How to Test Plastic Coated Steel Pipe for Long Service Life

Plastic coated steel pipe is one of the most reliable solutions for modern piping systems. It is a type of coated pipe, which also includes variations such as epoxy coated pipe and other steel-plastic composite pipes. By combining the high strength of steel with the corrosion resistance of plastic, these pipes are ideal for water supply, drainage, seawater transport, hot water, oil, and gas pipelines. Proper testing ensures that the pipes meet performance and safety standards.

What Is a Plastic Coated Steel Pipe?

A plastic coated steel pipe is created by fusing a protective plastic layer onto the inner or outer surface of a steel pipe. This results in a durable, corrosion-resistant composite pipe. Compared with traditional steel or plastic pipes, it offers:

· Superior rust and corrosion resistance

· Reduced friction for smooth fluid flow

· High fire safety and mechanical strength

· A design lifespan of up to 50 years

Key Tests for Plastic Coated Steel Pipe

1. Appearance Inspection

Check the pipe’s surface for cracks, bubbles, or uneven coating. A smooth and uniform surface indicates high-quality production.

2. Coating Thickness Measurement

Using an electromagnetic thickness gauge, measure the coating thickness at multiple points on cross-sections from both ends of the pipe. Consistent thickness ensures durability and reliability.

3. Pin-Hole (Spark) Test

A spark leak detector is used to detect tiny defects in the coating. Pipes with a coating thickness of ≤0.4 mm are tested at 1500V, while those >0.4 mm are tested at 2000V. Any spark indicates a coating defect.

4. Adhesion Test

According to CJ/T 120-2008 standards, adhesion tests confirm that the plastic layer bonds strongly to the steel surface. Proper adhesion is essential for long-term performance.

5. Bending Test

For pipes with DN ≤ 50 mm, bending tests simulate stress conditions. The pipe must maintain coating integrity when bent to a 30° angle under controlled conditions (20±5°C).

6. Flattening Test

For DN > 50 mm pipes, flattening tests verify that the coating remains intact under compression. The pipe is compressed to four-fifths of its diameter, with the weld seam perpendicular to the applied force.

7. Impact Test

A 100 mm specimen is subjected to impact testing. The weld seam is positioned opposite the impact point to ensure that the coating can withstand mechanical shock without damage.

Advantages of Plastic Coated Steel Pipe

· Excellent Corrosion Resistance – Protects steel from rust and chemical damage.

· Low Friction Flow – Ensures efficient transport of water, oil, and gas.

· High Strength & Durability – Combines steel’s mechanical strength with plastic’s protective properties.

· Versatile Applications – Epoxy coated pipe is ideal for water supply, heating, oil, and gas; PVC coated pipe works well for drainage, seawater, and gas pipelines.

· Long Service Life – Properly tested and installed, plastic coated steel pipe can last up to 50 years.

Why Testing Matters

Testing is essential to guarantee that each plastic coated steel pipe meets international safety and performance standards. From appearance checks to impact tests, every step verifies quality and durability. For industrial, municipal, or construction applications, only thoroughly tested coated pipes should be installed.

Conclusion

Plastic coated steel pipe is a reliable solution that balances strength, corrosion resistance, and long-term reliability. Choosing properly tested epoxy coated pipe or other coated pipes ensures safety, efficiency, and a service life of decades.

When selecting plastic coated steel pipe for your project, always choose certified suppliers that provide fully tested products to guarantee quality, durability, and long-term performance.