Sulfate-reducing bacteria, corrosion

Senez, J. C., "Investigation in Biological Corrosion in Anaerobic Soils by Sulfate-Reducing Bacteria, Corrosion and Anti-Corrosion, Vol. 1, 1953, pp. 131-132. 

Caldwell DE, Wblfriaedt GM, Korber DR, Lawrence JR (1997) Do bacterial communities transcend Darwinism Adv Microb Ecol 15 105-191 Callow ME, Fletcher RL (1994) The influence of low surface energy materials on bioadhesion - a review. Int Biodeter Biodegr 34 333-348 Campaignolle X, Crolet J-L (1997) Method for studying stabilization of localized corrosion on carbon steel by sulfate-reducing bacteria. Corrosion 53 440-447... 

Various patents (22—24) have been issued claiming the use of tetrakis(hydroxymethyl)phosphonium sulfate in, for example, water treating, pharmaceuticals (qv), and in the oil industry where this compound shows exceptional activity toward the sulfate-reducing bacteria that are a primary cause of hydrogen sulfide formation and consequent problems associated with souring and corrosion (25). 

The manner in which many of these bacteria cany on their chemical processes is qmte comphcated and in some cases not fuUy understood. The role of sulfate-reducing bacteria (anaerobic) in promoting corrosion has been extensively investigated. The sulfates in shghtly acid to alkaline (pH 6 to 9) soils are reduced by these bacteria to form calcium sulfide and hydrogen sulfide. When these compounds come in contact with underground iron pipes, conversion of the iron to iron sulfide occurs. As these bacieria thrive under these conditions, they will continue to promote this reaction until failure of the pipe occurs. 

Sulfate reducers. The best-known form of microbiologically influenced corrosion involves sulfate-reducing bacteria.- Without question, sulfate reducers cause most localized industrial cooling water corrosion associated with bacteria. Desulfovibrio, Desulfomonas, and Desulfotomacu-lum are three genera of sulfate-reducing bacteria. 

Corrosion morphologies. Sulfate-reducing bacteria frequently cause intense localized attack (Figs. 6.2 through 6.7). Discrete hemispherical depressions form on most alloys, including stainless steels, aluminum. Carpenter 20, and carbon steels. Few cases occur on titanium. Copper alloy attack is not well defined. 

TABLE 6.3 Typical Microbiological Analysis at Outlet A Main Condenser Suffering No Significant Corrosion by Sulfate-Reducing Bacteria ... 

Figure 6.9 Irregular deposit and corrosion-product mounds containing concentrations of sulfate-reducing bacteria on the internal surface of a 316 stainless steel transfer line carrying a starch-clay mixture used to coat paper material. Attack only occurred along incompletely closed weld seams, with many perforations. Note the heat tint, partially obscured by the deposit mounds, along the circumferential weld.

Scale deposits create conditions for concentration-cell corrosion as they do not form uniformly over the metal surface. Sulfate-reducing bacteria thrive under these deposits, producing hydrogen sulfide and, consequently, increasing the rate of corrosion. Due to the following factors, the drilling fluid environment is ideal for scale deposition [189]. These factors are as follows ... 

Light, sandy, well-drained soil of high electrical resistivity is low in corrosivity and coated steel or bare stainless steels can be employed. It is unlikely that the whole pipe run would be in the same type of soil. In heavier or damp soils, or where the quality of back filling cannot be guaranteed, there are two major corrosion risks. Steel, copper alloys and most stainless steels are susceptible to sulfide attack brought about by the action of sulfate-reducing bacteria in the soil. SRB are ubiquitous but thrive particularly well in the anaerobic conditions which persist in compacted soil, especially clay. The mechanism of corrosion where SRB are involved is described in Section... 

Corrosion of buried structures has been blamed on the sulfate-reducing bacteria (SRB) for well over a century. It was easy to blame the SRB for the corrosion as they smelled very bad (rotten egg smell). It is now known that SRB are one component of the MIC communities required to get corrosion of most buried structures. 

Electrochemical impedance, weight loss, and potentiodyne techniques can be used to determine the corrosion rates of carbon steel and the activities of both sulfate-reducing bacteria and acid-producing bacteria in a water injection field test. A study revealed that the corrosion rates determined by the potentiodyne technique did not correlate with the bacterial activity, but those obtained by electrochemical impedance spectroscopy (EIS) were comparable with the rates obtained by weight loss measurements [545]. 

E. D. Burger, A. B. Crews, and H. W. Ikerd, n. Inhibition of sulfate-reducing bacteria by anthraquinone in a laboratory biofilm column under dynamic conditions. NACE Int Corrosion Conf (Corrosion 2001) (Houston, TX, 3/11-3/16), 2001. 

Hydrogen sulfide promoted corrosion can be a serious problem (150) the best solution is prevention. Corrosion problems can be minimized by choice of the proper grades of steel or corrosion resistant alloys, usually containing chromium or nickel (150, 151) and avoiding generation of H S by sulfate reducing bacteria in situations where H S is not initially present. Cathodic protection of casing is often effective for wells less than 10,000 feet deep (150). 

Bacterial H2 metabolism impacts on human activities in other ways. The corrosion of iron, for example, is accelerated by bacteria, particularly sulfate-reducing bacteria. They do not appear to interact with the iron directly, but with the hydrogen that is produced on the surface of iron in contact with water. For this reason antibacterial agents are used in preservative solutions for heating systems. 

The term sulfate-reducing bacteria (SRB) is frequently used to describe organisms which metabolize organic sulfates in fuel. Upon metabolism, the oxygen bound to the sulfate sulfur is consumed by the SRB and utilized in cellular respiration. The sulfur is reduced to H2S gas. Once liberated, H2S can react with fuel olefins to form mercaptans, contribute to microbial-induced corrosion, or escape into the fuel. 

Organisms such as Thiobacillus thiooxidans and Clostridium species have been linked to accelerated corrosion of mild steel. Aerobic Thiobacillus oxidizes various sulfur-containing compounds such as sulfides to sulfates. This process promotes a symbiotic relationship between Thiobacillus and sulfate-reducing bacteria. Also, Thiobacillus produces sulfuric acid as a metabolic by-product of sulfide oxidation. 

Sulfate-reducing bacteria (SRB) can live in water bottoms of fuel storage tanks. These bacteria can produce growth plaques on metal surfaces and can live in corrosion pits in metal. Hydrogen sulfide is a product of SRB metabolism and can contaminate fuel stored in tanks. 

Where hyperbolic towers are used in process industry, it is not uncommon to find corrosion-inducing, sulfate-reducing bacteria under the silt, or as part of biofilm slimes. Use of problem-specific polymers and biocide programs can be of considerable benefit in these cases. 

Sulfur bacteria Thiobacillus thiooxidans is an aerobic acid- and corrosion-producing sulfur bacterium. Thiothrix sp. are troublesome aerobic slime formers. The most prolific of the slime- and corrosion-producing sulfate-reducing bacteria (SRB) is the anaerobe Desulfovibrio desulfuricans. Other sulfur bacteria include the anaerobes Beggiatoa sp. and Clostridium migrificans. 

Grab, Lawrence A. Theis, Alan B. Comparative Biocidal Efficacy vs. Sulfate Reducing Bacteria. Presented to NACE Annual Conference and Corrosion Show, Paper 184, Corrosion, USA, 1992. 

R.H. Gaines 1910 Sulfate-reducing bacteria in soils produce H2S and cause corrosion... 

Aerobic iron bacteria accelerate the formation of tubercles. The sulfate-reducing bacteria flourish in tubercles and can accelerate the corrosion process. 

Microbially influenced corrosion occurs in soil environment. The sulfate-reducing bacteria (SRB) reduce sulfate to sulfide and as a result iron sulfide is formed due to corrosion. The iron sulfide deposit on the steel surface and the steel form a galvanic couple, which is substained by the removal of electrons in the form of cathodic hydrogen, followed by the further formation of more iron sulfide.19,20... 

Sulfate-reducing bacteria (SRB) have been known to cause corrosion of copper and its alloys and various sulfides have been identified. Some of the sulfides are digenite Cu5S9, chalcocite Cu2S, covellite CuS, djuerleite Cu j 9fiS. 

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