Quantum chemical study of inhibition of the corrosion of mild steel in 1 M hydrochloric acid solution by newly synthesized benzamide derivatives

The inhibitory effect of some new synthesized benzamide compounds on corrosion of mild steel in 1 M HCl solution has been studied by use of weight loss measurements and the electrochemical techniques potentiodynamic polarization and electrochemical impedance spectroscopy. The inhibiting action is more pronounced with increasing concentration. Inhibition efficiency is maximum (approximately 99 %) at 10^?3 M. Polarization measurements also show that the compounds act as mixed inhibitors. The cathodic curves indicate that reduction of protons at the mild steel surface occurs as a result of a pure activating mechanism. EIS measurements reveal increased transfer resistance with increasing inhibitor concentration. The presence of heteroatoms increases inhibition efficiency without causing a drastic change in adsorption mechanism, which follows the Langmuir isotherm model. Significant correlations were obtained between inhibition efficiency with the chemical indexes calculated, by use of the standard software Gaussian03, on the basis of density functional theory (DFT) at the B3LYP/6-31G** level of theory, indicating that variation of inhibition with inhibitor structure may be explained in terms of electronic properties. The effect of temperature on the corrosion behaviour of steel in 1 M HCl without and with inhibitors at 10^?3 M was studied in the temperature range from 308 to 333 K, and the associated activation energy was determined.     

Experimental and theoretical study for corrosion inhibition of mild steel 1 M HCl solution by some new diaminopropanenitrile compounds

The inhibition of the corrosion of mild steel 1 M HCl solution by some diamine compounds has been investigated in relation to the concentration of the inhibitor as well as the temperature using weight loss and electrochemical measurements. The effect of the temperature on the corrosion behavior with the addition of different concentrations of new diamine compounds (3-[2-(2-cyano-ethylamino)-methylamino]-propionitrile (P1); 3-[2-(2-cyano-ethylamino)-ethylamino]-propionitrile (P2), and 3-[6-(2-cyano-ethylamino)-hexylamino]-propionitrile (P3), respectively, was studied in the temperature range 40–80 °C. Polarization curves reveal that (P1, P2, and P3) are mixed type inhibitors. The inhibition efficiency of organic compounds is temperature independent, but increases with the inhibitor concentration. Adsorption of inhibitor on the carbon steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined. On the other hand, and in order to determine the relationship between the molecular structure of these compounds and inhibition efficiency, quantum chemical parameters were calculated. The theoretically obtained results were found to be consistent with the experimental data.     

Synthesis and inhibition corrosion effect of two thiazole derivatives for carbon steel in 1 ​M HCl

Inhibition of C38 carbon steel corrosion by 4-methyl-3-phenyl-2(3H)-thiazolethione (TO1) and 4-methyl-2-(methylthio)-3- phenylthiazol-3-ium (ST1) in 1 ​M HCl was investigated by weight loss and electrochemical methods. All of the data obtained reveal that the two compounds act as good inhibitors in this media. At optimized concentration TO1 and ST1 showed the highest inhibition efficiency of 98.8% (2.10⁻⁴ ​M) and 93.86% (10⁻³ ​M) respectively. Polarization curves show that inhibitor molecules act as mixed type inhibitors. The impedance study showed that an increase in the concentration of the two inhibitors is accompanied by an increase in polarization resistance and a decrease in double layer capacitance. The Langmuir isotherm very well describes the adsorption of inhibitors to the surface of the corroding metal and the thermodynamic parameters showed that the adsorption of the two compounds was strong and chemical nature. X-ray photoelectron spectroscopy (XPS) confirms and describes the absorption of inhibitors under investigation on the metal surface.     

Argan hulls extract: green inhibitor of mild steel corrosion in 1?M HCl solution

Argan hulls extract (AHE) was tested as corrosion inhibitor for mild steel in 1?M HCl. Weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) revealed that inhibiting action increased with increasing concentration of the inhibitor. The highest efficiency 97.3% was obtained at 5?g/L AHE. There was good agreement between gravimetric and electrochemical methods (potentiodynamic polarization and EIS). Results obtained from EIS measurements were analyzed to model the corrosion-inhibition process by use of the appropriate equivalent circuit model; a constant phase element was used. Polarization measurements show also that AHE acts as good mixed inhibitor. AHE is adsorbed on the steel surface in accordance with a Langmuir isotherm adsorption model.     

Inhibitive effect by extract of Mentha rotundifolia leaves on the corrosion of steel in 1 M HCl solution

An extract of Mentha rotundifolia leaves (EMRL) was tested as a corrosion inhibitor of steel in 1 M HCl using electrochemical impedance spectroscopy, Tafel polarization methods, and weight loss measurements. The inhibition efficiency of the extract of Mentha rotundifolia leaves was calculated and compared. We note good agreement between these methods. The results obtained revealed that the inhibitor tested differently reduced the kinetics of the corrosion process of steel. Its efficiency increases with the concentration and attained 92.87 % at 35 %. The effect of temperature on the corrosion behavior of steel in 1 M HCl was also studied in the range 298 and 338 K. The thermodynamic data of activation were determined. Mentha rotundifolia extract is adsorbed on the steel surface according to a Langmuir adsorption model.     

Monte Carlo simulations of corrosion inhibition of mild steel in 0.5 M sulphuric acid by some green corrosion inhibitors

Atomistic modelling and simulations are becoming increasingly important in the field of corrosion inhibition. New research and development efforts and new possibilities for using computational chemistry in studying the behaviour of corrosion inhibitors on the metal surfaces are introduced. In this study, Monte Carlo simulations technique incorporating molecular mechanics and molecular dynamics were used to simulate the adsorption of methionine derivatives, namely l-methionine, l-methionine sulphoxide and l-methionine sulphone, on iron (110) surface in 0.5 M sulphuric acid. Adsorption energy as well as hydrogen bond length has been calculated. Results show that methionine derivatives have a very good inhibitive effect for corrosion of mild steel in 0.5 M sulphuric acid solution. Tafel polarisation studies have shown that methionine derivatives act as mixed-type inhibitors, and their inhibition mechanism is adsorption assisted by hydrogen bond formation. Impedance results indicate that the values of the constant phase element tend to decrease with increasing methionine derivatives concentrations due to the increase in the thickness of the electrical double layer. In addition, both polarisation resistance and inhibition efficiency E _i(%) tend to increase with increasing inhibitors concentrations due to the increase of the surface coverage, i.e., the decrease of the electrochemical active surface area. The quantum mechanical approach may well be able to foretell molecular structures that are better for corrosion inhibition.     

Role of hydroxyl group in cerium hydroxycinnamate on corrosion inhibition of mild steel in 0.6 M NaCl solution

The corrosion inhibition mechanism of cerium hydroxycinnamate compounds has been studied and compared as an effective corrosion inhibitor for steel in an aqueous 0.6?M NaCl solution. Surface analysis results showed that the surface of steel coupons exposed to solutions containing cerium hydroxycinnamate compounds has less signs of corrosion attack due to a formation of the protective film, while the surface of mild steel coupons exposed to 0.6?M chloride solution without inhibitor additions was severely corroded due to pitting. Electrochemical results performed a good inhibition performance and information of the formed protective deposit that hinders the electrochemical corrosion reactions with a dominance of anodic inhibition mechanism. The results also indicated that the addition of cerium hydroxycinnamate compounds to 0.6?M NaCl solution could mitigate electrochemical corrosion reactions, reduce protective and double layer CPE magnitudes, and improve protective and charge transfer resistances. Furthermore, cerium 2-hydroxycinnamate showed better efficient corrosion inhibitor in comparison with cerium 4-hydroxycinnamate for steel in aqueous media containing 0.6?M chloride ion.     

Inhibition of mild steel corrosion in 5 % HCl solution by 5-(2-hydroxyphenyl)-1,2,4-triazole-3-thione

A new corrosion inhibitor, namely 5-(2-hydroxyphenyl)-1,2,4-triazole-3-thione (5-HTT), has been synthesized and its influence on corrosion inhibition of mild steel in 5 % HCl solution has been studied using weight loss method and electrochemical measurements. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitor is of mixed type, and it inhibits the corrosion of the steel by blocking the active site of the metal. Changes in impedance parameters were indicative of adsorption of 5-HTT on the metal surface, leading to the formation of protective films. The degree of the surface coverage of the adsorbed inhibitors was determined by weight loss measurements, and it was found that the adsorption of these inhibitors on the mild steel surface obeys the Langmuir adsorption isotherm. The effect of the temperature on the corrosion behavior with addition of 5 × 10^?4 M of the inhibitor was studied in the temperature range 30–60 °C. The reactivity of this compound was analyzed through theoretical calculations based on density functional theory to explain the different efficiency of these compounds as a corrosion inhibitor.     

Aluminum corrosion prevention in 1.0 M HCl solution by cystosiera myrica extract: An experimental and biological study

Potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS), tests, mass loss (ML) and Hydrogen evolutions (HE) methods were used to examine the effects of the newly plant extracted compound (Cystosiera myrica). All these quantities exhibited that the effectiveness of inhibition increase with a rise in inhibitor concentration and with a rise in temperature. Polarization curves displayed that the inhibitor studied was an inhibitor of a mixed kind. Langmuir isotherm was attained for the adsorption of the inhibitor on the Aluminum surface. Thermodynamic parameters were determine and deduced such as activation enthalpy (ΔH*), activation entropy (ΔS*), adsorption equilibrium constant (K_ads) and free adsorption energy (G^o_ads) have been measured. UV/visible spectral, Attenuated Total Reflection Infra-Red (ATR-IR) and Atomic Force Microscopy (AFM) tested have observed the effect of this inhibitor on Al surface morphology. All other data approaches were compatible and in line with each other.     

Corrosion inhibition performance of 1,3,5-triazinyl urea derivatives as a corrosion inhibitor for mild steel in 1?N HCL

The inhibition effect of 1,3,5-triazinyl urea derivatives, viz. 1-(4-cyclohexyl amino)-6-(3,4-dimethoxy phenyl ethyl amino)-1,3,5-triazin-2-yl)-3-p-tolyurea (4-CADT) and 1-(4-chlorophenyl)-3-(4-(cyclohexyl amino)-6-(3,4-dimethoxy phenyl ethyl amino)-1,3,5-triazin-2-yl) urea (4-CCADT), were evaluated against mild steel (MS) corrosion in 1 N HCl solutions using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, and scanning electron microscopic studies. The losses in weights of MS samples have proved that both were efficient corrosion inhibitors. The mixed mode of inhibition was confirmed by electrochemical polarizations and the results of electrochemical impedance spectroscopy have shown the changes in the impedance parameters like charge transfer resistance and double-layer capacitance to confirm the strong adsorption on the MS surface inhibition of MS. The changes in concentrations of the inhibitors were due to the adsorption of the molecules evaluated leading to the formation of a protective layer on the surface of MS. The inhibition action of these compounds was assumed to occur via adsorption on the steel surface through the active centers contained in the molecules.     

Synthesis and evaluation of some quinoline Schiff bases as a corrosion inhibitor for mild steel in 1 N HCl

N-((2-chloroquinolin-3-yl)methylene)aniline (CQM) and N-((2-chloroquinolin-3-yl)methylene)-5-methylthiazol-2-amine (CQMA) were synthesized. The effect of CQM and CQMA have been investigated against mild steel (MS) in 1 N HCl solutions using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, UV–Vis spectroscopy and scanning electron microscopic studies. The losses in the weights of MS samples have proved that both CQM and CQMA are efficient inhibitors. The mixed mode of inhibition was confirmed by electrochemical polarizations. The adsorptions of these inhibitors are found to follow the Langmuir adsorption isotherm. CQM and CQMA adsorbs on the MS sample by chemisorptions.     

Mössbauer study of the corrosion of mild steel due to prolonged immersion in deionized water

The corrosion of mild steel as a result of 3 years of immersion in deionized water, using Mössbauer results, indicates that -FeOOH, -FeOOH and Fe₃O₄ are formed as corrosion products. This study shows that purified water will produce -FeOOH only when the exposure time is long. It is proposed that ferrihydrite, which is formed as an intermediate corrosion product, is converted to -FeOOH, which in turn is converted to -FeOOH and Fe₃O₄.     

Synergistic effect of AM-4VP-9 copolymer and iodide ion on corrosion inhibition of mild steel in 1 M H2SO4

The effect of iodide ions on the corrosion inhibition of mild steel in 1 M sulfuric acid in the presence of poly(acrylamide-co-4-vinylpyridine) copolymer abbreviated by (AM-4VP-9) was studied by weight loss measurements and electrochemical techniques (impedance spectroscopy and polarisation curves) at 18 °C. The results obtained showed that the inhibition efficiency increased with increasing copolymer concentration. It was also found that the inhibition efficiency increased with the addition of potassium iodide (KI) to the copolymer. A synergistic effect was observed between the AM-4VP-9 copolymer and KI. On the other hand, it was found that the inhibiting effect of the system (AM-4VP-9 + KI) increased with increasing immersion time. Polarisation curves indicate that (AM-4VP-9) copolymer act as mixed inhibitors. EIS measurements show an increase of the transfer resistance with the inhibitor concentration.     

The effect of some triazole derivatives as inhibitors for the corrosion of mild steel in 5 % hydrochloric acid

Corrosion inhibition by triazole derivatives (n-MMT) on mild steel in 5 % hydrochloric acid (HCl) solutions has been investigated by weight loss and electrochemical methods. The results obtained revealed that these compounds performed excellently as corrosion inhibitors for mild steel in HCl solution. Potentiodynamic polarization studies showed that they suppressed both the anodic and cathodic processes and inhibited the corrosion of mild steel by blocking the active site of the metal. The effect of temperature on the corrosion behavior of mild steel in 5 % HCl with the addition of different concentrations of the inhibitors was studied in the temperature range from 303 to 333 K. The associated activation corrosion and free adsorption energies were determined. The adsorption of these compounds on the mild steel surface obeys the Langmuir adsorption isotherm. The effect of molecular structure on the inhibition efficiency has been investigated by quantum chemical calculations. The electronic properties of inhibitors were calculated and are discussed.     

Inhibition effect of 1,3,5-tri-p-tolyl-1,3,5-triazene on the corrosion of brass in 0.5 M HCl solution

1,3,5-tri-p-tolyl-1,3,5-triazene was investigated as a corrosion inhibitor for brass in 0.5 M HCl solution using weight loss, potentiodynamic polarization, linear polarization resistance and electrochemical impedance spectroscopy. Data obtained from these methods showed average inhibition efficiency (76 %) at optimum concentration. The adsorption of the inhibitor on the brass surface follows the Frumkin adsorption isotherm.     

Study of the inhibiting effect of a quaternary ammonium surfactants mixture synthesized from petroleum fraction (reformate) against the carbon steel corrosion in HCl 1 M

Quaternary ammonium cationic surfactants were synthesized from reformate, a liquid mixture of hydrocarbons (aromatics, naphthenes and paraffins), via chloromethylation/quaternization sequences. The petroleum surfactants thus obtained were evaluated as corrosion inhibitors for carbon steel in 1 M HCl, by gravimetry, potentiodynamic polarization and electrochemical impedance spectroscopy. The corrosion inhibiting efficiency was assessed as functions of surfactant concentration. The results showed that the inhibiting efficiency increased with surfactant concentration; its optimal value of 70 % was for a surfactant concentration of 320 mg/L at 25 °C. Potentiodynamic polarization measurements showed that the mixture acts as a mixed type inhibitor. The corrosion inhibiting mechanism is thought to proceed via an adsorption of the surfactant molecules on the steel surface, generating a film and hindering the active sites. Our experimental adsorption data were found to obey the Langmuir adsorption isotherm. SEM images of the treated specimens, revealing the likely formation of a protective film, demonstrated the inhibiting capacity of the petroleum quaternary ammonium surfactants against the carbon steel corrosion.     

Mössbauer spectroscopy of corrosion products of mild steel due to microbiologically influenced corrosion

Corrosion products of mild steel exposed to four different cultures of sulfur reducing bacteria (SRB) grown in a synthetic medium have been studied by transmission Mössbauer spectroscopy (TMS). Cultures of SRB studied are two hydrogenase positive strains,Desulfovibrio desulfuricans (DD) andDesulfovibrio vulgaris (DV) and two hydrogenase negative strainsDesulfotomaculum orientis orientis (DO) andDesulfotomaculum nigrificans (DN). The corrosion products generated on the coupons as well as in the broth were studied. In all the cases, the corrosion products removed from coupons showed the presence of green rust 2 (GR2), ferrous sulfides, γ-FeOOH and superparamagnetic (SPM) α-FeOOH in different proportions. The corrosion products from the broth showed a symmetrical central doublet, which indicates the presence of γ-FeOOH and SPM α-FeOOH along with ferrous sulfides. The corrosion products from coupons suspended in sewage water also showed the presence of GR 2 and ferrous sulfides together with oxyhydroxides. FTIR spectrum supports the presence of these phases in corrosion products. The formation of GR 2 on coupons seems to be the first step for the SRB induced corrosion. The corrosion rate has been found in the order of DO>DN>DV>DD.     

Corrosion inhibition of steel in molar HCl by triphenyltin2–thiophene carboxylate

The effect of triphenyltin2–thiophene carboxylate (TTC) on the corrosion of steel in hydrochloric acid medium was studied using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor to reach 97% at 10^?3 M. Polarisation study shows that TTC is an efficient inhibitor and acts as a mixed-type inhibitor. EIS results indicate the increase of resistance transfer (R_T) and the decrease of double layer capacitance (C_dl) with TTC concentration. Triphenyltin2–thiophene carboxylate molecules lead to the formation of a protective layer on the surface of steel. The inhibitor is adsorbed on the steel surface according to Langmuir isotherm.     

Poly (vinyl alcohol – aniline) water soluble composite as corrosion inhibitor for mild steel in 1 M HCl

Poly (vinyl alcohol – aniline) PVAA composite was tested for its performance in protecting mild steel MS against corrosion in 1 M HCl. The inhibitive parameters were evaluated by means of weight loss, electrochemical polarization and impedance methods. Results indicated that the addition of PVAA to the acid reduces the corrosion of the metal. Inhibition efficiency increases with increase in inhibitor concentration. The results further revealed that PVAA at a concentration of 2000 ppm furnishes a maximum of 92% inhibition efficiency. Thermodynamic parameters such as free energy of adsorption, heat of adsorption, etc., had been evaluated from temperature studies. The adsorption of PVAA followed Langmuir and Temkin adsorption isotherms. Polarization curves revealed that PVAA is a mixed inhibitor.