Effect of TiO2 nanoparticles on the microstructure and corrosion behavior of MAO coatings on magnesium alloy

The microstructure and corrosion behavior of the micro‐arc oxidation (MAO) coatings modified by TiO₂ on AZ91 magnesium alloys were investigated by SEM, EDS, XRD, electrochemical analysis and drop test, respectively. The modified MAO coatings were consisted of not only MgAl₂O₄ and MgO, which usually could be found in MAO coatings on the AZ91 alloys, but also a small quantity of Ti. With increasing the contents of TiO₂ nanoparticles from 0 to 4.8 g/L in the electrolyte, the coatings thickness increased from 19 to 24 µm, and the color of the MAO coating changed from light gray to dark. The addition of TiO₂ could effectively decrease the number of the pores and improve the density of the coatings. The corrosion potential of the modified coatings positively shifted about 180 mV and the corrosion current density declined and the drop time increased. The mechanism of the corrosion resistances of the modified coatings lay in the fact that TiO₂ nanoparticles could increase the thickness and the density of the coatings on the AZ91 magnesium alloys.     

Growth,corrosion and wear resistance of SiC nanoparticles embedded MAO coatings on AZ31B magnesium alloy

In this research, nanocomposite coating was deposited on magnesium matrix AZ31B alloy using the micro arc oxidation (MAO) method. MAO was carried out in SiC-nanoparticles containing suspension using the sodium silicate and sodium aluminate bases at constant current density. The effect of nanopowder addition and MAO periods were also investigated in the present work. Using the Scanning electron microscopy (SEM), the thickness and surface morphology of the coatings were studied. The coefficient of friction and abrasion rate curves were used to analyze nanopowder addition on resistance to abrasion, while the potentiodynamic curves were used for assessing the resistance to corrosion in the ceramic nanocomposite coating deposited on surface of alloy AZ31B. The morphological studies on surface of coatings revealed that the cavitation level and size increases with the increasing coating duration. Besides, Energy Dispersive X-Ray Diffraction (EDS) analyses from cross section and surface of the prepared coatings revealed that nanopowder distribution on interface of coating with matrix and boundaries of the cavities is almost uniform. The cross section studies of the coatings revealed that their thickness increases, as coating duration prolongs. Furthermore, the corrosion behavior of the samples indicated that presence of nanopowder does not significantly affect the resistance to corrosion of the coatings; however, coefficient of friction and abrasion rate of coatings indicates a respective rise and drop in presence of these nanopowders.     

纯铜热化学反应热喷涂陶瓷/渗铝复合涂层耐蚀性研究

采用火焰喷涂技术在铜基体表面先后喷涂渗铝层和陶瓷涂层,并加热保温,制备成铜基陶瓷/渗铝复合涂层。用XRD和SEM对涂层进行组织结构分析和形貌观察,并测试涂层的硬度、抗热震性和耐蚀性。结果表明,复合涂层中有Cu9Al4、Cu5Zn8、Cu3Ti等新相生成;渗铝层部分有γ2相（Cu9Al4）析出且涂层与基体结合紧密;复合涂层的硬度为82～87 HRE,其耐热震次数可达50次以上;复合涂层封孔后的耐酸蚀能力提高到基体的16倍,耐盐蚀能力提高到基体的25倍;极化试验表明,复合涂层抗电化学腐蚀能力显著增强,其耐蚀性能远优于纯铜渗铝层和单纯陶瓷涂层。     

Corrosion resistance of composite coating on magnesium alloy using combined microarc oxidation and inorganic sealing

The combined microarc oxidation (MAO) and inorganic sealing process was used to deposit a composite coating to improve the corrosion resistance of AZ31 magnesium alloy.The surface morphologies of the resulting duplex coatings were studied by SEM.Furthermore,the corrosion resistance of the coated Mg alloy substrates was investigated using electrochemical workstation and dropping corrosion test.The results show that the composite coating surface consists of Mg,Si,O and Na.It is difficult to deposit inorganic coating on a thick MAO coating surface.As the composite coating was solidified by CO2 under 175 °C,it exhibits a better corrosion resistance than the MAO monolayer,owing to the thick and compact inorganic coating.     

Corrosion behaviour of thermally sprayed Al and Al/SiCp composite coatings on ZE41 magnesium alloy in chloride medium

Thermally sprayed Al and Al/SiCp composite coatings have been deposited on ZE41 magnesium alloy and mechanical compaction at room temperature was applied to the Al and Al/SiCp coatings to reduce their porosity. Corrosion behaviour of coated samples was evaluated and compared to that of uncoated substrate in 3.5 wt.% NaCl solution using electrochemical measurements. Al and Al/SiCp composite coatings reduced the corrosion current density of Mg-Zn alloys by three and two orders of magnitude, respectively, and reductions up to four orders of magnitude were obtained after mechanical compaction.     

羟基磷灰石/氧化石墨烯/氢氧化镁复合涂层镁-钙合金的耐蚀性及骨折修复效果研究

镁金属在生理环境中的降解速率和生物活性改善有助于其在生物医用领域的应用推广,合金化处理和表面改性是两种有效的途径。本文针对镁-钙合金(ZQ)提出一种新的改性方法,利用水热处理、电泳沉积和电化学沉积的结合,在其表面上构建羟基磷灰石/氧化石墨烯/氢氧化镁(HA/GO/ Mg(OH)2)复合涂层。扫描电镜(SEM)和X-射线衍射(XRD)分析证实,该复合涂层样品(ZQ-HEP)表面逐层形成了外层纳米薄片HA、中层絮片状GO、及内层Mg(OH)2纳米片的复合涂层。体外电化学耐腐蚀性测试分析表明,涂层化的ZQ-HEP比未处理ZQ样品在磷酸缓冲盐溶液(PBS)中有更优的耐蚀性。通过构建的体内兔股骨髁骨折模型,评价表面改性前后ZQ样品的骨折修复效果。术后大体观察、影像学和组织学分析证实,体内生理环境下ZQ-HEP螺钉比ZQ螺钉能降低析氢速率,减少皮下气肿现象。同时,ZQ-HEP螺钉因其更优的耐蚀性,在术后4周内可较好地保持其材料的完整性,同时介导更多的新骨长入,进而实现骨折的快速愈合。本研究提出的GO/HA/ Mg(OH)2复合涂层构建策略,可在调控镁金属降解速率的同时,显著提升其成骨修复效果,具有良好的临床应用前景。     

RE-Fe基合金热喷涂层的耐腐蚀性能

通过热喷涂的方法制备了添加稀土组分和适量铜组元的RE-Fe基合金涂层。采用液态浸渍法、电化学测试、盐雾实验以及涂层表面腐蚀形貌SEM观察等方法对不同成分、不同喷后处理工艺的RE-Fe基合金涂层的耐腐蚀性能进行研究。结果表明:添加适量的稀土组分和铜组元,使Fe基合金涂层的自腐蚀电位正移,维钝电流密度和致钝电流密度下降,明显地提高了Fe基合金(Fe-Cr-Ni-B-Si)涂层在酸类腐蚀介质中的耐腐蚀性能;同时也有效地提高了涂层抗盐雾气氛腐蚀的能力;其中以添加2%RE氧化物(质量分数)涂层(封孔后)的综合效果最佳。     

Corrosion fatigue behavior of the high-strength magnesium alloy AZ 80

The fatigue performance of the high-strength magnesium alloy AZ 80 is studied in air as well as in aqueous 0.5 and 3.5% NaCl solutions. The effect of mechanical surface treatments, specifically mechanical polishing, shot peening, and roller burnishing on the S-N curves, is investigated using an electropolished surface as a reference. While mechanical polishing as well as shot peening improves fatigue performance in air, no improvement is observed in NaCl solutions. However, roller burnishing, which combines a smooth surface finish with residual compressive stresses in sufficient depths, leads to outstanding fatigue performance even in 3.5% NaCl solution.     

Corrosion behavior of pure Mg and AZ31 magnesium alloy

Protection of Metals and Physical Chemistry of Surfaces - Purpose of this article is to study corrosion behavior of pure magnesium and AZ31 magnesium alloy in electrolyte containing different...     

镁合金微弧氧化陶瓷层的耐蚀性

通过NaCl中性盐雾腐蚀试验定性地分析镁合金微弧氧化陶瓷层的耐蚀性，初步研究了陶瓷层表面微观结构对其耐蚀性的影响。结果表明：镁合金微弧氧化陶瓷层的微观组织结构的结合方式和生长方式直接影响其耐蚀性，微弧氧化试样的耐蚀性与陶瓷的厚度有关，陶瓷层厚度的增加并不一定能使其耐蚀性提高。     

Preparation and corrosion resistance of superhydrophobic coatings on AZ31 magnesium alloy

In order to improve the corrosion resistance of the Mg alloys, the superhydrophobic coatings on AZ31 Mg alloy were prepared by a two-step process of micro-arc oxidation treatment and superhydrophobic treatment in stearic acid ethanol solution. The effects of voltages, frequencies and treatment time on the contact angle of the superhydrophobic treated sample were investigated. The results showed that with increasing the voltage, frequency and treatment time, all of the contact angles of the superhydrophobic treated sample increased first, and then decreased, reaching the maximum values at 350 V, 1000 Hz and 5 min, respectively. The optimal superhydrophobic coating was mainly composed of MgO and Mg₂SiO₄ phases, with the pore diameter of ～900 nm, the thickness of ～6.86 μm and the contact angle of 156.96°. The corrosion current density of the superhydrophobic AZ31 sample decreased by three orders of magnitude, and the amount of hydrogen evolution decreased by 94.77% compared with that of the AZ31 substrate sample.     

ME20镁合金阳极氧化膜耐蚀性研究

采用正交试验,开发出一种新型环保镁合金阳极氧化的电解液配方,研究在此工艺下形成的阳极氧化膜的对蚀性.采用EDAX、XRD、SEM对阳极氧化膜的成分、结构和形貌进行研究.结果表明,获得的陶瓷层分布均匀,表面光滑致密,耐蚀性显著加强.     

Corrosion behavior of the composite ceramic coating containing zirconium oxides on AM30 magnesium alloy by plasma electrolytic oxidation

The deterioration process of a plasma electrolytic oxidation (PEO) coating containing zirconium oxides on AM30 magnesium alloy in 3.5 wt.% NaCl solution have been investigated. The coating consists of an outer porous layer and an inner dense layer. The content of MgF₂ is high in the pores and an MgO-rich layer is evident in the inner layer. The corrosion resistance of the outer layer gradually decreases in the initial immersion stage (96 h) due to the decomposition of MgO, and the deterioration of the inner layer is delayed by the blocking effect of the outer layer.     

Corrosion behavior of laser melted AZ91HP magnesium alloy

AZ91HP magnesium alloy was melted by CO₂ laser. Compared with as‐received Mg alloy, the grain of the melted layer was refined significantly and the content of Al was increased. The corrosion resistance of the melted layer was improved because of the grain refinement, the redistribution of β‐Mg₁₇Al₁₂ and the increasing of the Al content. As compared to the non‐overlapping zone, the overlapping zone of the melted layer was liable to be corroded.     

镁合金在镀液中的腐蚀行为

摘要：通过腐蚀实验和阳极极化曲线研究了硫酸镍主盐配制的化学镀镍液成分和温度对AZ91D镁合金的腐蚀行为的影响，比较了碱式碳酸镍主盐和硫酸镍主盐两种镀镍液的腐蚀性以及施镀后的镀层质量。结果表明：硫酸镍镀液的腐蚀性比碱式碳酸镍镀液大，在低温下，镁合金在硫酸镍镀液中表面的氟化镁膜不致密，镀液对基材的腐蚀性高；而在高温下，Mg^2 与F^-的反应性增强，氟化反应完全，形成的氟化镁钝化膜致密性高，可保护镁合金基体免遭镀液的腐蚀。在施镀温度下，镀液中F^-的缓蚀作用，可使SO4^2-离子对镁合金的腐蚀速率大大降低。     

汽车发动机用AZ91镁合金的腐蚀行为

采用腐蚀失重试验、极化曲线法和扫描电镜研究了AZ91镁合金在不同成分的汽车发动机冷却液中的腐蚀速率,Tafel曲线和腐蚀形貌,分析了不同发动机冷却液对镁合金耐腐蚀性能的影响。结果表明,组分为55%乙二醇+无机盐添加剂+有机羧酸的冷却液抑制AZ91镁合金腐蚀的效果最佳。     

Corrosion resistance of Mg-Mn-Ce magnesium alloy modified by polymer plating

Polymeric nano-film on the surface of Mg-Mn-Ce magnesium alloy was fabricated by polymer plating of 6-dihexylamino-1,3,5-triazine-2,4-dithiol monosodium(DHN) to improve its corrosion resistance.The electrochemical reaction process was analyzed by cyclic voltammetry and two obvious peaks of oxidation reaction were observed.The static contact angle of distilled water on polymer-plated surface can be up to 106.3°while on the blank surface it is 45.8°.Potentiodynamic polarization results show that the polyme...