乌洛托品对模拟汽车冷却液中镁合金的缓蚀作用

镁合金具有高比强度、比刚度以及良好的铸造性、切削性、抗冲击减震性、导热性、无毒性和可回收性等优点,被认为是汽车工业中极好的铝合金及有色金属替代品[1]。用镁合金制造汽车部件,特别是发动机等大重量部件,可以大大减轻车身重量,进而降低能源消耗和废气污染。但是由于镁合     

Corrosion behavior of magnesium and its alloy in NaCl solution

The electrochemical behavior of cast Mg, AZ91, and cast AZ91 in 0.1 M NaCl solution is investigated by measuring open-circuit potential (OCP), steady-state current-potential, and electrochemical impedance spectra (EIS). The similar electrochemical impedance behavior is found of three corrosion electrodes. There are two capacitances in high-and medium-frequency domains and one inductive loop or component in low-frequency domain. From equivalent circuit simulation, cast AZ91 has the worst corrosion resistance. The EIS results are in good agreement with those obtained by OCP and polarization curves. Based on the Cao theory, a simple corrosion mechanism is put forward, supplying a possible explanation for low-frequency inductive behavior for Mg and its alloy in NaCl solution at OCP. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 878–885. The text was submitted by the authors in English.     

镁合金化学转化膜的制备及其性能研究

在磷酸钠-磷酸二氢铵-高锰酸钾体系中对镁合金进行化学转化处理.研究了磷酸钠、磷酸二氢铵、高锰酸钾、温度、时间和添加剂对转化膜性能的影响.通过对转化膜结构、成分及性能的测试评价,得到了性能较好的化学转化溶液配方:Na3PO4为5g·L-1,NH4H2PO4为15 g· L-1,KMnO4为1g· L-1,添加剂(NH4)6 Mo7O24为0.5g·L-1.由SEM可观察到转化膜的表面成“干枯河床”状.XRD和EDS检测表明,膜层的主要成分是Mg,Al12 Mg17和无定形相,膜层表面主要有Mn,Mg,K,O和Al等元素组成.腐蚀实验和电化学测试表明,添加剂能够降低转化膜的腐蚀率,转化膜较基体的腐蚀电位正移了0.73 V,提高了镁合金的耐蚀性.     

Acceleration of the corrosion reaction of magnesium by Fenton reagents

Abstract

Magnesium alloys have attracted increased attention for a variety of applications, chief among which are alternative energy and medical implants. The use of biodegradable implants in the complex system of the human body, in which myriad reactions occur, must consider the potential effects of the body’s natural chemical reactions on implant corrosion rates. The aim of this study was to elucidate the synergistic effects of pure Mg and Mg alloys on the Mg corrosion reaction with reagents that participate in the Fenton reaction. We corroborated our results with six different measurement methods (hydrogen evolution rate [HER], gas chromatography [GC], potentiodynamic polarization, inductively coupled plasma [ICP] spectrometry, Auger electron spectroscopy [AES], and scanning electron microscope [SEM]). The results point out that the corrosion and hydrogen evaluation rates of Mg were elevated by the addition of Fenton reagents, divalent iron and hydrogen peroxide, to a saline solution. In the context of Mg-based alloy medical implant development and use, this observation is significant.     

Surface evaluation and electrochemical behavior of cerium conversion coating modified with silane on magnesium alloy

A new cerium conversion coating modified with the hydrolysis silane is designed for AZ31 magnesium alloy, which aims at assessing the surface characterizations and electrochemical behaviors between the cerium conversion coating with and without the silane modified. The effect of the silane addictive is studied by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The adhesion of the coatings is undertaken according to the American Society for Testing and Materials (ASTM) standard D3359‐08 cross tape test. The electrochemical behavior is evacuated by polarization experiment and electrochemical impedance spectroscopy (EIS) in NaCl electrolyte. The results show that the addition of bis‐[triethoxysilylpropyl] tetrasulfide (BTESPT) to loosen and porous cerium conversion coating leads to the formation of a more compact and homogenous film, higher resistance to water uptake and better adhesion to substrate. Electrochemical measurements show that, compared with the non‐modified cerium conversion coating, the coating modified with the silane exhibits better anticorrosion properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Corrosion behavior of AZ91D magnesium alloy in distilled water

The corrosion of AZ91D magnesium alloy has received extensive attention due to the continuous expansion of its application field in recent years. However, the corrosion of AZ91D magnesium alloy in distilled water is relatively few. In this paper, the corrosion behavior of AZ91D magnesium alloy was studied in distilled water by electrochemical tests in combination with weight loss and surface analysis methods. The results indicated that the corrosion rate of AZ91D magnesium alloy increased with the increase of temperature and immersion time. The increase of the corrosion rate of AZ91D magnesium alloy with the increase of immersion time might be attributed to the damage of the structure of corrosion product film by hydrogen evolution, significantly accelerating the anodic process of AZ91D magnesium alloy. It was interesting that, in distilled water, the EIS of AZ91D magnesium alloy excluded an inductive arc in the low frequency region, which indicated that there was no the adsorption and desorption of aggressive ions or the damage and repair of film. The corrosion product film of AZ91D magnesium alloy in distilled water was composed of a compact inner corrosion product film and a loose outer corrosion product film.     

Effect of surface finishing on the formation of nanostructure and corrosion behavior of Ni–Ti alloy

In the present work, we have investigated the formation of nanostructured oxide layers by anodic oxidation on different surface finished (mirror finished, 600 and 400 grit polished) nickel–titanium alloy (Ni–Ti) in electrolyte solution containing ethylene glycol and NH₄F_. The anodized surface has been characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X‐ray photoelectron spectroscopy (XPS). The corrosion behaviors of the Ni–Ti substrate and anodized samples have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in simulated body fluid (Hanks' solution). The results show that the native oxide on the substrate is replaced by nanostructures through anodization process. XPS of Ni–Ti substrate shows the presence of Ni⁰, NiO, Ti⁰ and TiO₂ species, whereas Ni₂O₃ and Ni(OH)₂ and TiO₂ are observed in the samples after anodization. Corrosion resistance of the anodized sample is comparable with that of the untreated sample. Copyright © 2016 John Wiley & Sons, Ltd.     

Auger electron spectroscopic analysis of corrosion products formed on A3003 aluminum alloy in model fresh water with different Zn2+ concentration

The corrosion morphology and composition of corrosion products of A3003 formed in model fresh water with different Zn²⁺ concentrations were investigated by immersion tests combined with surface observations and analysis using an Auger electron spectroscope (AES). The cross-sectional AES observations showed that the thickness of the corrosion product layer formed on A3003 decreases with increases in the Zn²⁺ concentration of the model fresh water. A cross-sectional AES point analysis suggested that the corrosion products formed on the A3003 in the Zn²⁺ containing model fresh water (Zn²⁺ > 0.1 mM) have a multilayered structure and that the inner of Zn-rich layer would have high corrosion protective properties.     

火焰原子吸收光谱法测定锌合金中镁

建立火焰原子吸收光谱法测定锌合金中镁含量。选用10 mL盐酸溶液(1+1)溶解样品,加入5 mL质量浓度为100 g/L的LaCl3溶液,以消除铝对镁的化学干扰,在选定的仪器工作条件下进行测定。结果表明,镁的质量浓度在0~1.238 mg/L范围内与与吸光度具有良好的线性关系,相关系数为0.999 4,线性方程为Y=1.086 4X+0.018 5,方法测定下限为0.010 mg/L。样品测定结果的相对标准偏差为1.61%~3.45%(n=6),加标回收率为91.3%~94.7%。该方法准确度高,精密度好,满足锌合金中镁含量的日常检测要求。     

Effect of TiO2–Ti and TiO2–TiN composite coatings on corrosion behavior of NiTi alloy

Two kinds of biocompatible coatings were produced in order to improve the corrosion resistance of nickel titanium (NiTi) alloy. A titanium oxide–titanium (TiO₂–Ti) composite was coated on NiTi alloy using electrophoretic method. After the coating process, the samples were heat‐treated at 1000 °C in two tube furnaces, the first one in argon atmosphere and the second one in nitrogen atmosphere at 1000 °C. The morphology and phase analysis of coatings were investigated using scanning electron microscopy and X‐ray diffraction analysis, respectively. The electrochemical behavior of the NiTi and coated samples was examined using polarization and electrochemical impedance spectroscopy tests. Electrochemical tests in simulated body fluid demonstrated a considerable increase in corrosion resistance of composite‐coated NiTi specimens compared to the non‐coated one. The heat‐treated composite coating sample in nitrogen atmosphere had a higher level of corrosion resistance compared to the heat‐treated sample in argon atmosphere, which is mainly due to having nitride phases. Copyright © 2014 John Wiley & Sons, Ltd.     

Monochromatized x‐ray photoelectron spectroscopy of the AM60 magnesium alloy surface after treatments in fluoride‐based Ti and Zr solutions

The behaviour of the 6% aluminium–magnesium alloy (AM60) surface in zirconium or titanium fluoride aqueous acid solutions was studied. X‐ray photoelectron spectroscopy was used to investigate modifications in the surface chemistry with respect to the composition of the surface treatment solution. The surface film is composed of magnesium hydroxide and hydroxyfluoride, zirconium oxide, oxyhydroxide or oxyfluoride, titanium oxide and structural and adsorbed water. Optimal parameters leading to the formation of a zirconium‐ or titanium‐rich film were determined. A mechanism is proposed for the formation of zirconium‐ or titanium‐based films. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of surface pretreatment on the corrosion behaviour of silanated AA2198-T851 Al-Cu-Li alloy

The corrosion behaviour of silanated AA2198-T851 alloy substrates with and with no manufacturing-process induced near-surface deformed layer (MPI-NSDL) has been investigated. Two methods (alkaline etching + desmutting and mechanical polishing) were employed in removing the MPI-NSDL. Silanization was performed using 2-bis-triethoxysilylethane. Electrochemical impedance spectroscopy (EIS), salt spray test, and microscopy techniques were employed in the investigation of the corrosion behaviours. The studies revealed that polishing appeared to be the best silanating pre-treatment (compared with degreasing and etching + desmutting) for the new generation AA2198-T851 Al-Cu-Li alloy, and this was reflected in the EIS spectra. The etched + desmutted and the degreased surface with MPI-NSDL did not respond well to silanization and presented more pitting sites per square millimeter. However, the severity of corrosion per pit was more on the polished sample compared with the other two. Also, the corrosion mechanisms were different for the three cases.     

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.     

六偏磷酸钠对AZ31镁合金电化学行为的影响

为提高AZ31镁合金阳极的活化性能以及抑制它的腐蚀,用电化学等方法研究了在中性3.5%Na Cl体系中,六偏磷酸钠(Na6(PO3)6)对AZ31镁合金电化学行为的影响。结果表明:Na6(PO3)6能大幅度抑制AZ31镁合金的腐蚀,但极化程度有所增大。当Na6(PO3)6的质量分数为2.0%时,AZ31镁合金的缓蚀率高达74.9%,腐蚀后其表面均匀,且活化性能有所改善,在-1.10V处时合金的电流密度高达0.033 m A.cm-2,开路电位Eocp负移程度最大(-1.59 V),活化电位Eact负移程度最大(-1.38 V)。试验结果为AZ31镁合金作为电极材料提供了参考。     

The local electrochemical behavior of the AA2098-T351 and surface preparation effects investigated by scanning electrochemical microscopy

In this work, scanning electrochemical microscopy (SECM) measurements were employed to characterize the electrochemical activities on polished and as-received surfaces of the 2098-T351 aluminum alloy (AA2098-T351). The effects of the near surface deformed layer (NSDL) and its removal by polishing on the electrochemical activities of the alloy surface were evaluated and compared by the use of different modes of SECM. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were also employed to characterize the morphology of the surfaces. The surface chemistry was analyzed by X-ray photoelectron spectroscopy (XPS). The surface generation/tip collection (SG/TC) and competition modes of the SECM were used to study hydrogen gas (H₂) evolution and oxygen reduction reactions, respectively. H₂ evolution and oxygen reduction were more pronounced on the polished surfaces. The feedback mode of SECM was adopted to characterize the electrochemical activity of the polished surface that was previously corroded by immersion in a chloride-containing solution, in order to investigate the influence of the products formed on the active/passive domains. The precorroded surface and as-received surfaces revealed lower electrochemical activities compared with the polished surface showing that either the NSDL or corrosion products largely decreased the local electrochemical activities at the AA2098-T351 surfaces.     

Surface analysis and corrosion resistance of new nickel base thin film alloys

Electroless Zn–Ni–P thin films were deposited on low carbon steel from an alkaline non‐cyanide aqueous electrolyte. The newly developed ternary alloys structure and microstructure investigations were carried out via X‐ray diffraction and SEM. Chemical composition of the coatings was investigated via energy dispersive spectroscopy. Polarization tests were used to study the corrosion properties of the coatings in a 3.5 wt.% NaCl solution. The results confirmed the high corrosion resistance of Zn–Ni–P alloy plated steel sheet. The surface analysis of the thin film samples before and after corrosion was performed by XPS. The incorporation of Zn in Ni–P thin film is proven for all initial samples to be as a mixture of zinc and zinc oxide, while nickel exists in +2 and +3 oxidized states. A passive film of a mixture of oxide and hydroxide of zinc and nickel forms on the surface and prevents the Zn–Ni–P thin films from corrosion. Copyright © 2014 John Wiley & Sons, Ltd.     

Corrosion behavior of tantalum alloying on γ‐TiAl by double‐glow plasma surface metallurgy technique

The Ta coating with corrosion resistance is grown on the γ‐TiAl substrate by double‐glow plasma surface metallurgy technique, followed by the electrochemical test in 10 wt%, 20 wt% HCl and 10 wt%, 40 wt% H₂SO₄ solution. The data of nanohardness and elastic modulus are collected by the nanoindention test. The adhesion strength of Ta coating is investigated by means of the scratch test. The study of corrosion resistance is performed using potentiodynamic polarization and electrochemical impedance spectroscopy and measured by SEM and X‐ray diffraction. Results highlight that the Ta coating is tightly bonded to the γ‐TiAl substrate, consisting of the deposition layer and diffusion layer. Experimental data indicate that the Ta coating presents excellent corrosion resistance, which is confirmed by the high values of polarization resistance (R_p) and the low values of corrosion current density (i_corr). The surface nanohardness of the Ta coating is improved from 3.41 to 7.29 GPa, nearly twice of that of the substrate. The Ta₂O₅ formed on the coating is able to hold back the penetration of adverse ions inwardly, owing to its dense structure and adhesion effect. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of surface treatments on the localized corrosion resistance of the AA2198-T8 aluminum lithium alloy welded by FSW process

In this work, the effect of eight types of surface treatments on the corrosion resistance of friction stir welded samples of an AA2198-T8 Al-Cu-Li alloy were tested and compared in an attempt to find suitable alternatives to toxic and carcinogenic hexavalent chromium treatments. All the samples were anodized and subjected to different post-anodizing treatments. The post-anodizing treatments were (1) hydrothermal treatment in Ce (NO₃)₃ 6H₂O solution; (2) hydrothermal treatment in Ce (NO₃)₃ 6H₂O solution with H₂O₂; (3) hydrothermal treatment in boiling water; (4) hexavalent chromium conversion coating; and (5) immersion in BTSE (bis-1,2-(triethoxysilyl) ethane. The corrosion resistance of the treated samples was evaluated by immersion tests in sodium chloride solution (0.1 mol L⁻¹ NaCl) and electrochemical impedance spectroscopy (EIS) of the friction stir weldment. The results showed that among the alternative treatments, the Ce-containing solutions presented the best corrosion resistance, especially when used without peroxide.     

Quantitative surface analysis of Fe?Ni alloy films by XPS,AES and SIMS

A comparison of quantitative surface analyses of Fe? Ni alloy thin films by various methods has been proposed as a pilot study by the Surface Analysis Working Group of the Consultative Committee for Amount of Substance (CCQM). To test the suitability of Fe? Ni for this purpose, alloy films with different compositions were grown on Si(100) wafers by ion‐beam sputter deposition and the compositions were certified by an isotope dilution method using inductively coupled plasma‐mass spectrometry. The alloy compositions measured with X‐ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) using sensitivity factors determined from pure Fe and Ni metal films agreed with the certified mean values to better than 2%. The alloy compositions quantified by secondary ion mass spectrometry (SIMS) with a C₆₀ ion source agreed to better than 4% with the certified compositions if one of the alloys was used to establish the relative sensitivity factors (RSFs). These results indicate that the quantification of the Fe? Ni alloy is a good method for a CCQM pilot study because matrix effects and ion‐sputtering effects are small for these analytical methods. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of anodizing conditions on the cell morphology of anodic films on AA2024-T3 alloy

The effects of applied current density, anodizing time, and electrolyte temperature on the cell and pore morphology of anodic films and the voltage-time response obtained during galvanostatic anodizing of AA2024-T3 alloy in sulphuric acid electrolytes have been studied. Scanning electron microscopy was employed to observe the film morphology. Sponge-like porous structure was promoted by anodizing at relatively low current density and high electrolyte temperature. In contrast, linear porous structure was favoured under the converse conditions. Intermediate conditions resulted in films containing either sequential layers of the 2 morphologies or a morphology incorporating features of the 2 types; such conditions were associated with anodizing voltages in the range 25 to 35 V. The reasons for the morphological differences are proposed to be due to interactions between film growth stresses and stresses arising from oxygen evolution on the development of the alumina cells.