Bacterial exopolymeric inhibition of carbon steel corrosion

The development of biofilms is a combination of adhesion of organic and/or inorganic macromolecules, exopolymeric substance (EPS) production and microbial growth. In this study a variety of bacterial strains were isolated from different environments such as soil and water in order to investigate the corrosion inhibition by EPS. Fifty two mucoid colonies were obtained from the samples on Luria–Bertani (LB) medium. Carbon steel (low carbon) coupons were then exposed to seawater-mimicking medium (VNSS) containing different bacterial suspensions. Twenty one bacteria were identified by fluorescence dye staining screening for their efficient biofilm formation and biofilm development/EPS attachment on coupons surface. The mass loss of coupons was determined and two bacterial strains were selected for further analyses. The results obtained from EPS extraction, electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FT-IR) demonstrated that two bacterial strains could produce EPS with good effect on corrosion inhibition. The biochemical tests and 16S rRNA ribotyping lead to identification of these strains as Chryseobacterium indologenes MUT.2 and Klebsiella pneumonia MUT.1.

► Innovative use of biofilms were applied to the EPSs screening process.
► Two native bacteria with carbon steel anticorrosion properties were isolated.
► Bacterial exopolymer efficiently inhibited carbon steel corrosion.
► An equivalent circuit was selected for analysis of biopolymeric anticorrosive role.