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.

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.

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.

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.

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.

含复合络合剂的化学镀Ni-P合金工艺

介绍了一种含有复合络合剂的高稳定性化学镀Ni-P合金工艺,并讨论了镀液中各组分作用及工艺条件对沉积速度的影响。

铝合金Ni-P-Al_2O_3复合镀前处理工艺和耐蚀耐磨损性能的研究

探讨了铝合金 Ni- P- Al2 O3 复合镀的镀前处理液、预镀液组成以及工艺条件对处理效果的影响 ;测定了 Ni- P- Al2 O3复合镀层的耐蚀耐磨损性能。结果表明 :所研究配制的条件处理液和预镀液 ,在适当的工艺条件下 ,可在铝合金表面上获得质量良好的预镀层 ,能够确保 Ni- P- Al2 O3复合镀层的成功镀覆 ;Ni-P- Al2 O3复合镀层具有优良的耐蚀和耐磨性能。

高磷高耐蚀性化学镀Ni-P合金复合络合剂的研究

选取了对镀层和溶液性能有较大影响的络合剂和促进剂共五因素,采用正交试验法进行了研究,并优化验证了络合剂和促进剂工艺配方,筛选出一种高磷高耐蚀性的化学镀Ni-P合金复合络合剂。

铝合金化学镀Ni-P-B的研究

以二甲基胺硼烷(DMAB)为还原剂,在铝合金上获得了化学镀镍低磷低硼镀层,研究了硫酸镍、次磷酸钠、 DMAB、络合剂、pH值和稳定剂对镀层的沉积速度、显微硬度和微观形貌的影响。通过正交实验和单因素实验,确定了最 佳工艺配方为:24 g／L硫酸镍,适量DMAB,12 g／L次磷酸钠,3 mg／L硫脲,30 mL／L络合剂。所获得的化学镀镍镀层中 P、B、Ni的质量分数分别为:1.81％、0.26％和97.93％。该镀层与基体的结合力良好,硬度在550～710HV范围内,在铝 质活塞上应用获得了满意的效果。

化学镀Ni-P合金复合络合剂的应用研究

在化学镀Ni-P合金溶液中,加入有机酸LA、丁二酸、乳酸和甘氨酸四种络合剂为因素进行正交实验,以磷含量、镀速和稳定时间为考察指标,确定最佳实验方案。结果表明,当复合络合剂中ρ(有机酸LA)为22g/L,ρ(丁二酸)为6g/L,ρ(乳酸)为12mL/L时,三种络合剂复配效果最佳。并对加入复合络合剂所得化学镀Ni-P合金镀层进行X-射线衍射分析、中性盐雾腐蚀测试和溶液使用周期试验。结果表明,组合镀液所得镀层是非晶态的,镀层耐蚀性良好,镀液使用可达6个周期。

乳酸-苹果酸体系化学镀Ni-P合金复合稳定剂的研究

为提高化学镀镍磷合金镀液的使用寿命,研究了乳酸-苹果酸为主配位剂的化学镀Ni-P体系中KI、α-α′联吡啶、含硫有机物等稳定剂对镀液稳定性、镀速、镀层性能的影响。通过正交试验研究了稳定剂彼此复配后形成的复合稳定剂的协同效果,得到了一种稳定性高、镀层综合性能好、镀速适中、镀层孔隙率低、镀态硬度高的复合稳定剂。试验结果表明:使用该稳定剂时,镀液沉积速度保持16～17μm/h,PdCl2催化试验达6h不变色,镀层孔隙率为0.33个/cm2,镀态硬度达600HV以上,镀液使用寿命达9～10周期,各项性能指标均能满足工业应用要求。

复合化学镀Ni-P-SiC在铝合金转杯上的应用研究

采用复合化学镀工艺方法在铝合金转杯表面镀一层Ni-P-SiC合金,提高其耐磨性和使用寿命。对铝合金转杯的预处理工艺、镀液配方、施镀工艺以及镀后热处理工艺进行了研究。所获得工件镀层厚度达40μm以上,硬度可达1390HV0.05以上,其综合性能良好。

铝合金化学镀Ni-P沉积速率的研究

研究了乳酸、酒石酸钾钠、硼酸和柠檬酸钠等对铝合金化学镀Ni-P沉积速率的影响,并对镀层的结合强度以及耐蚀性等方面进行了考察,确定了合适的工艺条件。根据该工艺制备的Ni-P镀层具有良好的表面质量和较高的结合强度,提高了基体的耐蚀性。

基于三元复合络合剂的高磷Ni-P化学镀

针对单一络合剂难以兼顾镀液稳定性、镀速和镀层质量等多重要求,现有复合络合剂或成本过高、或工艺稳定性欠佳等问题,采用柠檬酸钠-乳酸-乙酸钠三元复合络合剂,借助增重法、扫描电子显微镜（SEM）、能谱仪（EDS）和材料耐蚀性快速检测专利技术,系统研究了络合剂及还原剂用量、镀液初始pH值及施镀温度对化学镀Ni-P施镀效果的影响,探明镀速、镀层硬度及其P质量分数、镀层腐蚀防护性能随工艺参数的变化规律。结果表明：利用基于三元复合络合剂的镀液,不仅可获得P质量分数最高为18.41%的高磷Ni-P镀层,而且工艺稳定性优异。在适宜的镀液初始pH值区间（4.0~5.5）,镀层P质量分数受其它工艺参数的影响甚微,能始终稳定在11.12%~14.52%的高位。典型试样SEM分析表明：镀层表面平整、均匀,结构致密,镀层与基体结合紧密且厚度分布均匀。

AZ91D镁合金Ni-P-Al_2O_3纳米化学复合镀的研究

在对AZ91D镁合金传统化学镀工艺改进的基础上加入Al2O3纳米颗粒,获得了Ni-P-Al2O3纳米化学复合镀层,研究了施镀温度、时间和纳米颗粒浓度等因素对镀层的耐蚀性和硬度的影响。实验结果显示,复合镀层的耐蚀性最高可比普通镍磷镀层的耐蚀时间高出170s;同时,硬度比镍磷镀层的高出110HV左右,甚至更高。

Sn-58Bi无Pb焊料与化学镀Ni-P层之间的界面反应

研究了Sn-58Bi共晶焊料与Cu的界面反应以及在Cu基体上化学镀Ni-P层的界面反应.焊接温度为180℃,焊接后时效温度范围为60-120℃,时间为5-30 d.利用SEM,EDAX,XRD对反应产物进行了鉴定.结果表明,焊料与Cu的界面反应产物为Cu6Sn5,与化学镀Ni-P层的界面反应产物为Ni3Sn4,在Ni3Sn4与Ni-P层之间存在一层富P层.在同样条件下,Cu6Sn5的生长速度要快于Ni3Sn4的速度.化学镀Ni-P层中P含量较高时进一步抑制Ni/Sn界面反应生成Ni3Sn4的速度.界面金属间化合物层生长动力学符合x=(kt)1/2关系,表明界面反应由扩散机制控制.由实验结果计算,Cu6Sn5的表观激活能为90.87 kJ/mol;Ni3Sn4的表观激活能则与化学镀Ni-P层中P含量有关,当镀层P含量为9％与16％(原子分数)时,其表观激活能分别是101.43 kJ/mol与117.31 kJ/mol.

以双酸配位剂提高碳纤维化学镀Ni-P层的速度

制备碳纤维增强铝基复合材料前需对碳纤维进行化学镀Ni—P处理，目前已有的碳纤维表面化学镀Ni-P工艺镀速较慢。用苹果酸、丁二酸作配位剂，对碳纤维表面化学镀Ni-P。采用扫描电镜、金相显微镜观察了镀层的形貌；采用能谱仪分析了镀层成分；通过镀覆相同时间内镀层的厚度表征镀速，分析了苹果酸、丁二酸单用及共用含量及工艺参数对化学镀Ni．P的影响。结果表明：双酸配位剂的最优用量为8g/L苹果酸、12g／L丁二酸，最佳镀覆温度87℃，最佳镀液pH值为4．6～4．8；此工艺下，镀层厚度在5min即可达到3．92μm，镀速是目前单酸配位剂最快镀速的3倍左右；最优镀层均匀致密、光滑平整，镀层为Ni—P合金，其中P含量为11．4％。

Study on the Technology of Ni-P Electroless Plating on the Mg Alloy

Base on the analysis for the corrosion mechanism of the Mg alloys,the technology of Ni-P directly electroless plating on the Mg-10Li-1Zn alloys was studied.The effects of the pre-treatment on the morphologies of substrate and plating films were investigated,The result shows that Ni-P electroless plating could be divided two steps:the induction period and the rapid deposition period.The Ni-P film is amorphous structure:A excellent Ni-P coating can be obtained under the optimal parameter.The Ni-P coating can obviously improve the corrosion resistance of Mg alloy in variety environment.