Influence of tramadol [2-[(dimethylamino)methyl]-1-(3-methoxyphenyl) cyclohexanol hydrate] on corrosion inhibition of mild steel in acidic media

Tramadol[2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol hydrate], a drug, was tested as a corrosion inhibitor for mild steel in 0.5 M HCl and 0.25 M H₂SO₄ separately at 300, 310 and 320 K using mass loss and galvanostatic polarization techniques. The percentage protection efficiencies were evaluated at different concentrations of the inhibitor at different temperatures. The protection efficiency increased with increase in inhibitor concentration and decreased with increase in temperature in both the acid solutions. Galvanostatic polarization studies showed that the inhibitor is of mixed type with a slight predominance of cathodic character. The inhibitor was more active in HCl than in H₂SO₄. The maximum protection efficiency approached 82.6% in the presence of 2.16 × 10⁻³ M inhibitor. Some samples of mild steel were examined by scanning electron microscopy. The inhibitor was found to adsorb on the mild steel surface according to the Langmuir adsorption isotherm. The thermodynamic functions of dissolution and adsorption processes were evaluated.     

Inhibiting and accelerating effects of aminophenols on the corrosion and permeation of hydrogen through mild steel in acidic solutions

The influence of aminophenols on the corrosion and hydrogen permeation of mild steel in 1 M HCl and 0.5 M H₂SO₄ has been studied using weight loss and gasometric measurements and various electrochemical techniques. All the isomers of aminophenol inhibit the corrosion of mild steel in 1 M HC1 and accelerate it in 0.5 M H₂SO₄. They behave predominantly as cathodic inhibitors. Aminophenols, except PAP in I M HCI, enhance the permeation current in both the acids. The adsorption of PAP on the mild steel surface in 1 M HCl obeys the Langmuir adsorption isotherm. Surface analysis and ultraviolet spectral studies are also carried out to establish the mechanism of corrosion inhibition and acceleration of mild steel in acidic solutions.     

Influence of anions on the performance of isomers of aminobenzoic acid on the corrosion inhibition and hydrogen permeation through mild steel in acidic solutions

The influence of aminobenzoic acids on the corrosion and hydrogen permeation through mild steel in 1 m HC1 and 0.5 M H₂SO₄ has been studied using weight loss and gasometric measurements and various electrochemical techniques. All the three isomers of aminobenzoic acid inhibit the corrosion of mild steel both in HC1 and H₂SO₄ in the order ortho > meta > para. It is observed that the inhibition is greater in HCI than in H₂SO₄. The predominant behaviour is in the cathodic inhibitor mode. These compounds reduce the permeation current in 111 HCl and enhance it in 0.51 v1 H₂SO₄. The adsorption of these compounds on mild steel in 1 m HC1 and 0.5 m H₂SO₄ obeys Langmuir's adsorption isotherm.     

Electrochemical characterization of the protective film formed by the unsymmetrical Schiff's base on the mild steel surface in acid media

The corrosion inhibition efficiency of a newly synthesized Schiff's base for the corrosion of mild steel was studied in 1.0 M HCl and 0.5 M H₂SO₄ solutions. The results of weight loss measurements, electrochemical impedance and potentiodynamic polarization measurements consistently demonstrated that the Schiff's base synthesized is a good corrosion inhibitor with an inhibitory efficiency of approximately 92% at an optimum inhibitor concentration of 600 mg/L. The inhibition in both of the corrosive media was observed to be a mixed type. The potential of zero charge (PZC) at the metal–solution interface was determined for both the inhibited and uninhibited solutions to provide the mechanism of inhibition. The inhibitor formed a film on the metal surface through chloride or sulfate bridges depending upon the medium. The temperature dependence of the corrosion rate was also studied in the temperature range from 27 to 50 °C. The value of the activation energy (E_a) calculated showed that the inhibition film formation on the metal surface occurred through chemisorption. The thermodynamic parameters such as the adsorption equilibrium constant (K_ads) and the free energy of adsorption (ΔG_ads) were calculated and discussed. Several adsorption isotherms were tested and the experimental data fit well with the Langmuir adsorption isotherm.     

Corrosion inhibition of mild steel in acidic medium by poly (aniline-co-<Emphasis Type="Italic">o</Emphasis>-toluidine) doped with <Emphasis Type="Italic">p</Emphasis>-toluene sulphonic acid

The corrosion behaviour of mild steel in 0.5 M H₂SO₄ solution containing various concentrations of a p-toluene sulphonic acid doped copolymer formed between aniline and o-toluidine was investigated using weight loss, polarization and electrochemical impedance techniques. The copolymer acted as an effective corrosion inhibitor for mild steel in sulphuric acid medium. The inhibition efficiency has been found to increase with increase in inhibitor concentration, solution temperature and immersion time. Various parameters like E _a for corrosion of mild steel in presence of different concentrations of inhibitor and ΔG _ads, ΔH ⁰, ΔS ⁰ for adsorption of the inhibitor, revealed a strong interaction between inhibitor and mild steel surface. The adsorption of this inhibitor on the mild steel surface obeyed the Langmuir adsorption equation.     

In depth analysis of anti corrosion behaviour of eco friendly gum exudate for mild steel in sulphuric acid medium

The current research work was keen to examine the corrosion inhibition efficiency of mild steel (MS) in presence of aqueous extract of Araucaria heterophylla Gum (AHG) in 1?M H₂SO₄ medium. The phytoconstituents of the AHG were interpreted by GC-MS and corrosion inhibition efficiency was deduced using other techniques like weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS). Adsorption of inhibitor molecules on the mild steel surface was supported by Density Functional Theory (DFT) studies, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). It is seen from the results that the inhibitor exhibits optimum efficiency of 78.57% at 0.05% v/v on mild steel specimen in 1?M H₂SO₄ medium at room temperature. Tafel polarizations clearly show that the aqueous extract of AHG acts as a mixed type inhibitor. The change in the EIS parameters in presence of inhibitor is investigative of the protective layer formation of the mild steel surface. The adsorption is found to obey Langmuir adsorption isotherm. Thermodynamic and activation parameters for the corrosion inhibition process supported the physical adsorption mechanism.     

Performance evaluation of poly (methacrylic acid) as corrosion inhibitor in the presence of iodide ions for mild steel in H2SO4 solution

The inhibition performance of poly (methacrylic acid) (PMAA) and the effect of addition of iodide ions on the inhibition efficiency for mild steel corrosion in 0.5 M H₂SO₄ solution were investigated in the temperature range of 303–333 K using electrochemical, weight loss, scanning electron microscopy (SEM), and water contact angles measurements. The results show that PMAA is a moderate inhibitor for mild steel in 0.5 M H₂SO₄ solution. Addition of small amount of KI to PMAA significantly upgraded the inhibition efficiency up to 96.7%. The adsorption properties of PMAA and PMAA + KI are estimated by considering thermodynamic and kinetic parameters. The results reveal that PMAA alone was physically adsorbed onto the mild steel surface, while comprehensive adsorption mode characterized the adsorption of PMAA + KI. Adsorption of PMAA and PMAA + KI followed Temkin adsorption isotherm. The SEM and water contact angle images confirmed the enhanced PMAA film formation on mild steel surface by iodide ions.     

Hyperbranched poly(cyanurateamine): A new corrosion inhibitor for mild steel in hydrochloric acid medium

Hyperbranched poly(cyanurateamine) (POCYAM) was tested as a novel corrosion inhibitor for mild steel in 0.5–3 M HCl using chemical and electrochemical techniques at 25–70 °C. The results show that this compound has good corrosion inhibiting properties for mild steel in HCl at very low concentrations. Corrosion inhibition efficiency rises with POCYAM concentration. The adsorption of the POCYAM onto the mild steel surface obeys Langmuir adsorption isotherm model. The inhibition mechanism was further corroborated by the values of thermodynamic parameters obtained from the experimental data.     

Synergistic effect of iodide ions on inhibitive performance of 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole during corrosion of mild steel in 0.5?M sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ solutions by 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole (4-MTH) has been studied using electrochemical impedance spectroscopy (EIS) and the Tafel polarisation method. The results showed that the inhibition efficiency increased with 4-MTH concentration while the potential of desorption (E _d) remained unchanged. The addition of potassium iodide (KI) in the acid solution stabilized the adsorption of 4-MTH molecules on the metal surfaces and, therefore, enhanced the inhibition efficiency of 4-MTH and increased the value of E _d. The synergistic effect was observed between KI and 4-MTH with an optimum mass ratio of [4-MTH]/[KI] = 5/5. The calculated values of synergism parameter (S _θ) from the coverage of the surface were found to be more than unity in most cases. This clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ by 4-MTH. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir’s adsorption isotherm.     

Inhibition of acid corrosion of steel using cetylpyridinium chloride

The cationic surfactant cetylpyridinium chloride (CPC) showed high inhibition efficiency for the corrosion of low carbon steel in 1 M H₂SO₄. Electrochemical measurements were dedicated to test the performance of CPC at different concentrations and temperatures. CPC has a significant inhibiting effect on the corrosion of steel and protection efficiencies up to 97% were measured. The inhibitor shifted the corrosion potential in the cathodic direction. It was found that adsorption is consistent with the Bockris–Swinkels isotherm in the studied temperature range (30–60 °C). The negative values of the free energy of adsorption and the decrease in apparent activation energy in the presence of the inhibitor suggest chemisorption of the CPC molecule on the steel surface.     

Corrosion inhibition of mild steel in sulphuric acid using a bicyclic thiadiazolidine

The inhibitory effect of 3a,6a-diphenyltetrahydro-1H-imidazo [4,5-c] [1, 2, 5] thiadiazole-5(3H)-thione 2,2-dioxide (TTU) on the corrosion behaviour of mild steel in 0.5 M H₂SO₄, at (30 ± 0.5) °C was studied by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy measurements. The effect of inhibitor concentration on the corrosion rate, surface coverage and inhibition efficiency is investigated. Results show that TTU exerts a strong inhibiting effect on mild steel corrosion and acts as a cathodic-type inhibitor. TTU does not affect the mechanism of the cathodic reaction while the anodic reaction mechanism changes upon addition of the inhibitor. Possible mechanistic pathways for the inhibition process are proposed. The inhibition efficiency of TTU may be due to either the adsorption of inhibitor molecules building a protective film or the formation of an insoluble complex of the inhibitor with metal cations. TTU adsorption obeys the Langmuir model.     

Inhibition of mild steel corrosion in the presence of fatty acid triazoles

The influence of some fatty acid triazoles namely, 4-Phenyl-5-undecyl-4H- [1,2,4] triazole-3-thiol (PUTT), 5-Heptadec-8-enyl-4-phenyl-4H- [1,2,4] triazole-3-thiol (HPTT), and 5-Dec-9-enyl-4-phenyl-4H- [1,2,4] triazole-3-thiol (DPTT) on the corrosion of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulfuric acid (H₂SO₄) was studied by weight loss and potentiodynamic polarization methods. The values of activation energy and free energy of adsorption of all the triazoles were calculated to investigate the mechanism of corrosion inhibition. The potentiodynamic polarization studies were carried out at room temperature, according to which all the compounds were mixed type inhibitors and inhibit the corrosion of mild steel by blocking the active sites of the metal. The adsorption of all the triazoles on mild steel surface in both the acid solutions was found to obey the Langmuir adsorption isotherm. All the compounds showed good inhibition efficiency in both acids. The inhibition efficiency of the compounds was found to vary with their nature and concentration, solution temperature and immersion time. Electrochemical impedance spectroscopy was also used to investigate the mechanism of the corrosion inhibition.     

Hector bases – a new class of heterocyclic corrosion inhibitors for mild steel in acid solutions

Three heterocyclic compounds namely 3-anilino-5-imino-4-phenyl-1, 2,4-thiadiazoline (AIPT), 3-anilino-5-imino-4-tolyl-1, 2,4-thiadiazoline (AITT), and 3-anilino-5-imino-4-chlorophenyl-1, 2,4-thiadiazoline (AICT) were synthesized and their influence on the inhibition of corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ was investigated by weight loss and potentiodynamic polarization techniques. The values of activation energy and free energy of adsorption of these compounds were also calculated. Potentiodynamic polarization studies were carried out at room temperature, and showed that all the compounds were mixed type inhibitors causing blocking of active sites on the metal. The inhibition efficiency of the compounds was found to vary with concentration, temperature and immersion time. Good inhibition efficiency was evidenced in both acid solutions. The adsorption of the compounds on mild steel for both acids was found to obey the Langmuir adsorption isotherm. Electrochemical impedance spectroscopy was also used to investigate the mechanism of corrosion inhibition.     

Corrosion inhibitory action of Commiphora caudata extract on the mild steel corrosion in 1 M H2SO4 acid medium

Corrosion inhibitory action of Commiphora caudata extract on the mild steel corrosion in 1 M H₂SO₄ acid medium is investigated by weight loss and electrochemical studies. The weight loss method shows that the inhibition efficiency increases with the increase of inhibitor concentration, time, and temperature. The polarization studies reveal that the extract acts as a mixed type inhibitor. In electrochemical impedance measurement, the semicircle curves indicated that the charge transfer process controlled the corrosion of mild steel. Thermodynamic parameter such as free energy value was negative, that indicates spontaneous adsorption of inhibitor on mild steel surface. In the presence of inhibitor decreases the activation energy value which shows the chemical adsorption. The Commiphora caudata extract is found to obey Langmuir adsorption isotherm. Scanning electron microscopy, FTIR, and Quantum chemical studies confirmed that the mild steel protect from the corrosion by adsorption of the inhibitor molecules on surface of metal.     

Biomaterials for corrosion protection: evaluation of mustard seed extract as eco-friendly corrosion inhibitor for X60 steel in acid media

The toxic nature of most organic and inorganic corrosion inhibitors has necessitated the search for corrosion inhibitors with an excellent environmental profile. The present work is focused on the widening utilization of plant extracts for metallic corrosion control and reports on the corrosion inhibition effect of mustard seed extract (MSE) for typical X60 pipeline steel in 2 M HCl and 1 M H₂SO₄ solutions. Gravimetric and electrochemical (electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization) methods were employed. The effect of immersion time and temperature on the corrosion inhibition effect of the plant extract was also studied. Results obtained show that MSE inhibited the corrosion of steel in both media which was more pronounced in H₂SO₄ than in HCl environment. Inhibition efficiency increased with increase in the concentration of the extract but decreased with increase in temperature. The potentiodynamic polarization studies revealed that MSE functions as a mixed-type inhibitor. The corrosion inhibition is assumed to occur via adsorption of the components of the extract on the steel surface which was found to obey Langmuir adsorption isotherm model. The morphology of the corroding steel surface in the absence and presence of the MSE was visualized using scanning electron microscopy.     

Joint effect of halides and ethanol extract of <Emphasis Type="Italic">Lasianthera africana</Emphasis> on inhibition of corrosion of mild steel in H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

Inhibitive and adsorption properties of ethanol extract of Lasianthera africana for inhibition of corrosion of mild steel in H₂SO₄ were studied using gravimetric, thermometric, gasometric, and infrared (IR) methods. The extract was found to be a good inhibitor of corrosion of mild steel in H₂SO₄. Inhibitive properties of the extract were attributed to enhancement in adsorption of the inhibitor on mild-steel surface by saponin, alkaloid, tannin, flavanoid, cardiac glycoside, and anthraquinone (present in the extract). Also, adsorption of the inhibitor was found to be exothermic, spontaneous, and consistent with assumptions of Langmuir and Temkin adsorption isotherms. Synergistic study revealed that, of the investigated halides, only KCl may enhance adsorption of the inhibitor, whereas KBr and KI antagonized its adsorption. Based on the decrease in efficiency of the inhibitor with temperature, with values of activation energy and free energy of adsorption below the threshold values of −40 and 80 kJ mol⁻¹, respectively, a physical adsorption mechanism has been proposed for adsorption of ethanol extract of Lasianthera africana on the surface of mild steel.     

Studies on the influence of iodide ions on the synergistic inhibition of the corrosion of mild steel in an acidic solution

The synergistic action caused by iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂S0₄ in the presence of dicyclohexylamine (DCHA) has been investigated using potentiodynamic polarization, linear polarization and a.c. impedance techniques. DCHA inhibits the corrosion of mild steel in 0.5 m H₂SO₄ even at lower concentrations. The inhibition efficiency decreases with increase in the concentration of the amine. The addition of iodide ions enhances the inhibition efficiency to a considerable extent. The adsorption of this compound is also found to obey Langmuir's adsorption isotherm, thereby indicating that the main process of inhibition is by adsorption. The increase in surface coverage values in the presence of iodide ions indicates that DCHA forms an insoluble complex at lower amine concentrations by undergoing a joint adsorption. The synergism parameter (S) is defined and calculated both from inhibition efficiency and surface coverage values. This parameter in the case of DCHA is found to be more than unity, indicating that the enhanced inhibition efficiency caused by the addition of iodide ions is only due to synergism and there is a definite contribution from the inhibitor molecule. Thus, DCHA is then adsorbed by coulombic attraction on the metal surface where the I^– is already chemisorbed and thus reduces the corrosion rate.     

Effect of iodide ions on corrosion inhibition of mild steel by 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole in sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M sulfuric acid (H₂SO₄) in the presence of 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) was investigated using weight loss measurements and different electrochemical techniques such as potentiostatic polarization curves and electrochemical impedance spectroscopy (EIS). The inhibition efficiency (E, %) increased with 4-MTHT concentration, but the desorption potential (E _d) remained unchanged with increasing 4-MTHT concentration. The addition of potassium iodide (KI) enhanced E considerably and increased the value of E _d. A synergistic effect was observed between KI and 4-MTHT with an optimum mass ratio of [4-MTHT]/[KI] = 4 × 10^–2. The synergism parameters (S ) calculated from surface coverage were found to be more than unity. This result clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ by 4-MTHT. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir's adsorption isotherm.     

INHIBITION OF MILD STEEL CORROSION IN H2SO4 USING EXUDATE GUM FROM PACHYLOBUS EDULIS AND SYNERGISTIC POTASSIUM HALIDE ADDITIVES

The corrosion inhibitive effects of Pachylobus edulis exudate gum for mild steel in 2 M H₂SO₄ and influence of potassium halide additives on the inhibition efficiency were investigated using hydrogen evolution and thermometric methods at 30°–60°C. Inhibition efficiency was determined by comparing the corrosion rates in the absence and presence of additives. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition. It was found that the exudate gum acts as an inhibitor for acid-induced corrosion of mild steel. Inhibition efficiency (%I) of the exudate gum increased with an increase in concentration of the exudate gum and synergistically increased on addition of potassium halides but decreased with increase in temperature. Inhibitor adsorption characteristics were approximated by Temkin adsorption isotherm at all the concentrations and temperatures studied. The phenomenon of physical adsorption is proposed from the activation parameters obtained.     

INHIBITION OF MILD STEEL CORROSION IN SULFURIC ACID MEDIUM BY HYDROXYETHYL CELLULOSE

The inhibitive effect of hydroxyethyl cellulose (HEC) on mild steel corrosion in aerated 0.5 M H₂SO₄ solution was studied using gravimetric and electrochemical techniques. The effect of temperature on corrosion and inhibition was also investigated. The results show that hydroxyethyl cellulose functioned as a good inhibitor in the studied environment and inhibition efficiency increased with concentration of inhibitor. Potentiodynamic polarization measurements revealed that HEC inhibited both the cathodic and anodic partial reactions of the corrosion processes. Impedance results clearly show that HEC inhibited the corrosion reaction by adsorption onto the metal/solution interface by significantly decreasing the double layer capacitance (C _dl ). This result was greatly pronounced in the presence of the inhibitor system (HEC + KI) that contains halide additive. Temperature studies revealed an increase in inhibition efficiency with rise in temperature. The adsorption behavior was found to obey the Freundlich isotherm. The values of activation energy, heat of adsorption, and standard free energy suggest that there was transition from physical to chemical adsorption mechanism of HEC on the mild steel surface. Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency.