Molecular dynamics and Monte Carlo simulations as powerful tools for study of interfacial adsorption behavior of corrosion inhibitors in aqueous phase: A review

Chitin extraction from crab shells and synthesis of chitin @metakaolin composite for efficient amputation of Cr (VI) ions

The present research study combines chitin from shrimp waste with the oxide-rich metakaolin. Metakaolin is a blend of mixed oxides rich in silica and alumina with good adsorbent properties. The chitin@metakaolin (CHt@M.K.) composite was synthesized and characterized using FTIR, SEM, TGA, XRD and XPS techniques. Cr(VI) removal studies were compared for chitin and CHt@M.K. through adsorption. It was found that the adsorption capacity of CHt@M.K. is 278.88 mg/g, almost double that of chitin, at pH 5.0 in just 120 min of adsorption. Isotherm models like Langmuir, Freundlich, Temkin and Dubinin-Radushkevich were investigated to comprehend the adsorption process. It was revealed that Langmuir adsorption isotherm is most suitable to elucidate Cr(VI) adsorption on CHt@M.K. The adsorption kinetics indicate that pseudo first order was followed, indicating that the physisorption was the process that limited the sorption process rate. The positive enthalpy change (20.23 kJ/mol) and positive entropy change (0.083 kJ/mol K) showed that the adsorption process was endothermic and more random at the solid-liquid interface. The negative free energy change over entire temperature range was an indicator of spontaneity of the process. Apart from all these, the non-covalent interactions between Cr(VI) and composite were explained by quantum calculations based models.

Recent advances in catalyst design, performance, and challenges of metal-heteroatom-co-doped biochar as peroxymonosulfate activator for environmental remediation

The escalation of global water pollution due to emerging pollutants has gained significant attention. To address this issue, catalytic peroxymonosulfate (PMS) activation technology has emerged as a promising treatment approach for effectively decontaminating a wide range of pollutants. Recently, modified biochar has become an increasingly attractive as PMS activator. Metal-heteroatom-co-doped biochar (MH-BC) has emerged as a promising catalyst that can provide enhanced performance over heteroatom-doped and metal-doped biochar due to the synergism between metal and heteroatom in promoting PMS activation. Therefore, this review aims to discuss the fabrication pathways (i.e., internal vs external doping and pre-vs post-modification) and key parameters (i.e., source of precursors, synthesis methods, and synthesis conditions) affecting the performance of MH-BC as PMS activator. Subsequently, an overview of all the possible PMS activation pathways by MH-BC is provided. Subsequently, Also, the detection, identification, and quantification of several reactive species (such as, •OH, SO4•-, O2•-, 1O2, and high valent oxo species) generated in the catalytic PMS system by MH-BC are also evaluated. Lastly, the underlying challenges associated with poor stability, the lack of understanding regarding the interaction between metal and heteroatom during PMS activation and quantification of radicals in multi-ROS system are also deliberated.

In-situ biosynthesized plant exudate gums‑silver nanocomposites as corrosion inhibitors for mild steel in hydrochloric acid medium

Natural gums due to availability, multifunctionality, and nontoxicity are multifaceted in application. In corrosion inhibition applications, their performance, in unmodified form is unsatisfactory because of high hydration rate, solubility issues, algal and microbial contamination, as well as thermal instability. This work attempts to enhance the inhibitive performance of Berlinia grandiflora (BEG) and cashew (CEG) exudate gums through various modification approaches. The potential of biogenic BEG and CEG gums-silver (Ag) nanocomposites (NCPs) for corrosion inhibition of mild steel in 1 M HCl is studied. The nanocomposites were characterized using the FTIR, UV-vis, and TEM techniques. The corrosion studies through the gravimetric and electrochemical (PDP, EIS, LPR, and EFM) analyses reveal moderate inhibition performance by the nanocomposites. Furthermore, the PDP results reveal that both inhibitors are mixed-type with maximum corrosion inhibition efficiencies (IEs) of 61.2 % and 54.2 % for BEG-Ag NCP and CEG-Ag NCP, respectively at an optimum concentration of 1.0 %. Modification of these inhibitors with iodide ion (KI) significantly increased the IE values to 90.1 % and 88.5 % for BEG-Ag NCP and CEG-Ag NCP at the same concentration. Surface observation of the uninhibited and inhibited steel samples using SEM/EDAX, 3D Surface profilometer, and AFM affirm that the modified nanocomposites are highly effective.

Assessment of Hydrazone Derivatives for Enhanced Steel Corrosion Resistance in 15 wt.% HCl Environments: A Dual Experimental and Theoretical Perspective

This study evaluates the corrosion inhibition capabilities of two novel hydrazone derivatives, (E)-2-(5-methoxy-2-methyl-1H-indol-3-yl)-N'-(4-methylbenzylidene)acetohydrazide (MeHDZ) and (E)-N'-benzylidene-2-(5-methoxy-2-methyl-1H-indol-3-yl)acetohydrazide (HHDZ), on carbon steel in a 15 wt.% HCl solution. A comprehensive suite of analytical techniques, including gravimetric analysis, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM), demonstrates their significant inhibition efficiency. At an optimal concentration of 5 × 10-3 mol/L, MeHDZ and HHDZ achieve remarkable inhibition efficiencies of 98% and 94%, respectively. EIS measurements reveal a dramatic reduction in effective double-layer capacitance (from 236.2 to 52.8 and 75.3 µF/cm2), strongly suggesting inhibitor adsorption on the steel surface. This effect is further corroborated by an increase in polarization resistance and a significant decrease in corrosion current density at optimal concentrations. Moreover, these inhibitors demonstrate sustained corrosion mitigation over extended exposure durations and maintain effectiveness even under elevated temperatures, highlighting their potential for diverse operational conditions. The adsorption process of these inhibitors aligns well with the Langmuir adsorption isotherm, implying physicochemical interactions at the carbon steel surface. Density functional tight-binding (DFTB) calculations and molecular dynamics simulations provide insights into the inhibitor-surface interaction mechanism, further elucidating the potential of these hydrazone derivatives as highly effective corrosion inhibitors in acidic environments.

A review of sodium silicate solutions: Structure, gelation, and syneresis

Sodium silicate solutions, also known as waterglass, have been found to have remarkable utility in a variety of applications. The cumulative weight of evidence from 70 years of varied analysis indicates that silicate solutions consist of a wide range of species, from monomers through oligomers, up to colloids. Moreover, the structure and distribution of these species are greatly dependent upon many parameters, such as solute concentrations, silica to alkali ratio, pH, and temperature. The most interesting and characteristic property of silicate solutions is their ability to form silica gels. Overall, despite extensive research using different spectroscopic and scattering techniques, many questions related to sodium silicate's dynamic structure, stability, polymerization, and gelation remain difficult to answer. The multitude of simultaneous reactions which restructure the silicate species at the atomic scale in response to variation in solution and environmental parameters, makes it difficult to investigate the individual events using only experimental data. Molecular modelling provides an alternative way to study the unknown areas in the aqueous silicate and silica gel systems, generating key insights into the chemical reactions at microscopic length scales. However, sufficient sampling remains a challenge for the practical use of molecular simulation for these systems. Based on both experimental and modelling studies, this review provides a detailed discussion over the structure and speciation of sodium silicate solutions, their gelation mechanism and kinetics, and the syneresis phenomenon. The goal is not only to review the current level of understanding of sodium silicate solutions, silica gels and characterization techniques suitable for studying them, but also to identify the gaps in the literature and open up opportunities for advancing knowledge about these complex systems. We believe that the future direction of research should be toward correlating atomistic, molecular, and meso-scale level details of interactions and reactions in silicate solution and establishing a fundamental understanding of its gelation mechanism and kinetics. We believe that this knowledge could eliminate the "trial and error" approach in manufacturing, and improve structural control in the synthesis of important materials derived from these solutions, such as silica gels and zeolites.

Insights into the use of two novel supramolecular compounds as corrosion inhibitors for stainless steel in a chloride environment: experimental as well as theoretical investigation

Novel supramolecular (SCPs) compounds such as: {[Ni (EIN)4(NCS)2]}, SCP1 and {[Co (EIN)4 (NCS)2]}, SCP2 have been studied using weight loss (WL) and electrochemical tests on the corrosion performance of stainless steel 304 (SS304) in 1.0 M hydrochloric acid (HCl) solution. The experimental results revealed that inhibition efficacy (η%) rises with increasing concentrations of SCPs and reached 92.3% and 89.6% at 16 × 10-6 M, 25 °C, from the WL method for SCP1 and SCP2, respectively. However, by raising the temperature, η% was reduced. Polarization measurements (PDP) showed that the SCPs molecules represent a mixed-type. The SCPs were adsorbed on a SS304 surface physically, and the Langmuir adsorption isotherm was found to govern the adsorption process. The determination of thermodynamic parameters was carried out at various temperatures. Quantum chemical calculations were calculated to prove the adsorption process of SCP components, using the molecular dynamics (MD) simulations and electron density map. The inhibition performance of SCPs for SS304 dissolution in an acidic medium was proved to be excellent through FT-IR and AFM analysis. The results obtained from all measurements exhibit a high level of agreement with each other.

Computational Exploration of Phenolic Compounds in Corrosion Inhibition: A Case Study of Hydroxytyrosol and Tyrosol

The corrosion of materials remains a critical challenge with significant economic and infrastructural impacts. A comprehensive understanding of adsorption characteristics of phytochemicals can facilitate the effective design of high-performing environmentally friendly inhibitors. This study conducted a computational exploration of hydroxytyrosol (HTR) and tyrosol (TRS) (potent phenolic compounds found in olive leaf extracts), focusing on their adsorption and reactivity on iron surfaces. Utilizing self-consistent-charge density-functional tight-binding (SCC-DFTB) simulations, molecular dynamics (MD) simulations, and quantum chemical calculations (QCCs), we investigated the molecules' structural and electronic attributes and interactions with iron surfaces. The SCC-DFTB results highlighted that HTR and TRS coordinated with iron atoms when adsorbed individually, but only HTR maintained bonding when adsorbed alongside TRS. At their individual adsorption, HTR and TRS had interaction energies of -1.874 and -1.598 eV, which became more negative when put together (-1.976 eV). The MD simulations revealed parallel adsorption under aqueous and vacuum conditions, with HTR demonstrating higher adsorption energy. The analysis of quantum chemical parameters, including global and local reactivity descriptors, offered crucial insights into molecular reactivity, stability, and interaction-prone atomic sites. QCCs revealed that the fraction of transferred electron ∆N aligned with SCC-DFTB results, while other parameters of purely isolated molecules failed to predict the same. These findings pave the way for potential advancements in anticorrosion strategies leveraging phenolic compounds.

Cellular Automata Modeling as a Tool in Corrosion Management

Cellular automata models have emerged as a valuable tool in corrosion management. This manuscript provides an overview of the application of cellular automata models in corrosion research, highlighting their benefits and contributions to understanding the complex nature of corrosion processes. Cellular automata models offer a computational approach to simulating corrosion behavior at the microscale, capturing the intricate interactions between electrochemical reactions, material properties, and environmental factors and generating a new vision of predictive maintenance. It reviews the key features of cellular automata, such as the grid-based representation of the material surface, the definition of state variables, and the rules governing cell-state transitions. The ability to model local interactions and emergent global behavior makes cellular automata particularly suitable for simulating corrosion processes. Finally, cellular automata models offer a powerful and versatile approach to studying corrosion processes, expanding models that can continue to enhance our understanding of corrosion and contribute to the development of effective corrosion prevention and control strategies.

Multi-method evaluation of a 2-(1,3,4-thiadiazole-2-yl)pyrrolidine corrosion inhibitor for mild steel in HCl: combining gravimetric, electrochemical, and DFT approaches

The corrosion inhibition properties of 2-(1,3,4-thiadiazole-2-yl)pyrrolidine (2-TP) on mild steel in a 1 M HCl solution were investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) measurements. In addition, DFT calculations were performed on 2-TP. The polarization curves revealed that 2-TP is a mixed-type inhibitor. The results indicate that 2-TP is an effective inhibitor for mild steel corrosion in a 1.0 M HCl solution, with an inhibition efficiency of 94.6% at 0.5 mM 2-TP. The study also examined the impact of temperature, revealing that the inhibition efficiency increases with an increasing concentration of 2-TP and decreases with a rise in temperature. The adsorption of the inhibitor on the mild steel surface followed the Langmuir adsorption isotherm, and the free energy value indicated that the adsorption of 2-TP is a spontaneous process that involves both physical and chemical adsorption mechanisms. The DFT calculations showed that the adsorption of 2-TP on the mild steel surface is mainly through the interaction of the lone pair of electrons on the nitrogen atom of the thiadiazole ring with the metal surface. The results obtained from the weight loss, potentiodynamic polarization, EIS and OCP measurements were in good agreement with each other and confirmed the effectiveness of 2-TP as a corrosion inhibitor for mild steel in 1.0 M HCl solution. Overall, the study demonstrates the potential use of 2-TP as a corrosion inhibitor in acid environments.

Performant removal of creatinine using few-layer-graphene/alginate beads as a kidney filter

Reduction of renal function, such as creatinine adsorption is one of the most common and dangerous diseases. Dedicated to this issue, developing high-performance, sustainable, and bio-compatible adsorbing materials is still challenging. Herein, barium alginate (BA) and BA containing few-layer graphene (FLG/BA) beads were synthesized in water from sodium alginate, also acting as bio-surfactant in in-situ exfoliation of graphite to FLG. The physicochemical characteristics of the beads demonstrated an excess of barium chloride used as a cross-linker. The efficiency and sorption capacity (Q_e) of creatinine removal increase with processing duration reaching 82.1, 99.5 %, and 68.4, 82.9 mg·g^-1 for BA and FLG/BA, respectively. The thermodynamic parameters detect the enthalpy change (ΔH°) of about -24.29 and -36.11 kJ·mol^-1 and the entropy change (ΔS°) of around -69.24 and -79.46 kJ·mol^-1 for BA and FLG/BA, respectively. During the reusability test, the removal efficiency decreases from the optimal first cycle to 69.1 and to 88.3 % in the sixth cycle for BA and FLG/BA, revealing superior stability of FLG/BA. The MD calculations confirm a higher adsorption capacity of FLG/BA composite compared to BA alone, clearly confirming a strong structure-property relation.

Corrosion Inhibition of Carbon Steel in a Sour (H2S) Environment by an Acryloyl-Based Polymer

Corrosion poses safety and operational challenges in the oil and gas field, particularly in a sour environment. Corrosion inhibitors (CIs) are thus employed to protect the integrity of industrial assets. However, CIs have the potential to dramatically impair the effectiveness of other co-additives, such as kinetic hydrate inhibitors (KHIs). Here, we propose an acryloyl-based copolymer, previously used as a KHI, as an effective CI. The copolymer formulation provided a corrosion inhibition efficiency of up to 90% in a gas production environment, implying that it can reduce or even eliminate the need for an additional dedicated CI in the system. It also demonstrated a corrosion inhibition efficiency of up to 60% under field-simulated conditions for a wet sour crude processing environment. Molecular modeling suggests that the enhanced corrosion protection is imparted by the favorable interaction of the heteroatoms of the copolymer with the steel surface, potentially displacing adhered water molecules. All in all, we show that an acryloyl-based copolymer with dual functionalities can potentially overcome issues caused by incompatibilities in a sour environment, resulting in significant cost savings and operational ease.

A comprehensive assessment of carbon steel corrosion inhibition by 1,10-phenanthroline in the acidic environment: insights from experimental and computational studies

1,10-Phenanthroline (PHN) is a nitrogen-containing heterocyclic organic compound that is widely used in a variety of applications, including chemosensors, biological studies, and pharmaceuticals, which promotes its use as an organic inhibitor to reduce corrosion of steel in acidic solution. In this regard, the inhibition ability of PHN was examined for carbon steel (C48) in a 1.0 M HCl environment by performing electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), mass loss, and thermometric/kinetic. Additionally, scanning electron microscopy (SEM) was used to examine the surface morphology of C48 immersed in 1.0 M HCl protected with our inhibitor. According to the PDP tests, increasing the PHN concentration resulted in an improvement in corrosion inhibition efficiency. Besides, the maximum corrosion inhibition efficiency is about 90% at 328 K. Furthermore, the PDP assessments demonstrated that PHN functions as a mixed-type inhibitor. The adsorption analysis reveals that our title molecule mechanism is due to physical-chemical adsorption, as predicted by the Frumkin, Temkin, Freundlich, and Langmuir isotherms. The SEM technique exhibited that the corrosion barrier occurs due to the adsorption of the PHN compound through the metal/1.0 M HCl interface. In addition, the computational investigations based on a quantum calculation using density functional theory (DFT), reactivity (QTAIM, ELF, and LOL), and molecular-scale by Monte Carlo (MC) simulations confirmed the experimental results by providing further insight into the mode of adsorption of PHN on the metal surface, thus forming a protective film against corrosion on the C48 surface.

Unraveling Bonding Mechanisms and Electronic Structure of Pyridine Oximes on Fe(110) Surface: Deeper Insights from DFT, Molecular Dynamics and SCC-DFT Tight Binding Simulations

The development of corrosion inhibitors with outstanding performance is a never-ending and complex process engaged in by researchers, engineers and practitioners. The computational assessment of organic corrosion inhibitors' performance is a crucial step towards the design of new task-specific materials. Herein, the electronic features, adsorption characteristics and bonding mechanisms of two pyridine oximes, namely 2-pyridylaldoxime (2POH) and 3-pyridylaldoxime (3POH), with the iron surface were investigated using molecular dynamics (MD), and self-consistent-charge density-functional tight-binding (SCC-DFTB) simulations. SCC-DFTB simulations revealed that the 3POH molecule can form covalent bonds with iron atoms in its neutral and protonated states, while the 2POH molecule can only bond with iron through its protonated form, resulting in interaction energies of -2.534, -2.007, -1.897, and -0.007 eV for 3POH, 3POH⁺, 2POH⁺, and 2POH, respectively. Projected density of states (PDOSs) analysis of pyridines-Fe(110) interactions indicated that pyridine molecules were chemically adsorbed on the iron surface. Quantum chemical calculations (QCCs) revealed that the energy gap and Hard and Soft Acids and Bases (HSAB) principles were efficient in predicting the bonding trend of the molecules investigated with an iron surface. 3POH had the lowest energy gap of 1.706 eV, followed by 3POH⁺ (2.806 eV), 2POH⁺ (3.121 eV), and 2POH (3.431 eV). In the presence of a simulated solution, MD simulation showed that the neutral and protonated forms of molecules exhibited a parallel adsorption mode on an iron surface. The excellent adsorption properties and corrosion inhibition performance of 3POH may be attributed to its low stability compared to 2POH molecules.

Application of molecular dynamics simulation for exploring the roles of plant biomolecules in promoting environmental health

Understanding the dynamic changes of plant biomolecules is vital for exploring their mechanisms in the environment. Molecular dynamics (MD) simulation has been widely used to study structural evolution and corresponding properties of plant biomolecules at the microscopic scale. Here, this review (i) outlines structural properties of plant biomolecules, and the crucial role of MD simulation in advancing studies of the biomolecules; (ii) describes the development of MD simulation in plant biomolecules, determinants of simulation, and analysis parameters; (iii) introduces the applications of MD simulation in plant biomolecules, including the response of the biomolecules to multiple stresses, their roles in corrosive environments, and their contributions in improving environmental health; (iv) reviews techniques integrated with MD simulation, such as molecular biology, quantum mechanics, molecular docking, and machine learning modeling, which bridge gaps in MD simulation. Finally, we make suggestions on determination of force field types, investigation of plant biomolecule mechanisms, and use of MD simulation in combination with other techniques. This review provides comprehensive summaries of the mechanisms of plant biomolecules in the environment revealed by MD simulation and validates it as an applicable tool for bridging gaps between macroscopic and microscopic behavior, providing insights into the wide application of MD simulation in plant biomolecules.

High-performance corrosion resistance of chemically-reinforced chitosan as ecofriendly inhibitor for mild steel

Finding new cost-effective and environmentally friendly anti-corrosion materials is a never-ending task. The present study is to prepare a new formulation based on chitosan derivatives with different degrees of substitution (chitosan-5-HMF) as an efficient green corrosion inhibitor to protect mild steel against corrosion in 1 M HCl. The inhibition performance of chitosan-5-HMF was determined by electrochemical tests coupled with theoretical study like as molecular dynamics (MD) simulations to assess the reactivity and adsorption mechanisms between chitosan-5-HMF and Fe. The obtained results revealed that chitosan-5-HMF3 performs excellently inhibition performance where its inhibition efficiency reached 97.01% at 200 mg/L, and it acted as an anode-based mixed inhibitor. SEM and contact angle analysis showed the formation of compact chitosan-5-HMF film on the steel surface. Molecular dynamic simulations also manifested that chitosan-5-HMF was absorbed more strongly on the metal surface in a parallel mode.

Palmitic acid-based amide as a corrosion inhibitor for mild steel in 1M HCl

Due to growing environmental concerns and regulations limiting the use of harmful and toxic synthetic corrosion inhibitors, there is a high demand for sustainable corrosion inhibitors. In this study, a green and rapid technique was used to synthesize amide N-(4-aminobutyl)palmitamide (BAPA) which yielded 91.17% of the product within 2 min, compared to a low yield of 75-80% and a very long 8-10 h reaction time with the conventional thermal condensation method. The chemical structure of BAPA was analyzed by FT-IR, 1HNMR and 13CNMR spectra, as well as CHNS elemental analysis. When applied to mild steel exposed to 1 M HCl, BAPA delayed and reduced corrosion by adsorbing to the steel surface to form a protective layer. The inhibition efficiency increased with increasing amide concentration, and maximal inhibition of 91.5% was observed at 0.5 mM BAPA. The adsorption of BAPA on mild steel in an acidic solution was studied and inhibition performance was correlated with the calculated adsorption-free energy ΔGads, indicating good agreement between the experimental and adsorption findings. Surface morphology of untreated and treated mild steel coupons was evaluated by SEM, and based on density functional theory (DFT) computations and atomic charges analysis, a stronger interaction was observed between BAPA and mild steel surface leading to the formation of a compact protective film on the metallic surface. This protective film is attributed to the presence of nitrogen atoms and carbonyl group in the chemical structure of BAPA.

Molecular Dynamics Simulations of Nitric Oxide Scattering Off Graphene

We performed classical molecular dynamics simulations to model the scattering process of nitric oxide, NO, off graphene supported on gold. This is motivated by our desire to probe the energy transfer in collisions with graphene. Since many of these collision systems comprising of graphene and small molecules have been shown to scatter non-reactively, classical molecular dynamics appear to describe such systems sufficiently. We directed thousands of trajectories of NO molecules onto graphene along the surface normal, while varying impact position, but also speed, orientation, and rotational excitation of the nitric oxide, and compare the results with experimental data. While experiment and theory do not match quantitatively, we observe agreement that the relative amount of kinetic energy lost during the collision increases with increasing initial kinetic energy of the NO. Furthermore, while at higher collision energies, all NO molecules lose some energy, and the vast majority of NO is scattered back, in contrast at low impact energies, the fraction of those nitric oxide molecules that are trapped at the surface increases, and some NO molecules even gain some kinetic energy during the collision process. The collision energy seems to preferentially go into the collective motion of the carbon atoms in the graphene sheet.

Experimental and Quantum Chemical Investigations on the Anticorrosion Efficiency of a Nicotinehydrazide Derivative for Mild Steel in HCl

A corrosion inhibitor namely N′-(4-hydroxy-3-methoxybenzylidene) nicotinohydrazide was synthesized and the inhibition efficiency of the investigated inhibitor toward the mild steel corrosion in 1 M HCl was studied. The anticorrosion effect has been investigated by weight loss (WL) techniques and electrochemical analysis includes potentiodynamic polarization (PDP) studies and electrochemical impedance spectroscopy (EIS). The current investigation has demonstrated that the tested inhibitor is suitable in corrosive environment and the inhibitive efficacy up to 97% in 1 M HCl. PDP measurements showed that the nicotinohydrazide is a mixed type inhibitor. EIS measurements showed that an increase in the inhibitory concentration leads to an increase in the charge transfer resistance (Rct) and a decrease in the double-layer capacitance (Cdl). Experimental results for the inhibitory performance of WL methods and electrochemical techniques (PDP and EIS) are in good agreement. The tested inhibitor molecules adsorbed on the surface of mild steel in a hydrochloric acid solution followed Langmuir’s isothermal adsorption. Quantum chemical parameters based on density function theory (DFT) techniques were conducted on oxygen/nitrogen-bearing heterocyclic molecule employed as a corrosion inhibitor for mild steel in HCl to evaluate the correlation between the inhibitor structure and inhibitory performance. The parameters including the energy gap (ΔE), dipole moment (μ), electronegativity (χ), electron affinity (A), global hardness (η), softness (σ), ionization potential (I), the fraction of electrons transferred (ΔN), the highest occupied molecular orbital energy (EHOMO), and the lowest unoccupied molecular orbital energy (ELUMO) were also calculated and were in good agreement with the experimental results.

Efficient Synthesis of 6,7-Dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile Compounds and Their Applicability As Inhibitor Films for Steel Alloy Corrosion: Collective Computational and Practical Approaches

An effective method for designing new heterocyclic compounds of 6,7-dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile derivatives (CAPDs) was presented through cyclocondensation reaction between 2,5-diarylidenecyclopentanone derivatives and propanedinitrile, and the cyclocondensation reaction succeeded using a sodium alkoxide solution (sodium ethoxide or sodium methoxide) as the reagent and the catalyst. The synthesized CAPD derivatives were employed as novel inhibitors for carbon steel (CS) corrosion in a molar H2SO4 medium. The corrosion protection proficiency was investigated by electrochemical measurements (open circuit potential vs time (E OCP vs t), potentiodynamic polarization plots (PDP), and electrochemical impedance spectroscopy (EIS)) and surface morphology (scanning electron microscopy (SEM)) examinations. The results show that the CAPD derivatives exhibit mixed type inhibitors and a superior inhibition efficiency of 97.7% in the presence of 1.0 mM CAPD-1. The adsorption of CAPD derivatives on the CS interface follows the Langmuir isotherm model, including physisorption and chemisorption. Scanning electron microscopy (SEM) exploration confirmed the adsorption of the CAPD derivatives on the CS substrate. Monte Carlo (MC) simulations and DFT calculations revealed that the efficacy of the CAPD molecules correlates well with their structures, and this protection was attributed to their adsorption on the CS surface.

Review on the Recent Development of Fatty Hydrazide as Corrosion Inhibitor in Acidic Medium: Experimental and Theoretical Approaches

In recent years, numerous research work has been conducted in order to find the most practical and cost-effective solution for corrosion issues in the oil and gas industry. Several studies have revealed that fatty hydrazide derivatives are the most suitable corrosion inhibitor for the application in the said industry. These compounds can also act as effective corrosion inhibitors in acidic medium with inhibition efficiency greater than 95%. This review summarizes and discusses the recent corrosion inhibitor development in acidic media from 2017 until 2021, focusing on fatty hydrazide derivatives. The significant findings and mechanisms of inhibition have been elucidated. In addition, intake on the computer simulation studies of fatty hydrazide inhibition properties is also included in this review. Finally, some suggestions for future research on corrosion inhibitors have been recommended.

Organic Compounds as Corrosion Inhibitors for Carbon Steel in HCl Solution: A Comprehensive Review

Most studies on the corrosion inhibition performance of organic molecules and (nano)materials were conducted within “carbon steel/1.0 M HCl” solution system using similar experimental and theoretical methods. As such, the numerous research findings in this system are sufficient to conduct comparative studies to select the best-suited inhibitor type that generally refers to a type of inhibitor with low concentration/high inhibition efficiency, nontoxic properties, and a simple and cost-economic synthesis process. Before data collection, to help readers have a clear understanding of some crucial elements for the evaluation of corrosion inhibition performance, we introduced the mainstay of corrosion inhibitors studies involved, including the corrosion and inhibition mechanism of carbon steel/HCl solution systems, evaluation methods of corrosion inhibition efficiency, adsorption isotherm models, adsorption thermodynamic parameters QC calculations, MD/MC simulations, and the main characterization techniques used. In the classification and statistical analysis section, organic compounds or (nano)materials as corrosion inhibitors were classified into six types according to their molecular structural characteristics, molecular size, and compound source, including drug molecules, ionic liquids, surfactants, plant extracts, polymers, and polymeric nanoparticles. We outlined the important conclusions obtained from recent literature and listed the evaluation methods, characterization techniques, and contrastable experimental data of these types of inhibitors when used for carbon steel corrosion in 1.0 M HCl solution. Finally, statistical analysis was only performed based on these data from carbon steel/1.0 M HCl solution system, from which some conclusions can contribute to reducing the workload of the acquisition of useful information and provide some reference directions for the development of new corrosion inhibitors.

Molecular dynamics study of three amino acids as corrosion inhibitor for copper in hydrochloric acid solution

Molecular dynamics (MD) simulation is used to study the corrosion inhibition mechanism of cysteine (Cys), glutamic (Glu) and glycine (Gly) for copper in hydrochloric acid solution. The adsorption energy and radial distribution function results show that all three amino acids can spontaneously adsorb on Cu (111) surface by chemical adsorption. The absolute value of adsorption energy and intensity is Cys > Glu > Gly. The diffusion coefficient and relative concentration curve show that all the three amino acids can inhibit the diffusion and aggregation ability of corrosion particles, so the three amino acids not only can slow down the aggregation of corrosive particles, but also effectively repel corrosive particles to protect the substrate. The inhibition ability obtained by the MD simulation shows the trend of Cys > Glu > Gly, which is consistent with the experimental results. The inhibition efficiency is determined by both the adsorption strength on the substrate surface and inhibition ability for the diffusion and aggregation ability of corrosion particles.

Ab initio molecular dynamics simulations on the adsorption of 1-hydroxyethane-1,1-diphosphonic acid on the iron (100) surface

Through IRI, Bader charges and ELF analysis, an electrostatic interaction network exists between HEDP and the iron (100) surface, which is responsible for the stability of the adsorption state.