The inhibition effect of 3-(4-Hydroxyphenylamino) propanenitrile (Para) and 3-(2-Hydroxyphenylamino) propanenitrile (ortho) on the corrosion of steel mild 1M HCl solution was studied by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy methods. The results revealed that corrosion rate depends on the molecular structure and the concentration of inhibitors. We found that the Para Hydroxyphenylamino propanenitrile is a good inhibitor and has been tested with efficiency reaches to 85% in 10- 3M. Polarization studies through electrochemical curves and spectroscopy of electrochemical impedance clearly show that 3-(4-Hydroxyphenylamino) propanenitrile is a mixed inhibitor. The adsorption of Ortho and Para inhibitors on the mild steel surface obeys Langmuir isotherm. Both thermodynamic parameters (adsorption heat ΔH°, adsorption free energy ΔG° and adsorption entropy ΔS°) and kinetic parameters (apparent activation energy Ea) were calculated and discussed. The quantum chemical parameters calculated using DFT at the B3LYP/6-31G* level of theory show a good correlation to the inhibition efficiency. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the separation energy (ΔE) and the dipole moment (μ) from the inhibitor to the metal surface explain well experimental data.

Inhibitory effect of some new synthesized and analyzed aminocyclohexane compounds, namely, 3-cyclohexylaminopropionitrile (P1) and aminocyclohexane (P2) respectively; on corrosion of steel in 1M HCl solution has been studied using weight loss measurements and electrochemical technique polarization methods. The results obtained reveal that these compounds are efficient inhibitors. The inhibition efficiency increases with the increase of inhibitor concentration and reaches 90 % for P1 at 10-3 M. Potentiodynamic polarisation studies clearly reveal that P1 and P2 acts cathodic inhibitors without change of the mechanism of hydrogen evolution. The temperature effect on the corrosion behaviour of iron in 1 M HCl without and with the inhibitors at 10-3 M was studied in the temperature range from 313 to 353 K. Significant correlations are obtained between inhibition efficiency with the calculated chemical indexes, indicating that variation of inhibition with structure of the inhibitor may be explained in terms of electronic properties. The inhibitors were adsorbed on the iron surface according to the Langmuir adsorption isotherm model at different temperature. From the adsorption isotherm some thermodynamic data for the adsorption process (K and DG°ads) are calculated and discussed.

The inhibition effect of a new imidazolpyridine derivative namely 2,6-bis(2,5-dimethyl-2H-imidazol-4-yl)pyridine (BDIP) on corrosion of mild steel in 1 M HCl was studied at 308 K. Weight-loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods were used. Results showed that BDIP was a good inhibitor and its inhibiting efficiency reaches 97,4% at 10− 3 M. The values of the inhibition efficiency calculated from these techniques are reasonably in good agreement. Polarisation curves revealed that this organic compound acted predominately as a cathodic inhibitor. EIS measurements showed that the charge transfer resistance increases with the inhibitor concentration. The temperature effect on the corrosion behaviour of mild steel in 1 M HCl with and without BDIP at 10− 3 M was studied in the temperature range 308–353 K. The associated activation energy was determined. The adsorption of BDIP on the mild steel surface obeyed to the Langmuir's adsorption isotherm model.

We have studied the oxidation of catechol to o-quinone with atmospheric dioxygen at ambient conditions by in situ generated copper (II) complexes of five electron-rich nitrogen ligands: (3,5-dimethyl-pyrazol-1-yl)-methanol L1; 3-benzylamino-propionitrile L2; 3-[benzyl-(3,5-dimethyl-pyrazol-1-ylmethyl)-amino]-propionitrile L3; {3-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L4 and 3-[{2-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-ethyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L5. We found that all complexes catalyze the oxidation reaction with different rates depending on three parameters: the nature of the ligand, the nature of ion salts, and the concentration of the complex. The combination of L3(CuSO4) gave the highest rate of this activity about 8.71 μmol1/L1/min1.

The inhibition of the corrosion of mild steel 1 M HCl solution by some diamine compounds has been investigated in relation to the concentration of the inhibitor as well as the temperature using weight loss and electrochemical measurements. The effect of the temperature on the corrosion behavior with the addition of different concentrations of new diamine compounds (3-[2-(2-cyano-ethylamino)-methylamino]-propionitrile (P1); 3-[2-(2-cyano-ethylamino)-ethylamino]-propionitrile (P2), and 3-[6-(2-cyano-ethylamino)-hexylamino]-propionitrile (P3), respectively, was studied in the temperature range 40–80 °C. Polarization curves reveal that (P1, P2, and P3) are mixed type inhibitors. The inhibition efficiency of organic compounds is temperature independent, but increases with the inhibitor concentration. Adsorption of inhibitor on the carbon steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined. On the other hand, and in order to determine the relationship between the molecular structure of these compounds and inhibition efficiency, quantum chemical parameters were calculated. The theoretically obtained results were found to be consistent with the experimental data.

New diamine derivatives, namely 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]ethanol (DAME) and 2-[{2-[bis-(2-hydroxyethyl)amino]ethyl}(2-hydroxyethyl)amino]propanol (DAMP) were synthesised and their inhibitive action against the corrosion of mild steel in 1M HCl solution were investigated at 308K. The detailed study of DAME is given using gravimetric measurements and polarization curves method. Results show that DAME is a good inhibitor and inhibition efficiency reaches 91.7% at 10−3M. Tafel polarization study revealed that DAME acts as a mixed-type inhibitor. The inhibitor adsorption process in mild steel/DAME/hydrochloric acid system was studied at different temperatures (308–353K) by means of weight loss measurements. The adsorption of DAME on steel surface obeyed Langmuir’s adsorption isotherm. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor adsorption, respectively, were determined and discussed. The comparative study of inhibitive performance of the two diamine derivatives revealed that DAME is more effective than DAMP. Quantitative Structure–Activity Relationship (QSAR) approach has been conducted in attempt to correlate the corrosion inhibition properties of these diamine derivatives with their calculated quantum chemical parameters.

The inhibition behaviour of a phosphite compound: NaMg(H2PO3)(3). H2O (abbr. PhMg) on C38 steel in 1 M HCl solutions was investigated at 25 degrees C using electrochemical and weight loss methods. The results indicated that the title compound inhibited the corrosion of steel and the extent of inhibition increased with its concentrations. A mixed-inhibition mechanism is proposed for the inhibitive effect of PhMg. Effect of temperature is investigated in the (313-353 K) range. The determination of activation and adsorption parameters indicated that the inhibition action in the presence of PhMg is due to physical adsorption.

PurposeThe purpose of this paper is to investigate the inhibitive effect of the phosphite NaCo(H2PO3)3•H2O (PhCo) for the corrosion of mild steel in HCl solutions. The study is another trial to find a mineral inhibitor for mild steel corrosion.Design/methodology/approachThe inhibitory effect has been evaluated by gravimetric and polarisation techniques at various temperatures. The type of adsorption inhibition and adsorption and kinetic data are determined.FindingsResults show that PhCo inhibits the corrosion of steel in acidic solution. The inhibition efficiency at 308 K increases with the inhibitor concentration to reach 96 per cent for 10−4 M, and then decreases at higher temperatures. Kinetic parameters such as Ea, ΔHa ∘ and ΔSa ∘ were calculated. The adsorption of inhibitor obeys the Langmuir isotherm model. Thermodynamic parameters of adsorption including ΔGad, ΔHad, ΔSad, and Keq(ad) were calculated in the presence of inhibitor.Research limitations/implicationsElectrochemical studies (polarization method) show the partial action of inhibitor on anodic and cathodic reactions of the corrosion inhibition.Practical implicationsThe efficiency of the tested phosphite increases with its concentration to reach 96 per cent. It can be used in chemical cleaning and pickling processes at moderate temperature.Originality/valueThis paper reveals the possible application of phosphites as environmentally valid inhibitors for corrosion under the specified conditions.

Some diamine compounds have been tested as corrosion inhibitors on steel in 1 M hydrochloric acid. The study is carried out using weight loss measurements. Results obtained show that the inhibition efficiency ( E %) increases with concentration. The effect of carbon chain length between the two amino groups shows that the efficiency increases with the number of -CH2. A correlation between quantum energies and efficiency is obtained. Adsorption of inhibitors on the mild steel surface in 1 M HCl follows the Langmuir isotherm model.

The effect of 1-{[benzyl-(2-cyano-ethyl)-amino]-methyl}-5-methyl-1H-pyrazole-3carboxylic acid methyl ester (P1) and 1-{[benzyl-(2-cyano-ethyl)-amino]-methyl}-5methyl-1H-pyrazole-3-carboxylic acid ethyl ester (P2) was evaluated as corrosion inhibitors of steel in molar hydrochloric using weight loss measurements and electrochemical polarisation. The results obtained reveal that those compounds reduce the corrosion rate. The inhibiting action increases with the concentration of pyrazole compounds to attain 98.5 % at the 10 -3 M of (P2). The increase in temperature leads to a decrease in the inhibition efficiency of the compounds in the temperature range 308 353 K. The adsorption isotherm of inhibitors on the steel has been determined. The thermodynamic data of activation and adsorption are determined.

The products of aza-type Michael addition, i.e., β-amino carbonyl compounds and their derivatives, are often used as peptide analogs or precursors of optically active amino acids, amino alcohols, diamines, and lactams [1].[...]

The products of aza-type Michael addition, i.e., β-amino carbonyl compounds and their derivatives, are often used as peptide analogs or precursors of optically active amino acids, amino alcohols, diamines, and lactams [1].[...]

The products of aza-type Michael addition, i.e., β-amino carbonyl compounds and their derivatives, are often used as peptide analogs or precursors of optically active amino acids, amino alcohols, diamines, and lactams [1].[...]