Citrate Bath Research Articles

Preparation, corrosion, and wear resistance of Ni‐Mo/Al composite coating reinforced with Al particles

In this research, Ni‐Mo/Al composite coatings were deposited from a citrate bath containing Al metallic particles. The impact of Al particle content in the bath on the microstructure, texture, thickness, current efficiency, wear and corrosion behaviors of Ni–Mo/Al coatings was surveyed. The [200] preferred orientation developed slowly to the [111] orientation with increasing Al loadings in the bath. The results showed that electroplating at 40°C and citrate ion concentration of 0.15M had the highest current efficiency and produced a dense coating free of cracks. Because of the presence of Mo, the morphology of the matrix changed from a regular pyramidal structure for Ni‐Al composite coatings to cauliflower for Ni‐Mo/Al composite coatings. The wear resistance of coatings decreased due to the increase of Al content in the coating. The polarization tests indicated that the corrosion resistance of the Ni‐Mo/Al composite coating was enhanced by adding Al metal particles. This was due to the increase of Al content and decrease of the grain size of the coatings.

Induced codeposition of Ni-W alloy coatings using glycerol as additive and their characterization

As a promising coating material to replace hard chromium coating, the development of nickel–tungsten (Ni-W) alloy coatings of good corrosion protection is of great interest in surface coating technology. Further, the effect of plating variables, including additive on the composition of alloys of induced co-deposition is more vagarious than in other types of alloy deposition. In this regard, an alkaline citrate bath has been formulated for electrodeposition of Ni-W alloy through conventional Hull cell method, using glycerol as additive. Electrodeposition following the induced type of codeposition of Ni–W alloy was carried out onto mild steel (MS) substrate at different current densities (c.d.’s) at room temperature, taking a basic bath. Influence of bath constituents and operating parameters on the appearance, hardness, thickness and composition of the deposits were studied as a measure of their performance against corrosion. Corrosion behaviours of Ni-W coatings, having hard-adherent mirror bright appearance were studied using Tafel’s polarization and electrochemical impedance spectroscopy (EIS) method in 5 wt. % NaCl solution. Experimental results revealed that corrosion protection efficacy of Ni-W coatings increased with deposition c.d., in proportion of its W content. The coating developed at 4.0 A dm-2 was found to exhibit the least corrosion rate (5.3 x 10-2 mm y-1), compared to those at other c.d.’s. The process and product of electrodeposition have been studied using different instrumental methods, such as Cyclic voltammetry (CV), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) study. Experimental observations were analyzed in the light of induced codeposition of Ni-W alloy due to stimulation by Ni+2 ions, and results are discussed.

Optimization of CuW alloy electrodeposition towards high-tungsten content

With the help of the factorial design of experiments, optimization of the deposition of the CuW alloy was successfully done. The important deposition parameters were identified as pH, current density, and—the most important one—copper ion concentration. All of them were examined in their wide ranges. Under optimal conditions, in a citrate bath, with copper ion concentration of 1.0 mM, at current density of −100 mA cm−2 and at pH ca. 8.3, the alloy layer had the highest tungsten content (circa 30 wt.%), satisfactory adhesion and a smooth and crackless morphology. The structure of the electrodeposited alloy can be described as an amorphous solid solution of Cu in W with built-in Cu nanocrystals.

THE ELECTROCHEMICAL BEHAVIOR OF Zn–Mn ALLOY COATING IN CARBONATED CONCRETE SOLUTION

In order to improve the protective performance of Zn coating on reinforcing steel in concrete, the electrochemical deposition of Zn–Mn coatings was conducted on steel surface. The morphology, chemical and phase compositions of Zn–Mn coatings obtained from sulfate–citrate bath were investigated in the first part of paper. In the second part, the obtained deposits were tested in solution simulating carbonated concrete, consisting of NaHCO3 and Na2CO3. Data obtained from Tafel analysis showed higher corrosion resistance for Zn–Mn alloy deposits obtained at –1700 and –1800[Formula: see text]mV versus SCE, when compared to pure Zn deposit. Impedance spectroscopy investigations revealed that the total impedance of Zn–Mn coatings increased steadily with time, and was significantly higher as compared to pure Zn after 24[Formula: see text]h in corrosion solution. On the contrary, for pure Zn, the impedance increased in the first 12[Formula: see text]h, and then decreased during prolonged exposure time, which can be explained by rapid growth of nonprotective white rust and the degradation of zinc coating, as was confirmed by optical microscope after 24[Formula: see text]h of immersion in carbonated concrete pore solution.

Electrochemical synthesis of ZnTe thin films from citrate bath and their electrical properties with incorporation of Cu

ZnTe and ZnTe:Cu thin films were electrochemically synthesized, and their electrical properties were systematically investigated. Electrochemical redox reactions of ionic species were identified by cyclic voltammetry, presenting the underpotential deposition (UPD) of Zn on Tesite occurred in the potential range of −0.6 to −1 V vs. Ag/AgCl. ZnTe thin films electrodeposited at 80 °C showed polycrystalline phase with strongly preferred to (111) direction observed by XRD. XPS analysis also indicated that there were no other phases in ZnTe films. Incorporation with Cu was performed using an electrodeposition bath containing Cu precursor, Cu(NO3)2, and the amount of incorporated Cu was varied with concentration of the Cu precursor. A significant increase in carrier mobility (∼1 cm2/Vs) and concentration (∼1018/cm3) compared to undoped ZnTe thin films was achieved.

Electrodeposition of Zn-Mn-Mo layers from citrate-based aqueous electrolytes

The first stage of this work involved the development of stable baths for electrodeposition of Zn-Mn-Mo alloys, on the basis of thermodynamic models of citrate baths. Then, the kinetics of co-reduction of Zn(II), Mn(II) and Mo(VI) from aqueous citrate solution were studied. Partial polarisation curves were determined. The influence of applied potential, hydrodynamic conditions, and electrolyte composition on the electrodeposition of Zn-Mn-Mo layers was determined. Surface composition of deposits was ascertained by chemical analysis (WDXRF). The morphology of coatings was studied by SEM. The phase composition of Zn-Mn-Mo samples was determined by Raman spectroscopy. Electrolysis parameters allowing electrodeposition of Zn-Mn-Mo coatings containing various amounts of Mn and Mo were described. The manganese content varied from 0.1 to 20.5wt.%, and the molybdenum content reached up to approximately 7.1wt.%. The electrodeposition of homogeneous, compact, pore-free Zn-Mn-Mo coatings on steel is possible from the citrate baths studied. Raman spectroscopy also revealed the presence of Mn and Mo solution in the Zn hexagonal phase. In addition, the ZnO, MoO2, Zn1-xMn2+xO4 on the surface of the deposits, which may be the products of chemical processes taking place simultaneously with electrolysis, were observed.

Pulsed cobalt-rich Zn–Co alloy coatings produced from citrate baths

Abstract Zn–Co alloy coatings deposited by pulsed current (PC) typically exhibit higher adhesion, lower porosity and smaller grain size than those deposited by direct current (DC). All of these features contribute to the improved anticorrosive performance observed in PC Zn–Co coatings. Additionally, an increase in cobalt content in Zn–Co coatings tends to decrease the material's grain size, which may influence the anticorrosive performance of the coating. Therefore, the present study investigates the deposition of anticorrosive cobalt-rich Zn–Co coatings on carbon steel using PC deposition. The electrodeposition process was executed under stirring conditions using baths containing Zn (II) ions (0.05 mol L − 1 ), different Co (II) concentrations ([Co 2 + ] = 0.05 and 0.10 mol L − 1 ) and sodium citrate (0.10 mol L − 1 ) as the complexing agent. Four current densities ( j c ) and three pulse frequencies ( F ) were applied to produce the alloys. It was observed that the deposition process was anomalous under all of the studied conditions. Higher contents of cobalt were verified at higher current densities for both Co (II) concentrations, particularly at smaller pulse frequencies. The anticorrosive performance of the Co-rich Zn–Co coatings appears to depend on the relationship among the parameters j c , [Co 2 + ] and F , because their joint effect influenced the chemical composition, thickness and microstructure of the coatings. In the current study, the best anticorrosive performances were observed for coatings containing 7.4 to 13 wt.% Co, presenting nanometric grain size and one predominant crystalline phase (γ-Zn 21 Co 5 ). These coatings showed a high stability in an aggressive environment for 24 h of exposure, thus indicating that they could be useful as long-term corrosion protection coatings.

Electrodeposition of nickel–phosphorus from a highly conductive citrate bath for wire bonding applications

A highly conductive electrolytic nickel–phosphorus (Ni–P) plating bath was formulated as an alternative to electroless Ni–P deposition for aluminium wire bonding application. The Ni–P deposits were electroplated from nickel citrate baths containing sodium chloride, citric acid, nickel sulphate and sodium hypophosphite (SHP) using the DC plating. In comparison with Watts bath, the formulated highly conductive citrate bath had almost twice of cathodic current efficiency in low-current density regions and exhibited more uniform plating thickness. In addition, the formulated citrate bath did not have any boric acid as a component; and hence, eliminating the waste disposal issue related to boric acid.

Microstructure and Magnetic Properties of Electrodeposited Ni85.8Fe10.6W1.4Cu2.2 Alloy Powder

Nanostructured 85.8 wt%Ni–10.6 wt%Fe–1.4 wt%W–2.2 wt%Cu alloy powder was deposited from an ammonium citrate bath at a current density of 600 mAcm−2. A cathodic polarization curve was recorded, and the current efficiency of the alloy was determined as a function of current density. The deposition of the alloy at current densities up to 400 mAcm−2 is an activation-controlled process. At higher densities, diffusion control is attained. At potentials more positive than −0.90 V, hydrogen evolution from NH4+ and (HCit)3− ions occurs in parallel with the alloy deposition. XRD analysis revealed an amorphous matrix embedded with nanocrystals of the FCC phase of the solid solution of iron, tungsten and copper in nickel. SEM micrographs showed the formation of two shapes of particles: large cauliflower-like particles and small dendritic particles with a large number of secondary and higher-order branches. The annealing of the as-deposited powder causes structural changes which consequently affect its magnetic properties. In the temperature range of 150°C–460°C, structural relaxation takes place, involving short-range ordering and an increase in the relative magnetic permeability of the cooled sample. At temperatures above 460°C, amorphous matrix crystallization and crystalline grain growth of the FCC solid solution occur, resulting in a decrease in the magnetic permeability of the powder.

Synthesis, structure and properties of nickel-iron-tungsten alloy electrodeposits - Part II: Effect of microstructure on hardness, electrical and magnetic properties

Nanostructured nickel-iron-tungsten alloys were produced by electrodeposition from an ammoniacal citrate bath. The tungsten content of the alloy ranged from 0.8 wt.% to 11 wt.%, and the crystal grain size of the FCC phase of the solid solution of iron and tungsten in nickel was between 14 nm and 3.3 nm. The amorphous phase content of the alloy increases with decreasing crystal grain size. As the amorphous phase content increases, the magnetization, electrical conductivity and hardness of the alloy decrease. Annealing the alloy to crystallization temperature results in structural relaxation during which the alloy undergoes short-range ordering in conjunction with decreases in the density of chaotically distributed dislocations and internal microstrain level, which increases the exchange integral value, the electronic density of states at the Fermi level, the mean free path of electrons, the ordering and the mean size of cluster in the sliding plane and results in more uniform orientation of dipole moments of certain nanoparticles. These changes: a) increase the mobility of magnetic domain walls, facilitate the orientation of domains in the external magnetic field and cause an increase in magnetization; b) cause a decrease in electrical resistance, and c) impede the sliding of grain boundaries and increase the hardness of the alloy. Annealing the alloys at temperatures above 400?C results in amorphous phase crystallization and larger crystal grains of the FCC phase, along with a decrease in the density of chaotically distributed dislocations and a decrease in internal microstrain level. The formation of larger crystal grains reduces the hardness of the alloy, decreases its specific electrical resistance and impedes both the orientation of certain magnetic domains and the shift of walls of already oriented domains, thus inducing a decrease in magnetization. The heat released during the milling of Ni87.3Fe11.3W1.4 alloy with FCC-phase crystal grains 8.8 nm in average size causes amorphous phase crystallization, FCC crystal grain growth and an increase in magnetization. Alloys with relatively high tungsten content (11 wt. %) have an inhomogeneous composition, a high proportion of the amorphous phase and FCC crystal grains with an average size of 3.3 nm. This microstructure results in magnetic domains that have different and relatively low thermal stabilities and relatively low degrees of magnetization.

Effect of ultrasonication on Ni–Mo coatings produced by DC electroformation

The effect of the ultrasound-assisted method on Ni–Mo alloy coatings by direct current (DC) electroformation in a sulphate–citrate bath was investigated.

Electrodeposition of 70-30 Cu–Ni nanocomposite coatings for enhanced mechanical and corrosion properties

A copper-nickel alloy (70:30 ratio) was electrochemically deposited and compared to a composite coating incorporating layered silicate platelets to obtain copper-nickel-montmorillonite (MMT). The composite coatings were electrochemically deposited from a citrate bath to investigate the effects of MMT on the corrosion and mechanical properties of the coatings. Incorporation of MMT into the Cu–Ni alloy films was not affected by the deposition parameters such as applied voltage and pH. Scanning electron microscopy and atomic absorption spectroscopy confirmed the successful incorporation of the MMT into the coatings. Longer term stability in the presence of corroding solutions was noted for the copper-nickel composite films. The Tafel calculations showed an increase in polarization resistance, Rp, from 190.7 kΩ·cm2 for pure Cu–Ni to 314.3 kΩ·cm2 for Cu–Ni-0.2% MMT after soaking the coatings in 3.5% NaCl at 25 °C for two weeks, which was consistent with the resistance increase measured by electrochemical impedance spectroscopy. Microhardness test results showed about a 25% increase in the hardness for the copper-nickel coatings incorporated with the layered silicate platelets versus the pure Cu–Ni coating.

Effect of salicylaldehyde on microstructure and corrosion resistance of electrodeposited nanocrystalline Ni–W alloy coatings

Abstract In this paper, nanocrystalline Ni–W alloy coatings were deposited from citrate bath containing salicylaldehyde (0–500 ppm). The structure, microstructure and surface roughness of coatings were separately analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscopy (AFM). The corrosion resistance of the Ni–W alloy coated specimens was evaluated using potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) studies. Results indicated that electrodeposits obtained in the presence of additive (100 ppm) in the bath were, nanocrystalline, uniform and smooth in their texture. A low value (7.02 μA/cm 2 ) of corrosion current and high value (1666.90 Ω cm 2 ) of charge transfer resistance supports for its superior corrosion resistance property. The inclusion of additive in the deposit was evidenced by FT-IR spectra.

Electrodeposition of laminar coatings of Ni–W alloy and their corrosion behaviour

The attractiveness of electroplating for the synthesis of advanced materials is linked to large selection of plating conditions coupled with different mass transfer processes towards the cathode, and this allows the tailoring of different properties of many electrodeposited coatings. This theme has been exploited effectively in the development of a new class of coatings; called composition modulated multilayered (CMM), or in short laminar coatings. The work embodied in this paper is to demonstrate how the corrosion resistance of monolayer Ni–W alloys can be increased to many fold of its magnitude by multilayer deposition. Ni–W coatings have been deposited on mild steel (MS) in a laminar multilayer pattern from a citrate bath using single bath technique (SBT). Electrodeposits having alternate layers of alloys, having different compositions were developed by modulating the direct current (DC). CMM coating configurations have been optimized from a newly developed bath, in terms of current pulse height and thickness of each layer to maximize its corrosion protection ability, in relation to its monolayer coating, developed from same bath for same time. The process and product of the Ni–W coatings have been characterized using different instrumental methods, such as cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) study. The better corrosion resistance behaviour of CMM Ni–W coatings has been analysed in the light of increased surface areas of the coatings due to layering, and results are discussed.

Sliding wear behavior of electrodeposited Ni–W alloy and hard chrome coatings

Present study deals with the comparative sliding wear behavior of electrodeposited nickel–tungsten (Ni–W) alloy and conventional hard chrome (HCr) coatings. Ni–W alloys with different W (7.4, 10.5 and 11at%) content in Ni were systematically deposited using pulsed electrodeposition from citrate bath. In addition, pure Ni coatings were also obtained from Watt׳s bath for comparison purpose. The dry sliding wear behavior of Ni, Ni–W and HCr coatings was compared using pin on disc configuration against WC–Co disc at three different loads. The results indicate that the wear rate is lowest for NiW10.5 amongst all the coatings despite of the fact that HCr coating is 12% harder than NiW10.5 coating. The wear behavior was attributed to ductile wear mechanism in NiW10.5 coatings as opposed to brittle fracture in the case of HCr coatings.

Electrodeposition and Electrocatalytic Study of Ni-W Alloy Coating

Electrocatalytically active Ni-W alloy coatings have been developed through compositionally versatile electrodeposition method on copper substrate from tri-sodium citrate bath, using glycerol as the additive. The deposition conditions have been optimized for peak performance of their electrocatalytic behavior, like hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1M KOH. Corrosion behaviors of the coatings have also been tested under study conditions of electrocatalysis. Electrocatalytic behaviors were tested by cyclic voltammetry (CV) and chronopotentiometry techniques. Experimental results demonstrated that Ni-W alloy coatings, deposited at low and high current densities (c. d.) were showing superior performance for OER and HER, respectively. Better electrocatalytic activity for HER with increase of deposition c. d. was attributed by the unique phase structure, surface morphology and chemical composition of the coatings, confirmed by XRD, SEM and EDX analysis. The dependency of coating thickness and hardness on HER and OER were analyzed, and results are discussed.

Mechanism of Nanocrystalline Nickel Electrodeposition from Novel Citrate Bath

The electrochemical behavior of nanocrystalline nickel deposition in citrate bath was investigated by electrochemical impedance spectroscopy (EIS). The two-step discharge of Ni (II) cations was confirmed, and an intermediate absorbate Ni(OH)ads originated from the reversible first step. The analysis of the impedance of nickel deposition showed that apart from the capacitive loop at the high frequency due to the double layer, the inductive loop at low-frequency was observed in a citrate bath which is ascribed to the relaxation of the electrode coverage by Ni(OH)ads. The electrochemical behavior observed in the experiment processes and results could be accounted for by the reaction mechanism implying two successive transfer reactions in which Ni(OH)ads acts as an intermediate compound consumed at the electrode. By quantitative analysis and simulation of the results of the cathodic impedance, the impedance parameters of nickel deposition in a bath with or without sodium citrate were obtained. The presence of sodium citrate in the bath increases the charge transfer resistance of nickel deposition and reduces the capacitance of the electrochemical double-layer.

Spalling of a Single Crystalline Silicon Layer By Electroless/Electrodeposit-Assisted Stripping(EAS) Process for Flexible Silicon Devices

The purpose of this study was to investigate a novel kerf-free method to reduce thecost of the silicon materialfor flexible silicon devices such as a solar cell, a TFT(thin film transistor) and etc. In the last few decades, there were a number of attempts to reduce the production cost of the silicon by reducing the thickness of the silicon wafer such as a sawing technique, a high-temperature induced spalling process and etc. Among these techniques, a novel method called Electroless/Electrodeposit Assisted Stripping(EAS) process is one of the most effective and inexpensive kerf-free methods for acquiring a high quality thin-single crystalline silicon film. The EAS process is schematically described in Figure 1. This technique requires a stressor layer at a predetermined depth by manipulating the stress value and thickness of Ni deposit. A stress is induced by a nickel layer electrodeposited from citrate bath at room temperature. As the induced tensile stress was introduced at the critical value, a thin Si layer without crack was successfully lifted off from a silicon substrate. The advantage of the EAS process is that the thin silicon film can be repetitively lifted off from a Si substrate, so that it dramatically reduces the manufacture cost of the solar cell and can also be reproduced continuously owing to its all-wet process. The EAS process is consisted of three steps: 1) forming a Ni seed layer with nano-rod using anelectroless deposition to enhance the adhesion of seed layer on Si substrate, and 2) forming a low stress layer as a buffer layer to prevent cracks on a seed layer and then finally 3) forming a high stress layer using electrodeposit at room temperature. A high quality Si film could be obtained by the precise control of two parameters: 1) adhesion between a metal seed layer and Si, 2) critical stress applied to Si substrate. Concerning control of the adhesion of the Ni seed layer-Si interface, a Ni seed layer has to be satisfied with both high adhesion on Si and high resistance of crack by a high stress-inducing layer. We investigated a high adhesive electroless seed layer on Si in place of a conventional high cost PVD(physical vapor deposition) process. Firstly, nano-holes were formed with control of a critical spacing on Si surface by MACE(metal assisted chemical etching) and then both holes and Si surface were covered with Ni using autocatalytic electroless deposition. The effect of the nano-hole in silicon, such as a pretreatment for enhance adhesion, is also investigated using different MACE parameters – control of metal distribution, depth in Si, the size of the nano-hole, various etched structure. Concerning control of a critical stress applied to Si substrate, a stress layer has to be satisfied with a certain stress value high enough to propagate a crack within Si during electrodeposition. We investigated both internal stress value of the Ni deposit and the spalling behavior under different conditions of composition, current density, pH, temperature etc. Figure 1

A Comparative Study of Saturation Induction with Current Density of Electrodeposited Fe-Ni-W Alloys

Fe-Ni-W alloys are electroplated from an ammonical citrate bath by applying three different current density values of 28, 56, and 84 mA/cm2. The morphology and structure of Fe-Ni-W alloys are detected by Scanning Electron Microscope (SEM) and X-ray diffraction (XRD), respectively. The deposits are smooth and well adhered to the substrate at a current density of 28 mA/cm2, while at current density values of 56 mA/cm2 and 84 mA/cm2 deposits were smooth but showed cracks in the layer. All the as-plated deposits have nano crystalline structures and have two phases of WO3 and BCC structured solid solution of Ni and W in Fe. The BCC structure is the dominant microstructure at high current density. The constituents in the films are determined by Energy Dispersive X-ray spectroscopy (EDX) technique. The magnetic saturation induction of the plated deposits is studied with the help of a Vibrating Sample Magnetometer (VSM).

Acute effect of citrate bath on postdialysis alkalaemia

IntroductionThe correction of metabolic acidosis caused by renal failure is achieved by adding bicarbonate during dialysis. In order to avoid the precipitation of calcium carbonate and magnesium carbonate that takes place in the dialysis fluid (DF) when adding bicarbonate, it is necessary to add an acid, usually acetate, which is not free of side effects. Thus, citrate appears as an advantageous alternative to acetate, despite the fact that its acute effects are not accurately known. ObjectiveTo assess the acute effect of a dialysis fluid containing citrate instead of acetate on acid-base balance and calcium-phosphorus metabolism parameters. Material and methodsA prospective crossover study was conducted with twenty-four patients (15 male subjects and 9 female subjects). All patients underwent dialysis with AK-200-Ultra-S monitor with SoftPac® dialysis fluid, made with 3 mmol/L of acetate and SelectBag Citrate®, with 1 mmol/L of citrate and free of acetate. The following were measured before and after dialysis: venous blood gas monitoring, calcium (Ca), ionic calcium (Cai), phosphorus (P) and parathyroid hormone (PTH). ResultsDifferences (p<0.05) were found when using the citrate bath (C) compared to acetate (A) in the postdialysis values of: pH, C: 7.43 (0.04) vs. A: 7.47 (0.05); bicarbonate, C: 24.7 (2.7) vs. A: 27.3 (2.1) mmol/L; base excess (BEecf), C: 0.4 (3.1) vs. A: 3.7 (2.4) mmol/L; corrected calcium (Cac), C: 9.8 (0.8) vs. A: 10.1 (0.7) mg/dL; and Cai, C: 1.16 (0.05) vs. A: 1.27 (0.06) mmol/L. No differences were found in either of the parameters measured before dialysis. ConclusionDialysis with citrate provides better control of postdialysis acid-base balance, decreases/avoids postdialysis alkalaemia, and lowers the increase in Cac and Cai. This finding is of special interest in patients with predisposing factors for arrhythmia and patients with respiratory failure, carbon dioxide retention, calcifications and advanced liver disease.