Corrosion protection of steel structures

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The field of anti-corrosion technologies for steel structures is vast, with a wide range of products available, and it covers various aspects in industrial, civil, and other sectors. It can be said that wherever there are steel structures, anti-corrosion measures are necessary, and anti-corrosion coatings are used in such situations. With the advancement of various research and development technologies and the constant renewal of products, coating materials, which are essential for the decoration of steel structures and facilities, not only offer diverse functions but also ensure the proper operation of these structures and facilities by extending their service life. They **reduce losses caused by corrosion, save energy, and increase efficiency. Therefore, the development of anti-corrosion coatings for steel structures can reflect certain aspects of infrastructure development and economic levels. Generally speaking, remote areas, locations with clean energy sources, and the interiors of buildings equipped with heating systems are C1 and C2 environments; typical examples include bus stations, subway exits, and airports. Areas with moderate levels of pollution, such as high levels of sulfur dioxide and high environmental humidity, are classified as C3 environments; typical examples include water treatment plants in urban areas, indoor swimming pools, and sports venues. Industrial parks, coastal areas, and pharmaceutical factories can be considered C4 environments; typical examples include hardware factories, foundries, and power plants. The areas where environmental pollution is particularly severe in industrial production zones with high humidity are the C5I industrial corrosion environments; high humidity combined with high seawater salinity constitutes the C5M deep-sea corrosion environment. In the anti-corrosion treatment of steel structures, the process of applying atmospheric anti-corrosion coatings means that the condition of the steel structure’s surface has a direct impact on the lifespan of the coating. Based on actual data, approximately half of all coating failures are attributed to improper treatment of the steel structure’s surface. International standards specify the requirements for surface treatment of steel structures; steel structures whose coatings have failed are no longer suitable for use. Furthermore, due to poor management during the construction process, the workers started applying paint before removing the welding slag after welding was completed. As a result, the quality of the welded joints did not meet the standards; the rough surface and uneven contours led to peeling, rusting, and bubbling of the coating. The coating lost its effectiveness very quickly, and the overall thickness of the coating was insufficient, causing the steel structure to be corroded and damaged. This severely affected subsequent maintenance and repair work on the coating. When using atmospheric anti-corrosion coatings to protect steel structures from corrosion, the lifespan of the coating is often short due to the insufficient durability of the coatings themselves, which makes it difficult to sustain the anti-corrosion protection of the steel structures. To extend the corrosion protection provided by coatings, which have a short lifespan, regular coating maintenance and repairs have become standard practices in steel structure corrosion protection projects. Additionally, it is necessary to select a coating system that meets the expectations regarding repair and maintenance cycles, in order to reduce the long-term costs associated with necessary maintenance. In addition, the lifespan design of the coating must also be based on practical considerations; by referring to relevant cases, the expected lifespan of the coating can be determined in a flexible manner. Professional designers and thorough, comprehensive analysis and comparison are what determine the final choice of coating; a decision cannot be made solely based on professional expertise. The optimal combination of anti-corrosion coatings for steel structures must be determined through long-term practice or by means of technical evaluation. Based on actual cases of anti-corrosion coating applications and their performance, there are still certain patterns to be followed in the use of anti-corrosion coatings for steel structures; that is, the coating should have good adhesion to the underlying surface, as well as between different layers of coating, without any adverse reactions occurring. Additionally, when combining these coatings, it is important to note that coatings with posterior solvents can be used together; weak-solvent coatings can be applied on the surface of strong-solvent coatings, rather than applying strong-solvent coatings on the surface of weak-solvent coatings. In the common process schemes for anti-corrosion coatings of steel structures, coatings with good anti-corrosion and rust-resistant properties, a hard film structure, strong adhesion, and the ability to resist the effects of upper-layer coatings are typically chosen as primers. Coatings that provide good adhesion between the base layer and the upper layers, have a buffering effect, and exhibit similar contraction and thermal expansion characteristics to those of the upper and lower layers are used as intermediate coats. As top coats, anti-corrosion coatings that are hard and durable, have good leveling properties, excellent weather resistance, good corrosion resistance, a high gloss level, and strong adhesion to either the primer or the intermediate coat are selected. The \"two-in-one for the base layer\" or \"three-in-one for the base and middle layers\" in steel structure anti-corrosion coatings are designed to simplify the construction process and reduce labor costs and waste, without compromising the overall performance of these coatings. The author believes it is beyond doubt that the \"bottom-middle-top\" approach in the process scheme for anti-corrosion coatings on steel structures enables each layer to perform its function effectively and work together to achieve the best possible anti-corrosion results; this is especially true for those anti-corrosion coating systems used on important steel structures, which have become standard practices and thus even more undeniable in their effectiveness. “\"Two-in-one\" bottom coating or \"three-in-one\" bottom and middle coating systems for steel structure anti-corrosion purposes are only suitable for simple applications where anti-corrosion is not a top priority. As single, non-combined anti-corrosion coatings, they struggle to meet the various requirements associated with high-level anti-corrosion protection. With the advancement of anti-corrosion coating technology, coatings that offer multiple functions in one product will surely become available, in order to meet market demands such as simplified application processes, environmental safety, and good cost-performance ratios. The traditional interlayer matching of multi-varietal coatings may evolve into a \"formulation matching\" using single-varietal coatings; therefore, how to coordinate the relationships between various components in the coating formulation in order to achieve its best possible performance has become a key technical challenge. Whether it is the coordination among the layers of anti-corrosion coatings for steel structures, or the coordination among the various components in the formulations of anti-corrosion coatings in the future, breakthroughs in key technologies require the joint efforts of researchers working on anti-corrosion coatings, manufacturers of such coatings, and those responsible for applying them. Fortunately, the large domestic market for anti-corrosion treatments of steel structures provides abundant resources for the research and development as well as application of these coatings, offering strong support for overcoming the challenges related to such coordination.