氟硅比对AM60B镁合金微弧氧化膜微观结构及耐蚀性的影响

通过改变硅酸盐体系电解液中KF和Na_2Si O_3的浓度,定量分析氟化钾与硅酸钠浓度配比(简称氟硅比)对AM60B镁合金微弧氧化膜层微观结构及耐蚀性的影响。结果表明:主盐Na_2Si O_3在微弧氧化成膜中必不可少。当电解液中含有KF时(氟硅比大于0),随着氟硅比的增大,成膜反应加剧,膜层表面的孔隙率和表面大孔(3μm)数目增加,膜厚增加,且由于KF在电解液中的存在,会生成新物相Mg F_2,促进物相Mg_2Si O_4的形成,这些物相有利于提高膜层的耐蚀性。此外,KF与Na_2Si O_3二者在成膜反应中的竞争与协同作用因氟硅比的变化而变化,致使膜层的微观结构与物相含量随之改变,从而影响膜层的耐蚀性。本研究中,当氟硅比为0.5(KF:Na_2Si O_3=7.5:15)时,由于KF与Na_2Si O_3间良好的协同作用,形成的膜层厚度较大,致密性较好,缺陷较少,此时膜层兼备厚度大与耐蚀性优的特性,是最佳的氟硅比。     

NaOH对铝合金微弧氧化膜特性的影响

在Na₂SiO₃电解液体系下,对ZAlSi12Cu2Mg1微弧氧化膜的形成进行研究,通过改变NaOH的含量,研究了其对电解液的电导率、微弧氧化的临界起弧电压、膜层特性及微观形貌的影响。并测定了氧化膜的相组成。结果表明：NaOH含量从1.0 g/L到3.0 g/L变化时,电解液的电导率由14.00 ms/cm几乎呈线性增大到26.28 ms/cm,正向临界起弧电压由360 V呈线性降低下降到290 V;含量从1.0 g/L增大到2.5 g/L时,膜厚从92 μm迅速增加到125 μm。含量超过2.5 g/L,膜厚减小,致密层所占比例下降。XRD分析表明：氧化膜层中主要由莫来石、SiO₂和α-Al₂O₃、γ-Al₂O₃和WO₃相。     

6063铝合金中性无铬转化膜制备及膜层性能分析

目的 提高铝合金微小器件的耐蚀性,开发一种条件温和可控的转化膜成膜工艺。方法 采用中性无铬转化工艺,在6063铝合金表面制备转化膜。通过研究NaF、NH₄HF₂、KMnO₄、十二烷基硫酸钠(SDS)和没食子酸等几种添加剂对转化膜外观与耐蚀性的影响,确定NH₄HF₂为最佳添加剂。采用电化学方法分析膜层的耐蚀性,用SEM和EDS分析表面形貌及元素组成,并采用XRD和XPS表征膜层晶态结构和化合物组成。基于检测结果,简要分析转化膜的成膜过程。结果 最终得到了中性转化处理的最佳成膜工艺为EDTA-2Na 8.0 g/L,单宁酸1.0 g/L,Na₂WO₄ 6.0 g/L,H2Zr F6 4.0 g/L,NH₄HF₂ 3.0 g/L,p H 6.6,成膜温度为30℃,成膜时间为15 min。该工艺所制备的转化膜外观致密均匀,颜色为浅黄色。电化学测试结果表明,转化膜具有良好耐蚀性,自腐蚀电流密度由基体铝...     

基于配方均匀试验优化微弧氧化电解液浓度配比

目的 研究电解液中各电解质不同浓度配比下微弧氧化膜层的制备、微观结构及耐蚀性能,以确定最优配方.方法 基于配方均匀试验方法,在硅酸盐系电解液中对AM60B镁合金进行微弧氧化处理.引入微弧氧化反应的可行性和微弧氧化膜层的成膜性两个试验指标,分别评判本研究中某电解液配方是否具有实际应用价值,以及评价在某个电解液配方下所制得膜层的合格程度.利用涡流测厚仪、扫描电镜(SEM)、X射线衍射(XRD)、电子探针(EPMA)、硝酸点滴实验以及电化学实验等方法,分别表征膜层的厚度、微观结构、物相组成、元素成分及耐蚀性能.结果 当电解液中NaOH的质量浓度小于10 g/L时,方能获得表观完整且色泽均匀的微弧氧化膜层.当NaOH和KF的浓度配比接近,且两者之和约为Na2SiO3所占配比时,即Na2SiO3为19.24 g/L、NaOH为8.80 g/L、KF为11.96 g/L时,膜层中孔径的尺寸小,缺陷少,致密度最高,此时膜层的耐蚀性最好,与基体相比,该膜层的硝酸点滴耐蚀性提高了39倍,电化学耐蚀性提高了3个数量级.膜层主要由MgO、Mg2SiO4及少量的MgF2、MgAl2O4组成,但含量有差别.结论 实验设计方法的选择是保证本研究结果有效性的核心和关键.电解液中NaOH的浓度高低是决定某电解液配方是否具有实用价值的首要因素.只有Na2SiO3、NaOH和KF三者间具备适当的配比时,才能降低膜层中的微孔尺寸,减少微裂纹,提高其致密度,并能够在膜层中沉积更多的优质物相,这些是增强膜层耐蚀性的前提和保障.     

铝合金微弧氧化膜层耐蚀性研究现状

铝合金微弧氧化技术是提高其表面性能的一项重要技术,微弧氧化膜层的耐蚀性直接影响其适用范围。较系统地总结了铝合金微弧氧化中影响膜层耐蚀性的因素,包括电解液和电参数2大部分。电解液主要由主盐、添加剂及NaOH等组分组成;电参数主要是电流、电压、占空比及频率等因素。提出了几种提高微弧氧化膜层耐蚀性的后处理方法,探讨了各因素对膜层耐蚀性影响的作用机理。     

电解液成分对等离子体电解氧化TC4合金腐蚀行为和摩擦学性能的影响（英文）

在TC4合金表面制备4种典型等离子体电解氧化(PEO)涂层,研究电解质组成对PEO涂层腐蚀行为和摩擦学性能的影响。结果表明,PEO涂层的腐蚀行为和摩擦学性能与电解质成分密切相关。在含NaH₂PO₂的电解液中制备的PEO涂层由于内氧化膜较致密而具有最好的耐蚀性能,而在含NaAlO₂的电解液中制备的PEO涂层由于含有Al₂O₃而具有最好的摩擦学性能。为制备具有良好耐蚀性和耐磨性的PEO涂层,以NaH₂PO₂和NaAlO₂为电解液主要成分制备了复合PEO涂层。     

氟化钾对AZ91D镁合金微弧氧化膜的生长及微观结构的影响

通过在NaOH和Na_2SiO_3组成的基础电解液中,分别不加及加入KF,对AZ91D镁合金进行微弧氧化处理,研究了KF的有无对镁合金微弧氧化膜的生长、微观结构及耐蚀性能的影响。结果表明:与不加KF相比,加入KF后,试样的起弧电压明显降低,击穿变得剧烈,试样表面火花较大,膜层的生长速率明显提高,膜层厚度显著增大,表面孔隙率稍有增大,但表面微孔数量减少。KF的加入有利于MgF_2、MgAl_2O_4的生成,与同样来自电解液的Si、O两元素相比,F~-更易被基体中的Mg所吸附,也容易通过已成膜层迁移到膜层的内部。电解液中含有KF时,膜层厚度显著增大,MgAl_2O_4物相含量增加,并生成新物相MgF_2,这些都有利于膜层耐蚀性的提高。     

NaOH对铝合金A356微弧氧化膜形成及其耐蚀性的影响

电解液采用NaOH-Na2SiO3体系,对铝合金A356进行徼弧氧化.通过改变NaOH浓度研究起弧电压、成膜速率的变化规律以及NaOH浓度的变化对膜层耐蚀性的影响.试验结果表明,随着NaOH浓度从1 g/L到5g/L逐渐增加,起弧电压从350 V降低到230 V,成膜速率在NaOH浓度为4 g/L时出现最大值0.8 μm/min;耐蚀性从19 min提高到25 min;综合各种因素,理想膜层的NaOH最佳浓度为4 g/L.     

硅酸盐体系电解液中添加Na2WO4对LY12铝合金陶瓷膜性能的影响

通过SEM、XRD、硬度试验、电化学腐蚀试验研究了在硅酸盐体系电解液中加入不同浓度的Na₂WO₄对LY12铝合金微弧氧化陶瓷膜表面形貌及性能的影响。结果表明,添加Na₂WO₄改变了膜层的微观结构,使微弧氧化膜层硬度增加,表面平滑,呈现出小而少的孔洞结构,且表面堆积少量形状不规则的白色质点;随着Na₂WO₄添加量的增加,膜层的硬度值呈现先增加后降低的趋势,当Na₂WO₄含量为4 g/L时,膜层达到最高硬度440.3 HV0.3,较基体(硬度值约168 HV0.3)提升了272.3 HV0.3;XRD分析证明W元素参与了微弧氧化过程,并生成W的氧化物WO₃,陶瓷层物相主要由α-Al₂O₃和γ-Al₂O₃以及WO₃组成;电化学极化曲线分析结果表明添加剂Na₂WO₄有效地提高了膜层的耐腐蚀性能,耐腐蚀性能最好的添加量为 1 g/L,此时自腐蚀电位为-532.0 mV,腐蚀电流为0.011 μA。Na₂WO₄的添加可有效改善陶瓷膜层的表面形貌及性能。综合考虑膜层的性能,添加剂Na₂WO₄的最佳添加量为 4 g/L。     

脉冲频率及占空比对Ti6Al4V合金微弧氧化膜层微观结构及性能的影响

研究了脉冲频率及占空比对Ti6Al4V合金在Na₂SiO₃-Na(PO₄)₆电解液体系中制备的微弧氧化膜层微观结构及其性能的影响,采用扫描电镜、能谱仪、X射线衍射仪、涂层厚度仪、激光共聚焦显微镜及显微硬度计对膜层形貌、元素分布、相组成、厚度、粗糙度及硬度进行测试表征。结果表明,Ti6Al4V合金微弧氧化膜层主要元素组成为Ti、O、Si等,物相组成主要为Rutile-TiO₂、Anatase-TiO₂及非晶相SiO₂,随脉冲频率增加,膜层中Anatase衍射峰强度先降低后增加,Rutile呈相反趋势;随脉冲占空比增大,Anatase衍射峰强度逐渐减小,而Rutile衍射峰强度逐渐增加。膜层表面均匀分布微米级孔洞,脉冲频率对膜层微观形貌及粗糙度影响较小,膜层厚度先增大后减小;随占空比增加,膜层快速增厚,但表面逐渐出现微裂纹及局部烧蚀等缺陷,膜层粗糙度大幅增加,600 Hz、20%占空比时膜层厚度达45.46μm,粗糙度R_a     

用优化的双电解液制备AZ91D镁合金微弧氧化膜(英文)

在含有Na2SiO3、NaAlO2、Na2B4O7、NaOH、C3H8O3和C6H5Na3O7的电解液中,采用交流脉冲电源对AZ91D镁合金进行微弧氧化处理。利用SEM、膜层测厚仪、EDS和XRD分别研究膜层的表面和截面微观形貌、厚度、成分及相结构。利用交流阻抗和动电位极化曲线试验测量膜层在3.5%NaCl中性溶液中的耐蚀性能。结果表明,正交试验得到的双电解液成分为15g/LNa2SiO3、9g/LNaAlO2、2g/LNa2B4O7、3g/LNaOH、5mL/LC3H8O3和7g/LC6H5Na3O7。经过微弧氧化处理而得到的膜层较致密,其腐蚀电流密度较镁合金基体的降低了2个数量级,自腐蚀电位提高了近73mV。EIS结果认为膜层的耐蚀性取决于内部致密层。微弧氧化膜主要组成元素为Mg、Al、O和Si,主要组成相为MgO、Mg2SiO4和MgAl2O4。     

Plasma anodized ZE41 magnesium alloy sealed with hybrid epoxy-silane coating

Anodic coatings on magnesium ZE41 alloy were formed by DC plasma electrolytic oxidation (PEO) in spark regime in solution composed of NaOH, Na₂SiO₃ and KF. The positive effect of poly(ethylene oxide) addition into the anodizing electrolyte on PEO process, anodic film porosity and its protective performance was described. Anodic films were sealed with hybrid epoxy-silane formulation. The corrosion behavior of the coated ZE41 was studied through electrochemical impedance spectroscopy (EIS) in 0.6 M NaCl solution. Resulting duplex PEO/epoxy-silane coating provides good protective performance without significant signs of corrosion during 1 month of immersion test.     

The effect of phosphate on MAO of AZ91D magnesium using AC power source

A rapid and convenient anodization technology with AC power source to obtain the MAO films formed on magnesium alloy AZ91D in phosphate bath (base electrolyte + Na₃PO₄) with or without aluminate and silicate was studied. The corrosion resistance of the anodic films was studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques and the microstructure and composition of films were examined by SEM and XRD. The results show that Na₃PO₄can promote the occurrence of sparking during the MAO process, while abundant heat generated by sparking might enhance the formation of the glassy phase of the compound when the electrolyte contains the additives of NaAlO₂and Na₂SiO₃simultaneously. The optimized MAO film is ivory‐white smooth by naked eye, while presents porous and microcracks in microscopic scale. The anodic film formed in the alkaline solution with optimized parameters possesses superior corrosion resistance by electrochemical test. The XRD pattern shows that the components of the anodized film consist of MgO, MgAlO₂, and MgSiO₃. No oxide crystal with P element can be found.     

几种添加剂作用的微弧氧化膜表面结构及防腐性能

为定性比较添加剂对涂层防腐性能的作用,通过恒压微弧氧化(MAO)方法在AZ31B镁合金表面制备氧化陶瓷膜,采用扫描电子显微技术(SEM)、中性盐雾试验(NSS)等手段,考察了KOH及添加剂Na_2B_4O_7、C_6H_5Na_3O_7和EDTA-2Na浓度(质量浓度)对MAO膜表面形貌、防腐性能、粗糙度和厚度的影响。结果表明:单一组分Na_2SiO_3电解液因较高起弧电压而未能在260 V恒压条件下获得具有"火山口"形貌特征的MAO膜,其防腐性能较差。适量KOH因较低微弧等离子体诱发电压和OH-较快的放电作用,提高了涂层的防腐性能。在优化的Na_2SiO_3-KOH体系中引入10~15 g/L Na_2B_4O_7,因其特殊的形成过程及其"火山喷射状"的微结构,且获得的MAO膜具有自封孔结构,提高了其对镁合金的点腐蚀防护性能。C_6H_5Na_3O_7和EDTA-2Na具有抑弧效应,获得的MAO膜表面微孔分布均匀,但降低了MAO膜的厚度、粗糙度以及防腐性能。     

Effect of electrolyte on mechanical properties of AZ31B Mg alloy in electrolytic plasma processing

Coatings on Mg alloys were prepared using NaOH + Na₂SiO₃ as basic electrolyte containing electrolyte of Na₂SiF₆ or NaF. EPP treatment was carried out on AZ31 Mg alloys matrix under a hybrid voltage of AC of 200 V combined with DC of 260 V for 30 min. Structural and morphological analyses of ceramic coatings were analyzed by XRD and SEM. Wear and hardness of coatings were measured by pin-on disk test and Vickers hardness test. The coatings formed in Na₂SiF₆ and NaF electrolytes were mainly composed of MgO and Mg₂SiO₄. The measured micro-hardness of coating formed in Na₂SiF₆ electrolyte was found to be over HV 1100, while, coating formed in NaF electrolyte possessed micro-hardness of HV ～900. These results show that the mechanical properties of AZ31B Mg alloys can be enhanced by the proper selection of electrolyte agent.     

Formation of ceramic alumina nanocomposite coatings on aluminium for enhanced corrosion resistance

Plasma electrolytic oxidation (PEO) has been considered as a novel technique to form ceramic nanocomposite coatings on aluminium and magnesium alloys for corrosion protection. However, a systematic study of the effect of process parameters on the properties of the coatings has not been well demonstrated. In the present study, aluminium was treated by PEO at various treatment time, current density, temperature and concentration of NaOH and Na₂SiO₃ and their effect on the surface properties of the coatings has been investigated systematically. It was found that the temperature and treatment time were the major factors affecting the thickness and growth. The coatings mainly consisted of α-alumina, γ-alumina and Al₂(SiO₃)₃. The ceramic composite coatings with best corrosion resistance were obtained at higher current density, lower temperature, moderate treatment time and optimum concentration of NaOH and Na₂SiO₃. The crystallite size of the composite coating was found to be in nanometer scale (9–131 nm).     

Wear and corrosion resistant coatings on surface of cast A356 aluminum alloy by plasma electrolytic oxidation in moderately concentrated aluminate electrolytes

Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO₂ solutions and a silicate electrolyte (for comparison) were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC (tungsten carbide) ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO₂ solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of ～4.5×10^?7 mm³/(N·m). A low corrosion current density of ～8.81×10^?9 A/cm² was also recorded. Despite low α-Al₂O₃ content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.     

Effect of SiO2:Na2O molar ratio of sodium silicate on the corrosion resistance of silicate conversion coatings

Passivation treatment by sodium silicate solution is considered as an alternative to chromium chemical conversion treatment to improve the corrosion resistance of hot-dip galvanized (HDG) steels. In this paper, a transparent silicate coating was formed on the surface of HDG steel by immersing in sodium silicate solution with SiO₂:Na₂O molar ratio in the range from 1.00 to 4.00. The parameter about the SiO₂:Na₂O molar ratio of silicate solution has been discussed using corrosion resistance and surface morphology. Tafel polarization, electrochemical impedance spectroscopy (EIS) measurements and neutral salt spray (NSS) test show that silicate coatings increase the corrosion resistance of HDG steels. From the results obtained, it is deduced that the optimum SiO₂:Na₂O molar ratio is 3.50. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD), and reflectance absorption infrared spectroscopy (RA-IR) show that there are no obvious differences of the chemical composition and structure in various silicate coatings. The silicate coatings mainly consist of zinc oxides/hydroxides, zinc silicate and SiO₂. However, atomic force microscopy (AFM) images reveal that the surface of silicate coatings with a molar ratio of 3.50 is more compact and uniform than other silicate coatings.