Resumen

OCANDO, Lisseth et al. Influence of ferrous ions, pH and H₂S at the interface on the corrosion mechanism of iron by Sulfate-Reducing Bacteria. Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.Especial, pp.223-233. ISSN 0254-0770.

Microbiologically Influenced Corrosion (MIC) by Sulfate-Reducing Bacteria (SRB) has been the subject of extensive studies for the past five decades and several theories have been proposed to explain the mechanisms governing MIC. Recently, a corrosion mechanism for the action of SRB on iron was proposed, which seeks to explain the initiation of this kind of corrosion in order to improve prevention and mitigation techniques. This mechanism was supported on the fact that there should be a local pH decrease at the metal/solution interface. So, the principal aim of this work was to prove this theory by evaluating an iron interface exposed to a culture medium rich in nutrients and SRB. The H₂S concentration produced was also evaluated to establish its relation with the pH at the interface. To measure these parameters during 24 hours, pH and H₂S microelectrodes with tip diameters of 10 µm were used. A SRB pure culture of Desulfovibrio desulfuricans subs. desulfuricans was used, grown as batch culture in modified ATCC 1249 medium with and without ferrous ions, in order to determine their influence on the pH and H₂S behavior. Attack morphology and biofilm structure in both mediums were also determined by scanning electron microscopy (SEM). The results showed that pH into the biofilm decreased depending on the ferrous ions presence. Also, it was confirmed the influence of ferrous ions and ferrous sulfides aggressiveness in the corrosion process established in the mechanism.

Palabras clave : MIC; SRB; Microelectrodes; pH; H₂S; ferrous ions.