Molecular Level Understanding of the Mechanism of Aloes Leaves Extract Inhibition of Low Carbon Steel Corrosion: A DFT Approach

Quantum mechanics calculations have been applied within the framework of the density functional theory (DFT) to five major molecules of Aloes extract namely; Anthranol (AN), Aloin-Emodin (AE), Aloin Barbaloin (AB), Chrysophanol glycoside (CN) and Rutin (RT) recently investigated as corrosion inhibitor for mild steel in 1.0 M HCl in order to determine the structural and electronic parameters of the molecules responsible for imparting on the extract its high inhibition efficiency as corrosion inhibitor. The electronic parameters calculated include: EHOMO, ELUMO, energy gap (Δε) etc,. The calculated results show that all the molecules have high propensity as electron donors, have low Δε and η (high reactivity), are good nucleophiles characterized by low values of ω, and the energy change associated with the charge transfer to the mild steel surface ΔE, are all favourable (negative). Our result confirms the generally held assumption that there is a synergistic effect between the different organic molecules present in plant extracts towards enhancing the corrosion inhibition of these extracts on metals and alloys in varied aggressive media.