Causes of corrosion on the lower surface of the oil storage tank bottom plate and protection measures

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Causes of Corrosion on the Lower Surface of the Oil Storage Tank Bottom Plate and Measures for Protection I. Causes of Corrosion 1. There is no anti-corrosion coating near the welds on the bottom plate; the areas with coatings around the welds are also damaged during welding, resulting in a corrosive anode that accelerates the corrosion of the bottom plate； 2. Typically, the bottom plate of an oil tank is seated on concrete ring beams; the high potential of the concrete and rebar creates a corrosion cell with the steel bottom plate of the tank, accelerating corrosion ； 3. The impact of the hydrolysis of insulation materials on corrosion: Most insulated oil tanks use rock wool as the insulation material, while a smaller number use polyurethane for this purpose. The pH values of these two materials when exposed to water are 6.4 and 5 respectively; both are acidic and therefore highly corrosive. Once water penetrates the insulation layer that contains cracks, especially during rainy days, rainwater and accumulated water will flow down along the tank walls into the bottom of the tank, creating a humid environment conducive to corrosion. This accelerates the corrosion of the tank bottom and causes ongoing damage to it over time. II. Protective Measures: Before installation, the bottom plate of the storage tank is first coated with an anti-corrosion paint to prevent corrosion. For areas of the bottom plate welds where coating for corrosion protection is not possible, cathodic protection can be used. For the protection of the bottom plates of storage tanks in a tank farm, cathodic protection with current supply can be used; for the protection of individual storage tank bottom plates, the sacrificial anode method can also be employed.