Semiempirical investigation of the inhibition efficiency of thiourea derivatives as corrosion inhibitors (original) (raw)
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Journal of Physical & Theoretical Chemistry, 2017
In this paper, quantum chemical parameters at density functional theory (DFT) B3LYP/6-31G** (d,p) level of theory were calculated for three organic corrosion inhibitors [N-benzoyl-N-(p-aminophenyl) thiourea, Nbenzoyl-N-(thiazole) thiourea and N-acetyl-N-(dibenzyl) thiourea. The calculated molecular descriptors such as the HOMO, LUMO, dipole moment, chemical potential (μ), chemical hardness (ղ), global nucleophilicity (ω) and average electronic charges on nitrogen atoms were explained in line with the experimental observed inhibitory efficiency for the compounds. The calculated results revealed that electron density on the rings (Q ring (e)) and thiocarbonyl sulphur atom (S* in C=S) are strongly correlated to the observed %IE. Therefore, electronic interactions such as π-cationic and n-cationic interactions between the molecules and metal surface played prominent roles in adsorption process than electron donor-acceptor model as early reported by Uday et al., 2013 [19].
Pivotal Role of Heteroatoms in Improving the Corrosion Inhibition Ability of Thiourea Derivatives
Diphenyl-2-thiourea (DPTU) and 1-phenyl-3-(2-pyridyl)-2thiourea (PPTU) were selected as the researched subject for investigating the effect of heteroatoms on the low carbon steel corrosion inhibition ability. Results from the potentiodynamic polarization measurements (PPM) indicate that the addition of a nitrogen atom in the benzene ring increases the corrosion inhibition efficiency of PPTU (97.2%), being higher than that of DPTU (93.1%) at the same condition of 2.0 × 10 −4 M at 30°C. The Nyquist diagrams show that increasing the concentrations of both DPTU and PPTU will enhance the charge-transfer resistance and reduce the double-layer capacitance. The obtained data based on PPM and electrochemical impedance spectroscopy methods are in accordance to the analysis based on the scanning electrochemical microscopy images. Besides, results from quantum chemical calculations prove that the heteroatoms in the inhibitor molecules are the adsorption centers, and the benzene rings increase the electrostatic interaction between the inhibitor molecules and the steel surface. Results from Monte Carlo and molecular dynamics simulation have clarified the adsorption mechanism of DPTU and PPTU on the steel surface. Adsorption energies confirm that PPTU displays the higher inhibition ability as compared with DPTU.
Industrial & Engineering Chemistry Research, 2012
1-Benzoyl-3,3-diphenylthiourea (1), 1-benzoyl-3,3-dibenzylthiourea (2), 1-benzoyl-3,3-diethylthiourea (3), 1benzoyl-3,3-dibutylthiourea (4), 1-benzoyl-3,3-bis(2-methylpropyl)thiourea (5), and 1-benzoyl-3,3-bis(propan-2-yl)thiourea (6) were synthesized and investigated as inhibitors for the corrosion of the surface of mild steel in 1.0 M HCl by chemical and electrochemical measurements. The inhibition efficiencies obtained from different methods were in good agreement with each other. Inhibitor 2 showed a higher inhibition efficiency according to all of the methods. The Tafel polarization method revealed the mixed-mode inhibition of inhibitors with predominant control of the anodic reaction. At all studied temperatures, the adsorption of the inhibitor molecules onto the steel surface was found to follow the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption strongly supported spontaneous chemical and/or physical adsorption of inhibitor molecules. The adsorption mechanism for inhibition was supported by ultraviolet−visible (UV−vis), Fourier transform infrared (FTIR), Raman, and scanning electron microscopy−energy-dispersive X-ray (SEM−EDS) spectroscopic methods, and adsorption isotherm measurements. The crystalline/amorphous nature of the inhibitors adsorbed onto the mild steel surface was indicated by wide-angle X-ray diffraction (WAXD) analysis.
Synthesis of Thiourea Derivatives and its Evaluation as Corrosion Inhibitor For Carbon Steel
The inhibitory effect of thiourea-based compounds was evaluated using carbon steel body specimens in hydrochloric acid media. Thiourea derivatives,benzamide and N-(6-methylpyridin-2-ylcarbamothioyl)benzamide, were synthesized using a simple route with good yields of approximately 70%. The inhibitory efficiencies were obtained by means of weight-loss experiments and electrochemical techniques (e.g., polarization curves and electrochemical impedance spectroscopy). The presence of a methyl functional group showed a better inhibitory efficiency compared with the derivate inhibitor without such modification. Analyzing Langmuir isotherms, G 0 ads values indicate the chemical adsorption of thiourea-based compounds. The E Corr values obtained for the thiourea derivative with the methyl functionality was cathodically shifted by approximately −0.08 V, with an inhibition efficiency of 81%.
Corrosion inhibition of thiourea and thiadiazole derivatives : A Review
Journal of Materials and Environmental Science, 2012
The continuous search for better corrosion inhibitors, due to vast differences in the media encountered in industry remains a focal point in corrosion control. The use of organic compounds to inhibit corrosion has assumed great significance due to their application in preventing corrosion under various corrosive environments. These compounds have great potential to inhibit aqueous corrosion due to film formation by adsorption on the metal surface. This paper reviews the inhibitive effect of thiourea and thiadiazole derivatives. This group of organosulphur and heterocyclic compounds and derivatives has important theoretical and practical applications, but their inhibition mechanism is not fully understood, despite extensive study. The effect of these compounds on the corrosion of metallic alloys was evaluated through assessment of various journals and experimental techniques. The corrosion rate was found to be a function of different variables. Due attention was paid to the systematic study of inhibitor action of derivatives with much emphasis on the functional groups of the molecular structure. From the comprehensive discourse presented, it is concluded that the derivatives fulfill the basic requirements for consideration as an efficient corrosion inhibitor.
Three thiosemicarbazides, namely 2-(2-aminophenyl)-N phenylhydrazinecarbothioamide (AP4PT), N,2-diphenylhydrazinecarbothioamide (D4PT) and 2-(2-hydroxyphenyl)-N-phenyl hydrazinecarbothioamide (HP4PT), were investigated as corrosion inhibitors for mild steel in H 2 SO 4 solution using gravimetric and gasometric methods. The results revealed that they all inhibit corrosion and their % inhibition efficiencies (%IE) follow the order: AP4PT > HP4PT > D4PT. The %IE obtained from the gravimetric and gasometric experiments were in good agreement. The thermodynamic parameters obtained support a physical adsorption mechanism and the adsorption followed the Langmuir adsorption isotherm. Some quantum chemical parameters were calculated using different methods and correlated with the experimental %IE. Quantitative structure activity relationship (QSAR) approach was used on a composite index of some quantum chemical parameters to characterize the inhibition performance of the studied molecules. The results showed that the %IE were closely related to some of the quantum chemical parameters, but with varying degrees. The calculated/theoretical %IE of the molecules were found to be close to their experimental %IE. The local reactivity has been studied through the Fukui and condensed softness indices in order to predict both the reactive centers and to know the possible sites of nucleophilic and electrophilic attacks.
Inhibition of mild steel corrosion in acid media by N-benzyl-N'-phenyl thiourea
Indian Journal of Chemical Technology, 2008
The inhibition el'l'ect of N-benzyl-N'-phenyl thiourea (BPTU) on the corrosion of mild steel in 0.01 and 0.05 N HCI medium has been investigated by potentiostatic polarization technique. Results obtained reveal that BPTU is an efficient anodic inhibitor with greater than 94% of efficiency in the range of temperature studied. The adsorption of inhibitor on the mild steel surface obeys the Temkins' adsorption isotherm and the inhibition is governed by chemisorption mechanism. The kinetic parameters of adsorption obtained reveal spontaneous adsorption and a strong interaction of the compound on the mild steel surface. The influences of the parameters like temperature, HCI concentration and inhibitor concentration on the corrosion of mild steel has also been investigated.
2014
A series of decanoyl thiourea derivatives, namely N-decanoyl-N’-2-pyridinethiourea (D1), N-decanoyl-N’-3-pyridinethiourea (D2) and N-decanoyl-N’-4-pyridinethiourea (D3) were successfully synthesized and were applied as corrosion inhibitors. The compounds were characterized via elemental analyser, Fourier Transform Infra Red (FTIR) and H and C Nuclear Magnetic Resonance (NMR) spectroscopies. The inhibition efficiency of each compound was studied on the corrosion of mild steel in 0.1 M H2SO4 with different concentrations of the compounds by using weight loss method and linear polarization resistance technique. From both techniques the results indicate that the corrosion process was significantly reduced with the presence of such compounds. It shows that compound D3 has the highest efficiency which is 85.84% compared to D1 and D2. The effects of position of N atom located at ortho, meta and para in chemical structure of pyridine on the corrosion inhibition efficiencies of the compounds...
ENHANCEMENT OF CORROSION INHIBITION ACTION OF THIOUREA BY AROMATIC AMINES
Industrialization and modernization has made a strong demand of steel and their maintenance for a strong infrastructure for every country in the race of survival, stabilization, growth and competition. Atmospheric corrosion may cause some dangerous and expensive damage to everything from automobiles, home appliances, water systems to pipelines, bridges and public buildings like other natural hazards such as earthquakes or several weather disturbances. Atmospheric corrosion can aggressively accelerate the rate of degradation of steel during their manufacturing, processing, storage and transportation. In these cases, traditional methods to prevent corrosion are not suitable which provide scope of vapour phase corrosion inhibitors in industries, defense and daily life. Synergistic effect of Thiourea was tested for mild steel in different aggressive atmospheric conditions with aromatic amines (N-Ethylaniline, 1-Benzylimidazole and 5-Aminotetrazole) by Vapour pressure determination test, Weight loss test, Salt spray test, Sulphur dioxide test, Metallurgical research microcopy and Scanning electron microcopy at 500C. Keywords: Synergistic effect, Salt spray test, Vapour phase corrosion inhibitor, Weight loss test, Sulphurdioxide test, Aromatic amine.