Corrosion is one of the main factors of oil tank failure. Corrosion significantly decreases tank service life and safety.
Speaking of steel tanks, they are prone to uniform, knife, crevice and pit corrosion. The rate is usually from 0.04 to 1.1 mm per year. Pit corrosion is very dangerous, since it can cause formation of openings, losing some of the valuable product. The situation is further aggravated by the fact that the rate of pit corrosion is several times that of other types of corrosion and can reach up to 8 mm per year.
From the construction viewpoint, the weakest part of the tank in terms of corrosion is the bottom. First, it is in constant contact with the liquid stored, second, it is relatively thin. Let us look at the most common ways of protecting storage tanks from corrosion.
Metal corrosion can be prevented by special coatings which isolate the metal from the aggressive environment. The methods are numerous: from paint to applying coats of corrosion-resistant steel or alloy.
Ground protection involves connecting a more electronegative metal to the protected structure. While that metal dissolves in the environment, the main structure is protected. This is, essentially, a case of cathodic protection. Combined coatings, such as metal and paint coating, are also used.