Discuss the main principles of action of anti-corrosion coatings on metal surfaces
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In normal environments, steel structures must be protected, and the most common method is to use coating protection. Generally, anti-corrosion and rust-proof coatings are used. This type of coating provides protection through two mechanisms: —— A barrier effect: On the surface of the steel structure, the coating forms a complete organic film layer that separates the environmental agents (oxygen, water, acids, bases, salts, etc.) from the steel, thereby eliminating the conditions necessary for the formation of \"corrosion cells\" and thus protecting the steel from corrosion. This is a physical mechanism, and its reliability has certain limits. Primarily, organic film layers cannot completely isolate the environment; there are always media such as oxygen and water that can penetrate the steel surface. The ability of these media to penetrate depends on the material of the film and the methods used in its application. On the other hand, over time, the effect of the membrane layer in isolating the environment weakens; therefore, physical isolation alone often cannot effectively protect the steel structure. ——Addition of anti-corrosion components (corrosion inhibitors): This is a unique feature of anti-corrosion and rust-preventing coatings. When a certain amount of a substance known as a \"corrosion inhibitor\" is added to the film-forming material, even if the organic film layer cannot completely isolate the environment and a \"corrosion cell\" has already formed, the corrosion inhibitor can effectively prevent or slow down the occurrence and progression of corrosion in the steel structure, thereby achieving better protective effects. Anodic metal layers (zinc, magnesium, aluminum, etc.) provide sacrificial protection (cathodic protection), while cathodic metal layers (nickel, chromium, etc.) mainly serve to isolate the structure from its environment; once such protective layers are damaged or incomplete, it accelerates the corrosion of the steel.
Thermal spraying coatings can be used to provide a “protective coat” for materials or equipment”
It’s just that the costs are too high and the construction conditions are very harsh
Well, you’re right. But if higher corrosion resistance is required, it could be considered
Anticorrosive coatings protect metal surfaces in two main ways: one is by creating a physical barrier that separates the metal from corrosive elements in the environment, such as oxygen and moisture, thereby preventing the formation of corrosion cells； Secondly, corrosion inhibitors are added; even if the organic layer is partially penetrated, these inhibitors can slow down or prevent the corrosion of the metal. Furthermore, different metal coatings can also provide sacrificial protection or enhance isolation effects. .