Corrosion Behavior and Mechanism of L245 Pipeline Steel Induced by Extracellular Polymeric Substances (EPS) of <i>Desulfomicrobium baculatum</i> Under the Regulation of Volatile Fatty Acid Carbon Sources

ABSTRACT A strain of Desulfomicrobium baculatum was isolated from shale gas flowback fluid in this study. By extracting extracellular polymeric substances (EPS), the effects of volatile fatty acid (VFA) carbon sources (sodium formate, sodium acetate) and sulfate‐reducing bacteria (SRB) medium carbon source (sodium lactate) on EPS composition and the corrosion of L245 pipeline steel were investigated. The results showed that under the same culture time, the total polysaccharide content of EPS followed the order: sodium formate‐EPS &gt; sodium acetate‐EPS &gt; sodium lactate‐EPS, while the total protein content followed: sodium acetate‐EPS &gt; sodium formate‐EPS &gt; sodium lactate‐EPS. The corrosion rate was lower in the sodium formate‐EPS medium with the highest polysaccharide content (45.34 μg/mL). The corrosion of carbon steel by EPS is achieved through physical adsorption and chemical complexation: physical adsorption inhibits corrosion in the early stage; in the later stage, functional groups of polysaccharides and proteins in EPS complex with Fe 2+ , hindering the formation of passive films and thus intensifying corrosion.