Small diameter seamless steel pipe for anticorrosion

The anti-corrosion steel pipe is directed to the three processes of electrochemical corrosion of the buried pipeline, and the anti-corrosion method of the steel pipe also starts from suppressing one of the processes. For example, adding anti-corrosion coating on the outer wall of the pipeline can increase the loop resistance and reduce the corrosion current; plus the DC power supply, the steel tube will cause a negative potential to the soil and form a cathodic protection, which can eliminate the cathode-anode potential difference and fundamentally stop the anode-anode process. get on. Anti-corrosion coating rule of law, cathodic protection of the rule of law. However, once the anti-corrosion coating is broken, the exposed iron portion accelerates local corrosion. Therefore, the combination of anti-corrosion coating and cathodic protection is the method of treating both the symptoms and the roots, which is economical and effective. Countries such as the United States have clearly stated that the use of anti-corrosion coatings must be cathodic protection. 
However, for the city gas system, due to the dense underground pipe network, the external power supply of the cathodic protection has great interference to other pipes, which will cause self-benefit and damage to his home. The sacrificial anode protection method that uses a metal material that is negative compared to the steel tube potential does not occur. Therefore, the gas pipeline of the city gas should adopt an anti-corrosion method combining the anti-corrosion coating and the sacrificial anode. For other non-trunk pipes with lower pressure, the anti-corrosion coating method is generally adopted directly. 
At present, the external anti-corrosion coatings commonly used in buried gas pipelines mainly include three layers of PE composite structure, epoxy resin powder (FBE), coal tar enamel, epoxy coal tar pitch and PE tape. The three-layer PE composite structure and the epoxy powder anti-corrosion coating have excellent performance, and thus are the main anti-corrosion coatings for buried pipelines in Europe and the United States [1]. In China, from the perspective of comprehensive economic factors such as durability and maintenance costs, the three-layer PE composite structure anticorrosive coating is generally preferred. 
In the sacrificial anode protection method, a magnesium alloy is generally used as a sacrificial anode to protect the pipeline. Due to the damage during the output current, the design life of the magnesium alloy sacrificial anode is best matched with the service life of the pipeline, which does not waste or 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 pipeline passes through the water.
Different anti-corrosion methods have different anti-corrosion quality and cost. The anti-corrosion method and anti-corrosion costs should be comprehensively considered according to the different pressures of the protected steel pipes, different uses and their different environments and different gas transportation. In consideration of economic rationality, two points should be noted: 1 an anti-corrosion investment during the construction of the gas pipeline network, and 2 maintenance costs after the operation of the gas pipeline network. Since the city gas pipeline network is located in the urban area, it is difficult to maintain and repair after commissioning, and the cost is high. Therefore, an investment should be appropriately increased to reduce the daily maintenance workload of the pipeline after commissioning.