Microbial corrosion sampling

Biofilm samples and microbial contamination of drinking water flowing through the model in result of biofilm formation were analyses with standard methods (APHA, 1992). Number of heterotrophic bacteria (R2A/22°C/7d) coliforms and bacteria from different physiological groups, including corrosion related bacteria were determined. 

The remote crevice assembly technique (see Chapter 19) is a research tool that allows one to separate the anode and cathode areas of a crevice corrosion test sample so that the current flowing between them can be measured with a zero-resistance ammeter. This technique is similar to the dual cell method, and it lends itself well to studies of microbial effects on crevice corrosion [7]. It allows direct measurement of microbial effects on both the initiation time and propagation rate for crevice attack, provided again that a suitable control experiment without the microbial influence can be done concurrently. The scime technique of separating the anode and cathode can be used to study the influence of microbes in biofilms on galvanic corrosion [li]. 

SRB have been implicated in localised pitting corrosion, commonly referred to as microbially influenced corrosion (MIC). These and other anaerobes cause biocorrosion due to production of adds and other by-products (e.g.hydrogen sulphide), that cause cathodic depolarisation of metal surfaces. SRB also cause discoloration problems and production of foul odors. They are susceptible to bioddes, and can be controlled. Many other types of anaerobes may be present in the mill system, including the common helical-shaped, motile bacteria Spirillum. These corkscrew-shaped anaerobes are often seen under the microscope swimming in deposit samples and soured stock. 

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