Anti-corrosion methods for the inner wall of oil tanks

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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 resulting from microscopic inconsistencies within 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. The coating applied to oil product storage tanks to provide antistatic and corrosion protection differs significantly from the requirements for other industrial coatings; it must meet two criteria: first, in addition to antistatic properties, it must also have excellent rust prevention 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 layer 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 100μm) + conductive anti-corrosion topcoat (applied by brushing or spraying in 2–3 coats, with a thickness of 100–150μm). The primer in this solution 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 of this solution is composed of special resins, special pigments, and conductive fillers, and it possesses excellent antistatic and anti-corrosion properties.