Abstract
Carbon steels are widely used in the oil and gas industry from downhole tubing to transport trunk lines. Microbes form biofilms, some of which cause the so-called microbiologically influenced corrosion (MIC) of carbon steels. MIC by sulfate reducing bacteria (SRB) is often a leading cause in MIC failures. Electrogenic SRB sessile cells harvest extracellular electrons from elemental iron oxidation for energy production in their metabolism. A previous study suggested that electron mediators riboflavin and flavin adenine dinucleotide (FAD) both accelerated the MIC of 304 stainless steel by the Desulfovibrio vulgaris biofilm that is a corrosive SRB biofilm. Compared with stainless steels, carbon steels are usually far more prone to SRB attacks because SRB biofilms form much denser biofilms on carbon steel surfaces with a sessile cell density that is two orders of magnitude higher. In this work, C1018 carbon steel coupons were used in tests of MIC by D. vulgaris with and without an electron mediator. Experimental weight loss and pit depth data conclusively confirmed that both riboflavin and FAD were able to accelerate D. vulgaris attack against the carbon steel considerably. It has important implications in MIC failure analysis and MIC mitigation in the oil and gas industry.
Highlights
Influenced corrosion (MIC) has become a major problem in the oil and gas industry due to frequent deployment of water flooding in enhanced oil recovery that increasingly leads to water wetting of pipeline walls [1]
The results demonstrate that both flavin adenine dinucleotide (FAD) and riboflavin did not increase the cell concentrations and influence the pH
Experimental data in this work demonstrated that two common electron mediators, riboflavin and FAD, at a low concentration (10 ppm) both were capable of increasing the Microbiologically influenced corrosion (MIC) of C1018 carbon steel considerably in terms of weight loss and pit size by D. vulgaris
Summary
Influenced corrosion (MIC) has become a major problem in the oil and gas industry due to frequent deployment of water flooding in enhanced oil recovery that increasingly leads to water wetting of pipeline walls [1]. Riboflavin and FAD Promoted MIC of Desulfovibrio vulgaris greatly increase microbial diversity and population. Another key factor is that oil and gas infrastructures are aging allowing more time for microbes to corrode. There has been no clear mechanism that clarifies why and how MIC happens in nature because of its complexity. This makes it difficult to identify the role of MIC in various corrosion failure cases amid a myriad of other factors such as chemical corrosion caused by CO2 and H2S
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