Present situation of corrosion and anticorrosion measures for gas pipe
In the urban gas pipe network, gas pipes are mostly distributed in ring or branch shape. Pipe fitting distribution is dense and pipe diameter change is common. With the rapid development of urban construction, the surrounding environment is complex or even sudden, and the interference of urban stray current is serious. This requires that do the work well of steel pipe anticorrosion. From the perspective of pipeline corrosion, most of them are concentrated perforation corrosion, and a few are uniform corrosion. Combined with the corrosion mechanism, it is not difficult to see that electrochemical corrosion is the main cause of gas pipe network corrosion. Pure chemical corrosion and bacterial corrosion also exist to varying degrees. In view of the three processes of electrochemical corrosion of buried pipeline, the anticorrosion method of steel pipe also starts from restraining one of them. Add anticorrosive coating on outer wall of pipe. Increase the transition resistance between steel pipe and soil, reduce the corrosion current, and add dc power supply. So that the steel pipe on the soil caused negative potential, the formation of cathodic protection. It can eliminate the negative and positive potential difference. Fundamentally stop the process of Yin and Yang. The combination of anticorrosive coating and cathodic protection is an economical and effective method.
Different methods have different quality and cost. Anticorrosion method and cost should be considered comprehensively according to the pressure, use and environment of the protected steel pipe.
At present, the commonly used external anti-corrosion coatings for gas pipelines mainly include 3PE anti-corrosion steel pipe coatings, epoxy resin powder (FBE) coatings, parrott coatings and red lead coatings. In China, from the durability, maintenance costs and other comprehensive economic factors, generally preferred 3PE anti-corrosion steel pipe. Due to its strong surface hardness, parrott anticorrosion can reduce the damage of scratch and knock against the anticorrosion layer in transportation and construction, and it is widely used in trenchless construction and complex ground mines.