Detection and Identification of Microbially Influenced Corrosion (MIC) in Steels

摘要

The causes of exceptionally high localized corrosion rates in steels may be difficult to diagnose. In recent years the cause has commonly been ascribed to microbially-influenced corrosion (MIC). This paper looks at two water-bearing piping systems, one stainless steel, the other carbon steel, and uses them to develop criteria by which MIC could be recognized.Corrosion in the stainless steel piping was taking place at or near welds, producing through-wall penetration of 0.25-inch (～6 mm) thick piping in six months; Micromorphology of the corrosion sites, plus their location with respect to the weld, allow identification of the process as MIC.Corrosion in the carbon steel pipes took place hidden from view in joints made with Victaulic-couplings.. On opening the joints it was found that corrosion had eaten away as much as one quarter inch of schedule 20 steel at the ends of the pipe. The system had already been shut down and dried out, making traditional culturing of the microbes in the joints impossible. Polymerase chain reaction techniques were used to recreate the DNA of the bacteria responsible for the corrosion, allowing their identification by sequencing.