Electroless Nickel-phosphorus Coatings Research Articles

Wear Resistance Behavior of Low-, Mid-, and High-Phosphorus Electroless Ni-P Coatings Heat-Treated in the Air Environment

The high-temperature heat treatment of electroless nickel–phosphorus (Ni-P) coatings in an air environment, and its consequences have scarcely been investigated. This work investigated tribological characteristics of the high-temperature, heat-treated, electroless Ni-P coatings on steel substrates with low-, mid-, and high-phosphorus content for which the average phosphorus content was 2.4 wt.%, 7.1 wt.%, and 10.3 wt.%, respectively. X-ray fluorescence and energy dispersive spectroscopy were implemented to determine the phosphorus content of the coatings. The oxidation of Ni and the formation of the NiO layer on the coating surface was confirmed by the X-ray diffraction technique. A reciprocating sliding method on a ball-on-flat system was utilized to evaluate the coating’s friction and wear behavior. Among the coatings with varying phosphorus content, a high hardness of 1086 HV was found for high-phosphorus coating when heat-treated at 400 °C in an air environment, and that was decreased to 691 HV when heat-treated at 650 °C. The oxidation of nickel in the electroless Ni-P coating occurred when heat-treated at 400 °C in an air environment, and this phenomenon was increased more when the temperature was increased to 650 °C. The characteristics of the NiO layer that formed on the surface of the heat-treated electroless Ni-P coating were influenced by the concentration of phosphorus, which caused different colors of NiO to be seen on the Ni-P coating surface. A greenish black NiO layer on the low-phosphorus and black NiO layer on the mid- and high-phosphorus Ni-P coating was developed during heat treatment at 650 °C in an air atmosphere. The adhesion and tribological characteristics of the Ni-P coatings were affected by the NiO layer developed on the heat-treated Ni-P coating surfaces. The Ni-P coatings with mid- and high-phosphorus content showed enhanced wear-resistance characteristics when they underwent heat treatment in an air atmosphere at the high temperature of 650 °C. The wear volume obtained for as-plated mid-phosphorus and high-phosphorus Ni-P coatings was 0.111 mm3 and 0.128 mm3, respectively, and that was reduced to 0.031 mm3 and 0.051 mm3, respectively, after the high-temperature heat treatment.

Zincate Replacement, an Economical a Sustainable Alternative for the Metal-Coating of Aluminum

Aluminum parts are of great value for many industries as they are cost-effective, very lightweight combined with a good mechanical strength. However, when parts are exposed to corrosive and abrasive conditions it is preferred to protect them with anodizing, powder coating, or for technical critical applications with nickel-phosphorus (NiP) coatings. Most preferred for functional parts such as scroll compressors, connectors,... is electroless NiP (EN) as it is has a low thickness variation in the final deposit and does not need the application of current like galvanic NiP coatings.Depositing an adherent layer of electroless NiP onto aluminum needs an alloy-specific pre-treatment. The largest challenge in pre-treatment lies in the very fast formation of Al2O3 oxide under neutral pH conditions of 4 - 9. For decades a very effective way to inhibit the re-oxidation of aluminum is the use of alkaline zinc as interim coatings that dissolve in the electroless NiP electrolyte before NiP deposition starts. Commercial solutions are optimized to produce an as thin and homogenous as possible zinc deposit to minimize the drag-in of zinc into the NiP electrolyte. At levels of 80 - 200 mg/l zinc starts to lower the adhesion and plating rate of deposited EN coatings. As results the nickel process needs to be discarded before nickel deposition capacity of electrolyte is fully reached (~ 40 g/l plated Ni). The impact of Zn contamination is most critical as lower the thickness of the EN layer is. At very thin thicknesses below 4 µm the increase of zinc is very large, and electrolytes need to be discarded at 6-12 g/l plated nickel creating higher chemical waste, maintenance effort, and cost. Due to technical changes in many applications, different and more parts will be composed of aluminum. In contrast to established applications NiP that exhibit EN layers > 5 µm new applications arise with the upcoming EV and Battery market that request thinner NiP layers. The most extreme case is reel-to-reel plating of thin (< 50 µm) foils with NiP deposits below 4 µm.In the present work, the application of a new chemical concept of aluminum pre-treatment for low-thickness EN coatings will be presented that reduces the number of needed process steps compared to double zincate by at least 2 steps (excl. rinses) without the need for special equipment such as pulse plating and others. Differences in the initiation of electroless NiP deposition and the correlated adhesion will be evaluated. As a model case, the application of thin NiP layers (< 4 µm) on pure Aluminum foils will be shown and discussed. Figure 1

Electroless Nickel Phosphorus Coatings to Mitigate the Corrosion of Construction Steel

Reinforced concrete is widely used in structures and construction, but its durability is limited due to corrosion of the embedded steel rebars. Thus, mitigation of corrosion of construction steel rebars is an important area of research. The present work reports the ability of electroless nickel phosphorus coating for corrosion protection of Fe-600-grade steel rebars used for construction purposes in chloride and sulphate environment. The coating deposited on Fe-600 rebar was Ni-P and was subjected to electrochemical tests in 3.5% NaCl and 0.5M H2SO4. Severe corrosion pitting and cracking were observed for the uncoated rebar while Ni-P coating showed nobler corrosion potential and low corrosion current density in the corrosive environments.

Impact of Die Coatings on Forming Conditions in Electromagnetic Embossing of Thin Sheet Metal

In electromagnetic embossing, the interaction of the magnetic field and the induced current density results in body forces that enable the replication of optical microstructures into thin sheet metals. However, as the sheet metal is completely penetrated by the magnetic field, electromagnetic properties of the dies need to be considered in process design, as they influence the forming conditions by changing the field distribution, force vectors and eddy current densities. With die coatings like electroless nickel–phosphorus (NiP), the electromagnetic properties of the die change. Therefore, the effect of both - die substrate and coating material - was studied to find advantageous conditions for electromagnetic embossing. Within two-dimensional electromagnetic field simulation, the electromagnetic properties of coating and substrate material were varied in addition to the coating thickness. To validate the results, electromagnetic embossing experiments were carried out. Here, different dies were fabricated from aluminum (uncoated) and cold work steel with 200 µm and 400 µm thick electroless nickel–phosphorus coatings that were subsequently micro-structured in optical surface quality. It was demonstrated by numerical and experimental results that the coating and the substrate influence the electromagnetic embossing significantly in correspondence to their shielding behavior and field interaction due to electromagnetic properties and coating thickness.

Investigations on Surface Behavior of Electro-Less Nickel Phosphorus Coatings with Nano Additives on Magnesium Alloy Used In Automotive Applications

To enhance the damage and corrosion behaviour for alloys, the coating is found because of the maximum fitted technique. Mg-based alloys have a good range of business application. These alloys show a high specific strength but bad attire and corrosion resistance. A standard coating of Cu, Ni &amp; Zn etc. provides a physical barrier against the wear and tear rate and corrosion attack of magnesium substrate. In the recent study, plating Ni-P was thru going on AZ91 composite by immersing samples into Nickel sulphate bath in the existence of surfactants. The study of the mechanism of Ni-P deposits was studied utilizing SEM. Ni-P coating was coated consistently within the existence of surfactants. Result of surfactant and Result of Nano-additives ZnO, Al2O3 and SiO with various quantities were examined. 0.5 g/l Nano Al2O3 additive-enhanced the deposition of Ni-P on AZ91 magnesium composite and hereafter the similar consequences are detected just in case of SiO accumulation. Effect of ZnO was also noticed. So is extremely clear that Ni-P coating is extremely effective to scale back the corrosion and rise the wear and tear behaviour if it's used together with Nano additive and therefore the surfactants.

Performance of Propargyl Alcohol as Corrosion Inhibitor for Electroless Nickel-Phosphorus (NiP) Coating in Hydrochloric Acid Solution

The electroless nickel-phosphorus (NiP) coatings have been used with great success in oil production equipment and accessories, such as pipes, valves, pumps, adapters, rings, connectors and various types of special tools. In the acidification or acid stimulation of oil wells, to increase their productivity, a hydrochloric acid (HCl) solution is preferably injected from concentrations of 5 to 28%, aiming at the dissolution of a reservoir rock constituted of limestone and dolomite. In addition, the HCl solutions are also used to remove lime scale adhering to carbon steel pipes, where propargyl alcohol as a corrosion inhibitor, has shown good anticorrosion protection. The aim of this work is centred on the laboratory evaluation of NiP coating in 5% and 10 % HCl solution, and addition of propargyl alcohol as a corrosion inhibitor. The mass loss and polarisation curves proved to be very promising with propargyl alcohol as a corrosion inhibitor.

Effect of heat treatment on the microstructure and mechanical properties of electroless nickel-phosphorus coatings

Electroless deposition have been considered as one of the most important nickelbased coating synthesization methods because of their coatings uniformity, high wear resistance, excellent corrosion and electrical properties. In this paper, nickel-phosphorus coatings were synthesized by electroless method on medium carbon steel substrates. The effect of heat treatment on the microstructure and mechanical properties of nickel-phosphorus coatings were investigated in detail. Structural analyses suggest that the coatings remain amorphous structure if the annealing temperature is below 400 °C. The crystalline Ni and Ni3P were formed in the coatings when the annealing temperature reach 400 °C and the grains grown significantly with increasing the heat treatment temperature from 500 °C to 800 °C. The mechanical properties of the nickel-phosphorus coatings display a significant change with the different heat treatment temperature. It was found that the highest microhardness value and the best wear resistance property has been obtained under heat treatment temperature of 400 °C. The possible mechanism of the relationship between microstructure and mechanical properties was also explored.

Study on corrosion behavior of TWIP steel and properties of surface electroless Ni-P coatings

In this study, the corrosion behavior and corrosion resistance of TWIP (Twinning Induced Plasticity) steels in the industrial atmospheric environment were studied by dry-wet cycle immersion test and electrochemical experiments. The results showed that the corrosion rates of TWIP steel gradually decreased with the increase of corrosion time. A layer of corrosion products was formed on the surface of TWIP steel during alternating immersion accelerated corrosion process, whose main components were Fe3O4 and α-FeOOH. With the prolongation of corrosion time, the rust layer on the surface of TWIP steel had a certain protective effect on the steel matrix. The adherent and defect-free electroless nickel–phosphorus (Ni-P) coatings were prepared on TWIP steels. Electrochemical test results showed the corrosion current density of the coating was about six times lower than that of TWIP steel substrate, indicating that the coating effectively improved corrosion resistance of TWIP steel and protected the steel substrate from erosion of corrosive ions. Additionally, the surface microhardness of TWIP steel was significantly increased after electroless Ni-P plating treatment.

Surface Interactions between Water-in-Oil Emulsions with Asphaltenes and Electroless Nickel-Phosphorus Coating.

Surface interactions between emulsion drops and substrate surfaces play an important role in many phenomena in industrial processes, such as fouling issues in oil production. Investigating the interaction forces between the water-in-oil emulsion drops with interfacially adsorbed asphaltenes and various substrates is of fundamental and practical importance in understanding the fouling mechanisms and developing efficient antifouling strategies. In this work, the surface interactions between water drops with asphaltenes and Fe substrates with or without an electroless nickel-phosphorus (EN) coating in organic media have been directly quantified using the atomic force microscope drop probe technique. The effects of asphaltene concentration, organic solvent type, aging time, contact time, and loading force were investigated. The results demonstrated that the adhesion between water drops and the substrates was enhanced with higher asphaltene concentration, better organic solvent to asphaltenes, longer aging time, longer contact time, and stronger loading force, which was due to the growing amount and conformational change of asphaltenes adsorbed at the water/oil interface. Meanwhile, the adhesion between the water drop and the EN substrate was much weaker than that with the Fe substrate. The bulk fouling tests also showed that EN coating had a very good antifouling performance, which was in consistence with the force measurement results. Our work sheds light on the fundamental understanding of emulsion-related fouling mechanisms in the oil industry and provides useful information for developing new coatings with antifouling performances.

Investigation of the Antifouling Mechanism of Electroless Nickel–Phosphorus Coating against Sand and Bitumen

Antifouling coatings have attracted much attention in applications of industrial equipment and systems. The accumulation of foulants on downhole equipment used in the steam-assisted gravity drainage process for oil sand extraction reduces the recovery efficiency of bitumen and causes failures of the equipment. Applying suitable coatings is expected to endow antifouling property to the related substrate surface. Understanding the interaction mechanism between foulants and antifouling coating is critical for the evaluation and prediction of antifouling performance. In this work, antifouling coating consisting of Ni and P was prepared on the L80 carbon steel substrate, which is a commonly used material in downhole equipment. The surface properties (e.g., morphology and surface energy) of the Ni–P coating and pristine L80 substrates were characterized. The intermolecular and surface forces between typical foulants (e.g., silica and bitumen-coated silica) and Ni–P coated and uncoated L80 substrates were directly measured using the atomic force microscope colloidal probe technique to investigate the fouling mechanisms and predict the fouling behaviors of the foulants at the nanoscale. It was found that the Ni–P coating possessed lower surface energy, weaker attractive van der Waals interaction, and smaller adhesion to both silica and bitumen as compared to the uncoated L80 substrate. Bulk soaking experiments were also conducted accordingly which further demonstrated the antifouling performance of Ni–P coating against silica and bitumen, agreeing well with the surface force measurements. This work has improved the fundamental understanding of fouling behaviors of silica and bitumen and the antifouling mechanism of Ni–P coating at the nanoscale, with potential applications in many related processes in chemical and petroleum industries. The methodologies employed in this work can be readily extended for investigating fouling and antifouling mechanisms of different materials in various engineering fields.

Sliding wear characteristics of as-deposited and heat-treated electroless Ni-P coatings against AISI E52100 steel ball

In the present experimental study, the wear characteristics of as-deposited and heat-treated, nickel phosphorus (Ni-P) coatings were studied against bearing steel ball (AISI E52100) at ambient dry conditions using linear reciprocating tribometer. The Ni-P coatings were deposited on En24 grade steel using electroless acidic bath and subjected to heat treatment at 400 °C for 1 h under air atmosphere. The phase structure and surface morphology of the coatings were characterized using x-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), respectively. Grain size of the coatings was analysed using Scherrer technique. Heat-treated coatings showed 50% improvement in Vickers hardness compared to as-deposited coatings, which is attributed to the formation of Ni3P phase. The stable friction coefficient (∼0.21) and low specific wear rate (4.49E-05 mm3/N-m) were observed for heat-treated coatings in comparison to those of as-deposited coatings. Wear tracks were characterized using SEM and energy dispersive spectroscopy (EDS) in order to understand the wear mechanisms.

Probing the Interaction Mechanism between Oil-in-Water Emulsions and Electroless Nickel–Phosphorus Coating with Implications for Antifouling in Oil Production

Fouling issues are highly undesirable in oil industries, and stable water–oil emulsion is one of the major causes of fouling on pipelines, upgrading equipment, and other surfaces in oil production. Studying the interfacial interactions between emulsion drops and various metal substrates is of significant importance in the fundamental understanding of fouling mechanisms. In this work, surface force measurements using a drop probe atomic force microscope technique and fouling tests were applied to investigate the fouling and antifouling mechanisms of electron-beam-deposited iron substrates with and without electroless nickel–phosphorus (EN) coatings. The effects of oil or aqueous solution conditions have been systematically investigated, including the asphaltene concentration, salinity, pH, and presence of divalent ions. A theoretical model based on the Reynolds lubrication equation and augmented Young–Laplace equation has been applied to analyze the measured force profiles. Our results indicate that the at...

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.

Evaluation of commercial nickel–phosphorus coating for ultracold neutron guides using a pinhole bottling method

We report on the evaluation of commercial electroless nickel phosphorus (NiP) coatings for ultracold neutron (UCN) transport and storage. The material potential of 50μm thick NiP coatings on stainless steel and aluminum substrates was measured to be VF=213(5.2) neV using the time-of-flight spectrometer ASTERIX at the Lujan Center. The loss per bounce probability was measured in pinhole bottling experiments carried out at ultracold neutron sources at Los Alamos Neutron Science Center and the Institut Laue-Langevin. For these tests a new guide coupling design was used to minimize gaps between the guide sections. The observed UCN loss in the bottle was interpreted in terms of an energy independent effective loss per bounce, which is the appropriate model when gaps in the system and upscattering are the dominate loss mechanisms, yielding a loss per bounce of 1.3(1)×10−4. We also present a detailed discussion of the pinhole bottling methodology and an energy dependent analysis of the experimental results.

Mechanical and wear characterization of electroless nickel mono and bilayers and high boron-mid phosphorus electroless nickel duplex coatings

Abstract The mechanical and wear properties of electroless nickel monolayer, bilayers and duplex NiP/NiB coatings were investigated in the as deposited state. Bilayers and duplex coatings, constituted of two layer of 10 μm each, were prepared according to four distinct configurations (NiB/NiP; NiP/NiB; NiB/NiB and NiP/NiP). Single layer coatings from each electroless nickel bath with a thickness of 20 μm were also synthesized and analyzed in this work: mid phosphorous NiP (nickel-phosphorus) and high boron NiB (nickel-boron). The microhardness, roughness and wear resistance of electroless nickel duplex coatings were compared with electroless NiP and NiB coatings of similar thickness. The hardness characteristics of duplex coatings are really influenced by the high hardness of NiB coatings: the hardness of pure NiP coatings was 550 HV while the presence of NiB coating as underlayer allowed to reach 738 HV. SEM observations of the cross-sections of the nickel duplex coatings also reveal that coatings are uniform with proper compatibility between layers.

Investigation of the surface properties of heat treated electroless Ni–P coating

Electroless nickel phosphorus (Ni–P) coatings were synthesised from an acid chloride electrolyte. The synthesised coatings were heat treated at different temperatures, and the surfaces of the heat treated coating were characterised using scanning electron microscopy and X-ray diffraction. Adhesion, wettability, hardness and corrosion behaviour of the coatings were measured. The surface morphology showed the formation of a nano crystalline nickel matrix under heat treated condition. X-ray diffraction analysis of the heat treated samples revealed the recrystallisation of nickel and formation of Ni3P phase in the coatings. The wettabilty study showed that the as-deposited Ni–P coating is hydrophobic and wettability increases to a maximum of 70.8° contact angle for heat treated temperature of 400°C due to nano crystalline formation. The Rockwell C adhesion test revealed the presence of micro cracks with increase in heat treatment temperature, however the failure is within the acceptability limit. The micro hardness of the Ni–P coating increased with increase in heat treatment temperature. Corrosion potential of the Ni–P coating shifted to a positive potential under heat treated conditions owing to oxidation and precipitation of Ni3P phase. Decreased corrosion rate and corrosion current density (7.37–0.21 µA cm−2) is attributed to heat treatment at 400°C.

Study of Mechanical Properties of Electroless Nickel-Phosphorus Coatings with Influence of Surfactant on AZ91 Magnesium Alloy

Electroless Nickel-Phosphorus (ENi-P) coating is well-known in surface engineering techniques and is preferred in various mechanical, chemical and electronic industries view its extraordinary resistance to wear and corrosion. The paper summerizes the effect of surfactant on the mechanical properties of electroless Nickel-Phosphorus (Ni-P) alloy coating obtained from an acidic bath. The endeavor of this study is to analyse the influence of surfactant Ammonium Lauryl Sulfate (ALS) concentration on the microhardness, surface roughness and wettability of ENi-P deposit on AZ91 Mg alloy substrate. It was observed that there was significant improvement in the rate of deposition, microhardness and wettability, along with reduction in surface roughness (Ra) by addition of ALS surfactant in the chemical bath.

Indentation property and corrosion resistance of electroless nickel–phosphorus coatings deposited on austenitic high-Mn TWIP steel

A multilayer coating using electroless nickel-phosphorus (Ni–P) was applied on a twinning-induced plasticity (TWIP) steel containing nominally 25wt.% Mn and 3wt.% Al to improve the indentation hardness and corrosion properties. Microindentation tests with two different indenters, namely, a three-sided pyramidal Berkovich indenter and a ball indenter were performed to study the mechanical response, the indentation hardness and elastic modulus of the coatings in conditions: as-plated, and post treated (PT) at 350°C and 700°C for 1h. The deformation morphology underneath the indenters was examined using a scanning laser microscope. The results showed that Ni–P coatings could significantly enhance the surface hardness of the TWIP steel. Significant improvement in the corrosion resistance could be observed in a sulfuric acid solution for the Ni–P coated steel compared to the uncoated substrate TWIP steel.

Study on Structural Characterization of Surfactants Influence on Electroless Ni-P Deposits

A novel method to improve the amorphous phase of electroless Nickel-Phosphorus (EN) coatings is developed by adding surfactants to EN bath. The two surfactants namely sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) have significant influence on the structure of EN deposits. The EN coated samples were characterized using X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The XRD pattern of all the deposits indicated the presence of nano crystalline and amorphous phases. Addition of surfactants favors the formation of amorphous phase than its crystalline counterpart. The crystallite size was found to varyfrom 20 nm with no surfactant to 8 nm with addition of surfactants. From the TEM study, dark surfaces corresponding to the amorphous phase can be seen and the SAD pattern of the deposit confirms the predominance of this amorphous phase. This favors wear and corrosion resistance applications. The experimental results and analysis are reported in this paper.

Direct Electroless Plating of Iron-Boron on Copper

Amorphous nickel-based alloys such as nickel-phosphorus (NiP) are widely used in the electronics and surface finishing industries. However, the use of nickel is now regulated under the ‘Nickel Directive’ of the European Union. This necessitates the development of Ni-free materials as replacements to conventional electroless NiP coatings. In the present work, we report on the electroless deposition of amorphous iron-boron (FeB) coatings with potential for replacing NiP. Chemical bath deposition of Fe was first achieved by Ruscior and Croiala1; however, these investigators used a sacrificial aluminum anode which dissolved, thereby providing the electrons for Fe deposition. True electroless deposition of FeB, i.e., using a reducing agent as electron source rather than a sacrificial anode, was achieved only recently through the use of palladium (Pd) activation of the substrate2,3. The significant cost and process complexity associated with surface activation motivated us to study and develop a ‘DIRECT’ electroless process for FeB deposition on copper (Cu) without the need for Pd activation. Our direct electroless FeB process was observed to be highly sensitive to the reducing agent, i.e., borohydride (BH) concentration. Electrochemical polarization studies were conducted to understand why low BH concentration in the bath did not yield Fe deposition. The polarization curves corresponding to the two half reactions of Fe plating and BH oxidation are shown in Figure 1. The mixed potential theory4allows us to predict theoretical plating rates corresponding to the potential at which the reduction and oxidation current densities are equal (dashed lines). It is noted that borohydride oxidation on the substrate (Cu) is cathodically shifted compared to borohydride oxidation on Fe. This implies that, at low borohydride concentrations, Fe plating on Cu proceeds rapidly but is suppressed immediately after the substrate (Cu) is covered with a thin layer of Fe. This observation led us to investigate the oxidation kinetics of borohydride and its dependence on electrolyte composition and pH. It was determined that increasing the borohydride concentration of the bath enabled a substantial cathodic shift in the polarization curve for borohydride oxidation on Fe, as shown in Figure 2. The cathodic shift was also evident in the mixed potential during electroless FeB plating from this high-BH electrolyte. The cathodic shift ensured sustained plating of FeB even after the initial coverage of the Cu substrate by Fe. Cross-section SEM was conducted to characterize deposit properties such as the thickness and surface morphology. X-ray photoelectron spectroscopy (XPS) was used to determine film composition, which was around 69% Fe and 31% B. X-ray diffraction (XRD) confirmed a nano-crystalline structure similar to NiP. Materials characterization and electrochemical corrosion testing confirmed that the proposed direct electroless FeB plating process has the potential of enabling Ni-free coatings in a variety of applications requiring corrosion-resistant, hard, and highly solderable surfaces5.