The anticorrosive coating of buried pipeline includes the whole anticorrosive coating of steel pipe and the joint coating at the welding junction. The main performance includes:
The corrosion of underground pipes with good electrical insulation is an electrochemical process. The corrosion battery circuit is composed of pipes and the surrounding soil. The insulation of the anti-corrosion coating directly determines whether the corrosion current is generated and its value. At the same time, the insulation of anticorrosive coating is also the basic condition to prevent stray current interference and corrosion. The electrical insulation indexes of anticorrosive coating commonly used for pipeline anticorrosion are volume resistivity, surface resistivity, electrical strength and insulation resistance.
2. Adhesion adhesion is the most basic performance of anticorrosive coating. Water vapor and other corrosive media need to contact the metal matrix through the interface between the anti-corrosion layer and the object to be coated. Strong adhesion can maintain the stability of this interface, avoid the accumulation of water vapor under the anti-corrosion layer due to penetration, prevent the accumulation of corrosive media under the anti-corrosion layer, and thus prevent the corrosion under the film and blistering of the paint film.
3. The underground environment of anti permeability pipeline is very complex, and the environment may be very humid or underground water. The low water permeability or low water absorption of the anti-corrosion layer is closely related to the high insulation property of the anti-corrosion layer; the corrosion reaction depends on the penetration and diffusion of the corrosion medium to the anti-corrosion layer. The anti-corrosion layer with good air permeability and anti-permeability can prevent the transmission and supplement of the corrosion medium and effectively prevent various forms of corrosion.
4. Good durability and soil corrosion resistance because the underground pipeline is a semi permanent facility, maintenance and repair are very difficult, and the cost is quite high, so the pipeline anti-corrosion coating must be able to withstand the soil corrosion environment and maintain long-term stability.
5 mechanical strength and soil stress resistance steel pipe from coating construction to installation to underground, is a relatively long process, which may be subject to many mechanical forces, such as collision. Friction, etc., also subject to the effect of changes in ambient temperature, requires the anti-corrosion coating to be impact resistant, wear-resistant and flexible, so as to minimize the damage of the anti-corrosion coating. In cohesive soil, due to the change of dry and wet soil, it will produce stress on the anticorrosive coating; the pipeline will expand and contract due to the change of temperature, which will lead to the shear effect of soil on the anticorrosive coating of pipeline. Therefore, the anticorrosive coating should have the ability of resisting soil stress.
6 the quality of the matching pipeline anticorrosive coating for patching is the sum of the quality of the pipe body anticorrosive coating and the quality of the patching anticorrosive coating. Only good pipe body anticorrosive coating has no reliable patching anticorrosive coating technology, and the pipeline anticorrosive coating also fails. In the production of anticorrosive coating, there may be defects of anticorrosive coating. It is difficult to avoid the damage of anticorrosive coating in the process of pipeline construction, which will affect the integrity of anticorrosive coating. Therefore, there should be a simple and easy way to repair the anticorrosive coating. The repaired anticorrosive coating and the original anticorrosive coating shall be well combined, and the anticorrosive performance shall be equivalent, so that the anticorrosive coating has integrity.
7. Matching with cathodic protection most underground pipelines, especially large-scale pipelines, special ring pipelines need to adopt anticorrosive coating and cathodic protection combined anticorrosive measures.
8. There is a time cycle for the construction of storage stability pipeline. The anticorrosive coating steel pipe may go through a long-distance transportation process, long-time storage and exposed pipe laying, which requires that the anticorrosive coating has stable performance, can withstand the impact of atmospheric environment, resist heat aging and light aging.
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