Corrosive aggressiveness of production water by effect of sulfate-reducing bacteria/Agresividad corrosiva de un agua de produccion por efecto de bacterias sulfato-reductoras/Agressividade corrosiva de uma agua de producao por efeito de bacterias sulfato redutoras

The corrosive aggressiveness on carbon A-366 steel exposed to a mixed culture of sulfate-reducing bacteria (MCSRB) isolated from production water in a flow station of the Venezuelan oil industry was analyzed. Different conditions that influence the growth of the MCSRB in a synthetic production water (SPW) were studied, simulating the conditions of plant water. Plankton and sessile growth curves for 10% MCSBR in SPW inoculums were obtained. The dependence on pH, sulfur, sulfate and iron in the medium was analyzed, as well as the loss of weight in time and the morphology of the attack on the exposed steel. The time course of iron sulfurs' production by effect of SRB was determined and samples were taken for X ray diffraction analysis. It was determined that with 10% initial inoculums, maximal SRB plankton ([10.sup.8]cell/ml) and sessile ([10.sup.6]cell/[cm.sup.2]) growths were reached, similar to those in the plant after a 48h exposure. The local attack by SRB on steel pieces is characterized by small bites (± 50µm) uniformly distributed on the metal surface. This shows that once the bio-pellicule is formed on the metal surface, this is activated and permanently corroded, being indicative of the joint influence of iron sulfur products and bacteria, negatively interacting on the material and leading to its corrosion.