Carbon steel corrosion induced by sulphate-reducing bacteria in artificial seawater: electrochemical and morphological characterizations

Abstract

In this work, the corrosion behavior of carbon steel AISI 1020 was evaluated in artificial seawater in the presence of mixed sulfate-reducing bacteria (SRB) culture isolated from the rust of a pipeline. The corrosion evaluation was performed by electrochemical techniques (open circuit potential (E ocp ), polarization curves and electrochemical impedance spectroscopy (EIS)), while the formation of a biofilm and corrosion products were observed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The presence of SRB in the medium shifted the open circuit potential to more positive values and increased the corrosion rate of the steel. Electrochemical and morphological techniques confirmed the presence of a biofilm on the steel surface. EDS spectra data showed the presence of sulfur in the corrosion products. After removing the biofilm, localized corrosion was observed on the surface, confirming that localized corrosion had occurred. The biogenic sulfide may lead to the formation of galvanic cells and contributes to cathodic depolarization.

Electrochemical Studies of Microbiologically Influenced Corrosion on API 5L X65 by Sulfate-Reducing Bacteria in CO_2 Environments

“…MIC materialises after the production of a biofilm on the surface of the steel 11,12) . In the course of SRB's metabolic activity, reduction of sulfate ions occurs into three forms of sulfide ions, namely H2S (soluble), HSand S [2][3][4][5][6][7][8][9][10][11][12][13]14) . The company of carbon dioxide (CO2), hydrogen sulphide (H2S), seawater and other particles initiate critical corrosion-related problems in oil and gas pipelines.…”

Microbially influenced corrosion of carbon steel in the presence of anaerobic sulphate-reducing bacteria

“…Interactions between the metal surface and the biofilm may then alter the kinetics of anodic/cathodic reactions occurring during electrochemical processes. Biofilm formation may enhance metal deterioration [34] by affecting the physico-chemical properties of the metal surface or by altering the properties of the passivation layer [11]. On the other hand, biofilms can also have a passivation effect, protecting the metal surface against corrosion [35].…”

“…Over the last decade, several studies have reported MIC on stainless steel, carbon steel and P235GH steel materials under repository relevant conditions [4,[34][35][36][37]. A recent study on MIC of carbon steel exposed to anaerobic soil using conventional electrochemical techniques demonstrated localised corrosion on the steel surface accompanied by breakdown of the biogenic ferrous sulphide (FeS) film [38].…”

“…During this three-month study, a corrosion rate of 1.4 µm·a −1 of carbon steel coupon was described at room temperature and 11.4 µm·a −1 at 6°C [39]. While a further study also noted biofilm formation on carbon steel exposed to SRB, the experiment only lasted 35 days, which limited the corrosion behaviour observed [34]. Overall, these studies were subject to a number of methodological shortcomings, such as lack of microbial analysis and/or sterile control conditions and inadequate exposure time.…”