PROTECTION OF STORAGE TANKS
Hydrocarbon-based fuels are not corrosive to steel. However, water condenses in the roof and upper surfaces of the fuel storage tanks, trickles down the walls and deposits on the bottom of the tank. As these plants are located mainly on the coast, the air that enters the tank while the tank is being filled with fresh fuel, is highly humid and contains salts from the environment. In addition, personnel in charge of this type of plants declares that part of the water would also come from fuel contamination during handling and shipping. Both situations explain the reason why the water inside the tank is saline. This saline water also has dissolved oxygen, producing a highly aggressive electrolyte. As the upper, bottom and mantle sectors are generally protected up to 1 m in height, the mantle remains unprotected against the action of this electrolyte. Unlike lead fuels, unleaded fuels have a high content of aromatics and other additives that damage and affect the coatings conventionally used in the protection of leaded fuel storage tanks. Hence, the anticorrosive coatings inside these tanks must be highly resistant to unleaded fuels and waterproof. Some specifications consider the application of inorganics rich in zinc for the bottom and lower mantles. Zinc-rich paints are not recommended as a single coating, since the silicate matrix absorbs water and the existing water oxidizes the zinc and releases hydrogen. Conventional epoxy paints must be replaced by epoxy paints resistant to the demands of unleaded fuels. Due to these new market demands, the design of an anticorrosive protection system should include 3 layers of paint resistant to unleaded fuels, to water condensation in the upper sectors of the tanks and to the water deposited on the bottom of the tanks. water should be considered. in the background of these. The outside of the tanks must be protected according to the environment. Regardless of the outer protection of the mantle and roof, the outer bottom of the tanks must be protected with an adequate cathodic protection system.