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Item Corrosion stability of electrodeposited cyclic multilayer Zn-Ni alloy coatings(2011) Bhat, R.S.; Udupa, K.R.; Hegde, A.C.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. © 2011 Institute of Metal Finishing.Item Optimization of bright Zn-Co-Ni alloy coatings and its characterization(2013) Bhat, R.S.; Hegde, A.C.Acidic sulphate bath having ZnSO4.7H2O, CoSO4.7H2O, NiSO4.7H2O and thiamine hydrochloride (THC) and citric acid (CA) in combination, was optimized for deposition of bright Zn-Co-Ni alloy coating on mild steel. Bath constituents and operating parameters were optimized by Hull cell method, for highest performance of the coating against corrosion. The effect of current density (c.d.), on deposit characters, such as corrosion resistance and hardness, thickness were studied and discussed. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion behaviors. The composition of deposits were determined by spectrophotometeric method and confirmed by EDX analysis. Surface morphology of the deposits was examined using scanning electron microscopy (SEM). The Zn-Co-Ni alloy, with intense peaks corresponding to Zn (100) and Zn (101) and Zn (110) phases, showed highest corrosion resistance, evidenced by X-ray diffraction (XRD) study. A new and cheap sulphate bath, for bright Zn-Co-Ni alloy coating on mild steel has been proposed, and results are discussed. © 2013 by CEE.Item Surface Structure and Electrochemical Behavior of Zinc-Nickel Anti-Corrosive Coating(Center of Excellence in Electrochemistry, Univ. of Tehran, 2023) Bhat, R.S.; Venkatakrishna, K.; Hegde, A.C.We report on the electrodeposition of a zinc-nickel alloy using a sulphate bath on mild steel (MS) substrate. The Hull cell experiment was used to optimize the bath composition and operating conditions. Sulphanilic acid (SA) was used as an additive for the coatings. The bath demonstrated an abnormal co-deposition with more zinc being deposited over nobler nickel. The effect of temperature and current density on the coating thickness, hardness, corrosion resistance, and weight % of Ni content in the coating was investigated. The corrosion behaviour of coated zinc-nickel alloy film in sodium chloride (wt.% 3.5) solution was investigated using potentiodynamic polarization and electrochemical impedance spectroscopic approaches. The nickel content in the coatings was determined through the colorimetric method and verified by the energy dispersive X-ray spectroscopy (EDX) technique. Atomic force microscopy (AFM) and Scanning electron microscopy (SEM) techniques were used to determine the surface roughness and surface topography, of the coatings. The results show that the zinc-nickel coatings had the highest corrosion resistance (0.213 mm y-1) at optimal current density (3A dm-2). Thus, due to their superior corrosion resistance Zn-Ni coatings have been largely used to protect the mild steel components in many industries including the automotive, military, and aerospace segments. © 2023 by CEE (Center of Excellence in Electrochemistry).Item Single-Layered Zn-Fe Alloy Electrodeposition for The Protection of Mild Steel Structures(Center of Excellence in Electrochemistry, Univ. of Tehran, 2024) Bhat, R.S.; Hegde, A.Electrodeposition of Zinc-Iron alloy has been used to improve the corrosion resistance of mild steel. This alloy plating was successfully coated on mild steel using the electrodeposition technique. Under varied deposition conditions, the zinc-iron alloy films onto the steel plate were examined. The purpose of this study is to describe the corrosion characteristics of the coated sample in 3.5% NaCl for the application of novel, sacrificial coatings for the defence of steel structures. It has been thoroughly examined how plating variables including bath composition, pH, and current density affect the composition, morphology; and corrosion properties of the coatings were discussed. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to analyze the morphological characteristics and phase structure of the coatings. The surface roughness of the coating was measured by Atomic Force Microscopy (AFM). The Vickers indenter was employed to measure the microhardness of the coated sample. The corrosion resistance of Zn-Fe alloy coatings was assessed using electrochemical impedance spectroscopy (EIS) and polarization techniques at different current densities. The new low-cost Zn-Fe alloy coating was used for automobile applications. © 2024 by CEE (Center of Excellence in Electrochemistry).Item Electrochemical study of Zn-Fe alloy coatings on mild steel for automotive applications(Chulalognkorn University, 2025) Bhat, R.S.; Hegde, A.This study investigates the electrochemical behavior of Zn-Fe alloy deposited on mild steel (MS) substrates for automotive applications. The electrodeposition of a Zn-Fe alloy onto MS using an acid chloride bath, with 1,2,4-Triazole as an additive to enhance the uniformity of the deposit. The hull cell method was used to optimize the bath composition and operating conditions. The coatings were produced using electrodeposition at varying current densities, with 3 A?dm?2 identified as the optimal current density (CD) for achieving uniform coatings. The microstructural properties, including crystallite size and micro-strain, were analyzed using X-ray diffraction (XRD) and Williamson-Hall (W-H) analysis, revealing a homogenous distribution of crystallite size and strain. The impact of CD on coating features such as hardness, cathode current efficiency (CCE), thickness, and the weight % of metal contents was investigated. The corrosion resistance of the deposit was estimated using the potentiodynamic polarization and electrochemical impedance spectroscopy methods, and the results have been discussed. The structural and morphological properties of the deposit were investigated by Scanning electron microscopy (SEM). The roughness of the deposit was studied by Atomic force microscopy (AFM). The deposits containing Zn and Fe contents were confirmed by Energy-dispersive spectroscopy (EDS). The results suggest that Zn-Fe alloy coatings can provide superior protection for automotive components. © (c) 2025 Journal of Metals, Materials and Minerals. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.