Abstract
It is well known that the localized corrosion damage morphology observed in the case of microbiologically induced corrosion (MIC) shows some characteristic features depending on the type of sessile bacteria species. Thus, in the case of sulfate reducing bacteria (SRB) the corrosion damage is reported to manifest itself as wide pits with terraced features. Some strains of acid producing bacteria (APB) cause corrosion damage which show pits within pits or tunneling.
At an operating oil company, a variety of bacteria species (SRB, GAB and GAnB) have been identified in the different types of process waters that are available in the company facilities. Extensive corrosion coupon monitoring as well as fluid and bacteria analyses are routinely conducted by the company and based on years of observation of the corrosion morphology of the coupons, it has been possible to establish a correlation between the characteristic morphological features and the different bacteria species found in the company waters. Thus, the morphology of attack encountered in Effluent Water streams, which often has no SRB species but an abundance of GAnB, appear like serrations (deep scratches) with small craters on the surface. This is distinctly different from the morphology due to SRB attack which appears like terraced pits, typically observed in Brackish Water and Seawater streams. Corrosion and sessile bacteria data from coupons obtained in various types of oil-field process waters over the last few years with corresponding photographic documentation are presented here to show the correlation between the bacteria strain and the morphological features of corrosion damage.
