INVESTIGATION OF NATURAL EXTRACTS AS GREEN CORROSION INHIBITORS IN STEEL USING DENSITY FUNCTIONAL THEORY

Abstract

. Steel is a material that has low resistance to corrosion when interacting with a corrosive environment. The application of natural extracts as green inhibitors is able to provide good performance in inhibiting corrosion of steel with high inhibition efficiency. Natural extracts that are effective and efficient as corrosion inhibitors on steel are those which in their compound structure contain heteroatom groups (such as O, N, S, P) and aromatic rings. This work provides an important comparative overview for the development of green inhibitor natural extracts in steel. The results of theoretical studies based on quantum mechanics with the DFT method at the atomic level based on molecular orbitals, chemical quantum parameters, and adsorption characteristics show results that are in accordance with experimental studies. The frontier molecular orbital (FMO) plot shows the distribution of electron density in the HOMO-LUMO region as a predictor of the active site of the inhibitor molecule interacting with the steel surface. Quantum chemical parameters such as ionization potential (I), electron affinity (A), absolute electronegativity (χ), hardness (η), softness (σ), fraction of electrons transferred (ΔN), electrophilicity (ɷ), and electron back-donation (ΔEback-donation) was calculated to obtain a correlation between the electronic properties of the inhibitor molecule and the corrosion inhibition potential. The results of the calculation of the quantum chemical parameters show the reactivity of the inhibitor molecule which has a very good potential to interact and bind strongly to the steel surface. This has the potential to make the inhibitor molecule have a high inhibition efficiency. Chemical adsorption and/or physical adsorption by forming complex compounds between inhibitor molecules and the steel surface are corrosion inhibition mechanisms to protect steel from a corrosive environment.The development of future studies should be able to display the mechanism of interaction and inhibition of inhibitor molecules in more detail and systematically at the atomic level on several metal surfaces such as Fe, Al, Cu, and others.