Corrosion inhibition of carbon steel in hydrochloric acid by furan derivatives

The efficiency of three furan derivatives (2-methylfuran, furfuryl alcohol and furfurylamine), as corrosion inhibitors for carbon steel in 1 M HCl, has been determined by gravimetric and electrochemical measurements. These compounds inhibit corrosion even at very low concentrations, and furfuryl alcohol is the best inhibitor. Polarization curves indicate that all compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. Adsorption of furan derivatives on the carbon steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. The structural and electronic properties of these inhibitors, obtained using AM1, PM3, MNDO and MINDO/3 semi-empirical self-consistence field methods, are correlated with their experimental efficiencies.     

Corrosion inhibition of carbon steel in hydrochloric acid by some polyethylene glycols

The inhibition effect of some PEGs on carbon steel corrosion at 25 °C in 0.5N hydrochloric acid as corroding solution was evaluated by weight loss method and polarization and electrochemical impedance spectroscopy (EIS) techniques. In order to study the effect of polyethylene glycols’ structure on the inhibition efficiency, different molecular weights (400, 1000, 4000, and 10,000 g mol⁻¹) were selected. This work has demonstrated that polyethylene glycols have inhibition effect on corrosion process and their inhibition efficiencies are between 50 and 90%. The inhibition efficiencies are increased by increase of the inhibitors’ concentration and molecular weight.     

Corrosion inhibition of mild steel in 1.0 M hydrochloric acid medium by new photo-cross-linkable polymers

Photo-cross-linkable polymers namely, poly((E)-(1-(5-(4-(3-(4-chlorophenyl)-3-oxoprop-1-enyl)phenoxy)pentyl)-1H-1,2,3-triazol-4-yl)methyl acrylate) (Cl-5) and poly((E)-(1-(5-(4-(3-(4-chlorophenyl)-3-oxoprop-1-enyl)phenoxy)decyl)-1H-1,2,3-triazol-4-yl)methyl acrylate) (Cl-10) were synthesized by click-chemistry. The polymers were characterized by using various spectroscopic techniques and the rate of cross-linking was evaluated by absorption spectroscopy. The inhibitory action of the photo-cross-linkable polymers was evaluated for mild steel (MS) corrosion in 1.0 M hydrochloric acid solution (HCl) by means of electrochemical impedance spectroscopy, potentiodynamic polarization measurements, adsorption isotherms and surface analysis. To the best of our knowledge, these are the most efficient inhibitors (Cl-5 and C-10) for the corrosion of MS in HCl reported so far. Tafel polarization measurements showed that the polymers act as mixed type inhibitors and the adsorption of the inhibitors onto the MS surface followed the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption (ΔG_ads) strongly supported spontaneous physicochemical adsorption of inhibitor molecules on the MS surface. The SEM-EDX results confirmed that the cross-linked polymers inhibited the corrosion to a greater extent than the intact polymer.     

Corrosion inhibition of mild steel by alkylimidazolium ionic liquids in hydrochloric acid

The acid corrosion inhibition process of mild steel in 1 M HCl by 1-butyl-3-methylimidazolium chlorides (BMIC) and 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄) has been investigated using electrochemical impedance, potentiodynamic polarization and weight loss measurements. Potentiodynamic polarization studies indicate the studied inhibitors are mixed type inhibitors. For both inhibitors, the inhibition efficiency increased with increase in the concentration of the inhibitor and the effectiveness of the two inhibitors are in the order [BMIM]HSO₄ > BMIC. The adsorption of the inhibitors on mild steel surface obeyed the Langmuir's adsorption isotherm. 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 standard free energy of adsorption (ΔG_ads) were calculated to elaborate the mechanism of corrosion inhibition.     

盐酸介质中头孢硫脒对碳钢的缓蚀作用

采用动电位极化曲线和交流阻抗实验,研究了抗生素——头孢硫脒的缓蚀剂在盐酸介质中对碳钢的缓蚀性能和缓蚀作用机理。结果表明,头孢硫脒对碳钢在1.0 mol/L盐酸溶液中具有良好的缓蚀性能,当头孢硫脒浓度为0.4 mmol/L时,缓蚀率达86%以上,为抑制阴极反应为主的混合型缓蚀剂。头孢硫脒在碳钢表面的吸附符合Langmuir等温式,属于单分子层吸附,其吸附行为是以化学吸附为主的物理和化学混合吸附。     

12-Aminododecanoic acid as a corrosion inhibitor for carbon steel

The inhibiting effect of 12-aminododecanoic acid (AA) on corrosion of carbon steel (CS) was investigated in hydrochloric acid of different pH, temperatures and over a prolonged period of time, and also in some other selected corrosive solutions. It was found that AA inhibits both partial corrosion reactions, with a slightly stronger inhibition of the anodic corrosion reaction. The corrosion protection mechanism is by formation of a surface-adsorbed AA monolayer that offers a hydrophobic barrier to transport of solvated corrosive ions to the surface. A maximum inhibition efficiency of 98.8 ± 0.5% was achieved in 0.5 M HCl. The adsorption of AA onto the CS surface was described by the Langmuir adsorption isotherm. The corresponding standard Gibbs energy of adsorption was calculated to be −26 kJ mol⁻¹. Polarization modulation infrared reflection absorption spectroscopy measurements revealed that the adsorbed AA monolayer is amorphous, which is due to the high heterogeneity of the CS surface.     

Corrosion inhibition performance of 2-mercaptobenzimidazole and 2-mercaptobenzoxazole compounds for protection of mild steel in hydrochloric acid solution

The effect of some mercapto functional azole compounds on the corrosion of mild steel in 1 M hydrochloric acid solution was studied by polarization and electrochemical impedance spectroscopy (EIS). Polarization studies showed depression of cathodic and anodic polarization curves in the presence of mercapto functional azole compounds, indicating mixed type corrosion inhibition of the compounds. Double layer capacitance and charge transfer resistance values were derived from EIS results. Changes in impedance parameters are indicative of adsorption of these compounds on the metal surface. Surface analysis SEM/EDX showing presence of sulfur on the surface confirmed the adsorption of the azole compounds on the mild steel surface as showed by electrochemical methods. Both compounds contain a pyridine-like nitrogen atom and a sulfur atom in their molecular structure, while they differ in only one heteroatom: oxygen in the oxazole ring and pyrrole-like nitrogen in the imidazole ring. The results of the electrochemical techniques revealed that changing the pyrrole like nitrogen atom to oxygen atom in the azole ring results in a decrease of corrosion inhibition performance in hydrochloric acid solution, which could be related to more negative charge on pyrrole-like nitrogen atom in comparison to oxygen atom as depicted by quantum chemical calculations.     

Evaluation of some bipyridinium dihalides as inhibitors for low carbon steel corrosion in sulfuric acid solution

Inhibition of low carbon steel (LCS) corrosion in 0.5 M H₂SO₄ solution by three bipyridinium dihalides (TMbPyBr₂, HMbPyBr₂ and MPhbPyCl₂) was evaluated by potentiodynamic polarization curves, EIS and SEM techniques. The effectiveness of the inhibitors is ranked as follows: MPhbPyCl₂ ≅ TMbPyBr₂ > HMbPyBr₂. The compounds behave as mixed-type inhibitors and their adsorption on the steel surface obeys the Langmuir adsorption isotherm. EIS measurements indicate that charge transfer controls the corrosion of steel in the absence and presence of the inhibitors and the equivalent circuit R_e(R_ctQ_dl) represents the electrode/solution interface either at the corrosion potential or at −75 and 30 mV versus E_corr. The compounds show maximum inhibition efficiency at 35 °C. The mechanism of corrosion inhibition was discussed in the light of the molecular structure of the bipyridinium salts.     

Experimental and theoretical study on amino acid derivatives as eco-friendly corrosion inhibitor on mild steel in hydrochloric acid solution

Amino acid derivatives, namely, 2-(2-oxo-2-phenothiazin-10-yl)ethylamino)-3-mercaptopropanoic acid (OPEM) and 2-(2-oxo-2-phenothiazin-10-yl)ethylamino)acetic acid (OPEA) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using the weight loss, polarization, and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiency of both the inhibitors increased with increasing the temperature and concentration of inhibitor. The inhibitors OPEM and OPEA show corrosion inhibition efficiency of 97.5 and 95.8%, respectively, in 200?ppm concentration, at 333?K. Polarization studies showed that both studied inhibitors were of mixed type in nature. The adsorption of inhibitors on the mild steel surface obeys Langmuir adsorption isotherm and the surface of inhibited and uninhibited specimens were analyzed by scanning electron microscopy (SEM). The semiempirical AM1 method was employed for theoretical calculations and the obtained results were found to be consistent with the experimental findings.     

Corrosion inhibition of mild steel in neutral aqueous solution by new triazole derivatives

Selected triazole derivatives have been synthesised and evaluated as corrosion inhibitors for mild steel in natural aqueous environment by weight loss, potentiodynamic polarisation and ac impedance methods. All the condensed products showed good inhibition efficiency (IE). The effect of changing functional groups of some triazole derivatives on their inhibition efficiency was also reported using weight loss and potentiodynamic technique. 3-Salicylalidene amino-1,2,4-triazole phosphonate (SATP) was found to be the best corrosion inhibitor compare to the other compounds. Surface analysis was carried out to establish the mechanism of corrosion inhibition of mild steel in neutral aqueous media.     

Corrosion inhibition of mild steel in sulfamic acid solution by S-containing amino acids

R_p, potentiodynamic polarization curves and EIS techniques were applied to study the effect of five S-containing amino acids on the corrosion of mild steel in 5% sulfamic acid solution at 40 °C. The compounds are effective inhibitors and the inhibition efficiency follow the order: N-acetylcysteine (ACC) > cysteine (RSH) > S-benzylcysteine (BzC) > cystine (RSSR) ≅ methionine (CH₃SR). The inhibitors affect the anodic dissolution of steel by blocking the anodic sites of the surface. EIS measurements indicated that charge transfer is the rate determining step in the absence and presence of the inhibitors and the steel/solution interface can be represented by the equivalent circuit R_s(R_ctQ_dl). Adsorption of RSH, CH₃SR and RSSR follows the Langmuir model while the Temkin isotherm describes the adsorption of ACC and BzC. From the application of the Flory–Huggins isotherm, the number of water molecules displaced by the adsorbing inhibitor molecules was estimated. The potential of zero charge pzc of mild steel without and with the inhibitors is calculated and the mechanism of corrosion inhibition is discussed in the light of the molecular structure.     

Corrosion inhibition of mild steel in acidic medium using hydrazide derivatives

The corrosion inhibition characteristics of N′-[(1E)-(4-hydroxy phenyl) methylene] isonicotinohydrazide (HIH) & N′-[(1E)-(4-hydroxyl-3-methoxy phenyl) methylene] isonicotinohydrazide (HMIH) on mild steel corrosion in 1 M hydrochloric acid were investigated by weight loss, potentiodynamic polarization and impedance techniques. The inhibition efficiency increased with increase in inhibitor concentration but decreased with increase in temperature. The thermodynamic functions of dissolution and adsorption processes were evaluated. The polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the compounds was found to obey Langmuir’s adsorption isotherm. Passive film characterization was done by Fourier transform infrared (FTIR) spectra and scanning electron microscopy (SEM).     

Electrochemical and quantum chemical study of purines as corrosion inhibitors for mild steel in 1 M HCl solution

The purines and its derivatives, such as, guanine, adenine, 2,6-diaminopurine, 6-thioguanine and 2,6-dithiopurine, were investigated as corrosion inhibitors for mild steel in 1 M HCl solution by weight loss measurements, electrochemical tests and quantum chemical calculations. The polarization curves of mild steel in the hydrochloric acid solutions of the purines showed that both cathodic and anodic processes of steel corrosion were suppressed. The Nyquist plots of impedance expressed mainly as a depressed capacitive loop with different compounds and concentrations. For all these purines, the inhibition efficiency increased by increasing the inhibitor concentration, and the inhibition efficiency orders are 2,6-dithiopurine > 6-thioguanine > 2,6-diaminopurine > adenine > guanine with the highest inhibiting efficiency of 88.0% for 10⁻³ M 2,6-dithiopurine.The optimized structures of purines, the Mulliken charges, molecular orbital densities and relevant parameters were calculated by quantum chemical calculations. The quantum chemical calculation results inferred that the adsorption belong to physical adsorption, which might arise from the π stacking between the π electron of the purines and the metal surface.     

Electrochemical frequency modulation as a new technique for monitoring corrosion inhibition of iron in acid media by new thiourea derivative

The electrochemical frequency modulation EFM technique provides a new tool for electrochemical corrosion monitoring. EFM is a non-destructive technique as electrochemical impedance spectroscopy (EIS). EFM technique was used in comparison with the traditional dc and ac techniques. Results obtained by EFM technique were shown to be in agreement with other electrochemical techniques. With EFM technique, a corrosion rate can be obtained instantaneously in very short time which makes this technique ideal in online corrosion monitoring. New synthesized thiourea derivative named 1,3-diarylidenethiourea (DAT) was examined as a new corrosion inhibitor for iron in 1 M hydrochloric acid solution.     

Physiochemical interactions of chiral Schiff bases on high carbon steel surface: Corrosion inhibition in acidic media

(S)1-N-(1-hydroxy-1,1-diphenyl-3-methylbut-2-yl)-2-hydroxybenzaldimine (DPV) and (S)1-N-(1-hydroxy-3-methylbut-2-yl)-2-hydroxybenzaldimine (LV) were synthesized and investigated as inhibitors for the corrosion of the high carbon steel (HCS) in 1.0 M HCl by electrochemical measurements. According to the electrochemical methods, inhibitor DPV showed higher efficiency in comparison to that of LV. The Tafel polarization method revealed the mixed-mode inhibition of chiral Schiff bases with predominant control of the anodic reaction. The adsorption of the inhibitor molecules onto the HCS surface was found to follow the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption strongly supported spontaneous physicochemical adsorption of inhibitor molecules on the HCS surface. The adsorption mechanism for inhibition was supported by Fourier transforms infrared (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy–energy-dispersive X-ray (SEM–EDS) spectroscopic methods, and adsorption isotherms.     

Corrosion inhibition effect of pyrazole derivatives on mild steel in hydrochloric acid solution

Synthesized compounds, namely methyl 5-(4-Chlorobenzoyloxy)-1-phenyl-1H-pyrazole-3-carboxylate (MCPPC) and 5-(4-methoxyphenyl)-3-(4-methylphenyl)4,5-dihydro-1H-pyrazol-1-yl-(pyridin-4-yl)methanone (MMDPPM) were investigated as corrosion inhibitor for mild steel (MS) in 15% HCl solution using weight loss measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. Inhibition efficiency was found concentration-dependent and increased by increasing the concentration of MCPPC and MMDPPM. Both of inhibitors were efficient even at a very low concentration of 25 ppm. The inhibitors MCPPC and MMDPPM showed inhibition efficiency of 67.1 and 76.8%, respectively, at 25 ppm, whereas it was 92.0 and 95.9%, respectively, at 250 ppm concentration at 303 K. The potentiodynamic polarization curves showed that MCPPC and MMDPPM act as mixed-type inhibitor in 15% HCl solution. The Nyquist plots showed that charge transfer resistance increased and double-layer capacitance decreased on increasing the concentration of studied inhibitors due to adsorption of inhibitor molecules on MS surface. The adsorption of each inhibitor on MS surface obeys Langmuir adsorption isotherm. On the basis of thermodynamic adsorption parameters, mixed-type adsorption (physisorption and chemisorption) for the studied inhibitors on MS surface was suggested. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM) analyses confirmed the existence of a protective film of the inhibitor on MS surface. The density functional theory was employed for theoretical calculations, and the obtained results were found to be consistent with the experimental findings.     

Electrochemical behavior of organic and inorganic complexes of Zn(II) as corrosion inhibitors for mild steel: Solution phase study

This work intends to study inhibitive performance of organic and inorganic complexes of Zn(II) using electrochemical techniques along with surface analysis. In this regard, inorganic zinc aluminum polyphosphate pigment as modified zinc phosphate and zinc acetylacetonate and benzimidazole mixture representing organic replacement of zinc phosphate were employed. Through taking advantage of electrochemical impedance spectroscopy and DC polarization, two mentioned approaches were indicated to be efficient. Charge transfer resistance and corrosion current density values exhibited superiority of zinc aluminum polyphosphate and mixture of zinc acetylacetonate and benzimidazole compared to zinc phosphate and also zinc acetylacetonate and benzimidazole as individual inhibitors. Corrosion inhibition efficiencies calculated based on charge transfer resistance in consistent with those calculated from corrosion current density showed the following sequence; zinc aluminum polyphosphate > mixture of zinc acetylacetonate and benzimidazole > zinc acetylacetonate > zinc phosphate > benzimidazole. Showing film formation, surface analysis SEM/EDX confirmed the results obtained by electrochemical methods.     

盐酸介质中吐温-60对冷轧钢的缓蚀作用机理

用失重法及电化学法研究了非离子表面活性剂吐温-60对冷轧钢在1.0～8.0 mol•L^-1盐酸溶液中的缓蚀作用. 结果表明：吐温-60对冷轧钢在1.0 mol•L^-1盐酸溶液中具有良好的缓蚀作用,且其在钢表面的吸附符合Langmuir吸附模型. 缓蚀率随缓蚀剂浓度的增加而增大,但随盐酸浓度和温度的增加而减小. 动电位极化曲线表明,吐温-60为混合抑制型缓蚀剂,但主要是抑制阴极反应. 通过吸附理论和动力学公式求出了相应的吸附热力学参数和动力学参数,并根据这些参数详细讨论了缓蚀作用机理.     

BMAT对碳钢或不锈钢在多种腐蚀介质中的缓蚀作用

用失重法和极化曲线法研究了苯并咪唑类化合物（ＢＭＡＴ） 对碳钢或不锈钢在醋酸、硫酸、盐酸－ 氢氟酸－ 磷酸、自来水等腐蚀介质中的抑制作用,结果表明ＢＭＡＴ 能抑制由于Ｈ＋ 的去极化而引起的各种酸的腐蚀,并可提高不锈钢在含Ｃｌ－ 自来水中的抗点蚀能力．     

Advanced quantum chemical and electrochemical analysis of ravage drugs for corrosion inhibition of mild steel

The blocking of corrosive sites of soft (mild) steel has been studied using ravage drugs Pyrazinamide (Z), Isoniazid (H) and Rifampicin (R) in 0.5?M HCl medium. The degree of ability of these drugs to act as corrosion controlling agents was investigated by gravimetric measurements, potentiostatic polarization and electrochemical impedance spectroscopy. Their inhibition efficacy has, further been validated through theoretical and simulation studies. Though, all the drugs have shown good anticorrosive impact, but, rifampicin (R) has proven its greater efficacy as 97.06% at 1000?ppm and at 303?K. Polarization curves depict that the H and R drugs act through mixed mode of inhibition while Z drug is predominantly anodic in nature. The result of electrochemical impedance spectroscopy specifies that the corrosion reaction is resisted by charge transfer process. Morphology of un-corroded and corroded coupons was studied by scanning electron microscopy. The mechanism of adsorption is obeyed well through Langmuir isotherm and advocated a significant physiochemical type of interaction by the compounds on the metal surface. Thus, all the findings got via various experimental techniques along with that of obtained using Molecular Dynamics (MD) and Density Functional Theory (DFT) for the three compounds are in proper harmony.