At the beginning of the 20th century, petroleum asphalt was used as the main anticorrosive material for pipelines. In the 1990s, the number of polyethylene anticorrosive coating used in the world was almost the same as that of epoxy powder and coal tar oil enamel. At the turn of the century, three-layer PE structure and epoxy powder occupied the leading position. At present, the anti-corrosion structure of domestic long-distance pipeline construction is mainly three-layer PE structure, some of which are epoxy powder anti-corrosion structure.
(1) Three layer PE structure and epoxy powder anticorrosive coating
The three-layer PE structure anticorrosive coating and epoxy powder anticorrosive coating in China were introduced from abroad in the 1990s and have been widely used. The so-called three-layer PE structure refers to the anti-corrosion coating formed after the external steel pipe is heated by surface cleaning and derusting, and coated by epoxy powder spraying and adhesive / PE winding; the epoxy powder anti-corrosion coating refers to the anti-corrosion coating formed after the external steel pipe is heated by surface cleaning and derusting, and coated by epoxy powder spraying. At present, most of the domestic anti-corrosion plants are set up in the steel pipe plant. After the steel pipe manufacturing is completed, it will enter the anti-corrosion plant for anti-corrosion operation. 3PE anticorrosive structure is also used at the welding junction, commonly 3PE heat shrinkable tape and 3PE heat shrinkable sleeve.
(2) Inner drag reduction coating
The internal friction reducing coating technology in China was developed on a large scale at the end of the 20th century. It is mainly used in the process of pipeline gas transmission, which can reduce the friction, increase the pipeline throughput and reduce the comprehensive cost of pipeline operation. The main process is to clean the inner surface of the pipe, spray the epoxy coating on the inner surface of the pipe through the high-pressure airless spray gun through the rotation of the pipe, so that the inner surface of the pipe can form a high-quality, continuous and smooth effective coating. The pipeline internal coating line is mainly composed of preheating system, internal rust removal system, internal spraying system and coating curing system.
With the progress and development of long-distance pipeline technology, pipeline anti-corrosion technology is also in progress and development, new anti-corrosion technology and new materials are also constantly being studied.
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