Browsing by Author "Hegde, A.C."

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Anomalous codeposition of NiCo alloy coatings and their corrosion behaviour
(Elsevier Ltd, 2022) Raveendran, M.N.; Hegde, A.C.
Here, we report the electrodeposition NiCo alloy coatings from a new bath using the glycine, as additive. A bright and uniform coatings NiCo alloy have been developed at different current densities and their corrosion performances have been evaluated. The surface morphology, composition and phase structure of alloy coatings have been analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) techniques, respectively. The compositional information of NiCo alloy coatings revealed that the proposed bath follows anomalous type of codeposition over range of current density studied (1.0–4.0 A dm−2), by demonstrating more Wt. % of Co in the deposits, than in the bath. A constant increase in the Wt. % of Ni with current density was found, supported by XRD analyses; and it may be attributed to the depletion of more readily depositable Co+2 ions at cathode film by following the principle of codeposition of NiCo alloy. The corrosion study revealed that NiCo alloy deposited at 4.0 A dm−2, represented as (NiCo) 4.0 A dm-2 coating is the most corrosion resistant compared to all other coatings. The highest corrosion stability of (NiCo) 4.0 A dm-2 alloy attributed to its highest Ni content (38.6 wt%) and increased surface smoothness, supported by EDS and SEM study. © 2022
Composition modulated multilayer Zn-Fe alloy coatings on mild steel for better corrosion resistance
(2011) Venkatakrishna, K.; Hegde, A.C.
Composition modulated alloy (CMA) of Zn-Fe coatings were developed on mild steel galvanostatically from chloride bath containing sulphanilic acid (SA) and ascorbic acid (AA) through single bath technique (SBT). The properties of CMA coatings were found to depend on the thickness of individual layers and switching cathode current densities (SCCDs). The CMA (Zn-Fe) coating, having 120 layers, deposited at 20 and 50mAcm-2, were found to show the least corrosion rate (1.545 × 10-2mmy-1) compared to monolithic alloy (32.5 × 10-2mmy-1) of the same thickness. The improved corrosion resistance of multilayered coatings was due to the fact that the defects and failures occurring in a single layer in the deposition process is covered by the successively deposited coating layers, and hence the corrosive agent path is extended or blocked. Further, the high corrosion resistance of CMA Zn-Fe coatings was attributed to the "dielectric barrier" of the coatings, evidenced by dielectric spectroscopy and Mott-Schottky's plot. The corrosion rate was found to increase at high degree of layering, and is attributed to less relaxation time for redistribution of metal ions in diffusion layer, during plating. In other words, at higher layer thickness, the CMA coating tends to become a monolithic. CMA coatings were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). © Taylor & Francis Group, LLC.
Compositionally Modulated Multilayered Zn-Co Deposits for Better Corrosion Resistance
(Springer, 2020) Bhat, R.S.; Venkatakrishna, K.; Nayak, J.; Hegde, A.C.
Zn-Co compositionally modulated multilayer alloy (CMMA) deposits have been developed onto mild steel using single bath technique. Multilayer alloy coatings have been galvanostatically produced using square current pulses. The switched cathode current density and number of layers have been designed for improved corrosion resistance. Experimental data revealed that multilayer coating with 120 layers at 10/30 mA/cm2 demonstrated ~ 125 times higher resistance to corrosion than monolayer alloy coating of the same thickness. The improved corrosion resistance of multilayer coatings is due to small changes in the wt.% cobalt, leading to change in the phase structure of deposit in alternate layers. The defects and failures occurring in a single layer in the deposition process are covered by the alternatively deposited coating layers. Therefore, the direction of the corrosive agent is extended or blocked. Further, the better corrosion resistances afforded by Zn-Co CMMA coatings were explained through changes in electronic properties at the interface, supported by Mott-Schottky’s plot. However, the decrease of corrosion resistance at a high degree of layering is attributed to the less relaxation time for redistribution of solutes in the diffusion layer, during plating. Potentiodynamic polarization and electrochemical impedance data showed its good protection ability. The enhanced corrosion resistance of multilayered deposits is due to small change in cobalt content, leading to alter the phase structure of the alternate-layers of the deposits. The structural morphology and the topographical structure of the coating were analyzed by scanning electron microscopy and atomic force microscopy. Evaluation of the chemical composition of the alloy coatings was carried out by x-ray photoelectron spectroscopy. © 2020, ASM International.
Corrosion behavior of electrodeposited Zn-Ni, Zn-Co and Zn-Ni-Co alloys
(2011) Bhat, R.S.; Bhat, U.; Hegde, A.C.
Zn-Ni, Zn-Co and Zn-Ni-Co alloy coatings were electrodeposited galvanostatically using sulphate bath, having THC as additive. The bath composition and operating parameters have been optimized by standard Hull cell method. The effects of current density (c.d.), pH on composition, thickness, hardness of the deposit were studied. Under all conditions of deposition, the bath followed anomalous type of codeposition with preferential deposition of less noble metal. Corrosion resistances of the coatings were measured by potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) method showed that under optimal conditions, the corrosion resistance of Zn-Ni-Co alloy coatings is approximately 20 times and 18 times better than Zn-Ni and Zn-Co alloys of same thickness. The Zn-Ni-Co coating under optimal c.d. (3.0 A dm-2) was found due to its inherent high dielectric barrier, evidenced impedance signals. High partial c.d. for zinc in Zn-Ni-Co alloy system supports the possibility of a synergistic catalytic effect of Co on Fe and vice versa. X-ray diffraction study clearly indicates that improved corrosion resistance of ternary alloy is due to the change in the phase structure of the coatings, compared to binary alloys. Surface morphology and composition of the coatings were examined by using Scanning Electron Microscopy (SEM), interfaced with EDX facility, respectively. The ternary Zn-Ni-Co coating may thus replace the conventional Zn-Ni and Zn-Co coatings in a variety of applications. © 2011 by CEE.
Corrosion behavior of Zn-Co alloy coating from acid sulphate bath
(Center of Excellence in Electrochemistry, Univ. of Tehran, 2014) Bhat, R.S.; Hegde, A.C.
Optimization of sulphate bath for deposition of a smooth and uniform Zn-Co alloy over mild steel is discussed in the present work. Electrodeposition was done using Thiaminehydrochloride (THC) and citric acid (CA) as additives in combination. The bath followed anomalous codeposition with preferential deposition of Zn over noble Co. The experimental results reveal that a bright Zn-Co alloy having ~1.06 wt. %Co was showing peak performance against corrosion in compliance with other physical properties like reflectance, hardness, thickness and adhesion. The dependency of bath composition, current density, partial current density, pH and temperature on deposit properties like reflectivity, corrosion resistance were discussed. Deposition was carried out under different condition of c.d.’s and molar ratio of [Co+2]/[Zn+2]. No transition c.d.’s at which codeposition behavior changed from anomalous to normal type was observed. Cyclic polarization measurement was performed to study the nature of corrosion taking place in the corrosion cell. An electrochemical behavior of Zn-Co alloy electrodeposition in alkaline solutions was studied using cyclic voltammetry technique. The increase in the corrosion resistance of coatings attributed to the formation of n-type semiconductor film at the interface was confirmed by Mott-Schottky (M-S) plot with straight line having positive slope. The composition of deposits were determined by colorimetric method and confirmed by EDX analysis. Surface morphology of the deposits was examined using scanning electron microscopy (SEM). The phase content was examined by XRD analysis at different current densities. A stable acid sulphate bath has been proposed for bright and uniform deposit of Zn-Co over mild steel and discussed. © 2014 by CEE.
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.
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.
Development of anti-corrosive multi-layered coatings of zinc-nickel alloy
(2011) Subbaiah, Y.; Kaje, V.; Hegde, A.C.
Purpose: The purpose of this paper is to develop and optimize anti-corrosive multi-layered coatings of zinc-nickel alloy on carbon steel. Design/methodology/approach: A variety of composition-modulated multi-layer alloy (CMMA) coatings of zinc-nickel were developed on a carbon steel substrate by cyclic changes in cathode current during electrodeposition, coupled with variation of the thicknesses of the individual layers. The corrosion behavior of the coatings was studied in 5 percent NaCl solution by electrochemical methods. Cyclic cathode current densities (CCCDs) and the number of alloy layers were optimized for highest performance of the coatings against corrosion. The factors responsible for improved corrosion resistance were analyzed in terms of change in the intrinsic electrical properties of the capacitance value at the electrical double layer that was associated with micro/nanometric layering. The formation of the semi-conductive surface film, which was responsible for the improved corrosion resistance, was supported by a Mott-Schottky plot and the cyclic polarization study. The formation of multi-layered deposit and the mechanism of corrosion degradation of the coating were analyzed using scanning electron microscopy. Findings: CMMA coatings with an optimal configuration of (Zn-Ni)2.0/4.0/300 showed ~35 times better corrosion resistance compared to a monolithic (Zn-Ni)3.0 alloy coating of the same thickness. The peak performance was attributed to the change in intrinsic electrical properties of the coating and this conclusion was supported by dielectric spectroscopy. Originality/value: The paper describes the optimization of CCCD and the number of deposited layers by development of electrolytic deposition of anti-corrosive multi-layered zinc-nickel coatings from a single plating technique. © Emerald Group Publishing Limited.
Development of corrosion-resistant Ni–Mo coatings from low-concentration bath: effect of magnetoconvection
(Taylor and Francis Ltd., 2021) Gonsalves, C.N.; Hegde, A.C.
The phenomenon of magnetoconvection has been used effectively to improve the corrosion protection efficacy of Ni–Mo coatings from a low-concentration bath. Experimental studies demonstrated that magnetoelectrodeposited (MED) coatings developed under parallel (
Development of multilayer Sn-Ni alloy coating by pulsed sonoelectrolysis for enhanced corrosion protection
(Royal Society of Chemistry, 2016) Shetty, S.; Mohamed, M.J.; Bhat, D.; Hegde, A.C.
Multilayer Sn-Ni alloy coating has been developed electrochemically on mild steel using an ultrasound effect, as a tool to modulate mass transfer process at electrical double layer, during deposition. Sn-Ni coatings having alternate layers of alloys of different compositions were developed on a nano/micrometric scale by pulsing sonicator ON (tON) and OFF (tOFF), periodically. The composition modulated multilayer alloy (CMMA) Sn-Ni coatings have been deposited by inducing the ultrasound field periodically at optimal current density. Corrosion performances of ultrasound-assisted multilayer Sn-Ni alloy coatings have been evaluated by electrochemical methods. Corrosion data revealed that CMMA Sn-Ni coating, developed using pulsed ultrasonic field and having 150 layers, represented as (Sn-Ni)2/2/150, is the most corrosion resistant, compared to its monolayer alloy coatings developed by both with/without ultrasound effect. Corrosion protection efficacy of multilayer coatings was found to be decreased at high degree of layering due to diffusion of layers. Improved corrosion resistance of multilayer Sn-Ni coatings is attributed to an increase in the number of layers, or interfaces separating alloys of the same metals, but of different composition, surface morphologies and phase structures, supported by energy dispersive spectroscopy, field emission scanning electron microscopy and X-ray diffraction study, respectively. The better corrosion protection of CMMA Sn-Ni coatings, compared to monolayer counterparts, is attributed to an increase in the number of layers, hence phase boundaries between layers, and experimental results are discussed. © 2018 The Royal Society of Chemistry.
Development of nano-structured cyclic multilayer Zn-Ni alloy coatings using triangular current pulses
(2011) Bhat, R.S.; Hegde, A.C.
Cyclic multilayer alloy (CMA) deposits of Zn-Ni were developed on mild steel from sulphate bath having thiamine hydrochloride (THC) and citric acid (CA) as additives. CMA coatings were developed galvanostatically using triangular current pulses, under different conditions of cyclic cathode current density (CCCD's) and number of layers. The corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy methods, and were compared with that of monolayer Zn-Ni alloy of same thickness. At optimal configuration, CMA coating represented as, (Zn-Ni)2.0/5.0/300 was found to exhibit ?40 times better corrosion resistance compared to monolayer alloy, (Zn-Ni)3.0. Cyclic voltammetry study demonstrated that THC and CA have improved the appearance of the deposit by complexation with metal ions. The corrosion protection efficacy of CMA coatings was attributed to the difference in phase structure of the alloy in successive layers, evidenced by XRD analysis. The formation of multilayer and corrosion mechanism was analyzed by Scanning Electron Microscopy (SEM) study. © 2011 Allerton Press, Inc.
Development of nano-structured Zn-Ni multilayers and their corrosion behaviors
(2011) Yogesha, S.; Bhat, R.S.; Venkatakrishna, K.; Pavithra, G.P.; Ullal, Y.; Hegde, A.C.
Composition modulated multilayer alloy (CMMA) coatings of Zn-Ni was developed using single bath technique (SBT). CMMA coatings were developed galvanostatically using square current pulses. The cyclic cathode current densities (CCCDs) and number of layers were optimized for highest corrosion resistance. Experimental results showed that CMMA coating, developed at 2.0/5.0 A/dm2, having 300 layers is ?29 times higher corrosion resistant than monolithic alloy of same thickness. Tafel and impedance data revealed its good protection ability. The improved corrosion behavior exhibited by multilayers was explained using dielectric spectroscopy. The formation of multilayer and corrosion mechanism was analyzed using scanning electron microscopy (SEM). Copyright © Taylor & Francis Group, LLC.
Development of nanostructure multilayer Co-Ni alloy coatings for enhanced corrosion protection
(2013) Pavithra, G.P.; Hegde, A.C.
Nanostructure multilayer alloy coatings (NMAC) of Co-Ni were developed on copper in layered manner using different current pulses. NMAC of Co-Ni was deposited galvaostatically from acid sulphate bath under different combination of cyclic cathode current densities (CCCD's) and number of layers. Corrosion behaviors of coatings were evaluated in 1 M hydrochloric acid, as representative corrosion medium. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) study revealed that NMAC (Co-Ni) 2.0/4.0/6.0/60/three exhibits~160 times better corrosion resistance than monolayer coating, deposited from same bath for same time. Better corrosion protection was attributed to the increased effect of interface, arising from the exceptional thinness of the layers. As composition of alloys in successive layers were varied, consequent to the deposition current density (c.d.), the change in phase structure of the deposits were observed, confirmed by X-ray diffraction (XRD) study. Layer formation and surface after corrosion tests were examined by scanning electron microscopy (SEM) and optical profilometer, and reasons responsible for better protection were analyzed. © 2013 by CEE.
Development of Ni-W alloy coatings and their electrocatalytic activity for water splitting reaction
(Elsevier B.V., 2020) Neethu, R.M.; Hegde, A.C.
This study reports the electrodeposition of Nickel-Tungsten (Ni-W) alloy coatings and their efficiency as electrode material for water splitting applications. Ni-W alloy coatings were electrodeposited and their electrocatalytic activity towards alkaline water splitting for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH were studied. Cyclic voltammetry (CV) and chronopotentiometry (CP)techniques were used to quantify their electrocatalytic behaviors. It demonstrated the inverse dependency of electrocatalytic behaviors of coatings towards HER and OER at low and high c.d.'s, respectively. This is attributed to the change in the composition, in terms of Ni and W content of the alloy. The surface features, structural and compositional change of coatings, responsible for improved electrocatalytic activity were examined using Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDS) techniques. Experiment results revealed that alloy deposit can be used as a potential material for water splitting applications. © 2020
Effect of current density on deposit characters of Zn-Co alloy and their corrosion behaviors
(2011) Yogesha, S.; Bhat, U.; Hegde, A.C.
Electrodeposition of Zn-Co alloy onmild steel has been studied, using thiamine hydrochloride (THC) as an additive. The effect of current density on deposit characters, such as chemical composition, thickness, hardness, phase structure, and surface morphology has been investigated. The electrochemical corrosion study revealed that the coating with 1.69 wt. % Co, deposited at 3.0 A dm-2 exhibited the best corrosion stability. Scanning electron microscopy (SEM), energy depressive spectroscopy (EDX), and X-ray diffraction (XRD) analyses were used to study the surface morphology, chemical composition, and phase structure of the coatings. The results were discussed focusing the effect of THC on coating characters. Copyright © Taylor & Francis Group, LLC.
Effect of heat treatment on structure and properties of multilayer zn-ni alloy coatings
(International Association of Physical Chemists, 2013) Rao, V.R.; Hegde, A.C.; Udaya Bhat, K.
Composition modulated multilayer alloy (CMMA) coatings of Zn-Ni were electrodeposited galvanostatically on mild steel (MS) for enhanced corrosion protection using single bath technique. Successive layers of Zn-Ni alloys, having alternately different composition were obtained in nanometer scale by making the cathode current to cycle between two values, called cyclic cathode current densities (CCCD’s). The coatings configuration, in terms of compositions and thicknesses were optimized, and their corrosion performances were evaluated in 5 % NaCl by electrochemical methods. The corrosion rates (CR)’s of multilayer alloy coatings were found to decrease drastically (35 times) with increase in number of layers (only up to 300 layers), compared to monolayer alloy deposited from the same bath. Surface study was carried with SEM, while XRD was used to determine metal lattice parameters, texture and phase composition of the coatings. The effect of heat treatment on surface morphology, thickness, hardness and corrosion behaviour of multilayer Zn-Ni alloy coatings were studied. The significant structural modification due to heat treatment is not accompanied by any decrease in corrosion rate. This effect is related to the formation of a less disordered lattice for multilayer Zn-Ni alloy coatings. © 2013 by the authors; licensee IAPC, Zagreb, Croatia.
Effect of including the carbon nanotube and graphene oxide on the electrocatalytic behavior of the Ni-W alloy for the hydrogen evolution reaction
(Royal Society of Chemistry, 2017) Elias, L.; Hegde, A.C.
The present work reports the electrocatalytic activities of the composite coatings of Ni-W developed using the carbon nanotube (CNT) and graphene oxide (GO). Ni-W-CNT and Ni-W-GO coatings were developed by exploiting the advantages of the composite electrodeposition technique. The effect of CNT and GO on the induced codeposition behavior of the reluctant metal W and the relationship with their electrocatalytic efficiency was studied. The electrocatalytic alkaline water splitting efficiency for the hydrogen evolution reaction (HER) of each of the electrode materials was tested by using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Furthermore, the practical utility of each of the electrode materials was evaluated by measuring the amount of H2 gas evolved. The variation in electrocatalytic activity with composition, structure, and morphology of the coatings was examined systematically using XRD, SEM, and EDS analyses. The Ni-W-CNT and Ni-W-GO composite coatings yielded much better electrocatalytic activities for the HER than did the as-coated Ni-W alloy. The obtained results showed Ni-W-CNT composite coating as the best electrode material for alkaline HER, attributed by both increased W content and number of electroactive centres. Moreover, the number of electroactive centres was found to be affected by the homogeneous distribution of CNT in the alloy matrix. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Effect of induced magnetic field on electrocrystallization of Zn-Ni alloy and their corrosion study
(Springer New York LLC journals@springer-sbm.com, 2014) Rao, V.R.; Hegde, A.C.
Zn-Ni alloy coatings have been deposited galvanostatically on mild steel under the effect of induced magnetic field (B), using gelatin and glycerol as additives. The effect of field intensity (from 0.05 to 0.4 T) and direction (both parallel and perpendicular) on electrocrystallization process has been studied considering the magnetohydrodynamic effect. The corrosion behaviors of coatings, deposited under different conditions of B, were evaluated by electrochemical AC and DC methods. Under optimal condition of B (perpendicular), Zn-Ni coatings showed about 3 times less corrosion rate (CR) than the one developed under natural convection (B = 0 T), deposited from same bath for same duration. The significant decrease of CR was attributed to unique electrocrystallization process during deposition, favoring increased ?-Ni5Zn21 (321) and decreased ?-Ni 5Zn21 (330) phase. Progressive decrease of CR with increase of B showed that corrosion protection efficacy of the coatings bears close relation with their crystallographic orientations and surface topography, evidenced by XRD study and SEM analysis. The effect of B on thickness, microhardness, surface morphology, phase structure, and the corrosion resistance of coatings was analyzed and results were discussed. © ASM International.
Effect of limiting current density on corrosion performance of Ni–Mo, Ni–Cd and Ni–Mo–Cd alloy coatings
(Springer Science and Business Media Deutschland GmbH, 2023) Shetty, A.R.; Hegde, A.C.
In this article an attempt was made to increase the corrosion resistance of Ni–Mo alloy coatings with the addition of small quantity of CdCl2 into its bath. The limiting of limiting current density (iL) of Ni in both Ni–Mo and Ni–Cd baths due to inherent induced and normal type of codeposition has been successfully alleviated by addition of 1 g/L of CdCl2. The advent of induced and normal type of codeposition of individual binary baths has been used to optimize the Ni content of the ternary deposit for better corrosion stability. The composition vs. current density plots of all coatings have been studied, and thereby optimal iL of Ni in all baths were assessed. The content of Mo was found to be decreased with the small addition of Cd to the bath. Results revealed that (Ni–Mo–Cd)6.0 Adm−2 coating showed better corrosion resistance by reducing iL of Ni, on addition of Cd+2 ions into the bath and was explained in the light of diffusion limited deposition of Ni+2 ions. The results were supported by SEM (scanning electron microscopy), XRD (X-ray diffraction) and AFM (atomic force microscopy) study of Ni–Mo, Ni–Cd and Ni–Mo–Cd coatings at optimal current densities. © 2023, The Author(s).
Effect of Magnetic Field on Corrosion Performance of Ni–Co Alloy Coatings
(Springer Science and Business Media Deutschland GmbH, 2023) Shetty, A.R.; Hegde, A.C.
The corrosion protection efficacy of Ni–Co alloy coatings was tried to improve by magnetoelectrodeposition (MED) approach. The magnetic field of varying strength (B) was applied in perpendicular and parallel to the direction of diffusion of metal ions, simultaneously to the process of deposition. The corrosion behaviour of the deposited coatings was studied through electrochemical DC method and results revealed that Magneto-electrodeposited (MED) Ni–Co alloys coatings were found to be more corrosion resistant than their conventionally electrodeposited (ED) counterparts. Moreover, the effect of magnetic field is more pronounced in perpendicular field direction and was explained by Lorentz force. Under optimal condition, MED Ni–Co alloy coating obtained at a magnetic field intensity of B = 0.3 T (Perpendicular) was found to be less prone to corrosion than its ED alloy (B = 0 T) counterpart. The increased limiting current density (iL) of Co2+ ions in turn increases the corrosion resistant properties of MED Ni–Co alloy coatings. The effect of magnetic field on improved corrosion resistance of the deposited coatings have been investigated in terms of their changed surface morphology, composition, phase structure and surface roughness using Scanning electron microscopy (SEM), Energy dispersion spectroscopy (EDS), X-Ray diffraction (XRD) technique and Atomic Force Microscopy (AFM) respectively. © 2022, The Author(s).