Process flow of 3PE anti-corrosion steel pipe before processing

The coating of 3PE anti-corrosion steel pipe consists of three layers. The bottom layer is an epoxy powder anti-corrosion coating in contact with the steel pipe surface. The middle layer is a copolymer adhesive with branched functional groups. The surface layer is a high-density polyethylene anti-corrosion coating. This three-layer structure effectively combines the advantages of each material, providing excellent corrosion resistance, mechanical protection, and long-term stability.

1.Steel Pipe Surface Pretreatment

The first and most critical step in the production process is the surface preparation of the steel pipe. The pipe is first degreased to remove oil, grease, and other contaminants. Then, it undergoes shot blasting or sandblasting to eliminate rust, scale, welding slag, and debris, achieving a near-white metal finish (typically Sa2.5 standard) with controlled surface roughness. This step ensures strong mechanical adhesion between the subsequent coating layers and the steel pipe substrate.

2.Epoxy Powder (FBE) Application

After pretreatment, the steel pipe is preheated using an induction heating system. The preheating temperature is precisely controlled to ensure the epoxy powder melts and adheres properly. The epoxy powder is electrostatically sprayed onto the pipe surface, forming a thin, uniform primer layer. This layer cures quickly to provide excellent adhesion and corrosion resistance, acting as the foundation of the entire 3PE coating system.

3. Adhesive and Polyethylene (PE) Coating Application

Immediately after the epoxy powder is applied, the middle and outer layers are applied in a continuous process. The copolymer adhesive and high-density polyethylene are co-extruded and wrapped around the rotating steel pipe. The adhesive layer bonds the epoxy primer to the outer polyethylene layer, ensuring strong interlayer adhesion. The outer polyethylene layer provides excellent mechanical protection, chemical resistance, and waterproof performance, forming a tough, seamless barrier against the external environment.

4. Cooling and Solidification

After the three layers are fully applied, the pipe is immediately passed through a water spray cooling line. The controlled cooling process allows the polyethylene to solidify gradually, preventing thermal stress and ensuring the coating remains smooth, wrinkle-free, and firmly bonded to the pipe surface.

5. Finishing and Quality Inspection

After cooling, the pipe ends are trimmed, and any excess coating is removed. Protective caps are installed to prevent damage to the coating during transportation. Every finished pipe undergoes comprehensive quality control before delivery:

Only pipes that pass all inspections are marked with specifications, batch numbers, and certification marks, then packaged for delivery. With mature production technology and strict quality control, 3PE anti-corrosion steel pipe provides a reliable, long-lasting anti-corrosion solution for buried oil and gas, water supply, and municipal pipeline projects worldwide.