Deeper insights into SRB-driven biocorrosion mechanisms

• Author(s): Dall’Agnol, Leonardo Teixeira
• Date: 2013
• Persistent ID: http://hdl.handle.net/10362/10424
• Origin: Repositório Institucional da UNL
• Subject(s): Biocorrosion; EPS; Iron uptake; SRB; Surface analysis
• Document Type: Doctoral thesis
• Language: English
• Advisor(s): Moura, José J. G.
• Contributor(s): RUN

Description

Dissertação para obtenção do Grau de Doutor em Química Sustentável

Microbially Influenced Corrosion (MIC) is recognized as an important category of corrosion and represents one of the most challenging to study and prevent. In biocorrosion, Sulphate Reducing Bacteria (SRB) are the best suited organisms because its ability to produce biogenic hydrogen sulphide. Still little is known about the mechanisms related to corrosion involving those microorganisms. In that regard, this thesis describes the analysis of the interactions, and its consequences, between Desulfovibrio desulfuricans ATCC 27774 and metal surfaces using electrochemistry, of surface analysis and biochemical techniques. The Open Circuit Potential (OCP) showed that the equilibrium of sulphide in the solution/gas phases is a key factor on determining the evolution of the corrosion process. Also it have been demonstrated that, although the trend in the behaviours remains, long measurements periods are necessary to avoid overestimations when dealing with biocorrosion. Our results also indicate that the nitrate injection strategy in oil fields has to be considered carefully as it can increase the uniform corrosion and the SRB population growth rate. High-throughput analysis techniques were used to characterize the surface of metal plates after incubation with SRB with different respiratory substrate. The precipitation of inorganic salts as calcium and phosphates, has been detected in the samples incubated in sulphate and could be related to iron dissolution areas in the metal surface. Also micropitting underneath the bacteria cells could be observed when the bacteria were incubated. In nitrate medium, a high concentration of precipitated chloride ions was observed on the surface which could be responsible for the enhanced corrosions rates observed. The Extracellular Polymeric Substance chemical composition corroborated the previous results regarding the iron uptake and the influence of phosphates and other functional groups in the corrosion process. The protein profile characterization has demonstrated heterogeneity of the expressed proteins depending on the respiratory substrate.

Project BIOCOR ITN, "People" Programme, under grant agreement n° 238579