is obtained.
GOTO YASUSHI
IKEDA HISAO
