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{(1Z)-2-oxo-N′-phenyl-N-quinolin-8-ylpropanehydrazonamide (H2L-H) and (1Z)-N′-(4-bromophenyl)-2-oxo-N-quinolin-8-ylpropanehydrazonamide (H2L-Br)} have been studied as corrosion inhibitors of carbon steel in 1 M HCl medium by the weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy EIS, scanning electron microscopy SEM coupled with Energy Dispersion X-Ray Spectroscopy EDS, Atomic Force Microscopy AFM, IR and UV-visible spectroscopy. The inhibition efficacy has been shown to increase with increasing inhibitor concentration. The corrosion of the carbon steel is mainly controlled by a charge transfer process. The temperature effect was evidenced and the thermodynamic parameters were calculated. The adsorption of the inhibitors on the metal surface obeyed the Langmuir adsorption isotherm. The hydrodynamic effect and the synergetic effect have been implemented. Inhibitory efficiency decreases with increasing rotation speed and the used additives adsorb cooperatively to form a protective layer on the metal surface. The results obtained by the experimental measurements and those of the theoretical calculations (DFT and MD simulation) are in good correlation. Equilibrium adsorption configurations of H2L-Br on Fe (1 1 0) surface obtained by molecular dynamic simulations [ABSTRACT FROM AUTHOR]

The inhibition effect of a new Schiff base, namely, 4,4′-thio bis{N-[ (E ) -phenol-3-ylmethylidene]aniline}(SB), on the corrosion of mild steel (MS) in a 1M HCl solution was investigated under both hydrodynamic flow and a stagnant environment at different temperatures and concentrations. To assess the inhibition effect, different characterization techniques have been used including the measurement of weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was found that the inhibition efficiency increases with the increase of the inhibitor concentration and decreases when the temperature increases. The adsorption of the inhibitor on the surface of MS obeys the Langmuir isotherm. The surfaces of MS, after being exposed to test solutions, were examined by atomic force microscopy (AFM). [ABSTRACT FROM AUTHOR]

The study of the corrosion inhibition of mild steel in acid medium 1 M HCl by the Schiff base compounds named {4,4′-Bis(pyrrole-2-carboxaldehyde) diphenyl diimino sulfide (L1) and 4,4′-Bis(thiophene-2-carboxaldehyde) diphenyl diimino sulfide (L2)} was carried out using various techniques: weight loss measurements, polarization curves, electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The influence of the concentration, immersion time and temperature was examined and the mode of adsorption of these inhibitors on the surface of the metal was highlighted by assigning the appropriate isotherm. The experimental results indicate that these compounds are effective corrosion inhibitors and the inhibitory competence rises with increasing inhibitor concentration. The adsorption of these compounds on the mild steel surface obeys the isotherm of Langmuir. The correlation between the molecular structures and the inhibitory properties of the compounds studied was performed using the Density Functional Theory (DFT) method. Furthermore, molecular dynamics (MD) simulation has been taken into account. The results indicate that the adsorption energy of L1 was less than L2, which is in accordance with the experimentally determined inhibition effect. [ABSTRACT FROM AUTHOR]

In this work, we have synthesized three diethyl (phenylamino) methyl) phosphonate derivatives: Diethyl(phenyl(phenylamino)methyl)phosphonate(DEPAMP), Diethyl(((2-meth oxyphenyl(phenylamino)methyl)phosphonate (o-DEPAMP), Diethyl(((4-methoxy phenyl(phe nylamino)methyl)phosphonate (p-DEPAMP), whose the yields were 92%, 86% and 88% respectively. After confirmation of their structures by UV–Vis, FT-IR and NMR spectroscopic methods, the synthesized compounds were investigated as corrosion inhibitors of XC48 carbon steel in 1 mol L−1 HCl medium. The results show that the Para position is a better inhibitor in 10−3 mol L−1. Atomic Force Microscopy (AFM) was required for metallic surface characterization and the quantum chemical parameters were calculated using the Density Functional Theory (DFT) method. The adsorption energies of the inhibitors on Fe (110) surface in gas and aqueous phases were premeditated adopting the Molecular Dynamics Simulation (MDS) method. This study described the successful performance of these compounds in corrosion using weight loss measurements, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS), and discusses the correlation between experimental and theoretical, presumed DFT and MDS finding. The adsorption studies on surface were in agreement with the Langmuir adsorption isotherm model. The effects of position of OCH 3 group located at ortho and para or without in chemical structure of aminophosphonates on the corrosion inhibition efficiencies of the compounds were also investigated. Image 1 • Synthesis and structural studies of three α-aminophosphonate derivatives. • The compounds (DEPAMP), (o-DEPAMP), (p-DEPAMP) are effective corrosion inhibitors. • High E HOMO and low E LUMO with a small Δ Ε gap confirmed a good inhibition efficiency. • The inhibition efficiency of the best inhibitor p-DEPAMP reached 98%. • All inhibitors can be adsorbed on Fe (110) with a high adsorption energy. [ABSTRACT FROM AUTHOR]

Solvent and catalyst-free synthesis of two bis-phosphonic acids were realized adopting one-pot reaction of 2,6-bis (hydroxymethyl)-4-methoxyphenol or 4-chloro- 2,6-bis (hydroxymethyl) phenol with trialkyl phosphite. Their structures were confirmed by 1H, 13C, 31P NMR and IR spectroscopies. The molecular structures have been optimized using DFT, and the related calculated vibrational frequencies and NMR shift confirm the proposed structures. Chemical and electrochemical tests evaluated the inhibitive capabilities on the XC48 steel corrosion against 1 M HCl. The weight loss (chemical one) shows that the adsorption on the XC48 steel surface obeys to Langmuir isotherm, while the polarization measurements suggest that the inhibition process is mixt, the results of Electrochemical Impedance Spectroscopy (EIS) prove an increase of the inhibition efficiency with the increase of inhibitor concentrations. The surface topographies were analyzed by the Atomic Force Microscopy (AFM). The Density Functional Theory (DFT) with B3LYP as correlation function and 6-31G (p, d) as basis sets were used to determine some theoretical physic-chemical parameters affecting the corrosion inhibition and on the other hand the DFT develop the Frontier Molecular Orbitals (FMOs) and the Molecular Electrostatic Potentials (MEP) and through a discussion was made about their relationship with the inhibition of the corrosion. At the end, Molecular Dynamics Simulations (MDS) based on Monte-Carlo calculations were accomplished to simulate the interface configuration between the inhibitor molecules and Fe (110)/H 2 O. Image 1 • Bis-phosphonic acids were synthesized and experimentally/theoretically identified. • Inhibition efficiency increases with concentration but decrease with temperature. • They inhibit the corrosion by the chemical adsorption via the Langmuir isotherm. • Polarization studies showed that inhibitors act as mixt inhibitors. • Quantum chemical parameters were in good correlation with experimental results. [ABSTRACT FROM AUTHOR]