Electrodeposition of tin-cobalt alloy as a replacement for decorative chromium

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Fig. 6: Throwing power of Sn-Co electrolyte compared with that for decorative chromium

Tin-cobalt alloys were electrodeposited onto nickel-plated brass substrates using a pyrophosphate electrolyte. Deposition conditions were as follows: current density, 0.2-0.3 A/dm2, bath temperature, 45±2°C, pH 8-8.2, ratio of Sn:Co 1.2:1 and current efficiency, approximately 90%. The bath exhibited good throwing power. Deposit morphology was uniform, with cauliflower-like microstructure, mean grain size 125nm. Visual appearance was very similar to electrodeposited chromium with a bluish-white colour. Electrochemical corrosion measurements using Tafel extrapolation and impedance data (as Nyquist plots) showed that Sn-Co alloy and decorative chromium had comparable corrosion resistance with values of 7.77*10-7 A/cm2 and 200 000 Ωcm2 respectively. The results demonstrate that electrodeposited tin-cobalt alloy can be a viable replacement for decorative electroplated chromium.

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Oxide Films on Sintered Tantalum for Electrolytic Capacitors

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1. Introduction

Electrolytic capacitors are characterized by the phase sequence electronic conductor / dielectric medium / electrolyte where the electronic conductor is a metal (typically Al or Ta) or an oxide (NbO) and the dielectric medium is an insulating oxide film (Al2O3, Ta2O5, SiO2, and Nb2O5). The electrolyte is a viscous or solid. Electrolytes are usually defined as ionic conductors, but for electrolytic capacitors the electronic conductivity is predominant.

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Choline chloride-Ethylene glycol mixture as electrolyte for nano crystalline Nickel electrodeposits

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Fig. 1a: Comparison of conductivity of Ni(II) chloride dissolved in Ethaline complex

Nickel plating was carried out in stable Nickel ion based deep eutectic solvent (DES). The DES electrolyte stability and possible structure were explained by using Fourier Transform Infrared spectroscopy (FTIR) and Temperature Modulated Differential Scanning Calorimetry (TMDSC) techniques. The conductivity and electrochemical studies for choline based eutectic solvents were analyzed by conductivity cell and electrochemical impedance spectroscopy respectively. Higher current efficiency, thickness and hardness of Nickel were obtained by Pulse current electrodeposition when compared with Direct current electrodeposition. Crystallographic orientation and structural morphology were studied by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM) respectively. Coated Nickel plate’s corrosion resistance and porosity properties were checked using potentiodynamic polarization and electrochemical impedance spectroscopy.

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Evaluation of Hydrogen Embrittlement Value Due to the Electroplating of Steel Springs

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Fig. 3: Tensioning device used in this study.

Electroplating is a conventional process for spiral springs coating. One of the major problems in this process is considered to be the undesirable reaction leading to hydrogen embrittlement. Taking into account the application of springs in dynamic conditions, any ductile reduction may cause sudden and quick fracture. Unfortunately, hydrogen embrittlement in steel springs will not come along with any special signs. In addition, evaluation of hydrogen penetration and its consequent embrittlement requires very complex laboratory works, and is time consuming with little repetition due to its being affected by surface conditions as well as steel springs variations.

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Electrochemical deposition and characterization of nanocrystalline Fe-Ni coatings

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Fig.1: Variation of metal contents in the deposit with applied c.d.

Nanocrystalline Fe-Ni coatings were electrodeposited on mild steel (MS) panels at different current densities (c.d.) from an acid sulphate electrolyte. The operating parameters were optimized for best appearance and performance of the coatings. Different techniques like Field Emission Gun Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Analysis (EDXA), X-Ray Diffraction, potentiodynamic polarization scan and Electrochemical Impedance Spectroscopy (EIS) were employed to characterize the electrodeposited thin films. The electrodeposition process was found to be anomalous with 35% to 70% Fe, depending on the current densities (c.d.) employed for deposition. The properties of all coatings were found to show close dependency with c.d., phase structure and composition of the alloys. Corrosion behaviors were studied in 5% HCl and 5% KOH medium and corrosion parameters were reported. Experimental results are discussed by relating the composition, phase structure and grain size with corrosion performance of the coatings in both acid and alkaline medium.

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