Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
19 results
Search Results
Item Optimization of deposition conditions for development of high corrosion resistant Zn-Fe multilayer coatings(2011) Yogesha, S.; Hegde, A.C.Composition modulated multilayer alloy (CMMA) coating of Zn-Fe was developed galvanostatically on mild steel through single bath technique (SBT), using thiamine hydrochloride as additive. Electrodeposits with different coating matrices were developed, using square current pulses. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion performance of the coatings. The cyclic cathode current densities (CCCDs) and number of layers were optimized, for highest corrosion resistance. Experimental results showed that CMMA Zn-Fe coating, developed at 2.0-4.0 A/dm2, having 300 layers is ?30 times higher corrosion resistant than corresponding monolithic alloy of same thickness. The corrosion resistance increased with number of layers up to a certain number of layers; and then decreased. The better corrosion resistance was attributed to the dielectric barrier at the interface, evidenced by dielectric spectroscopy. The formation of multilayer and corrosion mechanism was analyzed using scanning electron microscopy (SEM). © 2011 Elsevier B.V. All rights reserved.Item The fabrication, characterization and electrochemical corrosion behavior of Zn-TiO2 composite coatings(2011) Punith Kumar, M.K.; Venkatesha, T.V.; Pavithra, M.K.; Nithyananda Shetty, A.Metal-nanoparticle composite coatings improve the hardness, wear resistance and corrosion resistance properties of metal coatings. In this work, TiO 2 nanoparticles were chosen as second-phase particles to generate anticorrosive Zn composite coatings. The TiO2 nanoparticles were dispersed in a Zn plating solution to co-deposit them with Zn. The Zn-TiO 2 composite coatings were then characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray diffraction methods. The presence of TiO2 particles in the composite was confirmed by SEM images and EDS spectra. The Zn-TiO2 composite coatings incorporated with different amounts of TiO2 particles were tested for corrosion performance by polarization and electrochemical impedance spectroscopy, and the dissolution behavior of the coatings that had been immersed in corrosive media for a long time was studied. Improved corrosion resistance properties of the Zn-TiO2 composite coatings were confirmed by polarization studies, fitted Nyquist plots, an increase in phase angle and a shift in the Rct characteristic peak of the Bode plot. © 2011 The Royal Swedish Academy of Sciences.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 Nanofabricated multilayer coatings of Zn-Ni alloy for better corrosion protection(2013) Rao, V.R.; Hegde, A.C.As an effort to increase the corrosion resistance of conventional monolayer Zn-Ni alloy coating, the multilayer Zn-Ni alloy coating have been done electrolytically on mild steel (MS), using gelatin and glycerol as additives. Multilayered, or more correctly composition modulated multilayer alloy (CMMA) coatings have been developed using square current pulse. Successive layers of alloys, in nanometric scale having alternately changing composition were fabricated by making the cathode current to cycle between two values, called cyclic cathode current densities (CCCD's). The coatings having different configuration, in terms of composition and thicknesses of individual layers were developed and their corrosion performances were evaluated by electrochemical methods. The corrosion rate (CR)'s were found to decrease drastically with progressive increase in number of layers (up to 300 layers), and then increased. The coating configurations have been optimized for best protection against corrosion. The CMMA Zn-Ni coating having 300 layers was found to be about 37 times more corrosion resistant than corresponding monolayer alloy, developed from same bath for same time. High protection efficacy of the coatings were attributed to alternate layers of alloys having different surface structure and composition, supported by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) study, respectively. Optimization procedure has been explained, and results are discussed. © 2013 Pleiades Publishing, Ltd.Item Electrofabrication of multilayer Fe-Ni alloy coatings for better corrosion protection(Springer Verlag service@springer.de, 2014) Ullal, Y.; Hegde, A.C.Electrofabrication of multilayer Fe-Ni alloy coatings were accomplished successfully on mild steel and their corrosion behaviors were studied. Multilayer comprised of alternatively formed 'nano-size' layers of Fe-Ni alloy of different composition have been produced from a single bath having Fe 2+and Ni2+ ions using modulated (i.e. periodic pulse control) current density (cd). The deposition conditions were optimized for both composition and thickness of individual layers for best performance of the coatings against corrosion. The deposits were analyzed using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Hardness Tester, electrochemical AC and DC methods respectively. The multi layered deposits showed better corrosion resistances compared to the monolayer Fe-Ni (CR = 3.77 mm year-1) coating deposited using DC from the same bath; the maximum corrosion resistance being shown by the coating having 300 layers, deposited at cyclic cathodic current densities of 2.0 and 4.0 A dm-2 (CR = 0.03 mm year-1). Drastic improvement in the corrosion performance of multilayer coatings were explained in the light of changed kinetics of mass transfer at cathode and increased surface area due to modulation and layering. © 2014 Springer-Verlag Berlin Heidelberg.Item 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.Item Surface design of Mg-Zn alloy temporary orthopaedic implants: Tailoring wettability and biodegradability using laser surface melting(Elsevier B.V., 2018) Manne, B.; Thiruvayapati, H.; Bontha, S.; Motagondanahalli Rangarasaiah, R.; Das, M.; Balla, V.K.Magnesium-based alloys have attracted significant attention for biomedical applications due to its biodegradability as well as density and elastic modulus which are close to those of human bone. However, the uncontrolled biodegradation and hydrogen evolution are of major concern. In this work, laser surface melting (LSM) has been carried out to tailor initial corrosion rates of Mg-2.2Zn alloy implants. Melt pool dimensions, microstructure and surface topography of the LSM samples were analysed. The wettability and in vitro degradation characteristics of untreated and treated alloy were compared. LSM resulted in much finer cellular microstructural features than as-cast alloy and the melted region depths between 65 and 115 ?m. Higher treatment depths helped to extend the corrosion protection time by suppressing the corrosion front movement. Polished LSM samples resulted in overall corrosion rates of 0.5–0.62 mm/year which was about 40%–50% reduction compared to the as-cast alloy. Accelerated biomineralisation of the surface via enhancements in the surface energy due to microstructural refinement as well as microstructural homogeneity and Zn enrichment in ?-Mg, favoured improvement of the overall corrosion performance of LSM-treated alloy. © 2018 Elsevier B.V.Item Electrochemical studies on the corrosion resistance of Zn–Ni–Co coating from acid chloride bath(Springer, 2020) Bhat, R.S.; Manjunatha, K.B.; Prasanna Shankara, R.; Venkatakrishna, K.; Hegde, A.C.Anticorrosive deposits are a valuable approach to defending against corrosion from mild steel structures/machinery equipment. The Zn–Ni–Co coating has been deposited on low carbon steel surfaces using environment friendly optimized acidic chloride bath with ZnCl2·6H2O, NiCl2·6H2O, CoCl2·6H2O, sulphanilic acid (C6H7NO3S) and gelatin (C6H8O6). The standard Hull cell technique has been adopted for the optimization of bath components and experimental conditions, for the superior corrosion resistant coating. The corrosion test with potentiodynamic polarization method was performed to investigate the role of pH on the film quality and corrosion performances of the films. Further, the effect of current densities on corrosion resistance, thickness and hardness, have been investigated. Cyclic voltammetry technique has been used to test the electrochemical properties of the Zn–Ni–Co coating in acidic solutions. The results revealed that the increase in the current density favoured the increase in Ni and Co content in the deposit, showed higher corrosion resistance and higher cathodic current efficiency. The structural and morphological characteristics of the alloy coating have been obtained through scanning electron microscopy and X-ray diffraction techniques. The atomic force microscope was used to examine the topographic structure of the coating. X-ray Photoelectron spectroscopy was used to determine the chemical composition of alloy coatings and verified by energy dispersive X-ray analysis. The results indicate that a new and low-cost chloride bath for Zn–Ni–Co coating exhibit superior corrosion resistance properties and can be implement in various industrial applications such as automobiles, machine tools etc.[Figure not available: see fulltext.]. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Effect of Potassium Sodium Tartrate on Composition and Corrosion Performance of Ni–W Alloy Coatings(Pleiades journals, 2021) Neethu Raveendran, M.; Hegde, A.C.Abstract: In this communication, the effect of potassium sodium tartrate as complexing agent on the composition, phase structure, surface morphology, and corrosion performance of electrodeposited nickel-tungsten alloy coatings is reported. The deposition conditions were optimized for the best performance of the coatings against corrosion. Ni–W coatings were developed at different current densities and their corrosion behaviour was studied. Compositional data revealed that the noble metal tungsten content of the alloy decreased with growing cathodic current densities. Characteristics responsible for the best anticorrosion performance of Ni–W alloy coatings were compared with those of a citrate bath, earlier reported by the authors and their colleagues. The experimental study in this paper demonstrated an inverse dependency of the W content of Ni–W alloy on a current density, compared to that in a citrate bath. The X-ray diffraction study revealed that anticorrosion performance is driven by the W content of the alloys, not by the current density at which they are deposited. An inverse dependency of the W content on a current density, is discussed in the light of the theory of the mass transfer controlled M-complex ions (where M = W/Ni), associated in the deposition. It is supposed that a decrease/an increase of the W content in a tartrate or a citrate bath with the current density is afforded by a lower limiting current density (iL) of the W/Ni-complex ion, depending on the stability of the M-tartrate/citrate complex formed. The experimental results were discussed with the help of different analytical techniques, like scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractometry. © 2021, Allerton Press, Inc.Item Electrodeposition of multilayer NiW alloy coating for improved anticorrosion performance(Springer, 2021) Raveendran, M.N.; Hegde, A.C.The attractiveness of electroplating linked to cathodic current density (CD) has tried to exploit here to the development of coatings of high corrosion resistance. Multilayer NiW alloy coatings of better anticorrosion performance were electrodeposited from a tartrate bath by periodic pulsing of CD between two values, during the process of deposition. The multilayer coatings of different configurations, in terms of composition and thickness of individual layers were developed by proper modulation of amplitude and duration of the square current pulse, respectively. The deposition conditions were optimized for best performance of the coatings against corrosion. Our experimental study revealed that under optimal condition, multilayer NiW coating having (NiW)1.0/3.0/120 configuration is almost six times more corrosion resistant than its monolayer coating, deposited from same bath for same duration. The reason for improved corrosion performance in multilayer NiW alloy coating was explained in the light of effect of larger interfaces affected due to layered deposition and confirmed by scanning electron microscopy analysis, energy dispersive spectroscopy and X-ray diffraction study. The mechanism of corrosion responsible for its better performance, in relation to its monolayer coating is given, and results are discussed. © 2021, Indian Academy of Sciences.