Development of Natural Plant Extracts as Sustainable Inhibitors for Efficient Protection of Mild Steel: Experimental and First-Principles Multi-Level Computational Methods

Abstract

In the present work, we present the superior corrosion inhibition properties of three plant-based products, Fraxinus excelsior (FEAE), Zingiber zerumbet (ZZAE), and Isatis tinctoria (ITAE), that efficiently inhibit the corrosion of mild steel in phosphoric acid. The anti-corrosion and adsorption characteristics were assessed using a combination of experimental and computational approaches. Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy methods were used to evaluate the inhibitive performance of the inhibitors on the metal surface. Then, both DFT/DFTB calculations and molecular dynamic simulations were further adopted to investigate the interaction between organic inhibitor molecules and the metal surface. The protective layers assembled using the active constituents, such as carbonyl and hydroxyl groups, of the three plant-based products offer high electrochemical stability at high temperatures and robust protection against aggressive acidic solutions. All electrochemical measurements showed that the inhibition performance of extracts increased by increasing their concentration and improved in the following order: FEAE > ZZAE > ITAE. Further, these extracts worked as mixed-type inhibitors to block the anodic and cathodic active sites on the mild steel surface. Multi-level computational approaches revealed that FEAE is the most adsorbed inhibitor owing to its ability to provide electron lone pairs for electrophilic reactions. The experimental and theoretical results showed good agreement. These results indicate the possibility of replacing conventional compounds with natural substituted organic products in the fabrication of hybrid materials with effective anti-corrosion performance.

Sustainable and Green Corrosion Inhibition of Mild Steel: Insights from Electrochemical and Computational Approaches

“…Furthermore, the capacitive loops in these conditions are slightly depressed and take the form of semicircles with a center below the real axis. This distortion is attributed to frequency dispersion caused by the adsorption of inhibitor molecules at the metal surface, the formation of a porous layer, and the heterogeneity of the electrode surface. − The diameter of the Nyquist plots, which represents the corrosion protection ability of the inhibitor, increases as the concentration of LCC EO increases. This observation confirms that the inhibition of LCC EO on the corrosion of mild steel in a 0.5 M HCl solution occurs through the adsorption of the inhibitor molecules and is attributed to the formation of a [Fe-Inh] 2+ film.…”

Corrosion Prevention of Copper in 2.0 M Sulfamic Acid Using Novel Plant Extract: Chemical, Electrochemical, and Theoretical Studies

“…The contour maps of electron density show that oxygen and nitrogen atoms appear to be advantageous interaction sites on the investigated molecule inhibitor, which is consistent with the differences in functions between oxygen and the other atoms. A dark red outline surrounds the contact areas that produce the bonding connections between metal surfaces and inhibitor . In the contour map of negative potential, lupine extract molecules in the aqueous phase are particularly encircled by a dark red color, whereas the green color is dispersed across the positive potential region at the DFT/B3LYP/6-31++G­(2d,p) calculation level.…”

Fabrication of Protective Organic Layer Using Schiff-Base Metal Complex Responsible for Excellent Corrosion Performance: Experimental and Theoretical Perspectives

“…The following formula was used to predict the interaction between the inhibitor compound and the metal interface during the corrosive process , E normali normaln normalt normale normalr normala normalc normalt normali normalo normaln = E normalt normalo normalt normala normall − ( E normals normalu normalr normalf + normals normalo normall + E i n h i b i t o r ) where E total represents the calculated total energy of the system through simulation, E surf+sol denotes the energy calculated for the system iron/solution, and E inhibitor is the total energy of the inhibitor alone.…”

“…The following formula was used to predict the interaction between the inhibitor compound and the metal interface during the corrosive process 26 , 27 where E total represents the calculated total energy of the system through simulation, E surf+sol denotes the energy calculated for the system iron/solution, and E inhibitor is the total energy of the inhibitor alone.…”

“…These calculations were based on the highest occupied molecular orbital energy (HOMO), lowest unoccupied molecular orbital energy (LUMO), and energy gap (ΔE). For further details on the simulation process, readers can refer to the works by Chaouiki et al 23−25 The following formula was used to predict the interaction between the inhibitor compound and the metal interface during the corrosive process 26,27 = +…”