1996 Volume 45 Issue 10 Pages 595-602
Carbon steel was exposed for long time to an inoculation medium of sulfate-reducing bacteria (SRB). The corrosion behavior was investigated by measuring weight loss of the specimens and by using surface-analytical methods such as EPMA. In the medium containing ferrous ions of high concentration (0.01mol kg-1), the corrosion rate of carbon steel took a maximum value. The weight loss increased linearly with time after exposure above four weeks, although the weight loss was insignificant during the exposure up to four weeks. The corrosion rate in the medium containing ferrous ions of 3.6×10-4mol kg-1 and 0.3mol kg-1 was not so large as that in the medium containing ferrous ions of 0.01mol kg-1. The activity of SRB as well as the corrosion rate depended strongly on the concentration of ferrous ions. The EPMA results suggested that the some area of steel surface covered with the scale would act as a cathode and the other area would act as an anode. The formation of effective cathode area was closely related to the formation of FeS and dependent on the exposed time. Even if an antibiotic was added into the medium after exposure of two weeks, the corrosion did not cease and increased linearly with time after exposure above four weeks. Thus it is found that the contribution of SRB to the corrosion is associated with the creation of corrosive environment in the initial stage of culture (up to two weeks).
