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Item Development of high corrosion resistant (Ni-Fe) alloy coatings from a low concentration bath through multilayer approach(SAGE Publications Inc., 2025) Rai, T.Y.; Hegde, A.Here, we report the development of high corrosion-resistant (Ni-Fe) alloy coatings from a low-concentration bath through multilayer approach. The corrosion analysis of (Ni-Fe) alloys electrodeposited at different current densities (2.0–5.0 A/dm2) revealed that the coating developed at 2.0 A/dm2, represented as (Ni-Fe)2.0 A/dm2 is highly anticorrosive. The corrosion resistance of monolayer (Ni-Fe)2.0 A/dm2 coating, showing a corrosion rate of 14.71 × 10−2 mm/y was further improved by utilizing multilayer approach. Corrosion study revealed that multilayer coating having 120 layers, represented as (Ni-Fe)2.0/4.0/120 was six times more anticorrosive (with corrosion rate = 2.33 × 10−2 mm/y), compared to its monolayer counterpart. The improved anticorrosion performance of multilayered coatings was explained in the light of advanced instrumental techniques. © The Author(s) 2024.Item Effect of bath composition and operating parameters on deposit character and corrosion behaviour of Zn-Ni alloy(2008) Venkatakrishna, K.; Tangaraj, V.; Hegde, A.Electrodcpositcd Zn-Ni alloys arc extensively used as protective coatings for steel substrates and hence:lhe studies, on the factors which enhance corrosion resistance are of considerable significance. The present work details the optimization of acid chloride bath for bright Zn-Ni alloy over mild steel and study of the parameters which influence Ni content in the deposit. Use of sulphanilic acid and gelatin was found to show significant effect on brightness of the deposit. The effect of molar ratio of Ni+2/Zn+2 in the bath on limiting current density of nickel deposition was emphasized. Under no conditions of bath compositions and operating parameters studied, the change in codeposition behaviour from anomalous to normal type was observed. The wt. %Ni in the deposit was found to be the independent factor of its corrosion resistance. The photomicrograph of electroplates confirmed that superior corrosion resistance is due to good surface morphology. Tjhe effect of bath composition, current density (c.d.), pH and temperature on appearance, hardness and corrosion resistance oi.deposits were studied and discussed. Corrosion behaviour of electroplates has been studied by Tafel's extrapolation method. Electrochemical impedance spectroscopy analysis revealed that superior corrosion resistance of Zn-Ni alloys coatings at optimized current density is due to' barrier resistance at the interface of deposit and medium. Formation Of n-typc semiconductor film at the interface was confirmed by Mott-Schottky plot. Addition of small amount of cadmjutrrchloride did not increase corrosion resistance.Item Development of Zn-Co alloy coatings by pulsed current from chloride bath(2008) Thangaraj, V.; Udayashankar, N.K.; Hegde, A.Zinc-M (where M = Ni, Co and Fe) alloy is of great interest owing to their better mechanical and corrosion properties compared with pure zinc coatings. Corrosion resistance of Zn-Co alloy coatings can be improved considerably by pulse plating. The paper details the optimization of Zn-Co alloy bath using pulsed current and details the superiority of pulse plating over direct current plating. Electroplating of Zn-Co alloys over mild steel was carried out under different conditions of pulse parameters like duty cycle, frequency and peak current density. The production and properties of the deposits were found to be influenced by pulse parameters employed. Within the ranges studied, the bath follows anomalous codeposition with preferential deposition of less noble zinc. The influence of current density on %wt. of Co in the deposit and cathode current efficiencies was studied. It was observed that the deposit at average current density of 5.0 A.dm-2, 50% duty cycle and 100 Hz frequency showed excellent corrosion resistance with fine structure. The peak performance of pulse electrodeposit against corrosion was attributed to the change in the surface homogeneity as evidenced by scanning electron microscope (SEM) image. The drastic decrease of corrosion rate in pulse electrodeposit was attributed to the formation of semiconductor films on the surface as supported by impedance spectroscopy signals.Item Corrosion behavior of composition modulated multilayer Zn-Co electrodeposits produced using a single-bath technique(2009) Thangaraj, V.; Eliaz, N.; Hegde, A.Composition modulated alloy (CMA) electrodeposits of Zn-Co were produced from acid chloride baths by the single-bath technique. Their corrosion behavior was evaluated as a function of the switched cathode current densities and the number of layers. The process was optimized with respect to the highest corrosion resistance. Enhanced corrosion resistance was obtained when the outer layer was slightly richer with cobalt. At the optimum switched current densities 40/55 mA cm-2, a coating with 600 layers showed ~6 times higher corrosion resistance than monolithic Zn-Co electrodeposit having the same thickness. The CMA coating exhibited red rust only after 1,130 h in a salt-spray test. The increased corrosion resistance of the multilayer alloys was related to their inherent barrier properties, as revealed by Electrochemical Impedance Spectroscopy. The corrosion resistance was explained in terms of n-type semiconductor films at the interface as supported by Mott-Schottky plots. © 2008 Springer Science+Business Media B.V.Item Electrodeposition and characterization Zn-Co alloy(2009) Hegde, A.; Thangaraj, V.The present work details optimization of a stable acid chloride bath for electroplating of bright Zn-Co alloy on mild steel using gelatin and glycine as additives. It was found that the addition of gelatin along with glycine changed the deposition pattern markedly. A suitable bath has been formulated using conventional Hull cell experiments. The bath under plating conditions were found to exhibit anomalous codeposition with preferential deposition of less noble (zinc) over more noble (cobalt) as characterized by Zn-Fe group metal alloys. Investigation revealed that the current density (c.d.), temperature, and pH of the bath have strong effect on the composition of the deposit. Influence of bath constituents and operating parameters on appearance and composition of deposits were studied as measure of their performance against corrosion. A variety of deposits were obtained and their corrosion resistances were measured by Tafel method with/without chrome passivation. Experimental results demonstrated the fact that the corrosion resistances of Zn-Co alloys increased with percent of Co in the deposit except at very high c.d. This is due to the fact at very high c.d. the deposit becomes very porous and thick as evidenced by SEM image. The formation of Zn-Co alloy is confirmed by EDAX analysis. A stable chloride bath for Zn-Co alloy deposition has been proposed and discussed. The formation of passive film on chromatization is indicated by almost same E corr value of all Zn-Co electroplates irrespective of the current densities at which they have been deposited. © 2009 Pleiades Publishing, Ltd.Item Corrosion resistant Zn-Co alloy coatings deposited using saw-tooth current pulse(2011) Yogesha, S.; Hegde, A.Micro/nanostructured multilayer coatings of Zn-Co alloy were developed periodically on mild steel from acid chloride bath. Composition modulated multilayer alloy (CMMA) coatings, having gradual change in composition (in each layer) were developed galvanostatically using saw-tooth pulses through single bath technique (SBT). CMMA coatings were developed under different conditions of cyclic cathode current densities (CCCDs) and number of layers, and their corrosion resistances were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) method. Optimal configuration, represented as (Zn-Co)2 0/4.0/300 was found to exhibit ? 89 times better corrosion resistance compared to monolithic (Zn- Co)3 0 alloy deposited for same time, from same bath. The better corrosion resistance of CMMA coatings was attributed to changed interfacial dielectric properties, evidenced by dielectric spectroscopy. Improved corrosion resistance was attributed to formation of n-type semiconductor film at the interface, supported by the Mott-Schottky plot. Further, the formation of multilayer and corrosion mechanism was analysed using scanning electron microscopy (SEM). © Indian Academy of Sciences.Item Surface modification by multilayered Zn-Co alloy coatings(2012) Yogesha, S.; Udupa, K.R.; Hegde, A.Nanostructured multilayer alloy or composition modulated multilayer alloy coatings of Zn-Co have been developed, and their corrosion behaviours were studied by potentiodynamic polarization and electrochemical impedance spectroscopy methods. The coatings were developed galvanostatically using square, triangular and sawtooth current pulses through single bath technique. The cyclic cathode current density and the numbers of layers have been optimised for peak performance of the coatings against corrosion. Under optimal conditions, the coatings developed using square, triangular and sawtooth current pulses were found to be respectively y100, 80 and 90 times more corrosion resistant than monolithic alloy of same thickness. The better corrosion resistances of the composition modulated multilayer alloy coatings were attributed to the dielectric barrier at the interface, as evidenced by dielectric spectroscopy. Surface morphology, multilayer formation and surface after corrosion tests were examined by scanning electron microscopy. © 2012 Institute of Materials, Minerals and Mining.Item Hardness and electrochemical behavior of ceramic coatings on inconel(International Association of Physical Chemists, 2012) Sujaya, C.; Shashikala, H.D.; Umesh, G.; Hegde, A.Thin films of ceramic materials like alumina and silicon carbide are deposited on Inconel substrate by pulsed laser deposition technique using Q-switched Nd: YAG laser. Deposited films are characterized using UV-visible spectrophotometry and X-ray diffraction. Composite microhardness of ceramic coated Inconel system is measured using Knoop indenter and its film hardness is separated using a mathematical model based on area-law of mixture. It is then compared with values obtained using nanoindentation method. Film hardness of the ceramic coating is found to be high compared to the substrates. Corrosion behavior of substrates after ceramic coating is studied in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The Nyquist and the Bode plots obtained from the EIS data are fitted by appropriate equivalent circuits. The pore resistance, the charge transfer resistance, the coating capacitance and the double layer capacitance of the coatings are obtained from the equivalent circuit. Experimental results show an increase in corrosion resistance of Inconel after ceramic coating. Alumina coated Inconel showed higher corrosion resistance than silicon carbide coated Inconel. After the corrosion testing, the surface topography of the uncoated and the coated systems are examined by scanning electron microscopy. © 2012 by the authors; licensee IAPC, Zagreb, Croatia.Item Magnetic property and corrosion resistance of electrodeposited nanocrystalline iron-nickel alloys(Elsevier B.V., 2012) Pavithra, G.P.; Hegde, A.In the present investigation we have galvanostatically synthesized nanocrystalline Fe-Ni alloys on copper substrate. The effect of current density (c.d.) on composition, surface morphology and phase structure were studied for explaining the magnetic and electrochemical properties of the nanocrystalline alloy. The bath found to exhibit the preferential deposition of less noble Fe than Ni, and at no conditions of c.d., the deposition has changed from anomalous to normal type. Surface morphology and structural characteristics of the deposits were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. As composition of the alloy varied, consequent to the current density a change of body centered cubic structure (bcc) to face centered cubic structure (fcc) was observed for nanocrystalline materials. Finally, the conditions responsible for peak magnetic property and corrosion resistance were optimized. Factors responsible for improved functional properties were explained in terms of surface morphology and crystalline grain size of the coatings. © 2012 Elsevier B.V.Item Effect of surfactant on high capacitance of galvanostatically deposited MnO2(Elsevier B.V., 2012) Suhasini; Hegde, A.Manganese dioxide has been galvanostatically deposited on stainless-steel substrate from an aqueous acidic solution of manganese sulphate (1 M) in presence of a surface active agent (surfactant), namely, sodium lauryl sulphate (SLS), for supercapacitor applications. The deposits have been developed under different conditions of SLS and their specific capacitance is measured by cyclic voltammetry (CV) and also by galvanostatic charge/discharge cycle. The oxide film (?0.1 mg cm-2) anodized from the manganese solution at 2.0 mA cm-2 has shown the highest specific capacitance of 255.8 F g -1, at scan rate of 10 mV s-1. It is observed that the capacitance increased by about 40% compared to the oxide prepared in the absence of SLS. Improved specific capacitance is due to the effect of the surfactant molecules in the deposit, causing high surface area of the deposit. The deposit is found to display good cycleability, even up to 1500 cycles. The structure and surface morphology of the deposits have been studied by means of X-ray diffraction (XRD) analysis and Scanning Electron Microscopy (SEM). XRD study reveals that crystallinity of the deposit with SLS remains unchanged, both are amorphous in nature. The surface area of the deposit is found to increase considerably due to the effect of SLS, as evident by SEM study.© 2012 Elsevier B.V. All rights reserved.