Inhibition of steel corrosion in 2 M H3PO4 by artemisia oil

Artemisia oil (Ar) is extracted from artemisia herba alba collected in Ain es-sefra-Algeria, and tested as corrosion inhibitor of steel in 2 M H₃PO₄ using weight loss measurements, electrochemical polarisation and EIS methods. The naturally oil reduces the corrosion rate. The inhibition efficiency was found to increase with oil content to attain 79% at 6 g/l. Ar acts as a cathodic inhibitor. The effect of temperature on the corrosion behaviour of steel indicates that inhibition efficiency of the natural substance decreases with the rise of temperature. The adsorption isotherm of natural product on the steel has been determined.     

Electrochemical, theoretical and XPS studies of 2-mercapto-1-methylimidazole adsorption on carbon steel in 1 M HClO4

The inhibition of the corrosion of carbon steel in 1 M HClO₄ by 2-mercapto-1-methylimidazole (MMI) 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 behaviour with addition of different concentrations of MMI was studied in the temperature range 30-60 °C. Polarization curves reveal that MMI is a mixed type inhibitor. The inhibition efficiency of MMI is temperature independent but increases with the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, R_t, and double-layer capacitance, C_dl) were indicative of adsorption of MMI on the metal surface, leading to the formation of a protective film. Adsorption of MMI on the carbon steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined. The X-ray photoelectron spectroscopy (XPS) of the carbon steel indicated that MMI is chemically adsorbed on the steel surface. Moreover, the electronic properties such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels and molecular orbital densities were calculated.     

Investigation of the inhibitive effect of triphenyltin 2-thiophene carboxylate on corrosion of steel in 2 M H3PO4 solutions

A new organic compound was synthesised and tested as corrosion inhibitor of steel in phosphoric acid medium using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that the inhibitor studied is a good cathodic inhibitor. EIS results show that the change in the impedance parameters (R_T and C_dl) with concentration of triphenyltin 2-thiophene carboxylate (TTC) is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of steel. The effect of the temperature on the steel corrosion in 2 M H₃PO₄ and with addition of various concentrations of TTC in the range of temperature 298-348 K was studied. The associated apparent activation corrosion energy has been determined.     

Synergistic effect between 4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steel in 0.5 M sulfuric acid

The corrosion inhibition of 1-(2-pyridylazo)-2-naphthol (PAR) on the corrosion of cold rolled steel in 0.5 M sulfuric acid (H₂SO₄) was studied using weight loss method and potentiodynamic polarization method. Results obtained revealed that together with chloride ion, PAR is an effective corrosion inhibitor for steel corrosion in sulfuric acid. It was found that for steel corrosion inhibition in the presence of single PAR in sulfuric acid the Temkin adsorption isotherm may be used to explain the adsorption phenomenon. For the mixture of PAR and NaCl used as corrosion inhibitor, however, the Langmuir adsorption isotherm can be used to satisfactorily elucidate the adsorption of mixture of PAR and NaCl. Potentiodynamic polarization studies showed that single PAR mainly acts as a cathodic inhibitor for the corrosion of steel in 0.5 M sulfuric acid. The mixture of PAR and chloride ion, however, acts as a mixed type inhibitor that mainly inhibits cathodic reaction of the steel corrosion in sulfuric acid. By means of electrochemical polarization tests, a desorption potential at ca. −370 mV was observed for the adsorption of mixture of PAR and chloride ion, when potential reaches this value, adsorbed inhibitor molecule heavily departs from the steel surface. For the mixture of PAR and chloride ion, thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 30 to 45 °C, the kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The most suitable range of inhibitor concentration was discussed. The inhibitive action was satisfactorily explained by using both thermodynamic and kinetic models. Synergism between chloride ion and PAR was proposed. The results obtained from weight loss and potentiodynamic polarization were in good agreement.     

Berberine as a natural source inhibitor for mild steel in 1 M H2SO4

Berberine was abstracted from coptis chinensis and its inhibition efficiency on corrosion of mild steel in 1 M H₂SO₄ was investigated through weight loss experiment, electrochemical techniques and scanning electronic microscope (SEM) with energy disperse spectrometer (EDS). The weight loss results showed that berberine is an excellent corrosion inhibitor for mild steel immersed in 1 M H₂SO₄. Potentiodynamic curves suggested that berberine suppressed both cathodic and anodic processes for its concentrations higher than 1.0 × 10⁻⁴ M and mainly cathodic reaction was suppressed for lower concentrations. The Nyquist diagrams of impedance for mild steel in 1 M H₂SO₄ containing berberine with different concentrations showed one capacitive loop, and the polarization resistance increased with the inhibitor concentration rising. A good fit to Flory-Huggins isotherm was obtained between surface coverage degree and inhibitor concentration. The surface morphology and EDS analysis for mild steel specimens in sulfuric acid in the absence and presence of the inhibitor also proved the results obtained by the weight loss and electrochemical experiments. The correlation of inhibition effect and molecular structure of berberine was then discussed by quantum chemistry study.     

Enhanced corrosion resistance of mild steel in molar hydrochloric acid solution by 1,4-bis(2-pyridyl)-5H-pyridazino[4,5-b]indole: Electrochemical, theoretical and XPS studies

The inhibition effect of the new pyridazine derivative, namely 1,4-bis(2-pyridyl)-5H-pyridazino[4,5-b]indole (PPI) against mild steel corrosion in 1 M HCl solutions was evaluated using weigh loss and electrochemical techniques (potentiodynamic polarisation curves and impedance spectroscopy). The experimental results suggest that PPI is a good corrosion inhibitor and the inhibition efficiency increased with the increase of PPI concentration, while the adsorption followed the Langmuir isotherm. X-ray photoelectron spectroscopy (XPS) and theoretical calculation of electronic density were carried out to establish the mechanism of corrosion inhibition of mild steel with PPI in 1 M HCl medium. The inhibition action of this compound was, assumed to occur via adsorption on the steel surface through the active centres contained of the molecule. The corrosion inhibition is due to the formation of a chemisorbed film on the steel surface.     

The inhibition of corrosion of mild steel in 0.5 M sulfuric acid solution in the presence of benzyl triphenyl phosphonium bromide

Benzyl triphenyl phosphonium bromide (BTPPB) has been evaluated as a corrosion inhibitor for mild steel in aerated 0.5 M sulfuric acid solution by galvanostatic polarization and potentiostatic polarization methods. The effect of BTPPB on the corrosion current is measured at various temperatures and concentrations. The inhibitor efficiencies, effective activation energies and heat of adsorption have been calculated. The inhibition efficiency increases with increase in inhibitor concentration to reach 99.3% for 10⁻² M. The nature of adsorption of BTPPB on the metal surface has also been examined. Probable mode of adsorption on the metal surface has been proposed using infrared spectroscopic studies. The electrochemical results have also been supplemented by surface morphological studies and quantum chemical analysis.     

Understanding the adsorption of 4H-1,2,4-triazole derivatives on mild steel surface in molar hydrochloric acid

This study examines the use of some 4H-triazole derivatives, namely 3,5-diphenyl-4H-1,2,4-triazole (DHT), 3,5-bis(4-pyridyl)-4H-1,2,4-triazole (4-PHT) and 3,5-bis(4-methyltiophenyl)-4H-1,2,4-triazole (4-MTHT) for corrosion and dissolution protection of mild steel in normal hydrochloric acid solution. The inhibiting efficiency of the different additives is evaluated by means of weight loss and electrochemical techniques such as ac impedance measurements and polarisation curves. The experimental results obtained reveal that 4-MTHT is the best effective inhibitor and the inhibition efficiency is found to be in the following order: 4-MTHT > 4-PHT > DHT. The variation in inhibitive efficiency mainly depends on the type and nature of the substituents present in the inhibitor molecule. Polarisation curves show that theses triazoles are mixed-type inhibitors in 1 M HCl. The inhibition efficiency increases with 4H-triazole derivatives concentration and attains the maximum value of 99.6% in the case of 4-MTHT at 5 × 10⁻⁴ M. The results obtained from weight loss electrochemical studies were in reasonable agreement. The adsorption of 4H-triazole derivatives on the steel surface obeys to the Langmuir isotherm model. The thermodynamic data of adsorption and activation are determined and discussed. The fundamental thermodynamic functions were used to glean important information about the 4H-triazoles inhibitory behaviour. Molecular modeling was used to get better insight, about structural and electronic effects in relation to the inhibition efficiencies.     

Corrosion inhibition of steel in 0.5 M H2SO4 by [(2-pyridin-4-ylethyl)thio]acetic acid

The influence of [(2-pyridin-4-ylethyl)thio]acetic acid (P1) and pyridine (P2) on the corrosion inhibition of steel in sulphuric acid solution is studied using weight loss, potentiodynamic polarisation and linear polarisation resistance (R_p) and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that P1 is the best inhibitor and its inhibition efficiency (E%) increases with the increase of concentration. The highest E% of 82% is observed at 5 × 10⁻³ M. Potentiodynamic polarisation studies clearly reveal that P1 acts as a mixed inhibitor. The inhibitor studied reduces the corrosion rates. E% values obtained from various methods used are in good agreement. Adsorption of P1 on steel surface obeys to Langmuir adsorption isotherm. Effect of temperature indicates that E% decreases with temperature between 298 and 353 K.     

Electrochemical and quantum chemical studies of some Schiff bases on the corrosion of steel in H2SO4 solution

The efficiency, as steel-corrosion inhibitors in 0.1 M and 1 M H₂SO₄, of two Schiff bases, 2-{[(4-methoxyphenyl)imino]methyl}phenol and 1-{[(4-methoxyphenyl)imino]methyl}-2-naphthol, (abbreviated SB-1 and SB-2, respectively) was investigated by Tafel extrapolation and linear polarization methods. Corrosion parameters and adsorption isotherms were determined from current-potential curves. It was found that the percent inhibition efficiencies (η%) and surface coverage (θ) increase with an increases in the concentrations of inhibitors. The results showed that these compounds act as good corrosion inhibitors especially at high concentrations. The adsorption of used compounds on the steel surface obeys Langmuir's isotherm. Obvious correlation was found between corrosion inhibition efficiency and quantum chemical parameters obtained by B3LYP/6-31g(d) method. The obtained theoretical results have been compared with the experimental findings.     

An electroactive co-polymer as corrosion inhibitor for steel in sulphuric acid medium

The corrosion behavior of mild steel in sulphuric acid solution containing various concentrations of a co-polymer formed between maleic anhydride and N-vinyl-2-pyrrolidone (VPMA) was investigated using weight-loss, polarization and electrochemical impedance techniques. The polymer acts as an effective corrosion inhibitor for steel in sulphuric acid medium. The inhibition process is attributed to the formation of an adsorbed film of co-polymer on the metal surface which protects the metal against corrosion. Scanning electron microscopy (SEM) studies of the metal surfaces confirmed the existence of an adsorbed film. The adsorption followed the Langmuir isotherm. The protection efficiency increased with increase in inhibitor concentration and decreased with increase in temperature and acid concentration. The thermodynamic functions of the adsorption and dissolution processes were evaluated.     

Tween-40 as corrosion inhibitor for cold rolled steel in sulphuric acid: Weight loss study, electrochemical characterization, and AFM

The inhibition action of a non-ionic surfactant of tween-40 on the corrosion of cold rolled steel (CRS) in 0.5-7.0 M sulphuric acid (H₂SO₄) was studied by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the surface conditions. The inhibition efficiency increases with the tween-40 concentration, while decreases with the sulphuric acid concentration. The adsorption of inhibitor on the cold rolled steel surface obeys the Langmuir adsorption isotherm equation. Effect of immersion time was studied and discussed. The effect of temperature on the corrosion behavior of cold rolled steel was also studied at four temperatures ranging from 30 to 60 °C, the thermodynamic parameters such as adsorption heat, adsorption free energy and adsorption entropy were calculated. A kinetic study of cold rolled steel in uninhibited and inhibited acid was also discussed. The kinetic parameters such as apparent activation energy, pre-exponential factor, rate constant, and reaction constant were calculated for the reactions of corrosion. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic parameters. Polarization curves show that tween-40 is a cathodic-type inhibitor in sulphuric acid. The results obtained from weight loss and potentiodynamic polarization are in good agreement, and the tween-40 inhibition action could also be evidenced by surface AFM images.     

Synergistic effect between 4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steel in 1.0 M phosphoric acid

The synergistic inhibition between 4-(2-pyridylazo) resorcin (PAR) and chloride ion on the corrosion of cold rolled steel in 1.0 M phosphoric acid was studied using weight loss and potentiodynamic polarization method. Results obtained revealed that single PAR is not an effective inhibitor for steel corrosion in phosphoric acid, but in the presence of chloride ion, PAR may act as a good inhibitor due to the synergism. It is found that the adsorption of PAR accords with the Langmuir adsorption isotherm in the absence and presence of chloride ion. Potentiodynamic polarization studies show that PAR is an anodic inhibitor for steel in 1.0 M phosphoric acid, and with addition of chloride ion PAR acts as a mixed type inhibitor. The experimental temperature ranges from 30 to 45 °C. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The inhibitive action was satisfactorily explained by using kinetic models.     

The corrosion inhibition and gas evolution studies of some surfactants and citric acid on lead alloy in 12.5 M H2SO4 solution

The inhibition action of the citric acid and three surfactants: sodium dodecyl sulfate (SDS), t-octyl phenoxy polyethoxyethanol (Triton X-100), sodium dodecyl benzene sulphonate (SDBS) on the corrosion behavior and gas evolution of Pb-Sb-As-Se was investigated in 12.5 M H₂SO₄ solution with linear sweep polarization, cyclic voltammetry and weight loss measurements methods. The results drawn from different techniques are comparable. It was found that these surfactants and citric acid act as good inhibitors for the corrosion of lead alloy in H₂SO₄ solution. SDS inhibited most effectively the lead alloy corrosion among the three surfactants and citric acid. The inhibition efficiency for the inhibitors decreases in the order: SDS > SDBS > Triton X-100 > citric acid > blank. The inhibition efficiency increases with rising of the inhibitor concentration. In this work, the effect of the inhibitors on hydrogen and oxygen evolution was studied. In addition, it was found that the adsorption of used inhibitors on lead alloy surface follows Langmuir isotherm.     

Synergistic inhibition effect of 2-mercaptobenzothiazole and Tween-80 on the corrosion of brass in NaCl solution

The corrosion inhibition of brass in 0.2 M NaCl in the presence of 2-mercaptobenzothiazole (MBT) and polyoxyethylene sorbitan monooleate (Tween-80) has been investigated using potentiodynamic polarization, X-ray photoelectron spectroscopy and inductively coupled plasma analysis. Analysis of the results revealed that the addition of MBT and Tween-80 inhibits the corrosion of brass in 0.2 M NaCl. Potentiodynamic polarization measurements showed that MBT acts as a mixed-type inhibitor and Tween-80 as an anodic inhibitor. Corrosion inhibition occurs through adsorption of the inhibitor on brass surface without modifying the corrosion mechanism. The adsorption of MBT and Tween-80 both follow Langmuir adsorption isotherm. Potentiodynamic polarization results suggested that the mixture of MBT and Tween-80 acts as a mixed-type inhibitor. Inhibition efficiency of 79.0 and 62.5% were obtained in the presence of optimum concentration of MBT and Tween-80, respectively. The addition of the mixture of MBT and Tween-80 enhanced the inhibition efficiency to 94.0% and showed a synergism of inhibition. XPS analysis indicated that MBT adsorbed on brass surface along with Tween-80 in the presence of the mixture of MBT and Tween-80. The results of solution analysis using ICP showed that the mixture of MBT and Tween-80 effectively controlled the dezincification of brass.     

Establishment of equivalent circuits from electrochemical impedance spectroscopy study of corrosion inhibition of steel by pyrazine in sulphuric acidic solution

This paper describes the use of the electrochemical impedance spectroscopy technique (EIS) in order to study the corrosion inhibition process of steel in 0.5 M H₂SO₄ solution at the open circuit potential (OCP). Diethyl pyrazine-2,3-dicarboxylate (Prz) as a non-ionic surfactant (NS) inhibitor has been examined. The Nyquist diagrams consisted of a capacitive semicircle at high frequencies followed by a well-defined inductive loop at low frequency values. The impedance measurements were interpreted according to suitable equivalent circuits. The results obtained showed that the Prz is a good inhibitor. The inhibition efficiency increases with an increase in the surfactant concentration to attain 80% at the 5 × 10⁻³M. Prz is adsorbed on the steel surface according to a Langmuir isotherm adsorption model.     

Enhanced corrosion resistance of mild steel in normal sulfuric acid medium by 2,5-bis(n-thienyl)-1,3,4-thiadiazoles: Electrochemical, X-ray photoelectron spectroscopy and theoretical studies

The inhibitive action of some thiadiazole derivatives, namely 2,5-bis(2-thienyl)-1,3,4-thiadiazole (2-TTH) and 2,5-bis(3-thienyl)-1,3,4-thiadiazole (3-TTH) against the corrosion of mild steel in 0.5 M H₂SO₄ solution has been investigated using weight loss measurements, Tafel polarisation and electrochemical impedance spectroscopy (EIS) techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution. The protection efficiency increased with increasing inhibitors concentration and the ability of the molecule to adsorb on the steel surface was dependent on the position of the sulphur atom on the thienyl substituent. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. Potentiodynamic polarisation studies clearly showed that 2-TTH and 3-TTH acted as mixed inhibitors. Adsorption of these inhibitors on steel surface obeyed to Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal sulphuric solution by n-TTH is due to the formation of a chemisorbed film on the steel surface. Molecular modelling was used to gain some insight, about structural and electronic effects in relation to the inhibiting efficiencies.     

The inhibited effect of some tetrazolic compounds towards the corrosion of brass in nitric acid solution

The effect of the addition of some tetrazolic type organic compounds: 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMT), 1,2,3,4-tetrazole (TTZ), 5-amino-1,2,3,4-tetrazole (AT) and 1-phenyl-1,2,3,4-tetrazole (PT) on the corrosion of brass in nitric acid is studied by weight loss, polarisation and electrochemical impedance spectroscopy (EIS) measurements. The explored methods gave almost similar results. Results obtained reveal that PMT is the best inhibitor and the inhibition efficiency (E%) follows the sequence: PMT > PT > AT > TTZ. Polarization measurements also indicated that tetrazoles acted as mixed-type inhibitors without changing the mechanism of the hydrogen evolution reaction. Partial π-charge on atoms has been calculated. Correlation between the highest occupied molecular orbital energy E_HOMO and inhibition efficiencies was sought. The adsorption of PMT on the brass surface followed the Langmuir isotherm. Effect of temperature is also studied in the (25-50 °C) range.     

Corrosion inhibition of steel in sulphuric acid by pyrrolidine derivatives

Novel corrosion inhibitors, namely 1-{2-[(2-hydroxyethyl)thio]ethyl}pyrrolidin-2-one (P5) and {[2-(2-oxopyrrolidin-1-yl)ethyl]thio}acetic acid (P4), were synthesised and tested as corrosion inhibitors for steel in 0.5 M H₂SO₄. The effects of P4 and P5 are also compared to their initial reactants 1-vinylpyrrolidin-2-one (P1), 2-mercaptoethanol (P2) and mercaptoacetic acid (P3). The study was carried out by weight loss measurements, potentiodynamic polarisation, linear polarisation resistance (R_p) and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency increases with the concentration of P5 to attain 89% at 5 × 10⁻³ M. We note good agreement between the various methods explored. Polarisation measurements show also that the pyrrolidones act essentially as cathodic inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface is an activating mechanism. P4 and P5 adsorb on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied in the 298-353 K range. Efficiency is explained by the theoretical studies.     

Inhibiting effects of some oxadiazole derivatives on the corrosion of mild steel in perchloric acid solution

The efficiency of 3,5-bis(n-pyridyl)-1,3,4-oxadiazole (n-POX, n = 1, 2, 3), as corrosion inhibitors for mild steel in 1 M perchloric acid (HClO₄) have been determined by weight loss measurements and electrochemical studies. The results show that these inhibitors revealed a good corrosion inhibition even at very low concentrations. Comparison of results among those obtained by the studied oxadiazoles shows that 3-POX was the best inhibitor. Polarisation curves indicate that n-pyridyl substituted-1,3,4-oxadiazoles are mixed type inhibitors in 1 M HClO₄. The adsorption of these inhibitors follows a Langmuir isotherm model. The electronic properties of n-POX, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR).