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The adsorption and corrosion inhibition properties of three triazepines carboxylate substituted compounds, namely, ethyl 4,9-bis(4-chlorophenyl)-8-cyano-3-hydroxy-2,7-dioxo-1,2,5,7-tetrahydropyrido[1,2-b]triazepine-10-carboxylate (2Cl–Et), methyl 4,9-bis(4-chlorophenyl)-8-cyano-3-hydroxy-2,7-dioxo-1,2,5,7-tetrahydropyrido[1,2-b]triazepine-10-carboxylate (2Cl–Me), and ethyl 9-(4-chlorophenyl)-8-cyano-3-hydroxy-2,7-dioxo-4-(p-tolyl)-1,2,5,7-tetrahydropyrido[1,2-b]triazepine-10-carboxylate (Cl–Me–Et) on mild steel corrosion in 1.0 M of hydrochloride acid were investigated by using weight loss, electrochemical, and theoretical investigations. It is found that these compounds act as excellent inhibitors and their inhibition efficiencies follow the order: 2Cl–Me > 2Cl–Et > Cl–Me–Et, and they depend on the type of the substituent. In addition, the possible relations between the experimental and theoretical parameters were discussed. It is found that the theoretical parameters confirmed those obtained by experimental studies. Surface roughness morphology for mild steel before and after hydrochloric acid attack is investigated and discussed using 3D-profilometry images. The scanning electron microscope (SEM) images of the corrosion product confirmed the protection offered by triazepines carboxylate derivatives on the surface of the metal immersed in both media. © 2018, Springer International Publishing AG, part of Springer Nature.

International audience; Three new organic compounds primarily based on 8-hydroxyquinoline have been successfully synthesized and characterized via different spectroscopic methods (FTIR, H-1, and C-13 NMR). The synthesized compounds, namely 5-propoxymethyl-8-hydroxyquinoline (PMHQ), 5-methoxymethyl-8-hydroxyquinoline (MMHQ) and 5-hydroxymethyl-8-hydroxyquinoline (HMHQ), were evaluated as corrosion inhibitors for carbon steel in 1 M HCl solution using electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss measurements at 298 K. Electrochemical measurements confirmed that the newly synthesized 5-alkoxymethyl-8-hydroxyquinoline derivatives are mixed type corrosion inhibitors and confirmed maximum protection efficiencies of 94, 89 and 81% for PMHQ, MMHQ, and HMHQ, respectively, at the optimum concentration of 10(-3) M. The EIS spectra confirmed a slightly depressed semi-circle profile with a single time constant in Bode diagrams for the three organic compounds over the whole concentration and temperature ranges studied. The adsorption of PMHQ, MMHQ, and HMHQ on the carbon steel surface followed the Langmuir adsorption isotherm. In addition, the kinetic and thermodynamic parameters for carbon steel corrosion and inhibitor adsorption, respectively, were determined and discussed. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses supported the formation of a protective film on carbon steel in the presence of PMHQ, MMHQ, and HMHQ. Density functional theory calculations (DFT) showed that the effectiveness of the inhibitive actions of the studied compounds correlates well with their electron donating ability, whilst Monte Carlo simulations revealed that the extent and favourability of adsorption of inhibitor molecules on the carbon steel surface establish their corrosion inhibition performances.

The corrosion inhibition of mild steel in a 1.0 M hydrochloric acid solution by 2-(4,5diphenyl- 4,5-dihydro-1h-imidazol-2-yl)-5-methoxyphenol (P1) has been studied in relation to the concentration of the inhibitor, as well as to the temperature, using chemical (weight loss) and electrochemical techniques. All the employed methods were in reasonable agreement. The protection efficiency increased with an increased inhibitor's concentration. The obtained thermodynamic adsorption parameters (ΔG*ads, ΔH*ads, ΔS*ads) indicated that this polymer retarded both cathodic and anodic processes through physical adsorption, and blocked the active corrosion sites. It was also found that this compound obeyed the Langmuir's adsorption isotherm.

New quinoline, namely 5-(ethoxymethyl)-8-quinolinol (M-QN), has been synthesized and characterized by different spectral methods, such as 1H NMR, 13C NMR and IR spectra. Its inhibitive action against the corrosion of carbon steel in 1.0 M hydrochloric acid solution was investigated at different temperatures in the range from 25±2 to 55±2 °C by a series of known techniques, such as weight loss, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The inhibition efficiencies obtained from all employed methods are in good agreement with each other. The obtained results show that M-QN compound is a very good inhibitor with an efficiency of 97.7 % at 10-3 M additive concentration in a 1.0 M HCl solution. The inhibition efficiency increased with an increase of the inhibitor's concentration. Changes in impedance parameters (Rct and Cdl) were indicative of adsorption of the compound (M-QN) on the metal surface, leading to the formation of a protective film. Tafel polarization measurements showed that M-QN inhibitor is of a mixed type. The adsorption of the inhibitor on the surface of carbon steel in a 1.0 M HCl solution was found to obey Langmuir's adsorption isotherm. The kinetic and thermodynamic parameters for carbon steel corrosion and inhibitor adsorption, respectively, were determined and discussed. On the bases of thermodynamic adsorption parameters, comprehensive adsorption (physisorption and chemisorption) for the studied inhibitors on carbon steel surface was suggested.

WOS: 000459072300001, The inhibition efficiency of three substituted phenyltetrazole compounds, namely 5-(4-chlorophenyl)-1H-tetrazole (Cl-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT), and 5-phenyl-1H-tetrazole (PT), for mild steel corrosion in 5.0 M HCl solution was investigated using weight loss measurements and electrochemical study. It is showed that these compounds are good inhibitors for mild steel corrosion in 5.0 M HCl solution which act as cathodic type inhibitors. So, the inhibition efficiency was increased with inhibitor concentration in the order of Cl-PT > MO-PT > PT which depended on their molecular structures. It is found also that these compounds toke its performance at different temperatures range from 298 to 328 K. In addition, the thermodynamic adsorption parameters at different concentrations were investigated and discussed. Finally, it is seen that the inhibition efficiency of the studied compounds increased with immersion time to reach a maximum at 12 h.

Three quinoxalinone derivatives, namely (E)-3-styrylquinoxalin-2(1H)-one (SQ), (E)-3-(4methoxystyryl)quinoxalin-2(1H)-one (MOSQ) and (E)-3-(4-methoxystyry1)-7-methylquinoxalin-2(1H)-one (MOSMQ) were synthesized and characterized. Thus, their inhibition effects on mild steel corrosion in 1.0 M HCl medium were investigated using weight loss method, electrochemical measurements. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 298-328 K. Polarization measurements indicated that, the studied compounds act as a mixed type inhibitors, the inhibition efficiency depends on their concentrations and followed the order MOSQ> MOSMQ> SQ Electrochemical impedance spectroscopy showed that all compounds act by the formation of a protective film at the metallic surface. The adsorption of three inhibitors on steel surface obeyed Langmuir model, thus the thermodynamic and kinetic parameters were calculated and discussed. In the part based on DFF calculations of this study, some electronic properties of studied molecules were calculated and discussed with the help of B3LYP/6-311G (d,p), B3LYP/6-311 ++G (d,p) and B3LYP/6-311G ++ (2d,2p) methods. The theoretical and experimental results are in good agreement. (C) 2016 Elsevier B.V. All rights.reserved., Three quinoxalinone derivatives, namely (E)-3-styrylquinoxalin-2(1H)- one (SQ), (E)-3- (4-methoxystyryl)quinoxalin-2(1H)- one (MOSQ) and (E)-3- (4-methoxystyryl)- 7-methylquinoxalin-2(1H)- one (MOSMQ) were synthesized and characterized. Thus, theirinhibition effects on mild steel corrosion in 1.0 M HCl medium were investigated using weightloss method, electrochemical measurements. The effect of temperature on the corrosionbehavior of mild steel was studied in the range of 298-328 K. Polarization measurementsindicated that, the studied compounds act as a mixed type inhibitors, the inhibition efficiencydepends on their concentrations and followed the order MOSQ > MOSMQ > SQ.Electrochemical impedance spectroscopy showed that all compounds act by the formation of aprotective film at the metallic surface. The adsorption of three inhibitors on steel surfaceobeyed Langmuir model, thus the thermodynamic and kinetic parameters were calculated anddiscussed. In the part based on DFT calculations of this study, some electronic properties ofstudied molecules were calculated and discussed with the help of B3LYP/6-311G (d,p),B3LYP/6-311++G (d,p) and B3LYP/6-311G++ (2d,2p) methods. The theoretical andexperimental results are in good agreement.

International audience; The 2-propargyl-5-o-hydroxyphenyltetrazole (PHPT) has been tested as corrosion inhibitor for low carbon steel in simulated cooling water. The polarization curves showed that PHPT acts as mixed-type inhibitor. Its inhibition efficiency was found to enhance with increase of the inhibitor concentration and immersion time due to the formation of the inhibitor film on the metal surface as indicated by electrochemical impedance spectroscopy measurements. To complete the formulation further, a non oxidizing biocide was added. Its presence with PHPT does not affect its inhibitory performance and it can be served as a basic component of the formulation for cooling water system.

Phenyltetrazole substituted compounds, namely 5-phenyl-1H-tetrazole (PT), 5-(4chlorophenyl)-1H-tetrazole (Cl-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT) and 5-p-tolyl-1H-tetrazole (M-PT) were synthesized to study their inhibition behavior on mild steel in 1 M HCl by weight loss measurement, potentiodynamic polarization studies and electrochemical impedance spectroscopy (EIS). It has been observed that corrosion rate decreases and inhibition efficiency increases with increasing in phenyltetrazole substituted concentration and dependence on molecular structure. Polarization data indicate that these compounds act as very good cathodic inhibitors of mild steel in 1 M HCl. The result showed that the inhibition efficiency decreased with temperature and increased with immersion time. EIS has the same trend of inhibitive effect as that of the polarization data, which indicates the formation of a protective layer on mild steel surface by molecules adsorption .

Electroless Ni-Cu-P alloy coatings were deposited on the ordinary steel substrate in an acidic hypophosphite-type plating bath. These coatings were characterized by a scanning electron microscope (SEM) and an X-ray diffraction. The micrograph shows that coating presents a nodular aspect and is relatively homogeneous and very smooth. The EDX analysis shows that the coating contains 12 wt.% of phosphorus element with a predominance of nickel element. In addition, the anticorrosion properties of the Ni-Cu-P coatings in 1 M HCl, 1 M H2SO4, and 3% NaCl solutions were investigated using Tafel polarization curves, electrochemical impedance spectroscopy, and SEM/EDX analysis. The result showed a marginal improvement in corrosion resistance in 3% NaCl solution compared to acidic medium. It also showed that the corrosion mechanism depends on the nature of the solution.