Biocorrosion of Bacterial Inoculation on the API X52 Pipeline Steel

Abstract

ABSTRACTThe role of the initial bacterial inoculates on the biocorrosion of API X52 pipeline steel coupons was evaluated by electrochemical noise technique. The experiments were performed under laboratory conditions using an aerobic bacteria identified as Achromobacter xylosoxidans. Inoculations in the interval strain of 1x104 – 1x108 CFU/ml were evaluated. Environmental scanning electron microscopy (ESEM) analysis was carried out to evaluate the corrosive effects induced on the API X52 electrodes. The results show that all corroded surfaces show sites of localized corrosion, however, the density of de sites of localized corrosion have different grades depending of the initial inoculation used during the experiments. The maximum density sites of localized corrosion were obtained in the experiments with 1x105 CFU/ml. From inoculates of 1x106 CFU/ml the density sites of localized corrosion diminished constantly. The results show that with inoculates over 1x106 CFU/ml, the oxygen demand for the bacterial strain limits the presence of oxygen available into the metallic surface to maintain the corrosion reactions. The results were supported by the EDX analysis of the corrosion products formed on the metallic surfaces where the oxygen peaks diminished as the bacterial inoculation increases.