The purpose of this study is to investigate the corrosion behavior of API 5L-B steel in a simulated soil environment (0.1M NaCl+0.1M Na2SO4). The effects of corrosion inhibitors (Na2MoO4 and Hexamine) and coating defects on the corrosion behavior of API 5L-B steel are also studied. The electrochemical impedance spectroscopy (EIS) revealed that the addition of 0.01M Na2MoO4 leads to an increase of R(subscript ct)of the steel. The results from immersion tests of coated steels containing coating defects showed that delimination of coating caused corrosion to extend between coating/substrate interface. Furthermore, the extend of the undercoating corrosion become less severe for the specimens pre-immersed in inhibitor solutions before immersion test in simulated soil environments of pH 7.