Search

Desulfovibrio alaskensis G20 biofilms were cultivated on 316 steel, 1018 steel, or borosilicate glass under steady-state conditions in electron-acceptor limiting (EAL) and electron-donor limiting (EDL) conditions with lactate and sulfate in a defined medium. Increased corrosion was observed on 1018 steel under EDL conditions compared to 316 steel, and biofilms on 1018 carbon steel under the EDL condition had at least twofold higher corrosion rates compared to the EAL condition. Protecting the 1018 metal coupon from biofilm colonization significantly reduced corrosion, suggesting that the corrosion mechanism was enhanced through attachment between the material and the biofilm. Metabolomic mass spectrometry analyses demonstrated an increase in a flavin-like molecule under the 1018 EDL condition and sulfonates under the 1018 EAL condition. These data indicate the importance of S-cycling under the EAL condition, and that the EDL is associated with increased biocorrosion via indirect extracellular electron transfer mediated by endogenously produced flavin-like molecules.

This work aims evaluate the use of biocides in the microbiologically-influenced corrosion (MIC) of AISI 1020 carbon steel by sulfate-reducing bacteria (SRB) in artificial seawater. A natural biocide (garlic oil) and a commercial biocide (glutaraldehyde) were used to control the corrosion caused by these bacteria in artificial seawater. Microbial growth on the steel surface was evaluated by quantifying the sessile SRB using the most probable number (MPN) method. The action of biocides in the biocorrosion process was studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The biofilm formation and the corrosion products on the steel surface were observed by scanning electron microscopy (SEM). The results showed that, although it was not able to inhibit the growth of sessile SRB completely, garlic oil showed a greater reduction in the corrosion process when compared to glutaraldehyde, indicating its possible application as a natural biocide under these conditions.

Abstract: Evaluation of microbial populations in oilfield systems is critical to understand the risk of microbiologically influenced corrosion, reservoir and surface souring (hydrogen sulfide production), and biofouling. Although traditional culture based methods have dominated oilfield microbial monitoring for years, use of molecular tools is becoming more common for both field and laboratory evaluations. The implementation of these additional tools is in response to some of the disadvantages of culture-based methods such as long incubation times and underestimation of actual microbial populations. The current work provides a direct comparison of culture-based methods (serial dilution for sulfate reducing, acid producing, and general heterotrophic bacteria) with molecular methods including adenosine triphosphate (ATP) and adenosine monophosphate (AMP) quantification and quantitative polymerase chain reaction (qPCR). The results demonstrate that these technologies provide nearly identical results in untreated samples with known culturable organisms, but show some differences when used in the context of a planktonic kill study. The pros and cons of each technology were addressed with respect to their use in field monitoring, laboratory monitoring, and microbial kill studies. The authors found that none of the technologies described in this work provide an all-inclusive answer, but together they provide significant insight into the microbial population in an oilfield system. In short, the authors demonstrate that it is advantageous for oilfield stakeholders to expand their microbial monitoring toolkit with these new technologies to ensure sustainable, cost-effective operation. [Copyright &y& Elsevier]

• The spools had thick oxides (heat tint) at the Heat-Affected Zone (HAZ) of circumferential welds. • The premature failure of the pipe systems (ASTM A312 Grade TP316L steel) was caused by Microbiologically Influenced Corrosion- MIC. • The main cause of the failure was the use of an inadequate procedure for the hydrostatic test. A failure analysis of welded pipes (ASTM A312 Grade TP 316L) in a water treatment plant was done and it is presented in this paper. The premature failure was detected by several water leakages caused by pitting corrosion three months after hydrostatic tests and before transferring the plant to the operator. The leakages were located near the bottom of the circumferential butt welds of the entire piping system. The samples were analyzed using visual inspection, radiographic examination, optical emission spectrometry, ferrite number (FN) measurements, metallographic examination and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectrometry (EDS). The results showed that the corrosion rate was extremely high compared to other studies available in the literature for austenitic stainless steel and the pits were in the weld metal and the Heat Affected Zone (HAZ) of the circumferential welds. The lack or deficiency of a purging gas during the field welding generated heat-tinted zones around the welds. Visual inspection showed that the pits were preferentially located at heat-tinted zones and they have large sub-surface cavities. The SEM inspection confirmed the presence of structures compatible with sulfate-reducing bacteria and iron-oxidizing bacteria and revealed that the failure was caused by microbiologically-influenced corrosion (MIC). The review of standards and codes used to perform hydrostatic testing of austenitic stainless steel piping systems showed that the water used for hydrostatic tests should have been treated before testing or the surfaces should have been deeply drained and dried. The failure was caused by the water used during the hydrostatic testing since it was not fully drained from the piping system and remained stagnant leading to MIC. [ABSTRACT FROM AUTHOR]