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.     

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。     

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.     

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.     

“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.     

工业纯铝硬质阳极氧化的工艺研究

铝硬质阳极氧化法是一种厚层阳极氧化工艺,是铝及铝合金在硫酸电解液中,经过阶梯电流作用而进行的电化学反应.传统铝的硬质阳极氧化需要较低的温度和较高的电压.对工业纯铝在硫酸溶液中采用硬质阳极氧化的方法制取氧化膜的工艺进行了研究,在传统硫酸硬质阳极氧化工艺的基础上进行了改进.相同工艺条件下,在硫酸溶液中加入适量添加剂,可使氧化膜的成长速度大大提高,并拓宽了阳极化允许的温度范围,提高了阳极氧化生产效率.     

Regularity control of porous anodic alumina and photodegradation activity of highly ordered titania nanostructures

A two-step anodizing process was used to prepare wide-range highly ordered porous anodic alumina membrane （PAA） in the electrolyte of oxalic acid. The effects of anodic voltage, anodizing time, size of aluminium foil and additives on the regularity of PAA membrane were also studied in the process of two-step anodization. The template method was combined with the sol-electrophoresis deposition and sol-gel method respectively to prepare highly ordered titania nanostructures. The diameter and length of the obtained nanostructures were determined by the pore size and depth of the PAA template. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were, used to characterize the morphology and phase structure of the PAA template and the titania nanostructures. The results show that the anodizing time and the additive of ethanol have a great effect on the regularity of PAA template. This can be explained from the self-organized process and the current density theory. A theoretical model based on the self-organized process was established to discuss the formation mechanism of PAA template from the chemical perspective. The titania nanostructures prepared with this method has a high specific surface area. Furthermore, the photocatalytic activity of titania nanostructures on methyl orange were studied. Compared with ordinary titania membranes, the titania nanostructures synthesized with this method have higher photodegradation activity.     

Anodizing of magnesium alloy AZ31 in alkaline solutions with silicate under continuous sparking

Anodization is a useful technique for forming protective films on magnesium alloys and improves its corrosion resistance. Based on the alkaline electrolyte solution with primary oxysalt developed previously, the optimum secondary oxysalt was selected by comparing the anti-corrosion property of anodic film. The structure, component and surface morphology of anodic film and cross-section were analyzed using energy dispersion spectrometer (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion process was detected by electrochemical impedance spectroscopy (EIS). The results showed that secondary oxysalt addition resulted in different anodizing processes, sparking or non-sparking. Sodium silicate was the most favorable additive of electrolyte, in which anodic film with the strongest corrosion resistance was obtained. The effects of process parameters, such as silicate concentration, applied current density and temperature, were also investigated. High temperature did not improve anti-property of anodic film, while applying high current density resulted in more porous surface of film.     

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。     

铝的阳极氧化工艺与氧化膜性能

采用硫酸直流阳极氧化在铝表面形成氧化膜,并进行了表面成分深度分布、物相结构、形貌、显微硬度表征。结果表明,氧化膜为无定型Al2O3和Al的夹杂层,O和Al的分布由表及里呈反向变化,硫酸根离子渗入氧化层并在界面处富集,氧化膜的显微硬度较基体有了显著提高。通过正交试验优化了试验工艺条件。     

铝合金阳极氧化方法及成膜机理的研究进展

对铝合金阳极氧化的发展现状及趋势进行了总结和展望。首先,介绍了阳极氧化工艺的类型,并着重阐述了最常用的酸性阳极氧化以及碱性阳极氧化的特点。随后,概括了阳极氧化膜生长机理的研究进展,包括氧化膜的生长过程及提出的相关理论。此外,对碱性阳极氧化的研究现状进行了归纳,并简要介绍了其与酸性阳极氧化在氧化膜结构特点及生长机理方面的异同。最后,针对当前阳极氧化技术存在的问题和面临的挑战,对其未来的发展趋势做了展望,并指出了阳极氧化技术的发展方向。     

二次阳极氧化对6061铝合金氧化膜结构和耐蚀性的影响

目的 研究相同工艺参数下一次阳极氧化和二次阳极氧化对6061铝合金上氧化膜结构的影响,探究基体结构差异性与膜层生长行为及性能间的对应关系。方法 以商业6061铝合金和SPS粉末烧结铝合金为研究对象,针对不同基体在一次阳极氧化和二次阳极氧化过程中,围绕基体组织特征对膜层结构的影响展开系统研究。同时,对不同工艺方法制备出的不同结构特点的氧化膜进行封闭后处理,结合电化学测试方法对膜层的耐蚀性能进行分析对比。结果 相比一次氧化过程,商业6061铝合金和SPS铝合金的二次氧化电流密度分别由12.07、56.62 mA/cm2增加至13.68、64.8 mA/cm2,膜层生长速率增大。同时,一次氧化后在基体表面形成的有序凹坑结构有助于二次氧化中膜层多孔结构有序性的提升,其中SPS烧结铝合金膜层孔洞呈规则的“六边形”结构。二次阳极氧化过程可以有效减少基体表面阴极性金属间化合物颗粒的分布,提高氧化膜的连续性,增强相应膜层的耐蚀性。结论 二次阳极氧化可以使生成的氧化膜层更加均匀规整,且整体耐蚀性显著提高。     

Development of anodic film on Mg alloy AZ91D

At constant applied current, the evolution of morphology, structure and composition of anodic film on Mg alloy AZ91D with anodizing time was investigated using SEM, EDX and XRD. The development of anodic film on the Mg alloy was similar to that on high-purity Mg except that, attributed to alloying effect, hunch-like resultants replaced volcano-like ones to become predominant initial products at transitional stage of anodization. The black cicatrices at the anode surface were related with the inhomogeneous activation and dissolution under strong polarization conditions. The evolution of micropores in shape, size and number was associated with anodizing mechanism. The main elements in anodizing products were Mg, O, Al and Si, indicating that both alloy substrate and electrolyte solution were involved in anodization. Anodic film developed early was mainly comprised of periclase MgO and forsterite Mg₂SiO₄. However, amorphous compounds became dominant with treatment time increasing. In anodizing products, the element Al existed primarily in the form of amorphous compound.     

Pore development during anodizing of Al-3.5 at.%W alloy in phosphoric acid

The study investigates the behaviour of tungsten species during anodizing of a metastable solid-solution Al-3.5 at.%W alloy at a current density of 5 mA cm^− 2 in 0.4 M phosphoric acid at 293 K in order to elucidate the development of pores in anodic alumina. Quantitative measurements of film compositions, by ion beam analysis, have been employed to determine the loss of film species, with film morphologies examined by transmission electron microscopy. The findings indicate anodizing efficiencies, from the period of embryo cell formation to major pore growth, in the range 58-74%. The reduced efficiency is due to loss of aluminium species to the electrolyte. Notably, tungsten species are retained within the anodic films. The anodizing behaviour is consistent with cell and pore development due to flow of material in the barrier layer, under the influences of field-assisted plasticity and film growth stresses. The flow, in combination with the slow migration of tungsten species in the anodic alumina, leads to alumina cells with an outer tungsten-free region and an inner tungsten-containing region.     

Simultaneous plasma-electrolytic anodic oxidation (PAO) of Al-Mg compounds

A process for the simultaneous plasma-electrolytic anodic oxidation (PAO) of a compound consisting of an Al (AlMgSi1) and Mg (AZ31) alloy is introduced. Using this process, an almost uniformly thick, compact oxide coating on both compound partners can be produced provided that the narrow window of this process is determined and kept. The most important parameters for the simultaneous plasma anodizing are the composition and conductivity of the used electrolyte, the current density and the process time. A short-time process using high current densities has been found suitable. This process is a promising procedure for the protection of Al- and Mg-based compound surfaces.     

Effects of anodizing voltage on the anodized and hydrothermally treated titanium surface

Anodic oxidation is the process of creating a titanium oxide layer with various defects more dense and stable. In this study, a dense, stable and porous oxide layer was formed using anodic spark oxidation on pure titanium surface and hydroxyapatite crystals were formed on its surface via a hydrothermal treatment. A mixture of 0.02M−GP (Glycerolphosphate disodium salt) and 0.2M-CA (Calcium acetate) was used as an electrolyte. By increasing the anodizing voltage to 220, 260, 300, and 360 V, the effects of the anodizing voltage were examined by evaluating the film properties after anodization and a hydrothermal treatment. Breakdown occurred around 230 V. As the voltage increased after breakdown, the pore size increased. After the hydrothermal treatment, the amount of HA crystal precipitation was also increased as the voltage increased. The mean surface roughness (Ra) of the anodizing surface was also increased as the voltage increased. The Ra value was larger in the hydrothermally treated group compared with the group treated with anodization as a result of the HA crystals present on the surface after the hydrothermal treatment. Corrosion resistance of the surface modified by anodization was significantly increased in a saline solution compared to that for the non-treated group; this increased further after the hydrothermal treatment. These increases were most likely due to a thick stable oxide layer formed through anodization. Thus, it is believed that titanium with its surface modified through anodic spark oxidation would be a suitable biomaterial due to its corrosion resistance and biocompatibility.     

The bonding strength and corrosion resistance of aluminum alloy by anodizing treatment in a phosphoric acid modified boric acid/sulfuric acid bath

The process of phosphoric/boric/sulfuric acids anodizing was studied as a new pre-treatment for adhesive bonding of aluminum alloys. The microstructure and topography of the anodic films were examined using SEM and AFM, and the adhesive strength and corrosion behavior were studied with lap-shear test, wedge test and electrochemical technology. The results showed that by the process of phosphoric/boric/sulfuric acids anodizing a thicker film with high porosity and big pores can be obtained. The porous film was beneficial to improve the durability and lap-shear strength of the bonding joints. The thicker film can also provide better corrosion resistance. Compared with the films by boric/sulfuric acids anodizing and phosphoric acid anodizing, under humid and hot environments the phosphoric/boric/sulfuric acids anodic film showed better corrosion resistance, higher bonding strength and durability, and is a promising pre-treatment for adhesive bonding of aluminum alloys instead of the chromic acid anodizing process.     

Influence of copper on the morphology of porous anodic alumina

Sputtering-deposited Al-Cu alloy layers and an Al-Cu/Al bi-layer are used to investigate the influences of copper on the morphology of porous anodic alumina films formed galvanostatically in either sulphuric or phosphoric acid electrolyte. The results reveal development of an irregular morphology of pores during anodizing of the alloy layers, contrasting with the linear porosity of films formed on aluminium. Further, the rates of film growth and alloy consumption are relatively low, since oxygen is generated following enrichment of copper in the alloy and incorporation of copper species into the anodic film. The linear morphology is re-established following depletion of the copper in the bi-layer and at the same time, film growth accelerates as oxygen evolution diminishes. The irregular pore morphology is considered to arise from stress-driven pore development influenced by effects of oxygen bubbles within the anodic alumina.     

Pore development in anodic alumina in sulphuric acid and borax electrolytes

The formation of porous anodic films on an Al-3.5 at.%W alloy is compared in sulphuric acid and borax electrolytes in order to investigate pore development processes. The findings disclose that for anodizing in sulphuric acid, the pores develop mainly due to the influences of field-induced plasticity of the film and growth stresses; in borax, field-assisted dissolution dominates. The films formed in sulphuric acid are consequently much thicker than the layer of oxidized alloy and tungsten species are retained in the film. In contrast, with borax, the films and oxidized alloy layers are of similar thickness and tungsten species are lost to the electrolyte. Efficiencies of film growth are also significantly different, about 65% in sulphuric acid and about 52% in borax. The retention of tungsten species during anodizing in sulphuric acid is due to the localization of tungsten in the inner regions of the barrier layer and cell walls, with a layer of anodic alumina separating the tungsten-containing regions from the electrolyte. For borax, the tungsten is distributed more uniformly through the film material, enabling loss of tungsten species to the electrolyte from the pore base.