电解质对镁合金阳极氧化膜性能影响的研究进展

综述了电解质对氧化膜性能影响,为设计、选用阳极氧化工艺提供参考.随着人类环保意识的增强,未来镁合金阳极氧化电解质研究重点在于开发更多、对环境和人类友好且能较大提高氧化膜耐蚀性的物质.     

镁合金阳极氧化的研究进展与展望

回顾镁合金阳极氧化历史，介绍制备工艺、电解液组成及作用，同时对镁合金阳极氧化机理进行探讨。随着人类环保意识的增强，世界能源的紧缺和氧化设备的不断更新，认为电参数如频率、占空比、电压和电流密度对氧化膜性能的影响、阳极氧化电流效率的测定、氧化膜扩散规律的研究和环保型电解液的开发为未来镁合金阳极氧化研究的重点。     

热处理对铝箔阳极氧化膜结构与电化学特征的影响

将高压铝电解电容器用腐蚀铝箔在硼酸电解质溶液中进行530 V阳极氧化,应用透射电镜、X射线衍射与交流阻抗对比研究了阳极氧化对铝箔实施500℃×2 min热处理前后对表面高压阳极氧化膜的微观结构与电化学特征的影响。结果表明：高压阳极氧化膜具有明显的层状结构特征,外层晶化程度较低、晶粒细小;内层晶化程度较高、晶粒较为粗大;热处理后可以显著提高氧化膜各层的结晶程度、单位厚度阳极氧化膜耐电场强度增加,减弱了对铝箔表面隧道微孔的堵塞程度,氧化膜表观比电容相应增大,热处理及其随后的修补化成提高了阳极氧化膜的致密程度,氧化膜表观比电阻也相应增加。     

壁垒型铝阳极氧化膜的成份及电解质离子在膜中的漂移

讨论了俄歇能谱仪分析壁垒型铝阳极氧化膜成份的一些技术问题。配合氩离子溅射深度成份分析、离子注入标记氙原子、膜剖面超薄切片的透射电子显微镜观察,证实了壁垒型阳极氧化膜一般由内、外两层组成。外层是向膜外迁移的铝离子在膜与电解质溶液的界面上形成的;内层则是向膜内迁移的含氧离子在膜与基体界面上形成的。电解质溶液的离子会结合在膜中,并在电场影响下发生漂移。测出了存选定的实验条件下,膜中电解质离子的平均漂移速度。     

铝及铝合金阳极氧化分类及主要用途

<正>金属表面阳极氧化是指金属在电解质溶液中,被处理的零件作为阳极,耐腐蚀性导电材料作为阴极,通过电化学的处理方法,在金属表面生成具有耐磨性、耐腐蚀性及其他功能或装饰性的转化膜层的工艺过程。阳极氧化的处理对象主要是有色轻金属材料,特别是铝及铝合金、镁合金、钛及钛合金。阳极氧化处理所得到的膜层无论是致密度、硬度、耐磨性、耐腐蚀性及其他的性能,都比化学氧化所得到的转化膜好,膜层也更厚、更牢固。     

SiCp/2024 Al复合材料阳极氧化膜的结构和耐蚀性

用动电位阳极极化和点滴法评估了17％SiCp／2024Al复合材料(MMC)硫酸阳极氧化膜的耐蚀性，用光学显徽镜、SEM和TEM对氧化膜的形貌和结构进行了观察，用EDXS分析了膜的组成，极化实验结果表明，复合材料的阳极氯化膜具有良好的耐NaCl溶液腐蚀的能力，其腐蚀速度较未处理的基体降低了2个数量级以上。SEM形貌表明，SiC颗粒对膜的生长有阻碍作用，低电流密度下形成的阳极氧化膜膜层较薄，结构致密，孔隙细小，腐蚀实验结果表明该膜层具有更高的耐蚀性，TEM显示，MMC阳极氧化膜的孔隙分布严重不均，在SiC颗粒周围的基体中，孔隙密度较大，孔隙间距较小，孔径也较大，最大可达50nm，这表明阳极氧化膜具有低抗蚀性的结构特征，EDXS分析表明SiC颗粒在阳极氧化过程中会被氧化。     

铝及铝合金的阳极氧化研究综述

较为系统地介绍了铝及其铝合金的阳极气体工艺技术，对传统的阳极氧化方法进行了总结，探讨了铝阳极氧化多孔膜的性能及微观结构，以及作为功能材料铝阳极氧化膜广泛的应用，对铝阳极氧化技术最近所取得的应用上的进展进行了总结。     

腐蚀铝箔高压阳极氧化膜微观结构与电化学特征

将高压铝电解电容器用腐蚀铝箔在硼酸电解质溶液中进行530 V阳极氧化,应用透射电镜与交流阻抗研究了所形成的高压阳极氧化膜的微观结构与电化学特征。结果表明:高压阳极氧化膜具有明显的层状结构特征,各层的结晶程度与缺陷特征不同,外层晶化程度较低、缺陷较少;中层与内层晶化程度较高、缺陷较多;铝箔表面微孔诱发弥散效应,交流阻抗频谱的等效电路可用膜QOX与膜电阻ROX并联,再与电解液电阻RS串联来表征,容抗行为显著接近界面电容元件特性,膜电阻处于氧化膜非晶质层电阻与结晶质层电阻之间而偏向结晶质层电阻。     

Fe-40Cr-2Ce合金阳极900℃氧化及电解腐蚀行为

采用真空感应熔炼法制备铝电解用Fe-40Cr-2Ce合金阳极。研究了合金阳极900℃下的氧化和电解腐蚀行为。电解测试采用900℃的NaF-AlF3低温电解质体系,阳极电流密度为0.5 A/cm2,电解时间10 h。结果表明：合金的氧化动力学曲线遵循抛物线规律;合金中高浓度的Ce形成晶界沉淀,造成Ce的＂活性元素效应＂失效。电解后的阳极表面生成连续的FeCr2O4尖晶石相氧化膜。根据热腐蚀酸-碱溶解机理,氧化物在氧化物/电解质界面上的溶解度负梯度造成了阳极表面氧化物的持续的溶解。电解质中高浓度的氧化铝有利于减缓氧化膜的酸性溶解,降低合金阳极的电解腐蚀速率。     

镁合金的阳极氧化研究

阳极氧化是镁合金表面改性的有效方法.基于经典的阳极氧化工艺,目前的研究取得了长足的进步,主要表现在电解质溶液成分的改进、电参数的研究、成膜机理、膜层成分和结构的研究,以及后处理等.本文对其进行了详细的综述,同时指出了发展趋向.     

电解液组成对镁合金阳极氧化膜性能的影响

阳极氧化处理是提高镁合金耐腐蚀性能的有效方法。在阳极氧化工艺中,电解液组成对镁合金氧化膜的性能有着至关重要的影响。本文概述了近年来该领域内有关电解液组成的研究进展,期望为镁合金阳极氧化工艺研究提供参考。     

“Stopping off” Materials for Use in the Electro-Deposition of Nickel

The results are presented of a quantitative study of the phosphoric acid anodizing of high purity aluminium. The effects of electrolyte concentration, temperature, anodizing time, current density and air agitation on the coating weight, metal loss, coating ratio and density of the anodic coating were investigated.

The use of phosphoric acid anodic coatings as a base for electrodeposition is discussed with particular reference to plating in a copper pyrophosphate solution and the growth of copper deposits in the anodic film. Tests on chromium/nickel/copper electrodeposits on 38 aluminium alloy are briefly described.     

纯镁和AZ91HP镁合金微弧氧化膜性能比较

在环保型电解液中,采用电压-时间曲线、等离子体发射光谱仪(ICP)、扫描电镜(SEM)等方法研究了纯镁和AZ91HP两种基体材料对氧化过程、氧化膜表面形貌及成分的影响.根据电压-时间曲线,在氧化时间分别为1 min和5 min时,AZ91HP镁合金的电流效率比纯镁低,可能是由AZ91HP中的合金元素铝氧化并进入氧化膜中导致裂缝增加,成为析氧中心所导致的.在AZ91HP镁合金上生成的氧化膜孔的均匀性没有纯镁好,并且最大孔的直径比在纯镁上的氧化膜大.EDS分析表明,随着氧化时间延长,氧化膜中Si和P含量增加;而在氧化时间相同的情况下,两种基体上形成的氧化膜成分没有明显区别.ICP方法没有检测到氧化溶液中含有Mg~(2+)和Al~(3+),表明这两种离子在溶液中的浓度很低.     

Microplasma electrochemical deposition of aluminum oxide-polyethylene composite coatings on iron surface

Composite coatings containing aluminum oxide and polyethylene are deposited using microplasma electrochemical anodic treatment of the iron surface in an aluminate bath at a voltage of 260–360 V. Using scanning electron microscopy, microprobe analysis, Fourier transform infrared spectroscopy, and electrochemical polarization measurements, the composition, structure, and corrosion characteristics of the coatings are determined. Adding 0.5–1.0 wt % polyethylene dispersion to the electrolyte is shown to substantially facilitate the origination of microplasma conditions, prevent the strong warming of electrolyte during anodizing, and obtain coatings with substantially higher corrosion resistance compared to those produced in an aluminate bath containing no polymer dispersion.     

添加剂对铝合金常温硬质阳极氧化的影响

传统的铝硬质阳极氧化工艺需要较低的温度和较高的电压,能耗大且工件易烧损。本工作通过在阳极氧化电解液中添加草酸、丙三醇及NiSO4,提高阳极氧化温度上限实现了常温下的硬质氧化,并采用正交试验法对添加剂含量进行优化,获得了最佳的常温硬质阳极氧化工艺。     

Preparation of anodic films on 2024 aluminum alloy in boric acid-containing mixed electrolyte

The anodizing oxidation process on 2024 aluminum alloy was researched in the mixed electrolyte with the composition of 30 g/L boric acid, 2 g/L sulfosalicylic acid and 8 g/L phosphate. The results reveal that the pre-treatment and the composition of the mixed electrolyte have influence on the properties of the films and the anodizing oxidation process. Under the condition of controlled potential, the anodizing oxidation current-time response curve displays “saddle” shape. First, the current density reaches a peak value of 8-20 A/dm^2 and then decreases rapidly, finally maintains at 1-2 A/dm^2. The film prepared in the mixed electrolyte is of porous-type with 20 nm in pore size and 500 μm^-2 in porosity. Compared with the conventional anodic film obtained in sulfuric acid, the pore wall of the porous layer prepared in this work is not continuous, which seems to be deposited by small spherical grains. This porous structure of the anodic film may result from the characteristics of the mixed electrolyte and the special anodizing oxidation process. The surface analysis displays that the anodic film is amorphous and composed of O, Al, C, P, S, Si and no copper element is detected.     

Characterization of passive films on tin through transient electrochemical techniques

Voltammetry and chronoamperometry were employed to derive mechanistic information about the electroreduction of anodic films on tin. This information proved useful to gain a deeper insight into the complex passivation process as well as into the passive layer changes generated by the anodizing procedure. Tin electrodes were anodized in carbonate-bicarbonate buffers covering a wide range of pH and electrolyte composition. Two cathodic peaks were detected in the voltammetric response and they were correlated with two maxima present in electroreduction current transients. The second electroreduction process corresponds to a surface species generated during the anodic potential bias at the beginning of the secondary passivity range. This process has distinct features and is dependent on anodizing time, solution agitation and ionic strength of the electrolyte.     

Plasma electrolytic oxidation of pre-anodized aluminium

The influence of an anodizing pre-treatment in sulphuric acid is investigated on plasma electrolytic oxidation (PEO) of aluminium in silicate electrolyte under constant rms current. The presence of the anodic film is shown to promote the establishment of a micro-arc regime that is favourable for growth of the PEO coating. The incorporation of the pre-formed film into the coating appears to proceed by thermal transformation of the anodic alumina, accompanied by formation of oxide beneath the pre-formed layer. The final coatings contain α- and γ-Al₂O₃, with increased concentrations of silicon, sodium and potassium in an outer region of the coating.     

Modelling of the porous anodizing of aluminium: Generation of experimental input data and optimization of the considered model

The current paper considers the interdependency between the current density, the anodic overpotential and the temperature during the porous anodizing of aluminium in a sulphuric acid electrolyte. In contrast to common anodizing experiments, a sequence of increasing current densities is applied to each electrode. As demonstrated, this anodizing approach allows evaluating stationary anodic potentials up to very high current densities without being confronted with anomalous oxide growth. Additionally, anodizing is performed at controlled electrolyte and electrode temperature. Due to its large influence on the electrochemical behaviour, the control of the electrode temperature is important when studying the temperature dependency of the process. Based on the experimental evolutions a macroscopic model is presented, describing the relation between the considered general process parameters. It is demonstrated that a relatively simple expression is capable of well describing the experimental data in the extensive range of temperatures and current densities.     

Carbon in oxide layers formed under electric discharge conditions

The presence of carbon on the surface and in deep layers of oxide coatings produced by plasmaelectrolytic oxidation is studied. Graphite is found in the coatings formed on titanium under the conditions of cathodic polarization in an organic electrolyte. Carbon in the amount of 16–40 at % is present on the surface of coatings produced on aluminum at the anodic polarization in aqueous electrolytes. Compounds with C-O (oxidized carbon), C-C or C-H (aliphatic carbon), and C-M (carbide carbon) bonds are determined. The carbon content decreases to a few atomic percents upon etching the surface with a high-energy argon beam and removing a nearly 3-nm layer. Aliphatic and metal-oxide carbon is present at this depth. The carbon content on either the surface or in deep layers of the coatings is the same, regardless of the stage of the coating formation, namely, prespark, spark, or microarc anodizing.