CO_2体系中咪唑啉季铵盐与十二烷基磺酸钠之间的缓蚀协同效应

采用失重法、电化学阻抗谱(EIS)、极化曲线、X射线光电子能谱仪(XPS)及扫描电子显微镜(SEM)研究了CO2饱和的3.5%NaCl腐蚀介质中,咪唑啉季铵盐(IAS)与十二烷基磺酸钠(SDSH)对Q235钢的缓蚀协同效应.结果表明,IAS与低浓度SDSH在腐蚀介质中具有较好的缓蚀协同效应,且当二者以1:1(50 mg·L-1:50 mg·L-1)的浓度比例复配时,协同效应最明显,缓蚀率为88.5%;而IAS与高浓度SDSH间会产生拮抗效应.本文通过建立合理的吸附模型,阐述了协同效应及拮抗效应的机理.SDSH与IAS在Q235钢表面的吸附过程均为放热的自发过程,前者符合Frumkin吸附模型,后者符合Temkin吸附模型.单独使用较高浓度的SDSH对Q235钢也有较好的缓蚀作用,缓蚀率接近90%.     

离子液体[Bmim]Cl在H_2SO_4中对Q235钢的缓蚀实验和理论分析

探究1-丁基-3-甲基-咪唑氯盐([Bmim]Cl)在H_2SO_4介质中对Q235钢的缓蚀性能,解决酸性环境在金属表面造成的腐蚀危害。采用静态缓蚀失重法、电化学法分析了不同浓度[Bmim]Cl对Q235钢的缓蚀性能。Q235钢表面形貌特征以及吸附行为分别采用了扫描电子显微镜(SEM)及吸附等温模型进行了分析。采用理论模拟计算分析了缓蚀剂分子在碳钢表面的缓蚀机理。结果表明,[Bmim]Cl为阴极主导的混合型缓蚀剂,随[Bmim]Cl浓度的增加,缓蚀效果越好,当[Bmim]Cl浓度为0.6 mol·L~(-1)时,缓蚀效率可达91%以上,等温吸附模型证明缓蚀剂分子可自发吸附在金属表面,符合Langmuir等温线。[Bmim]Cl通过化学键与Q235钢表面结合形成了以咪唑杂环为吸附中心、稳定化学吸附的单分子吸附层,且[Bmim]~+平行吸附于表面达到防腐蚀效果。[Bmim]Cl是一种性能优异的防腐蚀剂,能有效预防Q235钢在H_2SO_4介质中的腐蚀。     

新型不对称双季铵盐缓蚀剂在HCl中对Q235钢的缓蚀行为

采用静态失重法、极化曲线法和交流阻抗法研究了自制的含咪唑啉环不对称双季铵盐缓蚀剂(DBA)在1 mol•L^－1 HCl介质中对Q235钢的缓蚀性能, 并探讨了其在Q235钢表面的吸附行为. 结果表明, 缓蚀效率随DBA浓度增加而增大, 在25～55 ℃的实验温度范围内, 浓度为2.89×10^－4 mol•L^－1时, 缓蚀效率均在90%以上, 且缓蚀效率随温度升高而增大. 极化曲线测试显示DBA是一种阴极抑制为主的混合型缓蚀剂. 缓蚀剂在Q235钢表面的吸附过程为吸热过程, 其在Q235钢表面的吸附遵循Langmuir等温式, 属于化学吸附. 最后采用量子化学方法对DBA的缓蚀机理做了进一步分析.     

2种癸二酸咪唑啉季铵盐的合成及缓蚀性能评价

合成了2种癸二酸咪唑啉季铵盐癸二酸-水杨酸咪唑啉季铵盐(SSAI)和癸二酸咪唑啉季铵盐(SAI),并采用失重法和电化学方法研究了这2种咪唑啉季铵盐对N80钢在1 mol/L HCl溶液中的缓蚀性能和吸附行为。 结果表明,在1 mol/L HCl溶液中这2种化合物对N80钢均有较好的缓蚀作用,缓蚀效率大小顺序为SSAI＞SAI。 SSAI和SAI均为混合偏阳极型缓蚀剂。 2种化合物在N80钢表面的吸附服从Langmuir吸附等温式,属于化学吸附。     

新型咪唑啉缓蚀剂缓蚀性能的理论与实验研究

采用量子化学计算与分子动力学模拟相结合的方法, 对1-(2-氨基-硫脲乙基)-2-十五烷基咪唑啉(A)、1-(2-甲基-硫脲乙基)-2-十五烷基咪唑啉(B)、1-(2-苯基-硫脲乙基)-2-十五烷基咪唑啉(C)三种新设计的咪唑啉类缓蚀剂抑制H₂S, CO₂腐蚀的缓蚀性能进行了理论研究, 并通过失重法和电化学极化曲线法进行了实验验证. 理论计算结果表明, 三种分子都具有较强的反应活性, 反应活性区域集中在咪唑环和亲水支链上, 其中C分子的反应活性最强|与金属表面发生吸附时, 分子上的咪唑环和亲水支链上的极性官能团优先吸附, 分子在Fe表面的吸附稳定性按C, A, B的顺序逐渐减弱. 失重法和电化学极化曲线法实验结果显示, 三种缓蚀剂在H₂S, CO₂共存的腐蚀介质中对Q235钢均具有良好的缓蚀作用, 最高缓蚀效率都在87%以上. 三种新型缓蚀剂的缓蚀效率大小顺序为: C＞A＞B, 理论分析与实验结果相吻合.     

分子结构对咪唑啉缓蚀剂膜在Q235钢表面生长和衰减规律的影响

采用弱极化法、电化学阻抗谱等手段研究了烷基咪唑啉和硫脲基烷基咪唑啉缓蚀剂对Q235钢在饱和CO2盐溶液中的缓蚀行为变化, 探讨了吸附膜的形成与衰减规律. 结果表明, 烷基咪唑啉和硫脲基烷基咪唑啉缓蚀剂都是以控制阳极过程为主的混合界面型缓蚀剂. 在85 ℃下, 烷基咪唑啉成膜相对较慢, 吸附能力较弱, 容易发生脱附; 而硫脲基的引入, 使得硫脲基烷基咪唑啉缓蚀剂溶液存在自动修复能力, 增强了咪唑啉环的吸附性能, 提高了缓蚀剂的缓蚀性能; 硫脲基烷基咪唑啉水解开环后, 成膜性能下降, 膜寿命和缓蚀效率也大大降低. 最后采用量子化学计算对上述结论进行了验证和解释.     

抑制Q235钢CO2腐蚀的气液双相咪唑啉衍生物缓蚀剂的缓蚀行为

采用失重法、交流阻抗(EIS)及傅里叶变换红外光谱(FT-IR)、原子力显微镜(AFM)、X射线光电子能谱(XPS)等表面分析测试方法首次研究了硫脲基咪唑啉衍生物(TAI)作为抑制CO₂腐蚀的气液双相缓蚀剂的缓蚀行为. 结果表明, 该硫脲基咪唑啉缓蚀剂能有效地抑制Q235 钢在气液双相中的CO₂腐蚀. AFM测试结果表明该缓蚀剂能显著地降低碳钢表面的腐蚀破坏, 并且由于碳钢表面形成的缓蚀剂吸附膜的疏水作用,可在AFM探头和碳钢表面之间检测到更大的粘附力, 而探针与试样表面之间的长程静电斥力在气相中增加,在液相中由于表面电荷的屏蔽效应而减小. XPS和FT-IR 光谱测试表明液相中和气相中在碳钢表面形成吸附膜的缓蚀剂成分分别是硫脲基咪唑啉衍生物和其酸水解产物——酰胺. 以上结果也进一步证实了咪唑啉衍生物在酸性溶液中的水解机理.     

O,O'-二(苯基)二硫代磷酸-N,N-二乙铵对Q235钢在硫酸溶液中的缓蚀性能研究

合成了O,O'-二(苯基)二硫代磷酸-N,N-二乙铵(DEDDP),采用失重,电化学和SEM技术共同研究了DEDDP在H2SO4溶液中对Q235钢的缓蚀性能。失重法研究表明:DEDDP在H2SO4溶液中能有效地抑制Q235钢腐蚀,25℃的5%H2SO4溶液中,DEDDP浓度为160 mg.L-1时,其缓蚀率为94.67%;电化学研究结果表明:DEDDP在5%H2SO4溶液中属混合型缓蚀剂。同时,研究了温度,H2SO4浓度和浸泡时间对缓蚀率的影响。吸附规律研究表明:DEDDP在Q235钢表面的吸附符合Langmuir吸附等温式,其吸附自由能为-32.32kJ/mol,吸附为自发进行的物理和化学吸附。     

咪唑啉衍生物与硫脲之间的缓蚀协同效应研究

应用失重法、动电位扫描法、X射线光电子能谱(XPS)研究了咪唑啉缓蚀剂和硫脲复配后对碳钢在CO2盐水溶液中的缓蚀协同作用.实验表明,咪唑啉和硫脲之间存在着良好的协同效应,二者复合后对CO2腐蚀有较好的抑制作用.经XPS检测,试样表面吸附膜有N、S元素存在,而且,于接近基体处,S元素含量相对较高;而在溶液界面处,则N元素含量较高.据此推断缓蚀剂和硫脲在钢样表面可能形成"包含络合物",从而使缓蚀剂膜更加致密,缓蚀效果也更好.     

新型双子表面活性剂在H2S和CO2盐水溶液中对碳钢的缓蚀性能

合成了一系列含有羟基的双子表面活性剂:1,3-双(十二烷基二甲基氯化铵)-2-丙醇(12-3OH-12),1,3-双(十四烷基二甲基氯化铵)-2-丙醇(14-3OH-14),1,3-双(十六烷基二甲基氯化铵)-2-丙醇(16-3OH-16)和1,3-双(十八烷基二甲基氯化铵)-2-丙醇(18-3OH-18).采用静态失重法、极化曲线和交流阻抗技术研究了其在H2S/CO2腐蚀环境中对L360钢的缓蚀作用.结果表明,三种研究方法取得的结论是一致的,缓蚀效果为14-3OH-14>12-3OH-12>16-3OH-16>18-3OH-18.其中,12-3OH-12和14-3OH-14都表现出很好的缓蚀效果,在35mg·L-1的较低浓度下缓蚀率就达95%以上.极化曲线测试结果表明n-3OH-n(n=12,14,16,18)型双子表面活性剂是一种以阳极抑制为主的混合型缓蚀剂.除n=18外,其它三种双子表面活性剂n-3OH-n(n=12,14,16)在L360钢表面的吸附服从朗缪尔等温线,并且属于物理和化学混合吸附.提出了一个用来解释双子表面活性剂在H2S/CO2溶液中缓蚀机理的吸附模型.     

Hydroclathrus clathratus marine alga as a green inhibitor of acid corrosion of mild steel

The corrosion inhibitive and adsorption behaviors of Hydroclathrus clathratus on mild steel in 1 M HCl and 1 M H₂SO₄ solutions at 303, 313 and 323 K were investigated by weight loss, electrochemical, and surface analysis techniques. The results show that H. clathratus acts as an inhibitor of corrosion of mild steel in acid media. The inhibition efficiency was found to increase with increase in inhibitor concentration but to decrease with rise in temperature, suggestive of physical adsorption. The adsorption of the inhibitor onto the mild steel surface was found to follow the Temkin adsorption isotherm. The inhibition mechanism was further corroborated by the results obtained from electrochemical methods. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses supported the inhibitive action of the alga against acid corrosion of mild steel.     

Corrosion inhibitive evaluation and DFT studies of 2-(Furan-2-yl)-4,5-diphenyl-1H-imidazole on mild steel at 1.0M HCl

A novel heterocyclic compound 2-(Furan-2-yl)-4,5-Diphenyl-1H-Imidazole (FDPI) was synthesized by a simple and cost effective one pot synthetic protocol and the structure of FDPI was confirmed by FT-IR, ¹H NMR and ¹³C NMR spectra. The corrosion inhibition activity of FDPI was investigated using gravimetric and electrochemical methods. It resulted a maximum inhibition efficiency of 95.84% at 10 mmolL⁻¹ concentrations of FDPI. The excellent inhibition efficiency is reasoned as the adsorption of FDPI on the mild steel surface as a protective layer immersed in the 1 ​M HCl. The adsorbed layer obeys Langmuir adsorption isotherm and the ΔG^o_ads values of FDPI suggested that process involves physisorption. The polarization curves showed that the FDPI behaves as a mixed type inhibitor. Surface morphology studied by SEM confirmed the formation of a protective film of FDPI on the mild steel surface. The computational studies using DFT have been analyzed for the FDPI to determine the HOMO-LUMO energy gap.     

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.     

Surface morphological and impedance spectroscopic studies on the interaction of polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) with mild steel in acid solutions

The inhibition of mild steel corrosion in aerated acid mixture of 0.5 N H₂SO₄ and 0.5 N HCl solution was investigated using potentiodynamic polarization studies, linear polarization studies, electrochemical impedance spectroscopy, adsorption, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, degree of surface coverage, adsorption kinetics, and surface morphology is investigated. The inhibition efficiency increased markedly with increase in additive concentration. The presence of PEG and PVP decreases the double-layer capacitance and increases the charge-transfer resistance. The inhibitor molecules first adsorb on the metal surface following a Langmuir adsorption isotherm. Both PEG and PVP offer good inhibition properties for mild steel and act as mixed-type inhibitors. Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that PVP offers better protection than PEG.     

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.     

Corrosion inhibition of mild steel by highly stable polydentate schiff base derived from 1,3- propanediamine in aqueous acidic solution

Recently, the hydrolysis of Schiff bases under experimental conditions gives suspicion for their corrosion inhibition performance. The current study employs a stable Schiff base namely, 2,2′-{propane-1,3-diylbis[azanylylidene (E) methanylylidene]}bis(6-methoxyphenol) (LPD) as corrosion inhibitor for mild steel (MS) in 1 M HCl solution. The presence of the characteristic peak of the imine group in UV-visible spectra was taken as an indicator for LPD stability in acidic media. The inhibition action was examined using electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) besides gravimetric measurement. The inhibition efficiency reached 95.93 % for 0.75 mM LPD after 24 h of immersion at 25 °C. This high efficiency is owing to the presence of the characteristic imine group and other heteroatoms and π- electrons of the aromatic benzene rings. The mechanism of inhibition depends on adsorption phenomena on mild steel surface which obeys Langmuir isotherm model. The calculated values of adsorption equilibrium constant (K_ads), adsorption free energy ΔG_ads, adsorption enthalpy ΔH_ads and adsorption entropy ΔS_ads indicated spontaneous exothermic adsorption process of both physical and chemical nature. By rising temperature, the inhibition efficiency of LPD was decreased. The calculated activation energy was increased as the concentration of LPD increased. LPD was considered as a mixed-type inhibitor as indicated from PDP measurements. The obtained surface morphology and composition analysis using SEM/EDS, AFM and FTIR techniques ensures the high efficiency of LPD as corrosion inhibitor.     

Xanthione: A new and effective corrosion inhibitor for mild steel in sulphuric acid solution

The adsorption and inhibition effect of xanthione (XION) on mild steel in 0.5 M H₂SO₄ at 303–333 K were studied using gravimetric and UV–visible spectrophotometric methods. The results obtained show that XION acts as an effective corrosion inhibitor for mild steel in sulphuric acid and inhibition efficiency reaches 98.0% at a very low inhibitor concentration of 10 μM. Inhibition efficiency was found to increase with increase in XION concentration but decreased with temperature suggesting physical adsorption mechanism. Arrhenius law and its transition equation lead to estimate the activation parameters of the corrosion process. XION inhibits the corrosion of mild steel effectively at moderate temperature and adsorbs according to the Langmuir isotherm. Thermodynamic parameters governing the adsorption process have been calculated and discussed. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a XEN–Fe complex. Attempt to correlate the molecular structure to quantum chemical indices was made using density functional theory (DFT).     

Electrochemical investigation of a schiff base synthesized by cinnamaldehyde as corrosion inhibitor on mild steel in acidic medium

The inhibiting effect of (NE)-4-phenoxy-N-(3-phenylallylidene) aniline (PAC) on the corrosion of mild steel in 1.0 M HCl has been studied by electrochemical impedance spectroscopy, and Tafel polarization measurements. The corrosion rate was also calculated theoretically in terms of mm per year and mil per year, using current density values of mild steel in 1.0 M HCl medium. It was found that PAC has a remarkable inhibition efficiency on the corrosion of mild steel especially at high temperatures. The values of E _a obtained in presence of a Schiff base were found to be lower than those obtained in the inhibitor-free solution. The increase of inhibition efficiency percent with temperature increase was associated with the transformation of physical adsorption into chemical adsorption. The thermodynamic functions of adsorption processes have been evaluated and discussed at each temperature. Scanning electron microscope observations of the electrode surface confirmed the existence of a protective adsorbed film of the inhibitor on the electrode surface.     

Study on the Inhibition of Mild Steel Corrosion by Cationic Gemini Surfactant in 1 M HCl

The cationic gemini surfactant 1,2-bis(N-tetradecyl-N,N-dimethylammonium)ethane dibromide (14-2-14) was synthesized using a previously described method. The surfactant was characterized using ¹H NMR. The corrosion inhibition effect of 14-2-14 on mild steel in 1 M HCl at temperatures 30–60°C was studied using weight loss measurements, potentiodynamic polarization measurements and electrochemical impedance spectroscopy. Morphology of the corroded mild steel specimens was examined using scanning electron microscopy (SEM). The results of the studies show that gemini surfactant is an efficient inhibitor for mild steel corrosion in 1 M HCl; the maximum inhibition efficiency (IE) of 98.06% is observed at surfactant concentration of 100 ppm at 60°C. The %IE increases with the increasing inhibitor concentration and temperature. The adsorption of inhibitor on the mild steel surface obeys Langmuir adsorption isotherm. SEM studies confirmed smoother surface for inhibited mild steel specimen.