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This post was last edited by Wang Wei2 on 2024-3-23 09:40. Mechanisms of action of several metal anti-corrosion coatings. Anti-corrosion coatings possess advantages such as excellent performance, ease of production, and low cost, which are unmatched by other materials; therefore, they are given priority when choosing anti-corrosion measures. With the advancement of anti-corrosion technology, anti-corrosion coatings will surely see further development as well. Among them, high-solid-content coatings will surely become the trend of development due to their low volatile content, fast curing speed, and good application properties. 1 Epoxy resin coatings: Epoxy resin is a thermosetting resin in which each molecule contains two or more epoxy groups on average. Epoxy resins are widely used due to their ease of processing and molding, as well as the excellent properties of their cured products. By modifying the epoxy structure, creating epoxy alloys, adding inorganic fillers, or using expanding monomers to enhance their performance, anti-corrosion coatings can be produced. Epoxy resin coatings possess excellent physical and mechanical properties, with their strongest feature being their strong adhesion to metals ； It also has excellent chemical and oil resistance, particularly very good alkali resistance. The main components of epoxy resin coatings are epoxy resin and its curing agent, while auxiliary components include pigments, fillers, etc. 2 Polyurethane coatings Polyurethane coatings are coatings that use polyurethane resin as the base material, with pigments, fillers, and other substances serving as auxiliary materials. Polyurethane coatings have strong adaptability to various application environments and surfaces; they can cure at low temperatures, can be applied in humid conditions on wet substrates, and exhibit excellent resistance to petroleum. The main drawback of polyurethane coatings is their high irritancy and toxicity. 3 Flake resin coatings: Metals and certain inorganic compounds are treated using special physical or chemical methods to turn them into thin flakes of a specific size; these flakes are referred to as flakes in engineering terms. Using scales as fillers and synthetic resin as the film-forming substance (adhesive), along with other additives, corrosion-resistant materials can be produced. Scaled resin coatings share the following common feature: good impermeability ； Low contractility ； It has good impact resistance and wear resistance. Currently, there are scale resin coatings made from materials such as glass flakes, mica, corrosion-resistant metal sheets, and organic materials. Experiments have shown that the factors with the greatest impact on the coating are the amount of flakes added and the amount of surface treatment applied. Those that have a significant impact on construction properties are suspended thickeners, reactive diluents, and pigments. 3.1 Glass Flake Coating: A glassflake coating is a type of coating filled with fine flaky glass powder. Its coating can be applied in thick layers, and thanks to the isolating effect of these flaky glass particles, it offers excellent resistance to water, water vapor, electrolytes, and oxygen; thus, it is an outstanding heavy-duty anti-corrosion coating. Unsaturated polyester coatings filled with glass flakes of appropriate specifications have a much lower water vapor permeability than other coatings. The size of glass particle grains has a significant impact on permeability; for example, in the case of a 3μm thick glass sheet, permeability increases significantly when its transverse dimension is less than 420μm ； When it exceeds 420 μm, there is no effect on permeability, and it reaches its minimum value. Furthermore, the thickness of the coating on the glass sheet is also important; to achieve an optimal anti-corrosion effect, the coating thickness must be at least 500μm. 3.2 Mica Flake Coatings Mica is an aluminosilicate; structurally, it belongs to the category of layered silicates. Mica has good chemical stability; it exhibits excellent resistance to alkalis and organic solvents. Studies have shown that, under the same environmental conditions, mica flake unsaturated polyester coatings have similar chemical stability to glass flake unsaturated polyester coatings ； Since resins are not resistant to alkalis, they are also completely destroyed in a sodium carbonate solution with a mass fraction of 20%. A newly developed mica resin film (0.1–1 mm) possesses the characteristics of flake resins while overcoming the inherent defects of such materials. 4 Inorganic zinc-rich coatings: Inorganic zinc-rich coatings are available in both aqueous and solvent-based types. The former is based on sodium silicate, while the latter is based on ethyl orthosilicate. Ethyl orthosilicate is soluble in organic solvents; after application, as the solvent evaporates, the alkoxy groups in ethyl orthosilicate absorb moisture from the air and undergo a hydrolysis reaction, resulting in cross-linking and curing into high-molecular-weight siloxane polymers. The zinc-rich coating is made from ethyl silicate and zinc powder (with a mass content of 70%~90%); the zinc powder provides cathodic protection, which gives this coating good heat resistance, wear resistance, and solvent resistance, as well as strong rust prevention properties. Its drawback is the poor toughness of the coating film, which often requires the addition of some organic resins for modification. 5 High-solid-content coatings: Conventional anti-corrosion coatings typically contain about 40% volatile components, most of which are organic solvents. These solvents evaporate into the atmosphere after the coating is applied, not only leading to defects in the coating layer and making it difficult to meet anti-corrosion requirements but also causing environmental pollution. Therefore, increasing the solid content of coatings and reducing their volatile components have become new directions in coating development. Currently, abroad, anti-corrosion coatings with a very high solid content (up to 95%) have been developed. These coatings possess excellent performance and have been used in oil and gas fields as well as in the hydropower industry, yielding good results.