Microbiologically Influenced Corrosion MIC

MIC and the way it affects corrosion have always been a matter of debate. For example, while acid production by bacteria is presumed to be one of the ways by which corrosion can be enhanced, some researchers [2f in their experience with aerobic Pseudomonas sp. have reported that acid production was not a major cause of corrosion, and others [3] have pointed out that the presence of bacteria was not an important factor in the deterioration of steels . It seems that it is not always easy to come up with a clear, once-forever-true explanation of the inpact of bacteria on corrosion. As a matter of fact, such relatively confusing outcomes have helped make MIC a puzzle to some and to others an industrial joke that is used when there is no other explanation for the failure. 

This chapter will deal with MIC, its definition and importance, and how historically both our understanding of and research methods for the study of MIC have evolved. We will then have a look at the parameters that can be used for categorising bacteria, and also the steps involved in biofilm formation. After discussing the ways by which biofilms can both accelerate and decelerate corrosion, we will look at three examples of bacteria that are involved in corrosion, the well-known SRB (sulphate-reducing bacteria), the rather shy , infamous IRB (iron-reducing bacteria) and almost unknown magnetic bacteria. 

This form of corrosion is defined as corrosion influenced by the presence and activities of microorganisms including bacteria and fungi. About 20-30% of all corrosion on pipelines is MIC related. MIC can affect either the external or internal surfaces of a pipeline. Microorganisms located on the metal surface do not directly attack 

The most aggressive corrosive attacks occur in the presence of microbial communities that contain a variety of bacteria. In these communities, the bacteria act cooperatively to produce favorable conditions for the growth of each species. For example, obligate anaerobic bacteria can thrive in aerobic environments when present beneath biofilms/deposits in which aerobic bacteria consume the oxygen. In the case of underground pipelines, the severe attack has been associated with acid-producing bacteria in such bacterial communities (Fig. 4.9). 

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When biofilms are formed on metallic surfaces, they can seriously corrode performance oil production facilities, chemical processing plants, paper mills, ships, and water distribution networks. Microbiologically influenced corrosion (MIC) represents the most serious form of that degradation. 

Bacterial corrosion is often referred to as microbiologically influenced corrosion. MIC involves the initiation or acceleration of corrosion by microorganisms. The metabolic products of microorganisms appear to affect most engineering materials, but the more commonly used corrosion-resistant alloys, such as stainless steels, seem to be particularly susceptible. 

Microbiological fouling, in industrial water treatment, 26 146—149 Microbiologically influenced corrosion (MIC), in industrial water treatment, 26 128-129 Microbiology... 

Active microbiologically influenced corrosion (MIC) of metal due to bacteria is quite complex. It can involve several species of microorganisms and is affected by temperature, TOC, pH, and other factors. Examples of bacterial species which are associated with MIC are described below ... 

Colonies established by microbes on the sidewalls and bottoms of fuel storage tank systems are called plaques. These plaques can often be the site of microbiologically influenced corrosion (MIC) of the underlying metal. 

The black scale was carefully removed to identify the morphology of pits (Figure 7.60). The pits were located at the bottom of a hole (Figure 7.61). The morphology of the pits is characteristic of microbiologically influenced corrosion (MIC). 

Table 7.4 Microorganisms commonly associated with microbiologically influenced corrosion (MIC), generally required environmental conditions, metabolic processes related to MIC, and resultant chemical species that can increase corrosion rates...

Depending on the bacteria and soil conditions which can be described appropriately as an extremely heterogeneous system, these transformations may be assimilatory or dissimilatory metabolic functions. Based on the recent field surveys and laboratory studies, the bacterial-environmental interactions, with reference to the cycles of sulfur and other elements, in corrosion on buried pipes are shown as Figure 1. This Figure demonstrates that microbiologically influenced corrosion (MIC) results from the activities of a microbial community. 

When considering the quality of a material, we also must consider the type of material (e.g., metal, resin, glass, or ceramic, etc.). In particular, metal materials exposed to different weather events may be oxidized and corroded. Here, I will focus on corrosion. Carbon steel, stainless steel, and alloys are considered metal materials, and these different types of steel may be chosen according to the purpose of the material and the environment in which the material will be used. However, changes in the environment will shorten the lifetime of the material, and the presence and activity of microorganisms can accelerate corrosion this process is called microbiologically influenced corrosion (MIC) [1-5]. Thus, when... 

The changes in jet fuel and jet fuel additives that have taken place in recent years have also brought about a shift in the microbial community in aircraft fuel. The bacteria isolated from aircraft jet fuel tanks have been found to be closely related to Bacillus, and they do have the potential to cause microbiologically influenced corrosion (MIC) [11,17,18]. 

Microbiologically influenced corrosion (MIC) is used to designate corrosion resulting from the presence and activities of microorganisms within biofilms on a material surface. Such microorganisms can accelerate and control corrosion reactions by several mechemisms formation of differential or concentration cells, formation of metabolites, such as sulfides md organic and inorganic acids metal oxidation and reduction, and deactivation of corrosion inhibitors. 

McNeil, M. B. and Odom, A. L., Thermodynamic Prediction of Microbiologically Influenced Corrosion (MIC) by Sulfate-Reducing Bacteria (SRB), Microbiologically Influenced Corrosion Testing, ASTM STP 1232, 1994, pp. 173-179. 

Microbiologically Influenced Corrosion (MIC) of the injection and production system. 

Control of MIC. Microorganisms in the injection water and produced water may have the opportunity to attach to metal surfaces in regions of low flow rates. If allowed to form biofilms, the microorganisms could contribute to microbiologically influenced corrosion (MIC) of the injection system. MIC events in the injection system can lead to corrosion failures of pipelines and pumps, with the related problems of equipment downtime, lost production and environmental hazards caused by spills or releases. It is safe to say that the overwhelming purpose of using biocides in the oilfield is to control MIC. 

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