Corrosion microbiological

Measurement of some of these parameters identifies the risk of a particular type of corrosion, for example pH measurements assess the risk of acid attack and redox potential measurements is used to assess the suitability of the soil for microbiological corrosion, a low redox potential indicates that the soil is anaerobic and favourable for the life cycle of anaerobic bacteria such as to sulphate-reducing bacteria. Other measurements are more general, resistivity measurements being the most widely quoted. However, as yet no single parameter has been identified which can confidently be expected to assess the corrosion risk of a given soil. It is therefore common practice to measure several parameters and make an assessment from the results. 

Booth, G. H., Microbiological Corrosion, M B Monographs, Mills and Booth Ltd., London (1971)... 

M. Elboujdaini and V. S. Sastri. Field studies of microbiological corrosion in water injection plant. In Proceedings Volume. 50th Annu NACE Int Corrosion Conf (Corrosion 95) (Orlando, FL, 3/26-3/31), 1995. 

Corrosion General corrosion, crevice corrosion, pitting, hydrogen damage, caustic corrosion, intergranular corrosion, microbiological corrosion... 

Localized biological corrosion of stainless steels. There are three general sets of conditions under which localized biological corrosion of austenitic stainless steel occurs (Figure 6.29). These conditions should be examined for metals that show active-passive corrosion behavior. Microbiological corrosion in austenitic steel weldments has been documented. (Wahid)61, (Krysiak)14... 

By their designation, inhibited films can be subdivided into those protecting metals against electrochemical or microbiological corrosion. As a rule, under service conditions, corrosion processes, whether atmospheric, soil or water, go hand in hand. A number of Cl used as modifiers of polymer films combine the properties of inhibitors of both electrochemical and microbiological types of corrosion [7,54]. 

The inhibited polymer films may simultaneously present a barrier for electrochemical and microbiological corrosion. Table 2.11 and Fig. 2.43 illustrate data from [5, 6, 54] characterizing the capability of PE films containing Cl of the PHC series to inhibit vitality of microscopic fungi and bacteria whose metabolic products evoke corrosion damage of metals. 

The water at the bottom of the tank can cause microbiological corrosion because of the presence of acid-producing and sulfate-reducing bacteria (SRB). Under suitable conditions, the SRB damage steel by reducing sulfates in the crude oil to sulfides, leading to pitting corrosion in the areas under the SRB colonies. 

The main problem is the external problem, mainly due to the corrosive nature of the soil. Across the pipeline route, the soil can be soft mud, hard mud, rocks, sand, sand with minerals, moisture, and other environments such as marshy lands, brackish water, seawater, and so forth. Ordinary steel with several compositions, shown in Table 8.1, shows severe corrosion, general corrosion, pitting, and so forth. One kind of serious corrosion problem that takes place is microbiological corrosion, which occurs due to presence of sulfate-reducing bacteria (SRB). They convert sulfate in soil to sulfide, which attacks steel, causing severe pits. Thus, external corrosion is taken care of by a combination of a good coating and cathodic protection. Let us now deal with internal and external corrosion in more detail. 

Williams, D.F. (1985) Physiological and microbiological corrosion. CRC Critical Reviews in Biocompatibility, 1(1), 1-24. 

Microbiological corrosion is more often found in hot countries, but it also occurs in tanks, such as fuel tanks. Fungus enters through the ventilation system or with the fuel and grows inside the tank. This leads to leakage and can result in structural failure. 

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