Electrochemical and computational insights into the utilization of 2, 2- dithio bisbenzothiazole as a sustainable corrosion inhibitor for mild steel in low pH medium.

Industries today place a high premium on environmentally friendly supplies that may effectively inhibit metal dissolution at a reasonable cost. Hence, in this paper, we assessed the corrosion inhibition effectiveness of the Thiazole derivative namely, 2, 2-Dithio Bisbenzothiazole (DBBT) against mild steel (MS) corrosion in 1 M HCl. Several experimental approaches, including gravimetric analysis, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and surface exploration using scanning electron/atomic force microscopy (SEM/AFM) and contact angle (CA), were utilized to conduct the measurements. In 1 M HCl corrosive medium at 298 K in the subsistence of 800 ppm of DBBT, this experiment indicated DBBT as an environment-friendly and sustainable corrosion inhibitor (CI) for MS, demonstrating an inhibition efficiency (IE %) of 97.71%. To deliver a deeper knowledge of the mechanism behind inhibitive behavior, the calculated thermodynamic and activation characteristics were applied. The calculated Gibbs free energy values indicated that the CI interacted physically and chemically with the MS surface, validating physio-chemical adsorption. The findings of the EIS research revealed that an upsurge in the doses of the CI is escorted by an upsurge in polarization resistance (Rp) from (88.05 → 504.04) Ωcm2, and a diminution in double layer capacitance (Cdl) from (97.46 → 46.33) µFcm-2 at (50 → 800) ppm respectively, affirming the inhibitive potential of DBBT. Additionally, the greatest displacement in Ecorr value being 76.13 mV < 85 mV, indicating that DBBT act as a mixed-form CI. To study the further impacts of DBBT on the inhibition capabilities of the compound under investigation, density functional theory (DFT) and molecular dynamics (MD) simulation were employed. Chemical and electrochemical approaches are in agreement with the computational analysis indicating DBBT is the most efficient CI.

Adsorption and anti-corrosion characteristics of vanillin Schiff bases on mild steel in 1 M HCl: experimental and theoretical study.

Herein, two Schiff base derivatives of vanillin and divanillin with 2-picolylamine, namely, 2-methoxy-4-((pyridin-2-ylmethylimino)methyl)phenol (compound A) and 3,3'-dimethoxy-5,5'-bis-((pyridin-2-ylmethylimino)methyl)-[1,1'-biphenyl]-2,2'-diol (compound B), respectively, were synthesized. Additionally, their adsorption characteristics and corrosion inhibition behavior were compared for mild steel in 1 M HCl using electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss methods. Compound B was found to impart a better anti-corrosive effect (around 95% inhibition efficiency at 313 K) than compound A. The inhibitors act as effective mixed-type inhibitors and exhibit Langmuir-type adsorption behaviour. The kinetic-thermodynamic parameters together with the data obtained from density functional theory (DFT) and molecular dynamics (MD) simulations illustrate the mechanism of corrosion and mode of adsorption of both inhibitors on the metal surface. The better corrosion mitigation propensity of the dimeric form of the inhibitor (compound B) over the monomeric form (compound A) was tested experimentally and explained according to the theoretical data.

Triazole-modified chitosan: a biomacromolecule as a new environmentally benign corrosion inhibitor for carbon steel in a hydrochloric acid solution.

In this work, a new inhibitor, triazole modified chitosan, was synthesized for the first time following chemical modification of chitosan using 4-amino-5-methyl-1,2,4-triazole-3-thiol. The newly synthesized biopolymer (CS-AMT) was characterized using FTIR and NMR, and then it was evaluated as an inhibitor against corrosion of carbon steel in 1 M hydrochloric acid. The corrosion testing and evaluation were performed thoroughly employing the weight loss method, electrochemical measurements and surface analysis. A maximum corrosion inhibition efficiency of >95% was obtained at 200 mg L-1 concentration of inhibitor. The adsorption of inhibitor obeyed the Langmuir isotherm and showed physical and chemical adsorption. The electrochemical study via impedance analysis supported the adsorption of the inhibitor on the surface of carbon steel, and the potentiodynamic polarization indicated a mixed type of inhibitor behavior with cathodic predominance. To get a better insight on the interaction of inhibitor molecules with the metal surface, a detailed theoretical study was performed using DFT calculations, Fukui indices analysis and molecular dynamics (MD) simulation. The DFT study showed a lower energy gap of CS-AMT and the MD simulations showed an increased binding energy of CS-AMT compared to the parent chitosan and triazole moieties thereby supporting the experimental findings.

Newly synthesized quercetin derivatives as corrosion inhibitors for mild steel in 1 M HCl: combined experimental and theoretical investigation.

To evaluate the corrosion inhibition efficacy of the derivatives of naturally available organics, mono and di-4-((2-hydroxyethyl)piperazin-1-yl)methyl derivatives of quercetin, a flavonoid, have been synthesized. Their potential as anti-corrosive agents is assessed for mild steel in 1 M HCl employing the weight-loss technique as well as electrochemical methods. Comparing the rate of corrosion in uninhibited and inhibited solutions as a function of temperature, the thermodynamic parameters of adsorption of these derivatives on mild steel surfaces and the kinetic parameters of the corrosion process are evaluated. These parameters together with information derived from electrochemical methods are further used to ascertain the mechanism of corrosion and mode of adsorption of inhibitors with intricate detail. Density functional theory (DFT) calculations were employed to explain the relative corrosion inhibition propensity between the studied mono and di quercetin derivatives. Molecular dynamics (MD) simulations were carried out to obtain the interaction energy between the inhibitor molecules and the metal surface. Results show that both derivatives, acting as mixed-type inhibitors, exert profound anti-corrosive influence (around 95% inhibition efficiency at 1 mM concentration at 313 K). Theoretical studies suggest that the trihydroxy chromone ring and dihydroxy phenyl ring of quercetin maintain a planar orientation with respect to each other and are adsorbed on the metal surface (mostly chemisorption).

Novel Schiff-base molecules as efficient corrosion inhibitors for mild steel surface in 1 M HCl medium: experimental and theoretical approach.

In order to evaluate the effect of the functional group present in the ligand backbone towards corrosion inhibition performances, three Schiff-base molecules namely, (E)-4-((2-(2,4-dinitrophenyl)hydrazono)methyl)pyridine (L(1)), (E)-4-(2-(pyridin-4-ylmethylene)hydrazinyl)benzonitrile (L(2)) and (E)-4-((2-(2,4-dinitrophenyl)hydrazono)methyl)phenol (L(3)) were synthesized and used as corrosion inhibitors on mild steel in 1 M HCl medium. The corrosion inhibition effectiveness of the studied inhibitors was investigated by weight loss and several sophisticated analytical tools such as potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Experimentally obtained results revealed that corrosion inhibition efficiencies followed the sequence: L(3) > L(1) > L(2). Electrochemical findings showed that inhibitors impart high resistance towards charge transfer across the metal-electrolyte interface and behaved as mixed type inhibitors. Scanning electron microscopy (SEM) was also employed to examine the protective film formed on the mild steel surface. The adsorption as well as inhibition ability of the inhibitor molecules on the mild steel surface was investigated by quantum chemical calculation and molecular dynamic (MD) simulation. In quantum chemical calculations, geometry optimized structures of the Schiff-base inhibitors, electron density distribution in HOMO and LUMO and Fukui indices of each atom were employed for their possible mode of interaction with the mild steel surfaces. MD simulations revealed that all the inhibitors molecules adsorbed in parallel orientation with respect to the Fe(110) surface.

Adsorption and corrosion inhibition effect of Schiff base molecules on the mild steel surface in 1 M HCl medium: a combined experimental and theoretical approach.

Corrosion inhibition performance of 2-(2-hydroxybenzylideneamino)phenol (L(1)), 2-(5-chloro-2-hydroxybenzylideneamino)phenol (L(2)) and 2-(2-hydroxy-5-nitrobenzylideneamino)phenol (L(3)) on the corrosion behaviour of mild steel surface in a 1 M hydrochloric acid (HCl) solution is investigated by sophisticated analytical methods like potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss measurements. Polarization studies showed that all the compounds are mixed type (cathodic and anodic) inhibitors and the inhibition efficiency (η%) increased with increasing inhibitor concentration. The inhibition actions of these Schiff base molecules are discussed in view of blocking the electrode surface by means of adsorption of the inhibitor molecule obeying the Langmuir adsorption isotherm. Scanning electron microscopy (SEM) studies of the metal surfaces confirmed the existence of an adsorbed film. Density functional theory (DFT) and molecular dynamics (MD) simulation have been used to determine the relationship between molecular configuration and their inhibition efficiencies. The order of inhibition performance obtained from experimental results is successfully verified by DFT and MD simulation.

Exploratory studies towards various anion recognition chemistry by two different sized cleft shaped organic ligands.

Indole and urea based two organic receptors have been synthesized by an easy synthetic process. These two receptors have strong sensitivity and selectivity for several bio-relevant anions. Receptor 1 and 2 were synthesized from indole-2-carboxylic acid and p-anisidine respectively, which are low cost starting materials. Receptor 1 can selectively sense anions like F(-), OAc(-) and H2PO4(-), while receptor 2 can only sense F(-) and H2PO4(-). Both receptors are silent toward anions like Cl(-), Br(-), I(-) and NO3(-). It is the difference in their shape and size which are responsible for different anion sensing. The nature of these host-guest type interactions was analyzed by convenient spectrophotometric techniques like UV-Vis, fluorescence, (1)H NMR, FT-IR studies and also confirmed by electrochemical techniques like cyclic voltammetry studies of the two ligand receptors with convenient anions. Between receptor 1 and 2, receptor 2 was crystallographically characterized also.