Cathodic Current Efficiency Research Articles

Effect of Electrolysis Potential and Molar Ratio of CaO to SiO<sub>2</sub> on Si Metal Deposition in Molten CaCl<sub>2</sub>

The electrodeposition of Si metal in molten CaCl2 containing various types of calcium silicate has been studied at 1373∼1673 K. It was shown that the influence of the molar ratio of CaO to SiO2 on Si electrodeposition was not remarkable in contrast with our previous results that the molar ratio of CaO to TiO2 strongly affected the Ti metal deposition in the similar system. Silicon metal was obtained on MoSi2 cathode in the melt by potentio-static electrolysis. The cathodic current efficiency was about 30% regardless of the added types of calcium silicate. The current efficiency tended to be better as the electrolysis potential became negative, but the electrolysis below the border potential lead to lower current efficiency due to Ca co-deposition.

Electrolyte Temperature Dependency of Electrodeposited Nickel in Sulfate Solution on the Hardness and Corrosion Behaviors

The hardness and corrosion resistance of nickel (Ni) deposit on a substrate could be reached by controlling electrolyte temperature during deposition. In this research, the electrodeposition of Ni at various temperatures of electrolytes was performed. Electrodeposited Ni films using an optical digital camera, X-ray diffraction (XRD), scanning electron microscope with energy-dispersive x-ray spectroscopy (SEM-EDS), microhardness test, and potentiostat were investigated. The bright deposit occurred at 25 °C; an increase in the temperature to 40 °C leads to a change of color into semi-bright. Shifting to a higher temperature would increase the deposition rate, cathodic current efficiency, grain size, and oxygen content. The X-ray reflections in the planes (111), (200), and (220) correspond to as the Ni phase with a face center cubic (FCC) crystal structure. Decreasing crystallite size and micro-strain promoted to reach high hardness. Increasing the corrosion current density implies decreasing polarization resistance. The sample at the lowest electrolyte temperature has a better hardness, and the sample formed at 25 °C sulfate solution had less corrosion rate.

Simulation and Optimization of CNTs Cold Cathode Emission Grid Structure

Carbon nanotubes (CNTs) show significant advantages in the development of cold cathode X-ray tubes due to their excellent field emission performance; however, there are still some problems, such as short lifetime and the low emission current of large-area CNTs. In this paper, a front-grid carbon nanotube array model was established, and the electric field intensity near the tip of the CNTs' electric field enhancement factor was analytically calculated. A simulation model of a CNT three-dimensional field emission electron gun was established by using computer simulation technology (CST). The effects of grid wire diameter, grid aperture shape, and the distribution of grid projection on the cathode surface on the cathode current, anode current, and electron transmission efficiency were analyzed. The aperture ratio was used to evaluate the grid performance, and the simulation results show that the ideal aperture ratio should be between 65% and 85%. A grid structure combining a coarse grid and a fine grid was designed, which can make the electric field intensity around the grid evenly distributed, and effectively increased the cathode emission current by 24.2% compared with the structure without the fine grid. The effect of grid aperture ratio on the electron transmission efficiency was tested. The simulation results and optimized structure can provide a reference for the grid design of cold cathode emission X-ray tubes.

Physico-Chemical Properties of Zn-Ni Alloy from Alkaline Sulphate Bath Containing Tartrate

The composition, properties, voltammetry studies and morphology of electrodeposited Zn-Fe alloy deposits obtained from an alkaline sulphate bath containing tartrate have been investigated. A bath containing high percentage of iron (20% wt.) produced an alloy with less percentage of iron (12% wt.) i.e. anomalous co-deposition process. The percentage of iron in an alloy decreased with temperature of the plating bath and thickness of the alloy deposit. The cathodic current efficiency depends on plating variables. Cyclic voltammetry studies indicate the mutual co-deposition of zinc with iron. Zn-Fe alloy showed a superior corrosion resistance than zinc coatings. Hardness of the alloy deposits increased with increase in iron content in the alloy. Smooth, uniform and fine grained deposits were obtained for the Zn-Fe alloy containing 20% Fe.

Green hydrometallurgical extraction of metallic lead from spent lead paste in the methanesulfonic acid system

As the mainstream process for recycling waste lead-acid battery paste to produce metallic lead ingots, pyrometallurgical smelting generally suffers from disadvantages such as high energy consumption, lead vapor and sulfur dioxide emissions. Hydrometallurgical extraction has received widespread attention because of its energy-saving and environmentally-friendly features. An innovative and efficient process for the hydrometallurgical recovery of lead paste was presented in this paper. In order to significantly improve the leaching efficiency of lead, PbSO4 in the lead paste was firstly converted into acid-soluble Pb3(CO3)2(OH)2 or NaPb2(CO3)2OH in Na2CO3 solution. At the same time, the insoluble PbO2 was reduced to PbO by the addition of Na2SO3. The pretreated product was then leached in MSA solution to obtain the lead-containing leachate, which was finally electrodeposited to produce lead deposits and to regenerate MSA. Under the optimized conditions, a dense and flat lead plate (purity greater than 99.99 %) could be obtained and the total lead recovery ratio in the whole process can reach 95.28 %. The cathode current efficiency and specific energy consumption in the lead electrodeposition procedure were 99.31 % and 598.91 kWh/t Pb, respectively. The electrolyte waste could be returned to the leaching process as the leaching agent. In contrast to the traditional fluorosilicate/fluoroborate and chloride systems, the environmentally-friendly MSA system with high lead solubility and low volatility, has promising applications in the field of lead hydrometallurgy.

A Study on Physico-Chemical Properties of Zn-Co Alloy Deposits from an Acid Sulphate Bath Containing Triethanolamine and Thiaminehydrochloride

The composition, properties, structure and morphology of electrodeposited Zn-Co alloy deposits obtained from an acid sulphate bath containing TEA and thiaminehydrochloride have been investigated. A bath solution containing 11% Co produced an alloy deposit with 0.6% Co indicating preferential deposition of zinc (anomalous process). The percentage of Co in the alloy increased with increase in current density and temperature. Cathodic current efficiency decreased with increase in current density and temperature. Static potentials of Zn-Co alloy were less negative to zinc and more negative to mild steel. Zn-Co alloy forms solid solution structure (-phase). The morphology of the alloy varied with %Co in an alloy deposit.

The relative efficiency of electrowinning indium from chloride electrolytes

The main characteristics of electrolytic reduction applied to indium recovery from aqueous chloride solutions were considered theoretically and examined experimentally. Also other media were considered for comparison. Potentiodynamic examinations pointed out that chloride electrolytes are superior to sulphuric and nitric acid-based ones for efficient indium deposition. The optimum conditions, allowing higher than 90% cathodic current efficiencies, were determined by galvanostatic experiments. In contrast, similar sulphate electrolytes could only yield lower than 50% efficiencies because of a stronger hydrogen evolution. The galvanostatic results confirmed the findings of the potentiodynamic study. The cathodic polarisation curves revealed the major characteristics of the deposition process, implying a reduction of the electroactive In3+ ions. Coupled processes are the dynamic transformations of complex species and various rates of simultaneous hydrogen evolution. The structure and the elemental composition of the—relatively dense—cathodic deposits were examined by scanning electron microscopy and energy-dispersive X-ray analysis. Various levelling agents were also tested, and gelatine (up to a concentration of 1 g/dm3 in the chloride electrolyte) was found efficient in grain refining.Graphical abstract

(Digital Presentation) Effects of Oxide Ion and Sulfate Ion on Mg Metal Deposition in Molten Salt Electrolysis

With the growing demand for Mg, it is desirable to establish domestic Mg production in Japan. The author focuses on Mg production by molten salt electrolysis using MgCl2 extracted from concentrated seawater. The control of the contamination to the MgCl2 product should be a key issue, and also the influence of the contamination on the Mg production must be clarified. In this study, the effects of oxide ions and sulfate ions on Mg metal electrodeposition in molten salt have been investigated.Molten MgCl2-NaCl-CaCl2 with trace CaF2, for the new IG method was used as the bath, and MgO (0~1.0mass%) or Na2SO4 (0.025~0.5mass%) was added to the bath. A Mo wire with BN cover was used as the working electrode, and a carbon rod was used as thecounter electrode. The reference electrode was a Ag/AgCl couple in the same bath in a mullite tube, and its potential was calibrated against the Mg deposition potential. Experiments were done at 700°C in an Ar atmosphere. The cathodic behavior investigated by cyclic voltammetry, and then potentio-static electrolysis was performed. Visual observation was carried out during the cyclic voltammetry and potentio-static electrolysis. The electrodeposits after rinsing was evaluated by XRD, XRF, SEM-EDX and ICP, and the cathodic current efficiency was calculated from the weight of the deposit and the quantity of electricity.It was showed that the cathode reaction did not depend on MgO addition. Electrodeposits were obtained by potentio-static electrolysis regardless of MgO addition, and current efficiency was not significantly affected by MgO addition. The purity of Mg metal deposit was not influenced by the MgO addition in the bath, too; Mg metal above 99.9 mass% was obtained regardless of MgO addition, and the Na, K and Ca contents did not change evidently. It was suggested that the contamination of MgO to MgCl2 extracted from condensed seawater did not affect the Mg metal deposition directly. However, our previous work showed that the solubility of MgO in the bath was limited, so the MgO content in MgCl2 must be controlled.The result of cyclic voltammetry showed that cathodic current peaks appeared around 1V (vs. Mg deposition potential, the same hereinafter) and 0.5V by the addition of Na2SO4, and these peak currents were increased as increasing the added amount. Since MgO and MoS2 were detected after the potentio-static electrolysis at 1.2V and 0.5V, respectively, the cathodic current around this potential region seemed not to correspond to Mg metal deposition. Magnesium metal was obtained by the potentio-static electrolysis below 0.0V even in the bath containing sulfate ion, but the current efficiency got worse rapidly as the added amount of Na2SO4 increased. The surface of Mg metal deposit became rough with Na2SO4 addition, which caused the deterioration in its purity. It was shown that the contamination of even a small amount of sulfate to MgCl2 gave a negative influence to Mg metal deposition, so the control of its contamination should be important in the Mg metal production from concentrated seawater.This work was performed under the support of the commissioned work (JPNP14004) of the New Energy and Industrial Technology Development Organization (NEDO).

Green Electrorefining of Crude Lead with High-Quality Deposits in an Additive-Assisted Methanesulfonic Acid System

The conventional electrorefining process of crude lead (Pb)─employing a bone glue (BG)- and calcium lignosulfonate (CL)-synergistically assisted fluosilicic acid (H2SiF6) system─suffers the undesired environment burden caused by the high saturated vapor pressure and low stability of H2SiF6. Herein, we propose an additive-assisted methanesulfonic acid (MSA) system for green and efficient electrorefining of crude Pb based on the low volatility and high stability of MSA. Combinations of MSA with additives are evaluated and screened using photographic images, SEM observations, XRD, white light interference, etc. The electrochemical analysis of cyclic voltammetry and chronoamperometry elucidates the Pb deposition behavior in the Lugalvan BNO12-assisted MSA system, in which a three-dimensional nucleation model is applicable. Using MSA as the solvent and β-naphthol ethoxylate (Lugalvan BNO12) as the assisted additive, the bench-scale operation of crude Pb electrorefining experimentally achieves an electric energy requirement (W) of 87 kWhe/t Pb and a cathodic current efficiency (η) of 99.6%. This is very competitive with the W of 120 kWhe/t Pb and η of 95.0% for the BG-CL-assisted H2SiF6 system. Also, the bench-scale operation obtains a plat and dense deposit sample with a Pb purity of >99.99%. The distribution behavior of elements shows that most of the Pb element is recovered in the form of the cathodic Pb, elements Sn, Zn, and Fe mainly accumulate in the electrolyte, and elements As, Sb, Bi, Ag, and Cu remain in the anode slime. This work opens new directions for more technically and economically feasible Pb electrorefining.

A universal study of liquid metal cathodes for direct extraction of titanium within a closed loop

Due to the environmental pollution, long process, and high cost of the current titanium recycling technologies, hundred million tons of titanium containing blast furnace slag generated in the iron making process are abandoned, which calls for urgent and effective utilization. Herein, we report a universal study of a series of high titanium affinitive liquid metal cathodes coupled with graphite anode for direct titanium extraction from titanium containing slag in a molten oxide electrolysis method. Two cost free slags, titanium containing blast furnace slag and electroslag remelting slag, serve as the electrolytes, and a series of liquid cathode metals are tuned to reveal the depolarization effect. Through thermodynamic and experimental analyses and kinetic calculations, we find binding energy, work function, and activities of titanium in liquid metal cathodes can synergistically affect the preferential deposition of titanium. After galvanostatic electrolysis, titanium–rich alloy cathodes are obtained, which can be directly used as industrial products or further distillated in vacuum to separate pure titanium and recyclable cathode metals, forming a closed loop throughout its life cycle. An ultrahigh cathodic current efficiency (∼64%) with short process and low energy consumption is achieved in this work. The outcomes reveal this environmentally friendly strategy can achieve efficient utilization of titanium resources, significantly reduce the loss of energy in the extraction process and lower the industrial production costs, and the breakthrough of directly extracting titanium from titanium containing oxides in this work is of great importance to titanium industry.

Direct electrolysis of bunsen reaction product for hydrogen production: The continuous-flow operation

Hydrogen sulfide (H2S) emitted from oil industry's hydrotreating processes can be converted into hydrogen and used back to the same processes through a H2S splitting cycle, where the Bunsen reaction and HI decomposition are two participating reactions. To overcome the difficulties and complications posted in the scaling up of the cycle, direct electrolysis of the Bunsen reaction product solution was proposed and has been studied in a batch electrolysis cell in our earlier work. This paper studies the direct electrolysis using a customer-made, continuous-flow electrolysis cell. The effects of the operating parameters including the current density, the entering HI concentration and flow rate of the anolyte, the toluene to aqueous phase ratio and stirring speed in anolyte cell, the H2SO4 concentration and circulation rate of the catholyte on the performing parameters such as the conversion of iodide ions, the yield of iodine transferred to toluene, and the anodic and cathodic current efficiencies for iodide conversion and hydrogen production were carefully investigated. The results show that the cathodic current efficiency for hydrogen production is nearly 100% for all the runs and that the anodic current efficiency for iodide ion conversion to iodine is relatively low (20%–70%) and varies with the changes in operating parameters. Running at high levels of the current density, the volumetric ratio of toluene to aqueous phase in anolyte, or the stirring speed in anolyte, and low levels of the entering concentration of I− in anolyte or the flow rate of anolyte in electrolysis operation are in favor of having a high iodide conversion and high I2-toluene yield. Iodide anions at a few mmol L−1 level (a few thousandths of the entering concentration) are found in the cathodic chamber caused by its diffuse against the electric field and the proton exchange membrane. The continuous, direct electrolysis of the Bunsen product solution can be considered being adapted in the sulfur-iodine (S–I) water splitting cycle for hydrogen production.

Application of central composite design approach for optimisation of zinc removal from aqueous solution using a Flow-by fixed bed bioelectrochemical reactor

A flow-by fixed bed bioelectrochemical reactor was used for zinc removal from an aqueous solution. Response surface methodology (RSM) based on central composite design (CDD) was employed to study the effect of process parameters, such as applied voltage, initial zinc concentration, and pH, on the efficiency of zinc removal. To predict the relationship between the response of zinc removal efficiency (RE%) and its independent variables and to maximise this response, a quadratic model equation was established. The reliability of the quadratic model was confirmed by the high R2 value (98.61%). The optimisation study revealed that the initial concentration of zinc was the most effective parameter in the zinc removal process because of its highest F-statistic value (331.59). Using RSM, the optimum conditions for maximum zinc removal were an applied voltage of 1.8 V, an initial zinc concentration of 15.9 mg/L, and a pH of 7.6. With these conditions, a high zinc RE% (90.5%) could be achieved at a specific energy consumption of 0.65 kWh/kg Zn with cathodic current efficiency of 99%.

Nanocrystalline silver coatings on steel by electrodeposition from non-polluting aqueous baths and its antibacterial activity

BackgroundAntimicrobial coatings are one way that could help inhibit the spread of germs. Despite significant research into a variety of antimicrobial coatings with varied formulas, silver-based coatings appear to be the most effective. Electrodeposition is a promising technology to synthesize nanocrystalline silver coatings which have a wide range of applications such as in microelectronics, aerospace, automotive, biotechnology, nanobiotechnology, bioengineering sciences, in addition to its antimicrobial characteristics. Regrettably, cyanide electrolyte which is commonly applied in industry for silver coatings is one of the most hazardous substances, raising serious health and environmental hazards. It is important that seek high environmentally friendly electrolytes alternative to cyanide electrolytes. MethodsThe nanocrystalline silver coatings were successfully synthesized via galvanostatic deposition on stainless steel surface from an environmentally friendly novel bath. The electrochemical measurements were made utilizing linear sweep voltammetry (LCV), and cyclic voltammetry (CV). A high field emission scanning electron microscope (FESEM) and X-ray diffraction analysis (XRD) were used to characterize the obtained silver coatings. Significant findingsBright and adherent nanocrystalline Ag coatings (nano-size ranging between 14.8 and 67.6 nm) were synthesized by direct galvanostatic electrodeposition on SS surface from a bath free from cyanide. This environmentally friendly, cyanide-free bath is characterized by its high stability, low cost, and high cathodic current efficiency. The morphology was strongly dependent on the electrolyte composition as well as on the run circumstances. The microhardness of Ag deposited from this bath has a relatively high value (120.2–158.7 kg f mm-2) depending on the applied current density. Furthermore, the nanocrystalline silver coatings formed by these baths are excellent antibacterial agents versus a vast spectrum of gram-positive and gram-negative bacteria, particularly Listeria and Streptococcus bacteria.

Synergistic effect of L-cysteine and iodide ions during electrodeposition of nanocrystalline nickel from a Watts bath

ABSTRACT Nickel deposited from the Watts bath with L-cysteine (L-Cys) as a new organic brightener additive, and/or iodide ion was accomplished on a copper cathode. Cathodic polarisation, anodic linear stripping voltammetry, i-t transients, throwing power and cathodic current efficiency were investigated thoroughly. The surface of the produced Ni coatings was analysed using scanning electron microscope and X-ray diffraction (XRD) methods. The results showed that the inhibition of nickel reduction was observed in the presence of L-Cys or in the presence of iodide ions individually. Excellent inhibition was achieved with the addition of a mixture of L-Cys and I− ions due to their co-adsorption on the cathode surface (in a synergistic effect). Moreover, the TP value of the Watts bath in the presence of a mixture of L-Cys and I− ions is four times its value in the absence of this mixture. XRD measurements showed that the (200) level was the most preferred direction for growth and the intensity of all peaks increased considerably with a combination of L-Cys and I− ions. Fine-grained and pit-free deposits that were firmly adherent to the substrate were produced using a combination of L-Cys and NaI.

Electrochemical deposition of tin-copper alloy coatings

Solderable tin-base alloy coatings are widely used when assembling electronic products. The reorientation of production to lead-free technologies sets the task of developing new technological processes for the formation of coatings for electrical contacts with stable electrical properties, high soldering ability, which lasts for a long time. The features of the process of electrodeposition of coatings with a tin-copper alloy were experimentally investigated and the regularities of the influence of the electrolyte composition, current density, and ultrasound intensity on the cathode current efficiency of the alloy, the deposition rate, elemental composition, structure and functional properties of the precipitation were established. For sonochemical treatment an experimental setup developed at Research Laboratory 5.2 of BSUIR, which makes it possible to vary the intensity of ultrasonic vibrations in the range of 0.058– 1.7 W/cm2 , was used. It has been established that the use of ultrasound changes the formation mechanism of the electrochemical alloy, reduces cathodic polarization, increases the value of the limiting current and makes it possible to control the composition and structure of the precipitates. With an increase in the intensity from 0.12 to 0.95 W/cm2 the amount of copper in the coating increases by 4.5 times. The spreading coefficient of the solder is 92.59–98.44 %.

Efficient production of metal manganese achieved by cylindrical and rotary electrode

Electrowinning is a vital process for the production of metal manganese, however, always suffer from low cathodic current efficiency and nodule issues. Herein, a new concept involving cylindrical cell and rotary electrolysis is proposed and demonstrated for manganese electrowinning process. Results indicate that manganese deposits on cylindrical cathode are uniform and the edge effect is effectively suppressed. The cathodic current efficiency increases from 77.65% to 82.56% and the corresponding energy consumption decreases from 5.29 kWh/kg to 4.27 kWh/kg with the comparison of traditional plate electrolytic cell. Based on the above results, fluid field is further introduced by stirring catholyte and rotating cathode respectively. The fluid field can refine manganese grains and significantly inhibit the formation of manganese nodules. Under the proper cathode rotating speed, the cathodic current efficiency reaches 86.22% and ideal compact flat electrolytic manganese flakes can be obtained. Our strategy here may also inspire other researchers especially in electrochemical fields to improve energy and mass efficiencies for a bubble-involving chemical process.

A study of AVR sediment leaching with copper-bearing cyanide effluent and electrowinning recovery of copper

In this paper, we proposed a combined leaching-electrowinning approach to recover Cu from AVR sediment. Firstly, speciation diagrams of the metal-cyanide (Cu, Zn and Fe) system were constructed using thermodynamic calculations. Afterward, leaching-electrowinning experiments were systematically conducted. The speciation calculations showed that CuSCN was converted into Cu-CN compounds when the CNT/Cu mole ratio exceeded 1.71. The cyanide ions complexed with Zn2+ were completely captured by Cu+ when the Cu/Zn mole ratio reached 5.0, yielding the formation of zinc hexacyanoferrate composite or Zn(OH)2 precipitation. Corresponding leaching results indicated that the selective Cu leaching from AVR sediment was realized with the leaching efficiency of 99%, forming Na2Zn3[Fe(CN)6]2 as the main ingredient of the residue at the optimal leaching conditions. Cyclic voltammetry tests suggested that cuprocyanide complexes were dominantly presented as [Cu(CN)2]− complexes in the leachate (5680 mg/L, CNT/Cu mole ratio of 2.18), exhibiting much higher current density than that of [Cu(CN)3]2− in the cyanide effluent. However, during the electrowinning process, [Cu(CN)2]− were gradually converted into higher-order complexes, and the cathodic current efficiency decreased correspondingly. Ultimately, the Cu recovery of 92% was achieved with a current efficiency of 57% and energy consumption of 1.91 kW·h/kg Cu.

Cu(II)-Assisted CO2Absorption and Desorption Performances of the MMEA–H2O System

The complexation of metal ions and amines can mediate the chemical equilibrium and the thermal effect between amines and CO₂, thus promoting the absorption and desorption of CO₂ in amine absorbents. In this work, the effects of Cu(II) on the performances of CO₂ absorption and desorption in the Cu(II)–MMEA (2-(methylamino)ethanol)–H₂O system were studied. The thermal desorption results show that the temperature increase during CO₂ absorption can be mitigated in the presence of Cu(II), and the desorption performance of CO₂ can be obviously improved at 75–95 °C. Using the thermal desorption at 85 °C, the CO₂ desorption efficiency of MMEA solution containing 0.1 M [Cu] is 16.4% higher than that without cupric ions, and the regeneration energy consumption is reduced by 25%. The electrochemical research results indicate that the electrode structure and temperature affect the electrolysis rate of anodic copper, and the temperature is the key factor to enhance the CO₂ desorption rate. Only considering the decomposition voltage, the energy consumption of the absorbent regeneration is 0.5 GJ/t CO₂ at 50 °C, which is much lower than that of the thermal desorption method. The anode current efficiency is always about 100%. Increasing the temperature can increase the cathode current efficiency. When nickel foam with a large specific surface area is used as the cathode, the current efficiency can be increased to 100% at 50 °C. The CO₂ desorption is significantly improved in a Cu(II)-assisted MMEA–H₂O system. The electrochemical method can achieve a desired desorption at a relatively low temperature and greatly reduce the energy consumption of amine absorbent regeneration.

ELECTROCHEMICAL DEPOSITION OF TIN–ZINC ALLOY FROM CITRATE–AMMONIA ELECTROLYTE

The cathodic processes of electrochemical deposition of a tin–zinc alloy in citrate–ammonia electrolytes have been investigated. The content of the main components of the investigated electrolyte (g/dm3): SnCl2·2H2O – 44, ZnO – 4, NH4Cl – 100, Na3C6H5O7 – 100. Wood glue (1.5 g/dm3) and neonol (4 ml/dm3) were added to the electrolyte as surfactants. It was found that high–quality coatings are deposited without heating and stirring only in the pH range from 6,0 to 7,0. The addition of these substances to the electrolyte is predicted to lead to inhibition of the reduction of metals, an improvement in the crystal structure of the deposit, but decreases the cathodic current efficiency. Hull cell studies showed that an electrolyte containing neonol as a surfactant showed better throwing power compared to other solutions. The dependence of the current efficiency of the alloy on the cathode current density showed that in the range of current densities from 0.5 A/dm2 to 4 A/dm2, the current efficiency decreases nonlinearly from 82 % to 52 %. The experimentally obtained dependence of the zinc content in the alloy on the cathodic current density showed the possibility of obtaining alloys with a zinc content of 8 % to 33 %. The obtained results allowed us to determine that for the deposition of an alloy with a zinc content of 20–25 %, which provides the best anti–corrosion properties of the coating, it is necessary to carry out the process at a cathodic current density of 1,5–2,0 A/dm2, while the current efficiency is about 70 %, and the deposition rate alloy is 0,44–0,54 μm/min. The received coatings have a semi–bright appearance, a fine–grained structure, light gray color, they are strongly adhered to the substrate.

Effects of Current Density on Surface Morphology and Coating Thickness of Nickel Plating on Copper Surface

Nickel (Ni) thin film was deposited on commercial pure copper using electrodeposition method. To understand the growth behavior of Ni nodules, deposition was done by varying the coating current density. The topography of coating was analyzed using Scanning Electron Microscope (SEM). The coatings were also analyzed for variation in amount of coating, cathode current efficiency and thickness of coating. The deposited Ni thin film was observed to be of coffee bean kind of secondary nodules with size varying from 400 to 800 nm and almost spherical primary nodules with size varying from 100 to 250 nm varying as a function of coating current density. At higher current density, the coatings were observed to be of multiple layers of nodules. This suggests the presence of defects like twins, dislocations and stacking faults. The nodules are observed to have fine crystallites in the nano range.