Microbial activity involvement on soil corrosion of old ductile iron was studied through electrochemical tests and microscopic analysis. Immersion test was conducted at room temperature under stagnant conditions during 62 days where sterilization and oxygen parameters were considered. Mechanisms were investigated through DC and AC electrochemical measurements combined to microscopic observation of surface products by SEM. The results showed an accelerated corrosion in the case of aerated biotic condition with evidence of oxygen promoting bacterial activity. However, corrosion inhibition was observed under deareated biotic condition. The results imply clearly the role of burying depth and soil compactness on ductile iron water pipe life time.