Bacterial corrosion

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. 

The importance of MIC has been underestimated, because most MIC occurs as a localized, pitting-type attack. In general this corrosion type results in relatively low rates of weight loss, changes in electrical resistance, and changes in total area affected. This makes MIC difficult to detect and to quantify using traditional methods of corrosion monitoring [1447]. 

To adequately address MIC problems, interdisciplinary cooperation of specialists in microbiology, metallurgy, corrosion, and water chemistry is required. Because the complexities of MIC are so great, one single technique cannot provide all the answers in terms of corrosion mechanisms. 

The problem of and importance of MIC was not fully realized until recently. Even in the mid-1980s the statement was made that The major problem encountered by the petroleum microbiologist working in the North Sea oil fields is that of convincing the oil field engineer that bacterial corrosion is a subject worthy of serious attention.  

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Figure 4-459. Diagram of the bacterial corrosion of steel or iron by Desulfovibrio bacteria (corrosion products are underlined). (From Ref. [208].)...

Sulphate in general appears to behave very similarly Hatch and Rice have shown that small concentrations in distilled water increase corrosion more than similar concentrations of chloride". In practice, high-sulphate waters may attack concrete, and the performance of some inhibitors appears to be adversely affected by the presence of sulphate. Sulphates have also a special role in bacterial corrosion under anaerobic conditions. Both sulphates and nitrates are acceptable in low-pressure boiler feed water as they are believed to be of value in controlling caustic cracking. 

Oxidation-reduction potential Because of the interest in bacterial corrosion under anaerobic conditions, the oxidation-reduction situation in the soil was suggested as an indication of expected corrosion rates. The work of Starkey and Wight , McVey , and others led to the development and testing of the so-called redox probe. The probe with platinum electrodes and copper sulphate reference cells has been described as difficult to clean. Hence, results are difficult to reproduce. At the present time this procedure does not seem adapted to use in field tests. Of more importance is the fact that the data obtained by the redox method simply indicate anaerobic situations in the soil. Such data would be effective in predicting anaerobic corrosion by sulphate-reducing bacteria, but would fail to give any information regarding other types of corrosion. 

The forms of corrosion which can be controlled by cathodic protection include all forms of general corrosion, pitting corrosion, graphitic corrosion, crevice corrosion, stress-corrosion cracking, corrosion fatigue, cavitation corrosion, bacterial corrosion, etc. This section deals exclusively with the practical application of cathodic protection principally using the impressed-current method. The application of cathodic protection using sacrificial anodes is dealt with in Section 10.2. 

Thus an effective control of bacteria responsible for these undesired effects is mandatory. Several biocides and nonbiocidal techniques to control bacterial corrosion are available, and procedures and techniques to detect bacteria have been developed. 

In this way, it is possible to explain the initiation and growth of bacterial corrosion pits. 

Reduced injectivity due to formation damage can be a significant problem in injection wells. Precipitate formation due to ions present in the injection water contacting counterions in formation fluids, solids initially present in the injection fluid (scaling), bacterial corrosion products, and corrosion products from metal surfaces in the injection system can all reduce permeability near the wellbore (153). The consequent reduced injection rate can result in a lower rate of oil production at offset wells. Dealing with corrosion and bacterial problems, compatibility of ions in the injection water and formation fluids, and filtration can all alleviate formation damage. 

Hydrocarbon Microbiology biodegradation mechanisms of oil products (gasoline, kerosene, diesel, etc.), pyrolysis, polycyclic aromatic hydrocarbons, chlorinated solvents, and ether fuels refining processes (e.g., oil product microbial desulfurization) and oil production processes (e.g., bacterial corrosion). 

Electrochemical testing and determination of polarization characteristics of every component are recommended. If one of the metals has active-passive behavior, the state of the contact material should be considered for the expected active and passive states. Both Pourbaix pH diagrams and the potential of the passive metal or alloy can be helpful for this purpose. Bacterial corrosion in case of intended media and conditions should be investigated. 

In the corroded concrete, there also reside acidophilic iron-oxidizing bacteria (see below) besides the usual sulfur-oxidizing bacteria. The acidophilic iron-oxidizing bacteria show optimal growth pH at 2.0, and oxidize not only ferrous iron but also sulfur compounds. Therefore, they can participate in the corrosion of concrete. We have to consider the action of both the usual sulfur-oxidizing bacteria and the acidophilic iron-oxidizing bacteria when we exploit the compounds which inhibit the bacterial corrosion of concrete. 

Most university efforts on electrochemical corrosion are located in materials and metallurgy departments. As with the situation in chemical engineering, only a small number have formal programs in this area. In addition, curricula in materials science and engineering offer little or no exposure to organic chemistry, an essential element in the understanding of corrosion inhibitors and bacterial corrosion. 

T. Dumas, Calcium aluminate binders an answer to bacterial corrosion , Proc. Symp. Corrosion... 

M. Bibb, Bacterial corrosion in the South Africa power industry. Biologically Induced Corrosion 86, NACE International, Houston, Tex., 1986. 

Aerobic organisms near the outer surface of the film consume oxygen and create a habitat for the SRB at the metal surface (52) (Fig. 1.13). The accompanying flora delivers the nutrients SRB need such as acetic and butyric acids and consumes the oxygen that is toxic for SRB. Sulfate-reducing bacterial corrosion is encountered in... 

FIGURE 4.32 Schematic presentation of possible nonbacterial and bacterial corrosive reactions involved in the biodeterioration of concrete by SOB. (With kind permission from Springer Science+Business Media Microbiologically Influenced Corrosion—An Engineering Insight, 2008, Javaherdashti R.)... 

Y. Matsumura, K. Yamada, M. Takahashi, Y. Kikuchi, T. Tsuchido. Properties of bacterial corrosion of stainless steel and its inhibition by Protamine coating. Biocontrol Science, Vol. 12, No. 1, pp. 21-29, 2007. 

This chapter has discussed the mechanism of what happens at the steel surface. The chemical reactions, formation of oxides, pitting, stray currents, bacterial corrosion, anodes, cathodes and reference electrode potentials (half cells) have been reviewed. A more detailed account of the electrochemistry of corrosion and corrosion of steel in concrete is given in Appendix B. Chapter 3 will discuss the processes that lead to the corrosion and the consequences in terms of damage to structures. We will then move on to the measurement of the problem and how to deal with it. 

Bacterial corrosion n. A corrosion, which results from substances (e.g., ammonia or sulfuric acid) produced by the activity of certain bacteria. Baboian R (2002) Corrosion engineer s handbook, 3rd edn. NACE International - The Corrosion Society, Houston, TX. 

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