Characteristics of corrosion of steel structures and similar materials in marine and industrial atmospheres, as well as protection methods
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Characteristics of corrosion and protection methods for steel structures in marine and industrial atmospheres 1. Characteristics of corrosion ⑴ Industrial atmosphere: Industrial gases contain components such as SO2, CO2, NO2, Cl2, H2S, and NH3. Although their concentrations are low, these substances can cause significant damage to steel; among them, SO2 has the greatest impact, while Cl2 can destroy the passivation layer on the metal surface. When these gases dissolve in water, they become acidic, forming acid rain that corrodes metal structures. ⑵Oceanic atmosphere: The oceanic atmosphere is characterized by a high content of salts, mainly NaCl. These salt particles settle on metal surfaces; due to their hygroscopic nature and their ability to increase the conductivity of the surface liquid film, coupled with the strong corrosive properties of Cl-, this accelerates the corrosion of the metal surfaces. The closer a steel structure is to the coast, the more severe its corrosion becomes, with its corrosion rate being many times higher than that in inland areas. 2. Common protection methods for large-scale steel structures: Steel structures are often treated with zinc or aluminum spraying, or with corrosion-resistant coatings to create a long-lasting anti-corrosion layer; alternatively, they can be coated with specialized heavy-duty anti-corrosion coatings for protection. To prevent corrosion caused by industrial and marine atmospheres, it has the following features: (1) Thermal spraying of metals; ① The aluminum coating forms a strong bond with the steel substrate, resulting in a long service life of the coating and good economic benefits over the long term ； ②Flexible in application, suitable for long-term protection of important large-scale and difficult-to-maintain steel structures; can be installed on-site ； ③Zinc or aluminum spraying followed by the application of an anti-corrosion coating can **extend the service life of the coating. Both theoretically and in practical applications, zinc or aluminum coatings serve as the best base layer for anti-corrosion coatings. The protective lifespan of a composite coating that combines a metal spray coating with an anti-corrosion coating is longer than the sum of the lifespans of the metal spray coating and the anti-corrosion coating alone, and it is several times longer than the lifespan of a coating applied as a single layer. ⑵Coating layer: A high-performance, long-lasting anti-corrosion coating; it consists of a primer, an intermediate coat, and a topcoat. By using different high-performance coating systems appropriate to various corrosion environments, long-lasting anti-corrosion coatings can be achieved.
The corrosion characteristics of steel structures in marine and industrial atmospheres are different. In industrial atmospheres, gases such as SO2, CO2, NO2, Cl2, H2S, and NH3 can corrode steel materials. Among these, SO2 causes the most severe corrosion of steel, while Cl2 destroys the passivation layer on the metal surface. These gases dissolve in water to form acid rain, which further corrodes metal structures. The marine atmosphere contains large amounts of salts, primarily NaCl. These salt particles deposit on metal surfaces, absorb moisture and increase the conductivity of the liquid film; moreover, Cl- is highly corrosive, exacerbating corrosion on the metal surface. The closer to the coast, the more severe the corrosion of steel structures; their corrosion rate is many times higher than that in inland areas with normal atmospheric conditions. Common protection methods include zinc or aluminum spraying, as well as protection through the application of high-performance anti-corrosion coatings. For steel structures, zinc or aluminum spraying is commonly used; zinc or aluminum is applied to the surface of the steel to form a robust coating that offers a long service life and good economic benefits. This method is suitable for large and difficult-to-maintain steel structures. Additionally, specialized anti-corrosion coatings can be used for protective coating; such coatings generally consist of a primer, an intermediate coat, and a topcoat. Depending on the different corrosion environments, an appropriate high-performance coating system should be selected to achieve long-term corrosion protection. .