Classification of Coal Tar Epoxy Anti-Corrosion Steel Pipes

The anti-corrosion system complies with SY/T 0447-2014 Specification for Epoxy Coal Tar Anti-Corrosive Coating of Buried Steel Pipelines. Classification is mainly based on anti-corrosion structural grade, together with other grouping methods as below.

Classified by Anti-Corrosion Structure (Most Widely Adopted in Engineering)

Ordinary Grade: One Coat & One Cloth

Structure: 1 primer coat + 1 topcoat + 1 layer of glass fiber cloth + 1 topcoat
Minimum total dry film thickness: 0.3 mm
Application: Dry soil with mild corrosion, temporary pipelines, drainage branch pipelines

Reinforced Grade: Three Coats & Two Cloths (Market Mainstream)

Structure: Primer → Topcoat → Glass Fiber Cloth → Topcoat → Glass Fiber Cloth → Topcoat
Minimum total dry film thickness: 0.4 mm
Application: Buried steel pipelines under general soil conditions, sewage pipelines, rainwater pipelines

Extra Reinforced Grade: Five Coats & Three Cloths

Structure: Primer → Topcoat → Glass Fiber Cloth → Topcoat → Glass Fiber Cloth → Topcoat → Glass Fiber Cloth → Topcoat
Minimum total dry film thickness: 0.6 mm
Application: Humid soil, silt, saline-alkali land, areas with abundant groundwater and strong corrosiveness

Classified by Construction Mode

Factory Prefabricated Coal Tar Epoxy Anti-Corrosion Steel Pipe
Sand blasting and derusting, mechanized coating and winding completed in workshop. Stable quality, suitable for mass engineering orders.

On-site Manual Coating & Winding Anti-Corrosion
Construction implemented after pipeline laying, mainly used for weld joint repair and renovation projects. Quality fluctuates greatly due to manual operation.

Classified by Anti-Corrosion Position

Outer Wall Only Anti-Corrosion (Most Common Solution)
The outer wall is protected against soil corrosion while the inner wall remains untreated. Widely used for sewage, rainwater and oil transmission pipelines.

Inner & Outer Wall Coal Tar Epoxy Anti-Corrosion Steel Pipe
Both inner and outer surfaces are coated with coal tar epoxy paint.
Not allowed for drinking water pipelines (the coating contains toxic asphalt ingredients). Only applicable for sewage and industrial wastewater delivery.

Supplementary Technical Notes

Base pipe material: Seamless steel pipe, spiral welded pipe and straight seam welded pipe are all available for coal tar epoxy anti-corrosion treatment.

Limitations: The coating turns brittle under low temperature. Its service life under long-term immersion and high saline-alkali environment is shorter than 3PE coating. Usage is gradually restricted in regions with strict environmental regulations.

Applicable media: Sewage, rainwater, non-potable industrial water, buried oil pipelines. Not suitable for tap water supply pipelines.

Quick Selection Guide

Dry ordinary soil → Reinforced Grade (Three Coats & Two Cloths)

Silt, swamp, saline-alkali land → Extra Reinforced Grade (Five Coats & Three Cloths)

Temporary simple pipelines → Ordinary Grade (One Coat & One Cloth)