Computational Modeling: Theoretical Predictive Tools for Designing of Potential Organic Corrosion Inhibitors

In-Depth Insight into Corrosion Inhibition Performance of Sweet Potato Leaf Extract as a Green and Efficient Inhibitor for 6N01 Al Alloy in the Seawater: Experimental and Theoretical Perspectives

Corrosion protection of metal has become an important and urgent topic, which requires the development of an inexpensive, environmentally friendly, and highly efficient corrosion inhibitor. Herein, a sweet potato leaf extract (SPL) was obtained by a simple water-based extraction method and then as a green corrosion inhibitor for 6N01 Al alloy in the seawater was well investigated by the weight loss method and various electrochemical tests. Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) spectroscopies were carried out to investigate the compositions of SPL. The findings from the potentiodynamic polarization (PDP) curves suggest that SPL functions as a typical mixed-type corrosion inhibitor. Notably, the maximum corrosion inhibition efficiency reaches 94.6% following a 36 h immersion period at 25 °C. The adsorption behavior of SPL on the Al alloy surface belongs to the Langmuir adsorption isotherm. The Gibbs free energy value illustrates that the adsorption of SPL contains both physisorption and chemisorption. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) indicate that SPL is firmly attached to the Al alloy surface by making a protective layer, which can effectively inhibit the corrosion of the Al alloy in the seawater. Furthermore, quantum chemical calculations were applied to validate the chemical adsorption and elucidate the relationship between the electronic structure of the active components in SPL and their effectiveness in corrosion inhibition.

Zwitterion modified chitosan as a high-performance corrosion inhibitor for mild steel in hydrochloric acid solution

Herein, a novel chitosan Schiff base (CS-FGA) as a sustainable corrosion inhibitor has been successfully synthesized via a simple amidation reaction by using an imidazolium zwitterion and chitosan (CS). The corrosion inhibition property of CS-FGA for mild steel (MS) in a 1.0 M HCl solution was studied by various electrochemical tests and physical characterization methods. The findings indicate that the maximum inhibition efficiency of CS-FGA as a mixed-type inhibitor for MS in 1.0 M HCl solution with 400 mg L-1 reaches 97.6 %, much much higher than the CS and the recently reported chitosan-based inhibitors. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) results reveal that the CS-FGA molecules firmly adsorb on the MS surface to form a protective layer. The adsorption of CS-FGA on the MS surface belongs to the Langmuir adsorption isotherm containing both the physisorption and chemisorption. According to the X-ray photoelectron spectroscopy (XPS) and UV-vis spectrum, FeN bonds presented on the MS surface further prove the chemisorption between CS-FGA and Fe to generate the stable protective layer. Additionally, theoretical calculations from quantum chemical calculation (DFT) and molecular simulations (MD) were performed to reveal the inhibition mechanism of CS-FGA.

Synergistic effect of KI on the corrosion inhibition of a poly(diallylammonium chloride)-based cyclocopolymer containing bis-cationic motifs for mild steel corrosion in 20% formic acid

This study entails the syntheses of a homopolymer, poly(diallylammonium chloride) (3), and copolymers (8a-c) containing hydrophilic/hydrophobic pendants and their role in mitigating mild steel in aggressive 20% formic acid, a type of corrosion that is not frequently discussed in the literature. The synthesized homopolymer and copolymers were characterized by FTIR, NMR, viscometry, and TGA. Inhibitor 8b was found to be the most potent, with 81.8% inhibition efficiency (IE) registered via the potentiodynamic polarization method for 100 ppm of inhibitor concentration at 30 °C. Inhibitor 8b, mixed with 2 mmol KI, showed more than 90% IE for a meager 1 ppm inhibitor concentration. For a synergism of 50 ppm inhibitor and 2 mmol KI, the IE reached a high value of 99.1%. The synergism was so good that it helped the inhibitor retain ∼100% of its original IE even after a 24 h weight loss study at 60 °C. The adsorption isotherm study showed that 8b followed the Langmuir adsorption isotherm and adsorbed via chemisorption. A very high value (2.48 × 105 L mol-1) of the equilibrium adsorption constant (Kads) indicated strong adsorption. XPS and SEM surface studies provided evidence of the inhibitor found on the metal surface. Some toxicological parameters, such as LC50, bioaccumulation factor, and developmental toxicity, have been measured computationally. A brief mechanistic insight into how the inhibitors functioned has been offered along with the DFT study.

Zwitterions and betaines as highly soluble materials for sustainable corrosion protection: Interfacial chemistry and bonding with metal surfaces

The primary requirements for interfacial adsorption and corrosion inhibition are solubility and the existence of polar functional groups, particularly charges. Traditional organic inhibitors have a solubility issue due to the hydrophobic moieties they incorporate. Most documented organic inhibitors have aromatic rings, hydrocarbon chains, and a few functional groups. The excellent solubility and high efficacy of zwitterions and betaines make them the perfect replacements for insoluble corrosion inhibitors. Zwitterions and betaines are more easily soluble because of interactions between their positive and negative charges (-COO-, -PO3-, -NH3, -NHR2, -NH2R, -SO3- etc.) and the polar solvents. The positive and negative charges also aid these molecules' physical and chemical adsorption at the metal-electrolyte interfaces. They develop a corrosion-inhibiting layer through their adsorption. After becoming adsorbed at the metal-electrolyte interface, they act as mixed-type inhibitors, slowing both cathodic and anodic processes. They usually adsorb according to the Langmuir adsorption isotherm. In this article, the corrosion inhibition potential of zwitterions and betaines in the aqueous phase, as well as their mode of action, are reviewed. This article details the advantages and disadvantages of utilizing zwitterions and betaines for sustainable corrosion protection.

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

Copper corrosion was suppressed when a lupine extract was immersed in a 2 M sulfamic acid (H2NSO3H) solution. Numerous methods, including mass loss (ML), dynamic potential polarization (PL), and electrochemical impedance (EIS), were employed in these experiments, in addition to theoretical computations such as density functional theory (DFT), Fukui function, and Monte Carlo simulations. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were used to analyze the Cu surface's composition and determine its form. Mass loss (ML) was used to examine the inhibition rate of copper corrosion in sulfamic acid at 25 °C in the presence of lupine extract. After examining how it behaved throughout the adsorption process on copper, it was discovered that it follows the Langmuir isotherm and chemical adsorption. An analysis of the PL curves indicates that the lupine extract is a mixed-type inhibitor. It was shown that the inhibitory efficiency increased to 84.2% with increasing lupine concentration. Additionally, as the data show, the efficiency of inhibitors is diminished by increasing temperatures. Theoretical calculations and experimental data were compared using Monte Carlo simulation (MC) and density functional theory (DFT).

Investigation of Sulfonium-Iodide-Based Ionic Liquids to Inhibit Corrosion of API 5L X52 Steel in Different Flow Regimes in Acid Medium

The present work deals with the corrosion inhibition mechanism of API 5L X52 steel in 1 M H₂SO₄ employing the ionic liquid (IL) decyl(dimethyl)sulfonium iodide [DDMS⁺I^-]. Such a mechanism was elicited by the polarization resistance (R _p), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques, both in stationary and dynamic states. The electrochemical results indicated that the corrosion inhibition was controlled by a charge transfer process and that the IL behaved as a mixed-type corrosion inhibitor (CI) with anodic preference. The experimental results revealed maximal inhibition efficiency (IE) rates up to 93% at 150 ppm in the stationary state, whereas in turbulent flow, the IE fell to 65% due to the formation of microvortexes that promoted higher desorption of IL molecules from the surface. The Gibbs free energy of adsorption (ΔG°_ads) value of -34.89 kJ mol^-1, obtained through the Langmuir isotherm, indicated the formation of an IL monolayer on the metal surface by combining physisorption and chemisorption. The surface analysis techniques confirmed the presence of Fe _x O _y , FeOOH, and IL on the surface and showed that corrosion damage diminished in the presence of IL. Furthermore, the quantum chemistry calculations (DFT) indicated that the iodide anion hosted most of the highest occupied molecular orbital (HOMO), which eased its adsorption on the anodic sites, preventing the deposition of sulfate ions on the electrode surface.

Corrosion Inhibition Properties of Phenyl Phthalimide Derivatives against Carbon Steel in the Acidic Medium: DFT, MP2, and Monte Carlo Simulation Studies

The effectiveness of phenyl phthalimide and its derivatives at preventing corrosion of carbon steel has been tested experimentally using gravimetric and electrochemical measurements. However, experimental studies have not thoroughly explained the structural patterns and coating mechanisms of phenyl phthalimide and its derivatives during corrosion inhibition. In this study, the density functional theory (DFT), ab initio MP2, and Monte Carlo simulation are applied to study phenyl phthalimide (PP) and its derivatives as corrosion inhibitors of carbon steel. The geometry, quantum parameters, and reactive site of the inhibitors were determined by DFT and ab initio MP2 methods. The real environment conditions of corrosion inhibition in the solution phase can be replicated by the Monte Carlo simulation. The corrosion inhibition efficiency of phthalimide derivatives is PP-OCH₃ > PP-CH₃ > PP-H > PP-Cl > PP-NO₂. The theoretical study is consistent with previously reported experimental results.

New QSPR model for prediction of corrosion inhibition using conceptual density functional theory

The relationship between structure and corrosion inhibition of a series of twenty-eight quinoline and pyridine derivatives has been established through the investigation of quantum descriptors calculated with PBE/6-311 +  + G** method. A quantitative structure-property relationship (QSPR) model was obtained by examining these descriptors using a genetic algorithm approximation method based on a multiple linear regression analysis. The results indicate that the efficiency of corrosion inhibitors is strongly associated with hardness (η), minimal electrostatic potential (ESP_min), and volume (V) descriptors. Furthermore, the validity of the proposed model is corroborated by an adsorption study on an iron surface Fe(110).

Theoretical Study and Adsorption Behavior of Urea on Mild Steel in Automotive Gas Oil (AGO) Medium

The continuous search for eco-friendly corrosion inhibitors due to differences in corrosive media remains an important point in corrosion control. The experimental studies on the corrosion inhibition of urea on mild steel in automotive gas oil (AGO) was conducted using gasometric techniques and scanning electron microscope (SEM). The theoretical approach on the density functional theory (DFT) on the urea molecule was carried out using Gaussian 09 software. The adsorption behavior of urea molecules on the surface of the mild steel was analyzed using Frumkin and Flory-Huggins adsorption isotherms models and Gibb’s free energy, respectively. The result of the experimental study shows a poor corrosion inhibitory effect of urea on mild steel in automobile gas oil (AGO) medium as the inhibition efficiency decreased from 69.30% in week 1 to 12% in week 11 at 200 ppm of inhibitor. The adsorption of urea on the mild steel surface obeys Frumkin’s adsorption isotherm model. Gibb’s free energy of adsorption of urea molecules onto mild steel surface revealed a physisorption mechanism. SEM results showed the non-inhibitive nature of urea on the studied mild steel. Quantum chemical parameters such as HOMO, LUMO, electron affinity, electronegativity, and the fraction of electrons transferred to the metal surface were calculated and interpreted to compare the experimental and theoretical results. The theoretical findings in the current investigation were not in agreement with the experimental result, thereby creating a need for further study using the electrochemical method.

Corrosion Mitigation Performance of N80 Steel in 5% Sulfamic Acid Medium by Applying Novel Tetrahydro-1,2,4-triazines Including Triazene Moieties: Electrochemical and Theoretical Approaches

We observed our newly developed tetrahydro-1,2,4-triazines, including triazene moieties (THTA), namely, 6-((1E)-1-((2E)-(4-(((Z)-1-(2,4-diphenyl-2,3,4,5-tetrahydro-1,2,4-triazin-5-yl) ethylidene) triaz-1-en-1-yl)piperazin-1-yl) triaz-2-en-1-ylidene) ethyl)-2,4-diphenyl-2,3,4,5-tetrahydro-1,2,4-triazine (THTA-I), and 1-((E)-((E)-1-(2,4-diphenyl-2,3,4,5-tetrahydro-1,2,4-triazin-6-yl) ethylidene) triaz-1-en-1-yl) naphthalen-2-ol (THTA-II), as effective inhibitors for the corrosion protection of N80 carbon steel metal in 5% sulfamic acid as the corrosive medium via electrochemical approaches such as potentiodynamic polarization and electrochemical impedance spectroscopy. Furthermore, the tested steel exterior was monitored using X-ray photoelectron spectroscopy after the treatment with the investigated components to verify the establishment of the adsorbed shielding film. The investigated compounds acted as mixed-type inhibitors, as shown by Tafel diagrams. The compounds considered obey the Langmuir adsorption isotherm, and their adsorption on the steel surface was chemisorption. When the tested inhibitors were added, the double-layer capacitances, which can be determined by the adsorption of the tested inhibitors on N80 steel specimens, decreased compared with that of the blank solution. At 10^-4 M, the inhibitory efficacy of THTA-I and THTA-II achieved maximum values of 88.5 and 86.5%, respectively. Density-functional theory computations and Monte-Carlo simulation were applied to determine the adsorption attributes and inhibition mechanism through the studied components. Furthermore, the investigated inhibitors were considered to adsorb on the Fe (1 1 0) surface. The adsorption energy was then measured on steel specimens.

Efficient corrosion inhibition by sugarcane purple rind extract for carbon steel in HCl solution: mechanism analyses by experimental and in silico insights

Sugarcane purple rind ethanolic extract (SPRE) was evaluated as an efficient corrosion inhibitor for carbon steel (C-steel) in 1 M HCl solution. Dynamic weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and frequency modulation (EFM) measurements were employed to evaluate the anticorrosive efficiency of SPRE, which was further validated by morphological and wettability analyses. The results of the weight loss tests showed that the inhibition efficiency (η_w) for C-steel in HCl solution increased with an increase in the concentration of SPRE. An increase in temperature moderately impaired the anticorrosive efficacy of SPRE. The maximum η_w of 96.2% was attained for C-steel in the inhibition system with 800 mg L⁻¹ SPRE at 298 K. The polarization curves indicated that SPRE simultaneously suppressed the anodic and cathodic reactions for C-steel in HCl solution, which can be categorized as a mixed-type corrosion inhibitor with a predominant anodic effect. The corrosion current density (i_corr-P) was monotonously reduced with an increase in the concentration of SPRE. The charge transfer resistance (R_ct) was enhanced for C-steel in the inhibition solution with a restrained capacitive property due to the adsorption of SPRE. A high temperature caused partial desorption of SPRE on the C-steel surface and a slight increase in i_corr-P and decrease in R_ct. However, SPRE still fully maintained its morphology and wettability at 328 K. The electrochemical kinetics of C-steel in HCl solution without and with SPRE was also supported by EFM spectra. The adsorption of SPRE conformed to the Langmuir isotherm and increased the corrosion activation energy of C-steel. Complementing the experimental observations, calculations based on density functional theory indicated that the hydroxyl-substituted pyran moiety on the carthamin (CTM) and anthocyanin (ATC) constituents in SPRE hardly contributed to its reactive activity due to their adsorption processes. Therefore, CTM and ATC exhibited imperfect parallel adsorption on the Fe (100) plane according to the molecular dynamics simulation, while anthoxanthin (ATA) and catechinic acid (CCA) constituents exhibited a flat orientation on the iron surface.

The anticorrosive mechanism of extracted components from sugarcane purple rind for carbon steel in HCl solution is clarified by weight loss, electrochemical and theoretical (novel DFT calculation and molecular dynamics simulation) analyses.

Preparation, Characterization, and Evaluation of Macrocrystalline and Nanocrystalline Cellulose as Potential Corrosion Inhibitors for SS316 Alloy during Acid Pickling Process: Experimental and Computational Methods

Converting low-cost bio-plant residuals into high-value reusable nanomaterials such as microcrystalline cellulose is an important technological and environmental challenge. In this report, nanocrystalline cellulose (NCC) was prepared by acid hydrolysis of macrocrystalline cellulose (CEL). The newly synthesized nanomaterials were fully characterized using spectroscopic and microscopic techniques including FE-SEM, FT-IR, TEM, Raman spectroscopy, and BET surface area. Morphological portrayal showed the rod-shaped structure for NCC with an average diameter of 10-25 nm in thickness as well as length 100-200 nm. The BET surface area of pure CEL and NCC was found to be 10.41 and 27 m2/g, respectively. The comparative protection capacity of natural polymers CEL and NCC towards improving the SS316 alloy corrosion resistance has been assessed during the acid pickling process by electrochemical (OCP, PDP, and EIS), and weight loss (WL) measurements. The outcomes attained from the various empirical methods were matched and exhibited that the protective efficacy of these polymers augmented with the upsurge in dose in this order CEL (93.1%) < NCC (96.3%). The examined polymers display mixed-corrosion inhibition type features by hindering the active centers on the metal interface, and their adsorption followed the Langmuir isotherm model. Surface morphology analyses by SEM reinforced the adsorption of polymers on the metal substrate. The Density Functional Theory (DFT) parameters were intended and exhibited the anti-corrosive characteristics of CEL and NCC polymers. A Monte Carlo (MC) simulation study revealed that CEL and NCC polymers are resolutely adsorbed on the SS316 alloy surface and forming a powerful adsorbed protective layer.