Electroless Ni-P plating on Mg-Li alloy by two-step method

Pretreated Mg-Li alloy sheets were pre-plated in a NiCO3？2Ni（OH）2？4H2O solution to form a thin Ni-P alloy film and then plating in a NiSO4？6H2O solution was carried out to obtain a protective coating.The surface morphology,structure and corrosion resistance of the coating were studied.The results showed that a flat,bright and compact plating layer,which was integrated into the matrix metal,was obtained.The P content of the Ni-P coating reached 13.56%（mass fraction）.The hardness value of the Ni-P coating was about HV 549.The polarization curve showed that the corrosion potential of the Ni-P coating reached ？0.249 V（vs SCE）.A long passivation region was found on the polarization curve,and this phenomenon indicated that the coating has an excellent anti-corrosion property.

Electroless plating and growth kinetics of Ni-P alloy film on SiC_p/Al composite with high SiC volume fraction

After Sn/Pd activating, the SiCp/Al composite with 65% SiC (volume fraction) was coated by electroless Ni?P alloy plating. Surface morphology of the composite and its effect on the Ni?P alloy depositing process and bonding action of Ni and P atoms in the Ni?P alloy were studied. The results show that inhomogeneous distribution of the Sn/Pd activating points results in preferential deposition of the Ni?P alloy particles on the Al alloy and rough SiC particle surfaces and in the etched caves. The Ni?P alloy film has an amorphous structure where chemical bonding between Ni and P atoms exists. After a continuous Ni?P alloy film formed, electroless Ni?P alloy plating is not affected by surface morphology and characteristics of the SiCp/Al composite any longer, but by the electroless plating process itself. The Ni?P alloy film follows linear growth kinetics with an activation energy of 68.44 kJ/mol.

Study of Electroless Ni-P-CNTs Composite Plating

The electroless Ni-P-carbon nanotubes composite plating was studied on the copper substrate. Metallurgical microscope, scanning electronic microscope, X-ray diffractometer and micro hardness tester were used to study the structure, constitution and performance of the electroless Ni-P-carbon nanotubes composite deposit. Experiential results show that, with the increment of carbon nanotubes content in electroless plating solution, the grain size on the sample surface decreases whereas the density of grains and the hardness for composite deposit increases. Moreover, adding carbon nanotubes not only improves the degree of crystallization for the composite deposit but also helps their transformation from the amorphous state to the nanocrystal state.

Removal of nickel from spent electroless nickel-plating bath with nickel foam cathode

The electrochemical method was used to remove nickel ion from spent electroless nickel plating bath (pH=5 3). An electrolytic cell was composed of a porous nickel foam cathode and an inert RuO 2/Ti anode. Nickel ions were reduced and deposited on the surface of the nickel foam cathode. The effect of current density (i), linear velocity of wastewater(v), gap between cathode and anode(d C/A) and reaction time(t) on nickel removal rate and current efficiency were studied. As reaction time prolonged, nickel removal rate increased while current efficiency decreased. And larger v and smaller d C/A can enhance nickel removal rate and increase current efficiency by promoting mass transfer and dropping concentration polarization. The effect of current density on nickel removal by electrochemistry was related to other parameters. After three hours’ electrolysis with i=1 0 A/dm2, v=18 5 cm/min and d C/A=0 5 cm, nickel removal rate and current efficiency reached 85 6% and 29 1%, respectively.

Evaluation of residual stress and corrosion behaviour of electroless plated Ni-P/Ni-Mo-P coatings

Single Ni-P and Ni-Mo-P coatings as well as duplex Ni-P/Ni-Mo-P coatings with the same compositions were prepared by electroless plating.The residual stresses of the coatings on the surface and cross sections were measured by nanoindentation and AFM analysis,and the corrosion behaviour of the coatings in10%HCl solution was evaluated by electrochemical methods,to establish the correlation between the residual stresses and corrosion behaviour of the coatings.The results showed that the single Ni-P and duplex Ni-P/Ni-Mo-P coatings presented residual compressive stresses of241and206MPa respectively,while the single Ni-Mo-P coating exhibited a residual tensile stress of257MPa.The residual compressive stress impeded the growth of the pre-existing porosity in the coatings,protecting the integrity of the coating.The duplex Ni-P/Ni-Mo-P coatings had better corrosion resistance than their respective single coating.In addition,the stress states affect the corrosive form of coatings.

Wear and Corrosion Resistance of Electroless Plating Ni-P Coating on P110 Steel

In order to improve the surface performance and increase the lifetime of P 110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/element distribution and phase constitution of the Ni-P coating were analyzed using scanning electron microscope （SEM） equipped with energy dispersive spectrometry （EDS） and X-ray diffraction （XRD）. Tribological and electrochemical measurement tests were applied to investigate the wear and corrosion resistance of P110 steel and the Ni-P coating. The results showed that a uniform and compact, high phosphorous Ni-P coating was formed. The obtained Ni-P coating indicated certain friction-reduction effect and lower mass loss during friction-wear tests. The Ni-P coating also exhibited higher corrosion resistance in comparison with bared P 110 steel. The obtained N i-P coating has significantly improved the surface performance of P110 steel.

Electrochemical behavior of Cu-Zn-Al shape memory alloy after surface modification by electroless plated Ni-P

The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.

Purification and Regeneration of Spent Electroless NickelPlating Baths by Electrodialysis

A method using electrodialysis to seperate phosphite from spent electroless nickel (EN) plating solution was studied. The major working parameters for the electrodialyzer with our selected membranes such as voltage, current and the flow rate of spent EN bath and condensed solution were optimized. Under the optimum operating conditions, spent EN bath could be effectively purified. And then the purified solution was replenished and reused for EN plating. The life of the EN bath was prolonged for more than 17 metal turnovers (M.T.Os). It showed that the electrodialysis method was one of the most effective means for purification and regeneration of spent EN plating baths and for saving resources and reducing waste.

Comparison Between Electrolysis and Reduction for Treatment of Spent Electroless Nickel Plating Bath

There are lots of residual nickel and organic compounds in the spent electroless nickel plating bath. It not only wastes resource but also causes environmental pollution if the wastewater is discharged without treatment. In this paper, electrolytic method and reduction method for treating spent electroless nickel plating bath were compared. The factors studied included reaction time, pH, temperature, effectiveness and cost. It was found that the recovery rate of nickel by reduction was 99.9% under the condition ofpH 6, 50℃ for 10 min. The purity of reclaimed nickel was 66.1%. This treatment needed about 16 g NaBH4 for a liter spent solution, which cost RMB 64 Yuan. For electrolysis method, with pH 7.6, 80℃, 0.45 A （current intensity） for 2 h, the recovery rate reached 97.3%. The purity was 88.5% for the reclaimed nickel. Moreover, it was found that through electrolysis, the value of TOC （Total Organic Carbon） decreased from 114 to 3.08 g·L^-1 with removal rate of 97.3%. The main cost of electrolysis came from electric energy. It cost about 0.09 kWh （less than RMB 0.1 Yuan） per liter wastewater. Compared with reduction, electrolysis had more advantages, so the priority of selection should be given to the electrolysis method for the treatment of spent electroless nickel plating bath.

Characteristics of microstructure and performance of laser-treated electroless Ni-P/Ni-W-P duplex coatings

Characteristics of microstructures of electroless Ni-P/Ni-W-P duplex coatings were investigated using SEM/EDX and XRD analysis techniques. Microhardness and wear behaviour of the coatings before and after laser crystallization were evaluated by measurements of hardnesses of coating surface and cross-section, and by unlubricated friction and wear experiments. The results indicate that it is possible to prepare electroless Ni-P/Ni-W-P duplex coatings by sequential immersion in two different plating baths. After laser crystallization, the microstructures of electroless Ni-P/Ni-W-P duplex coatings present the characteristics of higher degree of crystallization and larger grain size for outer layer Ni-W-P than inner Ni-P, but outer layer has a higher hardness. The wear resistance of laser-treated duplex coatings in a given process parameter conditions is superior to the as-plated ones. Laser treatment was performed directly in air without argon protection, which provides the possibility for application of industrialized production.

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.

Pretreatment-free Ni-P plating on magnesium alloy at low temperatures

Electrochemically promoted electroless plating(EPEP)was used for the application of pretreatment-free Ni-P coating on AM60B magnesium alloy at low temperatures and the obtained coating was characterized by SEM,AFM,EDS and XRD techniques.Compact,uniform,and medium-phosphorus Ni-P coating with mixed crystalline-amorphous microstructure was obtained by applying a cathodic current density of4mA/cm^2at50℃.Also,island-like nickel clusters were deposited on the alloy surface under the same plating condition but without applying the cathodic current.In addition,the durability of the magnesium alloy against corrosion was strongly improved after plating via EPEP technique which was revealed by electrochemical examinations in3.5%NaCl(mass fraction)corrosive electrolyte.The results of the electrochemical examinations were confirmed by microscopic observations.Thickness,microhardness,porosity and adhesive strength of the deposits were also qualified.

STUDY ON UNIFORMITY OF ELECTROLESS PLATING SOLUTION OF SOLAR CONTROL GLASS

A new type elctroless plating bath for solar control glass with large area uniform plating was presented on the basis of the relative Reynolds numbers , the temperature distribution calculation and the relative structure design. The experimental data of the distribution and change of temperature indicate that the mass transfer of the fluid was steady laminar flow and the difference of the maximum temperature was less than 0 5℃ in glass dipping region of 1000×200×1000mm.

Effect of additives on nickel-phosphorus deposition obtained by electroless plating:Characterization and corrosion resistance in 3%(mass)sodium chloride medium

Nichel-phosphorus(Ni-P)coatings are deposited on mild steel by using an electroless plating process.The effect of three calix[4]arene derivatives,namely tetra methyl ester-P-tertbutyl calix[4]arene(Calix1),tetra acid-P-tert-butyl calix[4]arene(Calix2)and tetra methyl P-tert-butyl-thicalix[4]arene ester(Calix3)on the deposition rate,the deposit composition,and the morphological surface was investigated and the study of growth mechanisms has delivered useful information about the surface properties of deposit.It is found that these additives modify the deposition rate and the nickel crystallization process.In fact,the Calix1 and Calix3 act as an accelerator,while Calix2 acts as an inhibitor for the nickel electroless.Furthermore,it is shown that the chemical bath is more stable with calix[4]arene derivatives addition and the obtained deposits are compact and adherent.It is observed also that the nickel content increases with additives.On the other hand,the X-ray diffraction showed that the orientation peaks are intensified at{111}in the presence of Calix2,confirming obtained results of EDAX spectrum.The cyclic voltammetry revealed that the tested additives strongly influence the cathodic process and slightly affect the hypophosphite oxidation.Finally,it is found that these compounds improve the anticorrosion efficiency of Ni-P coating on the mild steel substrate in 3%(mass)NaCl,where its polarization resistance increases with Calix2 and Calix3 addition.

Preparation and tribological performances of Ni-P-multi-walled carbon nanotubes composite coatings

Multi-walled carbon nanotubes （MWNTs） were wet-milled in the presence of ammonia and cationic surfactant and then used as reinforcements to prepare Ni-P-MWNTs composite coatings by electroless plating. The tribological performances of the composite coatings under dry condition were investigated in comparison with 45 steel and conventional Ni-P coating, Micrographs show that short MWNTs with uniform length and open tips were obtained through the wet-milling process. The results of wear test reveal that the Ni-P-MWNTs composite coatings posses much better friction reduction and anti-wear performances when compared with 45 steel and Ni-P coating. Within the MWNTs content range of 0.74%-1.97%, the friction coefficient and the volume wear rate of the composite coatings decrease gradually and reach the minimum values of 0.08 and 6.22x10-15 m3/（N.m）, respectively. The excellent tribological performances of the composite coatings can be attributed to the introduction of MWNTs, which play both roles of reinforcements and solid lubricant during the wear process.

均匀设计试验方法及其在Ni-P-MoS_2化学镀上的应用

均匀设计是基于试验点在整个试验范围内均匀散布的一种试验设计方法。介绍了该法的特点及其软件的基本功能与基本操作过程。从均匀设计试验方案的建立、试验结果的回归分析及优化、镀液最佳配方的试验验证3个方面介绍了均匀设计法在Ni P MoS2化学复合镀中的应用,并得到了最佳的Ni P MoS2化学复合镀液配方。该法应用于化学镀的工艺试验,简便可行。

化学镀镍废液中硫酸根增值化为硫酸钡试验研究

化学镀镍废液排放量大、成分复杂,其合理处置有利于减轻环境污染和提高资源回收利用率,目前该废液的处置工艺缺少对硫、钠、磷、碳等元素的回收。本研究以除镍后化学镀镍废液和醋酸钡为原料,利用废液中柠檬酸根离子对钡离子的络合作用,采用共沉淀法制备了BaSO_(4)粉体。研究了溶液pH值、柠檬酸根离子与钡离子摩尔比、反应温度和反应时间对硫酸根离子去除率、BaSO_(4)产率及其形貌的影响。结果表明,在溶液pH=9、柠檬酸根离子与钡离子摩尔比为1∶3、反应温度55℃、反应时间10 h的条件下,硫酸根离子去除率达到99.7%以上,BaSO_(4)产率达到98.9%以上;所得BaSO_(4)粉体呈类球形,粒径分布范围窄,纯度高。该工艺实现了化学镀镍废液中硫酸根的增值化利用,符合绿色循环经济发展理念。

温度对镁合金表面化学镀Ni-P合金性能的影响

镁合金直接化学镀工艺中温度是影响镀速和镀层质量的最重要因素之一.镀速与温度的变化有一定的关系,温度是影响沉积速度的一个重要因素,但温度对其具体影响我们还没有足够的认识,缺乏基本数据.文章系统地研究了不同镀液温度下产生镀层的速度,并利用扫描电镜观察镀层的表面形貌;能谱分析仪检测镀层表面的Ni-P含量,并探索最佳镀液温度.

化学沉淀法去除化学镀镍废液中磷的工艺研究

[目的]对化学镀镍废液中的含磷物质进行正确处理和有效回收是实现可持续发展的有效策略。[方法]采用化学沉淀法处理化学镀镍废液,使其中的磷以羟基磷灰石(HAP)沉淀形式得以回收。研究了反应温度、初始pH及Ca/P比(指硝酸钙与废液中磷的质量比)对磷去除率的影响,通过正交试验优化工艺参数。[结果]在温度为75℃、初始pH为12及Ca/P比为1.67的条件下处理后,化学镀镍废液的磷去除率达到了99.998%,并且所得沉淀为HAP。[结论]采用本工艺可有效去除化学镀镍废液中的磷,并且随之产生的HAP有望得以回收利用。

PCB化学镀铜废液中铜的资源化回收工艺研究

[目的]化学镀铜废液含有高浓度重金属离子,属于危险废物,给环境保护带来巨大压力。[方法]基于破络沉淀的原理处理化学镀铜废液,以回收其中的铜。研究了不同促进剂、促进剂投加量、初始pH和反应时间对铜回收效果的影响,再进一步通过正交试验对回收工艺进行优化。[结果]最优的工艺条件为:促进剂CAT-2投加量10 g/L,初始pH 14.0,反应时间48 h。在该条件下处理后废液的总铜浓度由初始的3 680 mg/L降至1.00 mg/L,铜回收率达到99.97%。[结论]采用破络沉淀法可实现对化学镀铜废液中铜的有效回收,有利于提高资源利用率,降低企业生产成本。