A study of synthesized Mannich base inhibition on mild steel corrosion in acid medium

1((Cyclohexylamino)methyl)urea Mannich base was synthesized and characterized using FT-IR, H¹NMR and C¹³NMR spectra and it was tested as a corrosion inhibitor for mild steel in 1?N HCl and 1?N H₂SO₄ solutions using potentiodynamic polarization and AC impedance techniques over the temperature range of 303?C333?K. The inhibition efficiency was increased with respect to concentration of inhibitor and temperature in 1?N HCl, whereas the inhibition efficiency was increased with respect to concentration of inhibitor and decreased with respect to temperature in 1?N H₂SO₄. Potentiodynamic polarization results revealed that the inhibitor acts as mixed type inhibitor. AC impedance study indicates that the corrosion of steel was mainly controlled by a charge transfer process. Surface analysis was carried out using SEM technique. The adsorption of inhibitor follows Langmuir adsorption isotherm. Activation and adsorption parameters were calculated to gain information about the inhibitive action mechanism.     

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     

Quantum chemical studies on some thiadiazolines as corrosion inhibitors for mild steel in acidic medium

Density functional theory at the B3LYP/6-31G(d,p) basis set level was performed on three thiadiazolines, namely 4-chloro-N-(5-phenyl-1,3,4-thiadiazol-2(3H)-ylidene)aniline (TD01), 4-chloro-N-(5-(4-methoxyphenyl)-1,3,4-thiadiazol-2(3H)-ylidene)aniline (TD02), and 2-(5-(4-chlorophenylimino)-4,5-dihydro-1,3,4-thiadiazol-2-yl) phenol (TD03), and the inhibitive effect of these thiadiazolines against the corrosion of mild steel in acidic medium is elucidated. The calculated quantum chemical parameters correlated to the inhibition efficiency are E_HOMO (highest occupied molecular orbital energy), E_LUMO (lowest unoccupied molecular orbital energy), the energy gap (ΔE) hardness (η), softness (S), dipole moment (μ), electron affinity (EA) ionization potential (IE), the absolute electro negativity (χ), and the fraction of electron transferred (ΔN). The decreasing order of %IE of the thiadiazolines studied was found to be in agreement with experimental corrosion inhibition efficiencies. The local reactivity has been analyzed through the condensed Fukui function and local softness indices using population analysis.     

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.     

Corrosion inhibition of mild steel by highly stable polydentate schiff base derived from 1,3- propanediamine in aqueous acidic solution

Recently, the hydrolysis of Schiff bases under experimental conditions gives suspicion for their corrosion inhibition performance. The current study employs a stable Schiff base namely, 2,2′-{propane-1,3-diylbis[azanylylidene (E) methanylylidene]}bis(6-methoxyphenol) (LPD) as corrosion inhibitor for mild steel (MS) in 1 M HCl solution. The presence of the characteristic peak of the imine group in UV-visible spectra was taken as an indicator for LPD stability in acidic media. The inhibition action was examined using electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) besides gravimetric measurement. The inhibition efficiency reached 95.93 % for 0.75 mM LPD after 24 h of immersion at 25 °C. This high efficiency is owing to the presence of the characteristic imine group and other heteroatoms and π- electrons of the aromatic benzene rings. The mechanism of inhibition depends on adsorption phenomena on mild steel surface which obeys Langmuir isotherm model. The calculated values of adsorption equilibrium constant (K_ads), adsorption free energy ΔG_ads, adsorption enthalpy ΔH_ads and adsorption entropy ΔS_ads indicated spontaneous exothermic adsorption process of both physical and chemical nature. By rising temperature, the inhibition efficiency of LPD was decreased. The calculated activation energy was increased as the concentration of LPD increased. LPD was considered as a mixed-type inhibitor as indicated from PDP measurements. The obtained surface morphology and composition analysis using SEM/EDS, AFM and FTIR techniques ensures the high efficiency of LPD as corrosion inhibitor.     

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.     

Adenosine as corrosion inhibitor for mild steel in hydrochloric acid solution

Research on Chemical Intermediates - (2R,3R,4S,5R)-2-(6-amino-9H-purin-9-yl)-5-(hydroxymethyl)oxolane-3,4-diol (adenosine) is an identified component present in agarwood leaf extract. The corrosion...     

Hydroclathrus clathratus marine alga as a green inhibitor of acid corrosion of mild steel

The corrosion inhibitive and adsorption behaviors of Hydroclathrus clathratus on mild steel in 1 M HCl and 1 M H₂SO₄ solutions at 303, 313 and 323 K were investigated by weight loss, electrochemical, and surface analysis techniques. The results show that H. clathratus acts as an inhibitor of corrosion of mild steel in acid media. The inhibition efficiency was found to increase with increase in inhibitor concentration but to decrease with rise in temperature, suggestive of physical adsorption. The adsorption of the inhibitor onto the mild steel surface was found to follow the Temkin adsorption isotherm. The inhibition mechanism was further corroborated by the results obtained from electrochemical methods. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses supported the inhibitive action of the alga against acid corrosion of mild steel.     

Ethanol extracts of Hemidesmus indicus leaves as eco-friendly inhibitor of mild steel corrosion in H2SO4 medium

The inhibitory action of an extract of Hemidesmus indicus leaves as a potential corrosion inhibitor for steel in H₂SO₄ solutions was examined using conventional mass loss, gasometric techniques, electrochemical polarisations and electrochemical impedance spectroscopy. The results revealed that the extract of Hemidesmus indicus leaves performed well as an inhibitor for the corrosion of the metal employed in an accelerating medium. The inhibition efficiencies for all the experimental techniques employed increased with increasing the concentration of the plant extract but decreased with a rise in temperature. Both the cathodic hydrogen evolution and the anodic dissolution of mild steel were inhibited, hence the active molecule of the extract studied acted as a mixed-type corrosion inhibitor.     

Berberine isolated from Mahonia nepalensis as an eco-friendly and thermally stable corrosion inhibitor for mild steel in acid medium

BackgroundThe environmental and economic benefits have been the driving force in search of efficient corrosion inhibitors for iron/steel used in industrial acidic medium. This study reports on berberine isolated from methanol extract of high-altitude (1347 m) shrub Mahonia nepalensis as a highly efficient and thermally stable corrosion inhibitor for mild steel (MS) in 1.0 M H₂SO₄ simulating acid pickling condition.MethodsThe weight-loss and electrochemical methods revealed the fast adsorption of berberine.Significant Findings: It achieved above 91% inhibition efficiency (IE) in 0.25 h and reached 94% in 6 h for 1000 ppm berberine. The IE increased with concentration and temperature, giving an IE of 97.2% at 328 K, which makes it a promising candidate for industrial application. It behaved as a mixed type of inhibitor as revealed by open circuit potential and polarization curves. The results indicated suppression of the corrosion by effectively forming an adsorbed berberine layer on the MS surface. Adsorption of the berberine followed a Langmuir adsorption isotherm. The thermodynamic parameters such as activation energy (43.19 kJ/mol), free energy (−35.05 kJ/mol), enthalpy (40.55 kJ/mol), and entropy (−97.83 J/molK) of adsorption supported both physical and chemical interactions of berberine with MS surface. The obtained results also revealed that the adsorption process was endothermic and spontaneous in nature.     

A second-harmonic generation study of a corrosion inhibitor on a mild steel electrode

Second-harmonic generation at surfaces was used to study the adsorption kinetics of a model corrosion inhibitor, oleic imidazoline, onto the surface of a mild steel electrode. It was found that positive polarization relative to the uninhibited rest potential of the electrode, in deaerated salt solution, increased the rate at which the oleic imidazoline adsorbs onto the surface. Negative polarization increased the rate of desorption from the surface. These results show that oleic imidazoline will stick preferentially to anodic sites on a corroding mild steel electrode and this is the mechanism that leads to build-up of the monolayer of oleic imidazoline on the surface.     

An investigation of carbon steel corrosion inhibition in hydrochloric acid medium by an environmentally friendly green inhibitor

The inhibition effect of polyphenols extracted from olive mill wastewater (PP) on carbon steel in 1.0 M HCl solution was studied. Inhibition efficiency of PP was carried out by using chemical (weight loss method) and electrochemical techniques [potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)]. The effect of temperature and immersion time on the corrosion behavior of carbon steel in 1.0 M HCl with addition of an extract was also studied. The results show that PP acts as a very good inhibitor, and the inhibition efficiency increases with the concentration of PP and decreases with rising temperature. Polarization curves show that PP behaves as a mixed-type inhibitor in hydrochloric acid. Data, obtained from EIS measurements, were analyzed to model the corrosion inhibition process through an appropriate equivalent circuit model; a constant phase element has been used. EIS shows that charge-transfer resistance increases and the capacitance of double layer decreases with the inhibitor concentration, confirming the adsorption process mechanism. The activation energy as well as other thermodynamic parameters for the inhibition process were calculated. The adsorption of PP obeys the Langmuir adsorption isotherm.     

Electrochemical studies of mild steel corrosion inhibition in sulfuric acid chloride by aniline

The corrosion behavior of mild steel in dilute hydrochloric acid under the inhibiting action of various concentrations of aniline was studied using the weight loss and linear polarization resistance technique. The efficiency of the inhibitor increased with the increase in the inhibitor concentration. The results obtained reveal that aniline performed effectively as a corrosion inhibitor. The adsorption mechanism indicates mixed molecular interaction from values of Gibbs free energy. The values of the inhibition efficiency calculated from the two techniques are in reasonably good agreement. The adsorption of the inhibiting compound was found to obey Langmuir, Frumkin and Freudlich adsorption isotherms. The mechanism of inhibition was discussed in the light of the chemical structure of the inhibiting compound and their adsorption on steel surfaces in relation to the potentiodynamic parameters.     

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.     

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 studies on mild steel in HCl by a newly synthesized benzil monohydrazone based Schiff base

The corrosion inhibition effect of newly formulated Schiff base 2-((E)-((E)-2-hydrazone-1, 2-diphenylethylidene) amino phenol) (HDAP) ligand L derived from Benzil monohydrazone and 2-Aminophenol on mild steel in 1 ​M HCl was examined. Electrochemical (Tafel and EIS) and mass loss techniques were employed to evaluate its corrosion protection efficiency. The inhibition efficiency (η %) was elevated with raise in concentration of compound L.Maximum inhibition efficiency of 94.18% was obtained at 0.01 ​M concentration of HDAP from Tafel polarisation curve. From electrochemical impedance (EIS) studies, it was confirmed that increase in concentration of HDAP led to enhancement of the charge transfer resistance. Both physical and chemical types of adsorptions were observed for the Schiff base via π-bonding electrons which obey Langmuir adsorption isotherm. The SEM picture revealed development of a thin layer on metallic surface. Quantum chemical evaluations were conducted to find out the mechanism of corrosion retardation power of HDAP.     

Chitosan as an eco-friendly inhibitor for copper corrosion in acidic medium: protocol and characterization

Natural biopolymer chitosan organic compound (COC) has been used as a copper corrosion inhibitor in molar hydrochloric medium. This study was conducted by weight loss, polarization curves and electrochemical impedance spectroscopy measurements. Scanning electron microscopy, energy dispersive X-ray spectrometry and atomic force microscopy studies were used to characterize the surface of uninhibited and inhibited copper specimens. The study of the temperature effect was carried out to reveal the chemical nature of adsorption. The inhibition efficiency tends to increase by increasing inhibitor concentration to reach a maximum of 87% at 10^?1 mg L^?1. The values of inhibitor efficiency estimated by different electrochemical and gravimetric methods indicate the performance of copper in HCl medium containing COC. Adsorption of COC was found to follow the Langmuir adsorption isotherm. In order to get a better understanding of the relationship between the inhibition efficiency and molecular structure of COC, quantum chemical and molecular dynamics simulation approaches were performed to get a better understanding of the relationship between the inhibition efficiency and molecular structure of chitosan.     

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...