Discuss the corner corrosion at the bottom of oil storage tanks
Thread Content
Due to the continuous operation of the storage tank, the edge of its foundation is higher than the bottom plate of the tank. As a result of long-term use, rainwater flows directly along the tank walls into the bottom plate of the tank; remaining there over time, it causes corrosion and damage to the bottom feet of the tank. Furthermore, the insulation material on the outer wall of the tank is mostly rock wool or ultra-fine glass wool, while the outer protective layer is made of cement asbestos ash or galvanized iron sheet. Due to long-term exposure to the atmosphere, the outer protective layer has cracked; in particular, the wall panels at the bottom corners of the tank’s outer wall, about half a meter away from those areas, are severely damaged. It is manifested as large areas of the asbestos-gray protective layer peeling off, leaving the insulation completely exposed to the atmosphere. There are occurrences of perforations and leaks in the tank walls. Based on the surface corrosion condition, the thickness of the rust product is approximately 3–5 mm; beneath the rust layer are corrosion pitting or pitted areas of varying sizes. During the welding and assembly of the oil tank bottom plate, it bonds tightly to the asphalt sand layer; however, after water filling for pressure testing and once the tank is put into use, the tank foundation usually experiences some degree of settlement. When the oil in the tank is depleted, the bottom plate has poor contact with the underlying asphalt sand, and an oxygen concentration difference corrosion occurs at the center and edges due to their different permeability; the center area with lower permeability acts as the anode and is thus corroded. Leakage occurred at the bottom plate of the storage tank during use. Under normal circumstances, corrosion on the lower surface is concealed; once it occurs, it is difficult to detect and repair. This unreasonable structure needs to be addressed urgently.
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Long-term use of oil storage tanks can cause severe corrosion at the tank corners. This is mainly because the relatively high tank foundation allows rainwater to flow into the tank bottom; once the insulation layer is damaged, exposure to the atmosphere accelerates the corrosion process. Furthermore, poor bonding between the tank bottom plate and the foundation, as well as oxygen concentration difference corrosion, can also lead to corrosion of the tank bottom. Especially when the oil level drops, the bottom plate is more prone to leakage and damage. This type of corrosion is often difficult to detect and repair in a timely manner, requiring structural improvements to address it. .