A brief discussion on the corrosion of oil storage tank interiors and protection methods

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A brief discussion on the corrosion of the inner wall of oil storage tanks and its prevention methods. The following types of corrosion occur on the inner wall of oil tanks: concentration cell corrosion, which mainly takes place below the liquid level on the inner wall of the tank, as a result of differences in oxygen concentration. Galvanic corrosion (electrochemical corrosion) is the most common and harmful type of corrosion, occurring primarily at the bottom, walls, and top of tanks. The anodic and cathodic regions in electrochemical corrosion are formed due to potential differences caused by factors such as the microscopic heterogeneity of the material itself, while water, salts, acids, etc. present in the oil are the main causes of electrochemical corrosion. Corrosion caused by sulfate-reducing bacteria and other bacteria mainly occurs at the bottom of the tank. Friction corrosion mainly occurs at the floating expansion joints of floating roof tanks. Coating anti-static and anti-corrosive coatings on oil product storage tanks requires different standards from those applied to other industrial coatings; it must meet two requirements: first, in addition to anti-static properties, it must also have excellent rust-preventing capabilities for steel ； The coating inside the tank is in contact with petroleum products, and this environment facilitates the penetration of corrosive agents through the paint film to corrode the steel, more so than an atmospheric environment ； Second, it must be able to withstand immersion in petroleum products throughout the year, without contaminating the oils or causing them to deteriorate. The typical anti-static and anti-corrosion coating scheme for the inner walls of oil storage tanks is: epoxy zinc-rich primer (applied by brushing or spraying in 2 coats, with a thickness of 100 μm) + conductive anti-corrosion topcoat (applied by brushing or spraying in 2–3 coats, with a thickness of 100–150 μm). The primer is composed of modified epoxy resin, zinc powder, and a high-performance curing agent. It uses the principle of sacrificial anode protection to prevent corrosion, with the zinc powder releasing electrons to prevent iron from corroding. This primer dries quickly, has excellent impermeability, outstanding corrosion resistance, and strong adhesion, making it suitable for use in tank farm environments. The topcoat is composed of special resins, special pigments, and conductive fillers, and it possesses excellent antistatic and anti-corrosion properties. Generally, such a supporting solution can be used for over 6 years.