Discuss the types of corrosion in oil storage tanks

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(1) Chemical corrosion mainly occurs on the outer wall of the dry tank, and the corrosion is generally mild. (2) Concentration cell corrosion mainly occurs below the liquid level on the inner wall of oil tanks, and is caused by oxygen concentration differences. (3) Galvanic corrosion (i.e., electrochemical corrosion) Electrochemical corrosion is the most common, severe, and harmful type of corrosion on the inner walls of oil tanks; it primarily occurs on the tank bottom, walls, and roof. The cathodic and anodic regions in electrochemical corrosion are formed due to differences in electrode potential caused by factors such as thermal stress and mechanical stress on the material, contact between different metals, and the unevenness of the metal itself (such as composition, microstructure, surface condition, and deposition of corrosion products). Water, oxides, sodium sulfate, calcium, magnesium, and iron salts, as well as hydrochloric acid, sulfuric acid, and hydrosulfuric acid, present in oils, are the main causes of electrochemical corrosion. (4) Corrosion caused by sulfate-reducing bacteria and other bacteria mainly occurs at the bottom of the tank. (5) Friction corrosion mainly occurs at the floating expansion joints of floating roof tanks.