Steel bridge has the characteristics of large span capacity, high strength, fast construction speed and short construction period. 1955 The completion of the Wuhan Yangtze River Bridge has made the Wanli Yangtze River stand as the first monument for China people to conquer the Yangtze River. In recent years, with the acceleration of national infrastructure construction, large steel structure bridges have emerged continuously. To build a super-large steel bridge across the river or sea, the steel consumption is generally more than 1 10,000 tons, or even 65,438+10,000 tons. Corrosion, stress corrosion and corrosion fatigue are one of the important reasons why this super-large steel bridge component stops working and reduces its life.

In the 1920s and 1930s, some steel bridges were built in developed countries in Europe and North America. Because the anti-corrosion technology at that time could not provide long-term anti-corrosion protection, these steel bridges were seriously corroded after being put into use, and even if they were regularly painted and maintained, they could not get satisfactory protection, so they had to be downgraded or build another bridge, which caused huge economic losses to the country. 1967, an iron bridge between Happy Point and Noga in the eastern United States collapsed in the Ohio River after 40 years of use, killing 46 people. The investigation shows that the cause of collapse is stress corrosion cracking caused by atmospheric corrosion. Therefore, the corrosion of steel bridges has attracted great attention from all countries. According to 1997, the annual maintenance cost of Wuhan Yangtze River Bridge is more than1000000 yuan, but it is still far from enough. Corrosion not only wastes a lot of manpower and material resources, but also greatly shortens the service life of the bridge.

Anti-corrosion of bridge steel structure has become a topic of increasing concern. Only in the design and construction of steel bridges can effective corrosion protection be carried out to ensure the long life of steel bridges.

2. Historical evolution of anti-corrosion development of bridge steel structure at home and abroad.

In Europe and North America, the anti-corrosion development process of steel bridges is as follows: in the 1940s, paint was used for anti-corrosion; From 1950s to 1970s, heavy-duty anti-corrosion coatings, hot-dip galvanized anti-corrosion, flame spraying anti-corrosion and arc spraying anti-corrosion co-existed. After 1980s, with the development of arc spraying technology, compared with flame spraying, arc spraying has the advantages of higher adhesion between coating and substrate and higher production efficiency, so it has been widely used. At first, more zinc was sprayed, and now arc spraying aluminum is becoming the trend of anti-corrosion development. Heavy-duty anticorrosive coatings containing heavy metal primers and a large number of organic volatiles have caused serious environmental pollution and are basically no longer used in these developed countries.

So far, the corrosion of steel bridges in China is still concentrated on painting. In the 50 years since the founding of the People's Republic of China, the change of anticorrosion technology for steel bridges has mainly focused on adjusting the types of coatings. For example, in 1950s and 1960s, lead-based environmental pollution coatings, mainly red lead antirust paint and mica alkyd topcoat, were used for the corrosion protection of steel bridges, which has always dominated the corrosion protection of steel bridges in China. With the construction of large-scale steel bridges, the anti-corrosion problem has become prominent, and the shortcomings of lead-based coating system, such as poor anti-corrosion durability and high maintenance cost, have become increasingly apparent. In 1980s, heavy-duty anticorrosive coatings were developed, and the anticorrosion life of steel bridges was greatly improved through the matching use of bottom coat, middle coat and top coat. In the 1990s, similar foreign heavy-duty anticorrosive coatings began to flood into the domestic market. Heavy-duty anti-corrosion coatings can only provide the anti-corrosion life of steel bridges 10 years, and it will inevitably face huge anti-corrosion maintenance costs after 10 years, which has been proved by facts in Europe.

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