Ni-Co Alloy Coatings Research Articles

Fabrication of superhydrophobic self-cleaning Ni-Co-MoS2/Ni composite coating

This work investigated the parallel magnetically assisted jet electrodeposition of Ni-Co-MoS2/Ni superhydrophobic composite coatings. As a comparison, the effect of the magnetic field on Ni-Co alloy coatings was analyzed. Then, micro/nano MoS2/Ni particles were further added to study the performance of Ni-Co-MoS2/Ni composite coatings under different concentrations of micro/nano particles. Research indicated that the Ni-Co-MoS2/Ni composite coating surface exhibits coral like micro/nano structures, and the micro/nano structures became denser as the concentration of micro/nano particles increased. The superhydrophobic composite coatings were obtained without any chemical modification reagents. The contact angle of the superhydrophobic composite coating was as high as 153.2° and the sliding angle was 8.7° when the amount of micro/nano particles was added at 5 g/L. The coral like micro/nano structures of the composite coating provided additional air cushion to support surface water droplets and exhibited excellent self-cleaning performance. In addition, the composite coating also showed excellent corrosion resistance and wear resistance, which was still relatively intact after friction, only exhibiting few wears on coral like micro/nano structures, it still maintained a good silver mirror effect after friction. This work suggested that parallel magnetically assisted jet electrodeposition could fabricate superhydrophobic composite coatings with excellent performance.

Effects of deposition current density, time and scanning velocity on scanning jet electrodeposition of Ni-Co alloy coating

Jet electrodeposition has superior application prospects in the preparation of nanostructured alloy coatings, which is suitable for high current density deposition and has selective deposition characteristics. The purpose of this work is to clarify the combined effect of multiple factors on the properties of alloy coatings prepared by jet electrodeposition. The L16 made by Taguchi orthogonal array was used in the experiment. The work studied the influence of process parameters such as deposition time (t), current density (i) and scanning velocity (v) on the properties of NiCo alloy coatings prepared on 304 stainless steel, which was set as the substrates. Material deposition rate (MDR), coating microhardness and coating surface roughness (SRa) were selected as the test indicators to characterize the coating properties. Analysis of Variance (ANOVA) was done to analyze the experimental data. The results indicated that current density had the greatest effect on MDR, coating microhardness and coating surface roughness, followed by deposition time and scanning velocity. The optimal parameters combination was selected, listed as follows: deposition time 20 min, current density 70 A·dm−2 and the scanning velocity 10 mm·s−1. The coating microhardness was 532.40 HV, coating SRa was as low as 85 nm, adhesion between coating and substrate was as high as 26.12 N and self-corrosion current density was 5.718 × 10−3 μA·cm−2 under the optimal parameters combination, which showed good performance. This processing method can guide the preparation of NiCo alloy coatings by jet electrodeposition, while the good performance exhibited by the coating can provide a reference for the anti-corrosion and wear-resistant treatment of marine equipment and textile machinery.

Effect of parallel magnetic field on growth and properties of jet electrodeposited Ni-Co-SiC composite coatings

Ni-Co alloy and composite coatings were fabricated by a parallel magnetic field-assisted jet electrodeposition (PMAJE), and the effect of nano SiC particles on the properties of Ni-Co alloy coating was studied. Crystal structure, micromorphology and 3D profile, microhardness, adhesion and corrosion resistance of the Ni-Co alloy and composite coatings were studied respectively. The deposition mechanism of Ni-Co alloy and composite coatings in PMAJE was analyzed. It was found that the parallel magnetic field (PM) significantly affected the surface morphology and flatness of Ni-Co alloy and composite coatings in jet electrodeposition. The microprotrusions of Ni-Co alloy and composite coating gradually increased with the magnetic flux density. PM refined the grain growth of Ni-Co alloy and composite coating when the magnetic flux density was 50 mT. Compared with jet electrodeposition, the Ni-Co-SiC composite coating exhibited a high mechanical properties and corrosion resistance in PMAJE. The microhardness of Ni-Co-SiC composite coating was 582.4HV, the adhesion was 27.2 N, the corrosion current density of Ni-Co-SiC composite coating was as low as 5.824 μA·cm−2 and the polarization resistance reached 6471 Ω·cm2, which was better than that of jet electrodeposition.

Development of Ni-Co-CNT composite coatings for corrosion protection of mild steel in 5% NaCl

In this report, corrosion resistance of Ni-Co-CNT composite coatings on mild steel was studied. The deposition step follows composite-electrodeposition technique. The effect of CNT nanoparticle on corrosion resistance behavior of Ni-Co alloy coatings on mild steel were studied. The Ni-Co bath contents such as electrolytes, stabilizer and additives were optimized by using Hull cell. The optimized amount of CNT particle in the bath was found to be 0.5g/L. The surface modification of Ni-Co alloy coatings in the presence of nanoparticle was studied interms of their corrosion resistance behavior. The Ni-Co-CNT composite coatings was developed at different current densities. The corrosion protection efficacy of the deposited coatings has been studied by using Tafel extrapolation and electrochemical impedance techniques. The Ni-Co-CNT coating was found to be more stable and results showed linear change of potential with time. The result depicted that deposited composite coating on mild steel at a current of 4.0Adm −2 was found to be more corrosion resistance as compared with other current density coatings. This was attributed to decrease of size of the particle with increase of current densities as confirmed by AFM analysis. The chronopotentiometry technique revealed that coating was found to be more stable for several hours at different current densities. The coating obtained at a c.d of 4.0A dm −2 was found be more stable towards corrosion and confirmed by Chrono potentiometric techniques.

Optimizing mechanical and tribological properties of electrodeposited NiCo alloy coatings by tailoring hierarchical nanostructures

NiCo alloy coatings were prepared via electrochemical deposition on low-carbon steel substrate. These coatings feature hierarchical nanostructures of ultra-fine grains (≈ 200 nm in size) with embedded high density of nano-twins, twin-stacking fault networks and/or martensitic bundle architectures, which were tailored by varying Co content. The nano-mechanical behaviors and dry-sliding tribological properties of the NiCo coatings were systematically investigated. The results reveal that formation of intersecting architectures with nano-twins and stacking faults/martensitic bundles considerably elevates the hardness of the coatings, as the plastic deformation is controlled by the interactions between the dislocations and the interfaces including grain boundaries, twin boundaries and phase boundaries. The presence of the transformation-induced plasticity (TRIP) effect in the dual-phase NiCo coating leads to a deviation from Archard scaling during dry-sliding. The optimized wear resistance exhibited by the dual-phase NiCo coating, corresponding to the lowest wear rate and wear coefficient, was discussed in terms of both the hardness and TRIP effect.

Effect of sodium dodecyl sulfate and different SiC quantities on electrodeposited Ni-Co alloy coatings

Ni-Co nanocomposites Prepared by electrodeposition in a modified Watts bath containing various quantities of silicon carbide SiC and the organic additive sodium dodecyl sulfate SDS as a surfactant. The influence of nanoparticle incorporation on the electrodeposit microstructure, mechanical characteristics, and deformation process was studied. Vickers micro-hardness and weight loss tests were used to study the mechanical properties and morphology. The microstructure has also been analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Co-deposition of uniformly dispersed SiC particles, on the other hand, was found to improve the extreme tensile strength of the deposits significantly; SDS lowered the surface tension, allowing the SiC particles to fill in all remaining gaps to achieve a homogeneous surface. A process involving atoms that can dramatically improve flexibility. The incorporation of SiC particles and raising the strain rate encouraged a ductile fracture mode in a nano-crystalline Ni-Co matrix, which demonstrated a mixed mod behavior of flexible and brittle fracture; it was evident that the addition of SDS increases the concentration of SiC particles in general on Ni-Co samples. Moreover, compare Ni-Co with various amounts of SiC and Ni-Co/SiC with adding SDS. Furthermore, to achieve the highest possible electroplating efficiency.

Anomalous codeposition of NiCo alloy coatings and their corrosion behaviour

Here, we report the electrodeposition NiCo alloy coatings from a new bath using the glycine, as additive. A bright and uniform coatings NiCo alloy have been developed at different current densities and their corrosion performances have been evaluated. The surface morphology, composition and phase structure of alloy coatings have been analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) techniques, respectively. The compositional information of NiCo alloy coatings revealed that the proposed bath follows anomalous type of codeposition over range of current density studied (1.0–4.0 A dm−2), by demonstrating more Wt. % of Co in the deposits, than in the bath. A constant increase in the Wt. % of Ni with current density was found, supported by XRD analyses; and it may be attributed to the depletion of more readily depositable Co+2 ions at cathode film by following the principle of codeposition of NiCo alloy. The corrosion study revealed that NiCo alloy deposited at 4.0 A dm−2, represented as (NiCo) 4.0 A dm-2 coating is the most corrosion resistant compared to all other coatings. The highest corrosion stability of (NiCo) 4.0 A dm-2 alloy attributed to its highest Ni content (38.6 wt%) and increased surface smoothness, supported by EDS and SEM study.

Sic-Yag Composite Reinforced Ni-Co Alloy Coatings Produced by Hvof Thermal Spray: Characterization and Wear Behaviour at Room and High Temperature

Sic-Yag Composite Reinforced Ni-Co Alloy Coatings Produced by Hvof Thermal Spray: Characterization and Wear Behaviour at Room and High Temperature

Sic-Yag Composite Reinforced Ni-Co Alloy Coatings Produced by Hvof Thermal Spray: Characterization and Wear Behaviour at Room and High Temperature

Sic-Yag Composite Reinforced Ni-Co Alloy Coatings Produced by Hvof Thermal Spray: Characterization and Wear Behaviour at Room and High Temperature

The effect of deposition potential on the structure and performance of the Ni-Co multilayer nanocrystalline coating

The effect of different deposition potential for electrochemical additive manufacturing prepared the nano-multilayer Ni-Co alloy coating was investigated. The Ni-Co alloy coatings are FCC structures according to XRD analysis. As the potential becomes negative, the weight ratio of Ni in the plating layer increases, and the thickness of the plating layer also increases. Meanwhile, the more negative potential reduces the crystallite size (between 15 nm and 44 nm) and increases the hardness of the Ni-Co coating. The corrosion tested for 3.5 wt% NaCl showed that the thinner multilayer structure will suffer significant penetration corrosion, and the thicker multilayer structure can slow down the penetration corrosion.

Effect of Annealing Temperature on Microstructure and Hardness of Ni-Co Alloy Coating

The effect of annealing temperature on microstructure and hardness of Ni-Co alloy coating electroplated on a Cr-Ni-Mo-V steel was investigated using the combination of micro-Vickers hardness tester, electron backscatter diffraction (EBSD) and energy dispersive spectrometer (EDS). It was found that the hardness of Ni-Co alloy coating drops suddenly at annealing temperature increased up to 350 °C, then gradually decreases with increasing annealing temperature. The microstructural characterizations suggested that the grains start to merge and grow in Ni-Co alloy coating at annealing temperature of 350 °C which leads to a decrease in the amount of grain boundaries, thus the initial dislocation density lowers when annealing temperature up to 650 °C. The formation of the Ni-Co oxidation was considered to be the second factor giving rise to the reduction in hardness with annealing temperature.

Synthesis and characterization of TiN nanoparticle reinforced binary Ni-Co alloy coatings

In the present work, TiN nanoparticle reinforced Ni-Co alloy coatings have been synthesized by pulse current electrodeposition under the assistance of magnetic and ultrasonic agitation. Various analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) were used to explore the effects of current densities and agitation modes on the coating composition, morphology and structure of the electrodeposits. The corrosion resistance of the composite coating was examined by electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. The electrodeposits prepared under magnetic stirring exhibit nodular-protrusion morphology. The ultrasonic-assisted electrodeposited Ni-Co/TiN coatings are flatter, finer, and denser compared to that of magnetic stirring. The agitation mode affects the Co and TiN content in the composite coatings. The preferred orientation was (111) texture, which was gradually changed to (200) plane as the current density increased. The crystallite size was 14–17 nm, 11–14 nm for the magnetic and ultrasonic-assisted electrodeposited Ni-Co/TiN coatings, respectively. The roughness of the samples prepared under ultrasonic agitation was lower than that of magnetic stirring. EIS measurements show that the composite coating prepared at 6 A dm−2 under ultrasonic assistance exhibits the best corrosion resistance with maximum Rct during the whole immersion period. The ultrasonic-assisted electrodeposited Ni-Co/TiN coating has a denser structure and better corrosion resistance than that prepared under mechanical stirring.

Electrodeposited Ni-Co Films from Electrolytes with Different Co Contents

Ni–Co alloy coatings were electrodeposited at various cobalt amounts on pretreated steel substrates. The co-deposition phenomenon of Ni-Co alloys was described as anomalous behaviour. Different techniques including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray diffraction (XRD) and potentiodynamic polarization were used to characterize the alloy coatings. EDX results showed that the Co content increase with the enhancing of Co amount. SEM images have shown that the increase of Co amount leads grain developing from large grain to branched grain form and that goes through spherical and pyramidal, this implies that the grain size of these alloy coatings is greatly affected by Co amount in the electrolyte baths. XRD patterns revealed that the phase structure of Ni–Co coatings is dramatically changed from fcc into hcp structure with the increase of Co amount. The electrochemical properties of Ni-Co alloy coatings evaluated in 3.5% NaCl solution reveal that Ni–34.32 wt.% Co alloy exhibits better corrosion resistance compared to pure Ni and other Ni–Co alloy coatings.

Nickel-cobalt alloy coatings prepared by electrodeposition Part II: Morphology, structure, microhardness, and electrochemical studies

A study was carried out to synthesize Ni-Co alloy coatings electrochemically from complex acidic glycine (gly) bath. The impacts of some operating parameters such as Co2+ to Ni2+ concentration ratios in the bath, gly concentrations, pH, applied current, plating time and temperature on the morphology of Ni-Co alloy were investigated. The microstructure, microhardness, and electrochemical studies were also investigated. The electrochemical studies utilized cyclic voltammetry, anodic linear stripping voltammetry, and potentiostatic current-time transient techniques. It was realized that gly lowers the cathodic overvoltage for the Co2+ deposition while promoting cathodic overvoltage of Ni2+ deposition. Accordingly, the concurrent codeposition of Co2+ and Ni2+ ions was simplified. The morphology of Ni-Co alloy is significantly dependent on the operating parameters rather than on the bath composition. Moreover, increasing either pH or bath temperature produces Ni-Co deposits free from cracking. The roughness of the alloy is decreased in the presence of gly as shown by the atomic force microscope (AFM) study. In the presence of gly, the microhardness increases from 387 to 970 kg f mm−2, i.e., it increased more than two-and-a-half times. On the other hand, X-ray diffraction analysis (XRD) data show that the crystallinity decreases with enhancing the percentage of cobalt in the deposits.

Electrodeposition of Ni-P/Ni-Co-Al2O3 duplex nanocomposite coatings: towards improved mechanical and corrosion properties

ABSTRACT Ni-Co alloy and composite coatings offer improved engineering properties such as hardness, wear resistance, and corrosion protection. The emphasis of this evaluation has been put on improvement of mechanical and corrosion properties of Ni-Co deposits by inclusion of the appropriate loadings of Al2O3 nanoparticles along with deposition of Ni-P interlayer. For this goal, a broad range of Al2O3 nanoparticles loadings, 0–80 g L−1, were incorporated into the Ni-Co alloy electrolyte to define precisely the optimum condition in terms of mechanical and corrosion performance. The inclusion of 60 g L−1 Al2O3 nanoparticles enhanced the microhardness and charge transfer resistance of Ni-Co alloy deposit by 244 HV and ≈5 kΩ, respectively. The influence of Ni-P interlayer on the characteristics of the Ni-Co-60 g L−1 Al2O3 coating was also assessed. A further increase in the abovementioned properties by 88 HV and ≈8 kΩ was obtained when a Ni-P interlayer was deposited between St 37 steel substrate and Ni-Co-60 g L−1 Al2O3 coating.

Ultra-low-power preparation of multilayer nanocrystalline Ni[sbnd]Co binary alloy coating by electrochemical additive manufacturing

Using the principle of electrochemical additive manufacturing (ECAM), a nanocrystalline NiCo binary alloy coating was prepared on the surface of the steel substrate. This study shows the pulse-shaped current-time curve of ECAM during the coating preparation process, and the nanocrystalline NiCo coating has a regular multilayer structure. At the same time, the ECAM method can effectively limit the growth time of the crystal nucleus and prepare nanocrystalline NiCo alloy coatings with ultra-low energy consumption (5.75 × 10−3 W). Besides, as the content of Co in the coating increases, the NiCo alloy coating changes from an FCC single-phase structure to an FCC + HCP multi-phase structure. Finally, through the performance test of the nanocrystalline NiCo coating, it is concluded that as the content of Co in the coating increases, the hardness of the coating increases, and the coating surface has a certain degree of hydrophobicity (100°–114°). The electrochemical corrosion test shows that the NiCo coating has better corrosion resistance than the steel substrate. As the content of Co in the coating increases, the corrosion current density of the NiCo coating increases from 9 μA/cm2 to 32 μA/cm2.

Nickel-cobalt alloy coatings prepared by electrodeposition Part I: Cathodic current efficiency, alloy composition, polarization behavior and throwing power

A systematic study was carried out to electrodeposit Ni-Co alloy coatings from a complexing acidic glycine bath on copper substrates. The effects of [Co2+]/[Ni2+] ratio, gly concentration, pH, current density and temperature on the current efficiency, Co content in the coatings and on polarization behavior were investigated. It was found that the CCE of these baths has a wide range starting from 55% up to a maximum value of 99.3%, relying on the operating parameters and the bath constituent. However, the CCE decreased from 96.2% to 84.8% when the gly content was enhanced from 25 to 150 g/L. On the other hand, the Co content in the deposit reached 97% (wt%) at [Co2+]/[Ni2+]=0.43, i= 16 mA cm2, t=10 min, T=20 °C. The codeposition of Co and Ni from acidic gly baths obeys the anomalous type of codeposition. The kinetic results indicate that the Tafel slope increased in the case of alloy deposition, while both the transfer coefficient αc and the exchange current i° decreased. Moreover, the obtained results indicated that increasing the Co2+ content in the electrolytic solution has an inhibiting impact on the kinetics of the nickel-cobalt alloy plating. The throwing power is enhanced with enhancing [Co2+]/[Ni2+] ratios, while the addition of gly decreases it. However, the outcomes of macrothrowing power, throwing index and Wagner numbers are in excellent accord.

The influence of electrodeposited Ni-Co alloy coating microstructure on CO2 corrosion resistance on X65 steel

Electrodeposited Ni-Co alloy coatings are investigated for the protection of X65 carbon steel in sweet (CO2) corrosion environments. Two coatings having different microstructures, but similar cobalt contents, were fabricated to investigate the microstructural influences on CO2 corrosion resistance. Experimental results show that the fibre-like Ni-Co micro-structured coating offers a corrosion resistance that is 2 orders of magnitude greater than the cone-like coating. This strong effect of microstructure is believed to arise from the larger surface/solution contact area, the higher density of grain boundaries and active defects, and the lower protective oxide content on surface of the cone-like Ni-Co coating.

Electrochemical behavior and electrodeposition of Ni-Co alloy from choline chloride-ethylene glycol deep eutectic solvent

In this work, nickel-cobalt (Ni-Co) alloy was prepared in choline chloride-ethylene glycol deep eutectic solvent by deposition. Metal ion complex structure and stability were studied using UV–Vis. The electrochemical behavior in different metal salts was studied by voltammetry (CV) and chronoamperometry (CA). The corrosion resistance was studied using potentiodynamic polarisation and electrochemical impedance (EIS). Surface and phase composition of Ni-Co alloy coatings were characterized by scanning electron microscopy (SEM/EDS) and X-ray diffraction (XRD). The results from the voltammetry showed that the reduction peak appear among −0.6 V ∼ −1.13 V, which belonged to Ni-Co codeposition. The reduction of Ni-Co alloy in the CE was an irreversible process under diffusion control. Chronoamperometric results indicated that the electrodeposition of Ni-Co on a glassy carbon electrode followed the mechanism of instantaneous nucleation and three-dimensional growth. The results of microstructure and phase composition showed that the control of deposition potential could effectively control the microstructure and Co content of Ni-Co alloy. Nano crystal structure could be obtained with a grain size in the range of 3.1–4.0 nm. Comparison in the corrosion behaviour of the coatings showed that the change of Co content had an effect on the corrosion resistance of Ni-Co alloy.

Effect of current density and cobalt concentration on the characteristics of Ni[sbnd]Co coatings prepared by electrodesposition with a supergravity field

A supergravity field offers several advantages during electrodeposition. Electrodeposition assisted by a supergravity field was employed to produce nickel–cobalt (NiCo) alloy coatings. The grain size, surface morphology, preferred crystal orientation, microhardness and wear resistance of the deposited NiCo coatings were studied systematically, and all were found to be dependent on the Co concentration in the plating bath and current density. Under a supergravity field, the surface morphology was found to be smoother than that obtained in a normal gravity field. Grain sizes of the as-prepared NiCo coatings were refined, and an average grain size of 15 nm was obtained. A Co content of 40.56 wt% was obtained using a low Co concentration in the bath. NiCo alloy coatings with a maximum microhardness of 660 HV were prepared, and the hardness value was significantly higher than that for coatings prepared by conventional electrodeposition. A minimum friction coefficient of 0.14 and a very low wear weight loss of 2.5 mg were achieved in our experiments.