What are the classifications and details of anti-corrosion treatment for plastic-coated steel pipes

First, the classification of plastic-coated steel pipes: 
The coating materials for plastic-coated steel pipes include epoxy resin (epoxy powder) and polyethylene. The inner wall of the plastic-coated steel pipe uses epoxy powder heat-fused as the coating, while the outer wall generally uses epoxy powder or polyethylene for anti-corrosion. Epoxy powder is a thermosetting coating. The plastic-coated steel pipe first undergoes shot blasting for rust removal, followed by medium-frequency heating, and then electrostatic spraying technology is used to spray epoxy powder onto the surface of the plastic-coated steel pipe, which then cures to form the coating.
1. According to the differences in coating raw materials, plastic-coated steel pipes include internally and externally plastic-coated steel pipes, externally galvanized and internally plastic-coated steel pipes, internally epoxy and externally polyethylene anti-corrosion steel pipes, TPEP anti-corrosion steel pipes, etc.
2. According to the application, plastic-coated steel pipes include fire-fighting plastic-coated steel pipes, mining plastic-coated steel pipes, water supply plastic-coated steel pipes, tap water supply plastic-coated steel pipes, and cable protection plastic-coated steel pipes.
3. According to the installation method, plastic-coated steel pipes include overhead plastic-coated steel pipes, municipal utility tunnel plastic-coated steel pipes, and buried plastic-coated steel pipes.
4. According to the connection method, plastic-coated steel pipes include threaded connection plastic-coated steel pipes, clamp and groove connection plastic-coated steel pipes, flange connection plastic-coated steel pipes, bimetallic welded plastic-coated steel pipes, and flexible socket plastic-coated steel pipes.
We can select different plastic-coated steel pipes based on their different uses, corrosion resistance requirements, and connection methods.

Second, do internally and externally plastic-coated steel pipes require anti-corrosion coating or painting?
If both the inside and outside are fully plastic-coated, anti-corrosion coating or painting is not required. If the inside is plastic-coated and only insulation is applied to the outside, anti-corrosion coating or painting is not required. If the inside is plastic-coated and the outside of the plastic-coated steel pipe is directly exposed to the outside, then anti-corrosion coating or painting is required.
Internally and externally coated steel pipes: These are steel-plastic composite pipes made by fusing a 0.5-1.0mm thick layer of polyethylene (PE) resin, ethylene-acrylic acid copolymer (EAA), epoxy (EP) powder, non-toxic polypropylene (PP), or non-toxic polyvinyl chloride (PVC) onto the inner wall of the coated steel pipe. They not only possess the advantages of high strength, easy connection, and resistance to water flow impact found in coated steel pipes, but also overcome the disadvantages of coated steel pipes, such as easy corrosion, pollution, and scaling when exposed to water, as well as the low strength and poor fire resistance of plastic pipes. The design life can reach 50 years. A disadvantage of this process is that bending, heat treatment, and electric welding/cutting are prohibited during installation. When cutting, the cut surfaces should be coated with the non-toxic, room-temperature curing adhesive provided by the manufacturer, and damaged areas should be repaired.