Chapter 7 : Microbially Influenced Corrosion of Steel

Abstract:

This chapter presents traditional and new concepts on the microbially influenced corrosion (MIC) from the microbiological viewpoint. Many review articles on microbially influenced corrosion take the viewpoint of metal destruction. It also investigates corroding iron as a food source for hydrogen-consuming bacteria. Some calculations are presented to visualize quantitative aspects of this economically important process. The process of corrosion is best known as rust formation of steel when in contact with oxygen and water. In this process, oxygen is the oxidizing agent responsible for accepting the electrons from metallic iron. In the absence of oxygen, iron is usually much more stable. However, in oxygen-free environments that are rich in anaerobic microbial activity, particularly with active bacterial sulfate reduction, iron is repeatedly found to deteriorate at high rates, sometimes higher than those due to oxygen alone. In anaerobic environments, organic material is broken down by different groups of bacteria, with molecular hydrogen being one of the most important fermentation end products. The chapter states that mechanisms other than bacterial hydrogen consumption must be responsible for the steel destruction in the presence of anaerobic bacteria. The ability of bacteria to supply protons to the metal surface is discussed in the chapter. The chapter is concerned with the ability of microbes to stimulate the overall corrosion rate. In future research on MIC in the petroleum industry, new capacities and the oil degradation capability of sulfate-reducing bacteria (SRB) will have to be considered.