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Morphology of an API 5L steel exposed to aerobic bacterial culture

Abstract:

Bacterial corrosion is recognized as a worldwide problem that affects different industries. In oil industries, 40% of the internal damage in transporting pipeline distribution is attributed to microbially-induced corrosion. Several studies have been focused on anaerobic corrosion influenced by sulfate-reducing bacteria and few advances related to the MIC by aerobic microorganisms have been described. In this study, two aerobic bacterial strains isolated from naphtha distribution system of Venezuelan Oil Industries with corrosion damage were tested using Scanning Electron Microscope in order to determine their morphological characteristics and their possible corrosivity on coupons steel surfaces API 5L. Morphological analysis allowed to discriminate that bacterial strains have different morphotypes (cocco and bacilli). The fluorescence microscopy quantification revealed the same sessile cell density values for the both strains. MEB analysis on the metal surface allowed to detect opposed effect produced by the bacterial strains: bacilli type strain generated a protective effect while the cocco type strain did not inhibit corrosion. Instead, in the presence or absence of the cocco type strain, localized corrosion (pitting) like control were obtained, suggesting the prevalence of abiotic corrosion in the condition studied. The results obtained are discussed.