Plastic-coated steel pipes are a new type of composite pipe material. They are made by coating the surface of a steel pipe with a polymer material (such as epoxy resin, polyethylene, etc.) to improve its corrosion resistance, wear resistance, and insulation properties. The following is a detailed analysis of plastic-coated steel pipes:

First, the definition and composition of plastic-coated steel pipes:
Base material: Seamless or welded steel pipe as the base, providing structural strength.
Coating: Thermoplastic plastics (such as PE, PVC) or thermosetting resins (such as epoxy resin) are applied to the inner and outer surfaces of the pipe wall through spraying, roller coating, or dip coating processes, forming a protective layer of 0.1-0.5mm.

Second, the core classification of plastic-coated steel pipes:
Plastic-coated steel pipes are classified according to the coating material:
Epoxy resin coating: High temperature resistance, chemical corrosion resistance, suitable for oil and chemical transportation.
Polyethylene (PE) coating: UV-resistant, low-temperature resistant, commonly used in municipal water supply and gas supply.
Polyurethane (PU) coating: High wear resistance, suitable for mining and sediment transportation environments. Classification by Application of Plastic-Coated Steel Pipes:
Buried Pipelines: Emphasis on corrosion resistance and soil stress resistance.
Industrial Pipelines: Emphasis on high temperature resistance, high pressure resistance, and resistance to chemical media corrosion.
Building Water Supply and Drainage: Emphasis on hygiene, non-toxicity, and smooth inner wall.

Third, Production Process of Plastic-Coated Steel Pipes
Base Steel Pipe Pretreatment: Acid pickling and rust removal → Phosphating treatment → Water rinsing → Drying.
Coating Application of Plastic-Coated Steel Pipes:
Powder Coating: Electrostatic adsorption of epoxy/PE powder, high-temperature melting and curing.
Fluid Coating: Spraying after mixing epoxy resin and hardener, natural air drying, or baking curing.
Post-treatment: Quality inspection (thickness, adhesion testing), packaging, and transportation.

Fourth, Performance Advantages of Plastic-Coated Steel Pipes
Corrosion Resistance: The coating of plastic-coated steel pipes isolates oxygen and moisture, resulting in a service life of over 50 years (e.g., epoxy coating in a salt spray environment). Wear Resistance: The polyurethane coating of the plastic-coated steel pipe has high hardness and can resist the erosion of particulate matter (friction coefficient <0.05).
Insulation: Resistivity >1×10¹²Ω·m, effectively preventing galvanic corrosion.
Low Fluid Resistance: The smooth inner wall of the plastic-coated steel pipe reduces flow resistance by approximately 30% compared to traditional steel pipes.
Lightweight and High-Strength: The density of the plastic-coated steel pipe is only 1/7 that of steel pipe, but its compressive strength reaches 50MPa.

Fifth, Typical Application Scenarios of Plastic-Coated Steel Pipes
Municipal Engineering: Urban water supply, drainage, and gas transmission (mainly PE coating).
Energy Industry: Long-distance oil and gas pipelines (epoxy coating + cathodic protection combined).
Manufacturing: Chemical media and cooling water circulation systems.
Agricultural Irrigation: Resistant to acid and alkaline soil and groundwater corrosion.
Marine Engineering: Tidal Zone Protection (Requires Additional Fiberglass Reinforcement)

Sixth, Technical Parameters and Standards of Plastic-Coated Steel Pipes
Standards: GB/T 5135 (Epoxy Coating), GB/T 17219 (Hygienic Requirements for Drinking Water Pipelines).
Pressure Rating: DN15-DN3000 plastic-coated steel pipes, pressure 0.6-2.5MPa.
Temperature Range: Epoxy coating -30℃~120℃, PE coating -40℃~70℃.
Coating Thickness: Outer wall 150-300μm, inner wall 80-150μm (depending on standard requirements)

Seventh, Selection and Maintenance Points of Plastic-Coated Steel Pipes
Selection Recommendations for Plastic-Coated Steel Pipes:
(1) For conveying corrosive media (such as acids and alkalis), epoxy coating is preferred.
(2) For environments requiring frequent bending or vibration, flexible PE coating is preferred. 
(3) High-pressure pipelines should be paired with high-strength base pipes (such as Q345B steel).
Installation Precautions for Plastic-Coated Steel Pipes:
(1) Use rubber sealing rings to avoid scratching the coating with hard seals.
(2) Welded joints need to be recoated to prevent localized corrosion.
Maintenance of Plastic-Coated Steel Pipes:
(1) Regularly check the integrity of the coating (ultrasonic testing every 2 years).
(2) Use a non-metallic scraper to clean the deposits inside the plastic-coated steel pipe.
(3) For long-term non-use, the internal medium of the plastic-coated steel pipe must be drained, and it must be dried.

Eighth. Market Trends and Innovations
(1) Environmentally Friendly Coating: Develop a water-based epoxy resin to reduce VOC emissions.
(2) Composite Structure: A double-coating process of outer PE and inner epoxy, balancing weather resistance and chemical resistance.
(3) Intelligent Monitoring: Integrated fiber optic sensors monitor the coating corrosion status in real time. Plastic-coated steel pipes, with their superior comprehensive performance, have become an important alternative to traditional metal pipes, especially offering significant advantages in harsh working conditions. Correct selection and standardized construction are key to maximizing their effectiveness. In the future, with the development of new material technologies, their application in the industrial field will become even more widespread.