Inhibition of cold rolled steel corrosion in sulphuric acid solution by 2-mercapto-1-methylimidazole: Time and temperature effects treatments

2-Mercapto-1-methylimidazole (MMI) has been evaluated as a corrosion inhibitor for cold rolled steel in aerated 2 M H₂SO₄ by gravimetric method. The effect of MMI on the corrosion rate was determined at various immersions time and concentrations. The effect of the temperature on the corrosion behaviour with addition of different concentrations of MMI was studied in the temperature range 30–60 °C. The MMI acts as an effective corrosion inhibitor for cold rolled in sulphuric acid medium. The inhibition process is attributed to the formation of an adsorbed film of MMI on the metal surface which protects the metal against corrosion. The protection efficiency increased with increase in inhibitor concentration at various immersions time and decreased with increase in temperature. Adsorption of MMI on the cold rolled steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined.     

Rosmarinus officinalis extract as eco-friendly corrosion inhibitor for copper in 1 M nitric acid solution: Experimental and theoretical studies

Rosmarinus officinalis extract (ROE) was studied chemically (mass loss, ML), electrochemically impedance spectrometry (EIS), and potentiodynamic polarization (PDP) as a corrosion inhibitor in 1 M nitric acid. According to ML, ROE is effective like a copper preservative in 1 M HNO₃ acid solution at R.T by improving inhibitor concentration up to 77 % at 300 ppm and 25 °C. A study was conducted regarding the effect of temperature on copper adsorption, as well as the calculation of adsorption coefficients. Results indicated that physisorption increases with temperature, indicating a decrease in inhibition efficiency (%IE). Langmuir's adsorption model was consistent with the adsorption mechanism. Using the PDP method, the inhibitor accumulated on the copper surface in mixed forms. Moreover, EIS revealed that the value of double-layer capacitance dropped with an increased dose of ROE, while the charge transfer resistance improved. A different approach was taken to the examination of surfaces. Both theoretical studies and practical results were calculated and compared to demonstrate that the results were valid.     

Surface interaction and corrosion inhibition of carbon steel in sulfuric acid using Petroselinum crispum extract

With the aid of the mass loss (ML) method, and a few electrochemical techniques [potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)], the inhibitory impact of Petroselinum crispum (PC) extract on C-steel corrosion in solutions of 1 M sulfuric acid was assessed. By employing Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques, the C-steel surface morphology was investigated. The data showed that the solution of plant extract can be effectively utilized to inhibit C-steel corrosion in solutions of 1 M sulfuric acid. The effectiveness of the extract was enhanced by the higher extract dose and rising temperature. The apparent activation energy and the enthalpy of the dissolution process were determined and discussed. The presence of PC decreases the double-layer capacity from 493.1 to 107.3 μF cm⁻² and raises the charge transfer resistance in a solution of 1 M sulfuric acid from 43.39 to 287.7 Ω cm². PC is a mixed-type inhibitor, as demonstrated by PDP tests. The PC extract demonstrated the highest productivity for the C-steel protection up to 90.2% at 300 ppm from the extract, according with the PDP technique. The attained data indicated that PC extract was adsorbed chemically (ΔG^o_ads > 40 kJ mol⁻¹) onto the surface of the C-steel following the Temkin isotherm. The results of numerous tests appear to agree.     

Role of dissolved oxygen reduction in improvement inhibition performance of ascorbic acid during copper corrosion in 0.50 mol/L sulphuric acid

<正>The kinetics of dissolved O_2 reduction and hydrogen evolution reactions on copper surface was studied in naturally aerated and air and O_2-saturated 0.50 mol/L H_2SO_4 solutions using polarization measurements combined with the rotating disc electrode (RDE).The Koutecky-Levich plot indicated that the dissolved O_2 reduction at the copper electrode was an apparent four-electron process.A correlation between the presence of dissolved O_2 and the formation of Cu_2O,confirmed from XRD,was discussed. Ascorbic acid(AA) was tested as a safe inhibitor for copper corrosion in H_2SO_4 solutions at 25℃.Measurements were carried out as a function of dissolved oxygen concentration using Tafel polarization measurements.The addition of AA slowed down the reduction reaction of dissolved O_2 more effectively than the anodic reaction.Dissolved O_2 was found to enhance the inhibition performance of AA.Adsorption via hydrogen bonding was considered.     

Thermal and structural properties of coordination compounds of 2-mercapto-1-methylimidazole with palladium(II) and platinum(II)

Complexes of 2-mercapto-1-methylimidazole (TMZ) with Pd^II and Pt^II of the general formula M(TMZ)_nX₂ (whereM=Pd, Pt andX=Cl, Br, I or SO₄ andn=2 or 4) were obtained. The thermal stabilities of the compounds were estimated by derivatographic measurements and lattice constants were estimated from their X-ray powder diffraction patterns.     

Corrosion inhibition of carbon steel in hydrochloric acid 0.5 M by hexa methylene diamine tetramethyl-phosphonic acid

The efficiency of hexa methylene diamine tetra methyl-phosphonic acid (HMDTMP), as corrosion inhibitor for carbon steel in 0.5 M HCl, has been determined by gravimetric and electrochemical measurements. Polarization curves indicate that the compound is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. Adsorption of HMDTMP derivatives on the carbon steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy value confirms the chemical nature of the adsorption. EIS results show that the charge in the impedance parameters (R_t and C_dl) with concentrations of HMDTMP is indicative. The adsorption of this molecule leads to the formation of a protective layer on carbon steel surface. The electrochemical results have also been supplemented by surface morphological studies.     

Electrochemical quartz crystal microbalance study of copper ad-atoms on gold and platinum electrodes Part I. Adsorption of anions in sulfuric acid

The deposition and dissolution processes of copper ad-atoms on a gold or a platinum electrode in sulfuric acid electrolyte solution were investigated by using the electrochemical quartz crystal microbalance. It was found that the weight loss in the removal of the Cu-adlayer from the Au substrate was considerably larger than that expected from Faraday's law whereas the deviation for the Pt substrate was very small. The adsorption of bisulfate or sulfate anions both on Cu ad-atoms and on the electrode substrates was discussed quantitatively. It was demonstrated that higher coverage with Cu ad-atoms and lower adsorbability with bisulfate or sulfate anions were obtained on the Pt electrode than on the Au, and these effects could be ascribed to the difference in electronegativity between Pt and Au substrates.     

Fluconazole as an inhibitor for aluminium corrosion in 0.1 M HCl

The interfacial behavior of fluconazole (FLC) between aluminium and hydrochloric acid has been investigated by using weight loss technique at 30–50 °C. The results showed that fluconazole is an excellent corrosion inhibitor for aluminium in acidic medium. Inhibition efficiency increased with increase in the concentrations of fluconazole but decreased with rise in temperature. The adsorption of the inhibitor on the aluminium surface is found to accord with Temkin adsorption isotherm. Some thermodynamic and activation parameters have been calculated and analysed. The mechanism of physical adsorption is proposed from the values of E_a and obtained. The correlation of inhibition effect and molecular structure of fluconazole was then discussed by quantum chemistry study to further provide insight into the mechanism of the inhibitory action.     

Synergistic inhibition effects between leaves and stem extracts of Sida acuta and iodide ion for mild steel corrosion in 1 M H2SO4 solutions

The synergistic action caused by iodide ions on the corrosion inhibition of mild steel in 1 M H₂SO₄ by leaves and stem extracts of Sida acuta was studied using weight loss and hydrogen evolution methods at 30–60 °C. It was found that the leaves and stem extracts of S. acuta inhibited the acid induced corrosion of mild steel. Addition of iodide ions enhances the inhibition efficiency to a considerable extent. The inhibition efficiency increases with increase in the iodide ion concentration but decreases with rise in temperature. Adsorption of the extracts alone and in combination of iodide ion was found to obey Freundlich adsorption isotherm at all temperatures studied. Inhibition mechanism is deduced from the temperature dependence of the inhibition efficiency as well as from assessment of kinetic and activation parameters that govern the processes. The synergism parameter (S₁) is defined and evaluated from the inhibition efficiency values. This parameter for the different concentrations of iodide ions from the two techniques employed is found to be greater than unity indicating that the enhanced inhibition efficiency of the extracts caused by the addition of iodide ions is due to synergism.     

Some natural aqueous extracts of plants as green inhibitor for carbon steel corrosion in 0.5 M sulfuric acid

The inhibiting impact of natural aqueous extracts of some plants such as curcumin, parsley and cassia bark extracts for the corrosion of carbon steel (C-steel) in 0.5 M H₂SO₄ solution was inspected utilizing some techniques such as galvanostatic and potentiodynamic anodic polarization and weight loss measurements. Outcomes indicated that the percentage inhibition efficiency increases with increasing the concentration of the extract due to its horizontal adsorption on the C-steel surface. The process of adsorption is followed by the Temkin isotherm. These natural extracts acted as pitting corrosion inhibitors by shifting the pitting potential to more noble values. The sequence of inhibition efficiency of the natural extracts decreases in the following order: cassia bark extract > parsley extract > curcumin extract. This arrangement is related to the molecular size of the major components of the three natural extracts used.     

The influence of aniline and its derivatives on the corrosion behaviour of copper in acid solution

The inhibiting action of aniline and its derivatives on the corrosion of copper in hydrochloric acid has been investigated, with emphasis on the role of substituents. With this purpose five different anilines were selected: aniline, p-chloro aniline, p-nitro aniline, p-methoxy and p-methyl aniline. The electrochemical and gravimetric results, obtained in the absence and presence of different concentrations of inhibitors, revealed that aniline reduces the corrosion of copper, with a critical concentration of 10^–2 M. Furthermore, the interaction energy calculated as G_ads gave a value of 4.2 kcal mol^–1 indicating physisorption of the organic compound at the copper surface. The results have also shown that substituents, either electron donors (–CH₃, –OCH₃) or, electron acceptors (–NO₂, –Cl) in para position, decrease the inhibition action of aniline. A theoretical study using molecular mechanic and ab initio Hartree Fock methods, to model the adsorption of aniline on copper (100) showed results in good agreement with the experimental data. Aniline adsorbs parallel to the copper surface, showing no preference for a specific adsorption site. On the other hand, from ab initio Hartree Fock calculations, an adsorption energy between 2 kcal/mol and 5 kcal/mol is obtained, which is close to the experimental value, confirming that the adsorption of aniline on the metal substrate is rather weak. In view of these results, the orientation of the aniline molecule with respect to the copper surface is considered to be the dominant effect.     

Inhibitory action of aqueous Ruellia Tuberosa L leaves extract on the corrosion of copper in HCl solution

The inhibitive action of the aqueous extract of Ruellia tuberosa L (ART) on the corrosion of copper in 0.5 ​M HCl was investigated. The inhibition efficiency increased with the extract concentration, acid concentration, as well as increasing the temperature. The Polarization studies revealed that the ART act as a mixed-type inhibitor. Based on the analysis of electrochemical impedance spectroscopy, an equivalent circuit is suggested. The adsorption of the inhibitor ART on the copper surface obeyed the Langmuir adsorption isotherm. From the results of scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy the adsorption of ART on the copper surface is confirmed.     

Effect of three 2-allyl-p-mentha-6,8-dien-2-ols on inhibition of mild steel corrosion in 1 M HCl

2-Allyl-p-mentha-6,8-dien-2-ols P1−P3 synthesized from carvone P are tested as corrosion inhibitors of steel in 1 M HCl using weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods. The addition of 2-allyl-p-mentha-6,8-dien-2-ols reduced the corrosion rate. Potentiodynamic polarisation studies clearly reveal that the presence of inhibitors does not change the mechanism of hydrogen evolution and that they act essentially as cathodic inhibitors. 2-Allyl-p-mentha-6,8-dien-2-ols tested adsorb on the steel surface according to Langmuir isotherm. From the adsorption isotherm some thermodynamic data for the adsorption process are calculated and discussed. EIS measurements show the increase of the charge-transfer resistance with the inhibitor concentration. The highest inhibition efficiency (92%) is obtained for P1 at 3 g/L. The corrosion rate decreases with the rise of temperature. The corresponding activation energies are determined.     

Adsorption and inhibitive properties of aminobiphenyl and its Schiff base on mild steel corrosion in 0.5 M HCl medium

Electrochemical measurements were performed to investigate the effectiveness and adsorption behaviour of aminobiphenyl (Aph) and 2-(3-hydroxybenzylideneamino)biphenyl (Aph-S), as corrosion inhibitors for mild steel (MS) in 0.5 M HCl solution. Potentiodynamic polarization, linear polarization resistance (LP) and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behaviour in the absence and presence of different concentrations of Aph and Aph-S. In order to gain more information about adsorption mechanism the AC impedance technique was used to evaluate the potential of zero charge (PZC) from polarization resistance (R_p) versus voltage (E) plot. Potentiodynamic polarization measurements showed that Aph act as cathodic type inhibitor where as Aph-S act mixed type. The inhibition efficiency (IE%) increases with increasing concentration of compounds and reached 92.6% for Aph and 97.2% for Aph-S at 5 × 10⁻³ M. Double layer capacitance (C_dl) and polarization resistance (R_p) values are derived from Nyquist plots obtained from AC impedance studies. The experimental data fit Langmuir isotherm for both Aph and Aph-S, and from the adsorption isotherm some thermodynamic data for the adsorption processes are calculated and discussed. The effect of exposure time on the corrosion behaviour of mild steel in the absence and presence of inhibitor over 168 h was also studied.     

The staged synthesis of 2-methylimidazole from ethylenediamine and acetic acid in the presence of a bifunctional aluminoplatinum catalyst

An investigation has been conducted into the staged synthesis of 2-methylimidazole from ethylenediamine and acetic acid in the presence of a bifunctional aluminoplatinum catalyst. It has been shown that the formation stage of 2-methylimidazoline occurs more quickly on -Al₂O₃ than its dehydrogenation on the Pt centers. From a comparison of the processes of dehydrogenation of 2-methylimidazoline in the molten phase and in aqueous solution it follows that the water eliminated in the imidazoline formation stage could cause the decrease in activity during the dehydrogenation on the Pt centers. The structures of the secondary and intermediate products have been established for each stage of the process and their formation routes are discussed.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 1997–2002, September, 1992.     

电感耦合等离子体-发射光谱分析中硫酸基体效应及抑制

研究了电感耦合等离子体-发射光谱分析中的硫酸基体效应及克服干扰的有效方法。对2%~20%范围内4种不同体积分数H2SO4溶液中30种元素的基体效应进行了观察,发现H2SO4对各元素的谱线发射强度均存在明显的抑制作用。实验证实体积分数5%乙酸可有效抑制H2SO4的基体效应,并建立了H2SO4溶液中痕量元素的电感耦合等离子体-发射光谱分析法。     

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。     

Electrochemical investigation of corrosion and corrosion inhibition of iron in hydrochloric acid solutions

The inhibition effect of 1-methyl pyrazole (MPA) on the acidic corrosion of iron in 1.0 M HCl was studied at different concentrations (10^?3–10^?2 M) by potentiodynamic polarization and electrochemical impedance spectroscopy, and EIS measurements. It is found from the polarization studies that methyl pyrazole (MPA) behaves mainly as anodic inhibitor in HCl. Values of polarization resistance (R_p) and double layer capacitance (C_dl) in the absence and presence of MPA in 1.0 M HCl are determined. The adsorption of MPA on iron surface from HCl is found to obey Temkin adsorption isotherm.     

Valorization of Zea mays hairs waste extracts for antioxidant and anticorrosive activity of mild steel in 1 M HCl environment

The extraction of Zea mays hairs (Z. mays) was carried out by soxhlet and ultrasound techniques and through three solvents. Phytochemical tests and quantitative analysis of total phenols content (TPC) and flavonoids content (FC) for all extracts were also determined. The antioxidant activity, for different fractions, was determined by using three methods; DPPH, FRAP and TAC. All extracts were rich in polyphenols and the analysis of TPC and FC showed that the hydro-ethanolic extract obtained by ultrasound was characterized by a significant amount of TPC and FC. The n-butanolic fraction was rich in FC and also had a very high antioxidant capacity. On the other hand, the inhibiting effect of hydro-ethanolic extract, n-butanolic fraction and standard (flavone) on mild steel corrosion in 1 M HCl solution was investigated by electrochemical measurements. The polarization curves along with EIS diagrams indicated that flavone was the major molecule responsible for inhibition and acted as mixed-type inhibitor with predominant control of cathodic reaction. The antioxidant activity of BF was well correlated to corrosion inhibition efficiency.     

Three copper(II) complexes of thiophene-2,5-dicarboxylic acid with dissimilar ligands: Synthesis, IR and UV–Vis spectra, thermal properties and structural characterizations

Three thiophene-2,5-dicarboxylic acid (H₂tdc) complexes of copper(II) with 2-aminomethylpyridine (ampy), {[Cu₂(μ-tdc)₂(ampy)₂]·2DMF}_n (1), ethylenediamine (en), trans-[Cu(H₂O)₂(en)₂](tdc) (2) and 4-methylimidazole (4-meim), trans-[Cu(H₂O)₂(4-meim)₄](tdc)·4H₂O (3) have been synthesized and characterized by spectral (IR, UV–Vis), thermal analyses and X-ray diffraction techniques. In 1, thiophene-2,5-dicarboxylate acts as a bridging bis(bidentate) ligand through four carboxylate oxygen atoms forming a 1-D zigzag polymeric chain, whereas in 2 and 3 the tdc dianion behaves as a counter ion. In all cases, the Cu(II) centers have an octahedral coordination geometry. Three-dimensional frameworks are constructed though hydrogen bonding and/or C–H···π interactions in the three complexes.