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Objective & Scope
1. Understanding about MIC 2. Establishment of laboratory system for the reliable test of MIC 3. Development of technology for preventing MIC Main Contents The microbial influence on corrosion is now well established, although many of the mechanisms are still not fully understood. Microbially influenced corrosion (MIC) is not a unique form of corrosion, but rather, modified forms of localized corrosion that are enhanced by the action of bacteria. While the mechanisms for the influence of bacteria on the corrosion of mild steel are relatively well established, this is not true for the stainless steels. On reviewing the literature it becomes evident that most of the information on the MIC of stainless steels is based on post analysis of corroded specimens retrieved from the field. There has been very little success with reproducing MIC of stainless steel in the laboratory; successful experiments have relied on other methods to initiate the pitting. A number of recent papers have emphasized the necessity for and action of mixed consortium bacteria in the corrosion process. It is suggested that the failure of many laboratory experiments is due at least in part to the inadequacy of the traditional experimental setup to address the issue of mixed cultures. These traditional methods have relied on a single reaction vessel, operated either as a batch or continuous culture. The inoculation of such systems usually occurs at defined points in time, consisting of either pure characterized cultures or unknown natural consortium. The use of natural consortium or mixed axenic species appears to be preferable, but the inoculation at specific time points will often mean that not all the members of the consortium will grow. This is particularly true for chemostat systems, where the bacteria that colonize mature biofilms are probably washed out of the system before they get a chance to colonize the metal specimen. Such systems fail to replicate nature where the inoculum is most probably present at a continual, albeit low, level. The objective of this study was to develop a method which can rapidly and consistently reproduce Microbiologically Influenced Corrosion (MIC) of stainless steel while that of field test was to identify microorganisms causing the MIC in the actual site. In the laboratory test, four major factors were tested using two types of stainless steel; overall medium composion, dilution ratio, chloride concentration and sulfate concentration. From this study, we isolated and identified a bacterium causing the MIC. The bacterium was Bacillus cereus, which is facultative and has a sulfate-reducing pathway. Related Projects Title : Study about the Microbially Influenced Corrosion Period : 20000301-20010531 Support : POSCO References 1) Establishment of laboratory system for the reliable test of Microbially Influenced Corrosion Pill Joo Kim, Thesis of Master (2002), POSTECH, KOREA |
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