Carbon steel Q235 corrosion protection by metabolism of Bacillus cereus biofilms in cooling water environment

Abstract

Multiple types of microorganisms have been reported to provide a corrosion protective effect on metals, but few cases under cooling water environments. This study addresses this research gap by employing Bacillus cereus (B. cereus) biofilms for carbon steel (CS) Q235 corrosion protection. The results demonstrated that the addition of B. cereus agent reduced the weight loss of CS Q235 by 92.38 %, increased the electrochemical impedance (R_ct 21616.77 Ω/cm²) and lowered the corrosion current density (I_corr 16.8 μA cm⁻²). Surface analysis indicated that B. cereus cells secreted polysaccharides and proteins to form a biofilm. Such biofilm, combined with biomineralized corrosion products, formed a composite layer that prevented direct contact between CS Q235 and corrosive media. Moreover, metabolites of B. cereus biofilm associated with corrosion protective capacity were profiled and screen by untargeted metabolism analysis. A total of 376 metabolites were detected and genetic materials including uridine monophosphate (UMP) and guanosine monophosphate (GMP) were identified as the most critical metabolic principle for corrosion protection. These metabolites, which enriched in nucleotide metabolic pathways, was considered as metabolic mechanisms of corrosion protection. The B. cereus cells forming extracellular polymeric substance (EPS)-biofilm to alter the physicochemical properties of CS Q235 surface and repelled the attachment of corrosive microorganisms, thus hindered their multiplication and protected CS Q235 from corrosion in cooling water environment.