Effect of accelerators and stabilizers on the formation and characteristics of electroless Ni–P deposits (original) (raw)
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PHASE TRANSFORMATION BEHAVIOUR OF ELECTROLESS NI-MO-P ALLOY COATINGS
IAEME PUBLICATION, 2020
Engineering applications for electroless nickel can be found in virtually every industry. Various physical characteristics of electroless nickel coatings such as hardness, uniformity, and corrosion resistance, as well as the ability to plate nonconductive surfaces make this coating surfaces of choice for many engineering applications. In the present investigation, the preparation and characterization of electroless plain Ni-P and Ni-Mo-P coatings was carried on mild steel with 0.13% of C, 0.18% Mn, 0.1% Si, 99.59% Fe (wt%) dimension of 2.5cmX2.5cmX0.8cm with roughness (Ra=0.5µm) to understand the material performance. The investigation included electroless Ni-P and Ni-Mo-P matrix using two different types of baths. Bath 1 of Ni-P bath uses nickel sulphate as nickel source, while sodium hypophosphite served as the reducing agent and source of phosphorus. Whereas the second bath of Ni-Mo-P had sodium molybdate used as a source of molybdenum along with suitable amounts of complexing agents and stabilizers. The bath 1 was operated at a pH range of 8±0.2 with temperature of 80±2°C. The bath 2 was operated at a pH range of 11±0.2 with temperature of 85±2°C. Elemental compositions of the deposits were examined by means of scanning electron microscope (SEM, Model Leo 4401) with EDAX attachment to determine the Mo and P elements co-deposited in EN matrix. From EDAX analysis, the sample exhibited Ni-P deposit containing 12.75% P and 87.25% Ni and the Ni-Mo-P deposit consists of 1.09% P, 16.25% Mo and 82.66% Ni. DSC thermograms showed that the crystallization temperature obtained for Ni-P coating was 357C and for Ni-Mo-P coating 515C. The activation energy for the crystallization of Ni-P and Ni-Mo-P deposits were 220 kJ/mol and 111 kJ/mol, respectively
Optimization of electroless Ni-P coating bath and its impact in the Industrial Applications
2021
Electroless Ni-P coating is widely used in industrial engineering applications due to its ability to alter and improve the surface properties of the steel substrate. Electroless nickel coating introduce an excellent combination of surface properties. It can add brightness, lustre, and appeal. The final coating layer also possess very good adhesion with coated substrates, this is the reasons for using such layer as an 'undercoat' for other coatings. The ability to produce a very homogenous composition and produce coating with high corrosion resistance are mainly based on the plating bath composition. The present work investigates the influence of bath compositions, which included nickel sulphate, sodium hypophosphite and tri-sodium citrate, on the process of electroless Ni‒P coating. The deposition rate (Dr) as well as the bath stability were monitored to optimize the plating bath conditions with the different composition. The results of this work showed that the deposition r...
Ni-P coatings electroplating - A review, Part I: Pure Ni-P alloy
arXiv: Applied Physics, 2018
In the electroplating industry Ni-P coatings are extensively employed owing to their excellent properties which enable substrate protection against corrosion and wear. Depending on their composition and structure, as-plated deposits demonstrate good mechanical, tribological and electrochemical features, catalytic activity but also beneficial magnetic characteristics. With subsequent thermal treatment hardness of Ni-P metal-metalloid system can approach or be even higher than that of hard Cr coatings. The purpose of this paper is to provide a general survey of the research work dealing with the electrodeposition of Ni-P binary alloy coatings. Proposed phosphorus incorporation mechanisms, Ni-P alloy microstructure before and after thermal treatment, its mechanical, tribological, corrosion, catalytic and magnetic properties are considered, so are the key process variables influencing phosphorus content in the deposits and the roles of the main electrolytic bath constituents. Findings o...
Surface and Coatings Technology, 2019
Electroless nickel-phosphorous (NiP) coatings were produced on low carbon steel substrates for a total plating time of 3 h. Different preparation modalities were pursued. Multilayered coatings were produced by stacking three layers of the same composition by successive electroless plating with rinsing steps in between. On the other hand, coatings termed 'monolayered' for the sake of comparison were deposited by one step electroless process, with and without undergoing bath replenishment of the electrolyte during plating. All the samples were subjected to thermal annealing at 400 ºC for 1 h under argon atmosphere.
Summary of Existing Models of the Ni-P Coating Electroless Deposition Process
International Journal of Chemical Kinetics, 2013
Electroless nickel-phosphorous plating is a technique often employed in preparation of protective, decorative, and functional coatings. Several feasible mechanisms are discussed in the literature. The influence of process parameters on metal coating deposition is analyzed and described. Nevertheless, some basics of the process and the fundamental aspects of plating still not explained. A number of research groups make an effort to provide a description of the process with a physical model. The aim is to design a theoretical model that could be valid under operating conditions on a practical scale. This work gives a short review of the published data on the mechanism and kinetics of the electroless Ni-P deposition process. The review also touches a novel approach-proposition to analyze data using artificial intelligence tools. C 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: [755][756][757][758][759][760][761][762] 2013
Structure and phase transformation behaviour of electroless Ni–P composite coatings
Materials Research Bulletin, 2006
This paper addresses the structural characteristics and phase transformation behaviour of plain electroless Ni–P coating and electroless Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings. The X-ray diffraction patterns of electroless Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings are very similar to that of plain electroless Ni–P coating, both in as plated and heat-treated conditions. Selected area electron diffraction (SAED) patterns obtained on the Ni–P matrix of Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings exhibit diffuse ring patterns resembling the one obtained for plain electroless Ni–P coating. Phase transformation behaviour studied by differential scanning calorimetry (DSC) indicates that the variation in crystallization temperature and the energy evolved during crystallization of plain electroless Ni–P coating and electroless Ni–P–Si3N4, Ni–P–CeO2 and Ni–P–TiO2 composite coatings is not significant. The study concludes that incorporation of Si3N4, CeO2 and TiO2 particles in the Ni–P matrix does not have any influence on the structure and phase transformation behaviour of electroless Ni–P coatings.
Effects of Current Density on Ni–P Coating Obtained by Electrodeposition
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2021
In this work, NiP coatings are deposited on the steel substrate by electrodeposition from a solution containing nickel sulfate and sodium hypophosphite (NaH 2 PO 2). The effect of the current density on the morphology, phase structure, microhardness, and corrosion performance of the NiP coatings are studied. Scanning electron microscopy and energy dispersive X-ray analysis and X-ray diffraction are used to study the morphological, composition and phase structure. The corrosion performance of the coatings is evaluated by weight loss, electrochemical impedance spectroscopy and Tafel polarization. Results showed that the morphology of the electrodeposited NiP alloys coatings has spherical grains for all the samples, and the Ni 3 P phases are formed all over the microstructure of the coatings. It is observed that the phosphorus content and microhardness are dependent on the current density. The corrosion tests show that 5 A⋅dm −2 current density is the optimal value which gives the best protective coating against corrosion. It also exhibits superior microhardness originated from the higher Ni 3 P amount.
Surface and Coatings Technology, 2013
Electroless NiP coatings offer excellent corrosion and wear resistance and ability to withstand acidic and salt solutions. Medium and high phosphorus NiP coatings were produced using plating baths with 10 g/L or 25 g/L of sodium hypophosphite as reducing agent (RA) with composition of the resulting deposits to be 91.5 Ni: 8.5 P and 87.6 Ni: 12.4 P, respectively. From field-emission scanning electron microscope (FE-SEM) examination, the deposit morphology was found to change from nodular with surface porosity and cracks to dense, smooth upon increasing the RA content. Addition of nanostructures such as nanoparticles of alumina (Al 2 O 3) or silicon carbide (SiC) or multi-walled carbon nanotubes (CNT) into NiP matrix, at low loading levels, was investigated for their effect on corrosion resistance and hardness of NiP -Al 2 O 3 , NiP -SiC and NiP -CNT composite coatings. Electrochemical impedance spectroscopy (EIS) studies in 4 wt.% NaCl solution revealed 91.5 Ni: 8.5 P coating to offer much superior corrosion resistance than 87.6 Ni: 12.4 P coating even after immersion for 42 days. Among all composite coatings, however, NiP -Al 2 O 3 produced from 1.0 g/L Al 2 O 3 in plating solution exhibits higher impedance values at low and intermediate frequencies. Nyquist plots for different frequencies were analyzed for comparison between different composite coatings. Microhardness tests indicate higher hardness value of 8.46 GPa for NiP -SiC coating as compared to 7.42 GPa for pure NiP coating.
Pretreatment Effect on the Properties of Electroless Nano -Crystalline Nickel Phosphorous Coating
he influence of mechanical polishing pre-treatments on steel substrates is investigated in terms of microstructure, deposition rate, adhesion, mechanical and corrosion properties of electroless NiP nanocoating with 9-10% wt. of P content. XRD analysis of NiP coatings demonstrated the nanocrystalline structure of coating with the grain size of 39 nm. Results showed that pretreatment of substrate can affect the microstructure and modularity of coatings. Coatings with homogeneous surface profile and lower nodule boundaries had higher corrosion resistance. The roughness of the substrate had a direct influence on the surface roughness of the substrate which had a direct influence on the surface roughness of the applied coating.Prog. Color Colorants Coat. 3(2010), 47-57.