Synthesis,Corrosion Inhibition Performance and Biodegradability of Novel Alkyl Hydroxyethyl Imidazoline Salts

New alkyl hydroxyethyl imidazoline salts were synthesized via a high pressure process with imidazoline and dimethyl carbonate, and their chemical structure were confirmed using mass spectral fragmentation and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions (formic acid, acetic acid and lactic acid) were also synthesized by ion exchange reaction of methyl carbonate quaternary ammoniums with the corresponding acids. These new compounds reduced the surface tension of water to a minimum value of approximately 27 mN m^?1 at a concentration of 8.72 × 10^?5 mol L^?1. They also show efficient corrosion inhibition performances and could significantly inhibit the corrosion of mild steel in acid solutions. It was also found that the biological degradation of these imidazoline surfactants was greater than 98 % after 7 days.     

Synthesis,Characterization and Inhibition Performance of Vanillin‐Modified Chitosan Quaternary Ammonium Salts for Q235 Steel Corrosion in HCl Solution

In order to enhance the solubility of chitosan in water and its corrosion inhibition performance on Q235 steel in 1 M HCl solution, N‐vanillyl‐O‐2′‐hydroxypropyltrimethylammonium chloride chitosan (VHTC) was synthesized. The structure of VHTC was characterized by FT‐IR and ¹H‐NMR spectroscopy. The corrosion inhibition performance of VHTC on Q235 steel in 1 M HCl solution was studied by weight loss, polarization, electrochemical impedance spectroscopy (EIS) and stereo microscope analysis. Experimental results indicate that VHTC shows better inhibition efficiency compared to chitosan. When the concentration of VHTC increases to 200 mg L^?1, the inhibition efficiency reaches 90 %, which is almost equal to the conventional corrosion inhibitors (e.g., imidazoline). The polarization study demonstrates that VHTC is a mixed‐type inhibitor caused by a geometrical blanketing effect. The charge transfer resistance is proportional to the inhibitor concentration as revealed by the EIS results, indicating that the protective film on the Q235 steel surface is formed by adsorption of the inhibitor molecules. The inhibition efficiency of VHTC achieves the maximum value within 24 h when the concentration of VHTC is 200 mg L^?1. The morphology observation of the corroded steel surface indicates that the corrosion of Q235 steel in 1 M HCl solution is significantly inhibited after introducing VHTC into the acidic solution.     

Corrosion of tin in aqueous solutions of mono-, Di- and trichloroacetic acids

The corrosion behaviour of tin in stagnant mono-, di- and trichloroacetic acids solutions in the pH range 1–6 and at concentrations 4.0 to 5 × 10^?4 M was investigated. The results indicate behaviour that is generally the same but there is some dependence on the acid concentration and the pH value. In 4.0 to 10^?2 M solutions, the corrosion rate (W) increased with increasing acid concentration and decreasing pH value from 1 to 4 as follows: log W=a+b log C, where b=0.70, 0.42 and 0.35 for tri-, di- and mono-chloroacetic acids respectively. At high concentrations 4.0 to 10^?2 M and in the pH range 1–6, the steady state corrosion potential shifted in the negative direction with increase of acid concentration accompanied by an increase in the corrosion rate, indicating that the corrosion process becomes anodically controlled by the complexing of Sn²⁺ ions with organic acid anions and that the order of aggressiveness is mono-<di-<trichloroacetic acids. In dilute solutions (10^?2 to 5.10^?4 M) in the pH range 1–6 the steady state potential shifted in the noble direction with increase of acid concentration (accompanied by a remarkable decrease in the corrosion rate). Corrosion inhibition in dilute solutions was attributed to film formation on the surface of tin which may result from the hydrolysis of tin species.     

油酸咪唑啉类缓蚀剂对不锈钢的缓蚀性能研究

利用静态失重法、Tafel极化曲线研究了油酸咪唑啉类缓蚀剂在不同酸介质中对不锈钢的缓蚀性能,并尝试了油酸咪唑啉缓蚀剂与KI的复配实验。结果表明,油酸咪唑啉类缓蚀剂在10%盐酸中和10%硫酸中对不锈钢有很好的缓蚀作用。在10%盐酸介质中,只需加入0.3%的油酸咪唑啉缓蚀剂,不锈钢材质的缓蚀率就能达到98%;在10%硫酸介质中,缓蚀率在油酸咪唑啉缓蚀剂添加量为0.5%时最大,达到94%。与KI的复配结果表明,咪唑啉与KI之间有一定的缓蚀协同效应,复合使用可以达到降低成本和保持高缓蚀率的作用。     

Dissolving states of cellulose and chitosan in trifluoroacetic acid

Chemical structures of cellulose and chitosan dissolved in trifluoroacetic acid (TFA) and those of cellulose and chitosan films cast from their TFA solutions were studied by ¹³C-NMR and infrared (IR) spectroscopy. Cellulose is trifluoroacetylated selectively at the C6–hydroxyl groups in the TFA solution, and chitosan is dissolved in TFA by forming amine salts with TFA at the C2–amine groups. IR analyses of cellulose films cast from its TFA–acetic acid solutions showed that partly trifluoroacetylated cellulose in the solution state turns to partly acetylated cellulose in the solid state during evaporation of the solvents in air by the ester interchange. Chitosan films cast from its TFA–acetic acid solutions still have the amine salts with TFA. These acetyl groups in cellulose films and TFA in chitosan films are removable by soaking the films in 1N NaOH at room temperature for 1 day.     

Synthesis,characterization, and in vitro drug‐release properties of 2‐hydroxyethyl methacrylate copolymers

2‐Hydroxyethyl methacrylate was copolymerized with acrylamide, N‐vinyl‐2‐pyrrolidone, and n‐butyl methacrylate by free‐radical solution polymerization with α,α′‐azobisisobutyronitrile as an initiator at 70 ± 1°C. The average molecular weights and molar compositions of the resultant copolymers were determined with gel permeation chromatography and ¹H‐NMR spectroscopy data, respectively. Diclofenac or 2‐[(2,6‐dichlorophenyl)amino]benzene acetic acid, a nonsteroidal anti‐inflammatory drug, was chemically attached to the copolymers by transesterification reaction in the presence of N,N′‐dicyclohexylcarbodiimide to give macromolecular prodrugs. All the synthesized polymers were characterized with Fourier transform infrared, ¹H‐, and ¹³C‐NMR spectroscopy techniques. The polymer–drug conjugates were hydrolyzed in cellophane member dialysis bags containing aqueous buffered solutions (pH 8) at 37°C, and the hydrolysis solutions were detected by UV spectrophotometer at selected intervals. The results showed that the drug could be released by selective hydrolysis of the ester bond from the side chain of the drug moiety. The release profiles of the drug indicated that the hydrolytic behavior of polymeric prodrugs strongly depends on the hydrophilicity of the polymer. The results suggest that the synthesized copolymers could be useful carriers for the release of diclofenac in controlled‐release systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2403–2409, 2007     

Influence of molecular weight of poly(ortho‐ethoxyaniline) on the corrosion inhibition efficiency of mild steel in acidic media

The present work revealed that the chemical polymerization of ortho‐ethoxyaniline yields two types of polymers not only with different spectroscopic properties but also with different molecular weights: (1) a green form, which corresponds to the high molecular weight fraction of the polymer with a molecular weight of 800,000 g mol^?1 based on the polystyrene calibration. It is mainly composed of quinoid and benzoid structures, which is an indication of a half‐oxidized polymer (emeraldine). This form of the polymer is insoluble in water‐miscible solvents like ethanol and methanol and thus cannot be tested in terms of corrosion inhibition efficiency; (2) a red form, which corresponds to the low molecular weight fraction of the polymer with a molecular weight of 44,000 g mol^?1. It is composed mostly of quinoid structures and exhibits an oxidation state similar to that of the completely oxidized polymer (pernigraniline). In our case, the polymer fraction, which is soluble in alcohol, was first tested as a corrosion inhibitor for mild steel in acidic media, not only at conventional molecular weight (44,000 g mol^?1) but also at different molecular weights. These different molecular weights of the polymer were obtained by adding varying amounts of neutral salt to the synthesis environment. Next, the effect of the molecular weight of the red form of the polymer on the corrosion inhibition efficiency of mild steel in hydrochloric acid solutions was investigated. The obtained results showed that the adsorption of the polymer alcoholic form obeys a Temkin adsorption isotherm with no significant change as function of inhibition efficiencies for a series of molecular weights ranging from13,000 to 124,000 g mol^?1. The effect of temperature on the corrosion behavior of mild steel in 1M HCl with addition of 100 ppm of the alcoholic form of poly(ortho‐ethoxyaniline) was studied in the temperature range 25–60°C. The associated activation corrosion energy was determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1275–1284, 2004     

Environmentally safe corrosion inhibition of Mg–Al–Zn alloy in chloride free neutral solutions by amino acids

The corrosion inhibition of Mg–Al–Zn alloy was investigated in stagnant naturally aerated chloride free neutral solutions using amino acids as environmentally safe corrosion inhibitors. The corrosion rate was calculated in the absence and presence of the corrosion inhibitor using the polarization technique and electrochemical impedance spectroscopy. The experimental impedance data were fitted to theoretical data according to a proposed electronic circuit model to explain the behavior of the alloy/electrolyte interface under different conditions. The corrosion inhibition process was found to depend on the adsorption of the amino acid molecules on the metal surface. Phenyl alanine has shown remarkably high corrosion inhibition efficiency up to 93% at a concentration of 2 × 10⁻³ mol dm⁻³. The corrosion inhibition efficiency was found to depend on the concentration of the amino acid and its structure. The mechanism of the corrosion inhibition process was discussed and different adsorption isotherms were investigated. The free energy of the adsorption process was calculated for the adsorption of different amino acids on the Mg–Al–Zn alloy and the obtained values reveal a physical adsorption of the inhibitor molecules on the alloy surface.     

硫脲基松香咪唑啉季铵盐 对A3碳钢的缓蚀性能研究

合成了硫脲基松香咪唑啉季铵盐,对其结构进行了红外和核磁表征。采用失重法、动电位极化曲线、交流阻抗以及接触角测试分析了目标产物在质量分数为15%HCl溶液中对A3碳钢的缓蚀性能。采用AFM以及XPS测试对产物的吸附膜进行了表征。结果表明：目标产物的缓蚀效率随添加质量分数的增加先增大后减小,当目标产物质量分数增加到占盐酸质量的0.4%时,缓蚀效率最高达到90.78%;此物质是一种阴极控制为主的混合型缓蚀剂;AFM以及XPS结果证实目标产物确实可以在碳钢表面形成缓蚀剂吸附膜。     

Polygonatum odaratum extract as an eco-friendly inhibitor for aluminum corrosion in acidic medium

The corrosion of aluminum specimens in Polygonatum odaratum (P. odaratum) extract was studied using weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), and electron dispersive X-ray spectroscopy (EDX) techniques. The inhibition efficiency of the aluminum specimens in the presence of inhibitor from P. odaratum plant extract at 303–333 ± 1 K was evaluated with the weight loss technique. The results indicate the inhibition efficiency of P. odaratum plant extract increased with increased concentration of the inhibitor and decreased temperature in an acidic medium. The corrosion inhibition properties of the P. odaratum plant extract for aluminum specimen corrosion in 1 M HCl were analyzed using polarization studies and electrochemical impedance studies, which clearly showed a mixed-type inhibitor. UV-visible spectroscopy, Fourier transform infrared (FT-IR), SEM, and EDX revealed the surface morphology in the presence and absence of inhibitor on the metal surface. The results indicated the feasibility of using the P. odaratum plant extract as a corrosion inhibitor in acid environments.     

一种抗CO2腐蚀缓蚀剂的制备及缓蚀性能研究

以油酸、二乙烯三胺、硫脲和氯化苄等为原料,合成出一种抗CO2腐蚀的咪唑啉季铵盐缓蚀剂,通过红外光谱法对其结构进行了表征,并利用静态失重法在模拟地层水的环境下对其缓蚀性能进行了研究。结果表明:红外谱图证明该实验成功地合成了咪唑啉季铵盐缓蚀剂;在高含CO2(PCO2=4.64MPa)的腐蚀介质中,当温度为90℃,缓蚀剂的用量为0.025%时,其缓蚀率可达88%以上;当温度的升高、腐蚀时间延长和矿化度增加时,缓蚀率均呈下降趋势。     

Alternating,all-trans polyenynes: Model compounds for poly(diacetylene)s with defined conjugation length

The syntheses of polyenynes as model compounds for poly(diacetylene)s (PDAs) are described. Variation of properties (UV–VIS, Raman, NMR and bond geometries) as a function of the chain length was investigated. After extrapolation to infinite chain length these data were compared to those for PDAs. From UV–VIS spectra a value of λ = 551 nm (2.25 eV) was calculated corresponding to the electronic transition of a single polyenyne chain. This energy is located at the low energy end of a yellow PDA solution spectrum. From Raman scattering v_(C?C) = 2108–2128 cm^?1 and v_(C?C) = 1505–1532 cm^?1 were calculated after extrapolation. Similarly sp-C¹³C NMR data yielded a shift of δ = 100 ppm. These data are almost identical to data known for yellow PDA solutions. Bond geometries are almost identical to those of poly(diacetylene)s and theoretical data.     

盐类浓度对油酸咪唑啉季铵盐缓蚀率的影响

针对油田污水富含钙、镁、钠等盐类的现状,合成了油酸咪唑啉季铵盐,采用电化学极化法和静态失重法测试了其缓蚀性能,并采用电化学极化法考察了强酸腐蚀介质中氯化钙、氯化镁及氯化钠3种盐的浓度对该缓蚀剂缓蚀率的影响。结果表明:该缓蚀剂是一种以阳极抑制为主的混合型缓蚀剂;在1mol·L-1 HCl溶液中,当缓蚀剂浓度为5mg·L-1时,N80钢片的腐蚀速率和缓蚀剂的缓蚀率趋于稳定;随着介质中盐类浓度的增大,缓蚀剂的缓蚀率逐渐减小。分析认为,缓蚀率减小的原因可能是由于介质的电导率增大,导致腐蚀速率加快。     

新型离子液体的合成及其阳离子基团缓蚀性能

以高纯环烷酸为原料,合成了一系列含咪唑啉环的新型离子液体Ⅰ～Ⅴ,探讨了阳离子咪唑啉基团中N_（3）原子上取代基与缓蚀性能的关系.采用碳钢挂片失重法和电化学测试法,评价了它们在酸性溶液中的缓蚀性能;采用量子化学法和极化效应指数法,分别计算了离子液体Ⅰ～Ⅴ阳离子咪唑啉基团的前线轨道能量及其相应的PEI等参数.实验结果和理论分析表明：离子液体Ⅰ～Ⅴ阳离子咪唑啉基团的缓蚀效率呈现如下关系,Ⅴ＞Ⅳ＞Ⅲ＞Ⅱ＞Ⅰ;其缓蚀效率与E_HOMO、ΔE_L-H和PEI等参数间均具有良好的线性关系.     

两种高效低成本咪唑啉类缓蚀剂的研制

为了缓解油田设备因腐蚀引起的问题,实验通过有机合成方法,用苯甲酸(油酸)和三乙烯四胺及氯化苄合成得到咪唑啉季铵盐缓蚀剂,经过油酸咪唑啉季铵盐缓蚀剂与苯甲酸咪唑啉季铵盐缓蚀剂的复配后,通过静态失重法进行评价。结果表明这类缓蚀剂的最佳加药浓度为30 mg·L-1,此时两种酸类咪唑啉季铵盐含量比为2∶3时的缓蚀效率可以达到97.4%;主剂(苯甲酸∶油酸=2∶3)与硫脲、乌洛托品、乙酰苯胺按比例10∶5∶2∶1复配缓蚀效率可以达到98.4%,符合油田生产需求。     

Corrosion inhibition of mild steel in 1 M HCl using Tamarindus indica extract: electrochemical,surface and spectroscopic studies

Abstract

We report, here, the corrosion inhibition of mild steel specimen in 1?M HCl by tamarind fruit pulp aqueous (TFPA) extract. The inhibition property in the presence of TFPA extract is studied using weight loss, polarization measurement and electrochemical impedance spectroscopy (EIS). The inhibitor efficiency is found to vary from 74% to 88% (weight loss method) with TFPA concentration of 100–600?ppm. The reduction in Tafel slopes shows that TFPA acts as a mixed-type inhibitor. The adsorption of the inhibitor on the metal surface follows Langmuir isotherm. The standard Gibbs free energy of adsorption value of –40?kJ/mol suggests the chemisorption of inhibitor molecules via coordinate bond. AFM results exhibit a decrease in the surface roughness of mild steel, exposed to 1?M HCl from 299?±?12 to 154?±?6.6?nm, with increasing concentration of inhibitor from 0 to 600?ppm due to the uniform coverage of inhibitor molecules on the metal surface. X-ray photoelectron spectroscopy de-convoluted high resolution profiles of C 1?s (carbon) for mild steel exposed to 1?M HCl with 600?ppm inhibitor show major peaks corresponding to sp³ C–C/C–H (284.9?eV) and oxygen bondings in C–OH, C=O, COOH with a binding energy of 285.9, 286.9, 288.5?eV, respectively, thereby confirming the adsorption of organic moieties on mild steel surface. Fourier transform infrared spectroscopy further confirms the adsorption of inhibitor molecules on the metal surface. Therefore, tamarind fruit pulp extract is a potential corrosion inhibitor for mild steel, which is cost-effective, green and non-toxic.     

一种新型固体缓蚀剂的合成及性能

以二聚油酸和二乙烯三胺为原料,氯乙酸为反应介质,经酰胺化、环化和季铵化反应合成了新型咪唑啉。通过正交实验研究,确定最优合成条件为:n(二乙烯三胺)∶n(二聚油酸)=1∶2.1;酰胺化时间3.5 h,季铵化时间3 h。通过红外光谱分析表明,产物为咪唑啉季铵盐,经测定其季铵盐质量分数为理论值的80%左右;通过ρ(C l-)=157 305 mg/L、CO2分压为3.5 MPa、在120℃和20 MPa条件下的油田模拟工况实验,证明该咪唑啉季铵盐对N80套管钢缓蚀率在85%以上,符合西部油田苛刻的腐蚀环境要求。     

Double-Tailed Single-Head Amino Acid-Based Chiral Cationic Amphiphilic Molecules: Synthesis,Characterization, and Physicochemical Properties

Two double-tailed single-head amino acid-based chiral cationic amphiphilic molecules, l -aspartic acid hydrochloride dihexylester (L-ADHE, C₆–C₆) and l -aspartic acid hydrochloride dioctylester (L-ADOE, C₈–C₈), were synthesized. ¹H NMR, ¹³C NMR, and Fourier transform infrared (FT-IR) were used to characterize the structures of the esters. Micellization, surface, and structural properties of L-ADHE and L-ADOE in aqueous solution were studied by means of a number of techniques including conductivity, pH, surface tension, density, zeta potential, and dynamic light scattering (DLS). The critical micelle concentration (CMC) of L-ADHE and L-ADOE were found to be very low compared with those of corresponding single-tailed amino acid-based amphiphilic molecules. The pK_a values of L-ADHE and L-ADOE in aqueous solutions were determined via pH measurements, and it was observed that they had acidic properties giving low pK_a values. The excellent adsorption behaviors at the air/water interface of L-ADHE and L-ADOE in aqueous medium were obtained, i.e. they efficiently lowered the surface tension of water at CMC down approximately to 24.3 and 23.4 mN m⁻¹, respectively. From the density measurements, the volume change due to the micellization process for L-ADOE was found to be quite high compared to L-ADHE, i.e. about three times more. This result and the data obtained from the DLS revealed that the increase in aggregated structures of L-ADOE may be due to vesicle formation. The dye solubilization study was performed by UV–vis absorption spectroscopy for L-ADHE. Besides, the CMC value of L-ADHE was also successfully determined without using any dye through UV–vis spectroscopy.     

Comparative study of corrosion inhibition by three anionic surfactants in an acidic environment

Corrosion in carbon steel units of chemical, petrochemical and oil and gas plants poses safety and economic concerns. The goal of our study is to investigate the corrosion inhibition effectiveness of an environmentally benign surfactant, namely sodium lauroyl lactylate (SLL), in comparison to sodium cocoyl glutamate (SCG) and sodium dodecyl sulfate (SDS). The corrosion of carbon steel in 1 M HCl was markedly inhibited by 0.05 and 0.1 M of the anionic surfactant SLL, as determined from weight loss over 96 h, at ambient conditions. X-ray photoelectron spectroscopy (XPS) showed that SLL adsorbed at the carbon steel surface, forming a protective film that decreased corrosion. Scanning electron microscopy (SEM) showed that carbon steel surfaces immersed in 1 M HCl for 96 h had an etched appearance without SLL, whereas they retained their smoothness with 0.1 M SLL. Electrochemical impedance spectroscopy (EIS) measurements confirmed that SLL passivated carbon steel surfaces, markedly increasing the polarization resistance R_p from ≈95 to ≈20,694 Ω cm² over a 12 h period. In contrast, without SLL, R_p decreased from ≈92 to ≈12 Ω cm². These results demonstrate for the first time that the environmentally friendly surfactant SLL is an efficient corrosion inhibitor in extreme environments such as 1 M HCl solutions. Dissimilar to SLL, SCG and SDS were not effective in inhibiting corrosion.     

SYNTHESIS,CHARACTERIZATION, AND COMPARATIVE STUDY OF PYRIDINE DERIVATIVES AS CORROSION INHIBITORS OF MILD STEEL IN HCl MEDIUM

Radical catalysis has been used to achieve addition of dodecanethiol and mercaptoacetic acid to 4-vinylpyridine (4VP), giving 4-(dodecylthiaethyl)pyridine (DTEP) and 4-pyridylethylthia-acetic acid (PETAA). The purified monoadducts have been characterized using ¹H NMR and ¹³C NMR spectroscopy. Inhibition of the corrosion of mild steel in 1 M HCl by 4VP, DTEP, and PETAA has been investigated at 308 K using weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. The results obtained show that PETAA is the best inhibitor and its inhibition efficiency (E %) increases with the inhibitor concentration, reaching up to 93% for DTEP at 10^?3 M. Potentiodynamic polarization studies clearly revealed that the inhibitors changed the mechanism of hydrogen evolution and that they acted as mixed inhibitors but most effectively in the cathodic range.