Computational and electrochemical studies on the inhibition of corrosion of mild steel by <Emphasis Type="SmallCaps">l</Emphasis>-Cysteine and its derivatives

This article presents the investigation of l-Cysteine (CYS) and its derivatives including N-Acetyl-l-Cysteine (NACYS), N-Acetyl-S-Benzyl-l-Cysteine (NASBCYS), and N-Acetyl-S-Hexyl-l-Cysteine (NASHCYS) as green chemical corrosion inhibitors for mild steel in 1 M HCl solutions. Weight loss method and Tafel polarization measurement were performed to determine the corrosion parameters and inhibition efficiencies. Experimental results showed that these compounds suppressed both anodic and cathodic reactions, and the inhibition efficiency of the four inhibitors followed the order NASBCYS > NASHCYS > NACYS > CYS. In order to further study the corrosion mechanisms, quantum chemical calculation and molecular dynamics method were applied. The relationships between quantum chemical parameters and corrosion inhibition efficiency were discussed. Molecular dynamics method was used to simulate the adsorption behavior of each inhibitor in solvent. The results showed that these four inhibitors can adsorb on mild steel surface by donor acceptor interactions between lone-pair electrons of heteroatoms/π-electrons of aromatic ring and vacant d-orbital of iron.     

<Emphasis Type="SmallCaps">l</Emphasis>-Tryptophan as green corrosion inhibitor for low carbon steel in hydrochloric acid solution

The inhibition behavior of low carbon steel in 1 M HCl by l-tryptophan was investigated with weight loss experiment and Tafel polarization curve in the used temperature range (298–328 K). All the experimental results show that l-tryptophan has excellent corrosion inhibition performance and the most effective concentration of inhibitor is 1 × 10⁻² mol L⁻¹. The Tafel polarization curve results indicate that l-tryptophan acts more as a cathodic than anodic inhibitor. The adsorption of l-tryptophan on the surface of low carbon steel obeys the Langmuir adsorption isotherm, and the thermodynamic parameters were determined and discussed. The adsorption behavior of l-tryptophan at Fe surface (1 1 0) was also investigated by the molecule dynamics simulation method and density functional theory. The results indicated that the l-tryptophan could adsorb firmly on the Fe surface through the indole ring with π-electrons and nitrogen/oxygen atom with lone-pair electrons in its molecule.     

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.     

Experimental and quantum chemical studies on corrosion inhibition performance of quinoline derivatives for MS in 1N HCl

The corrosion inhibition effect of two quinoline derivatives, viz, 2-chloro quinoline 3-carbaldehyde (CQC) and (2-chloro-quinoline-3ylmethyl)-p-tolyl-amine (CQA) have been investigated against mild steel (MS) in 1N HCl solution using conventional weight loss, potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy. The losses in weights of MS samples have proved that both CQC and CQA are efficient inhibitors of corrosion. The mixed mode of inhibition was confirmed by electrochemical polarizations. The results of electrochemical impedance spectroscopy have showed changes in the impedance parameters like charge transfer resistance and double-layer capacitance that confirmed strong adsorption of inhibitors on the MS surface. The inhibition action of these compounds was assumed to occur via adsorption on the steel surface through the active centres contained in the molecules. Furthermore, quantum chemical calculations have been performed at B3LYP/6-31G(d, p) level to complement the experimental evidence.     

Corrosion inhibition of carbon steel and antibacterial properties of aminotris-(methylenephosphonic) acid

In this work, the corrosion inhibition property and the antibacterial activity of the aminotris-(methylenephosphonic) acid (ATMP) have been studied. ATMP has been evaluated as a corrosion inhibitor for carbon steel in 1 M HCl solution using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. According to the experimental results, the inhibition efficiency increased with increasing inhibitor concentration. Tafel polarization study showed that the ATMP acts as a mixed inhibitor. Data, obtained from EIS measurements, were analyzed to model the corrosion inhibition process through appropriate equivalent circuit models. Adsorption of ATMP on the carbon steel surface obeyed the Langmuir adsorption isotherm. The calculated ΔG_ads value showed that the corrosion inhibition of the carbon steel in 1 M HCl is mainly controlled by a physisorption process. In addition, the effect of immersion time on the corrosion of carbon steel was also studied in this work using ac impedance technique. The corrosion inhibition mechanism of ATMP was discussed. This inhibitor can be also used as biocide in aqueous environments. Our results showed that ATMP have an antibacterial effect against both Gram positive and Gram negative bacteria. The lowest MIC (0.2 mg l^?1) was measured for Pseudomonas fluorescens while the highest MIC was measured for Escherichia coli (3.1 mg l^?1). In addition, the results showed that the MIC of ATMP against Listeria innocua in a buffered medium (pH 6.5) was of ca. 4-fold higher than MIC measured in unbuffered medium. Thus, our findings showed that the antibacterial activity of ATMP is a result of a combined effect of the pH solution and the chemical nature of the used phosphonate molecule.     

The inhibition of mild steel corrosion in hydrochloric acid media by two Schiff base compounds

Schiff bases of 2-({-1-methyl-3-[(2-sulfanylphenyl)imino]butylidene}-amino)-1-benzenethiol and 2-({-1,2-diphenyl-2-[(2-sulfanylphenyl)imino]ethylidene}amino)-1-benzenthiol are investigated as corrosion inhibitors in acid solution. Polarization, electrochemical impedance spectroscopy, and weight loss measurements were performed on mild steel in 15% HCl with and without the inhibitors. A significant decrease in the corrosion rate of mild steel was observed in the presence of investigated inhibitors. Polarization curves indicate that both compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. The adsorption of inhibitors on mild steel surface in 15% HCl was found to follow Langmuir adsorption isotherm. Thermodynamic adsorption parameters (K _ads, ∆G _ads) of studied Schiff bases were calculated using the Langmuir adsorption isotherm. Activation parameters of the corrosion process such as activation energies, E _a, activation enthalpies, ∆H*, and activation entropies, ∆S*, were calculated by the obtained corrosion currents at different temperatures.     

Inhibition of mild steel corrosion in sulfuric acid by some newly synthesized organic compounds

The corrosion inhibition of mild steel in 0.5 M sulfuric acid solutions by some new synthesized organic compounds namely (E)-2-acetyl-3-(butyl amino)-N-phenyl buten-2-thioamide (compound A), (E)-3-(4-(dimethyl amino) phenyl amino)-2-acetyl-N-phenyl buten-2-thioamide (compound B) and (E)-3-(2,3-dimethyl phenyl amino)-2-acetyl-N-phenyl buten-2-thioamide (compound C) was investigated using weight loss and potentiostatic polarization techniques. These measurements reveal that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follows the order A > B > C. Polarization studies show that these compounds are of the mixed-type but dominantly act as an anodic inhibitors for steel in 0.5 M H₂SO₄ solutions. These inhibitors function through adsorption following Langmuir isotherm. Activation energy and Gibbs free energy for adsorption of inhibitors are calculated. Molecular modeling has been conducted to correlate the corrosion inhibition properties with the calculated quantum chemical parameters.     

Inhibition of corrosion of mild steel in acid media by N′-benzylidene-3-(quinolin-4-ylthio)propanohydrazide

In the present investigation a new corrosion inhibitor, N′-(3,4-dihydroxybenzylidene)-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide(DHBTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl (1 M, 2 M) and H₂SO₄ (0·5 M, 1 M) solutions using weight-loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The corrosion inhibition efficiency measured by all the above three techniques were in good agreement with each other. The results showed that DHBTPH is a very good inhibitor for mild steel in acidic media. The inhibition efficiency in different acid media was found to be in the decreasing order 0·5 M H₂SO₄ > 1 M HCl > 1 M H₂SO₄ > 2 M HCl. The inhibition efficiency increases with increasing inhibitor concentration and with increasing temperature. It acts as an anodic inhibitor. Thermodynamic and activation parameters are discussed. Adsorption of DHBTPH was found to follow the Langmuir’s adsorption isotherm. Chemisorption mechanism is proposed. The mild steel samples were also analysed by scanning electron microscopy (SEM).     

Naturally Occuring Organic Substances as Corrosion Inhibitors for mild steel in acid medium

Inhibition of the corrosion of mild steel in H₂SO₄ by amino acids was studied by measuring the Tafel polarization curves. Nineteen different naturally occuring amino acids were used as corrosion inhibitors. Two-site adsorption model was proposed to explain the adsorption of some amino acids on the metal surface. At 1 × 10^?4M concentration of inhibitor, the best corrosion inhibition was obtained with the sulphur-containing amino acids. Other amino acids gave various corrosion inhibition efficiency depending or their structure.     

Electrochemical and quantum chemical study of 4-[(E)-[(2,4-dihydroxy phenyl) methylidine] amino]-6-methyl-3-sulphanylidine-2,3,4,5-tetra hydro-1,2,4-triazin-5-one [DMSTT]

The inhibition of mild steel in aerated 1 M hydrochloric acid solution was studied using conventional weight loss method, potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), electrochemical impedance spectroscopy (EIS) and quantum chemical calculation in the presence and absence of different concentrations of DMSTT. The inhibition efficiency increased markedly with increase in the additive concentrations, but slightly decreased with increasing temperature. The presence of DMSTT decreases the double layer capacitance and increases the charge-transfer resistance. The value of activation energy (E_a) for mild steel corrosion and thermodynamic parameters such as adsorption equilibrium constant (K_ads), free energy of adsorption (ΔG_ads) values were calculated and discussed. The inhibitor molecule first adsorbed on mild steel surface according to 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.     

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.     

Corrosion inhibition of aluminum in hydrochloric acid solution by alkylimidazolium ionic liquids

The effects of newly synthesized three alkylimidazolium ionic liquids—1-butyl-3-methylimidazolium chlorides (BMIC), 1-hexyl-3-methylimidazolium chlorides (HMIC) and 1-octyl-3-methylimidazolium chlorides (OMIC)—on the corrosion of aluminum in 1.0 M HCl were investigated using potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss methods. All measurements showed that the inhibition efficiency increased with increase in the concentration of inhibitor and the effectiveness of these inhibitors was in the order of OMIC > HMIC > BMIC. Polarization curves revealed that the studied inhibitors were mixed type inhibitors. The adsorption of the inhibitors on the aluminum surface obeyed Langmuir adsorption isotherm and had a physical mechanism. The effect of temperature on the corrosion behavior in the presence of 5 × 10^?3 M of inhibitors was studied in the temperature range of 303–333 K. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpy of activation (ΔH), entropy of activation (ΔS), adsorption equilibrium constant (K_ads) and free energy of adsorption (ΔG_ads) were calculated to elaborate the mechanism of corrosion inhibition.     

酸性盐溶液中复合缓蚀剂对304不锈钢缓蚀作用的研究

为了研究不同缓蚀剂及复合型缓蚀剂对304不锈钢在酸性(pH=1)3.5%氯化钠溶液中的最佳缓蚀效果、最佳复配效果和最佳复配比例,采用失重法、电化学方法、表面形貌观察法、表面接触角和表面张力等表征方法对咪唑、硫脲、铬酸钾这三种物质的缓蚀效果及复配效果进行了研究.结果表明:失重法和表面形貌观察法均显示出三种物质都有一定的缓蚀效果,其缓蚀效率的大小关系为:硫脲铬酸钾咪唑,最佳缓蚀时间为24 h;通过极化曲线Tafel外推法、电化学阻抗谱法和表面形貌观察法等均可得出最佳复配效果为硫脲与铬酸钾复配;将100 ppm的硫脲5 mL和100 ppm的铬酸钾5 mL进行复配时(复配比为1∶1)通过表面接触角和表面张力的方法可得最小接触角为46.5°,最小表面张力71.9 mN/m,故最佳复配比为1∶1,即在硫脲与铬酸钾配比为1∶1且时间为24 h时,这种复合型缓蚀剂对304不锈钢的缓蚀效果最佳.     

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.     

The corrosion inhibition and adsorption behavior of Uncaria gambir extract on mild steel in 1 M HCl

The inhibitive effect of the ethyl acetate extract of Uncaria gambir on the corrosion of mild steel in 1 M HCl solution has been investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The presence of this catechin-containing extract reduces remarkably the corrosion rate of mild steel in acidic solution. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 303–333 K. The results from this corrosion test clearly reveal that the extract behaves as a mixed type corrosion inhibitor with the highest inhibition at 1000 ppm. Surface analyses via scanning electron microscope (SEM) shows a significant improvement on the surface morphology of the mild steel plate. Linearity of Langmuir isotherm adsorptions indicated the monolayer formation of inhibitor on mild steel 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.     

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.     

1mol/L HCl中不同浓度维生素B1和B6对碳钢的缓蚀性能及机理

通过研究盐酸硫胺(维生素B1),吡哆醇(维生素B6)作为缓独剂对碳钢的缓蚀行为及其作用机制,可为新型环境友好缓蚀剂的开发和应用提供一定的理论基础.利用失重法、极化曲线法和交流阻抗法、量子化学方法研究了不同浓度维生素B1和B6在1mol/L盐酸溶液中对Q235碳钢的缓蚀性能及机理.结果表明:碳钢的腐独速率随缓性剂浓度的增...