Corrosion inhibition of mild steel in acidic medium by butyl alcohol

The corrosive behavior of mild steel in 1 M H₂SO₄ solutions contaminated with 3.5 % recrystallized sodium chloride at specific concentrations of butyl alcohol was investigated using potentiodynamic polarization and weight loss technique. The results obtained showed butyl alcohol to be an efficient inhibitor in the acid environment with general decrease in corrosion rate as the concentration of the alcohol increases. The adsorption of the inhibitor on the mild steel obeys the Langmuir adsorption isotherm. The thermodynamic parameters of adsorption deduced reveal a mixed interaction with the steel surface and spontaneous adsorption of butyl alcohol.     

Role of novel oxazocine derivative as corrosion inhibitor for 304 stainless steel in acidic chloride pickling solutions

Inhibition of 304 stainless steel corrosion in acidic chloride pickling (1.0 M HCl) solutions by newly synthesized oxazocine derivative 4 as a corrosion inhibitor have been studied using weight loss, potentiodynamic polarization, and atomic absorption spectroscopy investigations. Potentiodynamic polarization curves show that the inhibitor behaves as a mixed-type. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Langmuir’s adsorption isotherm. The inhibition mechanism of the investigated inhibitor was discussed in terms of its adsorption on the metal surface. The relationship between the molecular structure and the inhibition efficiency was elucidated by quantum chemical calculations.     

Inhibition effect of butan-1-ol on the corrosion behavior of austenitic stainless steel (Type 304) in dilute sulfuric acid

The electrochemical behavior of austenitic stainless steel (Type 304) in 3 M sulfuric acid with 3.5% recrystallized sodium chloride at specific concentrations of butan-1-ol was investigated with the aid of potentiodynamic polarization, open circuit measurement and weight loss technique. Butan-1-ol effectively inhibited the steel corrosion with a maximum inhibition efficiency of 78.7% from weight-loss analysis and 80.9% from potentiodynamic polarization test at highest concentration studied. Adsorption of the compound obeyed the Freundlich isotherm. Thermodynamic calculations reveal physiochemical interactions and spontaneous adsorption mechanism. Surface characterizations showed the absence of corrosion products and topographic modifications of the steel. Statistical analysis depicts the overwhelming influence and statistical significance of inhibitor concentration on the inhibition performance.     

The effect of some triazole derivatives as inhibitors for the corrosion of mild steel in 5 % hydrochloric acid

Corrosion inhibition by triazole derivatives (n-MMT) on mild steel in 5 % hydrochloric acid (HCl) solutions has been investigated by weight loss and electrochemical methods. The results obtained revealed that these compounds performed excellently as corrosion inhibitors for mild steel in HCl solution. Potentiodynamic polarization studies showed that they suppressed both the anodic and cathodic processes and inhibited the corrosion of mild steel by blocking the active site of the metal. The effect of temperature on the corrosion behavior of mild steel in 5 % HCl with the addition of different concentrations of the inhibitors was studied in the temperature range from 303 to 333 K. The associated activation corrosion and free adsorption energies were determined. The adsorption of these compounds on the mild steel surface obeys the Langmuir adsorption isotherm. The effect of molecular structure on the inhibition efficiency has been investigated by quantum chemical calculations. The electronic properties of inhibitors were calculated and are discussed.     

碱性溶液中苯甲酸抗坏血酸酯对钢筋的缓蚀行为

合成了一种苯甲酸抗坏血酸酯(AB), 利用腐蚀电化学和表面分析技术, 在含3.5% NaCl的饱和Ca(OH)₂溶液中研究了化合物对钢筋的缓蚀性能, 结合量化计算和分子动力学模拟对其在铁表面的吸附行为和缓蚀作用机理进行了分析讨论. 结果表明, AB的添加可有效降低钢筋的腐蚀电流密度, 提高钢筋的耐蚀性能, 表明缓蚀剂对Cl^－引起的钢筋腐蚀具有良好的抑制作用, 为阴极型缓蚀剂. 化合物通过吸附和与铁离子形成不溶性络合物, 可在钢筋表面形成一层保护膜, 进而阻碍介质中Cl^－与金属表面的接触, 且吸附符合Langmuir等温吸附规律. 量化计算和分子模拟结果证明, 分子中内酯五元环和苯环既是亲核反应活性中心, 也是亲电反应中心, 化合物通过与铁原子间的共价键合而以平行于铁表面的方式吸附在金属表面.     

Use of rare earth metal salt solutions for corrosion protection of aluminum alloys and mild steel

The rare earth metal salt (REMS) compounds which are non-toxic and inexpensive have been used successfully for the corrosion protection of commercial aluminum alloys as well as of mild steel. The resistance to localized corrosion of aluminum alloys such as Al 2024, Al 6061 and Al 7075 has been greatly improved by immersion in hot cerium salt solutions. Cerium oxides/hydroxides were formed at sites where intermetallic compounds containing copper were located and eliminated the formation of local cathodes. REMS solutions were also used for sealing of anodized layer on Al alloys replacing toxic chromates. In addition to increased corrosion resistance excellent paint adhesion was observed. Cerium nitrate and yttrium sulfate solutions produced the most satisfactory results. Cerium salts were also applied successfully as inhibitors and as pretreatment for the corrosion protection of carbon steel in hot NH₃/water solutions used in absorption heat pumps. Factorial design experiments have been used to determine the optimum concentrations of CeCl₃ and H₂O₂ as well as the treatment time used in the cerating process for mild steel. The corrosion protection provided by the cerated layer was further improved by cathodic polarization in cerium chloride. A dual corrosion protection strategy employing cerating and addition of a REMS to the working solution is expected to provide long-lasting corrosion protection of mild steel. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth. This article was submitted by the author in English.     

The effect of 2-aminoquinoline-6-carboxylic acid on the corrosion behavior of mild steel in hydrochloric acid

The inhibitive effect of 2-aminoquinoline-6-carboxylic acid (AQC) against mild steel corrosion in 1?M HCl solutions was investigated using conventional weight loss, potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy methods. The weight loss results showed that AQC is an excellent corrosion inhibitor since its efficiency increased with the concentration to attain 91.8?% at 500?mg?l^?1. Electrochemical polarization measurements revealed that AQC acted as a mixed-type inhibitor and the results of electrochemical impedance spectroscopy have shown that the change in the impedance parameters, charge transfer resistance and double layer capacitance, with the change in concentration of the inhibitor is due to the adsorption of the molecule leading to the formation of a protective layer on the surface of mild steel. The adsorption was assumed to occur on the steel surface through the active centers of the molecule. The inhibition action of AQC was discussed in view of Langmuir adsorption isotherm. Density functional theory calculations of quantum parameters were used to explain efficiency in relation with molecular structure.     

Inhibition of mild steel corrosion in 5 % HCl solution by 5-(2-hydroxyphenyl)-1,2,4-triazole-3-thione

A new corrosion inhibitor, namely 5-(2-hydroxyphenyl)-1,2,4-triazole-3-thione (5-HTT), has been synthesized and its influence on corrosion inhibition of mild steel in 5 % HCl solution has been studied using weight loss method and electrochemical measurements. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitor is of mixed type, and it inhibits the corrosion of the steel by blocking the active site of the metal. Changes in impedance parameters were indicative of adsorption of 5-HTT on the metal surface, leading to the formation of protective films. The degree of the surface coverage of the adsorbed inhibitors was determined by weight loss measurements, and it was found that the adsorption of these inhibitors on the mild steel surface obeys the Langmuir adsorption isotherm. The effect of the temperature on the corrosion behavior with addition of 5 × 10^?4 M of the inhibitor was studied in the temperature range 30–60 °C. The reactivity of this compound was analyzed through theoretical calculations based on density functional theory to explain the different efficiency of these compounds as a corrosion inhibitor.     

Electrochemical behavior and interfacial bonding mechanism of new synthesized carbocyclic inhibitor for exceptional corrosion resistance of steel alloy: DFTB,MD and experimental approaches

A new carbocyclic compound, namely 3-benzoyl-4-hydroxy-4-phenyl-2,6-(4-methylphenyl)cyclohexane-1,1-dicarbonitrile (MPC) was synthesized and characterized. Herein, MPC was used as green compounds and its anti-corrosion performance was evaluated on the basis of singular role of electron donor–acceptor of MPC molecule. For this purpose, a combination of experimental studies and electronic-/atomic-scale calculations were performed in a bid to understand the electrochemical behavior and interfacial mechanism of MPC molecule based on the correlation between electron charge transfer and adsorption mechanism. Theoretical perspectives are also used to validate the significant inhibition feature achieved by the experimental studies and propose a mechanism of adsorption by using density functional theory (DFT) and molecular dynamic (MD) simulations. According to DFT and MD perspectives, it is found that MPC presents strong interaction with metal surface due to its considerable ability to provide lone pair electrons for electrophilic attacks. This is demonstrated by the high adsorption energy (-5.83 eV) and the parallel configuration of MPC which reveal the formation of molecular self-assembly triggered by an organic-surface interaction. The reliable corrosion stability was provided for 72 h of immersion at an optimum concentration with a fairly high inhibition efficiency (85.81 %) due to the formation of organic inhibitive layer. The addition of MPC inhibitor worked as a sealing agent to reduce the corrosion rate, thus forming a dense and protective barrier on the metal surface. The corrosion resistance of mild steel sample was enhanced significantly due to a high adsorption ability arising from the electron-rich nature of molecule. The formation of organic layer on the metal surface was discussed in relation to the intermolecular interactions and microstructural observations by considering the charge transfer behavior responsible for exceptional corrosion protection of steel alloys. The computational simulations were consistent with the experimental results and confirm the importance of developing eco-friendly hybrid materials.     

Raman and surface-enhanced Raman study of insecticide cyromazine

Surface-enhanced Raman scattering (SERS) spectroscopy is applied to the study of the adsorption of the insecticide cyromazine on Ag colloid. The influence of pH and the aggregation inductors, sodium chloride, potassium nitrate and sodium hydroxide on the adsorption mechanism was investigated. Two different adsorption mechanisms are deduced depending on the experimental conditions: via the N atom bounded to the cyclopropyl (cP) group or through an ionic pairing of protonated amino groups with the chloride adsorbed on the metal. An important contribution of the chemical mechanism was inferred when the interaction with the metal occurs through the N lone pair.     

Corrosion inhibition of carbon steel immersed in a 1 M HCl solution using benzothiazole derivatives

Corrosion inhibition effect of 2-mercaptobenzothiazole (MBT) and 2-aminobenzothiazole (ABT) compounds on ST-37 carbon steel in 1 M hydrochloric acid solution was investigated by electrochemical impedance spectroscopy (EIS), and it was observed that both of these compounds have corrosion inhibition effect on carbon steel. Evaluation of electrochemical behavior in test solutions showed that by increasing the immersion time from 15 to 300 min, corrosion resistance of samples is increased and at the same immersion time MBT has a better corrosion inhibition in comparison to ABT. AFM technique was performed for MBT and ABT. The results of calculations showed superior inhibition efficiency of MBT in comparison to ABT. This can cause easier protonation and consequently adsorption on the metal surface occurs.     

Effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid solution

In this study, the effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid (HCl) solution was investigated by using dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC), cetyl trimethyl ammonium chloride (CTAC), and octadecyl trimethyl ammonium chloride (OTAC) as corrosion inhibitors to uncover their structure–efficiency relationships. The effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in HCl solution was studied under different conditions, such as corrosion inhibitor concentration, temperature, and acidity, and this was done using the weightlessness method. The results obtained show that these inhibitors have high corrosion inhibition effect on A₃ steel, and the corrosion inhibition efficiency is dependent on the length of the alkyl chain. At the same concentration, the longer the alkyl chain, the weaker the corrosion inhibition effect. When the temperature was 50 °C and the concentration of corrosion inhibitor was 70 mg/L, the corrosion inhibition efficiency order of the four cationic surfactants was DTAC > TTAC > CTAC > OTAC. Besides, the experimental results obtained show that the adsorption of the inhibitor on the A₃ steel surface conforms to the Langmuir type isotherm, and then the corresponding adsorption thermodynamic parameters were obtained according to these parameters. It was observed that ΔH, ΔS, and E_a increased with increase in the length of the alkyl chain. The adsorption of the inhibitor on the steel surface is an exothermic, spontaneous, entropy process.     

胡麻籽油咪唑啉类缓蚀剂的制备及其缓蚀性能

以胡麻籽油、羟乙基乙二胺为原料合成咪唑啉中间体,用苄基氯进行改性,得到阳离子咪唑啉衍生物。利用FT IR对合成产物进行了表征,用静态失重法、电化学极化曲线和FESEM对其缓蚀性能进行了评价,并考察了不同缓蚀剂浓度、腐蚀浸泡时间对缓蚀效果的影响,探讨了其在A30钢表面的吸附行为。结果表明,合成的缓蚀剂在盐酸体系中对A30钢有较好的缓蚀性能,在浓度为100mg/L时对低碳钢的缓蚀效率可达87%,并且其产物为阳离子型缓蚀剂,吸附满足Langmuir等温吸附方程。最后采用量子化学方法对其缓蚀剂的缓蚀机理进行了分析。     

氯化硝基四氮唑蓝对钢在盐酸溶液中的缓蚀作用

采用失重法、动电位极化曲线、电化学阻抗谱(EIS)和扫描电子显微镜(SEM)研究了氯化硝基四氮唑蓝(NTBC)在1.0-5.0mo·lL-1HCl溶液中对冷轧钢(CRS)的缓蚀作用.结果表明:NTBC在1.0mo·lL-1HCl溶液中对冷轧钢具有良好的缓蚀作用,且在钢表面的吸附符合Langmuir吸附等温式.缓蚀率随缓蚀剂浓度的增加而增大,但随盐酸浓度和温度的增加而减小.求出了相应的吸附热力学(吸附自由能ΔG0,吸附焓ΔH0,吸附熵ΔS0)和腐蚀动力学参数(腐蚀速率常数k,动力学常数B),并根据这些参数讨论了缓蚀作用机理.动电位极化曲线表明:NTBC为混合抑制型缓蚀剂;EIS谱在高频区呈容抗弧,在低频区出现感抗弧,电荷转移电阻随缓蚀剂浓度的增加而增大.SEM再次表明NTBC对钢在盐酸介质中的腐蚀产生了明显的抑制作用.     

Features of formation of magnetite coatings on low-carbon steel in hot nitrate solutions

The process of anticorrosion magnetite coating (MC) formation on low-carbon steel is studied in alkali-free nitrate converting media at the temperatures of 70–98°C reduced as compared to those used (130–145°C) in standard technologies of steel bluing: formation of such coatings in alkaline nitrate solutions. Alongside with the conventional corrosion-electrochemical methods of analysis of the formed MCs, the regularities of the MC surface reliefs were studied using the method of atomic force microscopy combined with the technique of flicker-noise spectroscopy (FNS) for processing digitized images and obtaining the parameters of the MC surface structure in different nanometer ranges. It was shown that it is necessary to introduce additives of metal nitrates with a low cation radius into the ammonium nitrate converting solution to obtain MCs with a high corrosion stability at the first stage of MC formation and the final stage must consist in the further “passivation” of MCs: MC treatment by aqueous solutions based on nontoxic carboxylates. According to the FNS analysis of the surface structure of the formed MCs, a significant decrease of the FNS “point” factor, an indicator of MC corrosion instability, occurred during the final treatment. On this basis, one could characterize quantitatively the results of accelerated corrosion tests: no steel corrosion occurred on the thus formed coatings for 42 days under standard severe conditions: 100% relative humidity and daily “showering”. The performed study reveals fundamental possibilities for solving the problems of standardization of the anticorrosion coating surface based on the analysis of their surface profile in the nanometer range.     

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.     

Adsorption Isotherms of Cetylpyridinium Chloride with Iron III Salts at Air/Water and Silica/Water Interfaces

The interaction of iron III salts and cetylpyridinium chloride (CPC) has been studied at the air/water and silica/water interfaces. The surface tension of cetylpyridinium chloride has been determined in aqueous solutions in the presence of iron III chloride and iron III nitrate at two constant pH values, namely, 3.5 and 1.2. It is shown that the surface tension of the cationic surfactant depends upon the ionic strength of the solution through the pH adjustment in the presence of the former salt but not in the presence of the latter. The effect of iron III nitrate on the surface tension of CPC is similar to that of potassium nitrate, indicating that the iron III various-hydrolyzed species do not interfere with the composition of the air/water interface. The competitive adsorption of iron III nitrate salt and the cationic surfactant at a silica/water interface was next investigated. The adsorption isotherms were determined at pH 3.5. It is shown that although the iron III ions, which were added to the silica dispersion in the presence of the cetylpyridinium ions, were strongly bound to the anionic surface sites, the surfactant ions are not salted out in the solution but remain in close vicinity of the silica surface. Conversely as the cationic surfactant is added first to the silica dispersion in the presence of the adsorbed iron III ions, the metal ions and the surfactant ions are both coadsorbed onto the silica surface. It is suggested that iron III hydrolyzed or free cations and the cationic surfactant molecules may not compete for the same adsorption sites onto the silica surface.     

氯离子对模拟混凝土孔隙液中钢筋腐蚀行为的影响

应用动电位扫描法研究钢筋在模拟混凝土孔隙液中的腐蚀电化学行为以及氯离子的影响作用,并根据阳极极化曲线的变化揭示钢筋表面钝化膜的击穿电位及其变化规律,得出当溶液pH值分别为12.50和12.00时,由氯离子侵蚀引起的钢筋局部腐蚀,其钝化膜击穿电位突降的浓度临界值.     

甲基丙烯酸二甲氨基乙酯类离子液体 对Q235钢的缓蚀性能

以甲基丙烯酸二甲氨基乙酯为母体、 对氯甲基苯乙烯为季铵化试剂, 合成了一种具有疏水结构的甲基丙烯酸二甲氨基乙酯型离子液体(DEMA). 通过失重实验、 电化学分析、 原子力显微镜(AFM)、 接触角测试和量子化学计算等研究了DEMA在1 mol/L盐酸中对Q235钢的缓蚀性能, 并揭示了其在Q235钢表面的吸附行为和吸附机理. 失重实验结果表明, DEMA在盐酸中对Q235钢具有优异的缓蚀效果, 且在较高温度(60 ℃)下也能保持高效吸附; 电化学实验结果与失重测试结果一致; 接触角测试结果表明, DEMA可明显增强Q235钢表面的疏水性; 分析热力学参数可知, DEMA在Q235钢表面的吸附为自发、 放热过程, 符合Langmuir等温式, 且以化学吸附为主; 量子化学计算结果证实DEMA的结构中包含大量吸附活性位点.     

十八胺基分子组装体在碳钢表面的作用机理与模拟

应用分子动力学模拟明确了以β-环糊精(β-CyD)为主体、 十八胺(ODA)为客体的分子组装体(CDDA)的最优空间构型, 并采用动态失重、 电化学极化与阻抗测试结合扫描电子显微镜、 原子力显微镜、 接触角、 X射线光电子能谱(XPS)与衰减全反射红外光谱(ATR-FTIR)等表面分析手段, 研究了CDDA对Q235碳钢在蒸汽凝结水中的缓蚀机理. 结果显示, CDDA的4种构型可共存于组装体系内; 35 ℃下, 添加1 mmol/L CDDA对碳钢的缓蚀率达94.1%; 添加CDDA不改变腐蚀机理, 但可同时抑制电化学反应的阴、 阳极过程, 并显著提升极化阻抗, 属于阳极抑制为主的混合型缓蚀剂. XPS和ATR-FTIR结果均表明, CDDA在碳钢/溶液界面释放客体ODA, 并由其自发吸附组装形成疏水膜, 吸附过程符合Langmuir等温式. 分子动力学模拟与量子化学计算结果支持上述ODA释放并于金属表面组装成膜的推断.