Anti-corrosion measures for long-distance natural gas steel pipelines

In the actual steel pipeline transportation process, in essence, steel pipeline corrosion is a normal phenomenon and cannot be completely avoided. Reducing the impact of pipeline corrosion on natural gas transportation can only be alleviated through the application of corresponding measures, to reduce the pipeline corrosion rate. The anti-corrosion of long-distance natural gas steel pipelines can be studied from two aspects: physics and chemistry. From the perspective of physics, the method of adding coatings is mainly adopted, and from the perspective of chemistry, electrochemical protection measures are mainly adopted. In most cases, the actual pipeline protection will choose to use a combination of physical and chemical protection measures.

(1) Additional coating
The main methods of adding coatings include: first, coal tar enamel. Adding coal tar enamel outside the transportation area is a relatively mature protective measure at this stage. Coal tar enamel not only has a strong anti-corrosion function but also has a certain degree of insulation. Being able to prevent the pipeline from being affected by stray currents plays a very critical role in the protection of the pipeline. Because coal tar enamel has a relatively long service life, its economy is relatively high, and most of them choose it as the main material for adding coatings. In addition, coal tar enamel also has some disadvantages in the process of use, mainly in the following aspects: This technology has a high requirement for pipeline temperature. Once the temperature of the pipeline exceeds the specified temperature of coal tar enamel, It will cause the melting of coal tar enamel, which not only cannot protect the pipeline, but also may cause environmental pollution, and then cannot protect the pipeline. Therefore, in the actual application process, attention should be paid to coal tar enamel. Tar enamel is not suitable for heating delivery piping. Second, the mechanical properties of coal tar enamel are in a relatively poor state, and it is very easy to be disturbed by other high-hardness substances outside. If there are many hard rocks in the nearby soil, it will also have serious damage to the coal tar enamel anti-corrosion layer. damage, in which case coal tar enamel is also not suitable for areas of underground rock hardness.
Secondly, PE two-layer structure. The addition of a PE two-layer structure on the outside of the transportation pipeline is also a pipeline protection measure that has been applied more frequently at this stage. The PE two-layer structure not only has an efficient anti-corrosion function but also has a strong milk bacteria function, which interferes with the bacteria around the pipeline. Can play a strong inhibitory effect. At the same time, the PE two-layer structure also has a strong water absorption capacity, which can largely prevent the impact of moisture in the soil on the operation of the pipeline. The price of the PE two-layer structure is not high, so it is suitable for long-distance natural gas steel pipelines. In other words, it is very suitable, but in its actual application, there are corresponding problems. On the one hand, this kind of material cannot be placed in the sun, otherwise, it will be seriously interfered with by ultraviolet rays, and then lose its protective effect. On the other hand, such materials are not easy to be tightly combined with steel pipelines, so the protective effect will be greatly reduced.
Finally, PE three-layer structure. This PE three-layer structure belongs to the pipeline protection measures produced and also belongs to the most effective protection measures at this stage. Compared with the two-layer structure, the three-layer structure adds epoxy powder in the middle link, which not only improves the corrosion resistance but also provides assistance for the tight combination of the material and the pipeline, so that it can fully exert its protective performance. In addition, due to the epoxy powder contained in the PE three-layer structure, the material will no longer be disturbed by ultraviolet rays and can be used in sunlight.

(2) Electrochemical protection
In the actual electrochemical protection process of long-distance natural gas steel pipelines, the sacrificial anode cathodic protection method is often used. The principle of this chemical transmission pipeline anticorrosion method is very simple. In the actual application process, a metal material that is more active than the metal material used in the pipeline is added to the outside of the transmission pipeline to form a primary battery. In this galvanic cell, the anode is the active metal and the cathode is the pipeline, which will be protected during the actual corrosion phenomenon. In the actual application of such anti-corrosion measures, comprehensive consideration should be given to the length, wall thickness, and environment of the pipeline. Then, the position and weight of the active metal are calculated in detail.

(3) Cathodic protection method with external power supply
In the actual application process, this anti-corrosion method for transmission steel pipelines is applied less frequently, but it is feasible in theory. In the actual application process, the power supply should be increased on the outer wall of the pipeline, so that the pipeline can be efficiently protected. Protect. The reason for the relatively small number of applications is that most natural gas is a flammable and explosive gas. When using this method, a simple calculation of the voltage is also required according to the actual situation.