There are three processes of electrochemical corrosion of buried pipelines, the steel pipe anti-corrosion method of pipe manufacturer Prime Steel Pipe also starts from the process of suppressing one of them. Such as add anti-corrosion coating in the outer wall of the pipeline, which can increase the loop resistance and reduce the corrosion current. Add DC power supply, to form the soil negative potential to steel pipe, will form cathodic protection, which can eliminate the anode and cathode potential difference, fundamentally stop the process get on. But once the anti-corrosion coating is damaged, the exposed iron part will accelerate local corrosion. Therefore, the combination of anti-corrosion coating and cathodic protection is the way to solve the problem, economic and effective. The United States and other countries have clearly stipulated that must use cathodic protection and use anti-corrosion coating at the same time.
But for the urban gas pipeline, due to underground pipe network is intensive, cathodic protection of external power has interfere with other pipes, which will cause their own benefit and other family affected the situation. But using the negative metal material than steel pipe and steel pipe connected to the sacrificial anode protection law does not appear such a situation, therefore, the city gas transmission pipe should be used anti-corrosion coating and sacrificial anode combination of anti-corrosion method. For other low-pressure non-trunk pipe, the general direct use of anti-corrosion coating method.
Currently commonly used the outside anti-corrosion coating by buried gas pipeline mainly are three layers of PE composite structure, epoxy resin powder (FBE), coal tar enamel, epoxy coal tar and PE tape and other five categories. Three-layer PE composite structure, epoxy resin powder coating excellent performance, which is also Europe and the United States buried pipe main anti-corrosion coating. In China, from the durability, maintenance costs and other comprehensive economic considerations, generally choose of three layers of PE composite structure anti-corrosion coating.
In the sacrificial anode protection method, the magnesium alloy is generally used as a sacrificial anode to protect the pipeline. Due to the destruction of the output current, the design life of the magnesium alloy sacrificial anode is best matched with the service life of the pipeline, and neither waste nor increase maintenance costs. However, it should be noted that sacrificial anode protection should not be used when the soil resistivity is too high and the protected pipe passes through the waters.
Different anti-corrosion methods have different anti-corrosion quality and cost, we should be based on the different pressure of the protected steel pipe, different uses and their different environments and different gas delivery, and should comprehensively considerate anti-corrosion methods and anti-corrosion costs. In considering the economic rationality should pay attention to two points:
① Corrosion investment when construct gas pipe network.
② Maintenance costs after the operation of the gas pipe network. As the city gas pipeline network is located in the urban areas, the maintenance is difficult and the cost is high after the operation, it should be appropriate to increase investment to reduce the daily maintenance of the pipeline after the operation of the workload.