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Item Effect of pH on Electrodeposition of Ni–Cd Alloy Coatings and Their Anticorrosion Performance(Springer Nature, 2022) Gonsalves, C.N.; Sneha, I.M.; Hegde, A.C.Electroplating is a complex process controlled by bath composition and operating parameters. Among many operating parameters, the pH of the bath plays an important role in the process of deposition and properties of coatings. The present paper reports the effect of pH in the electrodeposition process of Ni–Cd alloy coatings from a low concentration bath of Ni–Cd alloy, using glycine as an additive. The experimental results revealed that change of pH over a wide range (from lower acidic to higher basic conditions) has a significant effect on the structure, morphology, and composition of the alloy electrodeposits. A considerable increase in the uniformity of coatings was found with an increase in bath pH. Electrochemical corrosion study carried out in 3.5% NaCl medium demonstrated higher corrosion resistance for Ni–Cd alloy coating, deposited at pH 8.0 compared to those deposited at lower pH. A change in the process of electro-crystallization was found with the change of pH, confirmed by the scanning electron microscopy (SEM) study. The improved corrosion resistance of alloy coatings was ascribed to the change of codeposition from anomalous to normal type, known by its Ni content confirmed by the energy dispersive X-ray spectroscopy analysis (EDAX). A change in phase structure was found with the change of pH, confirmed by the X-ray Diffraction (XRD) technique. Experimental results are analyzed in light of the theory of alloy deposition, and results are discussed. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Magnetically induced electrodeposition of Zn-Ni alloy coatings and their corrosion behaviors(Elsevier B.V., 2013) Rao, V.R.; Bangera, K.V.; Hegde, A.C.The less magnetic features of Zn-Ni alloy compared to Fe-Ni and Fe-Co alloys made it interesting to develop them under the influence of applied magnetic field. In this regard, the effects of a magnetic field (B) applied in a direction parallel and perpendicular to the nominal current, during electrodeposition process of Zn-Ni alloy have been investigated by means of X-ray diffraction and EDX analysis. The modification of crystal orientation by superimposition of a varying magnetic field is studied for alloys of constant nickel content (8 a %.), deposited at optimal current density (j) of 3.0 A dm-2. The effect of magnetic field on crystallographic orientation and hence the corrosion behaviors of the coatings were studied. The preferential orientations (101) and (002) of the zinc phase and (330) ?-Ni 5Zn21 phase are always favored to exist with parallel and perpendicular magnetic field. The preferential (321) ?-Ni 5Zn21 orientation is found to be the characteristic of perpendicular magnetic field. Further, Zn (100) orientation is found to be non-responsive to the effect of parallel magnetic field. The coatings developed using perpendicular magnetic field is more corrosion resistant compare to that for parallel magnetic field. This is attributed to the additional (321) ?-Ni5Zn21 orientations. The changes in the phase structure of the coatings deposited at different magnetic field are attributed to the effect caused by the magnetic convection induced in the electrolytic solution, called MHD effect (magneto-hydrodynamic effect). The chemical composition of the alloy was found to be same in both natural and magnetically induced deposition due to constant Ni content in the bath. The variation in the surface morphology of the coatings was studied by scanning electron microscopy (SEM). The Zn-Ni alloy coating deposited at 0.8 T perpendicular B showed the highest corrosion resistance (with corrosion rate=0.26 × 10-2 mm y-1) compared to the one with no B (corrosion rate = 14.46 × 10-2 mm y-1). The improved corrosion resistance of the coatings was discussed in the light of magnetic field effect on crystallographic orientation. © 2013 Elsevier B.V. All rights reserved.Item Corrosion protection of electrodeposited multilayer nanocomposite Zn-Ni-SiO2 coatings(2013) Ullal, Y.; Hegde, A.C.Multilayer nanocomposite coatings of Zn-Ni-SiO2 were deposited galvanostatically on mild steel (MS) from Zn-Ni bath, having Zn+2 and Ni+2 ions and uniformly dispersed nano-SiO2 particles. The corrosion characteristics and properties of multilayered nanocomposite (MNC) coatings were evaluated by electrochemical polarization and impedance methods. Such deposition conditions as, bath composition, cyclic cathode current densities (CCCD's) and number of layers were optimized for peak performance of coatings against corrosion. A significant improvement in the corrosion performance of MNC coatings was observed when a coating was changed from a monolayer to multilayer type. Corrosion rate (CR) of MNC coating decreased progressively with number of layers up to an optimal level, and then started increasing. The increase of CR at a higher degree of layering is attributed to diffusion of layers due to a very short deposition time, failing to give the enhanced corrosion protection. The formation of layers, inclusion of silica particle in MNC coating matrix were confirmed by SEM and XRD study. At optimal current densities, i.e. at 3.0-5.0 A/cm2, the Zn-Ni-SiO2 coating having 300 layers, represented as (Zn-Ni-SiO2)30/5.0/300 is found to be about 107 times more corrosion resistant than a monolayer Zn-Ni-SiO2 coating, developed from the same bath for the same time. The reasons responsible for the extended corrosion protection of MNC Zn-Ni-SiO2 coatings, compared to corresponding monolayer Zn-Ni and (Zn-Ni-SiO2) coatings were analyzed, and results were discussed. © 2013 Allerton Press, Inc.Item Effect of magnetic field on corrosion protection efficacy of Ni-W alloy coatings(Elsevier Ltd, 2017) Elias, L.; Hegde, A.C.High corrosion resistant Ni-W alloy coatings were developed using magnetoelectrodeposition (MED) approach for the protection of mild steel substrates. The conditions for the development of more corrosion resistant MED Ni-W alloy coatings were optimized by inducing a magnetic field (B) during deposition, in terms of intensity and direction. The applied magnetic field was used as a tool to alter the crystallinity, composition and thereby the corrosion resistance of the coatings. It was demonstrated that the corrosion resistance of Ni-W alloy coatings can be improved to many folds of its magnitude by MED approach. Significant increase in corrosion resistance exhibited by MED coatings (under both parallel and perpendicular magnetic field, B) is attributed to the increased W content of the alloy affected by an increase in limiting current density (iL). The high corrosion resistance of the MED Ni-W alloy coatings was explained in the light of magnetohydrodynamic (MHD) effect, responsible for the increased W content, brought about by the enhanced mass transport. The inherent limitations of the bath like low iL and induced type of codeposition which impedes the development of W rich alloy coatings has been successfully resolved by MED method. Drastic improvement in corrosion resistance is ascribed to the basic difference in the process of electrocrystallization and phases formed during MED, confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. The results are discussed with greater insight into binary alloy deposition and mass transfer process at cathode/electrolyte interface. © 2017 Elsevier B.V.Item Inhibition effect of a new pyrimidine derivative on the corrosion of mild steel in hydrochloric acid solution(Allerton Press Incorporation journals@allertonpress.com, 2017) Shetty, P.B.; Suresha Kumara, T.H.; Mamatha, D.M.; Rao, V.R.; Hegde, A.C.The inhibition effect of a newly synthesized pyrimidine derivative, namely 3-(2-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)ethyl)-2-methyl-6,7,8,9-tetrahydropyrido[1,2-a]pyrimidin-4-one, on the corrosion of mild steel in 1.0 M HCl medium was investigated using the weight loss, the Tafel extrapolation technique and the AC impedance spectroscopy. The effect of the inhibitor concentration, temperature and concentration of the acid mixture media on the inhibitor action was also studied. It was observed that the anti-corrosion efficiency increases with an increase in the inhibitor concentration, but decreases with an increase in temperature. Thermodynamic parameters for the dissolution process were determined. The adsorption of the pyrimidine derivative on the mild steel surface was found to obey the Langmuir adsorption isotherm. © 2017, Allerton Press, Inc.Item Magnetically Induced Electrodeposition of Ni-Mo Alloy for Hydrogen Evolution Reaction(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Shetty, S.; Hegde, A.C.The electrocatalytic activity of Ni-Mo alloy coatings for hydrogen evolution reaction (HER) was tried to increase by inducing the magnetic field (B), perpendicular to the process of deposition. The electrocatalytic activity of Ni-Mo alloys were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) measurements in 1.0 M KOH medium. Ni-Mo alloy coatings developed at c.d. = 1.0 A dm?2 and B = 0.4 T was found to exhibit highest electrocatalytic activity for HER (with highest cathodic peak c.d. of ?0.274 A cm?2 and least onset potential of ?1.24 V and highest volume of H2 liberated, 14.0 mL), demonstrated by CV and CP experiments. The stability factor of Ni-Mo alloy coatings were evaluated through corrosion study. The experimental results showed that Ni-Mo alloy, electrodeposited in the presence of B, is more corrosion resistant than its conventional alloy, when tested in the same alkaline medium. The increase in the electrocatalytic activity of Ni-Mo alloy coatings, developed under induced B, is attributed to the structural and morphological changes, caused by an increase of Ni content in the alloy, evident from X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. [Figure not available: see fulltext.] © 2017, Springer Science+Business Media New York.Item Electrodeposition and characterization of Ni-Mo alloy as an electrocatalyst for alkaline water electrolysis(Elsevier B.V., 2017) Shetty, S.; Mohamed, M.; Bhat, D.K.; Hegde, A.C.This work details the efficiency of Ni-Mo alloy as an electrode for water splitting application through electrodeposition method. Nano-crystalline Ni-Mo alloy coatings were deposited in the current density (c.d.) range of 1.0–4.0 A dm? 2 on a copper substrate, and were investigated for their deposit characters, and their electrocatalytic behaviours in 1.0 M KOH solution. The electrocatalytic behaviour of the coatings, in terms of their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), were evaluated by electrochemical methods, like cyclic voltammetry (CV) and chronopotentiometry (CP). Experimental results revealed that Ni-Mo alloy electrodeposited at 1.0 A dm? 2 (38.3 wt% Mo) and 4.0 A dm? 2 (33.2 wt% Mo) shows the highest electrocatalytic tendency for HER and OER, respectively. The corrosion behaviour of Ni-Mo alloy coated at 4.0 A dm? 2 is found to be the most corrosion resistant in the same alkaline medium, compared to other coatings. The highest electrocatalytic activity of Ni-Mo alloy deposit for both HER and OER, depending on deposition c.d. was attributed to their composition (in terms of Ni and Mo content), structure and surface morphology; supported by EDXA, XRD, SEM and AFM analyses. The experimental study demonstrated that Ni-Mo alloy coatings follow Volmer-Tafel type of mechanism for HER, testified by Tafel slope analyses. © 2017 Elsevier B.V.Item Effect of TiO2 nanoparticles on hydrogen evolution reaction activity of Ni coatings(University of Science and Technology Beijing, 2018) Kullaiah, R.; Elias, L.; Hegde, A.C.The electrocatalytic activity of electrodeposited Ni and Ni–TiO2 coatings with regard to the alkaline hydrogen evolution reaction (HER) was investigated. The Ni coatings were electrodeposited from an acid chloride bath at different current densities, and their HER activities were examined in a 1.0-mol·L-1 KOH medium. The variations in the HER activity of the Ni coatings with changes in surface morphology and composition were examined via the electrochemical dissolution and incorporation of nanoparticles. Electrochemical analysis methods were used to monitor the HER activity of the test electrodes; this activity was confirmed via the quantification of gases that evolved during the analysis. The obtained results demonstrated that the Ni–TiO2 nanocomposite test electrode exhibited maximum activity toward the alkaline HER. The surface appearance, composition, and the phase structure of all developed coatings were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively. The improvement in the electrocatalytic activity of Ni–TiO2 nanocomposite coating toward HER was attributed to the variation in surface morphology and increased number of active sites. © 2018, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.Item Studies on electrodeposited Zn-Fe alloy coating on mild steel and its characterization(International Association of Physical Chemists zmandic@fkit.hr, 2019) Bhat, R.; Hegde, A.C.Chloride bath containing ZnCl2.7H2O, FeCl2.H2O and a combination of sulphamic acid and citric acid (SA+CA) were optimized for electrodeposition of bright Zn-Fe alloy coating on the mild steel. Bath constituents and operating parameters were optimized by the Hull cell method for highest performance of the coating against corrosion. The effect of current density and temperature on deposit characteristics such as corrosion resistance, hardness, thickness, cathode current efficiency and glossiness, were studied. Potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) methods were used to assess corrosion behaviour. Surface morphology of coatings was examined using scanning electron microscopy (SEM). The Zn-Fe alloy with intense peaks corresponding to Zn (100) and Zn (101) phases, evidenced by X-ray diffraction (XRD) study, showed the highest corrosion resistance. A new and economical chloride bath for electrodeposition of bright Zn-Fe alloy coating on mild steel was proposed and discussed. © 2019 by the authors.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).