The mechanistic pathways of extracellular polymeric substances in the inhibition of carbon steel corrosion.

This study examined the corrosion inhibition mechanisms of extracellular polymeric substances (EPS) from Lactobacillus reuteri, Pseudomonas fluorescens, and Escherichia coli on carbon steel. Using UV spectrophotometry, LC-MS, infrared spectroscopy, and atomic force microscopy (AFM), it was apparent that all three EPS effectively inhibited corrosion, with optimal concentrations of 300 mg/L for Lactobacillus reuteri and 400 mg/L for the other species, yielding inhibition efficiencies of 28.25%, 23.87%, and 21.72%, respectively. The carboxyl group content was critical, with Lactobacillus reuteri EPS having the highest proportion. Functional group analysis showed it contained 12.39% and 12.93% more carboxyl groups than those from Pseudomonas fluorescens and Escherichia coli. Iron ion adsorption was primarily physical and occurred in a monolayer, with a greater capacity for Fe³+ than Fe2+, peaking at 600 mg/L.