Electroless deposition of Ni-P composite coatings containing kaolin nanoparticles

Abstract

The ability to codeposit particulate matter in a matrix of electroless nickel has led to a new generation of composite coatings with unique properties, such as high hardness wear, abrasion, corrosion and high temperature oxidation resistance. In this paper, the authors report on the development of electroless Ni–P–kaolin composite coating, and the characteristic properties of the selected deposits were evaluated by scanning electron microscopy, energy dispersive X-ray and X-ray diffraction techniques. A good rate of deposition of 12 μm h^?1 was observed for the optimised concentration of 6 g L^?1 of kaolin in the bath. For the optimised bath composition and operating conditions, the composite deposit was found to contain 81·7%Ni, 9·8%P and 10·5%kaolin. Heat treatment at 400°C for 1 h results in an increase in the hardness and wear resistance of the composite coating. The corrosion resistance is also highly enhanced by the incorporation of kaolin in the nickel–phosphorus matrix. The crystallite size of the composite coating is 20 nm, and the codeposition of kaolin follows the Langmuir adsorption isotherm.     

The effect of additives on the pulsed electrodeposition of copper

Abstract

The pulsed electrodepostion of copper has been systematically investigated from a copper sulphate bath. Pulse duty cycles of 5–80%, at frequencies from 10 to 100 Hz with current densities ranging from 2·5 to 7·5 A dm^?2 were employed. The influences of pulsed current duty cycle, peak current density and frequency on the thickness and hardness of the copper deposit, current efficiency and throwing power of the plating process were studied. The effect of additives, polyethylene glycol and di-sodium EDTA on the properties of deposit were investigated.     

Properties of ‘Sulpho-Chromispel-I’ electrolyte of standard concentration for the electrodeposition of chromium

The most important properties of non-standard highly efficient “Sulpho-Chromispel- I” type electrolytes for chromium plating have been investigated. They contain as side anions catalysing the cathodic process, both SO^2-₄ and I^?. The effects of cathodic current density and concentration of hydroiodic acid on the total current distribution are evaluated. The deposition rate is determined. The effect of operating parameters on the throwing power is established. The properties of the electrolytes studied are compared with those of standard sulphate electrolytes and “Chromispel-I” compositions. The most efficient electrolyte comprises CrO₃:I- = 20:1 and 20 cm³ dm^?3 sulphuric acid. The deposition rate can reach a value of 250 μm h^?1 at a current density of 200 A dm^?2. The throwing power of this electrolyte is close to that of standard sulphate electrolytes. As a whole “Sulpho-Chromispel-I” electrolytes exhibit lower throwing power compared to standard sulphate electrolytes or pure “Chromispel-I” electrolytes. They are recommended for chromium plating details of simple profile.     

Effect of plating time on electrodeposition of thick nanocrystalline permalloy foils

Thick foils of nanostructured permalloy were electrodeposited by applying a current density of 100?mA?cm^?2 for 48 hours. The bath contained nickel sulphate, iron sulphate, a complex agent, a grain refiner, a stress reducing agent, a buffer and a wetting agent. The bath pH was 3·8. Different parameters were controlled to get thick (approximately 860?µm), uniform permalloy coatings. To investigate the effect of electroplating time on the surface morphology, thickness and structure of foils, scanning electron microscopy, optical microscopy and X-ray diffraction were used. Chemical compositions of foils and the bath were investigated by quantometry and ultra violet–visible spectroscopy. The composition of the coatings was constant during the long period of electroplating, which was attributed to the bath stability. The cathode current efficiency of the electroplated permalloy foils increased slightly on increasing the plating time. Existence of chloride ions, complex agent and saccharin in the bath influenced efficiency.     

Electrochemical study on corrosion behaviour of zircaloy-2 in aqueous medium containing permanganate ion

Abstract

The corrosion compatibility of zircaloy-2 was studied in strong oxidising permanganate based acidic (HMnO₄) medium using impedance spectroscopy and potentiodynamic anodic polarisation methods at room temperature (28°C) and elevated temperatures (65 and 90°C). The average corrosion rate of zircaloy-2 in HMnO₄ medium (0·417–8·33 mM) was found to be 1·32×10^?4 μm h^?1 at 28°C, 2·59×10^?4 μm h^?1 at 65°C and 3·53×10^?4 μm h^?1 at 90°C. At 28°C, the polarisation resistance R_p values obtained from impedance spectrum were higher (in kΩ) when compared to R_p values at 65 and 90°C, indicating a lower corrosion rate at lower temperature. Comparative studies with 2·5 mM H₂SO₄ and platinum (as a working electrode) showed the effects of oxidising nature and participation of additional redox reactions in HMnO₄ medium. Cyclic polarisation studies showed the absence of pitting attack on zircaloy-2.     

Investigation of electroless copper plating on polyurethane foam,as an initial step of open cell foam production process

Abstract

Coating of polymeric foams is known as a method for production of metallic foams, which produces foams with high volume of porosity and controllable pore size. In this research, this method was employed to produce open cell copper foam by use of polyurethane foam with an average pore size of 0.4?mm as the substrate. Since polyurethane foam as a non-conductive material is not able to be coated directly by electrolytic deposition, the substrate was initially metallised by electroless copper plating. In the electroless plating process, the effects of the main parameters such as bath chemical composition, solution pH and temperature on deposition rate and thickness of the coatings obtained were investigated. The results showed that the optimum condition of the process is obtained when CuSO₄ concentration in the deposition bath is 12?g?L^??1, pH is 13 and plating temperature range is 55–60°C.     

Development of metallised polyester fabric by electroless copper for aircraft application using glyoxylic acid as reductant

Electroless copper deposition on polyester fabric using glyoxylic acid (CHOCOOH) as a reductant has been investigated. Surface morphology, composition and crystal structure of copper coating on polyester fabric were characterised by scanning electron microscopy, energy-dispersive X-ray analysis and X-ray diffraction, respectively. The surface resistance of copper-plated polyester fabric was evaluated. When the concentration of glyoxylic acid was 12?g?L^?1, the deposition rate was 49.3?mg?cm^?2?h^?1 and the surface resistance was at a minimum of 24.8?mΩ?sq^?1, which has a potential application in electromagnetic interference shielding for aircraft.     

Electrodeposition,characterisation and mathematical model of nickel–iron film in a parallel plate flow system

Abstract

Nickel–Iron alloy films were electrodeposited in a parallel plate flow system. The volumetric flow rate of electrolyte was fixed at 12 dm³ min^?1 through the 1 cm thick and 9 cm wide slit parallel plate. Fluid velocity was ca 0.22 m s^?1 under fully turbulent convective flow. Alloy films with iron content varying from 7·5 to 40 wt-% were deposited as a function of solution pH, temperature, bath ingredient concentration and applied current density. It is shown that the magnetic property is strongly correlated to the alloy content: the saturation moment, B _s, increases with the iron composition, while the coercivity, H _c, increases with nickel content. Current efficiency increases with pH and applied current density. The nickel deposition rate is inhibited in the presence of ferrous ion in the plating bath. The microhardness of the deposit is increased as the iron content is increased over the range studied. A mathematical model that considers the convective mass transfer of Fe(II) and Ni(II) species in the diffusion layer, the competition of adsorbed metal species on surface active sites, and Tafel electrochemical kinetics describe the alloy plating system well.     

Fabrication of thin copper mesh for electromagnetic interference of display panel by pulse reverse current method and study on the microstructure by small angle neutron scattering

A copper sheet with mesh was mass-produced by continuously combining three techniques, electroforming with pulse-reverse current, transfer technique onto a transparent polyimide (PI) film and oxidation processes. Thiourea as an organic additive in a modified copper sulfate bath changes the reduction potentials of copper complexes, which results in effectively controlling the crystal orientation, surface roughness and microstructure of the copper layer. An electroformed copper layer without thiourea has a relatively rough surface with an average surface roughness of about 144.7 nm, whereas, the copper layers with thiourea have a smooth surface with an average surface roughness in the range of 6.3 to 12.1 nm. The copper layers with thiourea have a preferred orientation of crystal structure such that Cu (111) peak intensity increases, whereas, Cu(220) peak intensity decreases with thiourea addition. Electroforming with a rectangular pulse current density including etching at +640 mAcm^?2 for 1.8 msec and plating at ?160 mAcm^?2 for 4 msec in a modified copper sulfate bath with 200 ppm-thiourea at 25 °C is one of optimum conditions to massproduce a copper mesh sheet roll with 300 ??m pitch, 10 ??m mesh width and thickness, and 200 m long.     

Influence of sulphate and chloride ions on corrosion of 63–37 brass in aqueous ammonia containing copper

Abstract

The influence of copper added as metallic powder, cupric sulphate, or cupric chloride to 15·7M NH₄OH on the dissolution and tarnishing of 63–37 brass in this medium was studied using weight loss and electrochemical methods. Copper added as electrolytic metal powder accelerated the dissolution of brass in ammonia. The dissolution rate increased with increase in copper concentration to 4 g l^?1, beyond which the rate decreased because of the formation of a black tarnish film. When copper was added as cupric sulphate or cupric chloride it was found that at low concentrations sulphate and chloride ions had no significant effect on the dissolution of brass, whereas at higher concentrations they enhanced dissolution. Both these ions prevented formation of the tarnish film on the brass surface. When copper was present in the ammonia the corrosion of brass occurred via a cathodically controlled process. The presence of SO^2?₄ and Cl^? produced high anodic dissolution currents. Open circuit potential values of the brass in these solutions and their variation with time were measured. The results are interpreted with reference to the chemistry of the systems under study.     

High rate of copper electrodeposition from the hexafluorosilicate bath

A high-rate copper electrodeposition performed from a hexafluorosilicate bath is presented in this article. It is shown that the current density for electrodeposition ranges from 1 to 30 A dm^− 2 and the optimal suggested current density is 15 A dm^− 2 or a rate of 200 μm h^- 1. High plating rate is due to a higher mass transport through the hexafluorosilicate media when compared to a conventional sulphate-based bath. The microstructure, texture and mean grain size of the 30 μm-thick films plated from the additive free bath and the bath containing 10^− 3 mol dm^− 3 thiourea and 500 ppm Cl⁻ is studied with respect to the applied current density. Copper plated from the bath without additives has a macrocrystalline structure with preferable 110 texture and mean grain size of 65-85 nm, while thiourea produces a microsmooth surface and 111 texture with grain size of 40-70 nm.     

Investigation of corrosion resistance of electrodeposited Ni–W/SiC composite coatings

In this research, Ni–W/SiC composite coatings were electrodeposited from a plating bath containing suspension of SiC particles. The influences of SiC particle concentration in the plating bath on the composition of composite coatings were investigated. The surface morphology and composition of the composite coatings were characterised by scanning electron microscopy, energy dispersive X-ray measurements and X-ray diffraction analysis. The corrosion characteristics of Ni–W/SiC composite coatings were investigated by mass loss and electrochemical measurements, including open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarisation in a 3·5 wt-%NaCl solution. The results showed that the addition of SiC particle to the deposition bath of Ni–W significantly increased the corrosion resistance. The significant improvement in corrosion resistance observed for Ni–W/SiC composite coatings (17100 Ω cm²) compared to Ni–W (5619 Ω cm²) could have resulted from the microstructural differences.     

Copper-Ti3SiC2 composite powder prepared by electroless plating under ultrasonic environment

In this article, a new type of Cu-Ti3SiC2 composite powder prepared using the electroless plating technique was introduced. The initial Ti3SiC2 particles are 11 μm in diameter on an average. The Cu plating was carried out at middle temperature （62-65℃） with the application of ultrasonic agitation. The copper deposition rate was determined by measuring the weight gain of the powder after plating. It has been found that the pretreatment of Ti3SiC2 powder is very important to obtain copper nanoparticles on the surface of Ti3SiC2 The optimum procedure before plating aimed to add activated sites and the adjustment of the traditional composition of the electroless copper plating bath could decelerate the copper deposition rate to 0.8 gm/h. X-ray diffraction （XRD） indicates that the chemical composition of the plating layer is copper. SEM images show that the surface of the Ti3SiC2 particles is successfully coated with continuous copper layer. The wetting property between the copper matrix and Ti3SiC2 can be improved so as to increase the interfacial strength.     

Corrosion stability of electrodeposited cyclic multilayer Zn–Ni alloy coatings

Abstract

This paper reports on a study of electrodeposition and characterisation of cyclic multilayer coatings of Zn–Ni alloy from a sulphate bath. Cyclic multilayer alloy coatings were deposited on mild steel through the single bath technique by appropriate manipulation of cathode current densities. The thickness and composition of the individual layers of the CMA deposits were altered precisely and conveniently by cyclic modulation of the cathode current during electrodeposition. Multilayer deposits with sharp change in composition were developed using square current pulses, using thiamine hydrochloride and citric acid as additives. Laminar deposits with different configurations were produced and their corrosion behaviours were studied by AC and DC methods in 5%NaCl solution. It was observed that the corrosion resistance of the CMA coating increased progressively with the number of layers (up to certain optimal numbers) and then decreased. The decrease in corrosion resistance at high degree of layering was attributed to interlayer diffusion due to less relaxation time for redistribution of metal ions at cathode during deposition. The coating configurations have been optimised for peak performance of the coatings against corrosion. It was found that CMA coating developed at cyclic cathode current densities of 3·0/5·0 A dm^?2 with 300 layers showed the lowest corrosion rate (0·112×10^?2 mm/year) which is ～54 times better than that of monolithic Zn–Ni alloy, deposited from the same bath. The protection efficacy of CMA coatings is attributed to the difference in phase structure of the alloys in successive layers, deposited at different current densities, evidenced by X-ray diffraction analysis. The formation of multilayers and corrosion mechanism were examined by scanning electron microscopy.     

Influence of Bath Compositions and Some Operating Conditions on the Electroplating of Cobalt from Aqueous Sulphate Baths

A systematic study has been made of the influence of aqueous sulphate bath constituents on the cathodic polarization curves during cobalt electrodeposition. The optimum bath composition has been established and it contains: 0.30 mol l^?1 CoSO₄.7 H₃0, 0.30 mol^?1 H₃BO₃. 0.05 mol l^?1 (NH₄)₂SO₄ and 0.10 mole l^?1 Na₂SO₄.10 H₂o. Cobalt electroplating from the optimized bath has been performed under a variety of conditions viz: pH, 1.5 to 5.3; current density, 0.2 to 2.0 A dm^?2 and temperature 25 to 53°C. Under the most suitable conditions, the optimum bath is characterized by a high cathodic efficiency (~ 99%), moderate throwing power (21.6%) and throwing index (1.47). The bath produced smooth, adherent and semibright plates characterized by a high microhardness (411.4 kgf mm^?2) and their morphologies, as revealed by scanning electron microscopy, showed a dependence on the plating variables.     

Electrochemical behaviour of zinc acetate complexes: a cyclic voltammetry study

Abstract

The search for eco-friendly non-cyanide zinc plating solutions has resulted in the development of zinc acetate baths. Cyclic voltammetric studies of the dissolution and deposition of zinc in the presence of acetate complexes were carried out. In the pH range of 4·5–5·5, zinc acetate complexes underwent successive reduction to zinc. Acetate ions and OH^? ions were shown to affect both the dissolution and deposition of zinc. The dissolution of zinc required the participation of OH^? ions.     

Electro-deposition behaviors of trivalent chromium during pulse plating

Thick trivalent chromium layers were prepared in a modified chromium sulfate bath by pulse plating to replace hexavalent hard chromium coating in industrial fields; layer microstructure development was systematically studied by using electron microscopy and small angle neutron scattering (SANS) to give a model for nucleation and growth behaviors during the pulse plating. Finer columnar grain was formed by pulse plating due to its high nucleation rate at the same current density. Average deposition rate of the trivalent chromium layers is in the range of 32.4 μm/h to 49.7 μm/h. The deposition rate increases as the diameter of cylindrical shape of chromium cluster in a columnar grain is reduced. The highest deposition rate in this study was observed under the conditions of direct current density of 0.4 Acm⁻², combined with a rectangular shape pulse current density of 1.5 Acm⁻² with a 10/2 on-off time ratio. Most of the inner-cracks of the trivalent chromium layers have dimensions in the range of about 39 nm. Ultrasonic agitation during pulse plating resulted in an increase of neutral salt fog spray life, which is related to smaller crack size and broader size distribution in the trivalent chromium.     

Influence of SiO2 particles on zinc–nickel electrodeposition

Abstract

Zinc–nickel/SiO₂ electrodeposits have been produced from an acid sulphate bath. The complimentary (mutual) codeposition behaviour of SiO₂ and nickel was observed. The presence of SiO₂ in the zinc–nickel bath appears to change the alloy deposition behaviour. Rate of nickel deposition was considerably increased with SiO₂ particles in the bath. Similarly, nickel ions were found to enhance the rate of SiO₂ incorporation. The effect of particle size studied revealed that the rate of incorporation of larger (2 μm) particles was higher than that of the smaller (20 nm) particles. Changes in hydrodynamic conditions of the composite bath seem to influence the mass transport of nickel ions hence there is a notable increase in the rate of nickel deposition and SiO₂ incorporation. Morphological studies show that the presence of SiO₂ in the bath seems to have a marked effect on the morphology and microstructure of the zinc–nickel coatings. Cathodic polarisation studies carried out during electrodeposition show a decrease in cathodic current densities with increasing SiO₂ concentration in the bath.     

Evaluation of corrosion resistance of electrodeposited nanocrystalline Ni–Fe alloy coatings

Nickel–iron alloys with a compositional range of 24–80?wt-% iron were electrodeposited on a copper substrate from a sulphate-based bath and using a stirring rate of 100?rev?min^?1. The effect of applied current density and Ni²⁺/Fe²⁺ metal ion ratio of plating bath on the properties of alloy coatings was examined. Crystal structure and grain size of Ni–Fe alloy coatings were investigated using X-ray diffraction technique. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy were used to analyse the surface morphology and chemical composition of coatings. Microhardness test was applied to evaluate the hardness of the coatings. Finally, the electrochemical behaviour of the Ni–Fe alloy coatings was studied by a polarisation test in 10?wt-% H₂SO₄ solution. Results revealed that current density and plating bath composition had a strong effect on the characteristics of coatings. As the iron content of alloys produced increased, their corrosion resistance improved with the best corrosion resistivity being achieved at a metal ion ratio of 0.5 and applied current density of 2.5?A?dm^?2.     

A Study of Benzotriazole as an Addition Agent for Acid Copper Sulphate Solutions

During a study of addition agents for acid copper sulphate solution, it has been shown that benzotriazole forms an insoluble cuprous complex which codeposits with the copper^1a A method has been devised for dissolving the deposit and separating the addition agent and it has been deffionstrated that benzotriazole can be recovered from the electrodeposit in the undecomposed form.² Since benzotriazole can be separated and estimated with accuracy, it provides a compound which is eminently suitable for studying addition agent action during electrodeposition. Polarization studies have shown that benzotriazole markedly increases the activation overpotential of the cathode η_A—mainly by decreasing the active area of the surface by film formation—and it is possible to detect 10^?7 M benzotriazole from its effect on the cathode overpotential. Additions of 0·012 g/1 benzotriazole give very fine grained deposits of copper and prevent epitaxy, while higher concentrations (0·12 g/1) result in fully-bright deposits with a banded structure. The effect of plating variables on the amount of benzotriazole included in copper deposits has been studied as a necessary prerequisite for suggesting a mechanism of addition agent action which, in this particular system, has been based on the formation of metal complexes.