Papers by Keyword: Electroless Ni-P Plating

Abstract: Electroless Ni-P plating on Mg-7Al alloy by chemical conversion pretreatment was investigated. Morphology of electroless nickel plating coatings and phase compositions were measured by SEM, EDX and XRD. The optimized bath composition parameters were determined through orthogonal design. The morphology of electroless nickel plating coatings on Mg-7Al alloy exhibits a nodular structure and resembles the surface of a cauliflower and the coating is compact and consists of amorphous Ni-P coating. Potentiodynamic polarization curves of the Ni-P coatings in 3.5% NaCl show that the Ni-P coating extensively improves the corrosion resistance of Mg-7Al alloy and the highest corrosion potential reached to -0.54V vs. SCE(saturated calomel electrode). The results of the orthogonal experiment show that Nickel Sulfate of 25 g/L, Sodium Hypopho-sphate of 25 g/L and Citrate 7.5 g/L can be considered as the optimum bath content parameters for electroless Ni–P plating on Mg-7Al alloy and Nickel Sulfate has more effect on corrosion potential than Sodium Hypophosphate and Citrate..

Abstract: Electroless nickel plating coatings on AZ91D alloy by phosphate pretreatment were prepared. The coating resembles a cauliflower and is compact. It consists of amorphous Ni-P. Potentiodynamic polarization curves of the Ni-P coatings in 3.5% NaCl show that the electroless Ni-P coating improves the corrosion resistance of AZ91D alloy and the highest corrosion potential reached to -0.513V vs. SCE. The results of the orthogonal experiment of process parameters indicates that temperature 80°C, time 120min and pH 7.5 can be considered as the optimum process parameters for electroless Ni–P plating on AZ91D alloy and pH value in the bath has more effect on corrosion potential than temperature and time.

Abstract: The effects of the concentrations of NiSO₄•6H₂O, NaH₂PO₂•H₂O and complexing agents in bath, temperature, pH, SiC concentration etc. on deposition rate of electroless Ni-P plating were systematically studied. The appropriate deposition rate of electroless Ni-P plating (17μm h^-1) was obtained at the optimal conditions. The deposition reaction dynamics of electroless Ni-P plating on AZ91D magnesium alloy was discussed and the corresponding kinetic model was also determined based on the corresponding experimental results.

Abstract: In order to improve 6063A aluminium surface condition, electroless plating technology was used to obtain Ni-P coating on 6063A aluminium surface, the properties of Ni-P coating were investigated by means of scanning electron microscopy (SEM), X-ray diffractometer, microhardness teste, coating adhesion nick meter and electrochemical workstations. The result indicate that, the Ni-P coating shows a amorphous structure with compact structure, the hardness is about 4 times of substrate; the combination of the coating and the substrate is good, the strength for 42.25 N; after electroless plating, self-corrosion potential shift for positive direction for 0.55 V, the self-corrosion current density lower two orders of magnitude compare to the substrate, polarization resistance significantly increased, which shows that after electroless Ni-P plating, the corrosion resistance increase apparently.

Abstract: Magnesium alloys are being used as structural components in industry because of their high strength to weight ratio. But their high electrochemical activity and poor corrosion resistance limited their applications. Therefore, surface modifications are needed for protection purpose. This paper studied the anodic micro-arc oxidation and electroless Ni-P plating surface modifications on AZ80 magnesium alloy. The SEM, XRD and EDS were used to characterize the surface coating. It shows that a micro-porous MgO layer with the pores size 5 – 20 μm was fabricated on the bare magnesium alloy. The nodule Ni-P deposition could be prepared on the out layer of MgO with Ni/P atomic ratio being 1.4. The pores in MgO layer could be sealed by the following Ni-P deposition. Therefore the corrosion resistance of the magnesium alloy could be further improved.

Abstract: In order to improve and simplify the process of electroless Ni-P plating on AZ91D magnesium alloy substrate, pretreatment process and deposite time were optimized by orthogonal test, the plating morphology were analysed using Quanta 200 type scanning electron microscope. The bond between the plating and aluminum substrate were evaluated using method of water quenching and alternating bending test. The results show that good coating can be obtained on AZ91D substrate under the condition of the acid electroless Ni-P plating solution with pickling time of 40-50s, activated time of 10 min. And the good bond between the coating and AZ91D substrate was obtained.

Abstract: In order to improve and simplify the process of electroless Ni-P plating on aluminum substrate, a activated solution and process were optimized by orthogonal test, the plating morphology were analysed using Quanta 200 type scanning electron microscope. The bond between the plating and aluminum substrate were evaluated using method of water quenching and alternating bending test. The results show that good coating can be obtained on aluminum substrate under the normal condition of the acid electroless Ni-P plating solution with sulfuric acid of 120g/L and nitric acid of 10-15g/L as activated solution and activated time of 20 min. And the good bond between the plating and aluminum substrate was obtained.

Abstract: In order to improve deposition speed of electroless nickel plating coating, composition of complex accelerating agent was optimized by orthogonal test, and SEM and its EDS was used to analyze the plating morphology. The results show that the deposition speed is increased to 27.5μm/h after 0.002g/L of cadmium sulfate, 0.05g/L of sodium dodecyl sulfate, 10g/L of malic acid and 15g/L of butanedioic acid was mixed into an electroless plating solution. The coating holds good surface quality and its phosphorus content is 14.03%, any pore was not found on the surface and decay resistance of the coating was improved.

Abstract: In this work, one step for sensitization and activation in pretreatment process is adopted. The influences of the temperature, pH value on electroless Ni-P plating on PVC plastic were discussed. The components and surface morphology of the coating were studied by using SEM and EDS. The results show that the optimum operating condition is temperature being 50～55 , the optimum pH value being 8.5. Under the optimal technical conditions, the deposits is smooth and uniformity. The adhesion between the deposits and the matrix is better, The deposit contains 97.68% (wt) Ni and 2.32% (wt)P by the analyses of energy disperse X-ray.

Abstract: A new procedure of surface activation without using palladium salt is proposed for electroless nickel plating (Ni-P) on carbon fiber. The optimal formula and technical conditions for palladium-free activated electroless Ni-P were obtained by orthogonal experiments. The effects of nitric acid processing time on the quality of nickel coating was investigated .The effects of varying concentrations of Ni2 + on the rate of weight gain during the Ni2 + complex adsorption process were also analyzed and the kinetic equation of the process was established. The theoretical values calculated by the equation were proven to be consistent with the experimental verification. The material characteristics of the deposited layers were analyzed by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and X-ray diffraction (XRD). The tensile strength of the carbon fibers was analyzed by the Weibull method, and this showed that when the thickness of the Ni-P coating reached 0.150μm, the tensile strength reached a maximum value. The experimental results showed that the nickel deposition on the carbon fiber surface obtained by this method, had the same uniformity, compactness and adhesive properties as the one by conventional electroless Ni-P.