The coating layer should be smooth and flat, without scratches, cracks, pinholes, adherent foreign matter and other defects.
The outer coating of steel pipes should be red (fire-fighting), black or gray (water transmission).
There should be clear and durable signs on coated steel pipes. The content of the signs should at least include: product model, base pipe specifications and wall thickness, implementation standards, production company name or trademark, production date or batch number, etc. Base pipe
The material, specification and size of the steel pipe used for coating should comply with the regulations of GB/T3091, GB/T8163 and SY/T5037.
Coating materials
The epoxy resin powder used for coating should comply with the provisions of the corresponding national standards or industry standards. The coating thickness should comply with the requirements in Table 1.
Table 1 Coating thickness
Nominal diameter DN mm Coating thickness mm
DN≤65>0.30
DN≥80 >0.35
Pinhole test requirements
Carry out the pinhole test according to the method specified in 6.3. The coated steel pipe should have no sparks.
Adhesion requirements
Carry out adhesion test according to the method specified in 6.4. The adhesion of the coating should be level 1 to 3.
Bending resistance
Conduct a bending test according to the method specified in 6.5. The coating should not fall off or break.
Anti-crush performance
Conduct a flattening test according to the method specified in 6.6. The coating should have no peeling or breakage.
Impact resistance
Conduct impact test according to the method specified in 6.7. The coating should have no peeling or breakage.
Vacuum resistance performance
Carry out a vacuum test according to the method specified in 6.8, and the coating should not fall off.
High temperature resistance
Conduct high temperature test according to the method specified in 6.9. The coating should be free of falling off, bulging, cracking, peeling and damage.
Low-temperature resistance
Carry out low-temperature test according to the method specified in 6.10. The coating should not fall off or be damaged. After the test, the coating adhesion should meet the requirements of 5.6.
Pressure cycle
Carry out pressure cycle test according to the method specified in 6.11. The coating should be free of peeling and damage. After the test, the coating adhesion should meet the requirements of 5.6.
Temperature cycle
Conduct a temperature cycle test according to the method specified in 6.12. The coating should not fall off or be damaged. After the test, the coating adhesion should meet the requirements of 5.6.
Warm water aging resistance
Carry out the warm water aging test according to the method specified in 6.13. The coating should not fall off or be damaged.
Outer surface performance
The outer surface of the coated steel pipe is epoxy resin coating and should comply with the provisions of 5.4, 5.5 and 5.6.
The outer surface of the coated steel pipe is a hot-dip galvanized layer and should comply with the relevant regulations of GB/T 3091.
The outer surface of the coated steel pipe is coated with other anti-corrosion materials, which should comply with relevant national standards or industry standards.