Asphalt anticorrosive coating is surrounded by asphalt impregnated glass fiber cloth by the entanglement of buried pipeline coating, is China's most used tube cover layer material, its strength is wide raw material source, mature technology, the price is cheap, defect is bibulous rate is big, poor heat resistance, easy to aging, such as poor resistance to bacteria, easy to be reed roots. Coal tar enamel anticorrosive coating Coal tar enamel is a product made of heavy fraction and coal pitch obtained by high temperature coal tar fractionation, adding coal powder and filler, and heating. Compared with the asphalt anticorrosive layer, low water absorption, good bonding function, resistance to plant roots and stems penetration, bacteria resistance, good insulation function, use temperature of -25℃ ~ 80℃, service life of more than 60 years.

China's Tazhong Lunnan crude oil and natural gas pipeline, Jingbian Xi 'an natural gas pipeline are all coal tar enamel anticorrosion coating. Epoxy coal tar coating is a two-component curing coating composed of epoxy resin, coal tar pitch, curing agent and filler. The operating temperature is -20℃ ~ 100℃, and its function is between coal tar enamel, molten epoxy powder and polyethylene. It is widely used in petroleum and water supply engineering in China. 3PE anticorrosive layer organically combines the anticorrosive function of fused epoxy powder with the anti-mechanical scratch protection function of polyethylene, and solves the sales problem of polyethylene at the same time. Because of the poor adhesion of hot melt adhesive, the peel polyethylene has a shielding effect on cathodic protection. The 3PE anticorrosive coating has a high requirement on the surface treatment state of the pipe, and the depth of the anchor stripe should reach 50μm ~ 75μm. Otherwise, the anti-cathode peeling and waterproof seepage ability of the anticorrosive coating will be affected. Fused bonded epoxy powder (FBE) is a single component coating composed of epoxy resin, curing agent, filler and pigment.

In recent years, it has also been widely used in Korla-Shanshan line, Xinjiang and the Yellow River crossing section in China. The double-layer FBE combines the anti-corrosion function of the single-layer FBE with the anti-mechanical damage function of the plastic surface FBE, showing strong bonding function, wide operating temperature -60℃ ~ 100℃, soil stress resistance and good anti-cathode peeling function. Anticorrosive layer of polyethylene tape The main advantages of polyethylene tape are high insulation resistance, good resistance to stray current and convenient construction. The disadvantage is that the soil stress resistance is poor, easy to produce cathodic protection shielding due to poor bonding and high resistance value.