In our latest publication, Yajie Chen, Johanna Torres, Homero Castaneda, and Lu-Kwang Ju demonstrate that nutrient starved Desulfovibrio vulgaris (a sulfate reducing bacterium) is more corrosive than sea-water-level chloride under anaerobic condition. Neither the bacteria nor chloride caused significant steel weight loss (corrosion). However, when the bacteria is starved of an organic electron donor (no consumable organic nutrients), it turns to the metal for electron donor. This process induces deep pits with various pit shapes (i.e. cylindrical, conical and hemispherical) into steel surface. Alternately, fewer pits were created during 3.5% NaCl exposure and these pits had mostly conical shape.
Pitting pattern and failure risk diagrams were, for the first time, employed to follow and differentiate the pitting development paths and failure risks in different corroding systems. Application of fast pitting-parameter-quantitation method in chloride and D. vulgaris systems with two levels of surface roughness were also validated by infinite focus microscope. Effects of surface roughness on pitting was also discussed. It was shown that smoother surface has fewer pits, but higher maximum pit depth.