Comparison of Long - term Corrosion Protection Technology for Steel Structure
Large steel structures, such as bridges, hydraulic structures, towers, chemical tanks, pressure vessels and other preservatives, especially long-term preservative treatment (15-20 years) can have a variety of options. Such as hot-dip galvanized or aluminum technology, heavy duty coating technology, thermal spray zinc or aluminum coating technology. Among them, the most suitable is thermal sprayed aluminum or zinc (plus sealing layer) coating.
It is assumed that the life span of the steel structure used in harsh conditions is 20 years. The life span of the Zn or Al thermal sprayed coating is 20 years. The coating of organic coating takes 3 years and needs nearly 7 times in 20 years. Other losses caused, such as business suspension. Therefore, it can be concluded that the thermal spraying Al or Zn coating is priced at 4 ~ 6 yuan / year · m2 with an average of 5 yuan / year · m2, while the organic coating is 1.7-27 yuan / year · m2 with an average value of 14.35 Yuan / year · m2, thermal spraying long-term anti-corrosion technology about 3 times.
Loss due to coating failure during retiring periods (20 years) is substantial. For example, the Gezhouba project over the gate and the gate to enhance the gate with a large gantry crane steel structure, lift the steel structure. The original paint anticorrosive 2-3 years overhaul once during each overhaul, reducing the daily navigable capacity of 20 vessels, a total reduction of nearly l200 vessels navigable capacity, an average of 400-600 a year, causing great losses to the shipping of the Yangtze River . Therefore, the Three Gorges Project important hydraulic gates, Huang Baoxi Bridge and Xiaolinki Bridge need to use thermal spraying
Al or Zn coating for protection.
In terms of the comprehensive pricing of integrated engineering users, compared with paint coating technology and hot-dip technology, long-term anti-corrosion technology with thermal spraying has high performance-price ratio.
In the 1950s, arc spraying technology had been applied in the field of steel structure manufacture and maintenance in many countries. However, arc spraying was considered as an efficient and low-quality thermal spraying due to the technical limitations of arc spraying equipment at that time. method. Until the 1960s and 1970s, the United States, Germany and some other industrialized countries carried out comparatively great transformation of the arc spraying equipment, which greatly improved the quality of the coating and promoted the universal application of arc spraying technology in the manufacture of steel structures. In the 20th century In the late 1990s, arc spraying technology became one of the most rapidly developed thermal spraying technologies in recent years.
For example, Norwegian Offshore Oil Platform with a total weight of 2,300 tons built by Dalseide & Floysand in Norway in recent years employs 14 G35-LD / U3 spraying equipment for the entire arc spraying and 35 tons of AlMg5 wire for 3 months for 100 spraying workers. It is one of the larger models in the world for long-term preservation of thermal spraying. Long-term preservation of petrochemical pipelines also use a thermal spray anti-corrosion technology Of course, the application of thermal spraying technology construction, there is a certain amount of noise and dust. For the steel factory when the production of environmental requirements are quite strict, and the current installation of the old or the late steel construction maintenance of the basic no high requirements, but must strengthen the protection of construction workers.