a resin - coated steel pipe is provided having excellent mechanical strength and sliding properties . a double coated structure is formed that extends in the pipe &# 39 ; s axial direction and has substantially the same cross section . the structure has a thin steel pipe . attached to the outer surface thereof is a coating layer with adhesive and an alloy resin . that alloy resin is a mixture of a styrenic resin and a crystalline engineering plastic . further , formed on the outer surface of the alloy resin in a thickness required for mechanical strength and sliding properties is a crystalline engineering plastic . the resin - coated steel pipe exhibits markedly improved adhesion of the crystalline engineering plastic to the thin steel pipe and thus is free from a fear of the exfoliation of the plastic .