Microbiologically influenced corrosion in the stress-corrosion cracking of steels

One grade of stainless steel and one of carbon steel were tested in two environments containing microorganisms for stress-corrosion cracking with C-ring specimens. Although no specimens ever cracked during the test period of 96 days, their corrosion behavior could still be studied through corrosion potential monitoring, cyclic polarization, scanning electron microscopy and energy dispersive spectroscopy.; The stainless steel specimens did not undergo microscopically detectable corrosion during the immersion test. However, microorganisms lowered their resistance to localized corrosion and lowered corrosion potential.; Microorganisms also lowered the corrosion potential and caused more severe general corrosion for the carbon steel specimens. In addition, they affected the composition of various elements in the deposits on the carbon steel specimens.; It is also found that almost all the stainless and carbon steel specimens reached a similar corrosion potential which may suggest that this potential is heavily affected by the passive film, corrosion products, biofilm or a combination of them.