Optimization Of Conditions For Electrodeposition Of Alloys Directly From Ores

The objective behind the present work is to develop a novel method for electrodeposition of alloys directly from their ores thereby avoiding costly and tedious procedures.The study involved optimization of the working parameters including the bath composition because most of them did influence the deposit quality.The alloys under consideration were ferrochromium (Fe-Cr), ferrotungsten (Fe-W) and ferrocopper (Fe-Cu) to be deposited from their respective indigenously available ores i.e. chromite, scheelite and chalcopyrite. It is the use of indigenous ores, simpler cost-effective procedure involved in the deposition and better features of the deposited alloys together with the potential for greater industrial applications that make this study significant.Making conditions of the so-called Metal Salt Method (MSM) as the starting point, experimental parameters have been optimized to achieve greater efficiency of the process as well as quality of the deposits.Optimization of the working conditions involved adjusting the bath composition for its various components and other variables such as pH, temperature, Cathodic Current Density (CCD) which was applied either as Continuous Direct Current (CDC) or Pulsed Direct Current (PDC). Considering that all the alloys contain paramagnetic metal(s)/ion(s), the study has also been under taken in the presence of weak magnetic field (upto 0.2T) which proved to significantly improve the deposit quality by decreasing the grain size in all the cases. The process efficiency has been monitored through the deposition rate (amount of alloy deposited per unit area of cathode per unit time).Morphological features of the deposits like uniformity, shine, colour etc., in the first instance, were examined by visual inspection under an ordinary microscope while for the elaborated surface properties the deposits have been monitored making use of Scanning Electron Microscopy (SEM).The alloy compositions have been determined by Atomic Absorption Spectroscopy (AAS).Energy Dispersive X-ray (EDX) was also used in some selected cases to complement the AAS results.Hardness of the deposited film was checked by a durometer.Corrosion resistance using salt spray apparatus and the acid dip test provided the chemical ‘inertness’ of the deposits.The hardness and chemical inertness of the alloys were in no way inferior to those obtained by MSM while the alloy compositions were also in the desired range.PDC coupled with 0.2T field at the respective optimized bath composition provided better quality deposits in terms of their adherence, uniformity and shine.For the Fe-Cr, Fe-W and Fe-Cu the respective optimized parameters for the best results in terms of efficiency and quality were: pH values 1.5, 7 and 2; temperature range 60-65, 65-70 and 30-35°C; CCD values 31, 35 and 10mA.cm-2