硅酸钠模数对热镀锌件转化膜耐蚀性的影响

为了确立单独硅酸钠形成膜与硅酸钠模数的关系,将热浸镀锌钢板浸入硅酸钠溶液中,在其表面获得了连续透明的保护膜.采用俄歇电子能谱(AES)进行剥层分析,通过塔菲尔极化、电化学阻抗谱(EIS)和中性盐雾试验(NSS)研究了膜层的形貌组成及其耐蚀性能.结果表明:以硅酸钠模数(SiO2/Na2O摩尔比)为1.00～4.00的硅酸钠溶液(含50 g/L SiO2)处理锌层表面形成的化学转化膜,膜层主要含Si,O,Zn元素,其耐蚀性有所提高;当模数≤3.50时,膜的耐蚀性随模数的增大而显著提高,模数为3.50时膜具有最好的耐腐蚀性能.     

6063铝合金表面钛/锆/钼转化膜的制备及自愈性

采用化学转化处理法在6063铝合金表面制备获得淡黄色的钛/锆/钼转化膜,通过浸泡法并借助电化学工作站考察了钛/锆/钼转化膜的耐蚀性,采用划痕法结合扫描电子显微镜(SEM)研究了钛/锆/钼转化膜的自愈性。转化液的组成为:2 g/L H_2TiF_6,2 g/L H_2ZrF_6,2 g/L有机酸着色剂,3 g/L Na_2MoO_4。结果表明,在pH=3.0、温度为35℃、时间为5 min的工艺条件下能够在6063铝合金表面获得淡黄色、致密且耐蚀性良好的膜层,膜层微观表面均匀分布着白色颗粒和裂纹。人工划痕的钛/锆/钼转化膜在3.5%NaCl盐雾氛围中随着浸泡时间的延长划痕逐渐愈合,形成新的膜层,这表明制得的膜层具有自愈性。当在中性盐雾中的腐蚀时间超过5 d后,划痕处附近膜层中的氧化剂不断被消耗,迁移至划痕处发生络合的物质逐渐减少,膜层自愈性能退化,膜层被腐蚀。     

二氧化硅粉体粒度对硅酸盐转化膜制备的影响

用微米和纳米粒度的SiO2粉体分别配制SiO2质量分数为5%、模数(SiO2/Na2O摩尔比)为3.50的硅酸钠溶液,并用之浸泡热镀锌钢制备了硅酸盐钝化膜。用X射线衍射(XRD)、反射红外光谱(RA-IR)分析二氧化硅粉体,用透射红外光谱(FT-IR)和核磁共振(NMR)分析硅酸钠溶液的结构,用原子力显微镜(AFM)、电化学阻抗谱(EIS)分析转化膜的结构。结果表明:与微米级二氧化硅相比,纳米级二氧化硅含有Si-OH键较多,用它配制的硅酸钠溶液中硅酸负离子的聚合程度较低,成膜过程脱水量较多而生成微观孔隙较多的转化膜。     

硅酸钠溶液的模数对Zn-5%Al镀层上硅酸盐转化膜的影响

使用扫描电子显微镜(SEM)和能谱仪(EDS)、傅里叶变换红外吸收光谱(FT-IR)、X射线光电子能谱(XPS)等手段研究了经不同模数(SiO_2:Na_2O=2.0,3.0,3.5,4.0,4.5)硅酸钠溶液处理的热浸Zn-5%Al镀层表面硅酸盐转化膜的形貌和结构,并根据电化学交流阻抗(EIS)研究了膜层的耐蚀性。结果表明:与未处理的热浸镀Zn-5%Al试样相比,钝化后的试样耐蚀性有较大的提高,且模数为4.0时的膜层透明,表面均匀平整,膜层阻抗达到204.22 kΩ·cm~2,耐蚀性最高;而模数为2.0时的膜层表面有较多的裂纹,耐蚀性最低。硅酸盐转化膜主要由硅酸锌、铝硅酸盐和二氧化硅、铝氧化物/氢氧化物、锌氧化物/氢氧化物组成,根据膜层分析对Zn-5%Al镀层硅酸盐转化膜的成膜机理进行了讨论。     

镁合金高压阳极氧化工艺研究

为开发耐蚀性能优良的镁合金阳极氧化工艺,用正交试验对AZ91D镁合金高压阳极氧化成膜工艺进行了研究,并利用扫描电镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、全浸腐蚀试验和极化曲线等分别研究了镁合金阳极氧化膜层的表面形貌、相成分、元素成分、价态和膜层的耐蚀性等.获得了AZ91D镁合金高压阳极氧化的最佳成膜工艺参数为:10 g/L KOH,5 g/L NaF,5 g/L Na2SiO3,0.5 g/L Na2B4O7, 100 mL/L乙二醇, 75 mL/L丙三醇, 50 mL/L组分G;电流密度 8.9 mA/cm2,氧化时间 30 min.在最佳工艺下所得阳极氧化膜层呈多孔结构,孔洞分布比较均匀,孔径尺寸约为1～2 μm;氧化膜层主要由Al2SiO5、MgF2和MgAl2O4相组成;氧化膜层的耐蚀性明显优于传统含铬DOW17工艺所得氧化膜层的耐蚀性.     

炭/炭复合材料硼硅酸盐玻璃涂层制备及性能研究

系统研究了SiO2与B2O3之比、高熔点添加剂种类(包括MoSi2,Y2O3,SiC)及含量对硼硅酸盐(SAB)玻璃涂层高温稳定性、高温流动性的影响规律和最佳工艺参数组合,采用涂刷法在带有疏松结构的SiC内涂层炭/炭(C/C)复合材料表面制备了高温稳定性和流动性良好的硼硅酸盐玻璃外涂层,并测试了带有不同SiC/硼硅酸盐玻璃复合涂层C/C复合材料试样在1500℃静态空气中的抗氧化性能.结果表明:采用SiO2,B2O3摩尔比为4∶1时所得硼硅酸盐玻璃具有相对较高的高温流动性和高温稳定性;与添加Y2O3,SiC相比,在上述硼硅酸盐玻璃中添加MoSi2可以较大幅度提高所得玻璃涂层对C/C基体的氧化保护性能,并且当硼硅酸盐玻璃外涂层中硼硅酸盐与MoSi2的质量比为4∶1时,所得硼硅酸盐玻璃外涂层对SiC-C/C表现出较好的氧化保护能力,氧化17h后涂层C/C试样的失重仅为4.31%.     

Mg-Li合金微弧氧化陶瓷膜的制备及其耐蚀性能

通过三种优化工艺体系在Mg-5%Li合金表面上生长陶瓷膜层,分析了膜层的厚度、显微结构、相组成和耐蚀性.结果表明,三种膜层都含有MgO相,微弧氧化试样的耐蚀性能都明最提高.使用Na3PO4体系制备的膜层含有MgF2,膜层最厚、表面有大量裂纹;使用Na2SiO3体系制备的膜层含有橄榄石型Mg2SiO4,耐点蚀性能最好;使用Na2SiO3-Na3PO4体系制备的膜层含有MgSiO3,致密性最好,膜层酎均匀腐蚀性能最好.     

电解液对铝微弧氧化膜相结构及性能的影响

在Na2SiO3和NaAlO2两种电解液体系中用微孤氧化法制得铝氧化膜.采用扫描电镜、X射线衍射和电化学分析等对铝氧化陶瓷膜的表面形貌、相结构及耐蚀性进行了分析研究,结果表明:两种体系下生成的氧化膜均由α-Al2O3和γ-Al2O3相组成,Na2SiO3体系下形成的氧化膜中α-Al2O3相的含量更多;陶瓷膜表面有大量的类似火山口的等离子放电产物和明显的放电通道,Na2SiO3电解液中形成的氧化膜放电通道闭合得较好;由恒电位极化可以看出微弧氧化陶瓷膜具有良好的耐蚀性,Na2SiO3体系下生成的氧化膜耐腐蚀性能更好一些.     

硫代乙酰胺对镀锌钢表面铈盐转化膜耐蚀改性的影响

为了提高镀锌钢表面铈盐转化膜的耐蚀性能,添加硫代乙酰胺对其进行改性,采用扫描电镜(SEM)、能谱(EDS)、中性盐雾(NSS)和极化曲线对铈盐转化膜改性前后的形貌结构、成分和耐蚀性能进行分析测试。结果表明:硫代乙酰胺的加入大大增加了铈盐转化膜的反应时间和膜层厚度以及转化膜有效耐蚀成分O,P,Ce的含量,使得试片耐中性盐雾腐蚀时间由改性前的24 h提高到改性后的288 h,铈盐转化膜的耐蚀性显著提高。     

Lu-Si-O体系在高温水蒸气环境中的腐蚀行为

采用溶胶-凝胶法制得三种镥硅酸盐体系粉体材料.以氧化物的摩尔比来表示此三种粉体,分别为:Lu2O3.SiO2、Lu2O3.2SiO2和Lu2O3.2.26SiO2.在1400℃、50%H2O-50%O2静态常压气氛下,研究了它们的耐水蒸气腐蚀性能.以单位面积重量变化率表征材料的耐水蒸气腐蚀性能,结合X射线衍射(XRD)、傅里叶红外光谱(FTIR)和扫描电镜能谱分析(SEM-EDS)等分析手段,揭示了镥硅酸盐体系在高温水蒸气环境中的腐蚀机制和反应机理.结果表明:三种原始粉体主要物相依次为:Lu2SiO5+Lu2Si2O7、Lu2Si2O7+SiO2和Lu2Si2O7+SiO2.在水蒸气作用下,Lu2SiO5相与Al2O3反应生成新相Lu3Al5O12,而Lu2Si2O7相并未受到水蒸气的作用而发生任何反应,表现出优异的化学稳定性.     

Improving Corrosion Resistance of Friction Stir Welding Joint of 7075 Aluminum Alloy by Micro-arc Oxidation

An attempt has been made to improve the corrosion resistance of friction stir welded joints of 7075 aluminum alloys by micro-arc oxidation（MAO）, and the effects of Na2Si O3 concentration in electrolyte on the corrosion resistance of the coatings were discussed. Morphology and phase constituents of the MAO coatings produced in electrolyte with different Na2SiO3 concentrations were analyzed by scanning electron microscopy, confocal laser scanning microscopy and X-ray diffraction. Electrochemical tests were conducted to evaluate the corrosion resistance of the coatings. The results show that the corrosion resistance of the coated joints is much better than that without the ceramic coating, and the ceramic coating produced in the electrolyte with Na2SiO3 concentration 20 g/L showed better corrosion resistance than the others.     

电解液对微弧氧化陶瓷膜结构与耐蚀性的影响

在3种不同的电解液体系中,利用微弧氧化技术在AZ91D镁合金表面原位生长了陶瓷膜．通过扫描电镜、X射线衍射、电化学分析等方法研究了陶瓷膜的形貌特征、相结构及耐府蚀性能．研究表明,在相同反应条件下,不同电解液体系中生成的陶瓷膜结构和性能不同,硅酸钠体系中生成的陶瓷膜厚度大、偏铝酸钠体系中生成的陶瓷膜较薄,偏铝酸钠与硅酸钠的混合体系中生成的陶瓷膜致密、耐腐蚀性能较好．三体系中生成的陶瓷膜中都含有MgO,偏铝酸钠体系陶瓷膜中含有MgAl2O4、硅酸钠体系中含有Mg2SiO4,混合体系中则这两种物质都存在．     

镁合金表面微弧氧化-SiO2复合膜层的微观结构和耐蚀性

采用有机醇盐水解法制备SiO2溶胶,用浸溃-提拉制膜技术在AZ31B镁合金微弧氧化陶瓷层表面制备SiO2膜层,研究了镁合金表面微弧氧化-SiO2复合膜层的微观结构和耐蚀性.结果表明:SiO2溶胶进入微弧氧化陶瓷层表面的微孔并形成了SiO2膜层;由微弧氧化陶瓷层和SiO2膜层组成的复合膜层的腐蚀电位比单一陶瓷层明显提高,...     

Deposition and corrosion behavior of silicate conversion coatings on aluminum alloy 2024

Potassium silicate was deposited on AA2024 aluminum alloy as environmentally friendly conversion coatings and its corrosion behavior were examined by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surfaces techniques. Potentiodynamic polarization curves show significant decrease in corrosion current density of silicate coated aluminum in NaCl solution. The corrosion resistance was increased with increasing silicate concentration of coating baths. The results indicated that the coating applied from 3 molar silicate baths is more uniform and continuous. The X‐ray diffraction (XRD) and energy discharge spectroscopy (EDS) spectra confirm the existence of silicate film on the AA2024 surface. The coating performance was evaluated in acidic and basic NaCl solution and the results show the stability of silicate conversion coating in these solutions.     

Alkali silicate binders: effect of SiO2/Na2O ratio and alkali metal ion type on the structure and mechanical properties

The influence of SiO₂:Na₂O molar ratio and the nature of an alkali metal (Na vs. K) in commercial aqueous alkali silicate on the microstructure, textural properties, phase composition, and hydrolytic stability of an alkali silicate binder have been investigated using scanning electron microscopy, nitrogen adsorption/desorption technique, X-ray diffractometry, thermal analysis, and dissolution tests. It has been found that microstructure and textural properties of the alkali silicate binder depend both on silica to alkali molar ratio and type of alkali metal (Na vs. K). Sodium silicate binder obtained from commercial silicate solution with lower SiO₂:Na₂O molar ratio (2.2) exhibits a globular microstructure of silica xerogel with high content of micropores, whereas the binder formulated with SiO₂:Na₂O molar ratio 3.2 is characterized by more open cluster structure with lower content of micropores. It is observed that surface specific area estimated by Brunauer, Emmett, and Teller method and mesopore volume obtained by the Barrett–Joyner–Halenda method for sodium silicate binder are substantially higher than those for potassium silicate binder. The ultimate hydrolytic stability of the sodium silicate binder increases slightly with increase in the silica to alkali molar ratio within the studied range. Decreasing in SiO₂:Na₂O molar ratio and replacement of sodium silicate solution by potassium silicate solution in the corresponding filled composition lead to the improvement of mechanical properties and decrease in open porosity.     

Investigation of High Molar Ratio Potassium Solution Used in Zinc-Rich Coatings

High molar ratio potassium silicate solution used in zinc-rich water-base coatings was prepared by adding the nanosize SiO2 to the low molar ratio potassium silicate solution, and its microstructure was investigated by SEM and IR.Furthermore, the zinc-rich coatings was prepared by adding the zinc powders to this type of solution, and the properties of the coatings were evaluated. The test results show that the high molar ratio potassium silicate solution is the bonder of zinc-rich inorganic coatings with excellent property.     

Ceramic coatings of LA141 alloy formed by plasma electrolytic oxidation for corrosion protection

Superlight Mg-Li alloy is a promising structural materials in aerospace, automobile, and electronics because of its excellent properties such as low density, high ductility, superior strength-to-weight ratio, and good damping ability. The fabrication of compact plasma electrolytic oxidation coatings with excellent corrosion resistance is valuable for the widespread application of Mg-Li alloy. Here we present a ceramic coating on the surface of Mg-14Li-1Al (LA141) alloy for corrosion protection via plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte with tungstate as an additive. X-ray photoelectron spectroscopy and thin film-X-ray diffraction analysis of coatings show that the surface coating is mainly comprised of Mg(2)SiO(4), MgO and WO(3). Scanning electron microscopy observations have revealed that the dense and compact coating formed in the presence of tungstate has less structural imperfections in comparison to the control one fabricated without use of tungstate. The effect of oxidation time on the morphology and phase composition of coatings is also examined in detail.     

镁合金微弧氧化着色膜研究

镁合金在电子工业中的快速发展对装饰性能提出了更高的要求.主要研究了如何在微弧氧化的同时进行氧化着色.膜层制备选取的基材为AZ91,电解溶液由硅酸盐为主的碱性溶液组成,配方为:Na2SiO3 5～30g/L,KMnO4 1～20g/L,NaOH 1～5g/L,KF 5～8g/L,Na3 C6H5O70.5～2g/L,EDTA 0.5～2g/L.在电解液中添加着色盐KMnO4,形成了颜色各异的黄色陶瓷膜层.研究发现,膜层呈现出黄色主要是由于在膜层中生成了Mg6MnO8相,该物相在氧化膜中含量不同和分布差异将导致样品颜色深浅不同.     

激光重熔改性铝合金微弧氧化膜层的组织与性能

为了改善微弧氧化(MAO)膜层多孔疏松的组织和性能, 对其进行了激光重熔处理, 并制备了两种实验膜层: (1)选择双向电流脉冲和Na₂SiO₃-KOH体系的工作液, 在6082铝合金基体上制备平均厚度为18 μm的MAO膜层; (2)采用Nd:YAG激光器对上述MAO膜层进行激光重熔(LSM)处理, 获得MAO+LSM膜层。利用扫描电子显微镜(SEM)、X射线衍射仪、超显微硬度计和电化学分析仪分别检测上述两种膜层的微观形貌、相组成、表面硬度和耐蚀性能。结果表明: 激光重熔后的膜层由内往外分为致密层、中间层和重熔层, 组织致密、气孔率低的重熔层取代了MAO疏松层, MAO+LSM膜层中α-Al2O3相的比例得到提高, 硬度和耐蚀性能也进一步得到改善, 且保持了MAO膜层与基体的结合方式。     

镁合金微弧氧化-溶胶凝胶复合膜层的耐蚀性

用微弧氧化和溶胶凝胶法在AZ91D镁合金表面制备复合膜层,用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)和电化学测试等分析手段表征其成分、相结构和截面形貌,研究了复合膜层的耐蚀性.结果表明,溶胶凝胶膜有效地封闭了镁合金表面微弧氧化膜的微孔,形成结合力好且较为致密的复合膜层.复合膜层的组成主要有MgO、M...