Corrosion performances of a Nickel-free Fe-based bulk metallic glass in simulated body fluids

The corrosion performance of a Nickel-free Fe-based bulk metallic glass (BMG), Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ alloy, in Hank’s solution with pH value 7.4 and artificial saliva solution with pH value 6.3, was investigated by electrochemical techniques, aiming to assess the feasibility of Fe-based BMG as potential biomaterial. It was found that Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ BMG shows superior corrosion resistance in both simulated body fluids (SBF). The EIS analysis and cyclic polarization measurements indicated that the Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ BMG has larger polarization resistance value than that of 316L SS. The pitting corrosion potentials of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ BMG are much higher than that of the 316L SS, resulting in very few ions releasing into the SBFs while a significant amount of Ni and Fe ions release was found for 316L SS under the same condition.     

Influence of caffeine and temperature on corrosion-resistance of CoCrMo alloy

The inhibitory activity of caffeine (1,3,7-trimethyl xanthine) on artificial saliva was studied on a CoCrMo alloy using different electrochemical methods: open circuit potential (OCP), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The results show that caffeine produces an inhibitory effect on the anodic currents due to its adsorption on the surface of the alloy. Temperature is another parameter with an influence on corrosion processes, so thermodynamic data were obtained from Arrhenius plots and Langmuir adsorption isotherms. The protective action of caffeine is enhanced at high temperatures at OCP, while for potentiodynamic experiments high temperatures block the inhibitory activity of caffeine and the corrosion rate increases. The process may also be studied by a simulation, determining the functional dependence between OCP, corrosion current density (i _corr), corrosion potential (E _corr), breakdown potential (E _bd) and temperature and amount of caffeine in artificial saliva, for Heraenium® CE. The neural network-based methodology applied in this work provides accurate results, thus proving to be an efficient modelling technique.     

Investigation effect of benzotriazole on the corrosion of brass-MM55 alloy in artificial seawater by dynamic EIS

The electrochemical behavior of brass-MM55 alloy was studied in artificial seawater with benzotriazole by using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). This method gives possibility to investigate the protection of metals in corrosive medium by using inhibitors in galvanostatic conditions for a long time. Instantaneous impedance spectra for brass-MM55 were recorded for 10 h in artificial seawater for different concentration of benzotriazole. It was found that a few hours were not enough for the accurate calculation of corrosion inhibition. Also with this method it is possible to figure out how the charge transfer resistance (R _ct) changes by the time. Usefulness of the DEIS technique in the investigation of non-stationary phenomena has been proved in the field of inhibitor research. All studies clearly show that benzotriazole inhibits the corrosion of brass-MM55 alloy in artificial seawater solution and the value of inhibition efficiency increases with increasing concentration of benzotriazole.     

7075铝合金在电解液薄层下的电位波动

在3.5%NaCl电解液膜下,7075铝合金自腐蚀电位随浸泡时间的波动呈如下变化:浸泡初期,自腐蚀电位E波动的幅度极小,继续浸泡至4h后E急剧增大到20mV,而浸泡6h后的波动幅度与腐蚀初期相近,但出现了正向尖峰,至12h后的波动幅度又与4h的相当.实验发现自腐蚀电位的均方差随腐蚀时间呈先负移而后正移的趋势,4h时出现极小值.而电位功率谱密度线性部分的斜率(k),则在4h时呈现较小值,6h时出现最大值.由此推断7075铝合金在薄电解液膜下浸泡6h后其表面产生了稳定的蚀点.     

Study on corrosion resistance of electroplating zinc–nickel alloy coatings

Electrodeposited zinc–nickel alloy coatings have been widely adopted for surface treatment of automobile body steel sheet for high corrosion resistance. The corrosion behavior of the coatings has been related with the components of nickel, and the zinc–nickel alloy passive coatings have much higher corrosion resistance than that of zinc–nickel alloy coatings. In the present paper, the corrosion resistance behavior of the zinc–nickel alloy coatings obtained by new process and formulation has been studied by means of the electrochemistry test and neutral salt spray test. And it is discovered that the properties of corrosion resistance of zinc–nickel alloy passive coatings were better than that of zinc passive coatings, Cadmium passive coatings and alloys of electrodeposited cadmium–titanium. The components of corrosion productions, in terms of X‐ray diffraction (XRD), are mainly ZnO, ZnCl₂ · 4Zn(OH)₂ and small quantity of 2ZnCO₃· 3Zn(OH)₂. The component of zinc–nickel alloy coatings has been investigated with Glow Discharge Optical Emission Spectrometry (GDA‐750). And it is found that as the thickness of zinc–nickel alloy coatings increases, the component of zinc increases from beginning to end, but the peak value of nickel appears and an enrichment of nickel in the coatings comes into being. Because the electrodeposited zinc–nickel alloy coatings exhibit different alloy phases as a function of their alloy composition, in this paper, the crystal structure changing with the different component of nickel has been studied in terms of XRD. The result shows that electrodeposited zinc–nickel alloy has different phases: α‐phase, a solid solution of zinc in nickel with an equilibrium solubility of about more than 79% nickel; γ‐phase, an intermediate phase with a composition Ni₅Zn₂₁; η‐phase, a solid solution of nickel in zinc with less than 5% nickel; and δ‐phase (Ni₃Zn₂₂) appeared from η‐phase to α‐phase with increasing content of nickel. Copyright © 2009 John Wiley & Sons, Ltd.     

XPS and AES surface analysis of WC-Co-(Cr) cemented carbide after immersion in neutral solution

The binder phase Co in WC-Co cemented carbide is dissolved easily in corrosive media (even in neutral solution), which has limited its application in a wider range. In this paper, the influence of Cr on corrosion resistance of WC-Co immersed in neutral solution was studied, with a focus on the surface chemistry of the corrosion product. The results show that in neutral solution, the corrosion is mainly caused by the selective dissolution of Co and the dominant surface corrosion product after immersion is Co (OH)₂. The corrosion resistance of WC-Co cemented carbide can be improved by the addition of Cr. This can be explained by the formation of more protective chromium containing oxide on the binder phase of WC-Co-Cr alloy, leading to reduced corrosion rate.     

Corrosion of Al85Ni9Ce6 amorphous alloy in the first hours of immersion in 3.5-wt% NaCl solution: The role of surface chemistry

AbstractThe surface chemistry and corrosion behavior of Al₈₅Ni₉Ce₆ melt-spun ribbons were studied after the first hours of immersion in 3.5-wt% NaCl solution at room temperature. X-ray photoelectron spectroscopy (XPS) was used to assess the chemical states of Al, Ce, Ni, and O. Electrochemical impedance spectroscopy was used to assess the corrosion resistance of the Al₈₅Ni₉Ce₆ ribbons. The alloy remained immersed for up to 48 hours. The results showed that hydroxide species in the passive film play a central role in the corrosion behavior of the Al₈₅Ni₉Ce₆ alloy.     

Effect of nano-Al2O3 particles and of the Co concentration on the corrosion behavior of electrodeposited Ni–Co alloys

Incorporation of nano-Al₂O₃ particles into a Ni–Co alloy by electrodeposition influences the corrosion properties, morphology, and structure of the layers. The resistance against corrosion of Ni–Co/Al₂O₃ composite films deposited on stainless steel was investigated in a 0.1-M NaCl solution by potentiodynamic polarization. The presence of nanoparticles improves the corrosion resistance of Ni–Co/nano-Al₂O₃ deposits when compared to pure Ni–Co alloy. Moreover, by increasing the pH of the electrodeposition bath and the content of Co in the alloy, the resistance against corrosion is furthermore improved. The morphology of the deposits before and after their corrosion was analyzed by scanning electron microscopy. The presence of the embedded alumina particles in the Ni–Co alloys was one of the key factors that limited further propagation of corrosion on the metallic surface. Preferential corrosion attack, in the form of a pitting corrosion, was located mainly at the grain boundaries.     

The effect of chloride concentration and pH on pitting corrosion of AA7075 aluminum alloy coated with phenyltrimethoxysilane

The effect of chloride ion concentration and pH of solution on the corrosion behavior of aluminum alloy AA7075 coated with phenyltrimethoxysilane (PTMS) immersed in aqueous solutions of NaCl is reported. Potentiodynamic polarization, linear polarization, open circuit potential, and weight loss measurements were performed. The surface of samples was examined using SEM and optical microscopy. Elemental characterization of the coating by secondary ion mass spectrometry indicates an intermediate layer between coating and aluminum alloy surface. The corrosion behavior of the aluminum alloy AA7075 depends on chloride concentration and pH of solution. In acidic or neutral solutions, general and pitting corrosion occur simultaneously. On the contrary, exposure to alkaline solutions results in general corrosion only. Results further reveal that aluminum alloy AA7075 is susceptible to pitting corrosion in all chloride solutions with concentrations between 0.05 M and 2 M NaCl; an increase in the chloride concentration slightly shifted both the pitting and corrosion potentials to more active values. Linear polarization resistance measurements show a substantially improved corrosion resistance value in case of samples coated with PTMS as compared to uncoated samples in both neutral (pH = 7), acidic (pH = 0.85 and 3), and alkaline chloride solutions (pH = 10 and 12.85). The higher corrosion resistance of the aluminum alloy coated with PTMS can be attributed to the hydrophobic coating which acts as a barrier and prevents chloride ion penetration and subsequent reaction with the aluminum alloy.     

Electrochemical Behavior of Dental Ni‐Cr Wirolloy Coated with Eco‐friendly Films in Artificial Saliva

The electrochemical corrosion behavior of the non‐precious Ni‐Cr Wirolloy, being used in dentistry, was investigated before and after applying of two types of eco‐friendly coatings, polyvinyl silsesquioxane (PVS) and nano‐hydroxyapatite (nHAP) separately in artificial saliva solution at 37 °C for 14 d of immersion. The study aimed to investigate the effectiveness of the introduced coating films in enhancing the corrosion resistance of the alloy, and in decreasing the leaching of the toxic Ni ions from the alloy into the environment. The electrochemical corrosion investigation methods used are; open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The evaluated results revealed that the electrochemically coated alloy with PVS. prepared at cathodic potential showed higher corrosion resistance and more stable film compared to that prepared by conventional dip‐coating method. At the same time, the nHAP electrochemically coated film provided the best anti‐corrosion properties over all examined time intervals. The obtained results were confirmed via surface analysis, which assured the formation of the prepared coatings on the alloy surface. Chemical analysis of the corrosion product/solutions showed that the effect of electrochemically deposited nHAP and PVS. polymer films in suppression of Ni ions leaching is similar and slightly higher than that of the chemically coated PVS. one; however, all of them are efficient in decreasing the leaching of the risky Ni ions into the solution.     

Al合金铈盐转化膜缓蚀机理研究

Ce盐作为一种环境友好的Al合金缓蚀剂日益受到重视 ,但缓蚀机理还不很清楚 .本文应用自行研制的扫描微参比电极技术 (SMRE) ,原位测量经CeCl3处理和未处理过的 2 0 2 4 T3Al合金表面微区电位分布 ,并用扫描电子显微镜 (SEM )和X 射线能量散射谱 (EDS)表征样品形貌特征 ,结合其它电化学技术 ,对Ce盐缓蚀机理作了深入探讨 .结果表明 ,经Ce盐处理的Al合金表面可形成一层不均匀分布的转化膜 ,抑制了O2 和电子传输 ,表现为一种优良的阴极缓蚀特性     

Electrodeposition and characterization of Zn–Sn alloy coatings from a deep eutectic solvent based on choline chloride for corrosion protection

With the aim of obtaining high corrosion resistant Zn–Sn alloy coatings from an ionic liquid, the effects of electrodeposition potential and electrolyte composition on the electrodeposition behavior, film composition, morphology and corrosion performance were investigated. Cyclic voltammograms indicate that Zn and Sn were co‐deposited at distinct reduction potentials as pure Zn and Sn elements. In addition, the phase composition analysis also showed that the obtained Zn–Sn alloy deposits (8 wt.%–45 wt.% Zn) consist of a two‐phase mechanical mixture of small aggregates of Zn and Sn metals. The Zn content of the alloy significantly increases as the electrodeposition potential and electrolyte Zn (II)/Sn (II) ratio increase. The corrosion performance study of the obtained Zn–Sn coatings showed that they have a passivation behavior and their corrosion resistance increases as the alloy‐Sn content increases. To improve their morphological properties, ethylene diamine tetraacetic acid additive was introduced into the electrolyte and greatly improved the morphology and corrosion resistance of the deposits. For the first time, it was shown that high corrosion resistance Zn–Sn coatings can be obtained from ionic liquids. Copyright © 2014 John Wiley & Sons, Ltd.     

Corrosion evolution of UNS C90300 bronze in simulated acid rain of Hong Kong

Corrosion evolutions of UNS C90300 bronzes with and without artificial patina were investigated in the simulated acid rain of Hong Kong. The corrosion products mainly composed of cuprite were formed on the surface exhibiting slight protection for the bronze substrate. The ratios of Sn and Zn in the corrosion products are lower than in the alloy. The artificial patina effectively enhances the corrosion resistance of bronze substrate, even after 30 days of immersion. For both bare and patinated bronzes the Sn- and Zn-based species are absent in the outer layers of corrosion products, and Cu₂O species in the outer layer can partially transform into Cu (II) ionic state due to the abundant supply of dissolved oxygen.     

Electrodeposition of Zn–Ni alloys from sulfate bath

The electrodeposition of zinc–nickel (Zn–Ni) alloys from sulfate baths has been studied at different deposition times and H₂SO₄ and NiSO₄ concentrations; various characteristics have been observed during alloy deposition and dissolution. The deposit has been investigated by using scanning electron microscopy (SEM) and X-ray diffractometry. Cyclic voltammetry and galvanostatic measurements during electrodeposition have been conducted. Electrochemical and surface analysis indicate that deposition takes place with the formation of two different structures corresponding to γ-phase and δ-phase zinc–nickel alloys. During anodic part of the cyclic voltammetry of the alloys, a reduction process has been observed, which may be due to hydrogen evolution. With the increase of nickel concentration in the bath, the amount of γ-phase increases, as indicated by the relative increase in the height of the peaks in the X-ray patterns and anodic peaks in the cyclic voltammograms. Also, the corrosion resistance of the zinc–nickel alloy has been improved with an increased concentration of nickel. Under these experimental conditions the electrodeposition of the alloys is of anomalous type.     

Influence of acidic ionic liquids as an electrolyte additive on the electrochemical and corrosion behaviors of lead-acid battery

The aim of this study is to introduce the application of some acidic ionic liquids (ILs) as an electrolyte additive in lead-acid batteries. A family of alkylammonium hydrogen sulfate ILs, which are different in the number of alkyl chain, is investigated with the aim to compare their effects on the electrochemical behavior of Pb–Sb–Sn alloy in sulfuric acid solution. The hydrogen and oxygen gas evolution potential and anodic layer characteristics were investigated employing cyclic and linear sweep voltammetric methods. The morphological changes of the PbSO₄ layer that formed on the electrode surface were confirmed using scanning electron microscopy. Also, potentiodynamic polarization curves, electrochemical impedance spectroscopy, and an equivalent circuit analysis were used to evaluate the corrosion behaviors of the Pb–Sb–Sn alloy in the presence of ILs. The obtained results indicate that hydrogen and oxygen evolution overpotential of lead–antimony–tin alloy increases in the solution containing IL and mainly depends on the number of alkyl chain in alkylammonium cation. It is clearly observed that the morphology of PbSO₄ layer changes under the influence of ILs. The corrosion studies show an increase in corrosion resistance of lead alloy in the presence of some ILs. Also, the electrochemical effects of ILs in conversion of PbSO₄ to PbO₂ and vice versa were investigated by carbon-PbO paste electrode. Cyclic voltammogram of carbon-PbO electrode shows that in the presence of ILs, oxidation and reduction peak currents increase, while reversibility decreases.     

Assessment of corrosion resistance of surface-coated galvanized steel by analysis of the AC impedance spectra measured on the salt-spray-tested specimen

In the present work, corrosion resistance of surface-coated galvanized steel was quantitatively determined by an analysis of the alternating current (AC) impedance spectra measured on the salt-spray-tested specimen. To evaluate the corrosion resistance of the surface-coated galvanized steel, AC impedance spectroscopy was performed on the salt-spray-tested specimen previously exposed to salt-sprayed corrosive environment. From the analysis of the impedance spectra, the area fraction transient of white rust θ ₂(t) was theoretically derived from the equivalent circuit equation by using two fitting parameters. The values of the two fitting parameters were determined by fitting the empirical transient equations to the area fraction of the resin coating layer and to the total resistance obtained from the impedance spectra measured, respectively. From the analyses of θ ₂(t) for four kinds of surface-coated galvanized steels with various resin coating layers, it is indicated that as the values of the two fitting parameters decrease in the order of CP, GI, OD and OM (commercial trade names) specimens, the corrosion resistance increases in that order as well. Furthermore, from the quantitative comparison of the two fitting parameters with the polarization resistance of the upper resin coating layer R _p determined from the potentiodynamic polarization curve, it is suggested that the two fitting parameters decrease in value as well with increasing R _p.     

Synthesis and characterization of sol–gel derived glass-ceramic and its corrosion protection on 316L SS

Glass-ceramic was prepared by sol–gel method using Ca(NO₃)₂·4H₂O and P₂O₅ as Ca and P precursors, respectively. In order to improve the bioactivity of the implant material, glass-ceramic (β-Ca₂P₂O₇) coating was developed on 316L SS substrate by spin coating method. Coating was annealed at different temperatures and its corrosion resistance was evaluated by electrochemical polarization and impedance analysis using Ringer’s solution as electrolyte. The results from the present study, show excellent corrosion resistance for coated 316L SS, corroborated by the high values of charge transfer resistance from impedance analysis and higher breakdown and repassivation potential with the corresponding lower current density from polarization measurements. Based on the results, the glass-ceramic coating on 316L SS can be considered as a corrosion resistant material.     

Effectiveness of 2‐mercaptobenzothiazole, 8‐hydroxyquinoline and benzotriazole as corrosion inhibitors on AA 2024‐T3 assessed by electrochemical methods

In this study, the effectiveness of 2‐mercaptobenzothiazole (2‐MBT), 8‐hydroxyquinoline and benzotriazole as corrosion inhibitors for AA 2024‐T3 aluminium alloy was evaluated. The corrosion behaviour in the presence of each compound was investigated by image‐assisted electrochemical noise analysis, electrochemical impedance spectroscopy, potentiodynamic polarization and the split cell technique. It was found that 2‐MBT has superior inhibition properties compared with the other inhibitors. In particular, the specimens immersed in 3.5% NaCl in the presence of 2‐MBT displayed high values of noise resistance that were maintained for over 400 h of testing, and high values of low‐frequency impedance, measured after immersion for 24 h. The split cell technique and potentiodynamic polarization tests indicated that only 2‐MBT decreases significantly both the anodic and the cathodic reaction rates. Scanning electron microscopy observations and energy dispersive X‐ray measurements complement the findings from electrochemical measurements indicating that only 2‐MBT protects the second phase particles, preventing dealloying, trenching and initiation of corrosion. © 2015 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd.     

Electrodeposition of Al-Ti alloy on mild steel from AlCl<Subscript>3</Subscript>-BMIC ionic liquid

The electrodeposition of Al-Ti alloy on a mild steel substrate is examined in a Lewis acidic 66.7–33.3 mol% AlCl₃-1-buthyl-3-methylimidazolium chloride ionic liquid containing TiCl₄. Dense and compact Al-Ti alloy coatings with Ti content ranging from 5.3 to 11.4 at.% can be obtained under optimized conditions. The applied current densities and TiCl₄ concentration are found to play central roles in controlling the alloy compositions and surface morphologies of the resultant Al-Ti alloy coatings. Ti content in Al-Ti alloys increases with initial increase in the current density and decreases when the current density is beyond 5 mA cm^?2. In addition, the enhanced corrosion resistance of the mild steel substrate by the deposited Al-Ti alloy layers is evaluated via electrochemical techniques. The Al-Ti alloy coatings show much higher corrosion resistance than single Al coating, and this performance is improved with the increase of the Ti content.     

饱和NaCl溶液浸泡下混凝土试块中有机阻锈剂对钢筋腐蚀行为的影响

利用电化学阻抗谱(EIS)、半电池腐蚀电位(Ecorr)和宏观电池腐蚀电流密度(Icorr)测量技术,在饱和NaCl溶液浸泡的硬化混凝土试块中,研究了4种醇胺基阻锈剂对钢筋电极腐蚀电化学行为的影响和长期阻锈性能.在浸泡初始的100d内,与空白样相比,添加阻锈剂后钢筋电极腐蚀电位升高,阻抗膜值增大,腐蚀电流密度值降低,表明电极表面处于钝态,阻锈剂表现出良好的阻锈性能.随浸泡时间延长,电极腐蚀电位和阻抗膜值下降,腐蚀电流密度增大.浸泡后期,除添加醇胺基CI-4样外,电极电位和腐蚀电流密度与空白样相比无明显差别,表明电极由钝态转变为活性腐蚀状态.但添加CI-4样品,钢筋电极始终保持在钝化状态,阻锈性能最好.基于阻锈剂与Cl-间的竞争吸附,分析探讨了可能的阻锈机理.