Electrochemical properties and corrosion inhibition of AA6061 in tropical seawater

The corrosion inhibition of aluminum and its alloys is the subject of tremendous technological importance due to the increased industrial applications of these materials. This study reports the results of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) on the corrosion inhibition of AA6061 aluminum alloys in seawater using sodium benzoate as an inhibitor. The electrochemical measurements for aluminum alloys in seawater after varied immersion period showed that the presence of sodium benzoate significantly decreases the corrosion currents densities (i_corr), corrosion rates and double layer capacitance (C_dl), as simultaneously increase the values of polarization resistance (R_p). Charge transfer process and development of thin film on the specimen have been proven by morphology study using SEM.     

AZ31和AZ61镁合金在模拟海水中的腐蚀电化学行为

应用极化曲线、电化学阻抗谱方法研究了两种Mg-Al-Zn系合金——AZ31和AZ61在模拟海水中的腐蚀电化学行为.根据两种镁合金在浸泡过程中腐蚀介质pH值的变化以及扫描电子显微镜对合金微观金相组织和腐蚀形貌的观察,讨论了镁合金的腐蚀机理及合金元素Al的含量对镁合金耐蚀性能的影响.结果表明,AZ61镁合金具有比AZ31镁合金更好的耐蚀性能,其原因主要是AZ61镁合金中Al含量较高使合金的微观组织结构更有利于耐蚀性能的提高.     

Effects of Ca and Ag addition and heat treatment on the corrosion behavior of Mg-7Sn alloys in 3.5 wt.% NaCl solution

The effects of 1 wt.% Ca or 1 wt.% Ca + 1 wt.% Ag addition and heat treatment on the corrosion behavior of Mg-7Sn (wt.%) alloy in 3.5 wt.% NaCl solution were investigated by electrochemical measurements and immersion tests. The alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that all alloys were corroded by pitting corrosion and grain boundary corrosion and further corroded with time going. Loose layers of compounds, including Mg (OH)₂, MgO, SnO₂, and other compounds containing Ca and Ag elements, were calibrated on the surface of corroded Mg-7Sn-1Ca-1Ag alloy. The Ca addition improved the corrosion resistance of Mg-7Sn alloy due to the formation of relatively stable compounds containing calcium element and grains refinement. Furthermore, the solid solutioned alloys obtained a superior corrosion resistance due to the dissolve of eutectic Mg₂Sn phase and homogenization treatment. However, the aging treatment is slightly detrimental to the corrosion resistance of Mg-7Sn alloys with the formation of Mg₂Sn precipitates. In conclusion, the aged Mg-7Sn-1Ca-1Ag alloy exhibited a better corrosion resistance and a noticeable micro-hardness property compared with those of as-cast Mg-7Sn alloy. And this study provides an important idea for the research on the comprehensive properties of Mg-Sn alloys.     

Micro‐arc oxidation and electrophoretic deposition of nano‐grain merwinite (Ca3MgSi2O8) surface coating on magnesium alloy as biodegradable metallic implant

Magnesium alloys are promising biomaterials as biodegradable implant for orthopedic applications. However, their low corrosion resistance and poor bioactivity have prohibited their implant applications. In order to enhance these two properties, a nano‐grain merwinite coating was prepared on magnesium alloy. Its corrosion and the bioactivity behavior were characterized with electrochemical and immersion tests. The results showed that the nano‐grain merwinite coating can improve both the corrosion resistance and the bioactivity of the magnesium alloy making it an appropriate material for biodegradable bone implants. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrochemical behavior of Ni-Al-Fe alloys in simulated human body solution

An investigation about the corrosion resistance of Ni-Al-Fe intermetallic alloys in simulated human body fluid environments has been carried out using electrochemical techniques. Tested alloys included 57 (wt%) Ni-(20 to 30) Al-(12 to 23) Fe using the Hank's solution because the high corrosion resistance provided by protective Al₂O₃ external layer. For comparison, AISI 316L type stainless steel has also been used. Electrochemical techniques included potentiodynamic polarization curves, electrochemical impedance spectroscopy, and electrochemical noise measurements. The different techniques have shown that these alloys showed a similar or higher corrosion resistance than conventional AISI 316L type stainless steel, and this corrosion resistance decreased as the Al content in the alloy increased. The alloys were susceptible to pitting type of corrosion on the interdendritic Ni-rich phases.     

Corrosion behaviour of an Mg–Y–RE alloy used in biomedical applications studied by electrochemical techniques

Magnesium, due to its biocompatibility, a necessity in metabolic processes, and better mechanical properties than polymer, is an ideal candidate for biodegradable implants. The main actual limitation for the use of magnesium alloys is its too fast degradation rate in the physiological environment. The corrosion behaviour of an Mg–Y–RE magnesium alloy in two different physiological solutions (artificial plasma (AP) and simulated body fluid (SBF)) was investigated, using electrochemical impedance spectroscopy (EIS).The investigation showed that SBF is significantly more aggressive than AP with regard to the polished surface. A large difference in the corrosion rate and mechanisms (uniform or localized corrosion) is observed as a function of the buffer capacity of the media, but also of the carbonate and chloride content. For temporary surface protection, the formation of an approximately 350–400 nm dense hydroxide layer is obtained by electrochemical anodising. An increase of the corrosion resistance of the treated alloy for both physiological solutions is obtained, and this is especially noticeable for a long immersion time in AP.     

Inhibition effect of cerium in hybrid sol–gel films on aluminium alloy AA2024

Aluminium alloys such as AA2024 are susceptible to severe corrosion attack in aggressive solutions (e.g. chlorides). Conversion coatings, like chromate, or rare earth conversion coatings are usually applied in order to improve corrosion behaviour of aluminium alloys. Methacrylate‐based hybrid films deposited with sol–gel technique might be an alternative to conversion coatings. Barrier properties, paint adhesion and possibly self‐healing ability are important aspects for replacement of chromate‐based pre‐treatments. This work evaluates the behaviour of cerium as corrosion inhibitor in methacrylate silane‐based hybrid films containing SiO₂ nano‐particles on AA2024. Hybrid films were deposited on aluminium alloy AA2024 by means of dip‐coating technique. Two different types of coating were applied: a non‐inhibited film consisting of two layers (non‐inhibited system) and a similar film doped with cerium nitrate in an intermediate layer (inhibited system). The film thickness was 5 µm for the non‐inhibited system and 8 µm for the inhibited system. Film morphology and composition were investigated by means of GDOES (glow discharge optical emission spectroscopy). Moreover, GDOES qualitative composition profiles were recorded in order to investigate Ce content in the hybrid films as a function of immersion time in 0.05 M NaCl solution. The electrochemical behaviour of the hybrid films was studied in the same electrolyte by means of EIS technique (electrochemical impedance spectroscopy). Electrochemical measurements provide evidence that the inhibited system containing cerium displays recovery of electrochemical properties. This behaviour is not observed for the non‐inhibited coating. GDOES measurements provide evidence that the behaviour of inhibited system can be related to migration of Ce species to the substrate/coating interface. Copyright © 2010 John Wiley & Sons, Ltd.     

An investigation of carbon steel corrosion inhibition in hydrochloric acid medium by an environmentally friendly green inhibitor

The inhibition effect of polyphenols extracted from olive mill wastewater (PP) on carbon steel in 1.0 M HCl solution was studied. Inhibition efficiency of PP was carried out by using chemical (weight loss method) and electrochemical techniques [potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)]. The effect of temperature and immersion time on the corrosion behavior of carbon steel in 1.0 M HCl with addition of an extract was also studied. The results show that PP acts as a very good inhibitor, and the inhibition efficiency increases with the concentration of PP and decreases with rising temperature. Polarization curves show that PP behaves as a mixed-type inhibitor in hydrochloric acid. Data, obtained from EIS measurements, were analyzed to model the corrosion inhibition process through an appropriate equivalent circuit model; a constant phase element has been used. EIS shows that charge-transfer resistance increases and the capacitance of double layer decreases with the inhibitor concentration, confirming the adsorption process mechanism. The activation energy as well as other thermodynamic parameters for the inhibition process were calculated. The adsorption of PP obeys the Langmuir adsorption isotherm.     

Corrosion inhibition of zinc in aqueous acidic media using a novel synthesized Schiff base – an experimental and theoretical study

Abstract

The kinetics of H₂ production during Zn corrosion in 0.5?M HCl without and with various additives of N,N'-bis-(1-hydroxyphenylimine)-2,5-thiophenedicarboxaldehyde (HPTD) was studied using gasometry and electrochemical techniques. The surface of the corroded Zn samples was investigated using SEM and Optical Profilometry. The rate of H₂ production (RHP) increased with the immersion time and temperature. Presence of HPTD mitigated RHP due to an adsorption process. The electrochemical impedance spectroscopy showed that HPTD had a good inhibitive effect. Polarization data proved that HPTD acted as a surface-active mixed-type inhibitor. Some thermodynamic parameters were deduced and discussed. Theoretical calculations were also conducted to corroborate the capability of HPTD to protect Zn surface from corrosion process.     

Fe基非晶和纳米晶合金晶化及电化学腐蚀行为

应用单辊甩带法制备非晶态Fe78Si13B9和Fe73.5Si13.5B9Nb3Cu1薄带,并以非晶晶化退火法制备出纳米晶Fe73.5Si13.5B9Nb3Cu1薄带.利用X射线衍射(XRD)仪和示差扫描量热计(DSC)对该非晶薄带的非晶特性及其晶化过程进行了研究.并用电化学极化曲线的方法和电化学阻抗技术研究了非晶态Fe78Si13B9和纳米晶Fe73.5Si13.5B9Nb3Cu1合金在1mol/LNaOH溶液里的电化学腐蚀行为,用SEM对极化测试后的试样形貌进行了观察;同时还研究了不同的热处理温度对材料结构及在1mol/LNaOH溶液里耐腐蚀性能的影响.结果表明,该非晶薄带的晶化过程分为两步;纳米晶比非晶合金的耐腐蚀性要好;且随着热处理温度的升高,非晶和纳米晶的耐腐蚀性能都得到提高.     

卷绕式铅酸蓄电池板栅材料的研究

0引言制作高功率的卷绕式铅酸蓄电池,目前日益受到广泛关注。薄型极板是卷绕式铅酸蓄电池的显著特点之一。很薄的极板决定着卷绕式铅酸电池的优良性能。制造薄极板的前提是要先制得薄板栅。卷绕式铅酸蓄电池的板栅一方面要起到传统板栅支撑活物质与作为导电电极的作用,另一方面要求这种合金制成板栅后可以卷绕,所以硬度与脆性不能太大。此板栅一般要加工成厚度为0.2￣0.5mm的铅箔。而有报道制得更薄的板栅,厚度达到0.05￣0.08mm,可以说做到了薄如纸[1]。制作这样薄的板栅一般采用压延的方式,首先的问题就是选择何种合金材料,然后是其电化学…     

Electrochemical characterisation of dental alloys: its possibilities and limitations

Dental alloys are metallic biomaterials which have a broad variation of composition compared to technical alloys. It is therefore in the interest of patients and technicians to conduct a good assessment of the electrochemical behaviour of dental alloys in order to collect information about their corrosion resistance. The purpose of this work was to demonstrate possibilities and limitations of two electrochemical techniques: the voltammetry of immobilised microparticles (ViMP) onto lead, and cyclic voltammetry measurements with the help of the mini-cell system (MCS). Based on fingerprints obtained from ViMP it was possible to analyse and differentiate the dental alloys. The results obtained by MCS were comparable with ViMP, but give a better understanding of the corrosion behaviour of the materials.     

A closer look at the internal corrosion test for automotive heat exchangers: the OY water test

Nowadays, automotive heat exchangers are mainly made from aluminum. Over the last few decades, the development of aluminum brazing sheet has been mainly focused on the improvement of the external corrosion resistance. Recently, the interest of the heat exchanger manufacturers has also moved toward the assessment of the internal corrosion resistance. Accelerated tests are used to simulate in‐service conditions. These tests are crucial as they provide information to predict the material and product performance. Various internal corrosion tests have been developed, the so‐called ‘OY water tests’. Among all companies, the testing parameters can be varied in terms of ion concentrations or pH. Although the OY water tests are constantly being improved, there is so far no common internal corrosion standard as existing for external corrosion assessment. The present work aims at providing better understanding corrosion mechanisms encountered in the OY water media. The role of various elements present in the solution, cupric, chloride, sulfate ions, has been determined. These parameters were assessed via immersion testing. In order to get better understanding of the corrosion mechanism, electrochemical analysis combined with SEM characterization was carried out. The electrochemical analysis enables the understanding of the thermodynamics and kinetics of the corrosion process while immersion tests are performed to quantify the level of corrosion and follow the surface evolution over time. Copyright © 2010 John Wiley & Sons, Ltd.     

Dissolved carbon dioxide effect on the behavior of carbon steel in a simulated solution at different temperatures and immersion times

Dissolved carbon dioxide effect on the behavior of carbon steel (0.4%carbon), in a simulated solution at different temperatures and immersion times, has been investigated using different techniques as potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy. The observation of the steel surface was done by scanning electron microscopy. All measurements reveal that the corrosion resistance is strongly dependent on both the temperature and immersion times. The corrosion resistance of carbon steel decreases in the solution considered as the temperature increases from 20?°C to 50?°C. Potentiodynamic polarization curves showed that cathodic and anodic current densities increase with the increased temperature. Besides, the study concluded that the addition of CO₂ gas to the simulated solution affects negatively the corrosion resistance in one hand and that, on the other hand, the higher the time of immersion the higher is the resistance to corrosion.     

Effects of exposure time on the anodic dissolution of Monel-400 in aerated stagnant sodium chloride solutions

The anodic dissolution of Monel-400 (63.0% Ni, 28–34% Cu) alloy after its immersion in freely aerated stagnant 3.5% NaCl solutions for 0, 24, and 72 h has been investigated. The study was carried out using a variety of electrochemical techniques and gravimetric measurements after varied exposure periods (5–160 days). The work was complemented by scanning electron microscopy and energy dispersive X-ray analyzer (SEM/EDX) investigations. The electrochemical measurements showed that Monel suffers both general and pitting corrosion. The severity of uniform corrosion decreased, while pitting one increased with increasing the immersion time to 24 h and further to 72 h before measurements. Gravimetric data indicated that the weight loss increased, while the corrosion rate decreased for Monel with time. SEM images and EDX profile analyses confirmed that the corrosion of Monel after 160 days immersion in NaCl solutions occurs due to the selective dissolution of nickel.     

Exploration of the potentials of imidazole-based inhibitor package for heat exchanger-type stainless steel during acid cleaning operation

Protecting heat exchanger alloys from corrosion during acid cleaning is sacrosanct and necessitates the development and application of highly–efficient environmentally–friendly corrosion inhibitors. In the present work, gravimetry, electrochemical impedance spectroscopy (EIS), cyclic potentiodynamic polarization (CPDP), cyclic voltammetry and scanning electron microscopy-energy dispersive x-ray spectrophotometry (SEM-EDX) have been employed to investigate the potential of 1–benzylimidazole and its mixture with potassium iodide (KI) for the mitigation of stainless steel (SS316L) corrosion in 1 M HCl solution at 60 °C. After short immersion time, 1–benzylimidazole is found to decrease the weight loss and corrosion rate of the substrate and impacts an inhibition efficiency of ≈ 65% at 2000 ppm dosage. The inhibitor adsorption followed the Freundlich isotherm. The synergism significantly lowers the rate of anodic half–reactions involving Fe and Cr oxidation which, in turn, boosts the inhibitor efficiency to > 80% through a competitive synergism. SEM-EDX characterization confirm that the passive layer formed in the presence of 1–benzylimidazole + KI significantly mitigated against the propagation of localized pitting corrosion. Prolonged immersion time, up to 72 h, lowers the inhibition efficiency of 1–benzylimidazole + KI mixture to 74 %.     

Mg0.9－xTi0.1PdxNi(x=0.04～0.1)贮氢合金电极腐蚀行为研究

研究了Pd部分替代Mg对Mg0.9－xTi0.1PdxNi(x=0.04～0.1)贮氢合金腐蚀性能的影响. 利用机械合金化方法制备了Mg0.9－xTi0.1PdxNi(x=0.04～0.1)贮氢合金. XRD和TEM分析表明经120 h球磨后该合金完全非晶化. 循环充放电测试结果表明, Pd的替代有效地延长了Mg0.9－xTi0.1PdxNi(x=0.04～0.1)合金的循环寿命. 采用开路电位测量, 阳极极化, 电化学阻抗和X射线光电子能谱研究了该合金的腐蚀行为. 结果表明, 随着Pd含量增加, 合金腐蚀电位正移, 初始腐蚀电流下降, 腐蚀电流增加的速度变缓. 采用本文提出的等效电路模型较好地拟合了合金的电化学阻抗谱. 分析表明, 随着Pd含量的增加, 合金表面钝化膜厚度和电阻逐渐增大. X射线光电子能谱分析表明, Pd的加入减弱了合金在充放电过程中的氧化程度. 当Pd含量达到0.1时, Mg0.9－xTi0.1PdxNi(x=0.04～0.1)合金的耐腐蚀性能最好, 其放电容量保持率最高.     

Preparation and electrochemical corrosion behavior of bulk nanocrystalline ingot iron in HCl acid solution

Bulk nanocrystalline ingot iron (BNII) was produced by the severe rolling technique. The corrosion behaviors of BNII and as-received conventional polycrystalline ingot iron (CPII) in 1 M HCl solution were investigated by potentiodynamic polarization tests, electrochemical impedance spectroscopy measurement, and immersion tests at room temperature. For BNII, the anodic dissolution process is inhibited, but the cathodic process is enhanced. The corrosion current and average corrosion rate of BNII are 0.479 and 0.391 those of CPII, respectively. The resistance of the charge transfer of BNII is about 1.59 times higher than that of CPII. These results indicate that the corrosion resistance of BNII is improved in comparison with CPII.     

电沉积Ni—Mo—P合金镀层在NaCl溶液中的腐蚀特性

用失重法，阳极率曲线，Ｘ－光电子能谱（ＸＰＳ）以及俄歇电子能谱（ＡＥＳ）研究了电沉积Ｎｉ－Ｍｏ－Ｐ合金镀层在５％ＮａＣｌ溶液中的腐蚀特性，非晶态Ｎｉ－Ｍｏ－Ｐ合金镀层比晶态Ｎｉ－Ｍｏ－Ｐ合金镀层有较低的腐蚀速度阳极极化曲线表明，Ｎｉ－Ｍｏ－Ｐ合金镀层中，镍的摩尔分数国０．７１９～０．８６８时，随镀层中磷含量的增加，腐蚀电位正移，而活化区的峰电流随镀层中钼含量的增加而增加，磷含量的活化区的峰电流以及