The differences between the two are as follows:

　　(1) Different appearances

　　Plastic-coated steel pipes are based on steel pipes with the outer surface coated with polyethylene or other plastic powder. The inner and outer surfaces of the steel pipe are evenly coated, and some special ones have an anti-corrosion layer, and whether or not a flame retardant is added depends on the application. Although lined steel pipes are also based on steel pipes, their outer surface is galvanized and painted, with an inner lining of plastic or an anti-corrosion layer. In the market, most inner linings are PE or PP-R plastic layers, used for drainage and water supply.

　　(2) Different production processes

　　The production process of plastic-coated steel pipes involves pre-treating and heating the steel pipe before rapid plastic coating, and then allowing it to solidify and form. Lined steel pipes include two processes: lining and rotational molding. Lining involves applying adhesive to the outer wall of the plastic pipe and placing it inside the preheated steel pipe so that the plastic pipe expands due to heat. Rotational molding involves pre-treating and heating the steel pipe and then rolling plastic powder onto the inner wall of the steel pipe, allowing it to cool and solidify.

　　(3) Different connection methods

　　The connection methods for plastic-coated steel pipes mainly include flange connection, groove connection, and threaded connection; while lined steel pipes use flange connection and groove connection