Microbiological corrosion of buried pipelines

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Microbial corrosion is essentially bacterial corrosion, and it is also a type of electrochemical corrosion. The difference lies in the fact that the medium alters certain physical and chemical properties of the material interface in contact with it due to the reproduction and metabolism of the corrosive microorganisms. There are many types of bacteria involved in bacterial corrosion, among which the most harmful are sulfate-reducing bacteria (SRB). Sulfate-reducing bacteria are bacteria that use organic matter as nutrients and reduce sulfate to sulfides under anaerobic conditions. The SRB genus consists of anaerobic bacteria that require anaerobic conditions to grow; in fact, they can reproduce rapidly in locally anaerobic environments as well. In 1974, Von Wogozen Kuhr and others proposed the classic depolarization theory, suggesting that pitting in buried cast iron pipes is caused by the activity of SBR, which deoxygenates the metal surface through hydrogenases; the overall reaction is as follows: 4Fe + SO42- + 4H2O == 3Fe(OH)2 + FeS + 2OH-