Search

PurposeThe purpose of this paper is to investigate three Arylfuranylnicotinamidine derivatives against corrosion of carbon steel (C-steel) in 1.0 M HCl by chemical and electrochemical means. The inhibition efficiency (%IE) increases with increasing the dose of inhibitors. The tested compounds exhibited improved performance at elevated temperature, with %IEreaching 93 percent at 21 µM. Tafel polarization method revealed that the tested compounds act as mixed-type inhibitors. The inhibition action was rationalized due to chemical adsorption of inhibition molecules on C-steel surface following Temkin’s isotherm. Surface examination was carried out by AFM and FTIR techniques. Further, theoretical chemical approaches were used to corroborate the experimental findings.Design/methodology/approachExperimental and computational methods were applied to investigate the efficiency of these new compounds. These studies are complemented with spectral studies and surface morphological scan by AFM. The theoretical results indicate good correlation with experimental findings.FindingsThe tested derivatives are promising corrosion inhibitors for C-steel in the acid environment. The molecular scaffold of this class of compounds can be used to design new highly efficient inhibitors by screening its activity by modeling studies.Originality/valueThe studied compounds are safe inhibitors and greatly adsorbed on Fe surface. The action of compounds is enhanced with temperature, which means these compounds can be used in higher temperature systems. The new compounds are effective at very low concentration.

Corrosion of carbon steel is a major problem that destroys assists of industries and world steel installations; the importance of this work is to introduce new heterocyclic compounds as effective and low-cost corrosion inhibitors. Three compounds of carbohydrazide derivatives, namely: 5-amino-N′-((2-methoxynaphthalen-1-yl)methylene)isoxazole-4-carbohydrazide (H4), 2,4-diamino-N′-((2-methoxy-naphthalene-1-yl)methylene) pyrimidine-5-carbohydrazide (H5) and N′-((2-methoxynaphthalen-1-yl)methylene)-7,7-dimethyl-2,5-dioxo-4a,5,6,7,8,8a-hexahydro-2H-chromene-3-carbohydrazide (H6) were used to examine the efficacy of corrosion of carbon steel in 1 M hydrochloric acid solution. This corrosion efficacy was detected by utilizing various methods including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), weight loss measurements (WL), surface morphology analyses by atomic force microscopy (AFM), quantum chemical computations based on density functional theory (DFT) and molecular dynamics (MD) simulation. The results indicated that these compounds act as mixed type inhibitors i.e. reduce the corrosion rate of carbon steel due to the formation of a stable protective film on the metal surface and reduce the cathodic hydrogen evolution reaction. As confirmed from impedance, carbohydrazide derivatives molecules are adsorbed physically on metal surface with higher corrosion efficacy reached to (81.5–95.2%) at 20 × 10−6 M concentration at room temperature. Temkin isotherm model is the most acceptable one to describe the carbohydrazide derivative molecules adsorption on the surface of carbon steel. Protection mechanism was supported by quantum chemical analyses and Monte Carlo modeling techniques. The theoretical calculations support the experimental results obtained. This proves the use of carbohydrazide derivatives as a very effective inhibitors against the corrosion of carbon steel in acidic media.

2-((2-Aminophenyl)thio)-4,6-dimethylnicotinonitrile (APTDN) and 4,6-dimethyl-2-(phenylamino) nicotinonitrile (DPAN) as new organic derivatives were investigated as corrosion inhibitors for C-steel in 1 M HCl at various temperatures (25–45 °C) using chemical and electrochemical methods. The adsorption of inhibitors on the C-steel surface fits to Langmuir adsorption isotherm and polarization curves showed that APTDN and DPAN are mixed corrosion inhibitors. The topography maps of atomic force microscopy, X-ray photoelectron spectroscopy, and Attenuated total refraction infrared were performed for examination of C-steel surface. Moreover, quantum chemical calculations using Density functional theory were carried out to correlate between theoretical and experimental data.

A new cationic surfactant named (N-(3-(dimethyl hexadecyl ammonio)propyl) palmitamide bromide has been evaluated as corrosion inhibitor for API N80 Steel Pipelines in 1M HCl solution. Four different techniques have been utilized for studying the corrosion behavior of the synthesized cationic amphipathic corrosion inhibitor. The prepared corrosion inhibitor was evaluated at five different temperatures 25, 30, 40, 50 and 60 °C, using weight loss technique. The three other techniques which are potentiodynamic polarization, Electrochemical impedance (EIS) and Electrochemical frequency modulation (EFM) were used for evaluation at room temperature (25 °C ± 1). The results outlined that the synthesized DMHPP amphipathic corrosion inhibitor was good inhibitor and their inhibition efficiencies were directly proportional with both the inhibitor concentration and temperature. Polarization curve revealed that the studied inhibitor act as a mixed-type of inhibitor. The adsorption of the used inhibitor led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. The adsorption behavior of the amphipathic inhibitor obey Langmuir adsorption model. The change in free energy of adsorption of the synthesized inhibitor range from −40.5 to −45.5 kJ mol−1 as an indication for chemisorption process between inhibitor and steel. A clear correlation was found between corrosion inhibition efficiency and theoretical parameters obtained using density functional theory (DFT). Keywords: Steel, Cationic surfactant, Potentiodynamic polarization, EIS, EFM, Quantum chemical calculation

Corrosion inhibition of a novel cationic surfactant namely, N-(2-(2-hydroxyethoxy)ethyl)-N,N-dimethyldodecan-1-aminium bromide (HEDDB) was evaluated as a corrosion inhibitor for carbon steel in 1.0 M HCl by electrochemical frequency modulation (EFM), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. Results of Tafel polarization exhibit that the synthesized surfactant HEDDB behaves as mixed-type inhibitor. The effectiveness of temperature on the corrosion rate which evaluated by chemical technique (weight loss) was investigated and assessed. Langmuir’s adsorption isotherm was the preferable fitted isotherm. The results of weight loss clarified that the efficiency of the synthesized surfactant increases with raising both the concentration of the surfactant and the temperature. HEDDB effectiveness on the morphology of metal surface was monitored by Atomic Force Microscopy (AFM) and Scanning Electron Microscope (SEM) techniques. Quantum chemical technique has been employed to discuss the inhibition efficiency by effectiveness of molecular structure of the synthesized inhibitor. The various techniques which used in this research have inhibition efficiency (IE) with the same direction. Keywords: Carbon steel, Cationic surfactant, HCl, HEDDB, Potentiodynamic polarization, EIS, EFM, SEM, AFM

We reported here, the corrosion inhibition of carbon steel (CS) in H2SO4 media by Ficus carica leaves extract as green sustainable inhibitor. This study was investigated using mass loss method (ML), potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM) and electrochemical impedance spectroscopy (EIS). As well as the metal surface morphology was analyzed by Atomic Force Microscopy (AFM). In addition, the chemical characterization of green inhibitor is carried out by Fourier Transform Infrared (FTIR). EIS revealed that the Ficus carica extract formed a thin protective film on the metal surface and by using of 300 ​ppm of extract of Ficus carica allow reaches (92.7%) of corrosion inhibition efficiency (CIE). The PDP curves revealed that the Ficus carica extract act as a mixed-type inhibitor. It was demonstrated that %IE enhanced with rising the Ficus carica extract doses also increased with arises in temperature (95.7%). Kinetic parameters and thermodynamic adsorption of the system have also been measured and studied. The data obtained revealed that the adsorption of Ficus carica on metal surface followed the Temkin isotherm and according to the activation energy (Ea∗) the Ficus carica extract acts by chemisorption process. The results from unlike measurements were in a well accord.

Three nonionic surfactants based on azodye and Schiff base condensed with poly ethylene glycol were prepared. Their inhibition effect towards corrosion of steel in hydrochloric acid was investigated using electrochemical frequency modulation, electrochemical impedance spectroscopy, potentiodynamic polarization, quantum chemical calculations and molecular dynamic simulation. The data revealed that the prepared surfactants had the ability to inhibit corrosion reaction with good agreement between experimental and computational results. The adsorption of surfactants on the carbon steel surface in 1 M HCl was found to obey Langmuir isotherm. Polarization results showed that these inhibitors act as mixed-type inhibitors.

An expired pharmaceutical product, Carvedilol, was studied as save drug to prevent carbon steel (CS) corrosion in acidic environments by using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The inhibition efficiency increased with increasing drug dose and decreased with increasing temperature, reaching a maximum value of 98.94% at 25°C and 1.6 × 10−4 M. Polarization data showed that the drug is of a mixed type. The inhibition of CS corrosion by Carvedilol can be attributed to the adsorption ability of drug molecules onto the reactive sites of the metal surface. The adsorption process follows the Langmuir isotherm via physical adsorption. The surface morphologies of CS were examined by atomic force spectroscopy (AFM). The results obtained from different techniques are in good agreement.

Faint green crystals of the metal organic framework (MOF) [Cd(SCN)2(6-mquin)2], 1, was obtained by the reaction of CdSO4.5H2O with 6-methylequinoline (6-mquin) in the presence of KSCN. 3Dnetwork structure was created via H-bonds and π–π stacking interactions. The structure of the MOF 1 was characterized by IR, 1H-NMR, UV-visible, TGA, and X-ray single crystal analysis. The structure of the MOF 1 consists of cyclic (CdSCN)n building blocks exhibiting chair conformation creating 1D-chain decorated by the coordinated 6-mquin on both sides. The 1D zig-zagchain is bonded to another chain by hydrogen bonds organizing these chains into a 2D layer. Furthermore, the 2D layers are interacted each other feathering three-3D metal organic framework containing cavities through face-to-face π···π interactions. The MOF 1 was tested as corrosion inhibitor for copper in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance (EIS) techniques. Adsorption of the MOF 1 obeyed Langmuir adsorption isotherm. Effect of temperature on the corrosion process was studied and the activation parameters were calculated and discussed. The results obtained from the two different electrochemical techniques are in a good agreement.

Bichalcophene series namely 4-(2,2′-bithiophene-5-yl) benzamidine (MA-0944) and 6-(2,2′-bithiophene-5-yl) nicotinamidine (MA-0949) were evaluated as corrosion inhibitors for carbon steel (CS) in 1 M HCl using nonelectrochemical and electrochemical techniques. The results revealed that the tested compounds are efficient corrosion inhibitors and their inhibition percentage (η %) reached 98.3% at 18 × 10 − 6 M. The tested compounds are classified as mixed-type inhibitors. The adsorption of the investigated compounds corresponds to Langmuir adsorption isotherm. The surface morphology of the CS surface was analyzed using Attenuated Total Reflectance-infrared spectra (ATR-IR), and Atomic Force Microscopy (AFM). The inhibition property was further elucidated by theoretical approaches; quantum chemical calculation, Natural Bonding Orbital (NBO) analysis, Molecular Dynamic Simulation and Radial Distribution Function (RDF). The theoretical data support the experimental results.

The adsorption and the inhibitive properties of methanol extract of Euphorbia heterophylla on copper in 0.5 M HNO3 have been studied by weight loss method at different temperatures (30-50°C), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Also, the surface morphology was analyzed by scanning electron microscopy (SEM). It was found that the inhibition efficiency increases with increasing extract doses and decreased with increasing temperature. The polarization data revealed that this extract acts as mixed type inhibitor. The adsorption process was more favored at lower temperatures with larger negative standard free energy. The extract was adsorbed physically on the copper surface followed Frumkin isotherm.

The corrosion inhibition behavior in the presence of some surfactants in 1 M HCl medium was examined by mass loss, AC impedance spectroscopy (EIS), potentiodynamic polarization, electrochemical frequency modulation, and surface (scanning electron microscopy, atomic force microscopy) techniques. The C-steel protection rates increased with the increasing amount of surfactant to the 1 M H system and decreases with the increasing temperature of 1 M HCl solution. The adsorption of surfactants on the C-steel surface in HCl follows the Langmuir adsorption mechanism. Arrhenius and transition state equations were applied for the determination of activation parameters. Tafel curves reflect the mixed inhibition behavior of surfactants on the electrode surface in 1 M HCl system. Electrochemical impedance spectroscopy (EIS) method indicates that the C-steel dissolution in HCl environment was fully hindered by charge-transfer processes.

Hydroxy-ethoxy N-(2-(2-hydroxyethoxy)ethyl)-N,N-dimethyloctan-1-aminium bromide (HEDOB) cationic surfactant had been prepared and investigated as a steel protector against its corrosion in 1.0 M HCl. Different techniques such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, electrochemical frequency modulation (EFM) and weight loss techniques were conducted for investigating the corrosion inhibition efficiency of the HEDOB inhibitor at four different temperatures (25-55 °C). The corrosion inhibition of hydroxy-ethoxy HEDOB surfactant inhibitor is dependent on both its effective concentration and solution temperatures as clarified via weight loss results with maximum inhibition efficiency 88.9% at 1000 μM and 55°C. Langmuir's adsorption isotherm was confined as best fitted isotherm describes the physical-chemical adsorption capability of the HEDOB on the steel surface with change in the free energy of adsorption from -38.8 to -43.6 kJ/mol. The provided Tafel polarization results revealed that the hydroxy-ethoxy HEDOB surfactant promote the suppression both the cathodic and anodic reactions behaving as mixed-type inhibitor. The surface morphology techniques SEM and AFM revealed that, the HEDOB inhibitor is confined on the surface of the steel. The Quantum theoretical study revealed the correlation between the hydroxy-ethoxy HEDOB molecular chemical structure and its inhibition efficiency.

For the corrosion of carbon steel in 1.0 M HCl solution, the new pyrazolone derivatives (PY1 and PY2) have been identified as active corrosion inhibitors. Clear evidence of the inhibitory effect of pyrazolone derivatives is given by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) measurements. The synthesized compounds were characterized by spectroscopic and 1H-NMR techniques. The purity of compounds was confirmed by TLC. Our findings show that pyrazolone compounds inhibited the corrosion of carbon steel in the acid medium. Inhibition efficiency increases with the increase in concentration of compounds. The inhibition efficiency of PY2 was higher than that of PY1. These inhibitors obey the Temkin adsorption isotherm. It was found that the pyrazolone derivatives act by physisorption on carbon steel.

The effectiveness of using Tilia cordata extract as a green corrosion inhibitor for carbon steel in 1 M hydrochloric acid solutions was demonstrated by employing some chemical and electrochemical techniques. The surface morphology of C-steel specimens was examined. The results showed that Tilia cordata has corrosion inhibition characteristics with efficiency of 96% as the concentration of Tilia cordata extract increased to 300 mg L−1. Charge transfer resistance (R ct) value increases while both the capacitance of the double layer (C dl) and corrosion current (i corr) values decrease with increasing the extract concentration. The effect of temperature was studied in the range 30–60 °C. Some thermodynamic parameters were calculated and discussed. The adsorption of extract on the C-steel surface was found to obey Langmuir adsorption isotherm. Polarization results showed that the investigated extract acts as mixed type inhibitor. All the different used techniques gave similar results.

The corrosion behavior of copper in the presence of thiophene (T) and some of its derivatives [2-thiophene carboxylic acid (TC) and 2-thienyl ethanol (TE)] has been investigated in 2 M HNO3 solution using electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and weight loss techniques. Polarization studies showed that these compounds act as mixed type inhibitors. EFM technique provides a new tool for electrochemical corrosion monitoring and was used as an effective method for corrosion rate determination. In EFM measurements corrosion current density was determined without prior knowledge of Tafel slopes. Inhibition efficiency of these compounds has been found to vary with concentrations of the compounds and temperature. The adsorption of these compounds on the copper surface from the acid solution has been found to obey Langmuir adsorption isotherm. The thermodynamic activation parameters of copper corrosion in 2 M HNO3 were determined and discussed. The results obtained from EFM, EIS, Tafel and weight loss measurements were in good agreement.

Three newly cationic surfactants based on 2-(2-(dimethyl amino) ethoxy) ethanol were prepared through direct quaternization with different alkyl bromide. The chemical structures of the synthesized surfactants were confirmed by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. The critical micelle concentrations have been estimated using two different techniques surface tension and conductometric measurements at three different temperatures 25, 45 and 65 °C. The surface parameters were found hydrophobic and temperature dependent. The tail elongation and raising the solution temperature has a reverse effect on the critical micelle concentration. The calculated thermodynamic parameters proved that the synthesized surfactant favor the adsorption at the interfaces than aggregation in micelles. The synthesized surfactant HEDDB has the maximum antibiotic effect against the tested gram positive and negative bacteria and even higher than the used drug. The surfactant HEDHB has higher antifungal activity than the reference drug. The simply synthesized surfactant showed a high effect against sulfate reducing bacteria at low concentration.

In this work, the inhibitive effect of some antibacterial drugs against the corrosion of 316 stainless steel in 1M HCl has been studied by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The inhibiting effect explained by adsorption of the additives on steel surface. The inhibition efficiency increases with increasing the inhibitors concentrations and decreases with increasing the temperature. The data obtained fit well to Langmuir adsorption isotherm and the kinetic-thermodynamic model. The results of polarization studies indicate that the investigated antibacterial drugs are mixed type inhibitors. Increasing the inhibition efficiency of the investigated inhibitors with the addition of iodide ions indicates that iodide ions play important role in the adsorption process. The efficiencies obtained from the different electrochemical techniques were in good agreement which prove the validity of these tools in the measurements of the tested inhibitors.

The effect of the addition of some quinazoline derivatives on the corrosion of stainless steel 304 (SS 304) in hydrochloric acid medium was investigated using electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and weight reduction measurements, The inhibition efficiency increases with increasing the inhibitor concentration, but decreases with increasing the temperature. The adsorption of these compounds on the stainless steel 304 surface follows Langmuir isotherm. Potentiodynamic polarization studies showed that these compounds are mixed-type inhibitors. The results obtained from all the measurements are in good agreement. The effect of temperature in the range 298–328 K on the corrosion of stainless steel 304 in 1 M HCl was tested and thermodynamic parameters were computed and discussed.

Five compounds of 5-arylazothiazole derivatives were studied as inhibitors for corrosion of 1018 carbon steel in 0.5 M H2SO4 solution using weight loss and galvanostatic polarization techniques. The percentage inhibition efficiency increases with increasing the concentration of inhibitor, with decreasing the temperature and the presence of the electron donating group in the chemical structure of the inhibitor. Inhibition was interpreted in view of adsorption of these compounds on the steel surface. The adsorption mechanism obeys Freundlish isotherm. The addition of KI to 5-arylazothiazole derivatives improved the inhibition efficiency due to the synergistic effect. Some thermodynamic parameter functions were computed and explained. The polarization curves revealed that the inhibitors were of mixed type.

Novel series of Co2+, Ni2+, Cu2+, Mn2+ and Fe3+complexes derived from 4,4-dimethyl-2,6-dioxo-N-phenylcyclohexanecarbothioamide (HDDPT) were prepared and characterized by conventional techniques. The complexes have adopted the formulae; {[Mn(DDPT)Cl(H2O)3]·3H2O, [Ni(DDPT-H)(H2O)(OH)], [Cu (HDDPT) Cl2(H2O)2]·2H2O, [Co(HDDPT)2Cl2] and [Fe (DDPT)Cl2], respectively. Spectral data revealed that HDDPT coordinates as OS donor in a neutral or mononegative manner. Electronic and magnetic measurements suggested a square planar geometry for Ni2+ complex and an octahedral one for the other complexes. X-ray powder diffraction data suggested monoclinic and orthorhombic structures for Fe3+ and Ni2+complexes, respectively. DFT method was utilized to prove the geometry and evaluate the bond lengths, bond angles as well as different energetic parameters. The thermal stability of the compounds was examined and the corresponding thermodynamic parameters were determined using Coats-Redfern and Horowitz-Metzger methods. Also, the corrosion hindrance of carbon steel (CS) in 0.5 M HCl by HDDPT was carried out using potentiodynamic polarization (PP) measurement. The data proved the thiosemicarbazide to be a powerful inhibitor and it is demonstrated that the protection efficiency and surface converge (Ɵ) increase with increasing the inhibitor concentration and decrease with increasing temperature. Finally, the adsorption procedure obeys Langmuir’s adsorption isotherm. Moreover, all compounds were screened against the growth of four pathogenic bacterial strains.

Yellow crystals of the coordination polymers MOF[Ag (qox) NO3], 1 [Ag(pyzca)], 2 were obtained by the reaction of AgNO3 with quinoxaline (qox) or pyrazine carboxylic acid (pyzca). The MOFs 1 and 2 were tested as corrosion inhibitors for copper in 1 M HCl solutions using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Results of the polarization revealed that these coordination polymers are mixed type. Adsorption of the MOFs 1 and 2 was found to obey Langmuir adsorption isotherm. The effect of temperature on the corrosion rate was studied and activation parameters were calculated and discussed. The results obtained from the two different electrochemical techniques are in good agreement.

In this study, the effect of imidazole derivatives on the inhibition of aluminum corrosion in 0.5 M HCl has been studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) measurements. The results show that all imidazole derivatives are good inhibitors, and inhibition efficiency follows the order: B > A. Polarization curves demonstrated that the imidazole derivatives were of mixed-type inhibitors. The adsorption of each inhibitor on aluminum surface obeys Frumkin adsorption isotherm. Surface morphology studies were done using scanning electron microscopy (SEM) to characterize the film formed on aluminum surface. Quantum chemical calculations show that imidazole derivatives can adsorb on the aluminum surface through the nitrogen atoms as well as π-electrons in the imidazole ring.

The role of some heterocyclic compounds (1–3) as corrosion inhibitors for Csteel in 1 M HCl have been studied using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Polarization studies showed that all the compounds studied are mixed type inhibitors. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were calculated and discussed. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The presence of these compounds in the solution decreases the double layer capacitance and increases the charge transfer resistance. The adsorption of these compounds on C-steel surface was found to obey Temkin’s adsorption isotherm. The morphology of inhibited and uninhibited Csteel was analyzed by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX).

The corrosion behavior of 1018 carbon steel in 0.5 M HCl solution in the absence and presence some benzothazol-2-cyanomethyl derivatives was investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The results obtained from these techniques show that, the inhibition efficiency of these inhibitors increased with increase in inhibitor concentration but deceased with rise in temperature. Adsorption of these derivatives follows the Temkin adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed-type inhibitors for both anodic and cathodic reactions. Some activated thermodynamic parameters were computed and discussed. The results obtained from the four different techniques were in good agreement. Quantum structure-activity relationships have been used to study the effect of molecular structure on inhibition efficiency of the inhibitors.

The inhibiting action of some p-aminoazobenzene derivatives towards the corrosion behavior of stainless steel type 316L in 3M HCl has been studied using weight loss, galvanostatic and potentiodynamic anodic polarization techniques. The inhibition efficiency of the investigated compounds was found to increase with increasing the concentration of inhibitor and with decreasing the temperature. The addition of KI to p-aminoazobenzene derivatives increased the inhibition efficiency due to synergistic effect. The presence of iodide ions in the solution stabilized the adsorption of these compounds on the steel surface and, therefore, improved the inhibition efficiency. Inhibition process was explained on the basis of adsorption of these compounds on the metal surface. The degree of surface coverage varied linearly with logarithm of inhibitor concentration fitting Temkin isotherm. Some thermodynamic parameters were calculated and discussed. It was found that, the p-aminoazobenzene derivatives provide a good protection to stainless steel against pitting corrosion.

The inhibitive effect of some heterocyclic organic compounds on the corrosion of 304 stainless steel (304 SS) in 1 M HCl was studied using weight loss, open potential circuit, potentiodynamic polarization and electrochemical impedance spectroscopy techniques at room temperature. The polarization curves revealed that these investigated compounds act as mixed-type inhibitors. Adsorption of these inhibitors on 304 SS surface was found to obey the Langmuir adsorption isotherm. Results showed that the corrosion rate of SS increased with raising temperature and decreased in the presence of investigated compounds. The highest inhibition efficiency of 70.1% was observed with these investigated compounds. An improved inhibition efficiency of 94.5% was observed with the mixture of these compounds and KI at 25 °C in 1 M HCl. This indicates that these compounds were assumed to adsorb on SS surface via physical adsorption. The reactivity of these compounds was analyzed through theoretical calculations based on semi-empirical theory

Tecoma extract was investigated as a green corrosion inhibitor for aluminum in 1 M H2SO4 solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. It was found that this extract presented excellent corrosion inhibition performance for aluminum and show the maximum 90.2% inhibition efficiency at 300 ppm. Polarization curves revealed that the used extract represents mixed-type inhibitor. Adsorption of used extract led to a reduction in the double-layer capacitance and an increase in the charge transfer resistance. The inhibition efficiency was improved with concentration of the extract, while decreased with improvement of corrosion temperature of the medium. The adsorption isotherm of the extract on aluminum surface conformed to the Langmuir adsorption model. Surface analysis was tested using scanning electron microscope. The results obtained from all investigated techniques are in good agreement.

Oxazole derivatives were investigated as corrosion inhibitors for 316L stainless steel (SS) in sulfamic acid (NH2HSO3) solutions by potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation techniques. The results showed the variation in inhibition performance of the inhibitors with varying concentrations and temperatures. The maximum efficiency was found to be 91% at 2 × 10−4 M concentration of the inhibitors for the immersion period of 3 h. Langmuir was tested to describe the adsorption behavior of inhibitor on 316LSS surface. Potentiodynamic polarization study clearly revealed that these compounds act as mixed-type inhibitors. The results of the electrochemical impedance study showed a decrease in double layer capacitance and increase in charge transfer resistance. The results of various electrochemical techniques show good agreements with each other.

Yellow crystals of the coordination polymers (CP) [Ag(qox)NO3], 1 [Ag(pyzca)], 2 were obtained by the reaction of AgNO3, quinoxaline (qox) or pyrazinecarboxylic acid (pyzcaH), respectively. The crystal structure of 1 displays 1D-extended chain of [Ag(qox)]n with NO3 coordinated to every Ag atom. The 1D-chains of 1 are interconnected by strong hydrogen bonds, π–π stacking and short contacts developing two dimensional sheets containing channels. Furthermore, the overall packing arrangement of 1 results 3D topology with corrugated network. The Ag atom in 2 acquires tetrahedral geometry while each pyzca ligand provides three donor sites connected to three Ag atoms. The structure of CP 2 displays 1D-extended helical chain of [Ag(pyzca)]n. The 3D-packing of the CP 2 creates nanometer pores. The luminescence properties of 1 and 2 were discussed.

The effect of N-thiazolyl-2-cyanoacetamide derivatives on the corrosion of aluminum in 0.01N sodium hydroxide has been studied using weight-loss and glvanostatic polarization techniques. The inhibition efficiency was found to increase with increasing the concentration of inhibitor and with decreasing temperature. The inhibition process was explained in terms of its adsorption on the aluminum surface The adsorption is obeyed Frumkin isotherm. The addition of Ba2+, Sr2+, Ca2+ and Mg2+ ions to N-thiazolyl-2-cyanoacetamide derivatives enhanced the inhibition efficiency due to synergistic effect. Polarization data suggested that the additives used as mixed type inhibitors. Some activated thermodynamic parameters were calculated and explained.

Corrosion inhibition and adsorption behavior of two triazole derivatives on API 5L-B carbon steel in CO2-saturated 3.5% NaCl solutions was investigated using potentiodynamic polarization, EIS and EFM techniques. Specimen surfaces were characterized using SEM, EDX and XRD. Results show that the two compounds are mixed-type inhibitors and inhibition efficiency increases with increasing concentrations. Adsorption of the two compounds is a mixed between chemisorptions and physisorption and obeys Langmuir adsorption isotherm. Activation energy and thermodynamic parameters were calculated. Surface analyses confirm the formation of iron nitrides on the metal surface, which supports results obtained from previous techniques.

The electrochemical behavior and corrosion inhibition of zinc in 0.5 M H2SO4 in the absence and presence of some chromones has been investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectros- copy (EIS) and electrochemical frequency modulation (EFM) techniques. The presence of these investigated compounds in the corrosive solutions decrease the weight loss, the corrosion current density, and double layer capacitance but increases the charge transfer resistance. Polarization studies were carried out at room temperature, and showed that all the studied com- pounds act as mixed type inhibitors with a slight predominance of cathodic character. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were determined and discussed. The adsorption of the investigated compounds on zinc was found to obey Langmuir adsorption isotherm.

The inhibition effect of some phenyl sulfonylacetophenoneazo derivatives (PSAAD) on the corrosion of Al in 0.5 M HCl solutions was studied by potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation. The results obtained showed that the addition of the PSAAD inhibits the hydrochloric acid corrosion of Al. Potentiodynamic polarization measurements showed that the PSAAD act as mixed type inhibitors but predominately act as cathodic inhibitors. The inhibition efficiency increases with increasing the PSAAD concentration, but decreases with increasing temperature. A kinetic model and the Langmuir adsorption isotherm fit the experimental data well. A good correlation was found between the theoretical data and the experimental results.

The corrosion inhibition of C-steel in 1 M HCl solution by cyanoacetamide derivatives was investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The results obtained from these techniques show that, the inhibition efficiency of these inhibitors increased with increase in inhibitor concentration but deceased with rise in temperature. Adsorption of these derivatives follows the Temkin adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed-type inhibitors for both anodic and cathodic reactions. Some activated thermodynamic parameters were computed and discussed. The results obtained from the four different techniques were in good agreement. Quantum structure-activity relationships have been used to study the effect of molecular structure on inhibition efficiency of the inhibitors.

Corrosion inhibition of 304 stainless steel (SS) in 1 M HCl by aqueous extract of coriander seeds was studied using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modu- lation (EFM) techniques. Values of inhibition efficiency obtained are dependent upon the concentration of extract and temperature. Gen- erally, inhibition was found to increase with inhibitor concentration, but decrease with temperature. Physical adsorption mechanism has been proposed for the inhibition with Langmuir adsorption isotherm obeyed. Values of activation energy of the inhibited cor- rosion reaction of 304 SS are greater than the value obtained for the blank. Thermodynamic consideration reveals that adsorp- tion of aqueous extract of coriander seeds 304 SS surface is spontaneous.

The inhibiting effect of phenazone and aminophenazone towards the corrosion of aluminum–silicon alloy in 1 M HCl was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The results of these techniques showed that, the inhibition efficiency of these compounds depends on both their concentrations and chemical structures. Investigated organic molecules inhibit the corrosion process by the adsorption on alloy surface. The adsorption process was found to obey Temkin adsorption isotherm. The effect of the temperature on the rate of corrosion in the absence and presence of inhibitors was studied. Some activated thermodynamic parameters were computed and discussed. Potentiodynamic polarization data indicated that these inhibitors act as mixed type inhibitors. Also from impedance data it is found that the corrosion of aluminum–silicon alloy is controlled by charge transfer process at all concentrations of inhibitors. Quantum chemical parameters were constructed in order to characterize the inhibition performance of the tested molecules.

Inhibition of QD36 steel corrosion in 0.5 M HCl solution by aniline derivatives was studied using chemical (weight loss), potentiodynamic polarization and electrochemical frequency modulation measurements. The adsorption process of studied aniline derivatives on steel surface obeys the Langmuir adsorption isotherm. The values of activation energy (E*a), adsorption equilibrium constant (Kads), free energy of adsorption (ΔGads°, adsorption enthalpy (ΔHads°) and adsorption entropy (ΔSads°)were calculated and discussed. Potentiodynamic polarization measurements showed that aniline derivatives are mixed-type inhibitors. The results obtained by EFM technique were shown to be in agreement with other chemical and electrochemical techniques. Scaning electron microscope (SEM) was used to study the surface morphology of the QD36 steel in 0.5 M HCl solution in the absence and presence of inhibitors. Further, theoretical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.

The inhibiting effect of some chalcones derivatives on the corrosion of carbon steel in 1 M HCl was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The results showed that the inhibition efficiency increases with increasing the inhibitor concentration, while it decreases with increasing the temperature. The adsorption of chalcones derivatives on the carbon steel surface obeys Langmuir adsorption isotherm. Some thermodynamic parameters were calculated and discussed. The values of free energy of adsorption for investigated inhibitors were calculated. Polarization curves showed that chalcones derivatives are mixed-type inhibitors but the cathode is more polarized than the anode. The variation in inhibition efficiency depends on the type of the substituent groups in the benzene ring. It was found that the presence of donating group (such as OCH3) better facilitates the adsorption of molecules on the surface than in the case with withdrawing groups (such as – Cl and NO2). The data obtained from the four different methods were in good agreement. Key words: Carbon steel, HCl, corrosion inhibition, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), chalcones derivatives.

Corrosion inhibition of carbon steel in HCl by azo dye derivatives (ADD) was investigated using chemical and electrochemical techniques. Results obtained indicate that ADD inhibited the corrosion of carbon steel in the acid medium. Inhibition efficiency increases with increase in ADD concentration and is synergistically enhanced on addition of iodide and bromide ions. By fitting the obtained experimental data with the Langmuir adsorption model and the Arrhenius equation, some thermodynamic and kinetic parameters for the corrosion process were estimated, and the values support the results obtained. Some quantum chemical parameters and the Mulliken charge densities for ADD were calculated by the MNDO semi-empirical method to provide further insight into the mechanism of inhibition of the corrosion process.

The inhibitive and adsorptive characteristics of ethanol extract of fennel seeds for the corrosion of 304 stainless steel (SS) in 1 M HCl solutions have been studied using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation methods for monitoring corrosion. Ethanol extract of fennel is a good adsorption inhibitor for the corrosion of 304 SS in HCl. The inhibitive property of the extract is attributed to the presence of anethol and fenchone as major constituents in the extract. Inhibition efficiency increased with increasing concentration of the extract but decreased by increasing the temperature. Adsorption studies revealed that Langmuir adsorption isotherm is the best adsorption model applicable to the adsorption of fennel extract on 304 SS surface. Activation and adsorption parameters were evaluated and discussed. Potentiodynamic polarization measurements indicated that the inhibitor is of mixed type. The results obtained fr...

Corrosion inhibition of mild steel used in water station in 35 ppm aluminum sulfate and 10 ppm chloride solu- tion by Camellia sinensis leaves extract was studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy techniques at 30 o C. Results show that the inhibition efficiency increases with increasing concentra- tion of the extract and decreases with increasing temperature. Inhibitive effect was afforded by adsorption of the extract's components which was found to accord with Langmuir adsorption isotherm. Inhibition mechanism is deduced from the tem- perature dependence of the inhibition efficiency and was further corroborated by the values of activation parameters obtained from the experimental data. water plant) of composition (wt%) 0.13 C, 0.029 Si, 0.018 S, 0.0067 P, 0.397 Mn, 0.025 Ni, 0.0076 Cr, 0.0020 Mo, 0.0010 V, 0.036 Cu, 0.0010 Sn, 0.0057 Co, 0.126 Al, 0.023 Zn, 0.0020 Mg, 0.0046 Nb, and 0.0025 Bi, the rest Fe. The sheet was mechanically pressed and cut into cou- pons, each of dimensions, 20×18×1 mm. They were then ground with silicon carbide abrasive papers, polished, cleaned thoroughly, rinsed in ultrasonic cleaner, dried and kept in desiccator for further weight- loss tests. The weight loss was determined by weighting the cleaned samples before and after hanging the sample into 100 ml of cor

Extract of ginger has been evaluated as a green inhibitor for the corrosion of steel in sulfide polluted NaCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Potentiodynamic polarization measurements showed that this extract acts as a mixed type inhibitor but mainly inhibits the cathodic reaction. The inhibition efficiency was found to increase with inhibitor concentra- tion reaching to approximately 83.9% using 250 ppm of ginger. Nyquist plots show a single capacitive loop in uninhibited and inhibited solutions. From EFM the causality factors are very close to theoretical values which indicate that the measured data are of good quality. The adsorption process of the studied extract on steel surface obeys Temkin adsorption isotherm. The results obtained from the different electrochemical techniques were in good agreement which prove the validity of these tools in measurement of corrosion rate. Ginger extract has no effect on Escherichia Coli and can be applied safely on waste water treatment plants.

The inhibition effect of cefoperazone (CP) on the corrosion behavior of carbon steel in 0.5 M HCl solution was studied using potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation techniques along with scanning electron microscopy (SEM). Results showed that the inhibition efficiency increases with increasing inhibitor concentration and decreases with increasing the temperature. The results indicated that the inhibitive action of CP can be attributed to its adsorption. The results show that CP possesses excellent inhibiting effect for the corrosion of carbon steel and the inhibitor acts as mixed-type inhibitor. The adsorption process is spontaneous and follows Langmuir adsorption isotherm model. The surface adsorption of the inhibitor molecules decreases the double-layer capacitance and increases the polarization resistance. SEM results indicate the formation of an adsorbed protective film on the metal surface. The results obtained from the different techniques were in good agreement which prove the validity of these tools in the measurements of the tested inhibitor.

Lanthanides have been evaluated as new corrosion inhibitors for the corrosion of iron in 3.5% NaCl solutions using electrochemical techniques [potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation]. The adsorption of lanthanides on iron surface was found to be of neither a typical physisorption nor a typical chemisorption mode. Increase in temperature increases corrosion rate but decreases inhibition efficiency. The thermodynamic functions of activation have been evaluated. The polarization measurements indicated that the inhibitors are of mixed type. The adsorption of these compounds was found to obey Langmuir’s adsorption isotherm. The analysis of scanning electron microscopy and electron dispersion X-Ray confirmed the formation of precipitates of lanthanides on iron surface, which reduced the overall corrosion reaction.

Inhibition of carbon steel corrosion in 2 M hydrochloric acid (HCl) solution by thiophene azo dye derivatives were studied using weight loss, electrochemical frequency modulation (EFM), and atomic absorption techniques. The experimental data suggest that the inhibition efficiency increases with increasing inhibitors concentration in presence of 103 μM potassium iodide (KI). This is due to synergistic effect. Thus, the experimental results suggested that the presence of these anions in the solution stabilized the adsorption of inhibitors molecules on the metal surface and improved the inhibition efficiency. The results of EFM experiments are a spectrum of current response as a function of frequency. The corrosion rate and Tafel parameters can be obtained with measurement by analyzing the harmonic frequencies. The adsorption of the inhibitors on metal surface obeys the Langmuir adsorption isotherm. The surface of metal examined using Fourier transform infrared and ultraviolet spectroscopy. Quantum chemical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.

Inhibition of nickel corrosion in 1 M HCl solution in the absence and presence of some Cephalosporin antibiotics derivatives was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The results obtained show that the inhibition efficiency of these compounds depends on their concentrations and chemical structures. The inhibitive action of these compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structures following the Langmuir adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed inhibitors for both anodic and cathodic reactions. The effect of temperature on the rate of corrosion in the absence and presence of these compounds was also studied. The efficiencies obtained from the potentiodynamic polarization technique were in good agreement with those obtained from EIS and EFM techniques. This proves the validity of these tools in the measurements of the investigated inhibitors.