Microbiologically Influenced Corrosion (MIC) was suspected in the corrosion failure of heat exchanger copper piping, carrying groundwater. Laboratory simulation studies were planned to find out the mechanism of
corrosion. Ground water from the same plant was transferred to the laboratory aseptically and used for the experiment. Bacteria in the test solution were activated by the addition of low concentration of nutrients. Both welded and non welded Cu samples were exposed to the test solution. After 2 weeks, a lot of corrosion sites were observed on the surface in the form of pitting. On the other hand, pitting corrosion was not observed on exposure to sterile test solution. Culturing of bacterial strains in the ground water revealed 7 different species. Four of them
were susceptible to microbicidal activity of copper. Rest of them were incubated separately in liquid medium and exposure studies were conducted. Formation of biofilm on copper coupons was observed when they were exposed to the test solution with Stuphylucoccus sp. Under the biofilm, a lot of corrosion sitks in the form of pitting could be seen. Staphylococcus sp. are capable of fermentation of protein and thereby production of ammonia. It is concluded that copper coupons were corroded by ammonia in the test solution. Corrosion mechanism of copper pipe in the ground water is discussed with available literature.
Keywords: Cu, biocorrosion, groundwater, Staphylococcus sp.