硫酸根离子对铁在弱碱性溶液中阳极溶解和钝化行为的影响

采用浸泡实验, 电化学测试和表面分析技术研究了硫酸根离子浓度对铁在稀碳酸氢钠溶液中开路状态和阳极极化行为的影响. 在无硫酸根离子及含有少量硫酸根离子的碳酸氢钠溶液中, 铁的开路电位约为(-0.225±0.005) V, 并呈现钝化状态, 其电化学阻抗很大, 腐蚀速率较低. 在含有较高浓度硫酸根离子的碳酸氢钠溶液中, 铁的开路电位为(-0.790±0.010) V并呈现活性溶解状态, 其电化学阻抗较小, 腐蚀速率较高, 同时阳极极化曲线上能观察到活化-钝化转变现象. 由于铁在含有较高浓度硫酸根离子的碳酸氢钠溶液中处于活化状态, 阳极极化曲线上存在数个电流峰. 足够高的硫酸根离子浓度会导致铁表面预先形成或转变而成的氧化膜失效. 相比于自然曝氧状态, 在除氧条件下较低的硫酸根离子浓度即可引起铁在碳酸氢钠溶液中由钝态向活性溶解态的转变.     

扫描电化学显微镜原位表征pH值对核电蒸汽发生器合金腐蚀行为的影响

用扫描电化学显微镜(SECM)和电化学阻抗谱(EIS)原位表征了溶液pH值对核电蒸汽发生器800 合金溶液中的腐蚀行为的影响. 实验结果表明：在酸性氯化钠溶液中,SECM探针渐进曲线为正反馈,表明800合金为活化阳极溶解,腐蚀电位下的EIS 图呈现完整的单容抗弧特征;而在中性或者碱性溶液中,SECM探针渐进曲线为负反馈,表明800 合金为自钝化,不同阳极电位下的EIS 图均呈现不完整的容抗弧特征,但随着阳极极化电位的增加,EIS 谱容抗弧半径减小,表明钝化膜的耐蚀性下降;SECM二维扫描图像结果显示探针电流增加,表明电极表面活性增加,即钝化膜的溶解速度增加. 而在中性或者碱性溶液中的SECM二维图像中均可观察到若干活性点,这可能与晶界或者金属夹杂物等有关.     

扫描电化学显微镜原位表征pH值对核电蒸汽发生器合金腐蚀行为的影响(英文)

用扫描电化学显微镜(SECM)和电化学阻抗谱(EIS)原位表征了溶液pH值对核电蒸汽发生器800合金溶液中的腐蚀行为的影响.实验结果表明:在酸性氯化钠溶液中,SECM探针渐进曲线为正反馈,表明800合金为活化阳极溶解,腐蚀电位下的EIS图呈现完整的单容抗弧特征;而在中性或者碱性溶液中,SECM探针渐进曲线为负反馈,表明800合金为自钝化,不同阳极电位下的EIS图均呈现不完整的容抗弧特征,但随着阳极极化电位的增加,EIS谱容抗弧半径减小,表明钝化膜的耐蚀性下降;SECM二维扫描图像结果显示探针电流增加,表明电极表面活性增加,即钝化膜的溶解速度增加.而在中性或者碱性溶液中的SECM二维图像中均可观察到若干活性点,这可能与晶界或者金属夹杂物等有关.     

镁合金在含F－的NaOH溶液中钝化行为的电化学研究

采用极化曲线、电容-电位曲线、Mott-Schottky分析以及电化学阻抗(EIS)等电化学方法研究了镁合金在含F^－ NaOH溶液中的阳极钝化行为. 结果表明, 在－1.2～1.8 V的电位范围内, 镁合金在含F^－的NaOH溶液中发生阳极钝化. 所形成的钝化膜表现出n型半导体的导电特性. 在0.7～1.8 V的电位范围内, 随着F^－浓度增大, 镁合金的阳极极化电流密度呈现出随着电位升高而逐渐增大的趋势, 随着F^－浓度增大这一趋势逐渐减弱. 并且F^－浓度的增大使得镁合金表面空间电荷层电容和钝化膜的载流子密度都不断减小. 通过极化曲线和电化学阻抗共同说明, 在5%的Na₂SO₄溶液中, NaOH溶液中阳极钝化后的镁合金随着钝化体系中F^－浓度的增加其耐蚀性逐渐减弱.     

铬对碳钢在NaHCO3/NaCO3缓冲溶液中所成钝化膜半导体性能的影响

应用电化学阻抗谱技术研究铬对碳钢钝化膜半导体性能的影响.实验表明,在碳酸氢钠/碳酸钠缓冲溶液中碳钢形成的钝化膜具n型半导体特性,而含有3%铬的碳钢钝化膜则呈n-p型半导体特性,随着成膜电位的增加,以上两种钝化膜之Mott-Schottky直线部分的斜率均呈增大的趋势,表明成膜电位升高,膜内的杂质密度减小,但铬的加入使得碳钢钝化膜的施主密度增加约一个数量级,从而增加了碳钢点蚀发生的趋势.EIS分析表明:铬的加入降低了钝化膜的传递电阻R1和膜电阻R2,特别是膜电阻R2下降达3个数量级,这就有可能增加碳钢在高pH值环境中的腐蚀.     

碳钢在生物膜和硫化物膜下的电化学腐蚀行为

应用丝束电极技术比较了SRB生物膜以及硫化物膜对Q2 35碳钢腐蚀过程的影响机制 ,采用电位、电流扫描技术测试了生物膜和FeS膜下的碳钢腐蚀不均匀性特征 ,发现由于膜的导电性致使表面电位扫描已不能作为膜下局部腐蚀的判据 .动电位扫描表明无氧近中性溶液中 ,硫化物膜对碳钢具有一定保护作用 .电化学阻抗谱显示 ,硫化物膜电容增加缓慢 ,其极化电阻Rp 随时间呈先增后降的趋势 .与硫化物膜相比 ,生物膜表现出极大的电容 (10 4 ～ 10 5μF/cm2 ) ,且膜电容随时间呈S型增加 ,而极化电阻Rp 则呈指数下降 ,由此可知生物膜加速了腐蚀     

曲唑酮的两步法制备及对碳钢的缓蚀机理

以3-氯苯胺、N-氯丙基二乙醇胺和吡啶三唑酮为原料，两步法制备出曲唑酮（TZD）.通过动态失重、极化曲线与电化学阻抗谱研究了TZD在0.5 mol/L盐酸溶液中对20#钢的缓蚀性能；借助扫描电子显微镜、原子力显微镜、衰减全反射红外光谱与吸附活化参数分析研究了TZD在碳钢表面的作用机理.结果表明，TZD可显著降低碳钢在盐酸溶液中的腐蚀速率，缓蚀率随TZD添加浓度的增加而增大，随温度升高而降低；298 K下，添加6 mmol/L TZD时，缓蚀率达95.8%；TZD可自发吸附组装于碳钢表面，同时抑制腐蚀反应的阴、阳极过程，显著增加界面极化阻抗；吸附为放热过程，符合Langmuir等温式.理论计算结果显示，TZD倾向以平行取向组装于碳钢表面.     

不锈钢钝化膜耐蚀性与半导体特性的关联研究

通过极化曲线、交流阻抗谱和钝化膜半导体特性等电化学测量，研究了经电化学阳极氧化处理的不锈钢钝化膜在0.5 mol•L^-1 NaCl溶液中耐蚀性能与其半导体特性的关系，进一步探索电化学改性处理不锈钢钝化膜的耐蚀机理. 结果表明，不锈钢钝化膜在负于平带电位范围表现为p型半导体，在高于平带电位范围表现为n型半导体，这主要与组成钝化膜的Fe和Cr氧化物半导体性质有关. 与自然条件下形成的不锈钢钝化膜比较，发现经过电化学阳极氧化后不锈钢钝化膜具有较低的施主与受主浓度，平带电位负移，说明阴离子在钝化膜表面发生吸附. 低的施主与受主浓度及钝化膜表面负电荷的增强，可有效排斥侵蚀性Cl^－在钝化膜表面的特性吸附，有利于提高不锈钢的耐局部腐蚀性能.     

水性环氧铝粉涂层/碳钢体系的腐蚀电化学行为

应用电化学阻抗谱(EIS)和扫描振动电极技术(SVET)研究了碳钢基体上含人造缺陷的水性环氧铝粉涂层浸泡在3.5%NaCl溶液中的腐蚀电化学行为.结果表明,浸泡初期,涂层缺陷处为阳极活性区,涂层阻抗随时间延长逐渐降低,活性区逐渐扩展;之后,由于腐蚀产物的自修复作用使整个涂层/金属界面电化学反应活性降低,导致涂层阻抗快速增加.浸泡后期,由于腐蚀介质渗入到涂层/基体界面,出现了更多的阳极活性区,涂层产生破坏剥离.     

锈层下碳钢的腐蚀电化学行为特征

采用极化曲线、线性极化电阻(LPR)和电化学阻抗(EIS)研究了海水中带锈碳钢的电化学行为,结果发现:长期浸泡的内锈层对电极过程有较大影响;短期浸泡,LPR和EIS测定的极化电阻(Rp)逐渐增大;而长期浸泡,Rp却逐渐减小;随着浸泡时间的延长,Rp出现了先增大后减小的变化趋势.将锈层逐层剥离后研究了碳钢的电化学行为,并结合傅里叶变换红外(FTIR)光谱和横截面结构分析表明,这主要是因为长期浸泡后,内锈层中出现了具有较高电化学活性的β-FeOOH,并且其含量随着浸泡时间的延长而逐渐增加.当进行电化学测试时,在对体系进行一定程度极化的过程中,β-FeOOH参与了阴极还原反应,使电极过程不再是简单的阳极金属溶解和阴极氧还原,加快了阴极反应速度,从而导致Rp逐渐减小.     

Electrochemical interferometry of a carbon steel in 5–20 ppm KGR-134 inhibited seawater

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the number of the fringe evolutions during the corrosion test of a carbon steel in blank seawater and with seawater with different concentrations of a corrosion inhibitor. In other words, the anodic dissolution behaviors (corrosion) of the carbon steel were determined simultaneously by holographic interferometry, an electromagnetic method, and by the electrochemical impedance spectroscopy (EIS), an electronic method. So, the abrupt rate change in the number of the fringe evolutions during corrosion test, EIS, of the carbon steel is called electrochemical interferometry. The corrosion process of the steel samples was carried out in blank seawater and seawater with different concentrations, 5–20 ppm, of KGR-134 corrosion inhibitor using the EIS method, at room temperature. The electrochemical interferograms of the carbon steel in different solutions represent a detail picture of the rate change of the anodic dissolution of the steel throughout the corrosion processes. Furthermore, the optical interferometry data of the carbon steel were compared to the data which were obtained from the EIS tests. Consequently, holographic interferometry is found to be very useful as an electrochemical interferometer for monitoring the anodic dissolution behaviors of metals in aqueous solutions, in which the number of the fringe evolutions of the steel samples can be determined in situ.     

WBE联合EIS技术研究缺陷涂层下金属腐蚀

用电化学阻抗谱(EIS)结合丝束电极(WBE)技术研究了缺陷涂层浸泡在3.5%(质量分数)NaCl溶液中的劣化过程.从浸泡开始到完好涂层鼓泡失效,缺陷涂层丝束电极阻抗响应一直是缺陷区电极腐蚀反应过程特征,而完好涂层的劣化过程和涂层下的腐蚀反应过程特征被"平均掉".根据电极表面的电流分布,结合阻抗谱技术实现了对表面任意局部阴极和阳极区阻抗测试.研究发现,浸泡开始时,缺陷涂层阴极电流和阳极电流均出现在缺陷区,随着腐蚀过程的发展,阳极电流仍然保持在缺陷区,但阴极电流逐渐向完好涂层下扩展.根据实验结果,对缺陷处和涂层下金属腐蚀反应发生发展的机理进行了深入讨论.     

Electrochemical study of the corrosion behaviour of carbon steel in fracturing fluid

Corrosion behaviour of carbon steel (K-55) in fracturing fluid was studied with a rotation cylinder electrode, under static and rotation conditions by means of several electrochemical techniques which are as follows: open circuit potential (OCP) decay, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). The corrosion rate was determined by weight loss measurements. The electrode surface after a prefixed immersion time was characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that carbon steel showed anodic dissolution behaviour that increased under rotating condition. The cathodic polarisation current density also increased with the electrode rotation due to the increased oxygen diffusion on the electrode surface. Two different oxide layers were formed: a dark, thin layer of magnetite tightly adhering to the electrode surface, characterised by localised corrosion spots, and a porous reddish layer of poorly adhering hematite (Fe₂O₃) and maghemite (γ-Fe₂O₃). Under higher rotation rate, the developed oxide layer was not so stable, owing to the shear stress induced between the solution and the specimen surface, enhancing the corrosion rate.     

Corrosion protection of carbon steel in acidic media by expired bupropion drug; experimental and theoretical study

The effects of expired bupropion on the corrosion protection of carbon steel in hydrochloric acid (1.0 M) and sulfuric acid (0.5 M) solutions were examined by Fourier transform infrared (FTIR) spectroscopy, Tafel polarization and electrochemical impedance spectroscopy (EIS). Bupropion concentrations in both acid solutions were raised, which improved corrosion prevention. Bupropion was a mixed inhibitor because it retarded the anodic and cathodic processes, as indicated by polarization data. The inhibition efficiency decreased with the increasing temperature from 25 to 55 °C. In the presence of bupropion, the activation energies of corrosion in both acid solutions increased. The thermodynamic quantities were deduced from the influence of temperature on the corrosion process of carbon steel in both acid media. Bupropion adsorption on carbon steel followed the Langmuir adsorption isotherm. The polarization data yielded outcomes consistent with the results arising from impedance measurements. FTIR spectroscopy showed the active sites of bupropion molecule during adsorption on the alloy surface. The theoretical study and molecular dynamics simulation of bupropion was done by a density functional theory (DFT) approach to realize the effects of molecular structure on the inhibitive action of bupropion.     

Indole‐3‐acetic acid and N‐acetyltryptophan corrosion inhibition effects on mild steel in 1 M hydrochloric acid solution

Corrosion inhibition of indole‐3‐acetic acid and N‐acetyl tryptophan on carbon steel was investigated using polarization and electrochemical impedance spectroscopy (EIS). Polarization results revealed that corrosion inhibitors could reduce the rate of cathodic and anodic reactions on metal surface. EIS analysis showed inhibition efficiency of indoles increases by increasing the inhibitor concentration. The maximum inhibition efficiency was 97% and 80% in solutions containing 10 mM indole‐3‐acetic acid and 10 mM N‐acetyl tryptophan, respectively. The adsorption of inhibitors was found to follow Langmuir isotherm. Adsorption and film formation of inhibitors on the metal substrate were confirmed by calculating thermodynamic adsorption parameter (ΔG⁰_ads) and characterization of exposed metals' surface through contact angle measurements. Copyright © 2014 John Wiley & Sons, Ltd.     

高温高浓度溴化锂溶液对低合金钢的电化学行为作用

通过电化学测式技术和化学浸泡方法 ,在高温 55%LiBr +0 .0 7mol/LLiOH溶液中研究了MoO4 2 - 对低合金钢的电化学行为作用 .结果表明 ,MoO4 2 - 作为阳极型缓蚀剂能促进钝化 ,阻滞了阳极和阴极反应 .Na2 MoO4 浓度达到 2 0 0mg/L时 ,可有效地抑制低合金钢的活性溶解 .低合金钢中添加Cr和Ni元素可改善耐蚀性能 ,而AI元素则使耐蚀性能变劣 .Mo元素参与成膜过程 ,Cr和Mo元素的协调作用 ,使A钢能在较低Na2 MoO4 浓度下进入钝态     

Numerical Simulation for Crevice Corrosion of 304 Stainless Steel in Sodium Chloride Solution

The authors presented a mechanistic model describing the chemical reactions within a corroded thin, nar-row crevice. In the mathematical model, a two-dimensional steady-state was used to predict the crevice pH profile by taking into account dissolved oxygen and hydrogen ions within the crevice. It consists of six parallel electrochemical reactions: multi anodic reactions(Fe, Cr, Ni dissolution reactions) and three cathodic reactions(the oxygen reduction, the hydrogen reaction and water dissociation). Current density distribution and oxygen concentration distribution were determined to be corresponding to the evolution of potential distribution within the crevice. The contribution of each metal reaction to the overall corrosion process was in proportion to the mole fraction, and the simulation pro-vided a good agreement with published experimental results for the crevice corrosion of stainless steel in sodium chloride solution.     

缓蚀剂对船用钢在潮湿大气中的防蚀研究

模拟 90 7A钢在海水的潮湿大气环境和表面覆有薄层缓蚀剂液膜状态下其腐蚀受抑制的情况 ,利用恒电量仪连接ACM控头 ,监测其腐蚀状态 ,结合电化学阻抗谱 (EIS)的测量 ,探讨 90 7A钢在薄层缓蚀剂液膜下的腐蚀受到抑制机理 .结果表明 :此时大气腐蚀反应已转变为阳极过程控制占优势 ,在浸润后期的EIS呈现出由腐蚀介质扩散和电化学放电混合控制特征 ,如果利用恒电量激励下的等效电路模型解析 ,则可以更清楚地获知薄层缓蚀剂液膜下金属表面膜层的信息