How to construct anticorrosive lining of steel pipeline

　　Aiming at the three processes of electrochemical corrosion of buried pipeline, the anti-corrosion method of steel pipeline also starts from one of them. Therefore, the combination of anti-corrosion coating and cathode maintenance is an economical and useful method. Because of the damage in the process of output current, the service life of magnesium alloy anode is the best, which matches the service life of the pipeline, and it is neither extravagant nor additional maintenance costs. Different anti-corrosion methods have different anti-corrosion quality and cost. The anti-corrosion methods and cost should be considered according to the different pressure, different use, different environment and different gas transported.

　　When the flattening amount is 50 mm, cracks are gradually added to the whole pipe section at the edge. The test results show that "hairy" cracks occur when the flattening amount is 1% of the pipeline diameter. When the flattening amount is 6-9%, the mortar coating begins to crack and falls off when it reaches 30% of the pipe diameter. This will never happen in construction.

　　When the steel pipeline is deformed and flattened under external pressure, the mortar will produce "hairy" cracks, but it is very difficult to peel the mortar from the pipe wall. On the steel pipeline with diameter of DN800mm and wall thickness of 7.1mm, a one meter long pipeline section is cut and lined with 11mm thick mortar coating. When the flattening amount is 7-8mm, the "hairy" cracks can be seen. According to the measurement, the minimum flatness is 15 mm on the DN 1100 pipeline and 21 mm on the DN 1800 pipeline. It can be seen that with the increase of pipe diameter, the flattening amount of cracks will increase. Cement mortar fabric has the following obvious advantages: it can avoid the attack of corrosion and rust on the inner wall of the pipeline, keep the pipeline in excellent water delivery condition for a long time, and has small friction coefficient.

　　There are two ways to construct cement mortar. One is ground centrifugation. It is mainly suitable for the lining construction of pipes with diameter less than dn400. But the underground spraying method is mainly applicable to the underground anti-corrosion construction of DN700 diameter pipeline. Because of the barrier of the fabric coating, the water does not touch the metal pipe, ensuring the water quality. The inner wall of the pipeline is protected by cement mortar, which avoids corrosion perforation and extends the service life of the pipeline. The material selection of cement mortar coating is convenient, the construction period is short, the anti-corrosion effect is good, and the cost of pipeline engineering is reduced. In view of the above advantages of cement mortar, its anti-corrosion function and economy are recognized by more and more engineering and technical departments at home and abroad. Large and medium-sized cities in China are promoting the use of cement mortar as the primary point of internal anti-corrosion of water supply metal pipes.