Theoretical studies of some sulphonamides as corrosion inhibitors for mild steel in acidic medium

Density functional theory (DFT) at the B3LYP/6‐31G (d,p) and BP86/CEP‐31G* basis set levels and ab initio calculations using the RHF/6‐31G (d,p) methods were performed on four sulfonamides (namely sulfaacetamide (SAM), sulfapyridine (SPY), sulfamerazine (SMR), and sulfathiazole (STI)) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was SMR > SPY > STI > SAM which corresponded with the order of most of the calculated quantum chemical parameters namely E_HOMO (highest occupied molecular orbital energy), E_LUMO (lowest unoccupied molecular orbital energy), the energy gap (ΔE), the Mulliken charges on the C, O, N, S atoms, hardness (η), softness (S), polarizability (α), dipole moment (μ), total energy change (ΔE_T), electrophilicity (ω), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), and the fraction of electrons transferred (ΔN). Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the sulfonamides studied. The results showed that the %IE of the sulfonamides was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the sulfonamides studied was found to be close to their experimental corrosion inhibition efficiencies. The experimental data obtained fits the Langmuir adsorption isotherm. The negative sign of the E_HOMO values and other thermodynamic parameters obtained indicates that the data obtained supports physical adsorption mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Synthesis and evaluation of some new hydrazones as corrosion inhibitors for mild steel in acidic media

Research on Chemical Intermediates - Mild steel corrosion in HCl solution is an example of corrosion in acidic mediums. The ongoing research efforts to develop novel environmentally friendly...     

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.     

Inhibition of aluminium and mild steel corrosion in acidic medium using Gum Arabic

The corrosion behaviour of mild steel and aluminium exposed to H₂SO₄ solution and their inhibition in H₂SO₄ containing 0.1–0.5 g/L Gum Arabic (GA) used as inhibitor was studied at temperature range of 30–60 °C using weight loss and thermometric techniques. Corrosion rate increased both in the absence and presence of inhibitor with increase in temperature. Corrosion rate was also found to decrease in the presence of inhibitor compared to the free acid solution. Inhibition efficiency increases with increase in concentration of the inhibitor reaching a maximum of 37.88% at 60 °C for mild steel and 79.69% at 30 °C for aluminium at 0.5 g/L concentration of GA. The inhibitor, GA was found to obey Temkin and El-Awady et al. thermodynamic kinetic adsorption isotherm for mild steel and aluminium respectively from the fit of the experimental data at all concentrations and temperatures studied. The phenomenon of chemical adsorption is proposed for mild steel corrosion, while physical adsorption mechanism is proposed for aluminium corrosion. Results obtained for the kinetic/thermodynamic studies indicate that the adsorption of GA onto the metals surface was spontaneous. GA is a better corrosion inhibitor for aluminium than for mild steel.     

Electrochemical investigation of a schiff base synthesized by cinnamaldehyde as corrosion inhibitor on mild steel in acidic medium

The inhibiting effect of (NE)-4-phenoxy-N-(3-phenylallylidene) aniline (PAC) on the corrosion of mild steel in 1.0 M HCl has been studied by electrochemical impedance spectroscopy, and Tafel polarization measurements. The corrosion rate was also calculated theoretically in terms of mm per year and mil per year, using current density values of mild steel in 1.0 M HCl medium. It was found that PAC has a remarkable inhibition efficiency on the corrosion of mild steel especially at high temperatures. The values of E _a obtained in presence of a Schiff base were found to be lower than those obtained in the inhibitor-free solution. The increase of inhibition efficiency percent with temperature increase was associated with the transformation of physical adsorption into chemical adsorption. The thermodynamic functions of adsorption processes have been evaluated and discussed at each temperature. Scanning electron microscope observations of the electrode surface confirmed the existence of a protective adsorbed film of the inhibitor on the electrode surface.     

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.     

Expired pharmaceutical compounds as potential inhibitors for cast iron corrosion in acidic medium

The inhibition potential of some expired waste pharmaceutical drugs, namely cefpodoxime (CF), levofloxacin (LV), ofloxacin (OX) and linezolid (LZ) on cast iron corrosion in 1 M HCl has been tested for the first time by chemical (weight loss) and electrochemical (Tafel polarization and impedance spectroscopy) methods. At a constant acid concentration (1 M HCl), the inhibition efficiency (IE%) increased with the increase of the inhibitors’ concentration. At optimum inhibitor concentration, the CF exhibited the highest inhibition efficiency (95.2%). Inhibitors were adsorbed on the cast iron surface through the Langmuir adsorption isotherm at all concentrations and temperatures studied. Antagonism and synergism arising between the halide ions and the inhibitors were also explained. Thermodynamic parameters have been calculated and are discussed. Tafel polarization curves pointed to all inhibitors acting as mixed-type. Corrosion inhibition properties of the inhibitors have been inferred from FT-IR spectra, UV–Vis spectra, surface morphological analysis and wide-angle X-ray diffraction studies.     

Quantum chemical study of some triazoles as inhibitors of corrosion of copper in acid media

The efficiency of 1H-1,2,4-triazol-3-amine (Tz1), 4-amino-3-hydrazino-4H-1,2,4-triazole-3-thiol (Tz2), and 1H-1,2,4-triazole-3,5-diamine (Tz3) as inhibitors of corrosion of copper in nitric acid was investigated by use of density functional theory (DFT). Quantum chemical data, for example energy of the highest occupied molecular orbital (E _HOMO), energy of the lowest unoccupied molecular orbital (E _LUMO), energy gap (ΔE), dipole moment (μ), electronegativity (χ), electron affinity (A), global hardness (η), softness (σ), ionization potential (I), fraction of electrons transferred from the inhibitor molecules to the metallic atom (ΔN), and total energy (TE), were calculated. All calculations were performed by use of DFT with Gaussian 03W software. A good correlation was found between theoretical data and experimental results.     

Antibacterial drugs as environmentally-friendly corrosion inhibitors for carbon steel in acid medium

The effect of cefazolin (CZ) and cefotaxime (CT) as corrosion inhibitors for carbon steel in 0.5 M H₂SO₄ solution was investigated by use of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), and scanning electron microscopy (SEM). CZ and CT acted as mixed-type inhibitors. Inhibition increased with increasing inhibitor concentration and decreased with increasing temperature. Adsorption of the inhibitors obeyed the Langmuir adsorption isotherm. SEM confirmed inhibition by the inhibitors. Inhibition by 5 × 10^?4 M CZ and 7 × 10^?4 M CT approached 99.6 % and 90.9 %, respectively. The EIS and EFM results were in good agreement with the potentiodynamic data.     

Corrosion inhibitory action of some plant extracts on the corrosion of mild steel in acidic media

The alcoholic extracts of eight plants namely Lycium shawii, Teucrium oliverianum, Ochradenus baccatus, Anvillea garcinii, Cassia italica, Artemisia sieberi, Carthamus tinctorius, and Tripleurospermum auriculatum grown in Saudi Arabia were studied for their corrosion inhibitive effect on mild steel in 0.5 M HCl media using the open circuit potential (OCP), Tafel plots and A.C. impedance methods. All the plant extracts inhibited the corrosion of mild steel in acidic media through adsorption and act as mixed-type inhibitors.     

Alcoholic Mentha extracts as inhibitors of low-carbon steel corrosion in aqueous medium

This paper presents experimental evidence of the ability of alcoholic Mentha extracts to inhibit the corrosion of low-carbon steel in aqueous acid solutions. Alcoholic extracts of Mentha spicata L., Mentha x gentilis L., Mentha crispa L., Mentha piperita L., and Mentha x piperita L. were tested. The corrosion inhibition capability of these extracts was confirmed by means of weight loss experiments, cyclic voltammetry, chronoamperometry, polarization curves, and electrochemical impedance spectroscopy.     

Schiff’s bases as inhibitors of mild steel corrosion in hydrochloric acid

Mass loss and thermometric methods are used to study the inhibition of corrosion of mild steel in hydrochloric acid by Schiff’s bases N-(furfurlidine)-4-methoxy aniline, N-(furfurlidine)-4-methylaniline, N-(salicylidine)-4-methoxy aniline, N-(cinnamalidine)-4-methoxy aniline, and N-(cinnamalidine)-2-methylaniline. Results of inhibition efficiency yielded by the two methods are in good agreement and depend on the inhibitor and acid concentration. Maximum inhibition efficiency is 98%. The efficiency increases with the inhibitor concentration and acid strength. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 252–256. The text was submitted by the authors in English.     

Synthesis,X-ray structure and theoretical study of benzazole thioether and its zinc complex as corrosion inhibitors for steel in acidic medium

A ligand, 2-((benzo[d]thiazol-2-ylthio)methyl)-1H-benzo[d]imidazole, and its zinc complex have been synthesized. The structure of these compounds have been determined by spectroscopic techniques and single crystal X-ray diffraction. The corrosion inhibition study of these compounds for steel in 0.5 M H₂SO₄ medium has also been investigated using potentiodynamic polarization and EIS techniques. The quantum calculations were applied to investigate the relationship between the electronic properties and the corrosion inhibition efficiency of the two benzazoles derivatives. Surface analysis (XRF) indicated that the rust layer formed on the Cu-containing steels was enriched with Cu compounds. Polarization curves revealed that both inhibitors acted as a mixed-type inhibitor.     

Azorhodanine derivatives as inhibitors for acidic corrosion of nickel

Azorhodanine derivatives (HL1-HL5) were tested as corrosion inhibitors for nickel in 2M HNO3 solution using weight loss and galvanostatic polarization techniques. The results showed that these derivatives act as inhibitors for nickel in this medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. Polarization measurements indicated that these compounds act as mixed-type inhibitors, but the cathode is more polarized when an external current was applied. This means that these compounds retard the rate of hydrogen evolution and the rate of dissolution of the metal. Results showed that azorhodanine derivatives are adsorbed on the nickel surface following Temkin's adsorption isotherm. The activation energy and thermodynamic parameters were calculated and discussed at different temperatures (30-45 degrees C).     

New Schiff base cationic surfactants as corrosion inhibitors for carbon steel in acidic medium: weight loss,electrochemical and SEM characterization techniques

Research on Chemical Intermediates - Two new Schiff base cationic surfactants were synthesized and their chemical structures confirmed using FTIR spectroscopy. The tensioactive and thermodynamic...     

Influence of pyridazine derivative on corrosion inhibition of mild steel in acidic media

The inhibition behavior of 6-methyl-4,5-dihydropyridazin-3(2H)-one (MDP) on corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ was investigated using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) measurements. The results indicated that the corrosion inhibition efficiency depends on concentration, immersion time, solution temperature, and the nature of the acidic solutions. It is also noted that MDP is at its the most efficient in 1 M HCl and least in 0.5 M H₂SO₄. The effect is more pronounced with MDP concentration. It is found that the inhibition efficiency attains 98 % at 5 × 10^?3 M in 1 M HCl and 75 % at 5 × 10^?2 in 0.5 M H₂SO₄. Polarization measurements showed that the MDP acts as a mixed inhibitor. EIS diagrams showed that the adsorption of MDP increases the transfer resistance and decreases the capacitance of the interface metal/solution. From the temperature studies, the activation energies in the presence of MDP were found to be superior to those in uninhibited medium. Finally, a mechanism for the adsorption of MDP was proposed and discussed.     

Corrosion inhibition of mild steel in acidic medium by butyl alcohol

The corrosive behavior of mild steel in 1 M H₂SO₄ solutions contaminated with 3.5 % recrystallized sodium chloride at specific concentrations of butyl alcohol was investigated using potentiodynamic polarization and weight loss technique. The results obtained showed butyl alcohol to be an efficient inhibitor in the acid environment with general decrease in corrosion rate as the concentration of the alcohol increases. The adsorption of the inhibitor on the mild steel obeys the Langmuir adsorption isotherm. The thermodynamic parameters of adsorption deduced reveal a mixed interaction with the steel surface and spontaneous adsorption of butyl alcohol.     

Performance of some thiophene derivatives as corrosion inhibitors for 304 stainless steel in aqueous solutions

The inhibitive effect of 2-cyano-3-hydroxy-4(Ar)-5-anilino thiophene derivatives on the corrosion of 304 stainless steel (SS) in 3 M HCl solution has been investigated by weight loss, galvanostatic polarization techniques, and potentiodynamic anodic polarization in 3.5 % NaCl. The results indicate that these compounds act as inhibitors retarding the anodic and cathodic corrosion reactions. The presence of inhibitors does not change the mechanism of either hydrogen evolution reaction or SS dissolution. The activation energy and some thermodynamic parameters are calculated and discussed. These compounds are mixed-type inhibitors in the acid solution, and their adsorption on the SS surface is found to obey the Temkin adsorption isotherm. The results suggest that the percentage inhibition of these thiophene derivatives increases with increasing inhibitor concentration and decreases with increasing temperature. The synergistic parameter (S) was calculated and found to have a value greater than unity, indicating that the enhanced inhibition efficiency caused by the addition of I^?, SCN^?, and Br^? is only due to a synergistic effect. The relationship between molecular structure and inhibition efficiency was elucidated by quantum-chemical calculations using semi-empirical self-consistent field (SCF) methods.