The investigation of corrosion inhibition efficiency on some benzaldehyde thiosemicarbazones and their thiole tautomers: Computational study

In Silico Approaches for Some Sulfa Drugs as Eco-Friendly Corrosion Inhibitors of Iron in Aqueous Medium

This paper addresses the prediction of the adsorption behavior as well as the inhibition capacity of non-toxic sulfonamide-based molecules, also called sulfa drugs, on the surface of mild steel. The study of the electronic structure was investigated through quantum chemical calculations using the density functional theory method (DFT) and the direct interaction of inhibitors with the iron (Fe) metal surface was predicted using the multiple probability Monte Carlo simulations (MC). Then, the examination of the solubility and the environmental toxicity was confirmed using a chemical database modeling environment website. It was shown that the presence of substituents containing heteroatoms able to release electrons consequently increased the electron density in the lowest unoccupied and highest occupied molecular orbitals (LUMO and HOMO), which allowed a good interaction between the inhibitors and the steel surface. The high values of EHOMO imply an ability to donate electrons while the low values of ELUMO are related to the ability to accept electrons thus allowing good adsorption of the inhibitor molecules on the steel surface. Molecular dynamics simulations revealed that all sulfonamide molecules adsorb flat on the metal surface conforming to the highly protective Fe (1 1 0) surface. The results obtained from the quantum chemistry and molecular dynamics studies are consistent and reveal that the order of effectiveness of the sulfonamide compounds is P7 > P5 > P6 > P1 > P2 > P3 > P4.

The anti-corrosive behavior of benzo-fused N-heterocycles: an in silico study toward developing organic corrosion inhibitors

The work provides a computational protocol to predict the anti-corrosive performance of organic molecules through three successive phases of calculations; electron propagator theory (EPT), Monte Carlo (MC) simulations, and the density functional based tight-binding (DFTB) method. The protocol was applied to investigate the influence of two structural factors on the anti-corrosive performance of benzo fused-N-heterocycles (BFNHs) against the Fe(110) surface in an acidic medium; positional isomerism and the gradual insertion of nitrogen atoms in the heterocycle ring. The choice of BFNHs is attributed to their anti-corrosion activity and their use as building blocks in the molecular structure of many organic inhibitors. The findings indicate that EPT is a safe method for calculating the quantum chemical descriptors of the isolated molecules. Besides, the current work recommends using MC simulations and the DFTB method to describe the physical and chemical adsorption, respectively. Unexpected results were observed, as the gradual insertion of nitrogen atoms is not a specific factor for improving the inhibition efficiency of BFNHs. The findings were crystallized in equations linking the physical and chemical adsorption energies with the quantum chemical descriptors with a correlation exceeding 0.75. Besides, the peri steric hindrance plays an influential role in chemical adsorption. Intriguingly, the continuous introduction of nitrogen atoms does not increase the efficiency of the inhibitor along the way. For example, phthalazine exhibited better efficiency than benzotetrazine. In light of the above, the present protocol helps understand the anti-corrosive behavior of organic inhibitors and provides a feasible method to develop novel corrosion inhibitors.

Quantum Chemical and Monte Carlo Simulation Studies on Inhibition Performance of Caffeine and Its Derivatives against Corrosion of Copper

Performance tests on caffeine’s corrosion inhibition properties and their derivatives against copper corrosion have been previously reported experimentally using gravimetric and electrochemical analyses. The test was able to measure the efficiency of their corrosion inhibition accurately. However, the caffeine and its derivatives’ structure patterns and coating mechanisms when interacting with metals during copper corrosion inhibition have not been explained in detail by experimental studies. In the present study, the theoretical density functional study (DFT), ab initio MP2, and Monte Carlo simulation approaches explain the problem. The geometrical and quantum chemical parameters of inhibitors were compared under normal and protonated conditions in the gas and aqueous environments. Theoretical studies can accurately determine the molecule’s geometrical parameters and successfully explain the quantum parameters of inhibitors. Molecular dynamics are applied to study the mechanism of interaction between inhibitors and metal surfaces in an explicit water molecule environment. The energy absorption of caffeine and its derivatives on metal surfaces was linear, with quantum parameters calculated from the density functional theory and an ab initio approach. Furthermore, these theoretical study results align with the previously reported experimental studies published by de Souza et al. The inhibition efficiency ranking of studied molecules preventing copper corrosion was caffeine > theobromine > theophylline. This theoretical approach is expected to bridge the gap in designing effective corrosion inhibitors.

Synthesis, characterization and theoretical determination of corrosion inhibitor activities of some new 4,5-dihydro-1H-1,2,4-Triazol-5-one derivatives

Nine novel {bis-4-[(3-alkyl-5-oxo-1H-1,2,4-triazol-4(5H)-yl)-iminomethyl]-phenyl} [1,1'-biphenyl]-4,4'-disulfonates were synthesized and their structures were determined with spectral methods. Corrosion inhibitor activities of the title compounds were investigated using quantum mechanical methods. The parameters such as the Energy of the Highest Occupied Molecular Orbital (E_HOMO), Energy of the Lowest Unoccupied Molecular Orbital (E_LUMO), energy gap (ΔE = E_LUMO - E_HOMO) and dipole moment (μ) which are related to the corrosion effectivity of the organic compounds whose the molecular geometry and electronic properties are especially studied, were determined by using the density function theory method. Using these calculation results, properties such as hardness (ɳ), softness (σ), electronegativity (χ) values were calculated. Also quantum chemical parameters such as the fraction of transferred electrons (ΔN) between the iron surface and the 4,5-dihydro-1H-1,2,4-triazole-5-one derivative compounds were calculated. It has been discussed that which parameters have a good linear relationship with inhibition efficiency. The results of the calculations show that there is a close relationship between the activity of organic-based corrosion inhibitors showing good corrosion inhibitor activity and the calculated quantum chemical parameters of the process. Thus, corrosion inhibitor activity can be predicted without conducting an experimental study.

Electrochemical Studies of Monoterpenic Thiosemicarbazones as Corrosion Inhibitor for Steel in 1 M HCl

We have studied the inhibitory effect of some Monoterpenic Thiosemicarbazones on steel corrosion in 1 M HCl solution. The potentiodynamic polarization and electrochemical impedance spectroscopy were used. The Monoterpenic Thiosemicarbazones have inhibited significantly the dissolution of steel. The inhibition efficiency increased with increasing inhibitor concentration and also with the increase in temperature (293–323 K). Furthermore, the results obtained revealed that the adsorption of inhibitor on steel surface obeys Langmuir adsorption model and the thermodynamic parameters such as enthalpy and activation energy were determined. The scanning electron microscopy combined with dispersive X-ray spectroscopy examinations were used to see the shape of the surface morphology and to determine the elemental composition. Scanning electron microscope (SEM) images show that the surface damage decreases when the inhibitor is added. The quantum chemical calculations using density functional theory (DFT) were performed in order to provide some insights into the electronic density distribution as well as the nature of inhibitor-steel interaction.

Strychnos nuxvomica, Piper longum and Mucuna pruriens seed extracts as eco-friendly corrosion inhibitors for copper in nitric acid

The inhibitive effect of the Strychnos nuxvomica (SN), Piper longum (PL) and Mucuna pruriens (MP) seeds extract on the corrosion of copper in 3 M HNO₃ solution was studied using gravimetric and electrochemical techniques.