镁合金微弧氧化预处理化学镀镍研究

镁合金微弧氧化(MAO)预处理后,无需碱洗酸洗活化等传统预处理直接在硫酸镍溶液中化学镀镍。表征了镀镍层的显微结构与成分,研究了MAO预处理对镀层厚度、硬度、导电性及耐蚀性的影响。结果表明:含有Ni,P两种元素的镀层由均匀分布的胞状颗粒组成。MAO预处理显著影响镀层的厚度与导电性;当MAO薄膜从3μm增厚至7μm时,镀层的厚度快速增大而方块电阻迅速下降。极化曲线测试表明,当MAO薄膜厚15μm时化学镀镍镁合金的腐蚀电位最高,腐蚀电流最小。48h盐雾实验表明,MAO预处理化学镀镍镁合金的耐蚀性显著优于传统预处理化学镀镍镁合金。     

AZ31B镁合金表面微弧电泳复合膜层微观结构及耐蚀性表征

采用微弧氧化技术在AZ31B镁合金表面制备陶瓷层,利用其表面多孔结构借助电泳技术沉积有机膜层,对比研究陶瓷层和复合膜层表面粗糙度、表面及截面形貌、电化学性能及划伤腐蚀特性。结果表明:陶瓷层表面放电微孔被电泳层完全填充并形成均匀膜层,复合膜层表面粗糙度明显降低;微弧电泳复合膜层腐蚀电流密度与陶瓷层和基体相比分别降低2个和4个数量级,极化电阻分别增大2个和4个数量级,腐蚀倾向降低;微弧电泳复合膜层电化学阻值与陶瓷层相比增加4个数量级,同时电容值降低4个数量级,耐蚀性显著提高;由于陶瓷层与电泳层的机械嵌合作用,复合膜层划伤腐蚀过程表现为基体腐蚀及陶瓷层与基体界面的破坏,复合膜层界面处结合完好。     

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。     

纯镁表面等离子体电解渗硼与微弧氧化复合膜的制备及耐蚀性

目的 在纯镁表面制备新型复合膜,以提高其耐蚀性.方法 先在硼砂系电解液中对纯镁进行等离子体电解渗硼(PEB)处理,预制表面改性层,然后在硅酸盐系电解液中对其进行微弧氧化(MAO)处理,从而获得PEB+MAO新型复合膜.分别使用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析膜层的微观结构、元素分布及物相组成,膜层的耐蚀性则通过动电位极化曲线和电化学阻抗谱(EIS)来表征.结果 纯镁的等离子体电解渗硼过程经历了电离、置换、吸附和扩散四个阶段,获得的PEB表面改性层由氧化层和扩散层组成.在PEB+MAO复合膜的生长过程中,膜层在其厚度方向存在重叠的现象,而不是逐层的简单堆积.等离子体电解渗透时,硼元素渗入后所形成的渗层区域降低了纯镁基体表面的化学活性,改善了其微观组织结构,进而使PEB+MAO复合膜的腐蚀电流密度较基体、单一PEB改性层和单一微弧氧化膜层分别降低了3、2、1个数量级.同时,EIS研究也表明,PEB+MAO复合膜可以提供相对较长时间的抗蚀保护.另外,分析了PEB表面改性层的生成机理以及PEB+MAO复合膜的形成过程,并建立了物理模型.结论 PEB预处理会显著影响PEB+MAO复合膜的厚度、致密性及成分,继而明显提高纯镁的耐蚀性.该新型的复合膜制备方法有望进一步推广到镁合金上,以提高其耐蚀性和承载能力.     

镁合金表面微弧氧化-溶胶凝胶复合膜层的结构及其耐蚀性

采用微弧氧化和溶胶凝胶技术在镁合金表面制备复合涂层,该涂层过渡层为微弧氧化膜层,外层为SiO2溶胶凝胶层。通过傅里叶红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)等分析技术对复合涂层成分、组织结构以及微观形貌进行了表征,并采用电化学测试方法综合分析了该复合涂层的耐蚀性能。研究表明,该复合涂层与基体结合较好,具有良好的高温稳定性,在质量分数为3.5%的NaCl溶液中腐蚀电位明显正移,腐蚀电流密度显著降低,表现出良好的耐蚀性。     

微弧表面处理对AZ31B镁合金耐腐蚀及耐腐蚀疲劳性能的影响

采用微弧表面处理技术(微弧氧化MAO和微弧复合MCC)在AZ31B镁合金基体上制备出不同断面结构的防护涂层。通过电化学腐蚀及腐蚀疲劳测试方法,研究了MAO、MCC涂层的电化学腐蚀及腐蚀疲劳性能。结果表明,生长10 min的MAO涂层具有较好的耐电化学腐蚀性能。MAO涂层表面存在微孔和微裂纹,在应力条件下微孔和微裂纹作为疲劳断裂的裂纹萌生点,可加速裂纹的萌生与扩展,使其腐蚀疲劳寿命相较AZ31B合金基体降低了55%。而具有MCC涂层的AZ31B合金试样腐蚀疲劳极限为(64.0±5.4) MPa,比AZ31B合金基体提高了59%。在低应力载荷下(＜80 MPa),微弧复合涂层试样的腐蚀疲劳强度得到明显提高。     

C3H8O3含量对AZ91D镁合金微弧氧化过程及膜层特性的影响

在含有不同C₃H₈O₃含量的硅铝复合电解液中,利用交流脉冲电源在AZ91D镁合金基体上制备了一系列微弧氧化膜。利用SEM和膜层测厚仪分别研究了陶瓷膜层的微观形貌特征及厚度,采用全浸泡实验和电化学阻抗谱测试了膜层在3.5%NaCl中性溶液中的耐蚀性能。结果表明,微弧氧化过程中的起弧电压和终止电压均随C₃H₈O₃含量的增加而呈上升的变化趋势。随着C₃H₈O₃含量的增加,膜层耐蚀性先提高后降低,而膜厚变化幅度不大。膜层的耐蚀性主要取决于内部致密层,当C₃H₈O₃含量为5 mL/L时,膜层相对较致密,因而表现出良好的耐蚀性能。     

镁合金微弧氧化复合膜研究进展

微弧氧化（MAO）表面处理技术常用于改善镁合金的特定性能,但MAO膜容易产生微孔和微裂纹从而降低镁合金的耐蚀性。为了提高镁合金微弧氧化膜的使用寿命,主要综述了国内外MAO工艺过程调节措施和MAO膜后处理技术的最新研究进展,重点介绍了近年来国内外镁合金MAO复合膜的研究热点。着重介绍了通过工艺过程调节提高镁合金MAO膜长期保护性能的几项措施：通过电参数和电源类型调节协同电解液成分调整提高MAO膜耐蚀性;通过加入电解液添加剂提高MAO电解液稳定性和电导率;利用具有自封孔作用的添加剂可以参与成膜的特点提高MAO膜致密性;通过复合工艺在MAO膜传统封孔后进一步封闭孔隙。此外,详细介绍了包括疏水涂层、化学镀、类金刚石涂层、生物膜涂层等复合膜工艺的研究进展,强调了复合膜不仅耐蚀性高而且具有功能化应用前景：超疏水复合膜对镁基底具有主动的腐蚀保护作用,超疏水膜协同MAO膜可以提高表面的疏水性;镀镍层致密无微孔且与MAO膜交错咬合能够改善镁MAO膜的导电性和耐蚀性;MAO涂层代替金属缓冲层能够提高类金刚石涂层和基体界面结合强度;生物复合涂层不仅耐蚀性高还具有促进细胞增殖和分化生物活性的作用。最后,基于镁...     

不同镁合金支架材料MAO/PLLA复合膜研究

两种系列的镁合金WE42与AM20微弧氧化(MAO)后用浸渍法对微弧氧化膜进行聚乳酸(PLLA)封孔处理制备复合涂层,通过扫描电镜(SEM)分析微弧氧化膜及聚乳酸封孔膜的表面形貌及结构,X射线衍射(XRD)分析微弧氧化膜的主要成分为MgSiO3和SiO2,通过腐蚀失重测定试样的失重率.在37℃的hank's模拟体液中测...     

Corrosion resistance of micro-arc oxidized ceramic coating on cast hypereutectic alloy

The corrosion resistance of the micro-arc oxidation (MAO) ceramic coating on a cast Al-13Si-5Cu alloy was investigated using various electrochemical methods including electrochemical impedance spectroscopy (EIS) and polarization curves. Microstructures of MAO ceramic coating were studied by SEM, and the influence of microscopic patterns on corrosion resistance was analyzed. The corrosion resistance of the aluminum alloy can be improved significantly by MAO process owing to increasing impedance and corrosion potential and decreasing corrosion current, and the ceramic coatings are composed of loose layer, compact layer and transition layer, which improve the corrosion resistance. The corrosin resistance is determined by the thickness of the compact layer and is not proportional to the total thickness of MAO, though the latter is one of the important factors influencing the corrosin resistance.     

加压幅度对AZ91D镁合金微弧氧化膜的影响

研究了硅酸盐体系中加压幅度对AZ91D镁合金微弧氧化膜层结构及耐磨、耐蚀性能的影响.结果表明:随着加压幅度的增大,微弧氧化膜层的厚度、孔隙度和结合力都呈先增大后减小的趋势,且都在加压幅度为20 V时出现了最大值;粗糙度随着加压幅度的增大而增大.当加压幅度不小于25 V时微弧氧化膜层耐蚀能力强.     

Influence of substrate composition on the formation of phytic acid conversion coatings

In this paper, the formation and corrosion resistance of the phytic acid conversion coatings on Mg, Al, and AZ91D magnesium alloy were contrastively investigated using scanning electronic microscopy (SEM), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR), electronic probe microscopic analyzer (EPMA), electronic balance, and electrochemical methods. The influence of phytic acid conversion coating as a middle layer on the properties of the paint on magnesium alloys was also investigated. The results show that the formation process of the conversion coatings is evidently influenced by the compositions of the substrate. The coating on pure aluminum is thinner and compacter than that on pure magnesium and the coating formed on α phase in AZ91D magnesium alloy is thinner but denser than that on β phase. The phytic acid conversion coatings formed on Mg, Al, and AZ91D magnesium alloy can all increase their corrosion resistance. The active functional groups of hydroxyl and phosphate radical are rich in the conversion coatings, which can improve the bonding between the organic paint and magnesium alloy and then improve their corrosion resistance.     

AZ91D镁合金微弧氧化电参数对其耐蚀性的影响

在铝酸盐体系中对AZ91D镁合金进行微弧氧化处理。利用田口式实验设计法探讨微弧氧化过程电参数对膜层耐蚀性的影响,确定了最佳工艺参数为:电压180V,氧化时间30min,频率50Hz,占空比30%。用交流阻抗分析膜层的耐腐蚀性能,结果表明:最佳工艺条件下所制备微弧氧化,膜层电阻比镁合金基体提高了2个数量级,耐蚀性有所增强。     

Corrosion resistance and molecular dynamics behavior of the MAO/SAM composite coatings on magnesium alloy

To improve corrosion resistance of magnesium alloy AZ91D, y-Mercaptopropyltrimethoxysilane (MPTS) was assembled on the surface of micro-arc oxidation (MAO) treated magnesium alloy by self-assembly membrane (SAM) technique. The surface morphology and chemical components of the MAO/SAM composite coatings were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The corrosion resistance of samples was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy and total immersion tests in a 3.5 wt % NaCl solution. The measured EIS data were simulated by an equivalent circuit. Also the molecular dynamic simulation was used to study the adsorption behavior at the molecular level. The results showed that the surface of magnesium alloy was well covered by the MAO/SAM composite coatings with a better corrosion resistance. Chemical adsorption was formed between the organic molecules and the surface of the MAO coating. The approach presented here afforded an effective alternative for surface modification of magnesium-based materials to meet the many aspects of the application requirements.     

Corrosion characterization of microarc oxidation coatings formed on Mg–7Li alloy

Ceramic coatings with thickness of 27 µm were fabricated on Mg–7Li alloy in Na₂SiO₃–C₆H₁₈O₂₄P₆ solution by microarc oxidation (MAO). The morphology and phase composition of MAO coatings were characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The corrosion behavior of the bare and MAO coated Mg–7Li alloy was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results showed that the MAO coatings were composed of MgO, Li₂O, and Mg₂SiO₄, and there existed some micropores on the coating surface with a diameter of 3–20 µm. The corrosion potential (E_corr) and corrosion current density (I_corr) of the MAO coated alloy were about ?1.4761 V and 7.204 × 10^?7 A/cm², respectively. The E_corr of the MAO coated alloy increased by 109.6 mV and its I_corr decreased by three orders compared with that of the bare Mg–7Li alloy. The EIS plots indicated that the impedance of the MAO coated alloy was 15 times higher than that of the bare alloy. The fitting parameters showed that the resistance of the MAO coatings was far greater than that of the bare alloy. The dense intermediate layer and the transition layer of the MAO coatings acted as a barrier to hinder the proceeding of solution permeation, remarkably improving the corrosion resistance of the Mg–7Li alloy.     

Statistical Process Control

Abstract

In order to improve the corrosion resistance provided by a micro-arc oxidation (MAO) coating on AZ31 magnesium alloy, a polypropylene film was prepared on its surface. Scanning electron microscopy, energy dispersive X-ray analysis and Fourier transform infrared spectroscopy were used to characterise the surfaces of the coatings. The corrosion protective performance of the coatings was evaluated by potentiodynamic polarisation curves, electrochemical impedance spectroscopy and immersion testing. The results show that the microdefects of the MAO coating can be filled by PP and the corrosion resistance of the AZ31 magnesium alloy is improved greatly.     

Characterization of the corrosion performances of as-cast Mg–Al and Mg–Zn magnesium alloys with microarc oxidation coatings

In the present study, corrosion-protective microarc oxidation (MAO) coatings were prepared on AZ31B, AZ80, and ZK60 cast magnesium alloy substrates in an alkaline silicate electrolyte. The corrosion performances of the uncoated and MAO-coated alloys were investigated using electrochemical and salt spray chamber corrosion tests. The microstructure characterization and experimental results show that among the three alloys studied, the ZK60 Mg alloy exhibited the best and AZ31B the least corrosion resistance under the salt spray conditions. The MAO coating provided robust corrosion protection of the Mg substrates and resulted in a significant decrease in the corrosion rate of the alloys by 3–4 orders of magnitude. The MAO coating on ZK60 alloy showed better corrosion protectiveness than that on the AZ series alloys due to the incorporation of different alloying elements in the coating, especially the Zn and Al elements, which are from the Mg substrate. The corrosion performances and mechanisms of the uncoated and MAO-coated Mg alloys are interpreted in terms of the microstructure and phase/chemical compositions of both the substrates and coatings.     

镁合金表面冷喷涂铝涂层的热处理研究

使用冷喷涂方法在铸态AZ91D镁合金基体上沉积了纯Al涂层,所得涂层组织致密,厚度均匀,与基体结合良好,孔隙率小于1%.随后用机械减薄的方法使Al涂层的厚度减薄到135 μm,对减薄后的试样在真空加热炉中分别进行了400℃×20 h和400℃×40 h的热处理.结果显示随着保温时间的延长,Al涂层全部转化为较高硬度和较...     

Effects of increase extent of voltage on wear and corrosion resistance of micro-arc oxidation coatings on AZ91D alloy

The effects of increase extent of voltage on the wear resistance and corrosion resistance of micro-arc oxidation(MAO) coatings on AZ91D magnesium alloy were investigated in silicate electrolyte.The results show that with increasing extent of voltage, both of the thickness and bonding force of MAO coatings first increase,and then decrease.These parameters are all up to their maximum values when the increase extent of voltage is 20 V.The roughness of the coatings always increases.The coating has the best c...     

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.