镁-锂合金阳极氧化工艺的研究

采用阳极氧化技术提高镁一锂合金的耐蚀性.使用一种无铬环保型碱性电解液得到了有一定耐蚀性的白色氧化膜.用正交实验优选了电解液中三种组分的质量浓度;用扫描电镜分析了氧化膜表面形貌;用极化曲线研究了氧化膜的电化学腐蚀行为.结果表明:当电解液组成为NaOH 50 g/L,Na2SiO3·9H20 40 g/L,Na2B47·10H2O 30 g/L,Na3C6H5O7·2H2O 40g/L时,获得的阳极氧化膜的耐蚀性最好.EDS和XRD分析表明:氧化膜主要是由MgO,MgCO3两相组成.     

铝锂合金混合酸阳极氧化及无铬封闭研究

为有效提高铝锂合金的耐蚀性能,采用混合酸电解液(硫酸与柠檬酸的混合溶液)进行阳极氧化,然后对阳极氧化膜进行无铬封闭处理,并对阳极氧化膜的微观形貌、表面成分、厚度和耐蚀性能进行了分析表征。结果表明:混合酸阳极氧化后铝锂合金表面形成了均匀多孔的阳极氧化膜,主要含有Al、S和O元素,厚度为12.8μm,其耐蚀性能好于铝锂合金。沸水封闭、锆盐封闭、镍盐封闭和铈盐封闭对阳极氧化膜的厚度几乎没有影响,但封闭后阳极氧化膜表面平整度和致密性改善,耐蚀性能明显提高。铈盐封闭过程中同时生成水合氧化铝、铈氢氧化物和铈氧化物,更好的填充覆盖了孔洞,封闭效果好于沸水封闭、锆盐封闭和镍盐封闭,因此铈盐封闭阳极氧化膜表面更平整致密,抵御腐蚀能力增强,电荷转移电阻较铝锂合金提高了超过一个数量级,腐蚀失重仅为铝锂合金的1/9,可以显著提高铝锂合金的耐蚀性能。     

镁及镁合金环保型阳极氧化工艺研究

研究了镁及镁合金无铬、无磷的环保型阳极氧化工艺测定了镁阳极氧化的稳态伏安曲线和电流密度一时间曲线通过研究氧化电压、电解液中NaOH和Al(0H)3的浓度、电解液温度、氧化时间等对镁阳极氧化成膜的影响，确定了最佳工艺条件分析了最佳工艺条件下得到的镁合金氧化膜的成分、结构与表面形貌，并对镁合金基体与氧化膜的耐腐蚀性能进行了比较结果表明，在环保型阳极氧化液中得到的镁合金氧化膜由镁和铝的氧化物组成，其色泽光滑，结构致密，与镁合金基体相比硬度与耐腐蚀性能都大为提高。     

7050-T7451铝合金阳极氧化膜在模拟舰载环境下的腐蚀行为及疲劳性能衰减研究

通过酸性盐雾试验研究了经苹果酸-硫酸体系阳极氧化处理的7050-T7451铝合金在模拟舰载环境中的腐蚀行为。通过扫描电子显微镜、电化学阻抗谱测量和疲劳性能测试分析了经酸性盐雾腐蚀不同时间后阳极氧化膜结构和基体疲劳寿命的变化。结果表明,阳极氧化膜对铝合金基体具有很好的保护作用,能够保护铝合金基体在酸性盐雾试验的4个周期(192 h)内免受腐蚀。随着酸性盐雾试验时间的延长,阳极氧化7050-T7451铝合金的疲劳寿命逐渐衰减,其演化规律与腐蚀行为的变化基本吻合。     

电压对铝锂合金硬质阳极氧化膜性能的影响

选用2099铝锂合金作为基体进行硬质阳极氧化，并研究电压对硬质阳极氧化膜形貌特征、成分、厚度、硬度、耐磨和耐腐蚀性能的影响。结果表明：随着电压从50 V提高到90 V，硬质阳极氧化膜的结构趋于致密，然后变得疏松，表面粗糙度先降低后增加，厚度先增加后降低，导致硬度、耐磨与耐腐蚀性能表现出明显的差异，但硬质阳极氧化膜的元素组成未变。电压为70 V制备的硬质阳极氧化膜表面结构致密，厚度达到27.3μm，具有高硬度(457.4HV)、良好的耐磨和耐腐蚀性能，平均摩擦系数和腐蚀电流密度仅为0.49和2.02×10^-6 A/cm²，对铝锂合金的防护效率达到95.1%。由于电压提高逐步形成较致密的硬质阳极氧化膜并促使膜层增厚，承载能力、抵抗局部塑性变形能力、阻碍腐蚀介质渗透和抵抗腐蚀能力增强，因此硬质阳极氧化膜的性能明显提高。     

AZ 31镁合金阳极氧化工艺参数的优化研究

采用正交实验对AZ 31镁合金在碱性电解液中进行阳极氧化的工艺参数进行优化。考察了氧化时间、电流密度、脉冲频率和占空比对阳极氧化膜性能的影响,获得最佳阳极氧化工艺参数为:氧化时间15min,电流密度1.0A/dm2,脉冲频率200Hz,占空比10%。采用X射线衍射仪(XRD)、扫描电镜(SEM)和动电位极化曲线等检测手段研究了阳极氧化膜的结构、表面形貌和耐蚀性。结果表明:经优化工艺制得的阳极氧化膜,其主要成分为MgO,Al2O3和MgAl2O4,膜层孔隙分布均匀、致密,耐蚀性大幅提高。     

铜精炼阳极炉用镁-铬耐火材料内衬的气相腐蚀

镁铬耐火材料是铜精炼阳极炉风口常用的耐火材料。除热化学和热机械损耗之外，内衬还要经受气相腐蚀损坏。这里介绍了在伊朗Sarcheshmeh制铜集团（complex）的阳极炉中气相腐蚀的研究结果。由XRD和SEM/EDX对用后的铬镁耐火砖进行了分析。结果表明：在温度约900℃时，耐火内衬因碳沉积而开始破坏。由于耐火材料中含有铁相而使耐火材料的气孔中碳沉淀更加严重。然而对于低铁的铬镁耐火内衬，这种腐蚀将是轻微的。对于尖晶石类耐火材料，未观察到内衬破坏。从实用和经济的观点对阳极炉内衬的上述结果进行了讨论。     

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.     

热水封孔对镁合金阳极氧化膜耐蚀性能的影响

在100g·L-1硼酸盐,50g·L-1铝酸盐,30g·L-1氢氧化物,恒压50V,阳极氧化时间10min的阳极氧化工艺中,制备AD91镁合金阳极氧化膜.研究热水封孔前后阳极氧化膜层的微观结构及耐腐蚀性能.通过扫描电镜(SEM)和极化曲线分别研究了AD91镁合金阳极氧化膜的表面形貌和耐蚀性.结果表明:封孔温度在70℃,时间为10min时,氧化膜层均匀、致密,孔径明显减小;此时阳极氧化膜的耐蚀性也达到了最好.从极化曲线可以看出,腐蚀电位Ecorr为-0.582V,腐蚀电流密度icorr为4.586uA·cm-2,极化电阻Rp为12926.lohm·cm-2.     

铝及铝合金导电氧化工艺经验谈

介绍了铝极其合金导电氧化工艺过程中前处理、阳极氧化以及后处理等工序的操作要点和注意事项     

The influence of Ag and Si additions on the electrochemical behavior in extruded Mg-Zn alloys

Development of new wrought magnesium alloys for the automotive industry has increased in recent years, due to their high potential as structural materials for low density and high strength/weight ratio demands. However, the poor mechanical properties and low corrosion resistance of the magnesium alloys have led to a search for new kinds of magnesium alloys, for better strength, ductility, and high corrosion resistance. The main objective of this research is to investigate the corrosion behavior of new magnesium alloys: Mg-Zn-Ag (ZQ) and Mg-Zn-Si (ZS). The ZQ6X and ZS6X alloys were prepared using the hot extrusion method. AC and DC polarization tests were carried out on the extruded rods, which contain different amounts of silver or silicon. The microstructure was examined using optical and electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that the silver addition decreased corrosion resistance. The addition of silicon also affected corrosion behavior. These results can be explained by the effects of alloying elements on the microstructure of Mg-Zn alloys, such as grain size and precipitates caused by the change in precipitation, and by recrystallization behavior.     

Natural Silk Film for Magnesium Protection: Hydrophobic/Hydrophilic Interaction and Self‐Healing Effect

Biodegradable implants are required in order to provide successful treatment of injuries. Temporary magnesium‐based implants with particular properties are needed in cases when it is desirable not only to maintain vital activity, but also to initiate the self‐healing process of damaged bones or tissues as well. Unfortunately, the use of magnesium alloys is limited due to the fast biodegradability of the applied material. The aim of this research is to improve the corrosion resistance of magnesium alloys by sonochemical treatment in silk solution followed by additional layer‐by‐layer deposition of natural silk on the magnesium surface. The sonication process is carried out at a frequency of 20 kHz during 5–10 min, while the duration of the silk layer deposition is 15 min. The corrosion behavior of magnesium substrates modified by natural silk layer‐by‐layer assembly is studied. Magnesium substrates sonochemically treated in silk solution demonstrate three times better corrosion resistance compared to control samples sonochemically treated in water. Additional deposition of a silk layer enhances obtained corrosion resistance by 18 times, resulting in a 54‐fold increase overall.     

镁合金化学镀镍的研究进展

镁合金应用广泛,但其耐蚀性能很差,化学镀镍层可以为镁合金提供有效的保护作用.论述了镁合金化学镀镍的工艺和基本原理,并对镁合金化学镀镍技术的发展进行了展望.     

Hydroxyapatite-doped poly(lactic acid) porous film coating for enhanced bioactivity and corrosion behavior of AZ31 Mg alloy for orthopedic applications

The corrosion behavior of magnesium and its alloys in the electrolytic physiological environment is extremely poor; this imposes a limitation for their use in orthopedic applications. In the present study, the effect of spray coating AZ31 magnesium alloy with membrane films of pristine and hydroxyapatite-doped poly(lactic acid) on corrosion behavior and bioactivity is investigated. Polymer concentration was found to have a strong impact on the pore size of the coating layer. However, addition of HAp NPs distinctly stimulated the precipitation of an apatite-like compound upon soaking the samples in a simulated body fluid (SBF). Magnesium coated samples revealed three orders of magnitude less corrosion compared to the naked samples, which indicates a stable electrochemical corrosion resistance. During a 15 days in-vitro test, pH variation, weight loss, and bending strength were lower for the coated samples (with average values of 8.5%, 7.2% and 10%, respectively) than the control sample (10.5%, 15.5%, and 25%, respectively). Moreover, the coated samples showed good bending strength characteristics. Cytocompatibility studies on MC3T3 cells revealed a continuous increase in cell growth with the coated samples. Overall, the suggested strategy might open a new avenue to widen utilization of Mg alloys as implant materials for orthopedic applications.     

镁及镁合金的防护处理现状分析

综述了镁及镁合金防护存在的问题、影响因素及防护方法。对镁合金表面防护包括化学转化膜、阳极氧化、金属镀层等技术所涉及的理论基础及存在问题进行了概括与分析。并对镁合金耐蚀性研究的发展趋势作了展望。     

Electrochemical corrosion behavior of magnesium and titanium alloys in simulated body fluid

The electrochemical behavior of AZ91D and Ti–6Al–4V alloys was investigated in simulated body fluid (SBF) at 37 °C. The aim of the present study was to evaluate their corrosion performance through the analysis of corrosion resistance variation with time, using electrochemical impedance spectroscopy (EIS) tests and corrosion current density using potentiodynamic polarization measurements. Very low current density was obtained for Ti–6Al–4V alloy compared to that of AZ91D alloy, indicating a typical passive behavior for Ti alloy. EIS results exhibited high corrosion resistance indicating a highly stable film on titanium alloy compared to magnesium alloy in SBF.     

Recent progress in corrosion protection of magnesium alloys by organic coatings

The excellent properties of magnesium alloys, especially the high strength/weight ratio, make them desirable materials in the automotive industry. However, their high corrosion susceptibility has greatly limited or even prevented their larger scale use for various applications. Organic coating is one of the most effective ways to prevent magnesium alloys from corrosion. In this report, the recent progress of organic coatings on magnesium alloys and techniques for evaluating the performance of organic coatings are reviewed.As a critical layer in a normal coating system, organic coating has great potential to prevent magnesium alloys from corrosion attack. However, some unsolved problems currently limit the application of organic coatings. Firstly, organic coatings usually have poor adhesion if they are applied without an appropriate pre-treatment. Sol–gel coating or plasma polymerization requires the least pre-treatment prior to deposition. However, the corrosion and wear resistance of these coatings have not been documented. Secondly, it is difficult to prepare a uniform, pore-free organic layer. So, it is usually necessary to apply multiple layers of these coatings to provide sufficient/optimum corrosion and wear resistance. Finally, a number of organic coating techniques are still solvent based, which poses an environmental concern. New water-borne and powder coating technologies should be developed.In order to evaluate the performance of organic coatings on magnesium, both electrochemical and non-electrochemical techniques have been developed. Information from different techniques gives insight into the organic coating/magnesium alloy interface in different aspects. Comprehensive knowledge about the interface is indispensible for understanding the degradation of the organic coating and developing new coating strategies.     

镁合金化学镀工艺研究

向镀液中加入氰化物，采用硫酸镍代替碳酸镍作为镍源，开发出一种镁合金化学镀镍新工艺。测定了该镀层中的磷含量及其耐蚀性、显微硬度、结合力，并用扫描电镜对其表面形貌进行了观察结果表明，该镀层结合力合格，硬度远高于镁合金基体，且与普通化学镀层相当；该镀层属高磷镀层，耐蚀性较好，但与普通基体材料上的化学镀层相比要差一些。该工艺使镁合金化学镀成本大大降低，工艺得到简化。     

High corrosion resistance of magnesium coated with hydroxyapatite directly synthesized in an aqueous solution

Anticorrosion coatings are crucial for practical applications of magnesium alloys, which are used to reduce the weight of vehicles, aircraft, electronics enclosures etc. Hydroxyapatite (HAp) potentially offers high corrosion resistance and no environmental toxicity because its thermodynamic structural stability is high and it is a basic component of bone. However, direct synthesis of HAp on magnesium in aqueous solutions has been a scientific challenge because Mg ions prevent HAp crystallization. A new method of direct synthesis of HAp on magnesium was developed using a Ca chelate compound, which can maintain a sufficiently high concentration of Ca ions on the magnesium surface to overcome prevention of HAp crystallization with Mg ions. Highly crystallized HAp coatings were successfully formed on pure magnesium and AZ series alloys. Corrosion behavior of HAp-coated pure magnesium was examined by cyclic dry and wet tests with 1 g m⁻² NaCl on the surface and polarization tests in a 3.5 wt% NaCl solution. A HAp-coated pure magnesium showed no noticeable corrosion pits after the dry and wet test. HAp-coated specimens showed 10³-10⁴ times lower anodic current density than as-polished specimen in the polarization test. The results demonstrate the remarkable anticorrosion performance of HAp coatings on magnesium for the first time.     

Effect of process parameters of plasma electrolytic oxidation on microstructure and corrosion properties of magnesium alloys

In this work, a plasma electrolytic oxidation process was applied to AZ91 and AM50 magnesium alloys and commercially pure magnesium to produce a protective surface layer. The plasma electrolytic oxidation process was carried out in an alkaline phosphate solution with a DC power supply, using relatively high current densities and short treatment times. The influence of some important process parameters such as current density, treatment time and voltage was studied. The layers were characterised by scansion electron microscopy, X-ray diffraction and X-ray photoelectron spectrometry, in order to investigate the effect of the process parameters on the microstructure and chemical composition. The corrosion resistance properties of the obtained layers were investigated by potentiodynamic anodic polarization and electrochemical impedance spectroscopy tests. The current density, applied during the treatment, influenced the morphology and the thickness of the coatings, and, consequently, the corrosion resistance. The corrosion tests evidenced that the layers obtained with plasma electrolytic process provided a good corrosion protection to the magnesium and magnesium alloys.