The influence of methane sulphonic acid, naphthalene sulphonic acid and phenol sulphonic acid on the electrodeposition of nickel from a citrate buffered nickel bath was investigated. Solution characteristics such as cathode efficiency and throwing power have been assessed, and corrosion resistance of the coatings was measured by electrochemical impedance spectroscopy method. The X-ray diffraction pattern obtained for electrodeposited nickel showed a polycrystalline fcc structure. A uniform and pinhole free surface was observed under SEM analysis.

People with bipolar disorders may have relapse of mood episodes associated with sleep deprivation and postpartum states. Jet lag can cause sleep problems resulting in relapse of mood episodes in vulnerable people. Melatonin synthesized in the pineal gland will normalize the circadian rhythm and prevent the recurrence of mood episodes in predisposed people. We are reporting a case of successful use of melatonin in a 30-year old lady with history of postpartum onset mood disorder and multiple relapses of mania precipitated by jet lag.

Oculogyric crisis is a distressing acute/chronic side effect of neuroleptic medications. Chronic oculogyric crisis can be considered as a tardive hyperkinetic movement disorder and it may be associated with worsening of psychotic symptoms. Treatment strategies for chronic oculogyric crisis include; high potency antipsychotics and anticholinergics drugs for immediate relief and clozapine as a long-term treatment strategy. Here we are presenting case histories of four patients with oculogyric crisis and associated worsening of psychosis, its possible etiology and various treatment strategies.

Abstract Cyanide silver solution containing 200 to 1000 mg L−1 silver ions were used for recovery studies. The nature of the silver deposit was studied using a Hull cell, and the current density range was selected for electrolysis to recover silver. A batch electrochemical reactor, consisting of a planar stainless steel cathode and platinum anode was used and silver was recovered at 0˙04 to 0˙2 A dm−2. The effect of different initial silver concentrations on the electrochemical recovery of the metal was investigated as a function of electrolysis duration at various current densities. The cathode current efficiency and the energy consumption were determined for the solutions for various experimental conditions. Surface morphology and structure of the silver deposit was also studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that irrespective of the initial silver concentration, higher current efficiency and lower energy consumption can be achieved at a low current density. For a given current density, the energy consumption to recover silver is lower from relatively concentrated than from dilute solutions.

The present paper presents the results of a study on the development and optimisation of a chemical stripping solution for the removal of gold deposits from different substrates. This stripping solution essentially contains potassium hydroxide, potassium cyanide, sodium citrate and m-nitro benzoic acid. Rate of stripping has been studied at varying concentrations of constituents; temperatures and an optimum composition derived.

Abstract Sequential deposition of Cu–Ni was carried out on glass and mild steel substrates by electron beam evaporation technique. The films were vacuum annealed at 200°C for 1 h. A smooth deposit with 7·8 μm thickness was observed using a profilometer. The polycrystalline nature with FCC structure of the films was determined with X-ray diffraction analysis. The uniform coverage of film surface was observed with atomic force microscopy (AFM). X-ray fluorescence (XRF) showed a change in composition for the vacuum annealed Cu–Ni film. A high transmittance in the visible region and a very low transmittance in the infrared region were observed for these films. Corrosion behaviour of the evaporated Cu–Ni films in 3·5% w/v NaCl solution was examined.

The electroplating industry is one of the major industries, which generate a large amount of wastewater containing heavy metals. Even though chemical treatment processes are suitable for treatment of this kind of wastewater, the high concentration of heavy metals necessitates more treatment before discharge into natural resources, as heavy metals are important sources of environmental pollution and they can form compounds, which are toxic even in very low concentrations. The only way to remove the metals is to change their chemical states by oxidation/reduction and precipitation, and recover them in an acceptable form. In the present paper studies have been carried out by ethylenediaminetetraacetic acid complexation of effluents, using cyclic voltammetry.

Increasing concern over toxic wastes produced by nickel–chromium (Ni–Cr) plating industries has resulted in strong research efforts to replace conventional plating by physical vapour deposition techniques like evaporation and sputtering. Ni–Cr coatings on mild steel substrates produced by an electron beam evaporation process with layer thickness of ∼8–10 m m have been investigated with regard to the structural and corrosion properties. The structure of the coating was evaluated by X-ray diffractometer (XRD). The (110) Cr and (200) Ni predominant peaks with the crystallite size in the range of 25–30 nm was observed from XRD pattern. The electrochemical polarisation studies performed on samples showed the corrosion resistant nature of the evaporated Cr coating with Ni underlayer on mild steel substrates. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the surface characteristics of the samples before and after the electrochemical corrosion tests. The localised corrosion through a micropore in the evaporated Cr deposit and its penetration to the Ni layer was observed from SEM. The smaller change in roughness observed from AFM reflects the resistance of this coating to corrosion breakdown.

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.

Investigations into nickel electrodeposits on dc magnetron sputtered copper substrates are reported. Thin layers of copper were deposited by dc magnetron sputtering on mild steel substrates. Onto these sputtered copper surface, layers of nickel were electrodeposited using a Watt's bath. The coatings were vacuum annealed at 200°C for 120 min. The growth of the deposit is discussed in terms of structural and microstructural analysis by X-ray diffraction (XRD), SEM and atomic force microscopy (AFM). The orientation along (111), (200) and (220) was observed for the vacuum annealed Cu3·8Ni alloy deposits. Uniform and pinhole free morphology was observed from SEM. AFM images reveal that these coatings have a granular morphology. The corrosion behaviour of these samples in a 3·5 wt-%NaCl solution was examined. A decrease in Icorr and high charge transfer resistance indicated the improved corrosion resistant behaviour of the nickel sample plated over a sputtered copper base.

ZINC ELECTRO deposits of 5, 10, and 15 microns thickness were obtained using an alkaline non-cyanide zincate bath, and some of the samples were chromated. The corrosion behaviour of the zinc deposits was studied in 3.5% NaCl solution, by both electrochemical and non-electrochemical techniques such as galvanostatic, potentiodynamic, impedance, salt-spray, and weight-loss methods. Three specimens under identical conditions were subjected to the test. Similar studies were carried out for the chromated specimens, and the results are discussed.

Zinc electrodeposits offer protection to steel against atmospheric corrosion both by galvanic and shielding effects. The cyanide process for zinc electrodeposition is increasingly being replaced by chloride and many other non-cyanide formulations. The search for a better zinc plating electrolyte is therefore a continuing process. In this paper the authors present details of zinc plating from an acetate electrolyte together with the deposit properties. The addition of thiaminehydrochloride to the plating bath improves the surface morphology of zinc electrodeposits. The X-ray diffraction data obtained for electrodeposited zinc showed it to be polycrystalline in nature with an hexagonal structure. Analysis by scanning electron microscopy demonstrated a uniform and pinhole-free surface.

Zinc electrodeposits are widely used to protect iron and steel from corrosion. Zinc coatings are presently obtained from chloride, sulfate, mixed chloride and sulfate, cyanide and non-cyanide alkaline baths. Atmospheric corrosion is associated with the use of chloride electrolytes. The use of additives, low cathode efficiency and the costly effluent treatment discourage the use of non-cyanide alkaline zinc plating baths. Hence, a better quality zinc plating electrolyte is necessary. In this paper, the authors present a detailed investigation of zinc plating from non-cyanide based acetate electrolytes and the effect of thiamine hydrochloride and gelatin as additives to produce quality bright deposits. The bath and deposit characteristics of acetate-based zinc plating was studied and the results are presented.

A search for a non-cyanide zinc plating bath resulted on the development of a zinc acetate To obtain bright zinc deposits, thiamine hydrochloride and gelatin were added. Hull cell studies revealed that in presence of 3 g dm(-3) thiamine hydrochloride a bright deposit was obtained at a current above 2.5 A dm(-3). Addition of 3 g dm(-3) gelatin produced a bright yellow tinge deposit above 2.5 A dm(-2). Voltammetric studies carried out at a glassy carbon electrode in the plating solution revealed that in the pH range of 4.5-5.5, zinc acetate complexes underwent successive reduction to zinc. Acetate ions and pH affected both the dissolution and deposition of zinc. The dissolution of zinc took place with the participation of OH- ions. Gelatin molecules adsorbed on the electrode surface. They favoured both zinc dissolution and deposition and prevented hydrogen evolution in the potential range of interest. Thiamine hydrochloride caused a reduction in zinc dissolution and deposition rates but favoured hydrogen evolution.

Zinc alloy plating is a high performance coating. Compared to pure zinc plating, zinc alloys provide several advantages. A zinc alloy will generally provide superior sacrificial protection to steel. The degree of protection and rate of corrosion depends on the alloy metal and composition. The demand for higher-quality, longer-lasting, more corrosion-resistant coatings in industries such as aerospace, fastener, electrical component and particularly, automotive has played a large role in the development and use of zinc alloy coatings. Zinc-iron alloy has good weldability and ductility. In this paper the corrosion resistance properties of zinc-iron deposited from a sulphate bath are evaluated by electrochemical methods and the results are discussed.

The performance of anode is of considerable importance in determining the success of an electroplating process. Usually anodes used for electroplating are of two types namely (i) soluble and (ii) insoluble. Mostly soluble anodes are used in almost all the plating electrolytes in view of maintaining the concentration of cations as required. However under certain critical conditions, it becomes a must to use in soluble anodes. Such characteristically significant anodes, behave differently in the baths when their position, size, shapes etc, are changed. This aspect is not elaborately investigated and reported in the literature. investigations were carried out in the conventional cyanide and acid copper baths using soluble ns well as insoluble anodes of different shapes and sizes and the results ai e reported in this paper.

SUMMARYWith a view to eliminating the use of toxic cyanide for electroplating copper, a non-cyanide alkaline bath, using triethanolamine as complexant, has been investigated. Various steps of bath developments are discussed in this paper. These include stability and immersion deposition characteristics of solutions with varying concentrations, Hull cell experiments to arrive at a plating bath composition and determination of current efficiency and deposit nature under varying operating parameters to optimise the deposition conditions.

INTRODUCTION Zinc coating is a popular corrosion resistant coating and is normally applied on various components made of iron or steel. Moreover the corrosion resistance of zinc coating may be further improved three fold with a chromate conversion coating. Zinc coatings can be obtained from cyanide or acid type electrolytes• The improved throwing power of the cyanide electrolyte favours its use in preference to the acid electrolyte. It is commonly known that when electrodeposition takes place from a bath with the desired metal in a complexed state, the throwing power of the electrolyte is improved. Hence it has been decided to study the electrodeposition of zinc from a zinc citrate electroplating bath hitherto not studied and reported upon.

Silver is used as a deposit for decorative and aesthetic appeal on jewellery, hollowers, flatware etc. It is also used in engineering industries for various reasons like high heat and electrical conductivity and good antigalling property on bearings, electronic components like socket contacts, slip rings, switch gear and wave guides for radars etc. Usually, silver is electroplated from cyanide based electrolytes and these solutions contain higher concentrations of both silver and cyanide causing heavy pollution due to effluents. Also, silver being costly, it was considered worthwhile to investigate the feasibility of evolving a bath formula with low concentration of silver as well as cyanide with equivalent characteristic features to the concentrated baths. Experiments were carried out with different concentrations of silver and cyanide and the results are compared with that of conventional cyanide based baths.

Electrodeposited layers of silver-cadmium alloys are reported to have increased hardness, electrical conductivity and tarnish resistance compared to silver. The standard electrode potentials of silver and cadmium are too far apart to permit codeposition from simple salt solutions, suitable complexing is necessary to bring the deposition potentials closer and facilitate codeposition. Results of the investigations with cyanide complexed solutions are presented in this paper. Electroplating experiments with varying concentrations of metal ions and operating conditions have shown the possibility of depositing alloys with a range of compositions. Characterisation of the deposits has been by X-ray diffraction, scanning electron microscopy and microhardness measurements. Voltammetric studies show the deposition of alloys of solid solution type at low concentrations of cadmium and a mixture of phases at higher concentrations.