Inhibition of Aluminium Alloy Corrosion by Thiourea and Lithium Ion in 3.5 % NaCl Solution Using Gravimetric, Adsorption and Theoretical Studies (original) (raw)
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IOSR Journals , 2019
The mechanism of corrosion inhibition of aluminium by 2 M thiourea in 0.08 M potassium hydroxide was investigated using gasometric, gravimetric and scanning electron microscope (SEM) methods. Synergistic measurements were also carried out, The result showed that the rate of hydrogen gas evolution and weight loss was greatly reduced while inhibition efficiency increased. These effects were seen to increase as time prolonged. SEM results showed the vivid presence of the absorbed inhibitor molecules on the surface of the metal protecting it from corrosion attack.
Journal of Electroanalytical Chemistry, 2004
The inhibition of corrosion of iron by thiourea (TU) and its N-substituted derivatives has been investigated using semiempirical molecular orbital theory. The high efficiency of TU with low concentration is attributed to strong adsorption of molecular species through the active center C-S bond. The protonation process appeared to be the effective parameter at high concentration with lowering of the inhibition efficiency of the TU. Alkyl N-substituted TU with the least protonation and with the maximum adsorption is a better inhibitor than TU and aryl N-substituted TU. The thiocarbohydrazide molecule shows the least efficiency of our investigated inhibitors with the highest protonation due to high charge density on the sulphur atom, lengthening and weakening of the C-S bond, and high reactivity with small energy separation between the frontier molecular orbitals.
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Thiamine hydrochloride (vitamin B1) has been tested as a potential inhibitor for aluminium corrosion in 1.0 M hydrochloric acid solution, using mass loss technique and DFT studies. These studies were performed in the concentration range of 0.13 mM to 0.53 mM and the temperature range of 303 K to 323 K. The experimental results show that the inhibition efficiency is concentration and temperature dependent. Experimental data were used to fit adsorption isotherms including Langmuir, El-Awady, Freundlich and Temkin. Though the Langmuir model was the appropriate isotherm, it could not be applied rigorously. Furthermore, the Adejo-Ekwenchi isotherm was used to characterize the type of adsorption. The thermodynamic adsorption and activation functions were determined and analysed. They indicate a spontaneous adsorption process and both physisorption and chemisorption processes. Density functional theory (DFT) calculations were performed and discussed. They reveal good correlations between e...
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.
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.
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.
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%.
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.