Electroless Ni-P Coatings Research Articles

Reusing oxide-based pulverised fly ash and medical waste particles to develop electroless nickel composite coatings (Ni-P/fly ash and Ni-P/SiO2-Al2O3)

Recycling and reusing materials from waste have become a nexus in the development of sustainable materials, leading to more balanced technologies. In this study, we developed a composite coating by co-depositing recycled ceramic particles, pulverised fly ash (PFA) and medical ceramics (MC), into a nickel-phosphorus matrix using a typical electroless plating process. Scanning electron microscopy (SEM) images indicated well-dispersed particles in the Ni-P matrix. However, compared with the MC particles, the PFA particles were distributed scantily with a lower content in the matrix, which could be due to the less impingement effect during the co-deposition. A modified microstructure with refined grains was obtained for the PFA-incorporated composite coating, as seen in the SEM micrograph. The X-ray diffraction result of the MC-incorporated composite coating showed the formation of NixSiy phases in addition to the typical Ni3P phases for the heat-treated electroless Ni-P coatings. Upon heat treatment, the PFA-reinforced composite coating, due to a modified microstructure, exhibited a higher microhardness up to HK0.05 818, which is comparable to that of the traditional SiC particle-embedded composite coating (HK0.05 825). The findings can potentially open up a new strategy to further advance the green approach for industrial surface engineering.

A novel in-situ activation method on titanium alloys for electroless plating

Plating electroless Ni-P (EN) coating on titanium alloys is a complex process involving intricate pretreatment steps using strong acids that are dangerous to the operators, demanding on the operating conditions and harmful to the environments. To address this issue, this paper proposes a novel in-situ activation method where the substrate is activated in the plating bath. The microstructure and the chemical composition of the EN coatings were studied, the results showed that the coating exhibit typical semi-amorphous structure with ~13 at.% phosphorus content. The relationship between the dosage of the activator and the structure of the coating was investigated and the optimum dosage of activator was determined to be 20 mL/L with respect to the bath. Based on the results, the mechanism of this activation method was also discussed.

Insights into the Electrochemical Corrosion Behavior and Mechanism of Electroless Ni-P Coating in the CO2/H2S/Cl− Environment

The electrochemical corrosion behavior of Ni-P coating in 3.5 wt% NaCl solution-containing CO2 and H2S was investigated using electrochemical methods and surface characterization techniques. The results show that the presence of H2S can enhance the CO2 corrosion of Ni-P coated carbon steel by affecting both anodic and cathodic processes. The adsorbed layer only exists in the very early stage of corrosion and barely improves the anticorrosion performance of the coating. The formation of corrosion products (NiO and Ni3S2) renders temporary protection during immersion, but the addition of H2S accelerates the diffusion process at the electrolyte/coating interface and promotes the electrolyte penetration through the coating, causing severe localized corrosion and coating disbondment. A corrosion model is proposed to illustrate the corrosion and degradation process of Ni-P coated steel in the CO2/H2S/Cl− environment.

Tribological study of mechanically milled graphite nanoparticles codeposited in electroless Ni-P coatings

The present study focusses to enhance the wear resistance of electroless Ni-P coatings with the co-deposition of selflubricating nano graphite particles synthesized by mechanical milling using a high energy planetary ball mill. The coatings were developed on an aluminum substrate and nano graphite particles were co-deposited (4 g/l) into the Ni-P matrix using alkaline hypophosphite reduced electroless bath. Changes in properties after heat treatment at 220 °C for 4 h in vacuum have been correlated with morphological and microstructural changes shown by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) respectively. Energy dispersive analysis of X-ray (EDAX) determined the quality and elemental composition of coatings. Wear resistance, coefficient of friction (pin on disc) and microhardness of electroless Ni-P-graphite nanocomposite coatings were calculated and contrasted with Ni-P coatings. The outcomes reveal that the size of synthesized graphite nanoparticles is 20 nm. Microhardness and wear resistance of electroless coatings have improved after heat treatment. Excellent wear resistance has been observed at the cost of some hardness in Ni-P-graphite nanocomposite coatings over Ni-P coatings.

Corrosion mechanism of electroless Ni–Sn–P coating in multi thermal fluid

Multi thermal fluid generated by burning of fuel and oxygen-containing gas has been applied to enhance the production of heavy oil. While the thermal fluid containing carbon dioxide, nitrogen gas, oxygen and steam has caused serious corrosion damage of metallic tubing. Electroless Ni-P coatings show excellent corrosion resistance in many environments and Sn seems to have the potential to improve coating toughness and corrosion resistance. In the present work, Ni–Sn–P coating was prepared on N80 tubing substrate by electroless method, and its corrosion performance in multi thermal fluid was investigated. The results revealed that electroless Ni–Sn–P coating containing ∼2 wt% Sn was dense, defect-free and uniform, and possessed amorphous structure. After 240 h exposure, the bare N80 tubing suffered from severe corrosion and formed a thick, complex, and porous corrosion scale mainly composed of iron oxides. In contrast, N80 tubing substrate with Ni–Sn–P coating showed much more excellent corrosion resistance by forming an extremely thin NiO/Ni(OH)2/SnO2 corrosion layer and maintaining the amorphous structure.

Parametric Optimization of Electroless Ni-P coatings using Taguchi method

The present work deals with surface roughness characteristics of electroless Ni-P coatings. The optimised process parameters have been determined based on L27 Taguchi Orthogonal array. Bath concentration of nickel sulphate, concentration of sodium hypophosphite and temperature of bath has been considered as variable in this study. The optimum combinations of process parameters and surface roughness have been considered as response variable of the study. It has been found that 24 g/L of Nickel Sulfate, 25 g/L of Sodium Hypophosphite and 80°C temperature gives the minimum surface roughness of the Ni-P coated sample which was 0.23µm. Characterisation of the substrate and the as deposited samples were done by scanning electron microscope (SEM) and optical microscopy for surface morphology, energy-dispersive X- ray analysis (EDAX) for element analysis and X-ray diffraction for phase analysis.

Effect of heat treatment on mechanical and tribological characteristics of Electroless Ni-P deposits

In the present paper, mechanical and tribological characteristics of as-deposited and heat-treated Electroless Ni-P coatings were investigated. Medium phosphorus Ni-P coatings were deposited on mild steel substrate using an acidic bath and subjected to heat treatment at 400°C in a tubular furnace. Surface morphology and elemental analysis of the coatings were carried out using Scanning electron microscope (SEM) and Energy dispersive X-ray spectroscopy (EDS) analysis respectively. Dry sliding wear characteristics of the coatings were investigated by linear reciprocating ball on flat tribometer using AISI E52100 Steel ball as a counter body at room (25±2°C) and elevated temperature (300°C). Hardness results showed significant improvement in the surface hardness of coatings on heat treatment. Low friction coefficient and high wear rate were observed at elevated temperature in comparison of those of tests conducted at room temperature for both as-deposited and heat-treated coatings. Best tribological performance is observed for heat-treated coating tested at room temperature.

Improvement of anti-corrosive and anti-oxidative properties of electroless Ni-P coating

ABSTRACTIn order to improve the anti-corrosive and anti-oxidative properties of electroless Ni-P coating (ENPC), a vanadium conversion coating (VCC) was fabricated on the surface of the ENPC. SEM images and EDX line scanning spectra indicate that as-prepared VCC is supposed to be a thin film with a thickness of a few nanometres. XPS analyses demonstrate that the VCC is mainly consisted of V2O5 or V2O5·nH2O. The acid exposure test data indicate that the VCC-treated ENPC, compared with the pristine one, demonstrates a highly enhanced anti-oxidative property. Furthermore, the result of neutral salt spray test manifests that the VCC-treated ENPC has also a highly enhanced anti-corrosive property, which is further confirmed by the result of electrochemical corrosion test.

Tribocorrosion Behaviour of Electroless Ni-P Coating on AA7075 Aluminum Alloy

Tribocorrosion Behaviour of Electroless Ni-P Coating on AA7075 Aluminum Alloy

Preparation and tribological characterization of graphene incorporated electroless Ni-P composite coatings

Industrial application of electroless NiP coatings are limited by their low toughness and cracking under various loading conditions that in turn requires improvement of toughness using ternary coating systems. In this research work, graphene suspension was added to electroless NiP plating bath in various concentrations to produce four different compositions of Ni-P-G (graphene) coatings. Micro-structural and surface attributes were studied using SEM and white light profilometer respectively. Scratch and indentation behaviors of substrate and coatings were investigated. Graphene incorporation in NiP coating matrix improved the hardness as well as wear resistance. Also graphene supported NiP coating exhibited toughness through crack shielding and crack deflection phenomena.

Insights into the Interfacial Process in Electroless Ni-P Coating on Supercritical CO2 Transport Pipeline as Relevant to Carbon Capture and Storage.

To reduce the amount of greenhouse gas emissions and remedy related environmental damage, the research on carbon capture and storage (CCS) is gaining momentum and so is the search for a more effective way to control corrosion of pipeline steel used to transport impure supercritical (SC) CO2. Herein, we prepared an electroless high-phosphorus Ni-P coating and, for the first time, systematically explored the underlying mechanism of the interfacial process in applying Ni-P coating to protect pipeline steel that transports impure SC CO2. It is found that, benefiting from the formation of a protective surface film, Ni-P coating significantly mitigates the corrosion effects from SC CO2 and impurities (e.g., O2 and NO2), especially the synergistic effect of impurities. Concurrently, it effectively avoids the localized corrosion resulting from nonuniform adsorption of the aqueous phase. Although O2 and NO2 can degrade the coating through boosting water precipitation, deteriorating the water chemistry, and reducing the surface film protectiveness, the corrosion inhibition efficiency of Ni-P coating is invariably higher than 80%, independent of the varying causticity of SC CO2 streams, demonstrating that the coating has a superior stability toward corrosion attack. The as-prepared Ni-P coating undoubtedly holds great potential as an alternative for corrosion control of CO2 transport pipeline in the CCS industry. This work provides a new, feasible method to ensure the safe and efficient operation of CCS.

The influence of phosphorus content on the microstructure and specific capacitance of etched electroless Ni-P coatings

Acidic and alkaline electroless bath Ni-P coatings with varying P contents (4.7–8.1 wt%) were deposited on Ti substrate. These as-deposited Ni-P coatings had no apparent difference in specific capacitance. The deposition rate of coating increased with the increase in NaH2PO2·H2O content regardless of the bath type, while the alkaline bath yielded a lower phosphorus content. After the Ni-P coatings were etched by a HNO3 solution, dealloying first occurred in the boundaries between the nodules and then, in the inside of the nodules. Finally, the nodules were etched into numerous nanoparticles with a size of 25–35 nm. An increased specific surface area, due to porous structures, is the major contribution for high specific capacitance. The phosphorus content significantly affects the corrosion resistance of Ni-P coatings and, thus, plays an important role in deciding the microstructure and specific capacitance of etched Ni-P coatings. The specific capacitance of etched Ni-P coatings is a function of phosphorus content and etching time at a fixed etching condition, and an optimum value exists. The highest value achieved is dependent on phosphorus content. The mechanism of the etched Ni-P coatings used as the electrode of the supercapacitor also was discussed further.

Effect of Heat Treatment on Interfacial Fatigue Strength of Electroless Ni-P Coating

Effect of Heat Treatment on Interfacial Fatigue Strength of Electroless Ni-P Coating

Surface functionalisation by the introduction of self-healing properties into electroless Ni-P coatings

Ni-P∖alginate microgels coatings, as potential metallic protective coatings with self-healing properties, were deposited by the electroless method. The alginate microgels contained nickel chloride and sodium hypophosphite. It was proven that the reduction of nickel ions released from the microgels is possible on the steel and Ni-P coating surface. The self-healing effect of this system was studied by X-ray fluorescence (XRF), chronoamperometry and scanning vibrating electrode technique (SVET). An improved corrosion protection observed here is attributed to the reduction of nickel ions to metallic nickel on the tested surfaces. Differences in the surface concentration of nickel and phosphorous species in the corrosion tested coatings with and without microgels, as evaluated using X-ray Photoelectron Spectroscopy (XPS), provided substantial evidence for the formation of a Ni-P coating from the compounds included in the microgels.

The effect of sodium citrate as a complex agent on the corrosion properties of the electroless Ni-P coating

Electroless Ni-P coatings have a wide range of industrial applications due to their surface properties especially for their corrosion resistance. The research presented investigates the influence of sodium citrate concentration, as a complexing agent, on the surface and corrosion properties of the Ni–P coating layer. The deposition rate (DR) at different sodium citrate concentrations was calculated. The results show that the maximum deposition rate of about 15 μm h−1 was obtained at the lowest sodium citrate concentration of 0.05 M. Surface profiles were used to show the effect of citrate concentration on the final coated surfaces and the average surface roughness (Ra) of the coated samples was calculated. The results show that the citrate concentration has an adverse effect on the deposition rate (DR) and the surface roughness (Ra). Electrochemical testing in aerated artificial seawater was used to monitor the corrosion properties of the coated and uncoated samples. The Ni-P coated samples, when compared to the uncoated steel sample, show a nobler Ecorr and lower corrosion current density (icorr) with an inhibition efficiency range from 86 to 94%. The corrosion properties of coated samples were greatly affected by the citrate concentration in the plating bath. It was found that the increase of citrate concentration results in an increase of coating P content and decrease the porosity involved in coating, which consequently maximizes the corrosion protectability of the coating.

Recent advances in electroless-plated Ni-P and its composites for erosion and corrosion applications: a review

The metallic coating of surfaces plays a vital role in the protection of most industrial applications. Coatings can be carried through various routes (e.g., mechanical and electrochemical plating techniques). Electroless nickel coatings present unparalleled properties and a unique combination of corrosion and wear resistance features. Recently, the use and development of electroless nickel-phosphorus (ENP) coatings has attracted broad attention from many industries (e.g., oil and gas) due to their superior corrosion and wear resistance properties. In the present review article, mechanisms of ENP and preparation methods are briefly outlined. The review sheds light on properties of electroless Ni-P coatings and of their nanocomposites with an emphasis on new products and on their future development.

Tuning Interface to Improve Corrosion Resistance of Electroless Ni-P Coating on AZ31B Alloy

Interface is crucial to enable desirable service performances of coatings on substrates. In this paper, Ni-P coatings were prepared on AZ31B alloy by using electroless plating, with the coating/substrate interface being tuned to improve the corrosion resistance. The interface tuning involved a phosphate treatment prior to the electroless plating, which created a uniform surface of the Mg substrate and finally led to Ni-P plating coatings with enhanced density during the electroless plating. Electrochemical testing was performed to compare the corrosion properties between the Ni-P coatings with and without phosphate treatment. The experimental results evidently showed that the introduction of phosphate treatment, especially after an annealing treatment, greatly improved the corrosion resistance. The underlying mechanisms, revealed by microstructural examinations, were that the phosphate treatment reduced the substrate surface roughness and likely promoted a high and uniform nucleation intensity of the Ni-P coating. Corrosion processes of the unannealed and annealed Ni-P coatings with an interfacial phosphate layer were further clarified for comparison.

Effect of Reduced Graphene Oxide Reinforcement on the Wear Characteristics of Electroless Ni-P Coatings

Electroless composite coatings with various concentrations of reduced graphene oxide (rGO) particles were deposited onto mild steel substrate. The effects of adding rGO particles by varying their concentration from 0 to 100 mg/L on morphology, composition, microhardness, adhesion, wear and friction of the electroless composite coatings were investigated. Among the various parameters that influence the tribological behavior, sliding velocity was varied within a specific range for definite concentrations of rGO to obtain enhanced wear resistance in this study. The micrographs of the worn surfaces and indented spots were examined for the nature of wear mechanism and interfacial adhesion. The wear rate increased with increasing sliding velocity but was relatively stable for coatings with lower concentrations of rGO.

Parametric Optimization of Process Parameters on the Response of Microhardness of Electroless Ni-P Coating

The present work deals with the synthesis of chemically deposited nickel–phosphorous (Ni–P) coating on copper substrate. The process parameters are optimized for maximum hardness based on L[Formula: see text] Taguchi orthogonal design with three process parameters, viz., bath temperature, concentration of nickel Sulphate (a nickel source) and concentration of sodium hypophosphite (a reducing agent), respectively. This is considered and fitted into an L[Formula: see text] orthogonal array (OA) to find out the optimized condition for improved hardness of the coating. The optimized results were obtained from 35[Formula: see text]g/L of Nickel Sulphate, 20[Formula: see text]g/L of Sodium Hypophosphite and 90∘C of temperature. Analysis of variance (ANOVA) was performed to determine the significance of the individual process parameters. ANOVA showed that the factor Nickel Sulphate, the interaction between Sodium Hypophosphite and Temperature were significant in determining the hardness of the coating deposited in the optimized condition. The surface morphology, compositional and phase structure analysis of optimized sample are conducted with the help of scanning electron microscope (SEM), energy-dispersive X-ray analysis and X-ray diffraction (XRD) analyzer, respectively.

Cavitation Erosion Behavior of Electroless Ni-P Coating and Optimization of Process Parameter Using Analysis of Variance with Orthogonal Array.

This study investigated the cavitation erosion resistance of electroless Ni-P (EN) coated gray cast iron (GCI) in seawater solution. Furthermore, the optimum coating design parameters were examined to minimize cavitation erosion damage through analysis of variance (ANOVA) based on the L9 orthogonal array. In this study, four coating design factors were used: concentration of source of nickel (A), concentration of reducer agent (B), deposition temperature (C), and pressure of shot peening (D). In accordance with the regulation of the modified ASTM G32, the cavitation erosion experiment was conducted for 1 hour in a seawater solution to find the optimum design parameters which can minimize the cavitation erosion damage. Besides, ANOVA was performed to verify the contribution of each coating design parameter. As a result, the concentration of reducer agent among the EN process parameters was determined as the most significant factor in the cavitation erosion behavior.