A novel Schiff base-based cationic gemini surfactants: Synthesis and effect on corrosion inhibition of carbon steel in hydrochloric acid solution

The corrosion inhibition characteristics of the synthesized cationic gemini surfactants, namely bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene thiourea (10-S-10), bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene thiourea (12-S-12) and bis(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene thiourea (14-S-14) on the carbon steel corrosion in 1 M hydrochloric acid have been investigated at 25 °C by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiencies obtained from all methods employed are in good agreement with each other. The obtained results show that compound 14-S-14 is the best inhibitor with an efficiency of 97.75% at 5 × 10⁻³ M additive concentration. Generally, the inhibition efficiency increased with increase of the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, R_ct, and double-layer capacitance, C_dl) were indicative of adsorption of 14-S-14 on the metal surface, leading to the formation of a protective film. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir’s adsorption isotherm. The free energy of adsorption processes were calculated and discussed. The surface parameters of each synthesized surfactant were calculated from its surface tension including the critical micelle concentration (CMC), maximum surface excess (Γ_max) and the minimum surface area (A_min). The free energies of micellization (ΔG^o_mic) were calculated. The surface morphology of carbon steel sample was investigated by scanning electron microscopy (SEM).     

Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine

The behavior of the Schiff base N,N′-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N′-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1 mol L⁻¹ HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the inhibitors studied. The results obtained in the presence of Salen were similar to those obtained in the presence of the salicylaldehyde and ethylenediamine mixture, showing that in acid medium the Salen molecule undergoes hydrolysis, regenerating its precursor molecules.     

The effect of ionic liquids with imidazolium and pyridinium cations on the corrosion inhibition of mild steel in acidic environment

Ionic liquids with chemical formula 1,3-dioctadecylimidazolium bromide and N-Octadecylpyridinium bromide were synthesized by conventional and microwave-assisted reactions, respectively. Ionic liquids tested as corrosion inhibitors after polarization curves displayed corrosion protection efficiency within 82-88% at 100 ppm for mild steel in a 1 M aqueous solution of sulfuric acid. Standard free energy indicated that corrosion inhibition occurred by a chemical adsorption process. Surface analysis (SEM, EDX) completed by XRD and Mössbauer spectroscopy indicated the presence of carbon species pertaining to inhibitor and corrosion products, which was rationalized in an inhibition mechanism.     

Synthesis and evaluation of new long alkyl side chain acetamide, isoxazolidine and isoxazoline derivatives as corrosion inhibitors

2-(Alkylsulfanyl)-N-(pyridin-2-yl) acetamide derivatives were synthesized via amidation reaction of acyl chlorides bearing S atom in the long chain with 2-aminopyridine. Derivatives of isoxazolidine and isoxazoline were synthesized through 1,3-dipolar cycloaddition reactions with three different long chain alkenes containing O or S as hetero atoms and C,N-diphenyl nitrone or benzonitrile-N-oxide, respectively. Synthesized compounds were characterized with their FT-IR, ¹H NMR spectra and then their physical properties and corrosion prevention efficiencies were investigated. All compounds were tested with steel coupons in acidic medium by gravimetric method, and also some of them were tested with steel stripe in paraffin based mineral oil medium via standard method. Acidic test was done with a medium concentration of 2 M HCl for 20 h at room temperature. Mineral oil was used and the test in this medium was done at 60 °C constant temperature but varying time from 42 to 63 h. The best inhibition was generally obtained at 50 ppm inhibitor concentration in the acidic medium. All tested inhibitors except two of them in oil medium also showed promising inhibition efficiencies.     

Corrosion inhibition efficiency and surface activity of benzothiazol-3-ium cationic Schiff base derivatives in hydrochloric acid

Two series of cationic Schiff base surfactants namely: 2-(benzylideneamino)-3-(2-oxo-2-alkoxyethyl)-1,3-benzothiazol-3-ium bromide and 2-[(4-methoxybenzylidene)amino]-3-(2-oxo-2-alkoxyethyl)-1,3-benzothiazol-3-ium bromide were prepared and confirmed using elemental analysis, FTIR, and ¹H NMR spectra. The surface activity of the synthesized Schiff bases showed their tendency towards adsorption at the interfaces. The prepared compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution using gravimetric and polarization measurements. By fitting the gravimetric data, some thermodynamic and kinetic parameters were estimated. The adsorption of the inhibitors on the carbon steel surface obeyed Langmuir adsorption isotherm and had a physical mechanism. Polarization measurements showed that the synthesized inhibitors act as mixed inhibitors for carbon steel in the acidic media. The results of the corrosion inhibition using two different methods showed narrow differences in the obtained values between the two methods within 5%.     

Inhibition effect of novel nonionic surfactants on the corrosion of carbon steel in acidic medium

The inhibition effect of novel nonionic surfactants on the corrosion of carbon steel (CS) in 1 M HCl was studied at different temperatures (20-60 °C) by weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The CS surface morphology was investigated by SEM. The obtained results showed that the prepared nonionic surfactants are excellent inhibitor in 1 M HCl, and the inhibition efficiency (η) increases with the inhibitor concentration and temperature increasing. The adsorption of inhibitors on the CS surface obeys the Langmuir adsorption isotherm equation. Thermodynamic parameters have been obtained by adsorption theory. Polarization curves show that the synthesized inhibitors are mixed-type inhibitors in hydrochloric acid.     

N-Phenylcinnamimide and some of its derivatives as inhibitors for corrosion of lead in HCl solutions

The anodic and cathodic polarization behavior of lead electrode was studied galvanostatically in HCl solutions of various concentrations. Increasing the acid concentration enhances the rate of the anodic dissolution of the metal and the rate of hydrogen evolution reaction, with anodic and cathodic Tafel slopes equal to 30 and 115 ± 5 mV decade⁻¹, respectively. The effect of addition of N-phenylcinnamimide and some of its derivatives, N-(p-nitrophenyl)cinnamimide, N-(p-methylphenyl)cinnamimide, and N-(p-methoxyphenyl)cinnamimide, as inhibitors on the kinetic of the anodic and cathodic reactions of lead in 0.1 M HCl solutions was also studied. These compounds inhibit both the rate of anodic dissolution and the rate of hydrogen evolution reactions without affecting the Tafel slopes. This result indicates that the used compounds were of mixed-type. The inhibition efficiency of these additives increases in the order: N-(p-nitrophenyl)cinnamimide < N-phenylcinnamimide < N-(p-methylphenyl)cinnamimide < N-(p-methoxyphenyl)cinnamimide. The equilibrium constant and the free energy of adsorption process have been calculated and discussed.     

Electrochemical behaviour of carbon steel in acid chloride solution in the presence of dodecyl cysteine hydrochloride self-assembled on gold nanoparticles

In this work, the dodecyl cysteine hydrochloride surfactant was synthesized. The surface properties of this surfactant were studied using surface tension technique. The nanostructure of this surfactant with the prepared gold nanoparticles was investigated using TEM technique. The synthesized surfactant and its nanostructure with the prepared gold nanoparticles were examined as non-toxic corrosion inhibitors for carbon steel in 2 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The results show that the percentage inhibition efficiency (η%) for each inhibitor increases with increasing concentration until critical micelle concentration (CMC) is reached. The maximum inhibition efficiency approached 76.6% in the presence of 175 ppm of dodecyl cysteine and 90.8% in the presence of the same concentration of dodecyl cysteine hydrochloride self-assembled on gold nanoparticles. Polarization data indicate that the selected additives act as mixed type inhibitors. The slopes of the cathodic and anodic Tafel lines (β_c and β_a) are approximately constant and independent of the inhibitor concentration. Analysis of the impedance spectra indicates that the charge transfer process mainly controls the corrosion process of carbon steel in 2 M HCl solution both in the absence and presence of the inhibitors. Adsorption of these inhibitors on carbon steel surface is found to obey the Langmuir adsorption isotherm. From the adsorption isotherms the values of adsorption equilibrium constants (K_ads) were calculated. The relatively high value of (K_ads) in case of dodecyl cysteine hydrochloride self-assembled on gold nanoparticles reveals a strong interaction between the inhibitor molecules and the metal surface.     

Application of some ferrocene derivatives in the field of corrosion inhibition

Three ferrocene derivatives, namely 1,1′-diacetylferrocene (Diacetyl Fc), 1,1′-diformylferrocene (Diformyl Fc) and 2-benzimidazolythioacetylferrocene (BIM Fc) were synthesized and their inhibitive effects against mild steel corrosion in aerated 0.5 M H₂SO₄ and 1 M HCl solutions were evaluated. Corrosion measurements based on polarization resistance (R_p), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) indicate that Diacetyl Fc, in most cases, accelerates mild steel corrosion in HCl while Diformyl Fc and BIM Fc act as weak inhibitors. In H₂SO₄ solution, ferrocene derivatives show good inhibition performance. The efficiency of the inhibitors follows the order: BIM Fc > Diformyl Fc ? Diacetyl Fc. Adsorption of both Diacetyl Fc and Diformyl Fc obey Langmuir adsorption isotherm with very low value of free energy of adsorption ΔG^° for the Diformyl Fc (physisorption) while adsorption of BIM Fc follows that of Frumkin with high negative value of ΔG^° (chemisorption). Both Diformyl Fc and BIM Fc act as mixed-type inhibitors with predominant effect on the anodic dissolution of iron. Analysis of the polarization curves and impedance spectra indicates that charge transfer process mainly controls mild steel corrosion in H₂SO₄ solution without and with ferrocene compounds. The mechanism of corrosion inhibition or acceleration by ferrocene derivatives was discussed in the light of the molecular structure of the additives.     

Theoretical studies on the spectroscopic properties of a series of halide Zinc (II) complexes with pyridinylimine and pyridinylmethylamine derivatives

The ground structures of pyridinylimine derivatives (L1-a = N-(pyridin-2-ylmethylene)aniline and L1-b = N¹,N¹-(dimethyl-N⁴-pyridin-2-ylmethylene)benzene-1,4-diamine) and pyridinylmethylamine derivatives (L2-a = N-(pyridin-2-ylmethyl)aniline and L2-b = N¹,N¹-(dimethyl-N⁴-pyridin-2-ylmethy)benzene-1,4-diamine) and their corresponding Zn (II) complexes ([Zn(L1-a)Cl₂] (A), [Zn(L1-b)Cl₂] (B), [Zn(L2-a)Cl₂] (C), and [Zn(L2-b)Cl₂] (D)) are optimized at three DFT levels, i.e., B3LYP, B3PW91, and M06. The spectroscopic properties are calculated using time-dependent density functional theory (TD-DFT) in gas and in solution. The occupied orbitals involved in the transitions have mixed character of the Cl atom p orbital and ligand-based π orbital, while the lowest unoccupied molecular orbital (LUMO) presents π* orbital character. Two UV–Vis absorption peaks located at 252 and 353 nm are assigned to (p, π) → π* transition with mixed intraligand charge-transfer (ILCT)/ligand–ligand charge-transfer (LLCT) character and π → π* transition with ILCT character for complex A, respectively. With respect to complex B, the absorption bands show red shift with two peaks at 281 and 470 nm with the appearance of an electron-releasing group (–N(CH₃)₂) because the energy gap (ΔE|HOMO–LUMO|) is decreased. Red shift phenomenon is also observed between other two complexes C and D. Comparison between theoretical and experimental results for the structures and spectra is discussed in detail.     

Inhibitive properties of quaternary ammonium bromides of N-containing heterocycles on acid mild steel corrosion. Part I: Gravimetric and voltammetric results

Four quaternary ammonium bromides of different heterocyclic compounds were investigated as corrosion inhibitors of mild steel in 1 M HCl and 1 M H₂SO₄. Polarisation curves, polarisation resistance and gravimetric methods were used. The inhibitor efficiency was found to depend on both concentration and temperature. The inhibitors were of mixed type, influencing predominantly the anodic process. From the temperature dependences the apparent activation energy in 1 M HCl was determined in the presence of all studied compounds, found to be inferior to the activation energy in absence of inhibitor. The adsorption of the inhibitors was well described by the Frumkin or the Langmuir adsorption isotherms in both acidic media and the adsorption isotherm parameters were determined at room temperature. The influence of the molecular structure was discussed taking into account the different number of positive charges and the different heterocycles. The best inhibitive properties had 1-(carbamoylethyl)-4-methylpyridinium bromide.     

Corrosion inhibition of carbon steel in tetra-n-butylammonium bromide aqueous solution by benzotriazole and Na3PO4

The corrosion inhibition behavior of benzotriazole, Na₃PO₄ and their mixture on carbon steel in 20 wt.% (0.628 mol l⁻¹) tetra-n-butylammonium bromide aerated aqueous solution was investigated by weight-loss test, potentiodynamic polarization measurement, electrochemical impedance spectroscopy and scanning electron microscope/energy dispersive X-ray techniques. The inhibition action of BTA or SP or inhibitors mixture on the corrosion of carbon steel is mainly due to the inhibition of anodic process of corrosion. The results revealed that inhibitors mixtures have shown synergistic effects at lower concentration of inhibitors. At 2 g l⁻¹ BTA and 2 g l⁻¹ SP showed optimum enhanced inhibition compared with their individual effects.     

Theoretical study of benzimidazole and its derivatives and their potential activity as corrosion inhibitors

A theoretical study of benzimidazole (BI) and two of its derivatives namely 2-methylbenzimidazole (2-CH₃BI) and 2-mercaptobenzimidazole (2-SHBI) recently used as corrosion inhibitors for mild steel in 1 M HCl was undertaken by considering Density Functional Theory (DFT) at the B3LYP/6-311G++(d,p) level. The properties most relevant to their potential action as corrosion inhibitors has been calculated in the neutral and protonated form: E_HOMO, E_LUMO, energy gap (ΔE), dipole moment (μ), electronegativity (χ), global hardness (η) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (ΔN). The theoretical results are in agreement with the experimental data.     

Poly(N-methylaniline) coatings on stainless steel by electropolymerization

Poly(N-methylaniline) (PNMA) coatings have been electropolymerized on 304 stainless steel alloy by potentiodynamic, galvanostatic and potentiostatic synthesis techniques from aqueous solutions of 0.1 M N-methylaniline (NMA) and 0.3 M oxalic acid. Characterization of PNMA coatings was carried out by cyclic voltammetry, UV-Vis and FTIR spectroscopy techniques. Corrosion behavior of PNMA coated stainless steel electrodes was investigated using linear anodic potentiodynamic polarization, Tafel test, chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques in 0.5 M aqueous HCl solutions. Corrosion test results showed that PNMA coatings possessed protection to uncoated stainless steel against corrosion.     

Hydrophobic-tailed bicycloisoxazolidines: A comparative study of the newly synthesized compounds on the inhibition of mild steel corrosion in hydrochloric and sulfuric acid media

The cycloaddition reactions of the cyclic nitrones 1-pyrroline 1-oxide and 3,4,5,6-tetrahydropyridine 1-oxide with alkenes, 11-phenoxy-1-undecene and 11-p-methoxyphenoxy-1-undecene, afforded cycloaddition products (bicyclic isoxazolidines) in excellent yields. One of the cycloadducts on reaction with propargyl chloride and ring opening with zinc in acetic acid afforded quaternary ammonium salt and aminoalcohol, respectively. All the new inhibitor molecules in the presence of 400 ppm at 60 °C achieved inhibition efficiencies, determined by gravimetric method, in the range 99-99.6% and 85-99% for mild steel in 1 M HCl and 0.5 M H₂SO₄, respectively. Comparable results were obtained by the electrochemical methods using Tafel plots and electrochemical impedance spectroscopy for the synthesized compounds. The isoxazolidine derivatives were also found to be good inhibitors of mold steel corrosion in synthetic brine. Negative values of in the acidic media ensured the spontaneity of the adsorption process. While the corrosion inhibition by these molecules was predominantly under cathodic control in 1 M HCl, the inhibition in 0.5 M H₂SO₄ was found to be under anodic control. The isoxazolidines and their derivatives were found to be among a rare class of molecules, which provide suitable inhibition mechanism for the corrosion inhibition in HCl as well as in H₂SO₄ media.     

Investigation of the HCl (g) attack on pre-oxidized pure Fe, Cr, Ni and commercial 304 steel at 400 °C

The paper presents the results from an investigation studying the ability of pre-oxidized metals and alloys to withstand chlorine attack in the form of gaseous HCl. The materials under investigation were pure Fe (s), Cr (s), Ni (s), and a commercial 18Cr-10Ni-Fe (304) alloy. The samples were pre-oxidized in different well defined environments, dry 10 vol.% O₂ (g) + N₂ (bal.), 10 vol.% O₂ (g) + 5 vol.% H₂O (g) + N₂ (bal.) and 10 vol.% O₂ (g) + 250 vppm SO₂ (g) + N₂ (bal.) for 24 h at 400 °C using a horizontal tube furnace. Afterwards the oxide films were characterized by GI-XRD, FEG-SEM, XPS and ToF-SIMS. The samples were then exposed further in 10 vol.% O₂ (g) + 500 vppm HCl (g) + x (x = 5 vol.% H₂O (g), 250 vppm SO₂ (g)) + N₂ (bal.). The exposure time was 100 h and after the exposures during the cool down process the reaction chamber was flushed with dry 10 vol.% O₂ (g) + N₂ (bal.). The corroded samples were then examined by the same techniques mentioned before. HCl (g) showed mainly to be aggressive toward the Fe (s) samples that form a relatively thick and porous oxide scale consisting of layered Fe₂O₃ (s)/Fe₃O₄ (s) during pre-oxidation, and the aggressiveness did not depend on the pre-oxidation conditions. All the other materials formed thin and dense oxides (20-100 nm) during pre-oxidation, and they did not suffer accelerated oxidation caused by HCl (g) during the subsequent exposure. The only exception was Ni (s) that had been pre-oxidized in an atmosphere containing SO₂ (g), in this case Ni sulphides and sulphates were formed during pre-oxidation which in turn caused accelerated oxidation to Ni when subsequently exposed to HCl (g). HCl (g) readily reacts with NiSO₄ (s) and Ni₃S₂ (s) and forms NiCl₂ (s) and SO₃ (g).     

The application of some polydentate Schiff base compounds containing aminic nitrogens as corrosion inhibitors for mild steel in acidic media

The effect of three Schiff base compounds namely, (E)-2-(1-(2-(2-hydroxyethylamino)ethylimino)ethyl)phenol(I), 2,2′-(1E,1′E)-1,1′-(2,2′-azanediylbis(ethane-2,1-diyl)bis(azan-1-yl-1-ylidene))bis(ethan-1-yl-1-ylidene)diphenol(II) and 2,2′-((2E,12E)-3,6,9,12-tetraazatetradeca-2,12-diene-2,13-diyl)diphenol(III) on the corrosion behavior of steel in 2 M HCl solution has been investigated at 298 K by weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiencies obtained from all methods employed are in good agreement. Results show compound III to be the best inhibitor with a mean efficiency of 93% at 10⁻² M additive concentration. Studies showed all three compounds to act as mixed type inhibitors and to obey the Langmuir adsorption isotherm.     

Corrosion inhibition of carbon steel using novel N-(2-(2-mercaptoacetoxy)ethyl)-N,N-dimethyl dodecan-1-aminium bromide during acid pickling

A novel cationic surfactant, N-(2-(2-mercaptoacetoxy)ethyl)-N,N-dimethyl dodecan-1-aminium bromide, has been synthesized to study its corrosion inhibiting effect against carbon steel in 1.0 M HCl solution. The corrosion inhibition efficiency was measured by using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and weight loss methods. The inhibition efficiencies obtained from these methods were in good agreement. The inhibition efficiency slightly decreased in the temperature range 30–60 °C. The synthesized inhibitor acted as a mixed inhibitor. Thermodynamic adsorption and activation parameters were discussed. Adsorption of the synthesized inhibitor was found to follow the Langmuir adsorption isotherm. A chemical adsorption mechanism is proposed.     

Effectiveness of some diquaternary ammonium surfactants as corrosion inhibitors for carbon steel in 0.5 M HCl solution

Four Gemini surfactants were synthesized and characterized using elemental analysis, FTIR and ¹H NMR spectroscopy. The synthesized compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution. The inhibition efficiencies of the tested inhibitors were depended on the hydrophobic chain length and the used doses of the inhibitors. The polarization measurements showed that these inhibitors are acting as mixed inhibitors for both anodic and cathodic reactions. The results showed that the inhibition efficiencies were increased by increasing the inhibitor doses and the hydrophobic chain length and reached the maximum at 500 ppm by weight for stearyl derivative. The efficiencies obtained from the impedance measurements were in good agreement with those obtained from the gravimetrical and polarization techniques which prove the validity of these tolls in the measurements of the tested inhibitors.     

The effects of substituting oxygen for terminal nitrogen in aniline oligomers 2: A DFT comparison of diamino,dihydroxyl, and monoamino/monohydroxyl terminated aniline trimers

The variant aniline trimers, N,N′-bis (3′,4′-diaminophenyl)-1,4-quinonediimine; N,N′-bis (3′-hydroxy-,4′-aminophenyl)-1,4-quinonediimine; and N,N′-bis (3′,4′-dihydroxyphenyl)-1,4-quinonediimine were synthesized, and the properties of the compounds compared to the results of density functional theory (DFT) calculations using the B3LYP functional. The calculations are complicated by the large number (five) of isomeric forms of each compound. Each compound energetically preferred the syn-, syn- (outer) isomer. The computed vertical ionization energies for the same isomer of each compound are 75.0, 76.10, and 83.1 kcal mol⁻¹, respectively. The trimer with two oxygen atoms on each outer ring thus holds electrons more tightly than the trimers with either one or zero oxygen atoms on the outer rings. The electronic spectra computed by the ΔSCF method are in excellent agreement with experimental values, though inclusion of solvent effects does not improve the predictions. A red-shift upon change to more polar solvents confirms that the principal absorption band for each trimer is π → π*, in agreement with electronic structure calculations.