Studies of protection of iron corrosion by rosin imidazoline self‐assembled monolayers

A type of rosin imidazoline (IM) has been synthesized using rosin acid and diethylenetriamine (DETA) as raw materials. The monolayers of IM were assembled on the surface of iron. The monolayers of the IM inhibitor were characterized by electrochemical impedance spectroscopy (EIS), electrochemical polarization curves and double‐layer capacitance. Surface analysis was carried out to establish the mechanism of corrosion inhibition of iron by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy. The IM inhibitor showed good inhibition efficiency for iron in 0.1 M H₂SO₄. The inhibition mechanism of IM inhibitor was interpreted using molecular simulation. Copyright © 2006 John Wiley & Sons, Ltd.     

向日葵盘果胶对碳钢的缓蚀性能研究

以向日葵盘为原料,利用纤维素酶制备果胶(SFP)。采用静态失重、极化曲线和交流阻抗技术研究SFP在1mol/L HCl及0.5mol/L H_2SO_4溶液中对碳钢的缓蚀性能,并探讨其在碳钢表面的吸附机理。结果表明,缓蚀效率随SFP浓度增大而增大,随温度升高而降低。在HCl和H_2SO_4溶液中,SFP的吸附方式分别服从Langmuir和Temkin等温式,属于物理吸附;极化曲线测试显示SFP是一种混合型缓蚀剂。本文的研究表明,向日葵盘果胶是碳钢的绿色高效缓蚀剂,且在HCl溶液中的缓蚀性能优于在H_2SO_4溶液中。     

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.     

Aqueous extract of Acacia cyanophylla leaves as environmentally friendly inhibitor for mild steel corrosion in 1 M H2SO4 solution

The efficiency of Acacia cyanophylla leaves extract as an environmentally friendly inhibitor for mild steel in aerated aqueous 1 M H₂SO₄ solution has been investigated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy techniques. Addition of inhibitor decreases the corrosion current whereas the corrosion potential values show slight shifts in positive directions. Inhibition efficiency was found to be about 93% (the maximum value was determined from the polarization curve). Efficiencies obtained from both electrochemical techniques are in good agreement. Adsorption of Acacia cyanophylla leaves extract on mild steel surface in 1 M H₂SO₄ solution obeys Langmuir adsorption isotherm. Polarization curves were also obtained at different temperatures in order to measure changes of corrosion rate. Corrosion current increases and inhibition efficiency decreases with temperature increasing in H₂SO₄ solutions with and without Acacia cyanophylla extract. Corrosion parameters also changed with exposure time. Copyright © 2010 John Wiley & Sons, Ltd.     

蛋氨酸衍生物的合成及其缓蚀性能研究

本文合成了一种新型蛋氨酸衍生物酸洗缓蚀剂,运用红外光谱及核磁共振氢谱对其结构进行了鉴定。采用失重法和电化学法研究了在0. 5mol·L~(-1)硫酸介质中其对碳钢试片的缓蚀性能,并通过吸附等温模型对缓蚀机理进行初步的探讨。结果表明,蛋氨酸衍生物的缓蚀效率约为90%,整体用量适中,是一种有望得到良好应用的绿色缓蚀剂。电化学分析表明,蛋氨酸衍生物为混合型缓蚀剂,其通过增大金属表面的电荷转移电阻而降低电化学腐蚀速率。     

Inhibition effect of hexadecyl pyridinium bromide on the corrosion behavior of some austenitic stainless steels in H2SO4 solutions

The inhibition effect of hexadecyl pyridinium bromide (HDPB) as a cationic surfactant on the corrosion behavior of some Egyptian austenitic stainless steel SS 304L, SS 316H and SS 304H in 0.5 M H₂SO₄ solutions was investigated by using potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results indicate that HDPB is a good inhibitor for the samples under investigation in 0.5 M H₂SO₄ solutions. In addition, the inhibition efficiency η% increases with the inhibitor concentration while decreases with the increasing temperature referring to physical adsorption. The adsorption of the inhibitor obeys a Temkin adsorption isotherm. Polarization curves show that HDPB is a mixed inhibitor in H₂SO₄ solutions. The results obtained from polarization and impedance measurements are in good agreement. Activation-free energies, enthalpies, and entropies for the inhibition process of HDPB were determined.     

Corrosion and corrosion inhibition characteristics of bulk nanocrystalline ingot iron in sulphuric acid

The corrosion and corrosion inhibition of bulk nanocrystalline ingot iron (BNII) fabricated from conventional polycrystalline ingot iron (CPII) by severe rolling was studied in 0.5 M H₂SO₄ solution using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The results indicate that BNII was more susceptible to corrosion in the acidic environment essentially because of an increase in the kinetics of the anodic reaction. An amino acid cysteine (cys) was employed as a corrosion inhibitor at concentrations of 0.001 and 0.005 M. Tests in inhibited solutions revealed that cys reduced the corrosion rates of both metal specimens by different mechanisms. For CPII cys inhibited the cathodic reaction but had a stimulating effect on the anodic process at low concentration and a trivial effect at higher concentration. For BNII, cys inhibited both the cathodic and the anodic reactions, although the former effect was more pronounced. Iodide ions improved the inhibitive effect of cys without altering the inhibition mechanism.     

Corrosion inhibition of mild steel by Laurus nobilis leaves extract as green inhibitor

The efficiency of Laurus nobilis leaves?? extract as a corrosion inhibitor for mild steel in acidic medium (1?M H₂SO₄) was investigated by use of the electrochemical techniques potentiodynamic polarization, electrochemical impedance spectroscopy, and polarization resistance measurements. According to the experimental results, L. nobilis extract acts as a good corrosion inhibitor. In the presence of the inhibitor, corrosion potential shifted toward a more negative value than for the blank solution. Inhibitor efficiency increased with increasing inhibitor concentration, as expected. According to the potentiodynamic polarization results the corrosion of mild steel increased with increasing temperature both in the presence and absence of the inhibitor. The activation energy (E _a) of the corrosion process was calculated from the variation of corrosion current density with temperature.     

Corrosion properties of nickel coatings obtained from aqueous and nonaqueous electrolytes

Nickel was deposited on a copper substrate from aqueous and nonaqueous ethanol electrolytes. X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and chronovoltametry, scanning electron microscopy, and atomic force microscopy were used to study the effect of the solvent on the surface and corrosion properties of the Ni coatings formed. Unifom and relatively smooth Ni films were obtained as measured with microscopy techniques. The formation of a passive film in acidic, alkaline, and neutral chloride-containing media was confirmed with X-ray photoelectron spectroscopy. The water-based nickel-plating electrolyte makes it possible to deposit coatings with higher corrosion resistance as compared with coatings deposited from ethanol electrolyte in NaOH and NaCl media. The proposed mechanism of corrosion in a 0.5 M H₂SO₄ solution involves cycles of active-passive surface behavior due to its passivation by corrosion products.     

Inhibitor effect of sodium benzoate on the corrosion behavior of nanocrystalline pure iron metal in near-neutral aqueous solutions

Nanocrystalline iron coating was produced on carbon steel surface by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry and scanning electron microscopy. The electrochemical behavior of nanocrystalline iron coating in the presence of sodium benzoate was evaluated in 30 mg l^-1 NaCl + 70 mg l^-1 Na₂SO₄ aqueous solution using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results were compared with that of the coarse-grained iron surface. The thermodynamic properties of the inhibitor adsorption were also determined. The results indicated that corrosion inhibition of sodium benzoate in near-neutral aqueous solution was increased as the grain size of iron was decreased from micro- to nanocrystalline surface. This was reported in terms of excess free energy of nanocrystalline surface.     

The litchi (Litchi Chinensis) peels extract as a potential green inhibitor in prevention of corrosion of mild steel in 0.5 M H2SO4 solution

The corrosion inhibition of mild steel in 0.5 M H₂SO₄ solution by the extract of litchi peel (Litchi chinensis) was studied by weight loss method, potentiodynamics polarization and electrochemical impedance spectroscopy (EIS). The results show that the litchi peels extract acts as mixed-type inhibitor. The inhibition of corrosion is found to be due to adsorption of the extract on metal surface, which is in conformity with Langmuir’s adsorption isotherm. UV–Vis, Fourier transform infrared (FT-IR) spectroscopy and Scanning electron microscopy (SEM) studies confirm that the inhibition of corrosion of mild steel occurs through adsorption of the inhibitor molecules.     

Experimental and theoretical studies of media effects on copper corrosion in acidic environments containing 2-amino-5-mercapto-1,3,4-thiadiazole

Corrosion behaviour of copper metal in acid solutions (HCl, H₂SO₄ and H₃PO₄) containing 2-amino-5-mercapto-1,3,4- thiadiazole (AMT) was investigated experimentally and theoretically via gravimetric, potentio-dynamic and quantum electrochemical approaches. Similar behavior was observed for H₂SO₄ and H₃PO₄ media, and related to the nature of anions at metal/solution interface. With regard to HCl, however, the rate of corrosion was determined to be low at initial stages, but high later on using an auto-catalyzing mechanism. In the presence of AMT, the experimental studies revealed that this molecule was a good anodic-type inhibitor causing substantial changes in corrosion potential. Moreover, its adsorption obeys the Langmuir isotherm. The values of ΔG _ads were determined and correlated to the inhibitor powers. Finally, the influence of media (anions) on metal corrosion was also investigated from molecular point of view by calculations of the copper-anions interaction using density functional theory.     

Microencapsulation technology for thiourea corrosion inhibitor

The microencapsulation technology was brought in to solidify corrosion inhibitor in order to prolong the releasing time of it. In this work, thiourea (H₂NCSNH₂) was used as a corrosion inhibitor and microcapsuled using glutin and polyvinyl alcohol (PVA), respectively, as protective agent. The re-sealing process was used as a way to prolong the releasing time of the H₂NCSNH₂ encapsulated in microcapsules. It was found that the H₂NCSNH₂ microcapsule corrosion inhibitor using PVA as a protective agent had a better releasing time. The releasing times of the H₂NCSNH₂ microcapsule corrosion inhibitors were prolonged from 18 to 48 h by re-sealing process and using PVA as a protective agent. Both the use of PVA as a protective agent and the application of the re-sealing process decreased the encapsulation efficiency of the H₂NCSNH₂. The performance parameters on protecting Q235 carbon steel from corrosion in 0.1-M H₂SO₄ solution were evaluated by polarization curve and electrochemical impedance spectra methods. The results showed that the H₂NCSNH₂ released into the solution from microcapsules could well protect Q235 carbon steel from corrosion and the corrosion-inhibiting mechanisms of it were the same as that of H₂NCSNH₂.     

Electropolymerization,characterization and corrosion protection evolution of poly(4-aminomethyl-5-hydroxymethyl-2-methylpyridine-3-ol) on steel and copper

The electrochemical synthesis of poly(4-aminomethyl-5-hydroxymethyl-2-methyl pyridine-3-ol) on steel and copper electrodes was achieved in both sulfuric acid and oxalic acid by cyclic voltammetry technique. Characterization of the polymer films were achieved by Fourier transforms infrared spectroscopy technique (FTIR) and scanning electron microscope (SEM). Corrosion performance of coatings was investigated in 0.1 M H₂SO₄ by potentiodynamic polarization and electrochemical impedance (EIS) spectroscopy techniques.     

Effect of H2SO4 Solution Treatment on Adhesion,Charge Transfer,and Catalytic Performance of Screen-Printed PEDOT:PSS

Post-treatment was performed for poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films screen-printed on fluorine-doped tin oxide (FTO) substrates, to improve their charge transfer efficiency. Different H₂SO₄ solutions, including concentrated H₂SO₄ and H₂SO₄ diluted with H₂O or dimethyl sulfoxide (DMSO), were adopted during the post-treatment. The adhesion of the as-treated films was evaluated by adhesive tape peeling tests, the surface morphology and vertical charge transfer from the films to the substrates were investigated by current-sensing atomic force microscopy, and the catalytic activities toward I₃⁻ reduction of PEDOT:PSS films were characterized by electrochemical measurements. It is discovered that selecting proper H₂SO₄ solutions is crucial to improve the charge transfer efficiency and catalytic performance while maintaining reliable adhesion of the film on the substrates, with H₂SO₄/DMSO performing best as the solution for post-treatment. A mechanistic explanationis proposed based on different interactions among solution, PEDOT:PSS, and the substrate for various post-treatment solutions.     

Surface characteristics of anodic oxide films fabricated in acid and neutral electrolytes on Ti–10V–2Fe–3Al alloy

Anodic oxide films were fabricated on Ti–10V–2Fe–3Al alloy in acid (H₂SO₄/H₃PO₄) and neutral environmental friendly (C₄H₄O₆Na₂) electrolytes. The morphology, roughness, crystalline structure of the anodic oxide film were characterized by using scanning electron microscopy, atomic force microscopy, Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results showed that the oxide film fabricated in H₂SO₄/H₃PO₄ electrolyte had a porous structure and the thickness of the film was 3.5 µm. The oxide film fabricated in C₄H₄O₆Na₂ electrolyte presented a nonporous structure that sustained the evident microstructure of the substrate, and the thickness of the film was 6.0 µm. The surface average roughness values of the two types of films were 245 nm and 166 nm, respectively. The phase of the anodic oxide films consisted mainly of anatase and rutile. EIS results showed that the film fabricated in C₄H₄O₆Na₂ electrolyte had higher impedance of the outer layer, while the film fabricated in H₂SO₄/H₃PO₄ electrolyte had higher impedance of the inner layer. Moreover, we attempt to explain the differences in the anodizing kinetics, structure and electrochemical impedance of anodic oxide films by the different films growth processes in the two types of electrolytes. Copyright © 2012 John Wiley & Sons, Ltd.     

Enhancement inhibition efficiency of PBTCA depending on the inclusion complex with hydroxypropyl-β-cyclodextrin

For the first time, hydroxypropyl-β-cyclodextrin (HP-β-CD) has been brought in to include 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) in order to enhance inhibition efficiency of PBTCA, which leads a new approach to study oil–gas field corrosion inhibition in the process of acid treatment. Based on the host–guest inclusion reaction, the inclusion complex of PBTCA with HP-β-CD has been prepared in the laboratory. UV–Vis absorption spectrum was applied to study the inclusion behavior of PBTCA with HP-β-CD. The results revealed that PBTCA with HP-β-CD can form a 1:1 stoichiometry inclusion complex. The 1:1 inclusion complex synthesized by using lyophilization was further characterized by Fourier transform infrared spectroscopy. Besides, inhibition effect of the inclusion complex on the corrosion inhibition of Q235 carbon steel has been investigated in 0.1 M sulfuric acid (H₂SO₄) solution using potentiodynamic polarization, electrochemical impedance spectroscopy techniques and scanning electron microscopy (SEM). It was found that the presence of the inclusion complex better achieved the anti-corrosion property in aggressive medium than was the case with alone PBTCA and the highest inhibition efficiency of the inclusion complex over 90 % was obtained, which are suggestive of the active effect of the inclusion complex for improving inhibition efficiency of PBTCA. Meanwhile, the results obtained from SEM further showed that the inclusion complex acts as a more efficient corrosion inhibitor for Q235 carbon steel in H₂SO₄ medium.     

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.     

Adsorption and inhibition properties of Tephrosia Purpurea as corrosion inhibitor for mild steel in sulphuric acid solution

Abstract

The present study investigated the adsorption and inhibition behavior of leaf extract of Tephrosia Purpurea (T. purpurea) on mild steel corrosion in 1?N H₂SO₄ solution using electrochemical and surface morphological methods. Techniques adopted for electrochemical studies were Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) technique; and surface morphological studies were carried out using Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The leaf extract of T. purpurea was characterized using UV-Visible spectroscopy (UV-Vis), Fourier-Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance Spectroscopy (NMR) and Gas Chromatography – Mass Spectrometry (GCMS). The results obtained from electrochemical studies exhibited the potential of T. purpurea as good corrosion inhibitor. And, it was found that, the inhibition efficiency (I.E in %) increases with increase in concentration of the inhibitor molecules, the optimum inhibitor concentration observed was 300?ppm and the inhibition efficiency of 93% was observed at this inhibitor concentration. Above 300?ppm, there was not much changes in inhibition efficiency. Polarization studies provided the information that the inhibition is of mixed type and EIS confirmed that the corrosion process is controlled by single charge transfer mechanism. And, it was obtained that, the adsorption of inhibitor molecules obeys Langmuir adsorption isotherm. The inhibition is mainly by the adsorption of inhibitor molecules on the mild steel electrode surface, which was confirmed by FT-IR, SEM and AFM studies. Through all the experimental results, it can be arrived that, the leaf extract of T. purpurea performed as a good corrosion inhibitor for mild steel in 1?N sulfuric acid medium.     

Monte Carlo simulation and electrochemical performance corrosion inhibition whid benzimidazole derivative for XC48 steel in 0.5 M H2SO4 and 1.0 M HCl solutions

The inhibition of 1-(4-methoxybenzyl)-2-(4-methoxyphenyl)-1H-benzimidazole (MMB) on corrosion of XC48 steel in solutions 1.0 M HCl and 0.5 M H₂SO₄ were studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques (EIS). Potentiodynmic polarization curves revealed that MMB acts as a mixed-type inhibitor in both acidic media. The impedance results indicated that the corrosion process occurs under activation control. Furthermore, MMB shows a higher inhibition efficiency in HCl (97%) than in H₂SO₄ (92%) at 10^?4 M MMB. The values of ΔG°_ads, ΔH_a, E_a and ΔS_a in temperature range 293–323 K indicated that MMB strongly retarded the corrosion of XC48 steel in both solutions by a chemisorptions process. The adsorption of Benzimidazole (MMB) on carbon steel surface followed Langmuir adsorption isotherm. Scanning electron microscopy (SEM) analysis confirmed that there is an adsorbed film on the surface of XC48 steel. The results of Monte Carlo simulations studies confirmed the inhibition action of MMB.