Microbially influenced corrosion of structural materials

Studies of microbially influenced corrosion (MIC) of structural materials were conducted in solutions containing a single bacterial strain extracted from a known MIC failure site, using laboratory-based electrochemical methods (open-circuit potential measurements and potentiodynamic polarization techniques) and electron microscopy (scanning electron microscopy, scanning transmission electron microscopy with energy-dispersive spectroscopy and x-ray photoelectron spectroscopy).

The results indicated that the open-circuit corrosion potential of a prepassivated platinum electrode could serve as an indicator of changes in interfacial oxygen content. By using a double-electrode system (platinum and material-under-study), one can study the time effects of bacteria on the corrosion behavior of materials by simultaneously measuring the open-circuit potentials of the material and the platinum. This approach would appear to be a useful procedure in monitoring MIC attack at industrial sites.

The investigation also showed that the single A6F bacteria formed non-uniform tubercles on the material surfaces, which created occlusive geometries with highly aggressive local environments that shifted the anodic reactions of the materials toward higher rates.

The studies of MIC for austenitic stainless steel weldments revealed that the weld metal was selectively attacked by the bacteria, and that within the weld metal the austenitic phase was preferentially attacked.

The present studies indicated that the electrostatic nature of bacterial adhesion should be more fully addressed. Initial theoretical and experimental results showed that the surface conditions of materials would greatly affect the corrosion behavior under MIC conditions.