High Phosphorus Electroless Nickel Research Articles

Thermally Assisted Adhesion Enhancement in High-Phosphorous Electroless Nickel Plating

High-phosphorus electroless nickel is a widely recognized protective plating for oilfield metallic parts subject to corrosion and wear. In the present investigation, thermally activated diffusion treatment was applied to enhance electroless nickel (10-13 wt.% P) plating adhesion on low-alloy steel (UNS G41400) and reduce the risks of spalling. High-phosphorus electroless nickel (10-13 wt.% P) was applied to a variety of UNS G41400 low-alloy steel test samples as per ASTM B733 that were subsequently heat-treated in air for four distinct temperatures, i.e., 510, 540, 570, and 600 °C for 2-10 h. Following post-plating diffusion heat treatments, the initial amorphous electroless nickel was replaced by Ni3P precipitates dispersed in a crystalline nickel-rich phase, with an average hardness improvement from 500 to 700 HK. An increased atomic interdiffusion (from 400 to 3.5 µm) was observed at plating–substrate interfaces, resulting in enhanced adhesion and reduced susceptibility toward spalling. This improvement in adhesion was measured repeatedly through post-bending crack analyses and subsequently validated by interface microindentation. Along with diffusion across plating–substrate interface, nickel oxide formation on surface by oxidation was observed to grow at quasi-parabolic rate with no detrimental impact on spalling. In all cases, plating adhesion was improved by heat treatments due to the diffusion-controlled formation of a seemingly ductile layer.

Study of nickel matrix composite coatings deposited from electroless plating bath loaded with TiB2, ZrB2 and TiC particles for improved wear and corrosion resistance

The effect of thermally and electrically conductive TiB2, ZrB2 and TiC particles on the stability of high phosphorus electroless nickel (EN) plating bath was studied through particle surface modifications. The EN composite coatings with optimal contents of the hard particles were deposited on carbon steel substrates, characterized in microscopic morphology and composition (optical microscope, SEM/EDS), crystallinity (XRD), and micro-hardness. The composite coatings were evaluated with erosion and corrosion tests. The results showed that the electrically conductive hard particles affect the stability of EN plating bath in the order of TiB2 > TiC > ZrB2, with the utmost impact from TiB2 and insignificance from ZrB2. The incorporation of TiB2 particles trigged a rapid decomposition of an EN plating bath within 2 h, which is likely due to the high catalytic activity of TiB2 particles. The nickel phosphorus (NiP) matrix composite coatings are able to offer a combination of wear and corrosion resistance to effectively protect carbon steel components from corrosion according to the test results, which supports an expectation that the coatings can be used in harsh environments, e.g., those encountered in marine and oil and gas (O&G). The effect of heat treatment on the coating properties, in particular, corrosion and wear resistance were studied and the mechanisms behind the property changes were discussed as well.

High-Build, High-Phosphorus Electroless Nickel Plating: Process achieves plating to 20mils—without pitting.

High-Build, High-Phosphorus Electroless Nickel Plating: Process achieves plating to 20mils—without pitting.

Electrochemical behaviour of high phosphorus electroless Ni–P–Si3N4 composite coatings

A high phosphorus electroless nickel bath was used to prepare plain Ni–P and composite coatings containing submicrometre size silicon nitride particles. Deposits were characterised for their composition, morphology and electrochemical behaviour. Codeposition of particles in a Ni–P matrix has not influenced the phosphorus content (10 wt-%). Surface morphology of plain Ni–P deposits was smooth; the composite deposits became slightly rough with small nodules due to particle incorporation. Cross-sectional examination of composite coating revealed that the particles were uniformly distributed throughout the thickness of the coating. Potentiodynamic polarisation and electrochemical impedance studies were carried out in 3·5 wt-% sodium chloride solution in non-deaerated condition. Potentiodynamic polarisation studies showed that the corrosion current density value obtained for composite coatings is lower than that for plain Ni–P coatings. Electrochemical impedance spectroscopy studies showed that the coating resistance of the composite coating is higher than that of plain Ni–P coating. This was further confirmed by SEM analysis of corroded samples.

Influence of cubic nanostructure additions on the properties of electroless coatings

In this research, the influence of co-deposited within nickel-phosphorus matrix cubic nano- and micro-sized particles (nanodiamond and micron cubic boron nitride) on the properties of the composite coatings was investigated. Nanometer diamond was synthesised by using the detonation method. It is a kind of materials with properties of diamond and nanometer particle. High phosphorus electroless nickel bath was used to prepare electroless nickel composite coatings from a suspension. In order to characterise the deposits, their structure, morphology and hardness were analysed. The incorporation of particles has a marginal influence on the composition. The influence of thermal processing of the samples on the coating properties was investigated. The highest microhardness, the superior corrosion and wear resistance of the nickel-phosphorus-nanodiamond composite coating was obtained by heat-treated samples.

Effect of high-phosphorus electroless nickel coating on fatigue life of Al–Cu–Mg–Fe–Ni alloy

The fatigue behaviour of Al–Cu–Mg–Fe–Ni alloy was evaluated in four different conditions: uncoated, after second zincating pre-treatment, coated with high phosphorus electroless nickel layer and coated with NiP and heat treated for hydrogen release. The results of the fatigue test indicated an increased fatigue life of the coated aluminium alloy up to 150%. This improvement was associated with the higher strength of the coating as compared to the substrate and with the development of compressive residual stresses in the coating during deposition.

Electrochemical studies on electroless ternary and quaternary Ni–P based alloys

The autocatalytic (electroless) deposition of Ni–P based alloys is a well-known commercial process that has found numerous applications because of their excellent anticorrosive, wear, magnetic, solderable properties, etc. It is a barrier coating, protecting the substrate by sealing it off from the corrosive environments, rather than by sacrificial action. The corrosion resistance varies with the phosphorus content of the deposit: relatively high for a high-phosphorus electroless nickel deposit but low for a low-phosphorus electroless nickel deposit. In the present investigation ternary Ni–W–P alloy films were prepared using alkaline citrate-based bath. Quaternary Ni–W–Cu–P films were deposited by the addition of 3 mM copper ions in ternary Ni–W–P bath. X-ray diffraction (XRD) studies indicated that all the deposits were nanocrystalline, i.e. 1.2, 2.1 and 6.0 nm, respectively, for binary, ternary and quaternary alloys. Corrosion resistance of the films was evaluated in 3.5% sodium chloride solution in non-deaerated and deaerated conditions by potentiodynamic polarization and electrochemical impedance (EIS) methods. Lower corrosion current density values were obtained for the coatings tested in deaerated condition. EIS studies showed that higher charge transfer resistance values were obtained for binary Ni–P coatings compared to ternary or quaternary coatings. For all the coatings a gradual increase in the anodic current density had been observed beyond 740 mV. In deaerated condition all the reported coatings exhibited a narrow passive region and all the values of E p, E tp and i pass were very close showing no major changes in the electrochemical behavior. In the non-deaerated conditions no passivation behavior had been observed for all these coatings.

The physical and electrochemical properties of electroless deposited nickel–phosphorus black coatings

The manufacture of electroless black nickel surfaces had been obtained, through etching electroless nickel deposits by oxidizing acid solution. The morphology, chemical composition and reflectance of pre-etch and post-etch coatings were compared to examine influence of phosphorus and sulfur content on preparation of black surfaces. The non-metallic elements content of electroless nickel deposits was greatly improved after black treatment. It indicated the etching treatment was a selective dissolving process. The nickel atoms can be preferentially removed during the period. Optimum phosphorus content range to produce low reflectance black surface was proposed, after reflectance measurement of black surfaces. Additionally, the effect of co-deposited phosphorus and sulfur atoms on corrosion resistance of electroless nickel deposits was evaluated by electrochemical impedance spectroscopy (EIS). The fitting results indicated that corrosion resistance of high-phosphorus electroless nickel deposits will be significantly reduced after black treatment. However, that of low-phosphorus deposits will be improved.

Influence of particle size on the microstructure, hardness and corrosion resistance of electroless Ni–P–Al 2O 3 composite coatings

High phosphorus electroless nickel bath has been used to prepare composite coatings containing alumina powders (50 nm, 0.3 μm and 1.0 μm). Deposits were characterized for its structure, morphology and hardness. Incorporation of particle has a marginal influence on the composition. More amount of particle incorporation and uniform distribution was found in composite coatings obtained with 1.0-μm (C3) alumina particles compared to 50-nm (C1) and 0.3-μm (C2) alumina particles. XRD results showed a broad peak of nickel and low intensity alumina peaks present in C3 composite coating in as-plated condition. A marginal improvement in hardness was noticed in as-plated composite coatings. A 15% increase in microhardness was observed in the heat-treated (400 °C for 1 h) composite coatings. Potentiodynamic polarization measurements made on these deposits in 3.5% sodium chloride solution showed that uniform corrosion occurred in C1 and C2 composite coatings whereas localized corrosion was observed in C3 composite coating.

An Analysis of Fiber-Induced Surface Defects in Electroless Plated Components

The paper discusses the analysis of a coating defect on a high phosphorus electroless nickel (Ni-11 wt. % P) deposit plated on an aluminum alloy substrate. Preliminary investigations had indicated that the elongated defects were possibly caused by the entrapment of long fibers or particles during the plating. The possible sources of fibers were identified. The SEM/EDS analysis of fibers collected from the air duct filters correlated very well with the defect shape and the EDS profile collected from under the defect site. It appears that the fibers from air duct filters directly above the plating line were blown into the plating tank and getting co-deposited. The paper describes the step-by-step analysis of the defect that led to successful identification of the root cause of the defect.

Preparation and Characterization of Electroless Ni-P and Ni-P-Si3N4 Composite Coatings

SUMMARYThe present work pertains to the study of electroless Ni-P and Ni-P-Si3N4 composite coatings. The deposits are obtained from a proprietary high phosphorus electroless nickel plating bath, comprising nickel sulphate, sodium hypophosphite, complexing agents and stabilizers. The maximum weight percent of Si3N4 incorporated in the electroless deposit is obtained at a concentration of 10 g/l in the bath. The electroless Ni-P deposits having 0%, 2.01%, 5.81% and 8.10% of Si3N4, respectively, obtained from baths containing 0, 2, 5 and 10 g/l of Si3N4, are characterized by optical microscopy, XRD and TEM. Hardness is found to increase with the incorporation of Si3N4 at all heat treatment temperatures studied. Also hardness increases with an increase in weight percent of Si3N4 incorporated in the deposit. The analyses of the composite coatings by XRD and TEM reveal that the inclusion of Si3N4 particles does not change the amorphous nature of the Ni-P matrix.

Synthesis and Corrosion Behavior of Electroless Ni–P– Si3N4 Composite Coatings

The ability to codeposit ®ne particulate matter with an electroless nickel matrix is a major step in the development of processes aimed at the engineering of surfaces. The prime objective of incorporating the particulate matter is to improve wear and corrosion resistance. The most frequently studied systems are electroless Ni±P±SiC, Ni±P±Al2O3, Ni±P±diamond, Ni±P±PTFE and Ni±P±Cr3C2. Very little information is available on electroless Ni±P±Si3N4 composite coatings. Since Si3N4 has high hardness, good oxidation resistance and good chemical stability, it is worthwhile to study this combination. In the present study we codeposit Si3N4 with electroless nickel on medium carbon steel and evaluate its hardness and corrosion resistance. A proprietary high phosphorus electroless nickel plating bath was used. The pH of the bath was 4.8. Medium carbon steel coupons of 30 mm diameter and 5 mm thickness were surface ground (Ra ˆ 0:4 im) and suspended in the plating bath. The plating bath was maintained at a constant temperature of 88 1 8C. The coupons were plated for 2 h. For the preparation of composite coatings, the Si3N4 powder (size ,10 im) of a calculated quantity was mixed thoroughly with 10 ml of the plating solution using a mortar and pestle and then transferred to the plating bath. This process ensures the distribution of Si3N4 paticles throughout the bath. To obtain a uniform dispersion of Si3N4 particles in suspended form in the bath, the plating solution was stirred using a magnetic stirrer. The electroless plated samples were heat treated for 1 h at temperatures of 200, 300, 400, 500 and 600 8C to determine the change in hardness upon heating to different temperatures. In order to represent common industrial practice no special atmosphere was maintained during heat treatment. Hardness measurements were carried out using a Leitz Micro Vickers Tester employing a load of 0.1 kg. Five readings were taken on each deposit and the values were then averaged. Potentiodynamic polarization studies were carried out using EG&G PAR (Model 362) scanning potentiostat. The electrolyte used was non-deaerated 3.5% NaCl solution. The specimens were masked with lacquer so that only a 1 cm area was exposed to the electrolyte. A saturated calomel electrode (SCE) was used as a reference electrode. The corrosion potential (Ecorr) and corrosion current (icorr) were obtained from the polarization curves using the Tafel extrapolation method. Both the Ni±P and Ni±P±Si3N4 coatings did not exhibit any porosity when subjected to the ferroxyl test. Both of them were found to be adherent when tested by the bent test method, following ASTM B 571 and the thermal shock method. The thickness of the deposit was in the range of 22±25 im in all cases after 2 h of deposition. Fig. 1 shows that cross-section of the electroless Ni±P±Si3N4 deposits when viewed by optical microscopy. The incorporation of the Si3N4 particles in the deposit is clearly visible. Fig. 2 shows the weight percentage of Si3N4 particles in the electroless nickel deposit as a function of its concentration (g=l) in the plating bath. It can be deduced from the ®gure that the percentage incorporation of Si3N4 particles (the percentage of Si3N4 represents only the weight percent of Si3N4 throughout this communication unless otherwise stated) increases with an increase in concentration and reaches a maximum at a concentration of 10 g=l. Beyond this concentration of 10 g=l, a slight decrease in the percentage incorporation is observed. A decrease in the percentage of incorporation of the second phase particles was observed earlier in the electroless Ni±P±Al2O3 system by Rajagopal [1]. The increase in percentage incorporation of Si3N4 particles in the electroless Ni±P matrix with increase in its concentration in the plating bath can be

Electrochemical Corrosion Testing of High Phosphorus Electroless Nickel in 5% NaCl

Abstract Electroless nickel coatings are increasingly used in a variety of applications due to their advantageous chemical, mechanical, and physical properties. The purpose of this research is to i...