A novel chitosan Schiff base derivatives as eco-friendly corrosion inhibitors for Q235 carbon Steel: A combined experimental and theoretical study

In this study, two novel chitosan-based Schiff bases, SCBS-I and SCBS-II, were synthesized by condensation reactions between chitosan and isatin or menthone, respectively. The prepared Schiff bases were further quaternized via 2,3-epoxypropyltrimethylammonium chloride (EPTAC) to augment inhibitor solubility and inhibition efficiency. Developed as a green and eco-friendly corrosion inhibitor for Q235 carbon steel in hydrochloric solution. The successful synthesis of two chitosan derivatives was characterized via ¹H NMR and FTIR studies. The inhibitors efficiency was evaluated through weight loss, with a greater inhibition efficiency of 94.8 % achieved at 250 mg. L⁻¹. Electrochemical studies including EIS and PDP measurements suggest the inhibitors act as mixed types, while aligning with the Langmuir adsorption isotherms model. Gibbs free energies (ΔG) indicate that the inhibitors adsorb onto the carbon steel surface via physical and chemical adsorptions. The surface morphology was investigated using SEM, and XPS confirmed the formation of an adsorbed protective film on the metal surface. Molecular dynamics simulations were applied to investigate the corrosion inhibition mechanism. These findings provide new insights into the design of eco-friendly Schiff base–chitosan derivatives, and future work will focus on optimizing molecular structures and evaluating their performance in more complex corrosive environments.