Brief introduction to coating process of anticorrosive coating for conveying pipe-2

"China's natural gas pipeline from the west to the East is 4169km long, with a total capacity of 20 billion cubic meters per day Coating and cathodic protection are used to protect the outer wall of the pipeline This kind of pipeline coating has the following varieties (1) Petroleum asphalt has been used for more than 30 years in China The process is hot coated petroleum asphalt, wrapped with glass cloth and covered with plastic film, with low cost It is often used in petroleum sector, with simple construction Its disadvantages are high water absorption, poor heat resistance, use range of 0-40 ℃, not resistant to soil microorganisms, easy to be penetrated by plants, and gradually eliminated in Europe and the United States (2) The technology of coal tar pitch "enamel" is to first apply a thin coal tar pitch primer to wet the surface, reheat and apply solvent-free coal tar pitch "enamel", and then wrap the tape Its advantages are low water absorption, applicable to the temperature range of - 30 ~ 95 ℃, good corrosion resistance, resistance to soil bacteria, resistance to plant root penetration, and low cost The disadvantage is that the flue gas during construction is harmful to workers' health, and the compatibility with cathodic protection is poor In the early 1920s, this coating was used in Wuhan water pipeline After excavation and recheck in the 1950s, the steel pipe is still metallic luster and corrosion-free (3) This technology has been used in foreign countries for 30 years It has strong adhesion and corrosion resistance with steel pipes It can be used in the range of - 60 ~ 110 ℃ The disadvantage is poor waterproof, easily damaged by impact, and high cost The operation is shot blasting and derusting to Sa2.5 level, electrostatic spraying epoxy powder (novolac epoxy resin plus phenolic curing agent) with induction ring heating to 230 ~ 260 ℃, the pipe rotating binding force on the operation line for 2 ~ 3min, making the powder level and solidified, then spraying water for quenching, the film thickness is 400um (4) Epoxy asphalt coating has been used in foreign countries for 40 years, the United States started in 1959, Japan started in 1967, and has been used in China for 20 years The utility model has the advantages of strong adhesion, good water resistance, microorganism resistance and plant root penetration resistance, which can be used in the environment of - 60 ~ 110 ℃ and can be solidified at room temperature The disadvantage is that the two-component is inconvenient, the coating is brittle, the VOC of solvent pollutes the environment, and it can be used in the branch project with small scale and small pipeline diameter