Browsing by Author "Chitharanjan Hegde, A."

Now showing 1 - 3 of 3

Anomalous codeposition and characterization of Zn-Fe alloy
(2006) Chitharanjan Hegde, A.; Thangaraj, V.
A sulphate bath containing ZnSO4. 7H2O, FeSO 4.VH2O, ascorbic acid and hexamine is proposed for the deposition of bright iron rich Zn-Fe alloy onto mild steel substrate. Due to inherent character of Fe+2 ions to oxidize into Fe+3, the main part of the current applied during electroplating is spent on the reduction of ferric ions into ferrous ions. This results in decrease of cathode current efficiencies and will give instability to the bath. Hence the present work has been carried out with ascorbic acid as antioxidant with hexamine as brightener. Hull cell studies were used to optimize the concentrations of the all constituents in the bath. The influence of bath constituents, current density (c.d.) and pH on the appearance and composition of the deposits were examined. A stable bath has been formulated for deposition of Zn-Fe alloy having about 60% Fe for automobile application, by choosing very less zinc content (8 g/1) in the bath. The bath exhibits the anomalous codeposition with preferential deposition of zinc as characterized by any Zn-Fe group metal alloys. It was found that the due to less Zn+2 ions in the bath, the deposition of more noble iron has not been inhibited resulting in formation of Fe rich alloy. The compositions of the deposit at different conditions were related with their brightness, thickness, hardness and their corrosion behavior. Increase of the bath temperature enhanced the percentage of more readily depositable metal (zinc) in the deposit. Thickness of the deposit increased with c.d. as a characteristic of its iron content. A very thin and bright deposit obtained at about 1 A.dm-2 is found to have about 53% iron and a thick and bright deposit at 4.0 A.dm-2 contains about 80% iron. Photomicrograph observation showed that the phase structures of the deposits are influenced by the applied c.d. and pH of the bath. The proposed bath found to give a smooth and uniform deposit (64% Fe) with good performance against corrosion at about 2.0 A.dm-2. A stable acid sulphate bath has been proposed for iron rich Zn-Fe alloy plating for automobile applications.
Electrodeposition and compositional behaviour of Zn-Ni alloy
(2007) Thangaraj, V.; Chitharanjan Hegde, A.
This paper discusses the optimization of an electroplating bath for smooth and uniform deposition of zinc-nickel alloy on mild steel. Electroplating has been carried out in a chloride bath using glycine and gelatin as additives. The effect of bath conditions and operating parameters on chemical composition, micro-hardness and appearance of the deposit have been studied and discussed. The experimental results reveal that a bright Zn-Ni alloy having about 13.6 %Ni is showing good performance against corrosion. The corrosion resistance of the deposit is found to be characteristic of its %Ni content, and is improved drastically after chrome passivation. The bath follows anomalous codeposition with preferential deposition of Zn over the entire current density range used for the study. The increase of %Ni in the deposit with current density is due to the depletion of more readily depositable Zn2+ ions at the cathode. No transition current density, at which the codeposition behaviour changed from the anomalous to normal type, was observed during the study. The increase of %Ni in the deposit at high current density (cd.) is attributed to high ratio of Ni2+/Zn2+ in the bath. The effect of temperature on the plating process showed that codeposition of metals on the cathode is diffusion controlled.
Electrodeposition of Ni-Based Alloy Coatings and Their Electrochemical Behaviours
(National Institute of Technology Karnataka, Surathkal, 2023) M, Neethu Raveendran; Chitharanjan Hegde, A.
This thesis titled ‘Electrodeposition of Ni-Based alloy coatings and their electrochemical behaviours’ details the experimental results of investigation on electrodeposition and characterization of two newly proposed binary baths of nickel, namely NiW and NiCo for improved corrosion protection and electro-catalytic activity, through different new methods of electroplating. The research work presented here is primarily on optimization of two baths, using glycine as the common additive. Deposition conditions and operating variables have been optimized for best performance of alloy coatings against corrosion, and good electro-catalytic activity of alkaline water electrolysis of HER and OER (1 M KOH). The corrosion resistance and electro-catalytic activities of conventional (monolayer) alloy coatings developed using direct current were improved drastically through different modern methods of electroplating, like composition modulated multilayer (CMM) and magnetoelectrodeposition (MED) methods. Experimental results showed that under optimal conditions, multilayer alloy coatings of both NiW and NiCo show several fold better corrosion resistance, compared to their monolayer counterparts, deposited from same bath for same time. Study of MED alloy coatings revealed that corrosion protection efficacy of monolayer alloy coatings can be increased to many fold of its magnitude by superimposing magnetic field (B), both parallel and perpendicular, applied simultaneously to the process of deposition. At the same time, the electro-catalytic activity NiW and NiCo alloy coatings from their optimal baths, have been tested for their efficacy for both HER and OER during alkaline water electrolysis. The effect of addition of nanoparticles, namely Ag nanoparticles into NiCo bath has been studied for their HER activity. The corrosion resistance and electro-catalytic activity of Ni-based alloy coatings, and their nanocomposite coatings were compared in relation to their composition, surface morphology and phase structure. The process and product of electrodeposition were characterized using CV, CP, SEM, AFM, XRD, EDS and Elemental mapping techniques. The performance of alloy coatings, developed under different conditions have been compared, and discussed with Tables and Figures.