AM60B镁合金微弧氧化膜的电化学腐蚀行为

在硅酸盐体系中对AM60B镁合金进行微弧氧化处理,采用循环伏安(CV)法、Tafel极化曲线和电化学阻抗谱(EIS)研究膜层在3.5% NaCl介质中的电化学腐蚀行为.结果表明:AM60B镁合金经微弧氧化处理后,膜层耐蚀性得以显著提高.相比低电压下的膜层,高电压下获得膜层微孔略大,但微孔数量明显较少,厚度显著增加,这使得膜层在整个腐蚀过程中呈现了极强的电阻性和优异的耐蚀能力,甚至测试结束时腐蚀介质仍未渗透至膜基面,而低电压下处理得到的膜层,腐蚀介质已渗透至膜基面且侵蚀了基体.     

Mg-2.4Nd-0.5Sr-0.3Zr生物镁合金表面耐蚀抑菌层的制备与表征

以AgNO_3溶液为介质,采用水热法在Mg-2.4Nd-0.5Sr-0.3Zr生物镁合金表面制备具有抗菌性能的耐蚀膜层,通过XRD、SEM、EDS等技术,对不同水热温度及时间条件下所制膜层的形貌及物相结构进行表征,结合电化学测试及抑菌试验,考察了水热条件对膜层耐蚀性和抗菌性能的影响。结果表明,Mg-2.4Nd-0.5Sr-0.3Zr合金表面膜层主要由层片状Mg(OH)_2和颗粒状Ag/Mg(OH)_2聚集混合组成,随着水热温度的升高及反应时间的延长,膜层厚度逐渐增加。电化学测试结果显示,膜层能有效改善合金的耐蚀性,且随着表面膜层厚度的增加,对应合金样品的耐蚀性增强。此外,经过水热处理制得的合金样品在金色葡萄球菌培养24h后,产生了明显的抑菌圈,表现出了良好的抗菌效果。     

不同电压下钼酸钠对镁合金微弧氧化膜的影响

在硅酸盐体系中添加钼酸钠,对比研究不同电压下钼酸钠对AZ91D镁合金微弧氧化膜层耐蚀性的影响.通过TT260涂层测厚仪、SEM和XRD分别检测了膜层厚度、膜层表面形貌和物相组成.采用点滴和电化学实验评估了膜层的耐蚀性能.结果表明:电解液中加入Na_2MoO_4后,膜层厚度变化不大,膜层点滴耐蚀性有所降低,但电化学耐蚀性呈增加趋势.在高电压下,添加0.42g/L Na_2MoO_4获得的膜层耐蚀性最佳,比低电压下的高约1个数量级,比无添加剂时的高出31倍,比基体高约2个数量级.同时,Na_2MoO_4的加入,可在AZ91D镁合金表面制得棕色系的膜层,起显色作用的物质是MoO2,该物相微溶于HNO3,但在电化学测试的NaCl介质中化学性质稳定,故可根据应用场合进行选择性使用.     

不同种不锈钢电化学腐蚀性能的对比

采用CHI660D电化学工作站研究304、316L、2205、2507不锈钢在模拟塔里木油田复杂腐蚀介质中的电化学腐蚀性能,并通过扫描电子显微镜(SEM)对其表面的腐蚀产物膜进行对比分析.结果表明:2种复杂腐蚀介质条件下,随温度升高,4种不锈钢的耐蚀性和抗点蚀能力都会降低.CO2的通入对不锈钢的腐蚀过程影响较为复杂.20℃时,4种不锈钢的耐蚀性和抗点蚀能力随CO2的加入均降低;而50、80℃时,4种不锈钢的耐蚀性和抗点蚀能力则会增强.相同腐蚀条件下,4种不锈钢的耐腐蚀能力由强到弱的顺序为:2507、2205、316L、304.     

不同电压下制备等厚微弧氧化膜层的能耗及膜层的耐蚀性

首先对硅酸盐体系中的AZ91D镁合金进行微弧氧化处理,然后通过调节电压制备厚度均为25 μm和厚度均为40 μm的两组微弧氧化膜层,并针对这两组等厚度膜层的制备时间、能耗、质量厚度比及耐蚀性随电压的变化规律等进行对比研究.结果表明:随着电压的增大,两组等厚度膜层的制备时间均缩短,能耗均降低.相对于厚度均为25 μm的膜层,厚度均为40 μm的膜层的制备时间更长、能耗更大,同时因40 μm膜层较低的致密性,其在氯化钠介质中的耐蚀性较差,但其较厚的厚度使得膜层在硝酸介质中显现出更为优异的耐蚀性能.     

时间对微弧氧化膜性能的影响

利用微弧氧化技术(MAO),在钛合金表面制备了陶瓷膜层,研究了处理时间(10～22 min)对膜层的形貌、耐磨性、耐蚀性的影响.结果表明,钛合金表面微弧氧化层为多孔结构,随着处理时间的增加,微孔孔径逐渐变小并且微孔分布越来越均匀,膜层耐磨性不断增强,膜层的耐蚀性也不断增强.     

金属喷焊层在动态介质中的腐蚀

采用动态、静态腐蚀试验和电化学测试方法，研究了腐蚀介质状态和合金成分对金属喷焊层耐蚀性的影响。结果表明，在动态介质中，各种材料的腐蚀速度提高５～１５倍。与静态试验所得出的材料耐蚀性次序不同，静态试验主要反映材料的热力学稳定性，动态试验主要反映材料的动力学特性。喷焊层中铁含量的增加对耐蚀性有不利影响。     

金属喷焊层在动态介质中的腐蚀

采用动态、静态腐蚀试验和电化学测试方法，研究了腐蚀介质状态和合金成分对金属喷焊层耐蚀性的影响。结果表明，在动态介质中，各种材料的腐蚀速度提高５￣１５倍。与静态试验所得出的材料耐蚀性次序不同，静态试验主要反映材料的热力学稳定性，动态试验主要反映在材料的动力学特性。喷焊层中铁含量的增加对耐蚀性有不利影响。     

磷化/硅酸盐溶胶封闭复合膜的EIS腐蚀机理

采用电化学阻抗谱EIS测量研究了先磷化再硅酸盐溶胶封闭后处理的热镀锌钢在5%NaCl溶液中浸泡不同时间的腐蚀行为,建立了等效电路模型,分析了相关参数的变化规律,探讨了复合膜的腐蚀机理.结果表明:复合膜的耐蚀性随磷化时间的延长而增强,复合膜高电阻、低电容的特性是抑制基底锌层电极反应的关键;随着浸泡时间的延长,镀锌钢的耐蚀性指标变差,腐蚀初期主要发生复合膜的溶解破坏,腐蚀后期主要发生膜层下基体锌层的腐蚀反应.     

镀锌钢上钼酸盐/硅烷复合膜的组成与耐蚀性

分别采用一步法和两步法在热镀锌钢板表面获得钼酸盐/硅烷复合膜,通过X射线光电子能谱分析(XPS)、俄歇电子能谱剥层分析(AES)、盐雾腐蚀试验(NSS)及Tafel极化曲线等对两种复合膜的化学成分和耐蚀性能进行了研究,并将它们与单独的钼酸盐转化膜、硅烷膜进行对比.结果表明:一步法和两步法制备的复合膜具有相似的双层结构,内层以钼酸盐转化膜(含O、Mo、Zn、P)为主,外层以硅烷膜(含C、O、Si)为主,内外层之间及膜与锌基体之间的化学成分呈梯度变化;与单独的钼酸盐膜、硅烷膜相比,两种复合膜对腐蚀的阴极过程的抑制明显增强,自腐蚀电流减小至单层膜的1/5以下,耐蚀性显著提高;两步法制备的复合膜耐蚀性超过常规铬酸盐钝化膜,而一步法制备的复合膜的耐蚀性比由两步法制备的稍差,但仍接近常规铬酸盐钝化膜.     

反应等离子喷涂TiN涂层电化学腐蚀行为

利用电化学阻抗谱等电化学方法及扫描电镜(SEM)技术,研究了反应等离子喷涂TiN涂层在模拟海水中的电化学腐蚀行为. 研究结果表明:TiN涂层的自腐蚀电位高于基体,涂层对基体能起到良好的腐蚀屏蔽作用;腐蚀介质通过涂层的通孔、微裂纹等缺陷渗入涂层与基体的界面腐蚀基体,从而使涂层电阻下降、电容增加,所产生的腐蚀产物在一定程度上可以抑制腐蚀反应的进行,但不会阻止基体局部腐蚀的继续进行. 涂层的孔隙是造成涂层电化学腐蚀的主要原因.     

脉冲频率及占空比对3D打印Ti6Al4V合金表面生物活性涂层的影响

采用微弧氧化法,在恒定电压下,使用不同的脉冲频率及脉冲占空比,在3D打印Ti6Al4V合金表面制备生物活性涂层。利用扫描电子显微镜、能谱仪、电化学工作站、涡流膜厚仪、Image J软件和划痕仪等对涂层进行结构、性能以及微观形貌表征,研究脉冲频率和脉冲占空比对涂层的影响。结果表明：随着脉冲频率的增加,涂层的平均孔径、Ca/P比、表面粗糙度和厚度均逐渐减小,孔隙率变化不明显;耐腐蚀性先得到改善后变差;涂层与基体的结合力逐渐变大。随着脉冲占空比增大,涂层的平均孔径、孔隙率、Ca/P比、厚度逐渐变大;耐腐蚀性能呈现先好后差的趋势;涂层与基体的结合力逐渐变弱。     

化学镀非晶态Ni-P及Ni-Sn-P镀层在弱酸性介质中耐蚀性研究

以紫铜为基体,采用化学镀制备了非晶态Ni-P,Ni-Sn-P镀层.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线能谱(EDS)等对镀层的结构、微观形貌及元素组成进行分析.通过Tafel极化曲线、电化学阻抗谱(EIS)、开路电位监测及室内加速腐蚀试验,研究两种镀层在pH=5.5,w_(NaCl)=3.5%,以及pH=5.5,wS=20%的土壤介质中的耐蚀性能.结果表明,化学镀非晶态Ni-P及Ni-Sn-P镀层的自腐蚀电流密度是裸铜的4.5%和1.2%,两种镀层在酸性腐蚀介质中具有比金属铜更好的耐蚀性,并且化学镀Ni-Sn-P镀层耐蚀性优于Ni-P镀层.两种镀层的自腐蚀电位均负于铜.     

镁合金表面MoS2/树脂杂化涂层的制备及其摩擦磨损和电化学性能研究

以水作为分散介质,制备了含丙烯酸树脂和MoS2颗粒的分散液,以阳极氧化为前处理,采用电化学共沉积法在镁合金表面制备了MoS2/树脂杂化涂层;采用MR 060型多功能摩擦磨损试验机考察涂层的摩擦磨损性能,并分析其磨损机制;采用PARSTAT2273型电化学工作站测试涂层的电化学阻抗谱及极化曲线;利用扫描电子显微镜和能谱仪分析涂层的表面形貌及结构.结果表明：所制备的涂层厚度高达50 μm,在质量分数为3.5%的NaCl溶液中表现出优异的耐腐蚀性能;MoS2的加入,能够有效降低涂层的摩擦系数,提高其耐磨性.     

热浸Zn-Ti合金镀层的显微组织与耐蚀性能

为了抑制热镀锌过程中因含硅活性钢引起的镀层超厚生长,本文采用在纯锌浴中加Ti的方法,研究了0.09%Si钢在含低于0.1%Ti的几种锌浴中热浸镀获得的组织,并采用盐雾腐蚀,电化学极化以及X射线光电子能谱等方法,研究了Zn和Zn-Ti镀层的耐蚀性能。结果表明,随着锌浴中Ti含量的增加,Ti对ζ相生长的抑制作用增强,合金层厚度逐渐减薄,Ti能有效地抑制含硅活性钢镀层的超厚生长。当Ti含量大于0.05%时,镀层中出现Γ2粒子。Zn-Ti合金镀层在5%NaCl溶液中发生自发腐蚀的倾向小于Zn镀层,其极化电阻增大,腐蚀电流密度减小,耐蚀性能提高。Zn-Ti镀层表面形成的氧化膜由ZnO 和TiO2组成。锌钛合金镀层的耐腐蚀性能优于纯锌镀层是由于在镀层表面形成了更加稳定的TiO2膜。     

Electrochemical behavior of different shelled microcapsule composite copper coatings

Copper/liquid microcapsule composite coatings with polyvinyl alcohol (PVA), gelatin or methyl cellulose (MC) as shell materials were prepared by electrodeposition. The influence of shell materials on the corrosion resistance of the composite coatings in 0.1 M H₂SO₄ was investigated by means of electrochemical techniques, scanning electron microscopy (SEM), and energy dispersion spectrometry (EDS). The results show that the participation of microcapsules can enhance the corrosion resistance of the composite coatings compared with the traditional copper layer. Based on the analysis of electrochemical test results, the release ways of microcapsules were deduced. Gelatin and MC as the shell materials of microcapsules are easy to release quickly in the composite coating. On the contrary, the releasing speed of PVA microcapsules is relatively slow due to their characteristics.     

Microstructure and corrosion resistance of Fe/Mo composite amorphous coatings prepared by air plasma spraying

Fe/Mo composite coatings were prepared by air plasma spraying (APS) using Fe-based and Mo-based amorphous and nanocrystalline mixed powders. Microstructural studies show that the composite coatings present a layered structure with low porosity due to adding the self-bonded Mo-based alloy. Corrosion behaviors of the composite coatings, the Fe-based coatings and the Mo-based coatings were investigated by electrochemical measurements and salt spray tests. Electrochemical results show that the composite coatings exhibit a lower polarization current density and higher corrosion potentials than the Fe-based coating when tested in 3.5wt% NaCl solutions, indicating superior corrosion resistance compared with the Fe-based coating. Also with the increase in addition of the Mo-based alloy, a raised corrosion resistance, inferred by an increase in corrosion potential and a decrease in polarization current density, can be found. The results of salt spray tests again show that the corrosion resistance is enhanced by adding the Mo-based alloy, which helps to reduce the porosity of the composite coatings and enhance the stability of the passive films.     

Corrosion mechanism of micro-arc oxidation treated biocompatible AZ31 magnesium alloy in simulated body fluid

The rapid degradation of magnesium(Mg) based alloys has prevented their further use in orthopedic trauma fixation and vascular intervention,and therefore it is essential to investigate the corrosion mechanism for improving the corrosion resistance of these alloys. In this work, the effect of applied voltage on the surface morphology and the corrosion behavior of micro-arc oxidation(MAO) with different voltages were carried out to obtain biocompatible ceramic coatings on AZ31 Mg alloy. The effects of applied voltage on the surface morphology and the corrosion behavior of MAO samples in the simulated body fluid(SBF) were studied systematically. Scanning electron microscope(SEM) and X-ray diffractometer(XRD)were employed to characterize the morphologies and phase compositions of coating before and after corrosion. The results showed that corrosion resistance of the MAO coating obtained at 250 V was better than the others in SBF. The dense layer of MAO coating and the corrosion precipitation were the key factors for corrosion behavior. The corrosion of precipitation Mg(OH)2and the calcium phosphate(Ca–P) minerals on the surface of MAO coatings could enhance their corrosion resistance effectively. In addition, the mechanism of MAO coated Mg alloys was proposed.     

Effect of nano-SiC particles on the corrosion resistance of NiP-SiC composite coatings

NiP-SiC (≈1 1wt% P) composite coatings were electroplated in a Brenner type plating bath. The coatings had amorphous nano-phase composite structure. Direct current and alternating current electrochemical tests were carried out on such coatings in a 3.5wt% solution of NaCl to evaluate their corrosion resistance. The potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) tests, and exposure experiments all show that the corrosion resistance of NiP-SiC coatings first increases and then decreases when the SiC content increases, but the corrosion resistance of NiP-SiC composite coating is better than that of amorphous NiP coatings.