Mitigation of marine microbial corrosion using natural products based on chitosan polymer

A major cause of marine corrosion is sulfate-reducing bacteria (SRB). Traditional chemicals may pose an environmental threat to this sector. Therefore, this research aims to develop eco-friendly alternatives to biocides and corrosion inhibitors. This work successfully modified chitosan, a natural and biodegradable biopolymer, into cationic and non-ionic surfactants. H¹NMR, FTIR, and elemental analysis characterized the modified compounds. Mixed SRB culture was isolated from rust samples collected from steel immersed in a coastal area in Qingdao, China. Various techniques were used to evaluate the biological activity and corrosion protection provided by the newly modified chitosan surfactants in both abiotic and biotic environments, and their surface parameters in an aqueous solution were studied. SEM was used to display the surface morphology of the carbon steel; corrosion products were analyzed by EDS; surface topography and pitting were visualized by AFM; moreover, TEM was used to investigate the biocidal effect on the bacterial cell wall. Based on surface and thermodynamic calculations, the two surfactants exhibited adsorption behavior at the interface first, followed by aggregation in the bulk of the solution. The findings indicate that the newly modified chitosan-based surfactant displays significant corrosion protection over carbon steel and high antimicrobial activity against the isolated bacteria.