Essential oil of Salvia aucheri mesatlantica as a green inhibitor for the corrosion of steel in 0.5 M H2SO4

Essential oil of aerial parts of Salvia aucheri Boiss. var. mesatlantica was obtained by hydrodistillation and analyzed by GC and GC/MS. The oil was predominated by camphor (49.59%). The inhibitory effect of this essential oil was estimated on the corrosion of steel in 0.5 M H₂SO₄ using electrochemical polarization and weight loss measurements. The corrosion rate of steel is decreased in the presence of natural oil. The inhibition efficiency was found to increase with oil content to attain 86.12% at 2 g/L. Polarization curves revealed that the oil of S. aucheri mesatlantica acts as mixed type inhibitor with a strong predominance of anodic character. The temperature effect on the corrosion behavior of steel in 0.5 M H₂SO₄ without and with the inhibitor at 2 g/L was studied in the temperature range from 303 to 343 K, the associated activation energy have been determined. The adsorption of oil on the steel surface was found to obey Langmuir’s adsorption isotherm.     

Corrosion inhibition of copper in chloride media by 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile: Electrochemical and theoretical study

Electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization have been used to investigate the inhibition effect of a new pyrimidine heterocyclic derivative, namely 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (MPD) on copper corrosion in 3.5% NaCl solutions at 25 ± 1 °C. The electrochemical investigations showed that MPD gives sufficient inhibition against copper corrosion in 3.5% NaCl solutions. Potentiodynamic polarization measurements have shown that the MPD inhibit both the cathodic and anodic processes and thus it classified as mixed-type inhibitor. EIS measurements indicate that the values of constant phase elements (CPEs) tend to decrease and both charge-transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. Electrochemical kinetic parameters obtained using EFM methods were comparable with that calculated from traditional measurements (EIS and potentiodynamic polarization). Molecular simulation technique was used to investigate the adsorption configuration of MPD on copper surface. Number of electrons transferred from MPD to the copper surface was calculated by semi-empirical quantum chemical calculations.     

Inhibiting effects of 2-mercapto-1-methylimidazole on copper corrosion in 0.5 M sulfuric acid

The inhibiting efficiency of 2-mercapto-1-methylimidazole (MMI) on copper corrosion in sulfuric acid was investigated at 30 °C. Its effectiveness was assessed through electrochemical impedance spectroscopy, potentiodynamic polarization and gravimetric measurements. The results of study reveal that the inhibition efficiency of MMI depends on its concentration and attains approximately 81% at 10^?4 M. The inhibitor was adsorbed on the copper surface according the Langmuir adsorption isotherm model. The value of standard free energy of adsorption was calculated from this isotherm.     

Electrochemical investigation of corrosion and corrosion inhibition of iron in hydrochloric acid solutions

The inhibition effect of 1-methyl pyrazole (MPA) on the acidic corrosion of iron in 1.0 M HCl was studied at different concentrations (10^?3–10^?2 M) by potentiodynamic polarization and electrochemical impedance spectroscopy, and EIS measurements. It is found from the polarization studies that methyl pyrazole (MPA) behaves mainly as anodic inhibitor in HCl. Values of polarization resistance (R_p) and double layer capacitance (C_dl) in the absence and presence of MPA in 1.0 M HCl are determined. The adsorption of MPA on iron surface from HCl is found to obey Temkin adsorption isotherm.     

On the corrosion inhibition of iron in hydrochloric acid solutions,Part I: Electrochemical DC and AC studies

The inhibitive action of 4-methyl pyrazole (4MP) against the corrosion of iron (99.9999%) in solutions of hydrochloric acid has been studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). At inhibitor concentration range (10^?3–10^?2 M) in 1.0 M acid, the results showed that 4MP suppressed mainly the anodic processes of iron corrosion in 1.0 M HCl by adsorption on the iron surface according to Temkin adsorption isotherm. Both potentiodynamic and EIS measurements reveal that 4MP inhibits the iron corrosion in 1.0 M HCl and that the efficiency increases with increasing inhibitor concentration. Data obtained from EIS were analyzed to model the corrosion inhibition process through an equivalent circuit.     

Inhibition effect of hexadecyl pyridinium bromide on the corrosion behavior of some austenitic stainless steels in H2SO4 solutions

The inhibition effect of hexadecyl pyridinium bromide (HDPB) as a cationic surfactant on the corrosion behavior of some Egyptian austenitic stainless steel SS 304L, SS 316H and SS 304H in 0.5 M H₂SO₄ solutions was investigated by using potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results indicate that HDPB is a good inhibitor for the samples under investigation in 0.5 M H₂SO₄ solutions. In addition, the inhibition efficiency η% increases with the inhibitor concentration while decreases with the increasing temperature referring to physical adsorption. The adsorption of the inhibitor obeys a Temkin adsorption isotherm. Polarization curves show that HDPB is a mixed inhibitor in H₂SO₄ solutions. The results obtained from polarization and impedance measurements are in good agreement. Activation-free energies, enthalpies, and entropies for the inhibition process of HDPB were determined.     

Ceratonia siliqua extract as a green corrosion inhibitor for copper and brass in nitric acid solutions

ABSTRACT

The influence of extract of ceratonia siliqua extract on the corrosion of copper and brass in aqueous 1 M nitric acid was examined by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. The surface morphology was analyzed using scanning electron microscope and energy dispersive X-ray techniques. Potentiodynamic polarization curves indicated that the plant extract behaves as cathodic inhibitor. The results indicate that the extract solution of the plant could serve as an effective inhibitor for the corrosion of copper and brass in nitric acid media. As temperature increases, percentage of inhibition decreases. The degree of surface coverage of the adsorbed inhibitor was determined by weight-loss technique, and it was found that the results obeyed the Langmuir adsorption isotherm.     

A combined computational & electrochemical exploration of the Ammi visnaga L. extract as a green corrosion inhibitor for carbon steel in HCl solution

Natural-based corrosion inhibitors have gained great research interest thanks to their low cost and higher performance. In this work, the chemical composition of the methanolic extract of Ammi visnaga umbels (AVU) was evaluated by gas chromatography (GC) coupled with mass spectrometry (MS) and applied for corrosion inhibition of carbon steel (CS) in 1.0 mol/L HCl using chemical and electrochemical techniques along with scanning electron microscope (SEM) and theoretical calculations. A total of 46 compounds were identified, representing 89.89% of the overall chemical composition of AVU extract, including Edulisin III (72.88%), Binapacryl (4.32%), Khellin (1.97%), and Visnagin (1.65%). Chemical (Weight loss) and electrochemical (potentiodynamic polarization curves (PPC), and electrochemical impedance spectroscopy (EIS)) techniques revealed that investigated extract can be used as an effective corrosion inhibitor for carbon steel in 1.0 mol/L HCl solution. At a low dose of 700 ppm, the inhibitory action of AVU extract reached an inhibition efficiency of 84 percent. According to polarization tests, the investigated extract worked as a mixed inhibitor, protecting cathodic and anodic corrosion reactions. The EIS test showed that upon the addition of AVU extract to HCl solution, the polarization resistance increased while the double layer decreased. SEM images showed a protected CS surface in the inhibited solution. Quantum chemical calculations by Density Functional Theory (DFT) for the main components confirmed the major role of heteroatoms and aromatic rings as adsorption sites. Molecular dynamics (MD) simulation was used to study the adsorption configuration of the main components on the Fe(1 1 0) surface. Outcomes from this study further confirmed the significant advantage of using plant-based corrosion inhibitors for protecting metals and alloys.     

An experimental and theoretical investigation on adsorption properties of some diphenolic Schiff bases as corrosion inhibitors at acidic solution/mild steel interface

The effect of novel synthesized three Schiff bases, namely, 1,3-bis[2-(2-hydroxy benzylidenamino) phenoxy] propane (P1), 1,3-bis[2-(5-chloro-2-hydroxybenzylidenamino) phenoxy] propane (P2), and 1,3-bis[2-(5-bromo-2-hydroxybenzylidenamino) phenoxy] propane (P3), on the corrosion of mild steel in 0.1 M HCl was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy methods. Polarization measurements suggest that P1 acts as mixed type inhibitor while P2 and P3 behave as mainly cathodic inhibitors for acidic corrosion of steel. All electrochemical measurements show that inhibition efficiencies increase with increase in inhibitor concentration. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on steel surface. Adsorption of these inhibitors follows Temkin adsorption isotherm. The correlation between the adsorption ability of inhibitors and their molecular structures has been investigated using quantum chemical parameters obtained by MNDO semi-empirical method. Calculated quantum chemical parameters indicate that Schiff bases adsorbed on steel surface by chemical mechanism.     

Study of the inhibition of the corrosion of copper and zinc in HNO3 solution by electrochemical technique and quantum chemical calculations

The corrosion inhibition of copper and zinc in 0.1 M HNO₃ by 1,2,3,4-tetrazole (TTZ) and some of its derivatives has been analysed in a comparative study. Two experimental techniques have been used such as weight-loss and electrochemical polarization measurements. The results obtained reveal that the addition of these compounds reduces preferentially the corrosion of Cu rather than that of Zn. The adsorption of tetrazolic compounds on a copper surface was more favourable than their adsorption on a zinc surface. Moreover the inhibition efficiency calculated for copper was found to attain 95% in the presence of 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMT) while it remains constant at 1% for all compounds tested using zinc as electrode. Relationship between molecular structure and their inhibition efficiency was elucidated by quantum chemical calculations using the density functional theory (DFT).     

Monitoring corrosion and corrosion control of low alloy ASTM A213 grade T22 boiler steel in HCl solutions

Rates of corrosion of low alloy ASTM A213 grade T22 boiler steel were monitored in aerated stagnant 0.50 M HCl solutions at different temperatures (283–303 K) using Tafel extrapolation method and the non-destructive electrochemical frequency modulation (EFM) technique, complemented with XPS examinations. Serine (Ser) was introduced as a corrosion-safe inhibitor. Corrosion rates (in μm y^?1) obtained from these two methods was in good agreement. Tafel plots showed that Ser acted mainly as a cathodic-type inhibitor. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. XPS examinations of the electrode surface confirmed the existence of such adsorbed film. The inhibition efficiency increased with increase in Ser concentration, while it decreased with temperature, suggesting physical adsorption. Activation energies have been calculated in the absence and presence of various concentrations of Ser by measuring the temperature dependence of the corrosion rate obtained from the two methods employed. It was found that the activation energy in the presence of Ser is higher than that in bare HCl solution. The adsorptive behaviour of Ser followed Temkin-type isotherm. The standard free energy of adsorption was estimated to be ?25 kJ mol^?1 at 303 K. These results confirmed the occurrence of physical adsorption.     

Polyvinyl alcohol–sulphanilic acid water soluble composite as corrosion inhibitor for mild steel in hydrochloric acid medium

The inhibitive action of synthesised polyvinyl alcohol–sulphanilic acid (PVASA) composite on the corrosion of commercial mild steel in 1 M HCl medium has been investigated by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopic (EIS) methods. Characterization of PVASA composite has been carried out using Fourier transform infrared spectroscopy (FTIR). Experimental results reveal that PVASA composite acts as an inhibitor in the acid environment. The inhibition efficiency increases with an increase in the concentration of the inhibitor. Maximum inhibition efficiency of PVASA composite was found to be 84% at 6000 ppm. Thermodynamic and kinetic parameters have been obtained from temperature studies. Electrochemical measurement reveals that PVASA composite acts as a mixed inhibitor and the adsorption follows Langmuir adsorption isotherm.     

Spirulina platensis – A novel green inhibitor for acid corrosion of mild steel

The inhibition of the corrosion of mild steel in 1 M HCl and 1 M H₂SO₄ by Spirulina platensis has been studied at different temperatures viz., 303 K, 313 K and 323 K by weight loss method, potentiodynamic polarization method, electrochemical impedance spectroscopy measurements and SEM analysis. The inhibition efficiency increased with increasing concentration of the inhibitor in both HCl and H₂SO₄ media. The results of weight loss studies correlated well with those of impedance and polarization studies. From the results of weight loss studies at various temperatures, the mode of adsorption is confirmed to be physisorption. Further the adsorption has been found to follow Temkin isotherm. From this isotherm, the free energy of adsorption (ΔG) and entropy (ΔS) are calculated. The study reveals the corrosion inhibition potential of S. platensis in both the acid media, thus bringing to light another facet of this microalga as it has so far been used only to produce antioxidant principles, finding extensive use in medicine especially as neutraceutical.     

Cephalosporin antibiotics as new corrosion inhibitors for nickel in HCl solution

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.     

Effect of three 2-allyl-p-mentha-6,8-dien-2-ols on inhibition of mild steel corrosion in 1 M HCl

2-Allyl-p-mentha-6,8-dien-2-ols P1−P3 synthesized from carvone P are tested as corrosion inhibitors of steel in 1 M HCl using weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods. The addition of 2-allyl-p-mentha-6,8-dien-2-ols reduced the corrosion rate. Potentiodynamic polarisation studies clearly reveal that the presence of inhibitors does not change the mechanism of hydrogen evolution and that they act essentially as cathodic inhibitors. 2-Allyl-p-mentha-6,8-dien-2-ols tested adsorb on the steel surface according to Langmuir isotherm. From the adsorption isotherm some thermodynamic data for the adsorption process are calculated and discussed. EIS measurements show the increase of the charge-transfer resistance with the inhibitor concentration. The highest inhibition efficiency (92%) is obtained for P1 at 3 g/L. The corrosion rate decreases with the rise of temperature. The corresponding activation energies are determined.     

Inhibition of copper corrosion in 3.5% NaCl solutions by a new pyrimidine derivative: electrochemical and computer simulation techniques

A new pyrimidine heterocyclic derivative, namely 2-ethylthio-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (EPD) was prepared and its inhibition performance towards copper corrosion in 3.5% NaCl solutions was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) measurements. Experimental investigations showed that EPD reduces markedly the copper corrosion in 3.5% NaCl solutions. EFM can be used as a rapid and non destructive technique for corrosion rate measurements without prior knowledge of Tafel constants. Monte Carlo simulation technique incorporating molecular mechanics and molecular dynamics can be used to simulate the adsorption of pyrimidine derivative (EPD) on the Cu (111) surface in 3.5% NaCl.     

Stearate as a green corrosion inhibitor of magnesium alloy ZE41 in sulfate medium

The efficiency of stearate as a corrosion inhibitor for magnesium alloy ZE41 has been studied in sodium sulfate medium, employing electrochemical techniques like potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of polarization study imply that stearate functions as a mixed-type corrosion inhibitor with a predominant anodic control. The adsorption of stearate on alloy surface is found to obey the Langmuir adsorption isotherm. The proposed inhibition mechanism involved adsorption of stearate onto metal surface, followed by precipitation of magnesium stearate within the microdefects of Mg(OH)₂ surface film which enhanced the barrier effect of an otherwise porous partially protective film.     

Experimental and theoretical studies of acridine orange as corrosion inhibitor for copper protection in acidic media

The corrosion process commonly limits the use of copper in practical applications. The use of corrosion inhibitors is one of the effective methods to reduce the corrosion rate of copper. In this research, the inhibition effect of acridine orange (3,6-bis(dimethylamine)acridine) (AcO) for the protection of copper in 0.5 ?M ?H₂SO₄ solution was studied. For this aim, the change of open circuit potential with exposure time (E_ocp-t), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), anodic and cathodic potentiodynamic polarization measurements (PP) and chronoamperometry (CA) techniques were used. Some quantum chemical parameters (E_HOMO, E_LUMO and dipole moment) were calculated and discussed. The AcO film formed over the copper surface was examined by SEM, EDX, AFM and contact angle measurements. The electrochemical data showed that AcO is an effective corrosion inhibitor even at low concentrations (ranging between 99.1% and %99.4 ?at concentrations from 0.01 ?mM to 1 ?mM). The corrosion rate of copper decreases in the presence of the inhibitor by reducing both anodic and cathodic rates, which is depended on its concentration. This compound behaves as mixed-type corrosion inhibitors with predominantly cathodic type. Its adsorption on the copper surface obeys Langmuir adsorption isotherm. The value of adsorption equilibrium constant (K_ads) and the standard free energy of adsorption were ΔG_ads 1.298 x 10³ ?M^?1 and -27.71 ?kJ/mol in the case of 0.5 ?M ?H₂SO₄ solution containing 1.0 ?mM AcO, which shows the adsorption is high and spontaneous. The adsorbed inhibitor film over the metal increase contact angle of the surface, which suggests the more hydrophobic properties of the surface are increasing coming from the orientation of hydrophobic sites to the electrolyte. The zero charge potential (E_pzc) studies showed that the surface charge of the metal is positive in the corrosive media containing the inhibitor. Quantum chemical calculations showed that the binding of inhibitor molecules to the metal surface takes place through N atoms of the inhibitor.     

Some new bipyrazole derivatives as corrosion inhibitors for C38 steel in acidic medium

Three new bipyrazole derivatives, ethyl 5,5′-dimethyl-1′H-1,3′-bipyrazole-4-carboxylate (Bip1), 1,1′,5,5′-tetramethyl-1H,1′H-3,3′-bipyrazole (Bip2), and 3-(bromomethyl)-5,5′-dimethyl-1′H-1,3′-bipyrazole (Bip3), have been synthesized and used as additives to protect C38 steel from corrosion in aerated 1 M HCl solution, using the various corrosion monitoring techniques such as weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy. All the techniques used for the studies show an increase in inhibition efficiency and decrease in the corrosion rate by increasing the inhibitor concentration. Impedance measurements showed that the double layer capacitance decreased and charge transfer resistance increased with increase in the inhibitors concentration, and hence an increase in inhibition efficiency. A potentiodynamic polarization study showed that all the inhibitors act as mixed-type. The adsorption of bipyrazole derivatives is found to obey the Langmuir adsorption isotherm, and the thermodynamic parameters were determined and are discussed.     

Assembly of succinic acid and isoxazolidine motifs in a single entity to mitigate CO2 corrosion of mild steel in saline media

Inhibition of CO₂ corrosion of mild steel in 0.5 M NaCl under atmospheric pressure at 40 °C as well as high pressure (10 bar) at 120 °C by 2-[2-methyl-4(or 5)-alkylisoxazolidin-5(or 4)-yl)methyl]succinic acids, a new class of molecules having inhibitive motifs of succinic acid, isoxazolidine and hydrophobic alkyl chain assembled in a single entity, has been examined by gravimetric and electrochemical methods. Inhibitor molecule containing CH₃(CH₂)₈ outperformed its counterpart with a shorter hydrophobe CH₃(CH₂)₄ and two other commercial imidazoline-based inhibitors. The effectiveness of these new inhibitors was also evaluated by electrochemical impedance spectroscopy. The inhibition efficiency by EIS was found to be 75%, 91% and 98% in the presence of 1, 5 and 20 ppm, respectively, at 40 °C. The potentiodynamic polarization studies indicated that the new inhibitors act as anodic inhibitors. The adsorption of the synthesized inhibitors follows Temkin adsorption isotherm model with favorable high values of –ΔG°_ads and −ΔH°_ads pointing the inhibitors adsorbed on the metal surface by chemisorption process. The XPS study confirmed the adsorption of the inhibitors on the metal surface.