压铸镁合金阳极氧化膜的研究

研究了压铸镁合金AZ91的阳极氧化膜的工艺及其耐蚀性，探讨了镁合金表面阳极氧化膜的组织、相、成分及其耐蚀性。研究结果显示，压铸镁合金AZ91阳极氧化膜表面系氧化物的聚集，阳极氧化膜在3．5％NaCl中的极化曲线与AZ91压铸镁合金的极化曲线对比，阳极氧化膜的极化曲线有明显的钝化区，但在极化区只呈锯齿状变化，耐蚀性较好。     

Cementation and corrosion at a RDE: Changes in flow and transfer phenomena induced by surface roughness

Cementation and corrosion were investigated in a batch cell to highlight the improvement of the kinetics observed after a certain lapse of time. Experiments on cementation with the Cd(II)/Zn and Ag(I)/Cu systems, and on corrosion with the Ce(IV)/Zn and Cr(VI)/Zn couples, were carried out on a rotating disc electrode immersed in relatively concentrated solutions. Time variations of the concentration of the reacting species and SEM observations showed that the change in reaction kinetics was due to the roughness of the changing surface of the electrode, depending on the chemical system considered. For corrosion, the average roughness was shown to exceed the thickness of the Nernst diffusion layer, and the rougher surface created allows local flow disruption and mass transfer enhancement. Besides, corrosion by Cr(VI) species results in greater roughness of the metal surface with more significant flow disruption than with Ce(IV) at the same concentration.     

X70管线钢在CO2-3/HCO-3体系中表面膜性能研究

The electrochemical behavior of X70 pipeline steel in (0.5 mol· L-1 Na2CO3+1 mol· L-1 NaHCO3)solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze the composition and microstructure of the surface film. The results showed that there were two anodic peaks at -600 mV and -350 mV.The surface film formed at -600 mV mainly consisted of ferrous carbonates and ferrous hydroxycarbonates. It had a small reaction resistance. It was metastable and possessed poor protective property. Numerous pits and microcracks existed on the film, which could be the active paths for the initiation of stress corrosion cracking. The surface film formed at -350 mV, mainly consisted of ferric oxides. It has high reaction resistance and offered good protection for the substrate.     

The effect of potential bias on the formation of ionic liquid generated surface films on Mg alloys

An electrochemical approach to the formation of a protective surface film on Mg alloys immersed in the ionic liquid (IL), trihexyl(tetradecyl)phosphonium-bis 2,4,4-trimethylpentylphosphinate, was investigated in this work. Initially, cyclic voltammetry was used with the Mg alloy being cycled from OCP to more anodic potentials. EIS data indicate that, under these circumstances, an optimum level of protection was achieved at intermediate potentials (e.g., 0 or 0.25 V versus Ag/AgCl). In the second part of this paper, a small constant bias was applied to the Mg alloy immersed in the IL for extended periods using a novel cell design. This electrochemical cell allowed us to monitor in situ surface film formation on the metal surface as well as the subsequent corrosion behaviour of the metal in a corrosive medium. This apparatus was used to investigate the evolution of the surface film on an AZ31 magnesium alloy under a potential bias (between ±100 mV versus open circuit) applied for over 24 h, and the film evolution was monitored using electrochemical impedance spectroscopy (EIS). A film resistance was determined from the EIS data and it was shown that this increased substantially during the first few hours (independent of the bias potential used) with a subsequent decrease upon longer exposure of the surface to the IL. Preliminary characterization of the film formed on the Mg alloy surface using ToF-SIMS indicates that a multilayer surface exists with a phosphorous rich outer layer and a native oxide/hydroxide film underlying this. The corrosion performance of a treated AZ31 specimen when exposed to 0.1 M NaCl aqueous solution showed considerable improvement, consistent with electrochemical data.     

铝基超疏水表面的制备及其耐蚀性

对铝基进行恒电流阳极氧化后,采用正辛基三乙氧基硅烷化学改性,制得超疏水膜。采用接触角测试仪、扫描电镜、红外光谱仪、电化学工作站等,研究了所得超疏水膜的静态接触角、表面形貌、结构及耐蚀性。结果表明,经阳极氧化后,铝基构建了粗糙的微纳米结构,再硅烷化处理后,铝基表面的疏水性增强,静态接触角大于150°。超疏水膜使铝在质量分数为3.5%的NaCl溶液中的自腐蚀电位正移0.11V,腐蚀电流密度降低4个数量级,有效地提高了铝的耐蚀性。     

Incorporation of Cr in the passive film on Fe from chromate solutions

The uptake of Cr species from chromate solutions by Fe has been studied using X-ray absorption near edge structure (XANES). The objective of the investigation was to compare XANES with radioactive tracer techniques used by Brasher et al. Cr(III) was detected on the passive iron surface. The amount of Cr(III) was increased by cathodic polarization and decreased by anodic polarization. This demonstrated that the uptake of Cr(III) was the result of cathodic processes and was not a direct result of the growth of the passive oxide film. Cr(VI) was only found after Fe was exposed to a saturated dichromate solutions for extended periods indicating that Cr(VI) was not strongly absorbed on the passive film.     

Improvement of corrosion protection offered to galvanized steel by incorporation of lanthanide modified nanoclays in silane layer

Silane sol–gel based films are very promising alternatives to the traditional chromate pre-treatments. However, the protection offered by the silane films strongly decreases when the coating is damaged. Some previous studies showed that the barrier properties of the silane layer can be improved by incorporation of clay nanoparticles. Moreover, inhibitive metallic cations can be incorporated in the nanoclays by ion exchange, providing a way to prepare cheap corrosion inhibitors nanoreservoirs offering self-healing properties. Rare earth (RE) metal salts have been shown to be effective corrosion inhibitors on a wide range of metals, including hot dip galvanized (HDG) steel. For this study, montmorillonite clay is modified to obtain a Ce(III) montmorillonite clay (Ce-MMT). The amount of incorporated Ce(III) is characterized by means of XRF measurements. X-ray diffraction showed that the Ce(III) is located in the interlayer space.     

Effect of benzotriazole (BTA) addition on Polypyrrole film formation on copper and its corrosion protection

Benzotriazole (BTA) was added in a conducting Polypyrrole (PPy) film prepared on copper in oxalic acid aqueous solution containing pyrrole monomer to improve corrosion protection by the PPy film and reduce copper corrosion. When BTA was added in the preparation solution, the copper surface was covered by a BTA–Cu complex layer before the anodic polymerization of PPy was started. On the copper surface with the BTA layer, the initial dissolution of copper was inhibited and the PPy polymerization-deposition was started immediately after the anodic current was imposed. The PPy film thus formed was doped with oxalic ions and ionized BTA and was homogeneous in thickness and strongly adhesive. The PPy film containing BTA protected the copper from corrosion in 3.5 wt.% NaCl solution. In 400 h of immersion, copper dissolution was inhibited with 80% protection efficiency relative to that of bare copper.     

Corrosion resistance of aluminum oxide film and electrolytically coloured film in sodium chloride solution

The main interest of this study is to compare the corrosion resistance of aluminum anodic oxide film anodized in sulfuric acid bath with that of preanodized and electrolytically coloured film.Examinations have been carried out referring to (1) potentiostatted polarization curves shown on the specimens in 0.5 M sodium chloride solution, (2) impedance diagrams of the specimens and barrier thickness by Hunter's method and (3) optical metallographical observations of the aspects of pitting corrosion which took place on these specimens, and dipping test in corrosive solution.The results obtained are summarized as follows: (1) Typical difference was observed in regard to the potentiostatted polarization curves (i-t curves) between the two types of specimens in 0.5 M sodium chloride solution. The corrosion current caused by pitting corrosion of the electrolytically coloured specimens was smaller than that of anodized ones on the measurement by i-t curves. (2) The survey through the interfacial impedance diagrams of the specimens made clear that the impedance of the electrolytically coloured film was larger than that of uncoloured anodic oxide film, especially this greater increasing part of impedance was achieved in 15 s. This tendency was similar for the measurement of barrier thickness by Hunter's method. (3) The optical metallographical observations have demonstrated that there were far more advanced pitting corrosion on the anodic oxide film than on the electrolytically coloured film. In the dipping test, uncoloured anodized aluminum showed high extent of pitting corrosion, while electrolytically coloured aluminum performed well during colouring. So the total result of above examinations reveals that electrolytically coloured films are definitely more resistive to corrosion than anodic oxide films and this is due to the thick barrier layer of the former films.     

氨基乙酸对镁-锂合金阳极氧化膜的影响

在镁-锂合金阳极氧化中以氨基乙酸为添加剂制取氧化膜,并讨论氨基乙酸对氧化膜结构、形貌及性能的影响.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、无损涡流测厚仪、极化曲线(Tafel)和电化学交流阻抗谱(EIS)等分析了镁-锂合金基体和氧化膜的组成、表面形貌、厚度以及耐蚀性,并讨论其耐蚀机理.结果表明:阳极氧化膜主要由氧化镁、氢氧化镁和氢氧化锂构成;随着氨基乙酸的质量浓度的增加,阳极氧化膜趋于平整、致密,孔洞均匀;添加氨基乙酸形成的阳极氧化膜的自腐蚀电位正移,自腐蚀电流密度变小,当其质量浓度为6 g/L时,氧化膜耐蚀性最优,自腐蚀电流密度为1.12×10-7A/cm2;但当氨基乙酸的质量浓度过高时,氧化膜耐蚀性反而下降.电化学阻抗谱对氧化膜耐蚀性变化规律的分析与极化曲线结果相一致.     

The electrochemical synthesis of poly(aniline-co-o-anisidine) on copper and their corrosion performances

The copolymer films PANI-co-POA and poly(aniline-co-o-anisidine) were carried out on copper (Cu) electrode, by applying two different scan rates (20 and 50 mV s⁻¹) and using two different thicknesses at high scan rate. Synthesizes were achieved under cyclic voltammetric conditions from 0.075 M aniline and 0.075 M o-anisidine containing sodium oxalate solutions. The synthesized copolymer films were strongly adherent and homogeneous in both cases. AC impedance spectroscopy (EIS), anodic polarization plots and open circuit potential–time curves were used to evaluate the corrosion performance of copolymer coated and uncoated electrodes in 3.5% NaCl. It was shown that the copolymer film coated at low scan rate exhibited a better property initially when compared with the copolymer film produced at high scan rate. However, it could not resist the attack of corrosion products, in longer time and meanwhile its barrier property significantly diminished. It was found that the thin copolymer film produced at high scan rate by its catalysing effect led to the formation of highly protective copper oxides on the surface whereby providing a better protection for long exposure times. It also emerged that the corrosion resistances of thin copolymer film produced at high scan rate and copolymer film synthesized at low scan rate were almost same and relatively higher for much longer periods when compared with the one observed for bare copper electrode.     

Electrolytic oxidation of Ce(III) in nitric acid and sulfuric acid media using a flow type cell

The electrochemical oxidation behavior of Ce(III) in nitric acid and sulfuric acid media with various concentrations and compositions were investigated by cyclic voltammetry (CV) and potentiostatic electrolysis. In nitric acid media, the peak potential separation for the redox reactions of the Ce(III)/Ce(IV) couple shifted to base side with the increasing concentration of nitric acid from 1 to 6 M. The kinetics of the Ce(III)/Ce(IV) couple is rapid in high concentration nitric acid. The formal potential is independent of both proton and nitrate concentrations while the standard rate constant increases with added protons but is independent of nitrate concentration. Constant-potential electrolysis also shows that a high proton concentration is electrochemically favorable for the electron transfer of the Ce(III)/Ce(IV) couple and for a high Ce(IV) yield in nitric acid media. The current efficiency was ca. 75% for the oxidation process of Ce(III) at 298 K. A Ce(IV) yield of ca. 80% was achieved for the electrolysis of 100 mM Ce(III) in 6 M HNO₃ solution. In sulfuric acid media, the peak potential separation for the redox reactions of the Ce(III)/Ce(IV) couple shifted to noble side with rising concentration of sulfuric acid from 0.1 to 2 M and then shifted to base side with further increase in the concentration. A Ce(IV) yield of ca. 95% was achieved for the potentiostatic electrolysis of 100 mM Ce(III) in 3 M H₂SO₄ solution.     

汽车用铝合金阳极氧化及钵转化膜封闭技术

采用阳极氧化和钵转化膜封闭技术提高汽车用2036铝合金的耐蚀性。研究发现:铝合金阳极氧化膜由外部的多孔层和内部的阻挡层构成,多孔层孔径均匀,约为30 nm0经过阳极氧化处理后,铝合金的自腐蚀电位正移,自腐蚀电流密度下降,耐蚀性提高。经过钵转化膜封闭处理后,大量钵的氢氧化物覆盖阳极氧化膜表面,进一步提高了铝合金的耐蚀性。     

电压对7N01铝合金阳极氧化膜结构及耐蚀性的影响

采用160 g/L硫酸溶液在17°C下对7N01铝合金阳极氧化30 min,氧化电压分别选取14、15、16、17和18 V。用扫描电镜观察所得阳极氧化膜的形貌,用能谱仪和电化学测量分析了它的成分、厚度和耐蚀性。结果表明,7N01铝合金经过不同电压下的阳极氧化处理后,表面均能形成凹凸不平并有孔洞的阳极氧化膜,电压为17 V时所制膜层致密、均匀,厚度约为7.6μm,耐蚀性最佳,在3.5%NaCl溶液中浸泡1440 h后没有明显的腐蚀。     

6063铝合金在碱性含氧酸盐溶液中的高压阳极氧化

为比较在高压阳极氧化条件下不同电解液体系中碱性含氧酸盐对6063铝合阳极氧化膜层厚度及氧化时间的影响,将6063铝合金置于Na2SiO3、Na2HPO4和NaAlO2三种电解液体系中制备出阳极氧化膜。用涡流测厚仪测试了膜层厚度,通过点滴腐蚀实验评价了Na2SiO3体系所得氧化膜的耐腐蚀性能,利用扫描电子显微镜(SEM)观察分析了氧化膜的表面形貌。结果表明,钨酸钠能显著提高膜层厚度和膜层的耐腐蚀性能,六偏磷酸钠(SHMP)能延长氧化时间,提高膜层的硬度;在硅酸盐体系中钨酸钠和六偏磷酸钠按1∶1的比例加入,能得到致密的高耐蚀性阳极氧化膜层。     

汽车用铝合金阳极氧化及双重封闭工艺的研究

对汽车用2024铝合金进行了硫酸阳极氧化处理,并使用硫酸镍结合铬酸钾的双重封闭技术对阳极氧化膜进行了封闭处理。结果表明:在2024铝合金表面制备的阳极氧化膜属于典型的多孔膜。经过硫酸镍一次封闭处理后,大量镍的氢氧化物填充于膜孔内,有效地降低了阳极氧化膜的自腐蚀电流密度。经过铬酸钾二次封闭处理后,铬酸镍进一步覆盖在膜孔表面,大大提高了阳极氧化膜的均匀性和致密性。经过双重封闭处理后,阳极氧化膜的阻抗明显增大,耐蚀性大大提高。     

Ionic Liquids: How Far Do they Extend the Potential of Solvent Extraction of f-Elements?

Applicability of room temperature liquids (RTILs) as diluents in the solvent extraction of f-elements is reviewed. Characteristics of selected RTILs, important for such an application, are gathered. Properties tabulated are the melting and freezing points, density, mutual solubility with water, viscosity, surface tension, specific conductivity, and radiation stability. Properties such as environmental compatibility, toxicity, chemical and thermal stability, biodegradability, and chemical degradability imply that RTILs are not harmless to the environment or to work safety. The extraction efficiency and mechanism in systems involving RTILs is described, discussed, and compared with systems involving molecular diluents. Particularly assessed is the extraction of nitric acid by RTILs alone and TBP, the extraction of U(VI), Ce(IV), Pu(IV), Am(III), and lanthanides(III) by RTILs alone, the extraction of U(VI), Ce(IV), actinides(III,IV), and lanthanides(III) by solvating O-donors, the extraction of Eu(III) by a solvating N-donor, the extraction of lanthanides(III) and Am(III) by acidic extractants, and the extraction of actinides(III,IV) and lanthanides(III) by task specific ionic liquids.     

汽车用6061铝合金柠檬酸阳极氧化工艺的研究

对汽车用6061铝合金进行柠檬酸阳极氧化处理。研究发现:铝合金的阳极氧化过程伴随氧化膜的生成和溶解。适当升高氧化温度,有利于增加氧化膜的厚度和硬度。但氧化温度过高,会使得氧化膜的溶解速率加快。铝合金阳极氧化膜呈现典型的多孔结构。40℃下制备的氧化膜表面平整,具有优良的耐蚀性。当氧化温度高于40℃时,氧化膜表面的孔径增大,表面疏松,耐蚀性下降。     

紫铜海水管焊接部位在人工海水中的腐蚀行为

通过阳极极化曲线、交流阻抗测试、扫描电镜研究了紫铜海水管焊接部位在人工海水中的腐蚀行为.结果表明：紫铜、白铜焊缝和黄铜焊缝在人工海水中的阳极过程类似,相同电位下,白铜焊缝的电流密度最小,耐蚀性最佳,与阻抗测试结果一致.黄铜焊缝在电位-0.012 V时出现电流峰,腐蚀产物膜多孔、疏松,随后电极进入钝化区,钝化膜由Cu₂O、CuCl和ZnO组成;随电位升高,钝化膜溶解,发生铜锌置换反应,沉积的Cu导致活性电对的形成,增加了合金的腐蚀速度;当电位为＋0.87 V时,电极表面富集了针状锡和锡的氧化物.随后,电极表面积累的锡和锡的氧化物及腐蚀产物层对脱锌腐蚀有一定的阻碍作用,电流密度有所下降,最后腐蚀达到一种动态平衡,腐蚀机制为溶解-再沉积机理.     

硫酸镧对汽车用铝合金阳极氧化膜性能的影响

在汽车用2024铝合金阳极氧化使用的电解液中添加硫酸镧,并研究了硫酸锢的质量浓度对阳极氧化膜的厚度、膜重、硬度、表面形貌及耐蚀性的影响。结果表明:硫酸镧的催化作用有利于提高氧化速率,减小多孔层的孔径,从而提高阳极氧化膜的硬度及耐蚀性。当硫酸镧的质量浓度为0.8 g/L时,阳极氧化膜具有最高的硬度和最佳的耐蚀性。但当硫酸镧的质量浓度大于0.8 g/L时,稀土的吸附作用会使阳极氧化膜的性能有所降低。