Above ground storage tanks in hydrocarbon process plants which are located in aggressive soil at costal areas, are at a risk from bottom plate corrosion, due to formation of a galvanic corrosion cell between the tank bottom and the soil. This galvanic corrosion cell formation effect is more predominant if the content of the tank is stored at high temperature.
At such situations traditional methods of passive barrier protection systems such as sand bitumen tank foundation pad or soil side paint / coating of the bottom plates cannot prevent corrosion.
Tank leakage due to corrosion poses significant treat for the safety of the plant equipment and personnel due to possibility of occurrences of the fire hazards, if the tank content is hazardous material. The replacement of the bottom plate due to corrosion damage is also found to be costly.
Suitable designed cathodic Protection system using either close or remote anode ground bed supplemented with soil side paint / coating of bottom plate is the appropriate protective measure to ensure the integrity of the bottom plates against soil side corrosion for a longer period.
Aluminium tank anodes are used to complement the coating at areas of exposed steel prolonging the life of the coating and structure. Hydrogen is evolved from aluminium anodes and termite sparking may occur when light alloys impact on rusty steel.