Effect of Sulfate Reducing Bacteria on the Corrosion Behavior of the HSLA X70 Steel in Bacteria Culture Medium

In this study, microbiologically influenced corrosion because of metabolite sulfate reducing bacteria (SRB) has been investigated in terms of its electrochemical behavior and surface phenomena. According to the results of electrochemical impedance spectroscopy, SRB through changing the bacteria culture medium during the first hour that sample was contacted to the bacteria solution, leads to an increase in corrosion resistance of HSLA X70 steels from 235 to 1651Ω.cm2. Microstructural examinations on the sample surface embedded in culture medium without bacteria, in comparison to the sample exposed to the culture medium with bacteria, indicate that corrosion products disperse widely which is consistent with the electrochemical tests results. On the contrary, sample exposed to the SRB included bacterial colonies, although shows a reduction in the uniform corrosion rate via the alkalization of the culture medium, provides sites under colonies which are prone to the pitting corrosion. The results of the cyclic polarization test confirm the susceptibility to pitting corrosion of the sample in the bacteria containing solution.