Electrochemical and quantum chemical exploration on L-ornithine L-aspartate as a sustainable corrosion inhibitor for AISI 1018 steel in acidic environment.

This study uses an extensive strategy that includes quantum chemical calculations, gravimetric studies, electrochemical methods, adsorption analyses, and thermodynamic evaluations to investigate the effectiveness of expired L-Ornithine L-Aspartate (ELOLAd) as a corrosion inhibitor for AISI 1018 steel in 1.0 M HCl solutions. The substantial adsorption capacities of ELOLAd on the Fe (111) surface, which are essential for its inhibitory effectiveness, are demonstrated by Monte Carlo simulations. According to Tafel polarization experiments, ELOLAd increases protection efficiency from 19.8% to 92.9% at concentrations between 0.075 and 0.452 mM. ELOLAd acts as a mixed-type inhibitor with predominant anodic influence. The protective efficiency ranges from 0% (blank) to 94.3% at the maximum concentration, according to gravimetric measurements. However, protection efficiency drops to 91.5% and 90.7% at 318 K and 328 K, respectively, implying that ELOLAd’s effectiveness is significantly reduced at higher temperatures. Electrochemical impedance spectroscopy (EIS) measurements reveal a significant increase in charge transfer resistance and a decrease in double-layer capacitance, confirming that ELOLAd forms a robust, dielectric protective barrier at the steel/electrolyte interface. Surface characterization via SEM and EDX confirms the formation of a dense, protective organic film on the AISI 1018 steel, which significantly mitigates acid-induced pitting and surface degradation in the presence of ELOLAd. ELOLAd tends to alter corrosion processes by creating a protective layer, according to measurements of its apparent activation energy (Ea) and activation enthalpy (ΔH*). The Freundlich model best describes the adsorption behavior, according to adsorption studies. The adsorption process is spontaneous and primarily driven by physisorption processes, as evidenced by the negative Gibbs free energy change (ΔG° = -11.72 kJ mol−1). All aspects considered, our results show how promising ELOLAd is for successfully preventing corrosion in extremely acidic environments.