Electrodeposition of noncrystalline cobalt–tungsten alloys from citrate electrolytes

Induced electrodeposition of Co–W alloys onto steel substrates from acid citrate baths has been investigated. The effects of some plating parameters, such as current density, pH and temperature on the potentiodynamic cathodic polarization curves, cathodic current efficiency of the alloy and the percentage tungsten in the alloy were studied. Highly adherent and compact Co–W alloys codeposited from citrate baths containing up to 28 mass % tungsten were obtained. The percentage W (w/w) in the alloy increases with increasing pH, bath temperature and Co²⁺ ion concentration. On the other hand, the percentage W in the alloy decreases with increasing current density. Anodic linear stripping voltammetry (ALSV) indicated that the alloy might consist of one phase solid solution. These alloys were determined to be noncrystalline by X-ray diffraction analysis.     

Dissolution from electrodeposited copper–cobalt–copper sandwiches

The electrochemical behaviour of electrodeposited Co–Cu/Cu multilayers from citrate electrolytes was investigated using cyclic voltammetry and stripping techniques at a rotating ring disc electrode. Copper and cobalt–copper alloy sandwiches were deposited from an electrolyte containing 0.0125 M CuSO₄, 0.250 M CoSO₄ and 0.265 M trisodium citrate at two different pHs, 1.7 and 6.0. The Cu/Co–Cu/Cu sandwich is representative of a single layer in a Co–Cu/Cu multilayer deposit, which is known to exhibit unusual physical and magnetic properties. Results from cyclic voltammetry and detection of dissolving species at the ring showed that cobalt is stripped from a Cu/Co–Cu/Cu sandwich even when a copper layer as thick as 600 nm covers the Co–Cu alloy. Scanning electron microscopy showed that cobalt can dissolve from the deposit easily because the copper layer covering the Co–Cu alloy is porous. A separate series of experiments with Cu/Co–Ni–Cu/Cu sandwich showed that cobalt does not dissolve from these deposits because the addition of nickel stabilises cobalt in the Co–Ni–Cu alloy.     

Electrochemical preparation and magnetic study of Bi–Fe–Co–Ni–Mn high entropy alloy

A facile and efficient synthesis route for the preparation of Bi–Fe–Co–Ni–Mn high entropy alloy films has been firstly reported in this work. The surface of the film is close-grained and the nanorods with high aspect ratios can be obtained by potentiostatic electrodeposition in the DMF (N,N-dimethylformamide)–CH₃CN organic system. The effects of the deposition potential and the molar ratio of Bi(III) to transition metal ions (TMs(II)) in the organic system on the contents of Bi in the HE alloy were investigated. The annealed alloy structure is composed mainly of face-centered-cubic solid solution. The as-deposited alloys show soft magnetic behavior, and the annealed alloys exhibit hard magnetic properties.     

Electrochemical characterization of Ni–P and Ni–Co–P amorphous alloy deposits obtained by electrodeposition

Ni–P and Ni–Co–P amorphous alloy deposits were obtained by electrodeposition at 80 °C on carbon steel substrates. The influence of the electrolyte Co²⁺ concentration and of applied current density was investigated. The corrosion behaviour of amorphous and crystalline deposits was evaluated by polarization curves and electrochemical impedance spectroscopy in NaCl 0.1 M solution at room temperature. Impedances were measured for samples under total immersion (free potential against time) and for polarized samples in predefined regions of the polarization curves. It was found that the alloy deposit composition is highly affected by the composition of the electrolyte but displays no significant dependence on applied current density. The results showed that the presence of Co on Ni–P amorphous alloys improves the deposit performance in the studied corrosive medium. It was also verified that the amorphous structure provides higher corrosion resistance to both Ni–P and Ni–Co–P alloys.     

Ni–Zn–P alloy deposition from sulfate bath: inhibitory effect of zinc

Electroless Ni–Zn–P alloy deposition from a sulphate bath, containing sodium hypophosphite as reducer, was investigated. To increase the plating rate, the deposition parameters were optimized. The effect of process parameters (T, pH and [Zn²⁺]) on the plating rate and deposit composition was examined and it was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition. As a consequence, the percentage of zinc in the electroless Ni–Zn–P alloys never reaches high values. Using cyclic voltammetry the electrodeposition mechanism of Ni–Zn–P alloys was investigated. It was observed that the zinc deposition inhibits the nickel discharge and, as a consequence, its catalytic activity on hypophosphite oxidation. It was also found that increase in temperature or pH leads to the deposition of nickel rich alloys.     

镍钨合金电沉积的电流效率和镀层显微硬度

通过调节镀液中不同的Ｎｉ／Ｗ比例、温度和沉积电流密度,研究在焦磷酸盐体系中镍钨合金电沉积的电流效率、沉积层和组成和显微硬度。实验结果表明：合金共沉积的电流效率不高。为了尽量提高合金的沉积电流效率,主要途径宜增大镀液中硫酸镍和钨酸钠的浓度;提高合金沉积电流密度,降低镀液中［Ｎｉ］／［Ｗ］比例,则镀层中的钨含量增大;合金沉积层的显微硬度随镀层中的Ｗ含量提高而增大。     

Electrodeposition of Au–Sn alloys from acid Au(III) baths

A bath for the electrodeposition of white gold alloys of interest for the electroforming of hollow jewellery is proposed and investigated. The system was an acidic Au(III)–Sn(IV) bath for the electrodeposition of Au–Sn alloys. The electrochemical investigations were based on cyclic voltammetry, linear-sweep voltammetry, galvanostatic electrodeposition experiments and in situ Raman spectroscopy. The electrode kinetics of alloy formation were elucidated by stripping voltammetry. The effects of cathodically adsorbed CN^– were studied by in situ Raman spectroscopy. Electrodeposited foils were studied from the crystallographic, compositional and morphological points of view. Codeposition of Au and Sn gives rise to a single phase of approximately equiatomic composition over a current density interval of 10 to 40 mA cm^–2. This orthorhombic phase is structurally the same as the phase of the equilibrium Au–Sn system, but its stoichiometry and lattice parameters are different. The equilibrium two-phase , structure can be obtained by heat-treatment.     

Electrochemistry of the SUCOPLATE® Electroplating Bath for the Deposition of Cu–Zn–Sn Alloy; Part II: Influence of the concentration of bath components

The chemistry of a commercial alkaline cyanide electroplating bath used for the deposition of a Cu–Zn–Sn alloy has been investigated. The voltammetry, the deposit composition and the morphology have been investigated as a function of the concentrations of the three metal ions, Cu(i), Zn(ii) and Sn(iv) as well as the concentrations of cyanide, hydroxide, carbonate and `Copper Glo' additive. It is shown that all components combine to control the bath performance although the trends in alloy composition and quality can be predicted from the known chemistry of the bath. It is also concluded that the deposition of tin has an important role in initiating the growth of alloy layers.     

电沉积无铅可焊性锡铋合金的研究

提出了一种酸性锡铋合金电沉积工艺。研究了镀液中硫酸铋含量和电流密度对镀层铋含量、电流效率及镀层表面形貌的影响，另外，通过循环伏安曲线的测量研究了锡铋合金的电沉积过程，结果表明，镀层铋含量随硫酸铋含量的增大而增大，铋在-0.3V时开始析出，当电位达到-0.6V时，锡和铋共同沉积。     

Detection and characterization of molybdenum oxides formed during the initial stages of cobalt–molybdenum electrodeposition

The initial stages of cobalt–molybdenum electrodeposition on a vitreous carbon electrode were studied to obtain information about the mechanism of cobalt–molybdenum induced codeposition. Solutions containing cobalt sulphate, sodium molybdate and sodium citrate at pH 6.6 were used. A first step in the mechanism of alloy deposition is proposed. This step takes into account the formation of molybdenum(IV) oxides over which Co–Mo alloy may be only deposited if sufficient potential is applied. Co–Mo electrodeposition occurs through an early stage involving low reduction current, related to the formation of molybdenum oxides, followed by a later stage in which the reduction current suddenly increases, corresponding to alloy codeposition. When a low potential is applied, a continuous coloured molybdenum oxide film is formed on the electrode and Co–Mo is not deposited. To induce the alloy deposition on the oxide film it is necessary to apply more negative potentials than a threshold value, which depends on the composition of the electrolytic bath. By increasing molybdate concentration in solution, the threshold potential shifts to more negative values. Intermediate molybdenum oxides were characterized using scanning electron microscopy (SEM), compositional analysis, Raman measurements and Auger and X-ray photoelectron spectroscopies.     

络合剂对镁-镍储氢合金电沉积的影响

通过循环伏安法、交流阻抗法研究了一种有机络合剂对有机镀液中镁-镍合金在铜上共沉积的影响。并通过以合金镀层为电极的充放电性能测试,确定了镀液中络合剂的最佳浓度。结果表明,络合剂对电沉积是有利的,适量络合剂的加入能显著提高以镁-镍合金镀层为电极的最高放电比容量。     

Effect of heat treatment on electroless ternary nickel–cobalt–phosphorus alloy

Ternary Ni–Co–P and binary Ni–P alloy coatings were deposited on mild steel panels from an alkaline bath in the presence and absence of cobalt sulfate using an electroless process. The effects of heat treatment on surface topography and crystal orientation of Ni–Co(11.17%)–P(3.49%) alloy coatings were studied in contrast to that of Ni–P ones. It was found that the as plated Ni–Co–P alloy is a supersaturated solid solution of P and Co dissolved in a microcrystalline Ni matrix with 111 preferred direction. Heat treatment induces structural changes. The formation of Ni₃P phase precipitates and recrystallization of nickel occur when the sample is treated at > 400 °C for one hour. It is observed that the Ni diffraction lines of treated Ni–Co–P alloy at > 400 °C are shifted to lower angles as compared to those of treated Ni–P or as plated Ni–Co–P alloys. The surface topography of Ni–Co–P alloy also changes with heat treatment temperature. The surface topography and crystal orientation were characterized by means of scanning electron microscopy and X-ray diffraction, respectively. The hardness and corrosion resistance, in 5 wt % NaCl solution, of heat treated Ni–Co–P samples were studied.     

Effect of tartrate on the morphological characteristics of the copper–tin electrodeposits from a noncyanide acid bath

Copper and tin were electrodeposited on platinum substrates from a 1.0 M sulphuric acid plating bath in the presence and absence of tartrate. Voltammetric curves indicated two deposition processes, at –0.310 and –0.640 V, which do not shift upon addition of tartrate to the plating bath. The presence of tartrate decreased the current density in the region of the more cathodic process. The metals were electrodeposited at both deposition potentials and the deposits have the same proportions of copper and tin either with or without tartrate in the plating bath, as observed by AAS. X-ray spectra suggested that a mixture of Cu and -Cu₆Sn₅ alloy was deposited at the less cathodic potential. SEM analysis showed that tartrate affects the morphology of the films.     

Electrodeposition of Ni-W-B amorphous alloys

Partial polarization curves at the glassy carbon rotating disc electrode have been used to study the electrodeposition of Ni and Ni-W alloy from citrate-containing solution. For deposition of Ni-W alloys, the partial polarization curves indicate diffusion control for nickel reduction and stoichiometric limitation for tungsten deposition by the composition of the alloy. Plating experiments show that current efficiency of the electrodeposition and composition of the resulting alloy depend on the parameters of the electrolysis. The best conditions for electrodeposition of the alloy Ni-W-B are current density of 45–50 mA cm^–2, temperature of 60–70 °C, Ni(II) concentration of 20–25 mm, and pH 8.5. Pulsed galvanostatic plating at 1 Hz increased slightly the current efficiency. The concentration of Ni(II) in the solution can be self-regulated by using a nickel bipolar electrode in the cathode compartment.     

Influence of constant magnetic field on the electrodeposition of Co–Mo–W alloys

The aim of this study was to investigate the effect of a constant magnetic field (CMF) on the electrodeposition of Co–Mo–W alloys, and to observe changes in the topography of the alloy surface and its chemical composition. The investigation included the use of Cyclic Voltammetry (CV), Coulometry (C), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX). At higher electrolyte concentrations (so-called II), the CV method revealed an increase in cathode current density in a CMF environment. During crystallisation of the Co–Mo–W alloy, fractures appeared on the surface due to internal stresses. The application of CMF reduced the fracture widths resulting from the increased concentration of electroactive particles at the working electrode and the greater deposited alloy mass. Electrolyte motion under the influence of CMF caused an increase in the percentage of the main ferromagnetic component (Co) in the alloy.     

Tin–cobalt electrodeposition from sulfate–gluconate baths

The electrodeposition of tin + cobalt alloys from a slightly acidic sulfate–gluconate bath on both vitreous carbon and copper substrates has been studied for different [Sn(II)]/[Co(II)] ratios in the bath, varying between 1/10 and 1/2. A relationship between the electrochemical stripping analysis and the morphology of the deposits has been found. Two different types of deposit were obtained. At low [Sn(II)]/[Co(II)] ratios and relatively high deposition rates a nodular, cobalt-rich, nanocrystalline coating was obtained, while at high [Sn(II)]/[Co(II)] ratios and low deposition rates a new, well-defined tetragonal SnCo phase was obtained, with cell parameters of a = 3.087 Å and c = 5.849 Å. This structure favours hydrogen evolution.     

Electrodeposition of copper and nickel on InBi alloy electrodes

Electrodeposition of copper and nickel was investigated on the 67–33 w/w InBi soft alloy, which has a low melting point (72°C). The electrochemical behaviour of this alloy was found to be similar to that of pure indium in a Watt's type bath. Direct and pulsed current techniques were compared. For copper, a current density ranging from 500 to 1000Am–2 was found to be suitable to obtain regular and shiny deposits at 25°C. For nickel, at 45°C, the current density range used was 500 to 1250Am–2 to obtain good deposits, that were not affected by hydrogen evolution. Pulsed and direct currents were found to be equally efficient. The main interest of electrodeposition on InBi alloy was the ease of removal of the alloy by simple melting, and consequently to make electrodes of unusual shapes which are normally difficult to produce industrially. Only a small amount of InBi alloy remained in the inner part of the deposit.     

Electrodeposition of Au–Sn alloys from alkaline baths

A bath for the electrodeposition of white gold alloys of interest for the electroforming of hollow jewellery is proposed. The investigated system is an alkaline KAu(CN)₂ bath for the electrodeposition of Au–Sn alloys. The electrochemical investigations are based on cyclic voltammetry and electrodeposition experiments. Electrodeposited foils were studied from the crystallographic, compositional and morphological points of view. Co-deposition of Au and Sn gives rise to the formation of a series of intermetallic phases, which can be detected by X-ray diffraction and anodic stripping. Deposits are typically polyphasic; the phase composition generally does not correspond to the equilibrium one. Chemical compositions ranging from high-Au to high-Sn can be obtained by galvanostatic deposition at suitable current densities.     

Electrodeposition of palladium–silver in a Lewis basic 1-ethyl-3-methylimidazolium chloride-tetrafluoroborate ionic liquid

The electrodeposition of palladium–silver alloys was investigated in a basic 1-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid containing Pd(II) and Ag(I). Cyclic voltammetry experiments showed that the reduction of Ag(I) occurs prior to the reduction Pd(II). Both electrodeposition processes require nucleation overpotential. Energy-dispersive spectroscopy data indicated that the composition of the Pd–Ag alloys could be varied by deposition potential and concentrations of Pd(II) and Ag(I) in the solution. The Pd content in the deposited Pd–Ag alloy increased with decreasing deposition potential and the Pd mole fraction in the plating bath. At potentials where the deposition of both Pd and Ag was mass-transport limited, the Pd/Ag ratio in the electrodeposited alloys was slightly less than the Pd(II)/Ag(I) ratio in the ionic liquid due to the smaller diffusion coefficient of Pd(II). Scanning electron micrographs of the electrodeposits showed that in general, the Pd–Ag alloys were nodular and become more compact upon increasing the temperature up to 120 °C.     

The effect of the concentration of TBACl on the electrodeposition of zinc from chloride and perchlorate electrolytes

The effect of the concentration (5 to 220 mg l^–1) of tetrabutylammonium chloride (TBACl) on zinc deposition overpotential and on the degree of levelling of Zn electrodeposited on a Zn RDE was studied by cyclic voltammetry, galvanostatic measurements and SEM examination. The overpotential for Zn electrodeposition initially increases with increasing TBACl concentration until reaching a limiting value, at which point the surface becomes blocked by adsorbed TBA⁺. The optimum degree of deposit levelling is obtained for intermediate TBACl concentrations, whose value depends on the concentration (1 or 2.5m) of NaCl supporting electrolyte. When NaClO₄ is substituted for NaCl in the bath, the overpotential for Zn electrodeposition markedly increases and consequently the levelling power of TBACl decreases.