In-Depth Exploration of the Manufacturing Process of TPEP Anti-Corrosion Steel Pipes

In-Depth Exploration of the Manufacturing Process of TPEP Anti-Corrosion Steel Pipes

TPEP (Two-layer Polyethylene and Epoxy) anti-corrosion steel pipe is a high-performance pipeline widely used in water transmission, gas supply, and municipal engineering. It combines the advantages of fusion-bonded epoxy (FBE) and polyethylene (PE) coatings, offering excellent corrosion resistance, mechanical strength, and long service life. The following outlines the detailed manufacturing process and key technological considerations.

1. Pipe Preparation

Raw Pipe Selection:
High-quality seamless or spiral welded steel pipes are selected based on the intended pressure grade and application.

Surface Cleaning:

• Internal Cleaning: The inner wall is cleaned using high-pressure air or mechanical methods to remove dust, rust, and scale.

• External Surface Shot Blasting: Achieves a surface cleanliness level of Sa2.5 or above per ISO 8501, ensuring optimal adhesion of coatings.

2. Inner Wall Coating – Fusion Bonded Epoxy (FBE)

Preheating:
The steel pipe is heated to approximately 220–240°C to allow proper fusion of the epoxy powder.

Electrostatic Spraying:
FBE powder is uniformly applied to the internal surface using electrostatic spray guns. The powder melts, fuses, and cures to form a uniform and dense protective layer.

Curing:
The pipe is allowed to cool and solidify naturally or through forced air cooling. The resulting inner coating is smooth, hygienic, and resistant to chemicals and abrasion.

3. Outer Wall Coating – Polyethylene (PE)

Primer Application:
A layer of adhesive (often modified epoxy resin or polyolefin primer) is applied to create a bond between the steel surface and the PE layer.

PE Extrusion Wrapping:
Three-layer or two-layer PE coating is applied by extrusion. The outermost layer is typically black or yellow polyethylene with UV and impact resistance.

Cooling and Solidification:
After the extrusion process, the pipe passes through a water or air cooling section to solidify the PE layer.

4. Inspection and Testing

Coating Thickness Testing:
Ultrasonic or magnetic thickness gauges verify that the FBE and PE layers meet specification.

Holiday Testing:
A high-voltage spark tester is used to detect pinholes or defects in the coating.

Adhesion Testing:
Pull-off tests confirm the adhesion strength of the FBE and PE layers.

Bending and Impact Resistance:
Selected pipes are tested for coating flexibility and toughness.

5. Cutting and End Processing

The pipe ends are processed according to customer requirements—beveled, threaded, or straight-cut. Internal coatings at the ends are sometimes removed to facilitate welding during field installation.

6. Packaging and Storage

Coated pipes are carefully padded and stacked to prevent coating damage. PE end caps are added to protect inner coatings from dust and moisture during transit.

Technical Advantages of TPEP-Coated Pipes

• Double-Sided Protection: Internal FBE for chemical resistance; external PE for mechanical durability.

• Excellent Bonding: Strong adhesion ensures long-term corrosion resistance under buried or underwater conditions.

• Environmental Compliance: FBE is non-toxic and suitable for drinking water pipelines.

• Long Service Life: Typically 30–50 years depending on environment and application.

Conclusion

The TPEP anti-corrosion coating process combines advanced materials and precise application techniques to provide robust and durable protection for steel pipes. As infrastructure demands grow, TPEP pipes offer a reliable solution for long-distance, buried, and corrosive pipeline systems.