The role of coating anti-corrosion layers in steel structures
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This post was last edited by Wang Wei2 on 2026-1-27 at 08:16. Anti-corrosion coatings for steel components can be applied in various ways depending on the specific circumstances, such as metal protective layers (e.g., galvanizing), paint coatings, or composite protective layers (i.e., the use of both types of coatings simultaneously). The common method for preventing corrosion in steel structures nowadays is applying anti-corrosion coatings. Paint is an oily or non-oily colloidal solution. When applied to the surface of steel, it forms a thin film that protects the steel structure. Anticorrosion coatings generally consist of a primer and a topcoat. Primers contain a high amount of powder and little binder, resulting in a rough film texture. The function of a primer is to ensure a strong bond between the paint film and the substrate as well as the topcoat, that is, to provide good adhesion ； Primer contains anti-corrosion pigments that can prevent rust from forming; some of them also provide passivation and electrochemical protection for metals, thereby preventing them from rusting. The topcoat contains less powder and more binder; it is glossy after forming a film. Its main function is to protect the underlying primer, so it must be impermeable to air and humidity, as well as able to resist physical and chemical degradation caused by weathering. The current trend is to use synthetic resins to improve the weather resistance of the medium. Anti-corrosion coatings with atmospheric resistance can generally only resist vapor corrosion in the atmosphere. In areas subjected to erosion by acids, alkalis, and other substances, acid- and alkali-resistant coatings must be used. Based on their protective functions, anti-corrosion paints can be divided into primer, intermediate coat, and topcoat. Each layer of paint has its own characteristics and performs a specific role; when combined, these layers form a composite coating that enhances anti-corrosion performance and extends the product’s service life.
Corrosion tests of long-lasting anti-corrosion coatings applied by thermal spraying abroad: In 1953, the Welding Society of America conducted industrial coupon tests on zinc and aluminum coatings applied by thermal spraying over a period of 19 years in three types of environments: industrial environments, seawater environments (partially submerged in still seawater and fully submerged in flowing seawater), and marine environments. A total of 4,248 coupons were used in these tests, and the results showed that both zinc and aluminum coatings, when combined with sealing coatings, could provide effective long-term anti-corrosion protection for steel structural elements in these three types of environments. The world-famous 19-year test report on thermal spraying, AWSC2 14-74, was published as a result of these studies. The performance test reports on anti-corrosion coatings over 34 years in marine atmospheres, prepared by the LAQUE Corrosion Technology Center in the United States, confirm that thermally sprayed zinc and aluminum coatings remain effective in various hostile environments over the long term. Based on these findings, along with data from 19 years of research, the U.S. developed the AWSC2 18-93 guidelines for thermally spraying processes, which serve as a quality control manual for companies engaged in thermally spraying operations, aiming to guide production processes. The U.S. Navy Civil Engineering Laboratory conducted 10-year tests on zinc- and aluminum-coated surfaces with a thickness of 75 μm under marine climate and seawater conditions, and no red rust was observed, proving the effectiveness of these coatings in preventing corrosion. The French Metro Company conducted a 10-year exposure test on zinc and aluminum coatings; the results showed that they are effective in preventing corrosion. Tests on underground mines in Tbilisi, former Soviet Union, show that zinc spraying for corrosion protection provides at least 30 years of corrosion resistance. The test results of different **technicians are consistent. Immediate thermal spraying of zinc and aluminum coatings can both provide long-term and effective protection for steel in marine atmospheres, industrial atmospheres, and seawater environments. These test results were directly used as the basis for formulating standards for thermal spraying anti-corrosion techniques, and they played a key role in promoting the use of thermal spraying anti-corrosion on large steel bridges in developed countries around the world after the 1960s, making a significant contribution to the development of thermal spraying worldwide.