Evaluation of corrosion inhibition efficiency of chitosan oligosaccharide-derived quaternary ammonium vanillyl aldehyde oligosaccharide derivative for CO2 corrosion control

This study presents the synthesis of a non-toxic, water-soluble chitosan oligosaccharide derivative, quaternary ammonium vanillyl aldehyde oligosaccharide (GCOS), using chitosan oligosaccharide, vanillin, and 2,3-epoxypropyltrimethylammonium chloride as precursors, aimed at serving as a novel eco-friendly corrosion inhibitor. The successful synthesis of the derivative was confirmed through Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance (1H NMR) analysis. The corrosion inhibition properties of GCOS on 20# carbon steel were investigated in a 60 °C CO2-saturated 3.0 wt% NaCl solution employing an array of methods including weight loss measurements, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), electrochemical characterization, and molecular dynamics simulation. Additionally, the synergistic effect of protonated GCOS with halide ion Cl- on corrosion inhibition was analyzed at the molecular level. The results indicated an enhancement in inhibition efficiency with increasing concentrations of the inhibitor. Weight loss measurements showed a maximum inhibition efficiency of 90.9% at 200 ppm of GCOS after 3 days. The adsorption of GCOS on the carbon steel surface was found to follow the Langmuir adsorption isotherm, predominantly through chemisorption. Potentiodynamic polarization measurements classified GCOS as a mixed-type inhibitor, affecting both anodic and cathodic reactions by blocking the active corrosion sites. SEM and AFM analyses confirmed the formation of a protective inhibitor film on the metal surface. Furthermore, molecular dynamics simulations elucidated the synergistic corrosion inhibition effect between the protonated GCOS molecules and Cl- ions in the acidic solution.