Corrosion is the dissolution of materials of construction by their environment The resulting of metal deterioration by microorganisms is known as biocorrosion or microbially influenced corrosion (MIC). The industries most affected by MIC are power generations, cooling towers, storage and water distribution systems. A open recirculating cooling tower is a system necessary part of any industrial processes. In such a system microbial growth could be very high due to the presence of nutrients, favourable temperatures and large ratio of surface area to the volume.
Sulphate reducing bacteria (SRB) are the microorganisms most closely identified with MIC. SRB use the sulfate ions as the terminal electron acceptor and produce corrosive hydrogen sulphide (H2S).
Galvanized steel is usually used in the construction of cooling towers because of its high resistance to biofauling and corrosion.
The aim of our study is to conclude the corrosion of galvanized steel occured by SRB in cooling tower and also recognize the effects of biological parameters on MIC.
The experiment was planned to investigate the enumeration of SRB, aerobic and anaerobic heterotrophic bacteria (HB), corrosion rate measurement and carbonhydrate analysis of extracellular polysaccharide substances (EPS) from galvanized steel coupons located in cooling tower every month.
The results of analysis showed that SRB, aerobic and anaerobic heterotrophic bacteria grew and formed a biofilm layer on the galvanized steel coupons, and also microorganisms are responsible from the microbiological corrosion of galvanized steel.