Abstract
Steel structure of oil tanks is one of engineering components susceptible to biocorrosion phenomenon associated with the microbiological activities that induced corrosion known as Microbiological induced corrosion (MIC). The bacteria most frequently associated with corrosion failure of steel are those generate sulphides and these are commonly called Sulphate-Reducing Bacteria (SRB). The forms of corrosion promoted by the SRB are pitting, crevice, stress corrosion cracking, enhancement of corrosion fatigue, and hydrogen embrittlement. Consequently, corrosion progressing can deteriorate engineering materials and cause structure complete failure. Therefore, this paper discusses the mechanisms of biocorrosion in terms of SRB, and its effect on steel structures of oil storage tanks. To understand the causing of SRB, several mechanisms, causes, and effects on the steel structure are described. The study shows that environmental conditions preferred by SRB include zero dissolved oxygen, water and presence of soluble organic nutrients are available in oil content which assist the corrosion process to develop. It is shown that most cases of corrosion related to SRB are associated with a severe localized pitting attack, particularly on the bottom shell of oil storage tanks. This is due to the combined sulfate reduced with hydrogen resulting in chemical compounds such as hydrogen sulphide (H2S) that react with the steel surface producing corrosion products such as ferrous sulphides or ferrous hydroxides, eventually causing metal loss in the form of pitting corrosion.