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。     

“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.     

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.     

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.     

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.     

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.     

Experimental study and modelling of anodizing of aluminium in a wall-jet electrode set-up in laminar and turbulent regime

The influence of heat transfer on anodic oxide growth during anodizing of high purity Al is studied on a laboratory scale in a wall-jet electrode reactor under different flow conditions. Local electrode temperatures are monitored by temperature measurements on the backside of the anode, whereas the effect of local temperature on film growth is evaluated by FE-SEM analyses. Quantitative information on the conditions of heat transfer is provided by numerical calculations of the flow field, and is applied during simulations of the anodizing process. The impact of the flow field, calculated by two different turbulence models, on the simulations is verified.     

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.     

In situ temperature measurement on the metal/oxide/electrolyte interface during the anodizing of aluminum

The temperature development during anodizing processes plays a key role in the case of industrial hard anodizing processes. Commonly, only the bath temperature is controlled; although it is well known that the bath temperature can significantly deviate from the temperature across the interface metal/oxide/electrolyte no investigation is known which shows the temperature deviation in this area. The authors have built a special experimental setup which allows a local temperature measurement across the interface. The results show the possibility of local resolved temperature measurements and the calculation of the heat flow into the metal and the anodizing bath. Based on this knowledge a target control of the current‐voltage‐regime avoids the formation of thermally caused cracks in hard anodized layers.     

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.     

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。     

基于人工神经网络的铝铜合金硬质阳极氧化工艺优化

目的探究Al-5%Cu合金硬质阳极氧化处理的最佳工艺。方法采用硬质阳极氧化试验装置对Al-5%Cu合金进行硬质阳极氧化处理,并用扫描电镜和显微硬度计研究了在硫酸电解液中生成的硬质阳极氧化膜的微观组织结构、厚度及硬度。综合采用正交试验以及人工神经网络的方法,设计了三因素三水平的实验方案,研究了硫酸溶液温度、电流密度和阳极氧化时间对硬质阳极氧化膜的硬度及膜层厚度的影响。利用人工神经网络系统对Al-5%Cu合金阳极氧化的工艺参数进行了优化。结果采用硬质阳极氧化技术可以增加Al-5%Cu合金的表面硬度。制备的氧化膜厚度较均匀,表面质量较好,硬度较高。硫酸溶液的温度是影响表面氧化膜层微观组织及硬度的主要因素。结论 Al-5%Cu合金进行硬质阳极氧化的最佳工艺条件范围为:氧化液温度-9~-7℃,电流密度4~4.8 A/dm2,氧化时间115~120 min。     

Control of silver throwing power by pulse reverse electroplating

The influence of electroplating parameters on throwing power (TP) is studied in additive-free silver cyanide solutions under direct current and pulse reverse electroplating conditions. It is found that the best TP is obtained when no agitation of the electrolyte is applied. The most important parameters for controlling the TP are the cathodic current density, the anodic to cathodic charge ratio, and the ratio between the anodic and cathodic current densities. Guidelines for process optimisation are given.     

Production and characterization of the anodic film on Al-6%Zn-1%Mg alloy

The newly developed high strength aluminum alloy Al-6wt.%Zn- 1wt.%Mg was anodized in acids by direct current to produce a protective anodic coating against abrasion and corrosion. Mechanical properties of the anodized finish, including microhardness, abrasion resistance and fatigue strength were evaluated in terms of the composition and temperature of the electrolyte, applied voltage, current density, duration of anodizing and sealing temperature. Pitting is destructive of the anodized finish particularly in a marine environment and thus can also serve as a direct measure of the efficacy of sealing procedures.The optimum conditions for anodizing Al-6wt.%Zn-1wt.%Mg are a bath of 5 wt.% oxalic acid with 3 wt.% formic acid as an additive, a current density of 4 A dm^-2 for 30 min at 20 °C and sealing in boiling deionized water for 30 min. Results show that this anodized finish possesses good mechanical properties and corrosion resistance.     

Untersuchungen zur Morphologie von Aluminiumhydroxiden und anodischen Aluminiumoxiden mit dem Rasterelektronenmikroskop

Investigations on the morphology of aluminium hydroxides and anodic aluminium oxide films using scanning electron microscope Hydroxide films of spongy structure are originated on aluminium surfaces if aluminium is trated with hot water for short periods. By increasing the reaction time the hydroxide layers start to become more compact until films are growing coherent showing a porous surface. If the reaction time exceeds 4 hours at a reaction temperature of 98°C crystalline scales appear on the top of the films. During the anodic oxydation of hydroxide coated aluminium in citric acid solutions, thin hydroxide films transform into barrier layer type oxides. If the anodization occurs in aggressive electrolytes the existing hydroxide dissolves and oxide layers with porous structure are obtained. Oxide layers produced by anodizing in hot citric acid solutions in the absence of a hydroxide film show a current density dependent morphology. At higher current densities barrier layer type oxides are growing. Using low current densities oxide layers with a character are predominating.     

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.     

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。     

A Novel Anodising Cell

Uniformity of anodising in a batch process can sometimes be difficult to achieve, due to tank lay-out configuration and inconsistencies in air agitation systems. An anodising cell, producing 60 micron anodic films in a phosphoric acid based electrolyte, is described. The principle of the cell is based on anodising electrolyte flow, where the electrolyte is pumped at high speeds past the anode. Heat from the process is removed more efficiently by the electrolyte flow system than with the conventional batch process using air agitation. This results in the production of more uniform anodic films and offers the possibility of anodising at higher current densities. Cell design and monitoring equipment to achieve the above aims are described.     

Influence of surface treatment on detachment of anodic films from Al–Mg alloys

Previous work of the authors has revealed detachment of anodic films during anodizing of electropolished, solid-solution Al–3 at.%Mg alloy at constant current density, with the possibility of the electropolishing pre-treatment having a significant influence on the loss of the film material. Here, anodic films were formed on a similar alloy, with pre-treatment by electropolishing, alkaline etching or mechanical polishing. The results disclose the detachment of the anodic film for all pre-treatments, thus demonstrating that prior electropolishing is not essential for initiation of detachment. However, the occurrence of detachment was sensitive to the current density, with lower current densities promoting detachment at earlier stages of growth of the anodic film for a particular pre-treatment.     

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.