Coating Pipe Types and Selection Guide

Pipe coatings protect steel from corrosion, reduce friction and ensure water quality. Choosing the right coating depends on the fluid, operating environment and applicable standards.

1. Why Coat Pipe?

Bare steel corrodes quickly in moist or aggressive environments. Coatings create a barrier between the steel and the fluid/soil, preventing rust, scaling and contamination. They also reduce hydraulic friction and improve flow efficiency.

2. Common Coating Types

• IPN8710 — a two-component epoxy ceramic coating used for internal drinking water pipes. Non-toxic, smooth and resistant to corrosion.
• FBE (Fusion Bonded Epoxy) — a thermoset powder coating fused to the pipe surface. Excellent for buried and submerged service.
• PE Coating — polyethylene extrusion coating for external corrosion protection, used in TPEP and 3PE systems.
• Epoxy Coal Tar — used for sewage and submerged pipelines, though less common now due to environmental concerns.

3. Selection Criteria

• Fluid type (potable water, sewage, oil, gas).
• Installation environment (buried, above ground, submerged).
• Operating temperature range.
• Applicable standards (AWWA C213, GB/T 23257).

Internal vs External Pipe Coatings

Pipe coatings serve different purposes depending on location. External coatings protect against soil corrosion and moisture. Internal coatings protect against fluid corrosion and reduce friction. In water supply pipes, internal epoxy lining also prevents contamination and maintains water quality. Always specify both internal and external coating requirements.

Internal vs External Pipe Coatings

Pipe coatings serve different purposes depending on location. External coatings protect against soil corrosion and moisture. Internal coatings protect against fluid corrosion and reduce friction. In water supply pipes, internal epoxy lining also prevents contamination and maintains water quality. Always specify both internal and external coating requirements on the purchase order, along with the relevant standard (AWWA C213, GB/T 23257, ISO 21809).

Coating Thickness and Quality Control

Coating thickness directly affects performance. Too thin and the coating may pinhole or wear through quickly. Too thick and it may crack or delaminate. Typical TPEP coating thickness is 1.5–3.0 mm total. Quality control includes: visual inspection for holidays and defects, holiday spark testing to detect pinholes, thickness measurement with a magnetic gauge, and adhesion testing. Reputable manufacturers provide coating test reports with every batch.

• Holiday testing — uses a spark tester to find pinholes in the coating.
• Thickness measurement — verifies coating meets specified minimum thickness.
• Adhesion test — checks coating-to-steel bond strength.
• Visual inspection — looks for blisters, bubbles, runs and sags.

Pipe Coating FAQ

Answers to the most common questions about pipe coating selection.

• What is the difference between internal and external pipe coating? — External coating protects against soil corrosion and moisture. Internal coating protects against fluid corrosion and reduces friction. For water supply pipes, internal epoxy lining also prevents contamination and maintains water quality.
• How thick should pipe coating be? — Typical external coating thickness is 0.5–3.0 mm depending on the system. Internal epoxy lining is usually 0.3–0.8 mm. Always specify the required thickness on the purchase order.
• Can I recoat existing pipe? — Yes, but the old coating must be removed completely (by blasting) before applying new coating. Recoating is common for pipeline rehabilitation projects.
• What is FBE coating? — Fusion Bonded Epoxy (FBE) is a powder coating that melts and cures when applied to hot steel. It provides excellent corrosion resistance and is often used as the primer layer in three-layer systems.
• How do I repair coating damage? — Use repair kits specifically designed for the coating system. Clean the area, apply the repair material, and smooth it out. Always follow the manufacturer's repair procedure.

Coating Standards Reference

Common pipe coating standards include: AWWA C213 (fusion bonded epoxy for water pipelines), GB/T 23257 (polyethylene coating for buried steel pipe), ISO 21809 (petroleum and natural gas industries), and DIN 30670 (German standard for polyethylene coating).