Causes of Corrosion in Chemical Storage Tanks

(1) Corrosion of the outer wall of the storage tank: The outer wall of the storage tank comes into contact with the atmosphere, and the surrounding environment of the storage tank is generally a petrochemical enterprise. The industrial atmosphere contains harmful gases such as sulfur dioxide, hydrogen sulfide, and nitrogen dioxide. Due to adsorption, condensation, or rain, water vapor or rainwater in the air forms a water film on the outer wall of the storage tank. This water may dissolve acids, alkalis, salts, and other impurities, acting as an electrolyte and causing electrochemical corrosion of the metal surface.

(2) Corrosion of inner wall of storage tank: Impurities in the medium accumulate in the tank for a long time, forming water accumulation. Due to the centerline of the drainage pipe being generally higher than the tank wall, there is always water present at the bottom of the tank. The deposited water contains a large amount of chloride, sulfide, oxygen, acid substances, etc., forming a strong electrolyte solution and producing electrochemical corrosion, causing severe local corrosion at the root of the inner wall of the storage tank.

(3) Corrosion at the fluctuation of tank wall liquid level: Due to the different oxygen content in the medium and the meteorological space above the medium, an oxygen concentration cell can be formed, causing corrosion. Frequent alternation of dry and wet conditions at the liquid level can also lead to the accumulation of sediment, resulting in corrosion under the scale.

(4) Corrosion of tank bottom: One side of the tank bottom is in contact with the medium and the other side is in contact with the soil. The corrosion of the medium side of the tank bottom mainly comes from the sedimentation water in the tank. Sulfides, chlorides, oxygen and other substances in the sedimentation water will react with metals, causing electrochemical corrosion. Due to uneven settlement of the storage tank, the bottom plate may fluctuate or have a stepping phenomenon. Poor contact between the tank bottom plate and the foundation can lead to uneven inflation of the soil at the bottom of the tank, resulting in the formation of oxygen concentration batteries and corrosion of the tank bottom plate