Influence of sulphate reducing bacteria on corrosion rates of buried cast iron pipes

Microbial corrosion is a severe concern for owners and asset managers of buried pipes. Among the various types of bacteria, sulphate reducing bacteria (SRB) are by far one of the most extensively reported in relation to microbial corrosion. The influence of SRB on corrosion rates of buried pipes is a matter of prime significance among researchers due to their peculiar localized impact in the form of pits. Several research studies have been conducted on finding the effects of SRB on buried pipes. However, the literature suggests that these studies are conducted in culture medium where bacteria can easily be grown, but not replicating the soil environment. Hence, a gap exists in finding the influence of SRB in the real soil medium where most of onshore pipelines are buried. This paper presents the outcomes of an innovative experimental setup developed for simulating the external corrosion caused by sulphate reducing bacteria (SRB) for buried cast iron pipes. Coated cast iron specimens with one surface remained uncoated are exposed to SRB in clay soils using well-controlled experimental setup. Results revealed high corrosion rates for the cast iron specimens buried in the soil having SRB compared to the specimens immersed in culture medium as reported in the literature. The experimental approach presented in this paper is first of its kind, and the corrosion rates obtained from the test can be used for accurate prediction of failure of buried metal pipes.