Fusion bonded polyethylene (PE), ethylene acrylic acid copolymer (EAA), epoxy (EP) powder, non-toxic polypropylene (PP), or non-toxic polyvinyl chloride (PVC) are applied as an inner layer to steel pipes, creating steel-plastic composite tubing with a thickness of 0.5 to 1.0mm. This material combines the high strength, ease of connection, and water impact resistance of steel pipes, while overcoming their vulnerabilities to corrosion, contamination, scaling, and the lower strength and poor fire performance of plastic pipes. It is designed for a service life of up to 50 years.