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。     

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.     

工艺因素对镁合金微弧氧化膜层性能的影响

本文通过对镁合金微弧氧化膜制备中电流密度、电压、脉冲频率、占空比、电解液配方、浓度、温度、电导率、氧化时间等的分析,表明电参数和非电参数都是影响微弧氧化膜层形成、组织结构和性能的重要因素.     

电解质对AZ91D镁合金微弧氧化的影响

在Na2SiO3和NaAlO2为主成膜剂的硅铝复合电解液中,利用交流脉冲电源对AZ91D镁合金进行微弧氧化处理,研究主成膜剂含量的变化对微弧氧化过程及膜层特性的影响规律。利用扫描电镜(SEM)和膜层测厚仪分别研究了膜层的微观形貌和膜层厚度,通过电化学阻抗谱(EIS)测试膜层在3.5%NaCl中性溶液中的耐蚀性能。结果表明,随着主成膜剂含量的增加,微弧氧化过程中起弧电压和终止电压均呈下降的变化趋势,而膜层耐蚀性则基本呈先增大后降低的变化趋势,膜厚的变化趋势与其耐蚀性一致;Na2SiO3含量的变化对膜层内部致密层和外部疏松层的耐蚀性均有影响,而NaAlO2含量的变化则主要影响膜层内部致密层的耐蚀性;适量的主成膜剂含量是获得致密耐蚀膜层的关键。     

过电压对镁合金微弧氧化膜层性能的影响

采用自行研制的大功率微弧氧化电源在频率700 Hz、占空比20%的条件下进行微弧氧化实验:并测量陶瓷膜层的厚度,观察膜层微观形貌,通过盐雾试验来评定陶瓷膜层的耐蚀性.研究发现:随过电压的升高,镁合金微弧氧化膜层厚度增加,表面熔融物颗粒增大,膜层表面变粗糙,陶瓷层的耐蚀性呈先增加后降低的趋势;并且陶瓷膜层耐蚀性在过电压为100～150 V时较好,因此镁合金微弧氧化要选择适当的过电压.     

电流密度对镁合金微弧氧化膜层性能的影响

在电流密度分别为3、6、9、12 A/dm2时,用微弧氧化的方法在碱性电解液体系中制备了镁合金微弧氧化膜,考察了不同电流密度对生成的氧化膜层厚度、硬度的影响规律;用XRD分析了氧化膜层的相结构;并采用NaCl溶液浸泡试验和中性盐雾试验,考察了氧化膜的耐蚀性能。结果显示:随着电流密度的增大,膜层的厚度、硬度均呈增加的趋势;陶瓷层主要由MgO、Mg2SiO4和非晶相组成;得到的氧化膜层具有优良的耐蚀性能。     

电流密度对镁合金微弧氧化膜层性能的影响

在电流密度分别为3、6、9、12A/dm2时,用微弧氧化的方法在碱性电解液体系中制备了镁合金微弧氧化膜,考察了不同电流密度对生成的氧化膜层厚度、硬度的影响规律;用XRD分析了氧化膜层的相结构;并采用NaCl溶液浸泡试验和中性盐雾试验,考察了氧化膜的耐蚀性能.结果显示：随着电流密度的增大,膜层的厚度、硬度均呈增加的趋势;陶瓷层主要由MgO、Mg2SiO4和非晶相组成;得到的氧化膜层具有优良的耐蚀性能.     

TiN颗粒对镁合金微弧氧化过程及膜层性能的影响

目的分析Ti N颗粒在镁合金微弧氧化过程中的作用,并研究其在膜层中对镁合金硬度、耐磨和耐蚀等性能的影响。方法通过在微弧氧化电解液中添加2.7μm Ti N颗粒,并使其充分分散于电解液中,使电解液中Ti N颗粒的质量浓度分别为0、2、4、6 g/L,并控制其他实验参数(如电流密度、频率、占空比和氧化时间)一样的情况下进行实验,通过电子显微镜、涂层厚度测厚仪、显微维氏硬度计、X射线衍射和电化学工作站,分别从膜层的表面形貌、厚度、硬度、相组成及耐蚀性等方面,研究了Ti N颗粒对镁合金微弧氧化膜层性能的影响。结果在微弧氧化电解液中添加Ti N颗粒后,相同电化学参数下制得的微弧氧化膜层变得致密,厚度、硬度有所增加,氧化膜层主要由Mg、MgO、Mg2Zr5O12、Ti N组成。极化曲线显示,加入Ti N颗粒,制备的微弧氧化膜层比未加入Ti N颗粒制得的膜层的腐蚀电流下降了2个数量级。阻抗图谱表明,电阻值增加了1个数量级。结论 Ti N颗粒能够随镁合金的微弧氧化过程进入制得的氧化膜层中,并且能够增加膜层厚度和硬度,使膜层的耐磨、耐蚀性得到提高。     

镁合金微弧氧化技术及其膜的耐蚀性能

本文介绍了微弧氧化技术的几种成膜机理;论证了镁合金微弧氧化膜具有很好的耐蚀性能,且微弧氧化工艺比普通的阳极氧化工艺简单。同时,镁合金的微弧氧化膜层还具有耐磨性、电绝缘性等一些优良性能,这使得微孤氧化技术有广泛的应用前景。     

有机添加剂对镁合金阳极氧化膜性能的影响

镁合金作为一种轻质工程材料,具有密度低、比强度和比刚度高、减震性好、导电导热性好、磁屏蔽性能优良等特点,在航空、汽车、通讯和光学领域具有很大的应用前景[1～3].但是镁的化学性质活泼,即使在室温下也会发生氧化腐蚀[4,5],阻碍其在工业     

Effects of electrolytes on properties of anodic coatings formed on AZ91HP magnesium alloy

In a basic solution containing 10 g/L NaOH, the thickness, morphology and corrosion resistance of anodic coatings formed in solutions without and with additions of Na2SiO3, Na2CO3, Na2B4O7 and Na2SnO3 were separately determined and evaluated. The results show that the electrolytes used above take part in the coating formation and the obtained anodic coatings contain elements from the electrolytes. These electrolytes, especially Na2SiO3 and Na2B4OT, contribute to the film thickness. The coating uniformity obtained by addition of Na2SiO3 is the best, while Na2CO3, Na2B4O7 and Na2SnO3 decrease the number of pores per area on the coatings surface though they worsen the uniformity of the anodic coatings. In addition, the anodic coatings formed in solutions with addition of Na2CO3 or Na2SnO3 exhibit loose and net-like structure. Na2SiO3 and Na2B4O7 can significantly improve the corrosion resistance of the anodic coatings while Na2CO3 and Na2SnO3 have minor effects on improving the coating corrosion resistance.     

Effects of electric parameters on corrosion resistance of anodic coatings formed on magnesium alloys

Anodic coatings were obtained by micro-arc oxidation on AZ91HP magnesium alloys in a solution containing 10 g/L NaOH and 8 g/L phytic acid. The effects of electric parameters including frequency, final voltage, duty cycle and current density on the corrosion resistance of anodic coatings formed on the magnesium alloys were investigated by using an orthogonal experiment of four factors with three levels. The results show that the final voltage plays a main role on the coating properties. The orders of affecting corrosion resistance and coating thickness are separately ranked from high to low as, final voltage>duty cycle>current density>frequency and final voltage>current density>frequency>duty cycle. The final voltage influences the corrosion resistance of the anodized samples mainly by changing the surface morphology and coating thickness.     

电参数对镁合金阳极氧化膜性能影响的研究进展

阳极氧化是提高镁合金耐蚀性的一种有效方法,选择的电参数对氧化膜性能影响很大。介绍了电参数如频率、占空比、电流密度、终电压等的概念,推导了占空比与电流密度的关系,并综述了电参数对阳极氧化膜性能影响的研究进展。随着电子技术在氧化电源上的广泛应用,氧化设备的发展趋势为更加智能化以及频率越来越高。     

环保型电解质对溶液电导率的影响

在含硅酸钠的碱性基本溶液中,研究植酸(C<,6>H<,18>O<,24>P<,6>)浓度对溶液电导率的影响.采用四因素三水平正交实验,研究环保型电解质如氢氧化钠(NaOH)、硅酸钠(Na2SiO2·9H2O)、硼酸(H>.38>O3)、钨酸钠(Na2WO<,4>·2H2O)、铝酸钠(NaAlO2)和碳酸钠(Na2CO3)对溶液电导率的影响规律.结果表明:随着植酸和硼酸浓度增加,溶液电导率减小;随着NaOH、Na2SiO3·9H2O、Na2WO<,4>·2H2O、Na2CO3和NaAl2浓度增加,溶液电导率增大.     

Effects of sodium tungstate on properties of micro-arc coatings on magnesium alloys

Anodic coatings were prepared by micro-arc oxidation on AZ91HP magnesium alloys in a base solution containing 10 g/L NaOH and 12 g/L phytic acid with addition of 0-8 g/L sodium tungstate. The effects of sodium tungstate on the coating thickness, mass gain, surface morphology and corrosion resistance were studied by eddy current instrument, electronic scales, scanning electron microscope and immersion tester. With the addition of sodium tungstate, the electrolytic conductivity increases and the final voltage decreases. The sodium tungstate has a minor effect on the coating thickness, but lightens the coating color. With increasing sodium tungstate concentration, the size of micropores on the coatings is enlarged and the corrosion resistance of the anodized samples decreases.     

Influence of sodium silicate concentration on properties of micro arc oxidation coatings formed on AZ91HP magnesium alloys

In a base solution containing 10 g/L sodium hydroxide and 12 g/L phytic acid, the influence of sodium silicate concentration on the formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on magnesium alloys was systematically studied. The results demonstrate that sodium silicate can increase the solution conductivity, decrease the final voltage and change the coating color. Amorphous magnesium silicate is detected and the silicon content in the coatings continually increases with the increasing of sodium silicate concentration. Silicate ions can simultaneously combine with magnesium and aluminum ions to develop anodic coatings, while phytic acid radicals preferentially react with magnesium ions. Sodium silicate can further improve the corrosion resistance of MAO treated magnesium and the coating shows the best corrosion resistance in the base solution with 10 g/L sodium silicate.     

Formation and properties of stannate conversion coatings on AZ61 magnesium alloys

The effects of solution composition and temperature on the microstructure and corrosion resistance of stannate conversion coatings on AZ61 magnesium alloys were investigated. The conversion coating consisted of a porous layer as under layer intimately contacted with the magnesium plate and a hemispherical particle layer as major overlay formed right on top of the porous layer. During the coalescence of the hemispherical particles to form a complete coating on the magnesium alloy, some sites of discontinuity inevitably left and determined the corrosion resistance of the coating evaluated using a salt spray test. Increasing bath stannate ion concentration and lowering bath pH increased the population density of the hemispherical particles whose size was accordingly reduced. The corrosion resistance of the conversion coating was improved with finer particles, which were preferably formed at less alkaline solution with higher stannate ion contents. Furthermore, the conditions favoring the formation of finer particles also reduced the immersion time necessary for producing the conversion coating with optimal corrosion resistance.     

Structure and properties of ceramic coatings formed on aluminum alloys by microarc oxidation

The thick and hard ceramic coatings were deposited on 2024 AI alloy by microarc oxidation in the electrolytic solution. Microstructure, phase composition and wear resistance of the oxide coatings were investigated by SEM, XRD and friction and wear tester. The microhardness and thickness of the oxide coatings were measured. The results show that the ceramic coating is mainly composed of α-Al2O3 and γ-Al2O3. During oxidation, the temperature in the microarc discharge channel is very high to make the local coating molten. From the surface to interior of the coating, microhardness increases gradually. The microhardness of the ceramic coating is HV 1 800, and the microarc oxidation coatings greatly improve the antiwear properties of aluminum alloys.     

Characterisation of anodic films formed on titanium and its alloys

The properties of the anodic oxide films formed on titanium and its implant alloys Ti‐5Al‐4V and Ti‐6Al‐4Fe are investigated in this paper. Anodic oxide films were prepared by electrochemical treatment in 3M sulphuric acid solution at 60 V for 1 min, followed by a thermal treatment consisting of heating at 500°C for 24 h and then cooling in water. Electrochemical impedance spectroscopy (EIS) measurements were carried out at open circuit potential. Nyquist and Bode spectra exhibit a two‐time constant system, attesting an oxide with two layers: a barrier inner oxide and a porous outer one. All spectra change in time, indicating a thickening of the films. Open circuit potentials were monitored (long‐term, 25,000 exposure hours) in Ringer 2 solution of different pH values (6.98, 4.35, 2.5) for titanium, Ti5Al‐4V and Ti‐6Al‐4Fe alloy but without treatment with the purpose to compare the biomaterial behaviour. It was pointed out some variations of the open circuit potentials around electropositive values, suggesting slow dissolution, re‐passivation or adsorption processes.     

电参数对镁合金微弧氧化膜厚度的影响

在自行研制的电解液中,采用四因素三水平正交实验,系统研究频率、占空比、电流密度和终电压对AZ91HP镁合金氧化膜厚度的影响。结果表明,各因素的主次顺序为终电压〉电流密度〉占空比〉频率。终电压对氧化膜厚度影响显著,电流密度对氧化膜厚度有影响但不显著,占空比和频率对氧化膜厚度无显著影响。氧化膜层的耐蚀性并不是仅仅由厚度决定,而是由多种因素综合作用的结果。