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。     

Anti-corrosion characteristics of nitride-coated AISI 316L stainless steel coronary stents

The corrosion resistance of TiN and TaN coatings deposited on AISI 316L stainless steel thread-coiled coronary stents by pulsed bias arc ion plating is evaluated by electrochemical methods in deaerated Tyrode's simulated body fluids (37 ± 1 °C). The free corrosion potential of the TaN-coated stents is found to be nobler than that of the TiN-coated and uncoated stents throughout most of the immersion time. The potentiodynamic polarization test results indicate that the TaN coatings offer better passivation stability and anti-breakdown performance. The longer-term 6-month immersion tests disclose slight localized corrosion on the surface of both coatings, but no film delamination or large area pitting can be observed indicating reasonably good corrosion resistance after the long period.     

镁合金微弧氧化膜耐蚀性表征方法的对比研究

制备结构、性能相近的AZ91D镁合金微弧氧化膜,通过浸泡、点滴及电化学实验表征膜层的耐蚀性,并结合SEM分析膜层腐蚀前后的表面形貌。本研究中6种耐蚀性检测方法的结果均表明：AZ91D镁合金经微弧氧化处理后耐蚀性显著提高; 失重与增重现象的共存使浸泡实验不能准确评定微弧氧化膜层耐蚀性的优劣; 点滴实验可以较快较准确地反映膜层的耐蚀性,但采纳点滴液开始变色的时间点为评价依据更合适,且测试耐蚀性较好的膜层时,点滴液中硝酸的含量提高到标准中的至少两倍时,才能达到快速检测的目的; 循环伏安、Tafel 极化、开路电位和电化学阻抗谱4种电化学实验能反映诸如腐蚀电位、腐蚀电流密度、阻抗值等更多的信息,可以进一步研究膜层的耐蚀原因。膜层的耐蚀性除了与膜厚、化学成分有关外,还与微观结构膜层内部和表面的密切相关。     

Comparative study of Cr3C2-NiCr coatings obtained by HVOF and hard chromium coatings

In the present work the corrosion resistance of micro-cracked hard chromium and Cr₃C₂-NiCr (HVOF) coatings applied on a steel substrate have been compared using open-circuit potential (E_OC) measurements, electrochemical impedance spectroscopy (EIS) and polarization curves. The coatings surfaces and cross-section were characterized before and after corrosion tests using optical microscopy (OM) and scanning electron microscopy (SEM). After 18 h of immersion, the open-circuit potential values were around −0.50 and −0.25 V/(Ag∣AgCl∣KCl_sat) for hard chromium and Cr₃C₂-NiCr, respectively. The surface analysis done after 12 h of immersion showed iron on the hard chromium surface inside/near surface cracks, while iron was not detected on the Cr₃C₂-NiCr surface even after 18 h. For longer immersion time hard chromium was more degraded than thermal sprayed coating. For hard chromium coating a total resistance values between 50 and 80 kΩ cm² were measured and two well-defined time constants were observed, without significant change with the immersion time. For Cr₃C₂-NiCr coating the total impedance diminished from around 750 to 25 kΩ cm² as the immersion time increased from 17 up to 132 h and two overlapped time constants were also observed. Polarization curves recorded after 18 h of immersion showed a lower current and higher corrosion potential for Cr₃C₂-NiCr coating than other samples studied.     

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.     

微弧氧化-溶胶凝胶复合表面技术改善铝合金的耐腐蚀性能

通过微弧氧化-溶胶凝胶复合表面处理技术来提高铝合金的耐腐蚀性能,分析了多层凝胶层对6061铝合金耐腐蚀性能的影响。采用扫描电镜（SEM）、X射线衍射仪（XRD）和电化学分析等方法对膜层的表面形貌、化学组成、结构以及耐腐蚀性能进行了表征。研究表明：TiO2溶胶渗入微弧氧化陶瓷膜的微孔以及裂纹中,能有效阻挡腐蚀介质的扩散和渗透;复合处理后的试样较仅微弧氧化处理更平滑、致密;膜层除了γ-Al2O3相外,经高温退火处理后出现TiO2锐钛矿,并形成较好的晶相结构;在3.5%NaCl溶液中的室温电化学行为中,复合处理较微弧氧化处理后的试样自腐蚀电位上升最高约400 mV,自腐蚀电流密度最高减小约3个数量级,极化电阻明显增大;随着凝胶层厚度的增加耐腐蚀性能逐渐增强,但当凝胶层数大于4时,膜层龟裂现象严重,并导致耐腐蚀性能开始下滑。     

Improvement in the corrosion resistance of TiB2/A356 composite by molten-salt electrodeposition and anodization

This study reported a novel treatment to improve the corrosion resistance of TiB₂/A356 composites. The method was employed in combination of the molten-salt electrodeposition and subsequent electrochemical anodization technique. By means of molten-salt electrodeposition, the Al coatings were deposited on the surface of TiB₂/A356 composites. It was found that the morphology of the Al coatings is closely related to the current density. Thus, under the suitable condition, a dense and uniform Al coating can be obtained, with the crystal size in the range of 0.5–2 μm and the coating thickness of ~ 9 μm. This continuous Al layer can eliminate the adverse corrosion contribution of TiB₂ particles in Al matrix. The following step of anodization was designed to convert the Al film to an anodized Al oxide film for further corrosion protection. The electrochemical corrosion behavior was evaluated by potentiodynamic polarization curves and electrochemical impedance spectroscopy. These results showed the corrosion resistance was greatly enhanced in TiB₂/A356 composites with an anodized Al-coating than that of the anodized composites. It is evident that the new treatment of metal electrodeposition in molten salts and following anodization is an effective method of anti-corrosion in composites.     

骨植入镁合金表面缓蚀剂覆载的微弧氧化/PLGA复合涂层的制备与表征

目的 在可降解镁合金表面制备缓蚀剂覆载的微弧氧化/聚乳酸-羟基乙酸(PLGA)复合涂层,提高其耐蚀性.方法 首先利用微弧氧化技术在镁合金表面制备出适合复合缓蚀剂涂层的微弧氧化(Micro-Arc Oxidation,MAO)涂层,之后在微弧氧化多孔涂层上浸涂PLGA-缓蚀剂涂层,得到复合涂层,缓蚀剂选择天然植物提取物姜黄素(Curcumin,Cur).利用SEM&EDS、FTIR和AFM等实验对涂层形貌、成分及结构进行分析,通过电化学测试、体外浸泡实验评价涂层的耐蚀性能.结果 FTIR结果表明Cur可成功覆载在涂层中,且不与PLGA发生反应.电化学测试和体外浸泡实验表明MAO/PLGA-Cur涂层能有效提高镁合金的耐蚀性.动电位极化曲线显示MAO/PLGA-Cur涂覆样品的腐蚀电流密度比基体下降了3个数量级,浸泡14 d的质量损失比基体下降62.04％,比未覆载的样品减少26.63％.结论 MAO时间为10 min为最合适复合缓蚀剂涂层的参数.Cur作为缓蚀剂的最佳添加量为0.12％,PLGA的最佳添加量为12％,最佳浸涂角度为0°.     

Effects of additives on corrosion and wear resistance of micro-arc oxidation coatings on TiAl alloy

Ceramic coating was deposited on TiAl alloy substrate by micro-arc oxidation(MAO)in a silicate-aluminate electrolyte solution with additives including sodium citrate,graphite and sodium tungstate.The microstructures and compositions were analyzed by SEM,EDX and XRD.The corrosion and wear properties of the coatings were investigated by potentiodynamic polarization and ball-on-disc wear test,respectively.The results show that the MAO coatings consist of WO3,Ti2O3,graphite and Al2O3 besides Al2TiO5 and Al2SiO5.With additives in the electrolyte,the working voltage at the micro-arc discharge stage decreases,and the ceramic coating gets smoother and more compact.The corrosion current density of MAO coating is much lower than that of TiAl substrate.It can be reduced from 9.81×10-8A/cm 2to 3.02×10-10A/cm 2 .The MAO coatings composed of hard Al2O3,WO3 and Ti2O3 obviously improve the wear resistance of TiAl alloy.The wear rate is-3.27×10-7g/(N·m).     

Corrosion resistance of amorphous hydrogenated SiC and diamond-like coatings deposited by r.f.-plasma-enhanced chemical vapour deposition

This paper reports on the properties and corrosion resistance of amorphous hydrogenated carbon and amorphous hydrogenated SiC films deposited by r.f.-plasma-enhanced chemical vapour deposition at low temperatures (below 200 °C). SiC coatings were prepared from SiH₄-CH₄ gas mixtures. Hydrogenated diamond-like coatings were deposited from classical CH₄-H₂ mixtures. The influence of various deposition parameters was investigated.

Microstructural and mechanical properties of the films were studied (density, hydrogen content, nanohardness, internal stress, critical load and friction coefficient). Two examples of corrosion resistance are given: (1) the corrosion resistance and biocompatibility of SiC and diamond-like coatings deposited on metal implants (Ti alloy) (the corrosion resistance is evaluated through potentiodynamic polarization tests in biological media; the biocompatibility of coated and uncoated metals is compared using differentiated human cell cultures); and (2) the corrosion resistance of SiC-coated magnesium in chloride-containing boric borate buffer at pH=9.3 evaluated from anodic polarization curves and scanning electron microscopy studies.     

6061铝合金表面新型黄色微弧氧化陶瓷层的制备与表征

目的 研究6061铝合金表面新型微弧氧化黄色陶瓷层的制备工艺,并对其微观结构、成分、硬度、耐蚀性能等进行表征。方法 在以Na2SiO3为基础的电解液中加入Na2SnO3进行微弧氧化处理,制备出黄色微弧氧化陶瓷层,并与传统白色、黄色、黑色微弧氧化陶瓷层作对比。采用SEM和EDS分析膜层表面形貌和元素分布,借用XPS对膜层进行成分表征,使用硬度计测试其表面硬度,采用电化学工作站和人造海水腐蚀实验评价陶瓷层的抗腐蚀性能。结果 随着电解液中Na2SnO3浓度的增加,陶瓷层中Sn元素含量增加,Si元素含量减少,陶瓷层黄色饱和度不断增强。黄色含Sn陶瓷层制备过程中,电解液中的SnO32-在高温高压下转化为SnO2,导致陶瓷层硬度达到365HV,高于白色与黑色陶瓷层。在3.5% NaCl溶液中进行电化学测试,黄色含Sn陶瓷层的腐蚀电流密度与腐蚀电位分别为9.34×10-9 A/cm2和-0.34 V,耐蚀性优于白色和黄色含Mn陶瓷层。结论 在电解液中添加Na2SnO3可在铝合金表面生成具有较高硬度和耐蚀性能良好的类似沙漠黄色的陶瓷层,为铝及其合金在多领域的应用奠定了一定的实验基础。     

High-velocity oxyfuel Cr<Subscript>3</Subscript>C<Subscript>2</Subscript>-NiCr replacing hard chromium coatings

Comparative wear and corrosion properties of Cr₃C₂-NiCr (CC-TS) (a high-velocity oxyfuel [HVOF]) and hard chromium (HC) coatings obtained on a steel substrate have been studied. The structural characterization was done before and after measurements by optical microscopy, scanning electron microscopy, and scanning white light interferometry. Wear and corrosion properties were evaluated by ball on disk (ASTM G99-90), rubber wheel (ASTM G65-91), and electrochemical measurements of open circuit and polarization curves. The best corrosion and wear resistance was for the CC-TS obtained by HVOF. The open-circuit potential values measured for both samples after 18 h of immersion were: −0.240 and −0.550 V, respectively, for CC-TS and HC, versus Ag/AgCl,KCl_sat. Three orders of magnitude lower volume loss were found for CC-TS (HVOF) after friction tests compared with HC.     

铝合金双极板磁控溅射Ag掺杂类石墨薄膜表面改性研究

目的研究在铝合金样品表面制备Ag掺杂类石墨薄膜对样品导电、耐蚀性能的影响。方法采用磁控溅射离子镀技术,在6061铝合金表面沉积了Ag掺杂类石墨层,对样品微观形貌、接触电阻和电化学腐蚀性能进行了观察测试。结果类石墨薄膜厚度随着Ag靶电流的提高而增大。与铝合金基体相比,镀膜样品的接触电阻降低了2个数量级,腐蚀电流密度降低了2~3个数量级。Ag靶材电流为0.04 A时,镀膜样品接触电阻(1.5 MPa压强)为1.93 m?·cm~2,腐蚀电流密度低至10~(-5.5) A/cm~2数量级。结论沉积有Ag掺杂类石墨薄膜的样品达到了极低的表面接触电阻与较低的腐蚀电流密度,使镀膜后的铝合金样品具有优异的导电性能与较好的耐腐蚀性能。     

NaOH浓度对铸造铝锂合金微弧氧化膜层显微组织和耐蚀性能的影响

采用含有Na2WO4和不同NaOH浓度的硅酸盐系列电解液,利用微弧氧化(MAO)技术在Al-Cu-Li合金表面制备陶瓷涂层,研究NaOH浓度在1-9 g/L范围内对涂层显微组织和腐蚀行为的影响。利用X射线衍射(XRD)、X射线光电子能谱(XPS)和扫描电子显微镜(SEM)对膜层的组成和微观结构进行表征。结果表明,NaOH促进MAO反应中氧化物的生成,使膜层厚度增加。电化学腐蚀测试(极化曲线、交流阻抗谱)和质量损失试验确定膜层的耐蚀性随NaOH加入量的增加而提高,且在7g/LNaOH溶液中制备的膜层耐蚀性最优。全浸泡腐蚀试验也给出一致的结果。     

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.     

Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

Three kinds of single layer coatings of Zn, Zn15Al, 316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion. The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and natural immersion tests. The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn, Zn15Al, Zn+316L and Zn15Al+316L coatings. The corrosion rate value of Zn15Al coated samples is negative. The corrosion products on Zn and Zn15Al coated samples are compact and firm. The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time, and the latter are more outstanding than the former. But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time. When the coatings are sealed with epoxy resin, the corrosion resistance of the coatings will be enhanced significantly.     

Corrosion behaviour of single and double layer hydroxyapatite coatings on 316L stainless steel by plasma spray

AISI316L stainless steel is extensively used in orthopedic and dental applications. However, this alloy exhibits low integration behaviour when it comes in contact with surrounding bone tissue and implant healing duration can be as much as few months. The aim of this study is the fabrication of biocompatible hydroxyapatite (HA) coatings on stainless steel substrate in order to accelerate the process of osseointegration of implants. The biocompatible single layer of Titania (TiO₂), Hydroxyapatite and bi-layer TiO₂/HA coatings were deposited by atmospheric plasma spray on 316L stainless steel. Coated and uncoated stainless steel specimens were incubated in simulated body fluids and 0.9% NaCl solutions for 1h and 7 days. In vitro electrochemical-corrosion evaluation of coated and uncoated stainless steel specimens have been investigated by Tafel extrapolation and linear polarization methods. Results indicates that corrosion resistance of single layer HA coated stainless steel specimens are superior to single layer TiO₂ and bi-layer HA/TiO₂ coated stainless steel specimens.     

Corrosion protection of commercial steel using stainless steel coatings deposited by Cathodic Arc Plasma Deposition technique

The commercial steel AISI 1010 was coated with AISI 316L steel using Cathodic Arc Plasma Deposition (CAPD) technique. The coatings were deposited in vacuum and in the presence of nitrogen, acetylene and mixture of the two as reactive gases. The coatings were deposited as a function of time while other parameters remained constant. The coatings 0.75 to 1.3 μm thick were adherent and amorphous. The aqueous corrosion properties of the coated samples in 3.5 wt % NaCl solution were studied by Tafel, cyclic and potentiodynamic polarization measurements. The derived corrosion parameters were then compared among the various uncoated and coated samples. The study revealed that the coated samples were more corrosion resistant than the uncoated one. Similarly, the samples coated in the nitrogen + acetylene mixture atmosphere were more corrosion resistant than the samples coated in only nitrogen and acetylene atmospheres. The corrosion parameters were also compared as a function of coating time to ascertain best coating thickness.     

Ni/Cu定向结构涂层在不同浓度H2SO4中的耐蚀性能

为了研究Cu元素对Ni基合金定向结构涂层耐腐蚀性能的影响,向Ni60合金粉末中添加了5%Cu(质量分数,下同),制备了定向结构Ni60/Cu复合涂层。采用电化学试验和浸泡试验,评估了涂层在不同浓度H₂SO₄溶液中的电化学腐蚀特性和浸泡腐蚀性能,探讨了涂层在不同浓度H₂SO₄溶液中的腐蚀行为。结果表明,涂层在不同浓度H₂SO₄溶液中的腐蚀均表现为活化-钝化-过钝化的过程,电化学阻抗谱在整个时间常数内具有典型的容抗特征,H₂SO₄溶液浓度从5%增至80%时,电荷转移电阻先减小后增大,涂层的耐腐蚀性呈现先降低后升高的趋势。随着H₂SO₄溶液浓度的增加,涂层表面的腐蚀程度先加剧后逐渐减缓,且在H₂SO₄溶液浓度为40%时,腐蚀电位移至最负,腐蚀电流密度增至最大。但在H₂SO₄溶液浓度达到80...     

Corrosion behavior of electroless Ni-P alloy coatings containing tungsten or nano-scattered alumina composite in 3.5% NaCl solution

The corrosion protection performance of electroless deposited nickel-phosphorus (Ni-P) alloy coatings containing tungsten (Ni-P-W) or nano-scattered alumina (Ni-P-Al₂O₃) composite coatings on low carbon steel was studied. The effect of heat treatment on the coating performance was also studied. The optimum conditions under which such coatings can provide good corrosion protection to the substrate were determined after two weeks of immersion in 3.5% NaCl solution. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance before and after heat treatment. The Ni-P-W coatings showed the highest surface resistance compared with Ni-P-Al₂O₃ and Ni-P. The surface resistance of Ni-P-W coatings was 12.0 × 10⁴ Ω cm² which is about the double of the resistance showed by Ni-P-Al₂O₃ (7.00 × 10⁴ Ω cm²) and twenty times greater than the surface resistance of Ni-P (0.78 × 10⁴ Ω cm²). XRD analysis of non-heat-treated samples revealed formation of a protective tungsten phosphide phase. Heat treatment has an adverse effect on the corrosion protection performance of tungsten and alumina composite coatings. The surface resistance decreased sharply after heat treatment.