The use of Euphorbia falcata extract as eco-friendly corrosion inhibitor of carbon steel in hydrochloric acid solution

Euphorbia falcata L. extract (EFE) was investigated as eco-friendly corrosion inhibitor of carbon steel in 1 M HCl using gravimetric, ac impedance, polarization and scanning electron microscopy (SEM) techniques. The experimental results show that EFE is good corrosion inhibitor and the protection efficiency is increased with the EEF concentration. The results obtained from weight loss and ac impedance studies were in reasonable agreement. Impedance experimental data revealed a frequency distribution of the capacitance, simulated as constant phase element. Polarization curves indicated that EFE is a mixed inhibitor. The corrosion inhibition was assumed to occur via adsorption of EFE molecules on the metal surface. The adsorption of the E. falcata extract was well described by the Langmuir adsorption isotherm. The calculated ΔG_ads^o value showed that the corrosion inhibition of the carbon steel in 1 M HCl is mainly controlled by a physisorption process.     

Cefalexin drug: A new and efficient corrosion inhibitor for mild steel in hydrochloric acid solution

Corrosion inhibition of mild steel in 1N HCl by cefalexin has been studied by electrochemical and weight loss measurements. The inhibitor showed increase in inhibition efficiency with increase in inhibitor concentration up to optimum concentration 400 ppm. Potentiodynamic polarization suggests that it is a mixed type of inhibitor. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. Thermodynamic parameters were calculated to investigate mechanism of inhibition. AFM is used to investigate the surface morphology of the uninhibited and inhibited mild steel.     

Tributylamine as corrosion inhibitor for mild steel in hydrochloric acid

The corrosion inhibition of mild steel in 2 M hydrochloric acid solution by tributylamine has been investigated using the impedance technique. Tributylamine was studied in concentrations from 5 × 10^–4 M to 1 M at a temperature of 298 K. The inhibitor mechanism was treated as a substitutional adsorption process according to Flory-Huggins, Dhar-Flory-Huggins and Bockris-Swinkels isotherms. The best approach was obtained using the latter. A structural parameter, the projected molecular area of tributylamine, was calculated to elucidate inhibitor orientation in the adsorption process.     

Investigation of inhibition effect of rhodanine-N-acetic acid on mild steel corrosion in HCl solution

Corrosion inhibition effect of rhodanine-N-acetic acid (R-NA) on mild steel (MS) corrosion in 0.1 M HCl solution was investigated. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) as well as hydrogen gas evolution (VH₂−t) and the change of open circuit potential as a function of immersion time (E_ocp − t) were used. The MS surfaces exposed to 0.1 M HCl solution in the absence and presence of inhibitor were examined by scanning electron microscopy (SEM). The thermodynamic parameters of adsorption were calculated and discussed. In order to gain more information about the adsorption mechanism, the EIS technique was used to evaluate the potential of zero charge (PZC) and a mechanism of adsorption process was proposed. It was found that, R-NA is a good corrosion inhibitor for the MS corrosion in 0.1 M HCl solution. The inhibition efficiency increased with increasing inhibitor concentration and reached 98% at 1.0 × 10⁻² M R-NA. The high inhibition efficiency was related to adsorption of R-NA on steel surface. Surface SEM images showed a good surface coverage of inhibitor on the metal surface.     

Adsorption and corrosion inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base on mild steel

In this study, the inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base (MTMP) on mild steel corrosion in 0.5 M HCl solution was studied. For this aim, electrochemical techniques such as potentiodynamic polarization curves, weight loss (WL), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) were used. It was shown that, the MTMP Schiff base has remarkable inhibition efficiency on the corrosion of mild steel in 0.5 M HCl solution. Polarization measurements indicated that, the studied inhibitor acts as mixed type corrosion inhibitor with predominantly control of cathodic reaction. The inhibition efficiency depends on the concentration of inhibitor and reaches 97% at 1.0 mM MTMP. The remarkable inhibition efficiency of MTMP was discussed in terms of blocking of electrode surface by adsorption of inhibitor molecules through active centers. The adsorption of MTMP molecules on the mild steel surface obeys Langmuir adsorption isotherm.     

Green approach to corrosion inhibition of mild steel in hydrochloric acid and sulphuric acid solutions by the extract of Murraya koenigii leaves

The inhibition of the corrosion of mild steel in hydrochloric acid and sulphuric acid solutions by the extract of Murraya koenigii leaves has been studied using weight loss, electrochemical impedance spectroscopy (EIS), linear polarization and potentiodynamic polarization techniques. Inhibition was found to increase with increasing concentration of the leaves extract. The effect of temperature, immersion time and acid concentration on the corrosion behavior of mild steel in 1 M HCl and 0.5 M H₂SO₄ with addition of extract was also studied. The inhibition was assumed to occur via adsorption of the inhibitor molecules on the metal surface. The adsorption of the extract on the mild steel surface obeys the Langmuir adsorption isotherm. The activation energy as well as other thermodynamic parameters (Q, ΔH^*, and ΔS^*) for the inhibition process was calculated. These thermodynamic parameters show strong interaction between inhibitor and mild steel surface. The results obtained show that the extract of the leaves of M. koenigii could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric and sulphuric acid media.     

Poly(o-phenylenediamine) as an inhibitor of mild steel corrosion in HCl solution

The inhibition properties of the electro-prepared P(o-phenylenediamine), P(oPD), on the corrosion rate of mild steel (MS) in HCl solutions have been investigated under different experimental conditions using weight loss and potentiodynamic polarization techniques. The data obtained from the two techniques are comparable and showed that the presence of P(oPD) in the acid solutions suppresses the corrosion rate of MS indicating that the polymer acts as corrosion inhibitor. The inhibition efficiency (IE%) of the polymer enhances with increasing its concentration and decreases with an increase in temperature. The inhibition occurs through adsorption and formation of barrier film on the metal surface which separates the metal from direct contact with the corrosive medium and hence protects the metal against the corrosion. Langmuir isotherm fits well with the experimental data. Thermodynamic parameters for both dissolution and adsorption processes were determined.     

Poly(aniline-formaldehyde): A new and effective corrosion inhibitor for mild steel in hydrochloric acid

In recent years, polyanilines have emerged as efficient class of corrosion inhibitors for mild steel in acidic media. The corrosion inhibition of poly(aniline-formaldehyde) on mild steel in 1.0N HCl has been evaluated by potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy and weight loss measurements. Results obtained show that poly(aniline-formaldehyde) is a mixed inhibitor and it inhibits mild steel corrosion through adsorption mechanism. It showed >90% inhibition efficiency at 10 ppm. AFM clearly reveals that surface roughness of inhibited mild steel sample is less than uninhibited mild steel.     

Streptomycin: A commercially available drug as corrosion inhibitor for mild steel in hydrochloric acid solution

The corrosion inhibition of mild steel in 1 M HCl solution by Streptomycin has been studied by Tafel polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurement. The inhibitor showed 88.5% inhibition efficiency at optimum concentration 500 ppm. Results obtained revealed that inhibition occurs through adsorption of the drug on metal surface without modifying the mechanism of corrosion process. Potentiodynamic polarization studies suggest that it is a mixed type of inhibitor. Electrochemical impedance spectroscopy techniques were also used to investigate the mechanism of corrosion inhibition.     

The study of the inhibitory properties of benzoin, benzil, benzoin-(4-phenylthiosemicarbazone) and benzil-(4-phenylthiosemicarbazone) on the corrosion of mild steel in hydrochloric acid

The effects of benzoin (BN), benzil (BL), benzoin-(4-phenylthiosemicarbazone) (BN4PTSC) and benzil-(4-phenylthiosemicarbazone) (BL4PTSC) on the corrosion of mild steel in hydrochloric acid have been studied. Weight loss and hydrogen evolution measurements reveal that BN exhibit a higher maximum inhibition efficiency than BN4PTSC, BL and BL4PTSC. Generally, inhibition was found to increase with increase in inhibitor concentration and temperature. Chemical adsorption mechanism has been proposed for the inhibitors and the difference in the inhibition behaviour of the compounds has been explained in terms of the solubility of the compounds as well as the strength of the inhibitor–metal bond.     

The inhibition of mild steel corrosion in 1 M hydrochloric acid solutions by triazole derivative

The title compound 1-(4,5-dihydro-3-phenylpyridine-1-yl)-2-(1H-1,2,4-triazole-1-yl)ethyl ketone (DTE) was synthesized and its inhibiting action on the corrosion of mild steel in 1 M hydrochloric acid solutions was investigated by means of weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscope (SEM). Results obtained revealed that DTE performed excellently as a corrosion inhibitor for mild steel in 1 M hydrochloric acid media and its efficiency attains more than 90.9% at 1.0 × 10^− 3 M at 298 K. Polarization curves indicated that the inhibitor behave mainly as mixed-type inhibitor. EIS showed that the charge transfer controls the corrosion process in the uninhibited and inhibited solutions. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm. And the values of the free energy of adsorption ΔG_ads indicated that the adsorption of DTE molecule was a spontaneous process and was typical of chemisorption.     

Effects of 5-(3-aminophenyl)-tetrazole on the inhibition of unalloyed iron corrosion in aerated 3.5% sodium chloride solutions as a corrosion inhibitor

The effects of 5-(3-aminophenyl)-tetrazole (APT) on the inhibition of unalloyed iron corrosion in aerated 3.5% NaCl solutions as a corrosion inhibitor have been studied using open circuit potential (OCP), cyclic potentiodynamic polarization (CPP), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. The inhibited iron surface was characterized by scanning electron spectroscopy (SEM) and energy dispersive X-ray (EDS) investigations. The OCP showed positive shifts of potential in the presence of APT and the increase of its concentration. CPP and CA measurements indicated that APT molecules decrease the pitting and uniform corrosions through decreasing the pitting and absolute currents, and corrosion rate as well as shifting the corrosion and pitting potentials of iron towards the noble values. EIS plots revealed that APT increases the surface and polarization resistances of iron. SEM/EDS investigations proved that the inhibition of iron corrosion in NaCl containing APT solutions is achieved by the adsorption of APT molecules onto iron to preclude the dissolution process by blocking the active sites on its surface.     

The inhibition of 4-(2′-amino-5′-methylphenylazo) antipyrine on corrosion of mild steel in HCl solution

The effect of 4-(2′-amino-5′-methylphenylazo) antipyrine (AMPA) on the corrosion of mild steel in a 2 M HCl solution was studied using weight loss and potentiodynamic polarization techniques. All of the data reveal that AMPA acts as an inhibitor in the acid environment; furthermore, polarization data show that the compound behaves as a mixed-type inhibitor. It was found that the inhibition efficiency increases with an increase in AMPA concentration but decreases with an increase in temperature. Flory–Huggins adsorption isotherm and El Awady thermodynamic–kinetic model fit the experimental data of the studied compound. Thermodynamic parameters for corrosion and adsorption processes were obtained from experimental data of the temperature studies.     

Computational and electrochemical studies of some amino acid compounds as corrosion inhibitors for mild steel in hydrochloric acid solution

The corrosion inhibition behaviour of four selected amino acid compounds, namely l-cysteine, l-histidine, l-tryptophan and l-serine on mild steel surface in deaerated 1 M HCl solution were studied electrochemically by Tafel polarization and electrochemical impedance spectroscopy methods and computationally by the quantum chemical calculation and molecular dynamics simulation. Electrochemical results show that these amino acid compounds inhibit the corrosion of mild steel in 1 M HCl solution significantly. The order of inhibition efficiency of these inhibitors follows the sequence: l-tryptophan > l-histidine > l-cysteine > l-serine. The quantum chemical calculations were performed to characterize the electronic parameters which are associated with inhibition efficiency. The molecular dynamics simulations were applied to find the equilibrium adsorption configurations and calculate the interaction energy between inhibitors and iron surface. Results obtained from Tafel and impedance methods are in good agreement. The electrochemical experimental results are supported by the theoretical data.     

Properties of 2,6-di-tert.-butyl-4-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-3-yl)-phenol as hole-transport material for life extension of organic light emitting diodes

We studied structural and optical properties of 5′ replaced pyrazoline by hindered phenol 2,6-di-tert.-butyl-4-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-3-yl)-phenol (HPhP) films for application in organic light-emitting diode (OLED) as a hole transport layer (HTL). Analysis of impedance and current-voltage characteristics of ITO/HPhP/Al structure has shown that the current is limited by a space charged region with exponential distribution of traps near Fermi level. Characteristics of electroluminescence structure ITO/HPhP/Alq₃/poly(ethylene glycol) dimethyl ether/Al was studied and analyzed. We performed the comparative analysis of luminescence time decay in two types of electroluminescent devices with HTL from pyrazolines derivative with hindered phenol and without it. We showed that hindered phenol in HTL slows down the degradation processes in OLED.     

Electrochemical and thermodynamic studies to evaluate inhibition effect of 2-[(4-phenoxy-phenylimino)methyl]-phenol in 1 M HCl on mild steel

Inhibition of the corrosion of mild steel in 1.0 M HCl solution by a Schiff base compound named 2-[(4-phenoxy-phenylimino)methyl]-phenol (APS) was investigated at different temperatures (25–55 °C) using electrochemical measurements. The inhibition efficiency increased as APS concentration and temperature increased. It was found that adsorption for APS on mild steel complies with the Langmuir adsorption isotherm in all studied temperature. Thermodynamic parameters (ΔG_ads, ΔH_ads and ΔS_ads) for APS adsorption on mild steel were found out and discussed at each temperature. Time dependency of mild steel in 1.0 M HCl solution in the absence and presence of APS was also studied. The surface morphology of mild steel was examined via SEM analysis.     

Electrosysnthesis of poly(aniline-co-m-amino benzoic acid) for corrosion protection of steel

Conducting polymer (poly(aniline-co-m-amino benzoic acid)) has been deposited on steel surface by cyclic voltammetric technique. The copolymer film was characterized by FTIR, XPS and SEM techniques. The corrosion protection performance of copolymer film on steel was found out by impedance and tafel polarization methods in 1N HCl. The copolymer film was found to be highly corrosion resistant.     

Corrosion inhibition of 6061 Al–15 vol. pct. SiC(p) composite and its base alloy in a mixture of sulphuric acid and hydrochloric acid by 4-(N,N-dimethyl amino) benzaldehyde thiosemicarbazone

The corrosion inhibition characteristics of 4-(N,N-dimethylamino) benzaldehyde thiosemicarbazone (DMABT) on the corrosion behavior of 6061 Al–15 vol. pct. SiC(p) composite and its base alloy were studied at different temperatures in acid mixture medium containing varying concentrations of hydrochloric acid and sulphuric acid using Tafel extrapolation technique and ac impedance spectroscopy (EIS). The effect of inhibitor concentration, temperature and concentration of the acid mixture media on the inhibitor action was investigated. It was found that inhibition efficiencies increase with the increase in inhibitor concentration, but decrease with the increase in temperature and with the increase in concentration of the acid media. Thermodynamic parameters for dissolution process were determined. The adsorption of DMABT on both the composite and base alloy was found to be through physisorption obeying Freundlich adsorption isotherm.     

The inhibition action of N-(furfuryl)-N′-phenyl thiourea on the corrosion of mild steel in hydrochloric acid medium

The inhibiting effect of N-(furfuryl)-N′-phenyl thiourea (FPTU) on the corrosion of mild steel in 0.01 M HCl solution has been demonstrated using potentiodynamic polarization technique. The polarization data have shown that FPTU acts as an efficient anodic inhibitor for mild steel in acid solution. Adsorption of this compound on the mild steel surface was found to obey Temkin's adsorption isotherm. Good inhibition efficiency (> 93%) has been evidenced at 28 °C and 50 °C and inhibition is governed by chemisorption mechanism.     

Effect of PWVA/Sb2O3 complex inhibitor on the corrosion behavior of carbon steel in 55%LiBr solution

The inhibition performance of PWVA/Sb₂O₃ complex inhibitor on carbon steel was studied in 55%LiBr + 0.07 mol L⁻¹ LiOH solution. Results indicated that the complex inhibitor decreased both anodic and cathodic polarization current density and widened the passive potential region of carbon steel in test solution and can be classified as mixed inhibitor. The complex inhibitor exhibited excellent inhibition performance on carbon steel when the concentrations of PWVA and Sb₂O₃ were 300 and 200 mg L⁻¹, respectively. With the solution temperature increasing from 145 to 240 °C, the corrosion rates of carbon steel increased from 4.71 to 120.66 μm y⁻¹. In solution containing the complex inhibitor, the relationship between relative coverage ratio of inhibitor on carbon steel surface and inhibition efficiency at 145 °C was obtained as the equation μ = 0.94η, it was a direct proportion. This result proved that the complex inhibitor inhibited the corrosion of carbon steel by geometric blocking effect. When solution temperature was 160 °C, the adsorption Gibbs free energy of PWVA and Sb₂O₃ on carbon steel were −49.59 and −44.29 kJ mol⁻¹, respectively. It indicated that the adsorption processes of PWVA and Sb₂O₃ on carbon steel surface were spontaneous processes. As a strong oxidant, PWVA facilitated the compact passive film comprising of FeO, Fe₂O₃ and Fe₃O₄ forming on the surface and itself was reduced to heteropoly blue. Sb₂O₃ adsorbed on carbon steel surface formed an adsorption film. PWVA and Sb₂O₃ behaved synergistic effect. The corrosion resistance performance of carbon steel in 55%LiBr + 0.07 mol L⁻¹ LiOH solution was improved by PWVA/Sb₂O₃ complex inhibitor.