Concrete, bacterial corrosion

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. 

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. 

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.)... 

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. 

Corrosion of concrete by bacteria that oxidize sulfur compounds into sulfuric acid was reported by Parker (1945, 1947) and has been examined more recently by Fjerdingstad (1969). The lowest pH is tolerated by Thiobacillus concretivorus Parker (pH 2.75 + 0.42) and T. thiooxidans Waksman and Joffe (pH 2.35 0.32). Within 100 days of incubation in a T. thiooxidans culture, 60% of a 3.6 g block of concrete were dissolved. Bacterial destructive activity has also been established on buildings and monuments (Krum-... 

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Milde K, Sand W, Wolff W, Bock E (1983) Thiobacilli of the concrete walls of the Hamburg sewer system. J Gen Microbiol 129 1327-1333 Millard SG, Gowers KR, Bungey JH (1995) Galvanostatic pulse techniques a rapid method of assessing corrosion rates of steel in concrete structure. NACE International Corrosion, Houston Miller JDA (1970) Microbial aspects of metallurgy. Elsevier, New York, pp 61-105 Mills AL, Powelson DK (1996) Bacterial interactions with surfaces in soils. In Fletcher M (ed) Bacterial adhesion molecular and ecological diversity. Wiley-Liss, New York, pp 25-57... 

Thermoplastic pipe has an exceptionally smooth pipe wall. This results in its excellent flow capacity. Thermoplastic pipes have less drag, less tendency for flow turbulence, no corrosion, and are less susceptible to deposits or bacterial growth. Because of its excellent flow properties, a smaller diameter pipe can often be specified to carry a given volume when compared with steel, cast iron or concrete. 

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