Understanding the synergistic inhibition effect of hydrosol extract derivatives as eco-friendly anti-corrosive for copper alloy: GC–MS Identification, An Electrochemical, surface morphology and computational modeling

Abstract

The research on green sources of corrosion inhibitors has gained significant traction in recent times due to their cost-effectiveness and environmentally friendly nature. In this study, we assessed the synergistic inhibitory impact of hydrosol extract (H-EX) derivatives obtained from T. Capitata (L.) Cav. on the corrosion of copper alloy (brass) in a 3% NaCl environment, employing a combination of experimental and computational approaches. The chemical composition of H-EX was analyzed through Gas Chromatography-Mass Spectrometry (GC–MS), revealing that Carvacrol (CA) constitutes the predominant compound at 98.01%. In addition, minor constituents include Acetovanillone Acetate (A-AC) at 1.41% and Eugenol (EU) at 0.58%. We assessed the corrosion inhibition properties using various electrochemical techniques, including Open Circuit Potential (OCP), Potentiodynamic Polarization (PDP), and Electrochemical Impedance Spectroscopy (EIS) measurements. The results unequivocally indicate the substantial anti-corrosion efficacy of H-EX, with an impressive inhibition efficiency (ƞEIS (%)) of 90.20% at a concentration of 1(g/L). Notably, H-EX exhibits characteristics of a cathode-type inhibitor, and its adsorption onto brass follows the Langmuir adsorption isotherm. Furthermore, H-EX demonstrates excellent inhibitory activity across a broad temperature range, spanning from 298 K to 338 K. The examination of surface morphology using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) reveals the formation of a robust protective film on the brass surface in the presence of H-EX. Our computational chemistry investigations, employing Density Functional Theory (DFT) with two functionals (B3LYP and M062X) at the 6–311++G(d,p) level, along with Monte Carlo (MC) simulations and the radial distribution function (RDF) tool, affirm the inhibitory performance of the eco-friendly H-EX compounds and their synergistic inhibitory effects on the metal surface. Moreover, MC simulation studies shed light on the synergistic and inhibitory interactions between the various components within the studied extract. Notably, the CA-AC-A-EU mixture demonstrates the most potent synergistic impact and offers the most effective protection for the metal surface, outperforming other combinations (i.e., CA-EU, CA-AC-A, and EU-AC-A), with adsorption energies of −114.80 Kcal/mol and −738.41Kcal/mol in gas and aqueous media, respectively. In conclusion, our study showcases the potential of using DFT and Monte Carlo (MC) simulations to enhance our understanding of the synergistic effects of natural extract-based inhibitors. This knowledge can significantly contribute to the design and production of more efficient and cost-effective mixed corrosion inhibitors.