Selected oxadiazoles of fatty acids; namely 2-hepta decene-5-mercapto-1-oxa-3,4-diazole (HMOD); 2-undecane-5-mercapto-1-oxa-3,4-diazole
(UMOD); and 2-decene-5-mercapto-1-oxa-3,4-diazole (DMOD), were synthesized. Their influence on the inhibition of corrosion
of mild steel in 20% formic acid (HCOOH) was investigated by weight loss and potentiodynamic polarization techniques. The
inhibition efficiency of the compounds was found to vary with concentration, immersion time and temperature. All the compounds
showed good inhibition efficiency (eIE) in formic acid solution. Adsorption on mild steel obeyed the Langmuir adsorption isotherm. Potentiodynamic polarization
revealed that all three inhibitors, HMOD, UMOD, and DMOD are mixed inhibitors. Electrochemical impedance spectroscopy was
also used to investigate the inhibition mechanism. 相似文献
2-(N,N-dimethylamino) benzylidene imino-4-(4-methyl phenyl)-1,3-thiazole (DIMPT), 2-benzylidene imino-4-(4-methyl phenyl)-1,3-thiazole (BIMPT), 2-salicylidene imino-4-(4-methyl phenyl)-1,3-thiazole (SIMPT) and 2-cinnamylidene imino-4-(4-methyl phenyl)-1,3-thiazole (CIMPT) were synthesized in the laboratory and their influence on the inhibition of corrosion of mild steel in 20 formic acid and 20 acetic acid was investigated by weight loss and potentiodynamic polarization techniques. The inhibition efficiency of these compounds was found to vary with their nature and concentration, temperature, immersion time and acid concentration. The values of activation energy and free energy of adsorption of the thiazoles were calculated to investigate the mechanism of corrosion inhibition. The adsorption of all the thiazoles on mild steel surface was found to obey Langmuir adsorption isotherm. The potentiodynamic polarization result revealed that the compounds studied are mixed type inhibitors. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. 相似文献
Two triazole derivatives, 3,4-dichloro-acetophenone-O-1′-(1′,3′,4′-triazolyl)-methaneoxime (4-DTM) and 2,5-dichloro-acetophenone-O-1′-(1′,3′,4′-triazolyl)-methaneoxime (5-DTM) were synthesized, and the inhibition effects for mild steel in 1 M HCl solutions
were investigated by weight loss measurements, electrochemical tests and scanning electronic microscopy (SEM). The weight
loss measurements showed that these compounds have excellent inhibiting effect at a concentration of 1.0 × 10−3 M. The potentiodynamic polarization experiment revealed that the triazole derivatives are inhibitors of mixed-type and electrochemical
impedance spectroscopy (EIS) confirmed that changes in the impedance parameters (Rct and Cdl) are due to surface adsorption. The inhibition efficiencies obtained from weight loss measurements and electrochemical tests
were in good agreement. Adsorption followed the Langmuir isotherm with negative values of the free energy of adsorption
. The thermodynamic parameters of adsorption were determined and are discussed. Results show that both 4-DTM and 5-DTM are
good inhibitors for mild steel in acid media. 相似文献
The corrosion resistance of mild steel in 1 M H2SO4 solution was evaluated after addition of Sn2+ and Zn2+, N-acetylcystein (ACC) and S-benzylcystein (BzC) as a function of concentration (5–1000 μM) and solution temperature (35–50°C). Eight blends were also
investigated. Both polarization resistance (Rp) and electrochemical impedance spectroscopy (EIS) were employed. For single additives, Zn2+ ions acted as accelerator for mild steel corrosion while the other additives showed good performance. The most effective
additive was Sn2+. Adsorption of Sn2+, ACC and BzC obeyed the Temkin adsorption isotherm and had a very high negative value of free energy of adsorption (−ΔG°ads). All blends provided good inhibition which increased with rise in temperature. Corrosion kinetic parameters such as activation
energy (Ea) and the pre-exponential factor (λ) were calculated and discussed. EIS revealed that the interface of the uninhibited and
inhibited systems can be represented by the simple equivalent circuit Re(RctQdl). 相似文献
Selected hydrazides and thiosemicarbazides of fatty acids with 11, 12, and 18 carbon atoms were synthesized and evaluated as corrosion inhibitors on mild steel and oil-well steel (N-80) in boiling 15% hydrochloric acid solution, by weight loss method. Potentiodynamic polarization studies carried out on mild steel and N-80 steel at room temperature showed that all the tested compounds are of mixed type. Adsorption studies showed that all the investigated compounds followed Temkin's adsorption isotherm. 相似文献
3,5-Diamino-1,2,4-triazole Schiff base derivatives and their inhibition efficiency, based on the effect of changing functional
groups, were reported to establish a relationship between inhibitor efficiency and molecular structure using weight loss method,
electrochemical and Fourier transform infrared spectral techniques. It was found that the molecules containing more electron
donating groups have higher inhibition efficiency than the corresponding compounds with low electron donating groups. The
results indicate that the order of inhibition efficiency of the triazole and its Schiff bases in solution and the extent of
their tendency to adsorb on mild steel surfaces are as follows: vanilidine 3,5-diamino-1,2,4-triazole > furfuraldine 3,5-diamino-1,2,4-triazole > anisalidine
3,5-diamino-1,2,4-triazole > 3,5-diamino-1,2,4-triazole. 相似文献
The inhibitive effect of four oleo chemicals (namely; 2-Pentadecyl-1,3-imidazoline (PDI), 2-Undecyl-1,3-imidazoline (UDI),
2-Heptadecyl-1,3-imidazoline (HDI), 2-Nonyl-1,3-imidazoline (NI)), regarded as green inhibitors, were studied for the corrosion
protection of mild steel in 0.5 M H2SO4. The methods employed were weight loss, potentiodynamic polarization and electrochemical impedance techniques. Scanning electron
microscopy (SEM) was carried out on the inhibited and uninhibited metal samples to characterize the surface. The purity of
synthesized inhibitors was checked by FT-IR and NMR studies. The inhibition efficiency increased with increase in inhibitor
concentration, immersion time and decreased with increase in solution temperature. No significant change in IE values was
observed with increase in acid concentration. The best performance was obtained for UDI possessing 96.2% inhibition efficiency
at 500 ppm concentration. The adsorption of the compounds on the mild steel surface in the presence of sulfuric acid obeyed
Langmuir’s adsorption isotherm. The values obtained for free energy of adsorption and heats of adsorption suggest physical
adsorption. The addition of inhibitor decreased the entropy of activation suggesting that the inhibitors are more orderly
arranged along the mild steel surface. The potentiodynamic polarization data indicate mixed control. The electrochemical impedance
study further confirms the formation of a protective layer on the mild steel surface through the inhibitor adsorption. 相似文献
The corrosion inhibition behaviour of some substituted dithiobiurets, namely, -1,5-diphenyl-2,4-dithiobiuret (DPDTB), 1-tolyl-5-phenyl-2,4-dithiobiuret (TPDTB), 1-anisidyl-5-phenyl-2,4-dithiobiuret (APDTB), 1-chorophenyl-5-diphenyl-2,4-dithiobiuret (CPDTB) were studied in 1 to 5 M HCl on mild steel. The characteristics of these compounds are explained in terms of factors such as inhibitor concentration, acid concentration, temperature, immersion time and molecular structure. Potentiodynamic polarization and a.c. impedance techniques were used to investigate the inhibition mechanism. Among the compounds studied APDTB exhibited the best performance giving more than 98% inhibition efficiency (IE) in HCl solutions. DPDTB and CPDTB were found to reduce hydrogen permeation through mild steel in HCl solutions. The adsorption of APDTB was also confirmed by Auger electron spectroscopy (AES). 相似文献
The purines and its derivatives, such as, guanine, adenine, 2,6-diaminopurine, 6-thioguanine and 2,6-dithiopurine, were investigated as corrosion inhibitors for mild steel in 1 M HCl solution by weight loss measurements, electrochemical tests and quantum chemical calculations. The polarization curves of mild steel in the hydrochloric acid solutions of the purines showed that both cathodic and anodic processes of steel corrosion were suppressed. The Nyquist plots of impedance expressed mainly as a depressed capacitive loop with different compounds and concentrations. For all these purines, the inhibition efficiency increased by increasing the inhibitor concentration, and the inhibition efficiency orders are 2,6-dithiopurine > 6-thioguanine > 2,6-diaminopurine > adenine > guanine with the highest inhibiting efficiency of 88.0% for 10−3 M 2,6-dithiopurine.The optimized structures of purines, the Mulliken charges, molecular orbital densities and relevant parameters were calculated by quantum chemical calculations. The quantum chemical calculation results inferred that the adsorption belong to physical adsorption, which might arise from the π stacking between the π electron of the purines and the metal surface. 相似文献
The Chromene derivatives having heteroatoms as active sites were investigated for scaling downthe corrosion process in mild steel (MS). The effectiveness of the inhibitors was monitored by gravimetric potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. Observations suggested that the mechanism of inhibition is mainly due to the adsorption of the inhibitor molecules on the MS surface. Adsorption of both inhibitors follows the Langmuir adsorption isotherm. Tafel curve shows that both inhibitors act as mixed type inhibitor. Morphological studies were done by FESEM and AFM instruments. These images indicated the formation of a protective layer on the MS surface which slows down the process of corrosion. DFT calculation provides the valuable quantum chemical parameters for both inhibitors which are supportive of the results obtained from gravimetric and EIS methods. 相似文献
Three fatty acid triazoles, namely, 3-undecane-4-aryl-5-mercapto-1,2,4-triazole (triazole 1), 3(heptadeca-8-ene)-4-aryl-5-mercapto-1,2,4-triazole
(triazole 2), and 3(deca-9-ene)-4-aryl-5-mercapto-1,2-4-triazole (triazole 3) were synthesized and their corrosion-inhibiting
action in 15% hydrochloric acid was evaluated by weight-loss method and electrochemical techniques. Electrochemical polarization
studies at room temperature indicated that all the triazoles are mixed-type inhibitors, i.e., they inhibit both anodic and
cathodic reactions. The adsorption of these compounds onto mild steel from 15% HCl followed Temkin's adsorption isotherm. 相似文献
To diminish corrosion which leads to structural damages and to implement a green mitigator has induced the usage of aminothiazolyl coumarin derivatives to study mild steel (MS) corrosion using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), weight loss, atomic force microscopy (AFM), and electron microscopy with energy dispersive spectroscopy (SEM–EDS) spectrometry in acid medium. The results showed that the inhibition efficiency was 90.8% for the least effective inhibitor and 97.1% for the most effective inhibitor at optimal concentration (10 mM). Enhancement of inhibition efficiency in weight loss method and increase in Rp values in impedance and mixed nature of the inhibition in polarization measurement reveals the best inhibition capacity of coumarins over the MS. The coumarins were characterized using FT-IR, NMR and Mass spectroscopy. The adsorption was well fitted with the Langmuir adsorption isotherm model. SEM–EDS and AFM images confirmed the shielding effect of coumarin derivatives through a layer formation on MS against acid medium. The adsorption mechanism of aminothiazolyl coumarin derivatives was further explored by quantum chemical calculations (DFT) and molecular dynamics (MD).
Three triazole derivatives (4-chloro-acetophenone-O-1′-(1′,3′,4′-triazolyl)-metheneoxime (CATM), 4-methoxyl-acetophenone-O-1′-(1′,3′,4′-triazolyl)-metheneoxime (MATM) and 4-fluoro-acetophenone-O-1′-(1′,3′,4′-triazolyl)-metheneoxime (FATM)) have been synthesized as new inhibitors for the corrosion of mild steel in acid media. The inhibition efficiencies of these inhibitors were evaluated by means of weight loss and electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and polarization curves. Then the surface morphology was studied by scanning electron microscopy (SEM). The adsorption of triazole derivatives is found to obey Langmuir adsorption isotherm, and the thermodynamic parameters were determined and discussed. The relationship between molecular structure of these compounds and their inhibition efficiency has been investigated by ab initio quantum chemical calculations. The electronic properties such as the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energy levels, energy gap (LUMO-HOMO), dipole moment and molecular orbital densities were computed. 相似文献
Inhibition effect of three bis-Schiff bases of isatin namely (2-methoxybenzylidene) hydrazono) indolin-2-one (HZ-1), (2-hydroxybenzylidene) hydrazono) indolin-2-one (HZ-2) and (4-nitrobenzylidene) hydrazono) indolin-2-one (HZ-3) was studied on mild steel corrosion in 1.0 M HCl by gravimetric measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and quantum chemical study. The values of activation energy (Ea), equilibrium constant (Kads), free energy of adsorption ΔG°ads, activation enthalpy ΔH* and activation entropy ΔS*were discussed. The adsorption of inhibitors on metal followed Langmuir's adsorption isotherm. SEM and EDX observations confirmed the existence of protective inhibitor film on metal surface. Quantum chemical study supports the comparative inhibition effect of HZs. 相似文献