External Corrosion of the bottom plate of Petroleum and Derivative Storage tanks on Compacted Soils

Inspections carried out on petroleum and derivative storage tanks on compacted soils have shown external corrosion on the bottom plates of the tanks despite cathodic protection by an impressed current. The holes or cavities in the outer plates of the bottom of the tank (in contact with the soil) result in oil leakage, thereby having significant environmental impacts. The objective of this paper is to show, in laboratory experiments, that cathodic protection is not reliable when there are voids or spaces between the plates and the soil. In addition, it proposes the application of a thermal spray with aluminium in the parts of the bottom plates that are in contact with the soil to protect these plates from localised corrosion. It is important to note that the welding temperature was 320°C, without affecting the aluminium coating applied by the thermal spray.