MIC Corrosion Induced by Microorganisms

While there are a relatively large number of culturable types of bacteria whose corrosion impacts are known, perhaps the central bacteria of interest in MIC have been those known as SRB. Corrosion rates of 10 mm/year in oil treatment plants and 0.7 to 7.4 mm/year due to the action of SRB and/or acid-producing bacteria in soil environments have been reported. 

One immediate result of such classification of bacterial states according to availability of nutrients is that, as in almost all experiments that are being carried out under laboratory conditions, the bacteria have all the required nutrients around them, and they may be inclined to prefer planktonic growth over sessile conditions, whereas a great majority of MIC problems come from sessile bacteria, not planktonic ones. This can call into question the reliability of such experiments, especially if one bears in mind the direct relationship between corrosion rate changes and sessile microorganism growth.  

The complexity of confusions about MIC does not end with the various ways of naming it or mixing it up with other corrosion phenomena while it has been stated that there is unequivocal evidence that the observable physical or biochemical characteristics of sessile bacteria are profoundly different from those of their planktonic cousins, it has also been reported that, for example, only 1% of Pseudomonas aeruginosa genes have revealed differential expression in planktonic and biofilm cells. 

FIGURE 4.9 (a) Nutrient-poor bulk solution destiny, (b) Nutrient-rich bulk solution destiny. (From R. Javaherdashti. Microbiologically Influenced Corrosion—An Engineering Insight, Springer, UK, 2008. With permission.) 

There are very interesting features of the sessile bacteria that could be related to corrosion. Some of these interesting points are as follows  

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