High corrosion and wear resistant electroless Ni–P gradient coatings on aviation aluminum alloy parts

A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.

Tribological Behaviors of Electroless Nickel-Boron Coating on Titanium Alloy Surface

Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.

Effects of zincate treatment on adhesion of electroless Ni-P coating onto various aluminum alloys

The effects of alloying elements on zincate treatment and adhesion of electroless Ni-P coating onto various aluminum alloy substrates were examined.Surface morphology of zinc deposits in the 1st zincate treatment and its adhesion were changed depending on the alloying element.The zinc deposits in the 2nd zincate treatment became thinly uniform,and the adhesion between aluminum alloy substrate and Ni-P coating was improved irrespective of the alloying element.XPS analysis revealed the existence of zinc on the surface of each aluminum alloy substrate after the pickling in 5% nitric acid.This zinc on the surface should be an important factor influencing the morphology of zinc deposit at the 2nd zincate treatment and its adhesion.

High-temperature Compressive Performance of Mg Alloy Foams Coated with Ni-P Layer

Mg/Ni hybrid foams were fabricated by the electroless method.The Ni-P(Nickel-Phosphorous)coatings were deposited on the surface of closed-cell Mg alloy foams.The composition,microstructure and phases of the Ni-P coatings were characterized by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS)and X-ray diffraction(XRD),respectively.The compressive tests were performed on the Mg/Ni hybrid foams at 400℃using the Mg alloy foams as a reference.The experimental results show that the yield strength,plateau stress and energy absorption capacity of the closed-cell Mg alloy foams at high temperature were improved by the Ni-P coating.And there are four main modes for the Mg/Ni hybrid foam failure at 400℃,i e,shearing in cell wall,bending in cell edge,shedding and cracking in Ni-P coating.

Progress of electroplating and electroless plating on magnesium alloy

The current research processes of electroplating and electroless Ni-P alloy plating on magnesium alloys were reviewed. Theoretically,the reason for difficulties in electroplating and electroless plating on magnesium alloys was given.The zinc immersion, copper immersion,direct electroless Ni-P alloy plating and electroplating and electroless plating on magnesium alloys prepared by chemical conversion coating were presented in detail.Especially,the research development of magnesium alloy AZ91 and AZ31 was discussed briefly.Based on the analysis,the existing problems and future research directions were then given.

Influence of pH values on electroless Ni-P-SiC plating on AZ91D magnesium alloy

A novel Ni-P-SiC composite coating was prepared by electroless plating in order to improve the corrosion capacity and wear resistance of AZ91D magnesium alloy.The influence of pH values on deposition rates and properties of the coatings was studied.The microstructure and phase structure of the Ni-P-SiC coatings were analyzed by scanning electron microscopy(SEM)and X-ray diffractometry(XRD).The corrosion and wear resistance performances of the coatings were also investigated through electrochemical technique and pin-on-disk tribometer,respectively.The results indicate that the composite coating is composed of Ni, P and SiC.It exhibits an amorphous structure and good adhesion to the substrate.The coatings have higher open circuit potential than that of the substrate.The composite coating obtained at pH value of 5.2 possesses optimal integrated properties,which shows similar corrosion resistance and ascendant wear resistance properties to the substrate.

A novel electroless silver depositing method for magnesium alloys

Depositing silver on magnesium alloy by both electroless plating and organic coatings was studied. The organic coating was made by immersing samples in organosilicon heat-resisting varnish. In this method the organic coating acts as interlayer between the substrate and silver film. When the reaction starts, silver deposits directly on the interlayer. X-ray diffraction and SEM analysis were used to determine the composition and morphology of the interlayer and silver film. The potentiodynamic polarization curves for corrosion studies of coated magnesium alloys were performed in a corrosive environment of 3.5% NaCl(mass fraction) at neutral pH (6.9). The results indicate that compared with the substrate, the corrosion resistance of coated magnesium alloys increases greatly. Moreover, the method proposed in this work is environmentally friendly, non-toxic chemicals were used. In addition, it provides a new concept for the corrosion inhibition of magnesium alloys.

A novel dual nickel coating on AZ91D magnesium alloy

Magnesium alloys covered with metal coating display excellent corrosion resistance,wear resistance,conductivity and electromagnetic shielding properties.The electroless plating Ni-P as bottom layer following the electroplating nickel as surface layer on AZ91D magnesium alloy was investigated.The coating surface morphology was observed with SEM and the structure was analyzed with XRD.Electrochemical tests and salt spray tests were carried out to study the corrosion resistance.The experimental results indicate that the dual coating is uniform,compact and pore-free.The adhesion strength between magnesium alloy substrate and electroless plating Ni-P bottom layer and electroplating nickel surface layer is perfect.The corrosion resistance of AZ91D magnesium alloy is greatly improved after being protected with the dual coating.

稳定剂KI对化学镀Ni-Fe-P-B合金性能的影响

利用化学镀方法沉积铁合金系镀层，具有诱人的软磁性能，应用于计算机以及磁头材料等领域。近期研究较多的镀层主要有：Fe—P、Fe—Ni-P、Fe-Mo-B、Fe-W—B、Fe—Sn—B、Fe—Mo—W—B和Fe—Ni-P-B等体系，并取得了可喜的成果。但也存在不少问题，化学镀液本身处于热力学不稳定状态，常要加入稳定剂，阻止H2PO2^-分解。目前常用稳定剂：（1）重金属离子，如Pb^2＋等；（2）无机含氧酸根离子，如IO3^-等；（3）有机酸，如柠檬酸等；

医用Co-Cr合金表面化学镀铜抗菌涂层的制备及性能

钴铬合金具有良好的耐磨性、耐菌性及生物性能,是理想的医用金属材料,但钴铬合金对细菌的粘附往往比较敏感,容易引发口腔细菌感染,因而采用化学镀方法在钴铬合金上镀铜,对镀铜工艺参数进行单因素变量研究,得出化学镀铜最佳实验方案为:硫酸铜质量浓度为16 g/L,酒石酸钾钠质量浓度为46 g/L,NaOH质量浓度为15 g/L,甲醛为15 g/L,pH为12.9。通过采用XRD分析和SEM表征结果表明,化学镀铜后表面化学成分大部分为Cu,且分布密集,厚度约为6~7μm。涂层和基体结合稳定,不易脱落,镀铜后的钴铬合金抗菌性能明显得到提高。

钛铜合金接插件连续电镀及化学镀高磷镍工艺优化

针对智能手机零件的无磁性要求,采用钛铜合金为基材进行电镀和化学镀高磷镍。通过正交试验对镀前阳极电解脱脂、阴极电化学浸蚀、冲击镀镍,电镀高磷镍和化学镀高磷镍,以及镀后封孔工艺进行优化。研究了镀层P含量对其磁导率的影响,得出镀层P质量分数至少为11%方可满足静态磁导率小于1.003 H/m的要求。目前该连续电镀及化学镀高磷镍工艺已用于实际生产,产品合格率高达99.8%以上。

Coupling a titanium dioxide based heterostructure photoanode with electroless-deposited nickel-phosphorus alloy coating on magnesium alloy for enhanced corrosion protection

The utilization of photoelectrochemical cathodic protection(PECCP)enables an indirect corrosion pro-tection of metals with low self-corrosion potential by introducing a metallic nickel interlayer.However,the ability to enhance the PECCP efficiency remains challenging because of the inherent property of the semiconductor.Herein,this ability is demonstrated by coupling a covalent organic framework(TpBD)dec-orated TiO 2 photoanode(TiO 2/TpBD)with nickel coating on magnesium alloy for an effective corrosion protection.The composite photoanode showed direct PECCP for the nickel interlayer and indirect corro-sion protection of the magnesium alloy.The composite structure of the nanotube array and the covalent organic framework for the photoanode were confirmed by field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).The en-hanced photoelectrochemical conversion capability and PECCP performance of the nickel-coated Mg alloy were evidenced by the results from electrochemical and photoelectrochemical measurements including Mott-Schottky curves,photoinduced potential variations,and electrochemical impedance spectroscopy(EIS).Lastly,a corrosion protection mechanism is proposed,where the enhanced PECCP efficiency is at-tributed to the formation of a direct Z-scheme heterojunction,which is substantiated by the results from valence band(VB)XPS and electron spin resonance characterizations.

化学镀Ni-P镀层晶化过程研究

化学镀Ni-P镀层的显微组织对其服役性能有重要影响.通过SEM、TEM、XRD和DTA等分析手段,研究了压铸镁合金表面Ni-P镀层的晶化过程.结果表明,初始化学镀层不仅有非晶,还有亚稳态纳米晶;镀层的初始晶化温度大约为300℃,450℃晶化过程完成;升温过程中的原子扩散和纳米晶的长大导致有新的亚稳态相析出和转变;有序畴和析出物一起长大最终产生晶界.

化学镀Ni-P合金工艺的优化

用五种化学镀工艺制备了Ni-P合金镀层。用动电位极化曲线法比较镀层的耐均匀腐蚀性能,用溶液浇浸法测定了镀层的耐孔蚀性能,并用X-射线衍射仪和扫描电子显微镜分别研究镀层结构和表面形貌。结果表明:工艺2制备的镀层具有较高的耐均匀腐蚀和耐孔蚀性能,属于非晶和微晶组成的混晶结构。并对该工艺进行了正交试验,得到了最优工艺条件。

温度对化学镀Ni-P合金层形貌、硬度及耐蚀性的影响

目的揭示在70-95℃施镀温度范围,Ni-P合金镀层显微形貌的变化规律,并探讨表面形貌结构、合金硬度及耐蚀性能的相关性。方法以施镀温度为变量,通过化学沉积的方法制备Ni-P合金镀层。对镀层表面形貌进行表征,测试镀层硬度,并采用盐酸为腐蚀介质进行浸泡,以相对腐蚀速率表征镀层的耐蚀性。结果在70-95℃的施镀温度范围内,随着温度升高,镀层形貌先趋于致密和平整,而后表面粗化,镀层的硬度和耐蚀性均呈现先提高、后降低的趋势。最佳镀层形貌和硬度值出现在85℃,耐蚀性最好的施镀温度区间为85-90℃。结论当镀液p H值为4.5±0.1,施镀时间为3 h时,施镀的最佳温度为85℃。此条件下制备的镀层表面平整且均匀致密,硬度高,耐蚀性能优异。

镁锂合金的腐蚀机理及表面防护方法研究进展

镁锂(Mg-Li)合金具有质量超轻、强度高、延展性好和成形性好等优点,在汽车、航空航天、军事及核工业等领域具有广阔的应用前景。但是高化学活性的锂使该合金易在使用环境中发生腐蚀且难以防护,限制了其广泛应用。因此,研究Mg-Li合金的腐蚀机理并发展有效的防腐蚀技术极为重要。基于近年来国内外的研究进展,本文综述了Mg-Li合金在大气、中性及碱性NaCl溶液和模拟人体体液中的腐蚀机理,介绍了Mg-Li合金在不同环境中的腐蚀过程。同时对Mg-Li合金的表面防护方法作了系统总结,包括阳极氧化、电镀与化学镀、化学转化、涂层及其他表面防腐蚀方法,分析了各种表面防护方法的特点、优势与不足。并对Mg-Li合金表面防护的未来发展进行了展望,提出通过涂层的复合化、功能化及自修复化可以提高涂层对Mg-Li合金的防腐蚀性能和实用性。

钨铜合金化学镀镍磷镀层在NaCl溶液中的腐蚀行为

采用化学沉积的方法在W-Cu粉末合金上成功地实现了化学镀Ni-P镀层,镀层表面光滑、致密,在结构上属于非晶态;经过25 d的3.5 mass%NaCl溶液浸泡研究表明:在浸泡的前16 d中,化学镀Ni-P镀层的腐蚀速率逐渐增大,在16 d之后腐蚀倾向有所降低;通过腐蚀失重实验得到Ni-P镀层的腐蚀失重小于W-Cu合金,说明化学镀Ni-P镀层可以对W-Cu合金起到保护作用。

空心微珠表面化学镀Ni-Co-P合金

以无机非金属粉煤灰空心微珠为芯材,利用化学镀工艺对其表面进行金属化改性,可以得到表面完整包覆的导电粉体,该粉体具有中空,质轻,粒度细,高强度,耐高温,导电性能好等多种优异性能,可部分代替金属和铁氧体微粉作为电磁波吸收剂.采用SnCl2和PdCl2进行敏化-活化处理后,在空心微珠表面化学包覆Ni-Co-P合金层,利用XRD、EDS、SEM和镶嵌金相等方法对样品进行形貌观察和分析表征,结果表明,使用PdCl2作活化剂可以得到优质均匀的Ni-Co-P合金镀层,镀层光亮,均匀,包覆完整.化学镀后镀层呈非晶态,450℃氢气气氛下热处理后出现结晶相Ni3P和六方晶系的!-Co单质.

AZ91D镁合金化学复合镀Ni-P-ZrO_2的工艺与性能

对镁合金传统化学镀工艺进行了改进,避免了使用氢氟酸和六价铬等有毒物质。采用化学镀与化学复合镀相结合方法,在AZ91D镁合金上获得了Ni-P-ZrO2纳米化学复合镀层,并研究了新工艺化学镀前处理和镍沉积机理及复合镀层的结构和性能。结果表明:新工艺方法获得的Ni-P镀层更均匀、致密,耐蚀性优于传统工艺化学镀层;Ni-P-ZrO2复合镀层与AZ91D合金基体在3.5%NaCl溶液中的动电位极化曲线对比表明,该复合镀层对镁合金可以起到明显的保护作用;从磨损实验结果可见,Ni-P镀层的磨损质量损失率几乎为Ni-P-ZrO2镀层的3倍,说明ZrO2纳米粉的加入能改善镀层的耐磨性。

原位测量法研究AZ31镁合金表面化学镀Ni-P的沉积机理(英文)

设计一种原位方法去测量AZ31镁合金在化学镀Ni-P过程中基体在镀液中的开路电位和体积表面的镀层形貌变化。通过开路电位曲线、扫描电子显微镜和能谱分析研究AZ31镁合金化学镀Ni-P的沉积机理。结果表明:化学镀Ni-P的沉积过程包括镀层的形成过程和镀层的增厚过程,其中镀层的形成过程又包括镍晶核的形核和长大过程、镀层的二维扩展过程和镀层的三维搭接过程。扫描电镜分析证实了Ni-P镀层的球形瘤状物不仅形成于镀层的增厚阶段,同样也形成于Ni-P镀层的初始沉积阶段。不同沉积阶段的沉积速度变化分别与各自的沉积机理对应。