Synergistic Effect of Aspartate on Chrysophyllum africanum Adsorption on Steel in Saline Media: Experimental and Theoretical Insights

This study explores the corrosion inhibition potential of Chrysophyllum africanum (CA) biomass extract on mild steel in a 3.5% NaCl solution and how its performance is enhanced by blending with aspartic acid (AA). While both CA and AA exhibit low inhibition efficiencies individually of about 40% and 35%, respectively in neutral environments, their blending significantly improves protection, achieving up to 89.1% inhibition efficiency. GC-MS and FTIR were employed to characterize the CA's active components. The corrosion inhibition was assessed using gravimetric, electrochemical, and surface imaging techniques. A proposed mechanism highlights that the dissociation of AA in aqueous solution and its proton-donating ability promote electrostatic adsorption in neutral media, which is otherwise limited. Computational studies using DFT and MDS simulations support this synergy, revealing increased adsorption energies when CA is blended with AA. The synergistic interaction, quantified with an index of 0.339, demonstrates a cooperative effect between the two agents. These findings suggest that blending CA with AA offers a promising, eco-friendly corrosion inhibitor for mild steel in saline environments.