Faculty Publications
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Item Development, Characterization, Mechanical and Corrosion Behaviour Investigation of Multi-direction Forged Mg–Zn Alloy(Springer International Publishing, 2019) Anne, G.; Ramesh, S.; Kumar, G.; Sahu, S.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.In the present study, homogenized Mg−4%Zn (wt%) alloy was exposed to multi-direction forging (MDF) at 280 °C up to 5 passes successfully. Microstructural evolution, mechanical properties and corrosion behavior of the MDF-processed Mg−4%Zn alloy was investigated using different characterization techniques. Five passes of MDF (cumulative strain, ΣΔε = 3.45) led to the formation of ultrafine grain structure (grain size ~2.3 μm) with high angle grain boundaries (HAGBs) and high dislocation density. Corresponding ultimate tensile strength (UTS) and microhardness were observed to be 228 MPa and 88 Hv. Potentiodynamic polarization test results exhibited higher corrosion resistance (0.38 mm/y) in comparison with that of homogenized condition (1.33 mm/y). © 2019, The Minerals, Metals & Materials Society.Item The inhibition of corrosion of mild steel in 0.01-0.1 N HCl solutions by N-cyclohexyl-N?-phenyl thiourea (CPTU) has been studied using potentiodynamic polarization technique. Results obtained reveal that CPTU performs excellently as anodic inhibitor for mild steel in HCl solution. The inhibitor functions through adsorption following Temkins' adsorption isotherm. The influence of parameters like temperature, hydrochloric acid concentration and inhibitor concentration on the corrosion of mild steel has also been studied.(Inhibition of corrosion of mild steel in hydrochloric acid by N-cyclohexyl-N?- phenyl thiourea) Shetty, S.D.; Shetty, P.; Nayak, H.V.S.2005Item 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 Microstructure Evolution and Mechanical and Corrosion Behavior of Accumulative Roll Bonded Mg-2%Zn/Al-7075 Multilayered Composite(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.B.; Sahu, S.Multilayered composite of Mg-2%Zn/Al-7075 was developed by accumulative roll bonding (ARB) of wrought Mg-2%Zn and aluminum 7075 alloy. The Mg-2%Zn/Al-7075 multilayered composite exhibited density of 2295 kg/m3 and an average grain size of 1 and 1.3 ?m in Mg-2%Zn and Al-7075 layers, respectively. A thorough microstructural characterization was performed on the composites by scanning electron microscope, electron backscatter diffraction (EBSD), transmission electron microscope and phase analysis by x-ray diffraction. In addition, mechanical properties were evaluated by microhardness and tensile tests. Corrosion behavior of the multilayered composite was examined using electrochemical polarization test. EBSD analysis showed the presence of ultrafine grains with high-angle grain boundaries. The composite exhibited a significant improvement in ultimate tensile strength (~1.82 times) and elongation (~1.5 times) as compared with Mg-2%Zn alloy, after four-pass ARB process. © 2017, ASM International.Item Electrochemical investigation of the corrosion inhibition mechanism of Tectona grandis leaf extract for SS304 stainless steel in hydrochloric acid(Walter de Gruyter GmbH info@degruyter.com, 2017) Kadapparambil, S.; Yadav, K.; Ramachandran, M.; Noyel Victoria, N.V.The use of Tectona grandis leaf extract as a green corrosion inhibitor for stainless steel 304 (SS304) in 2 m hydrochloric acid was investigated using electrochemical techniques. Potentiodynamic polarization studies with different inhibitor concentrations showed that the inhibitor is of mixed type, which works by affecting both cathodic and anodic reactions. Adsorption analysis using the potentiodynamic polarization and electrochemical impedance spectroscopy runs result in standard free energy of adsorption values between -20 kJ mol-1 and -40 kJ mol-1, indicating a comprehensive adsorption, which is a mixture of both physisorption and chemisorptions processes. Fourier transform infrared spectroscopy studies show the appearance of new peaks and shift in peak positions at some locations with the use of an inhibitor, which indicates the interaction between the inhibitor molecules and metal surface. Contact angle analysis indicates the formation of hydrophobic film on the metal surface. © 2017 Walter de Gruyter GmbH, Berlin/Boston.Item Effects of combined multiaxial forging and rolling process on microstructure, mechanical properties and corrosion behavior of a Cu-Ti alloys(Institute of Physics Publishing helen.craven@iop.org, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.; Sahu, S.; Arya, S.Combined multiaxial forging (MAF) and rolling was performed on Cu-3% Ti (wt%) alloy at room temperature with emphasis on microstructural evolution, improvement in mechanical properties, and corrosion resistance. Microstructural changes were confirmed from various characterization techniques, and co-related with mechanical properties. TEM analysis revealed high shear band density in the 3 pass MAF + 90% rolled sample appearing due to high strain. EBSD analysis revealed transformation to low angle grain boundaries from high angle grain boundaries. Maximum microhardness and UTS reached to 340 HV and 960 MPa, respectively in the processed samples. Significant grain refinement was observed in MAF processed Cu-3%Ti alloy, and after combined MAF + rolling, higher dislocation density and refinement of shear bands were observed. In addition, potentio-dynamic polarization test was used to study the corrosion behavior of the alloy. Scanning electron microscope (SEM) was used to analyze the corroded surface morphology. © 2019 IOP Publishing Ltd.Item Influence of Multidirectional Forging on Microstructural, Mechanical, and Corrosion Behavior of Mg-Zn Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Ramesh, S.; Anne, G.; Shivananda Nayaka, H.S.; Sahu, S.; Ramesh, M.R.Multidirectional forging (MDF) was applied to Mg-6%Zn alloy up to 5 passes successfully at 280 °C. MDF-processed materials were characterized using optical microscope, scanning electron microscope, electron backscatter diffraction, transmission electron microscope, and x-ray diffraction. Obtained results showed a significant reduction in grain size (up to 3.8 ?m) having a large fraction of high-angle grain boundaries after 5 passes of MDF process. Maximum tensile strength of 230 MPa was achieved for 5-pass MDF-processed Mg-6%Zn alloy which is about ~ 2.0 times higher in comparison with that of homogenized alloy (117 MPa) and was attributed to higher dislocations density and grain refinement. Corrosion behavior of the alloy was investigated in 0.1 M NaCl solution using potentiodynamic polarization test, electrochemical impedance spectra analysis, and immersion tests. It was found that the corrosion rate of 5-pass MDF sample improved (0.34 mm/year) ~2.5 times in comparison with that of homogenized Mg-6%Zn alloy (0.86 mm/year) due to fine grain structure, which creates more grain boundaries that act as a corrosion barrier. © 2019, ASM International.Item Exploring the Corrosion Inhibition Properties of an Anionic Gemini Surfactant Based on an Ethylenediaminetetraacetic Acid Derivative on AZ31 Alloy(John Wiley and Sons Inc, 2021) Acharya, G.M.; Shetty, N.A.Novel sodium 2,2?-(7,16-dihexyl-8,15-dioxo-7,10,13,16-tetraazadocosane-10,13-diyl)diacetate was prepared by treating ethylenediaminetetraacetic acid dianhydride with N-dihexylamine. The surfactant was used as a corrosion inhibitor on AZ31 alloy. FT-IR spectroscopy, NMR spectroscopy and LC-MS techniques were used to characterize the synthesized anionic inhibitor. The theoretical studies, performed by using the DFT simulations revealed in-depth information on the frontier molecular orbitals and electronic properties of the inhibitor. Potentiodynamic polarization and electrochemical impedance spectroscopy methods were used to determine the corrosion inhibition ability of the synthesized surfactant. The adsorption of the surfactant on the surface of AZ31 Mg alloy obeyed Langmuir isotherm with predominantly physical adsorption and partial chemisorption. SEM-EDX and XPS were used to understand the surface morphologies of the corroded AZ31 alloy. The quantum chemical simulations were used to get the correlation between their structural, molecular geometry, and experimental results. © 2021 Wiley-VCH GmbHItem Exploring the potential role of quercetin in corrosion inhibition of aluminium alloy 6063 in hydrochloric acid solution by experimental and theoretical studies(Taylor and Francis Ltd., 2022) Kumari, D.; Venugopal, P.P.; Reena Kumari, P.D.; Chakraborty, D.Quercetin was evaluated as corrosion inhibitor for AA6063 in 0.5 M HCl solution by employing weight-loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX), Atomic Force Microscopy (AFM), X-Ray photoelectron spectroscopy (XPS) techniques allied to quantum chemical studies. Electrochemical results substantiate that the inhibition efficacy of quercetin increases proportionally with the concentration of the inhibitor. The effect of temperature on the corrosion behavior of the alloy was studied in the range of 30–60 °C. Potentiodynamic polarization study confirms the mixed type of inhibition by quercetin with preferential control of the cathodic reaction. The adsorption of quercetin on alloy surface was explained through the Langmuir adsorption isotherm model. ΔG°ads values and its variation with the temperature ensured spontaneous adsorption through chemisorption and the process was endothermic. Further, quantum chemical parameters calculated from Density Functional Theory (DFT) method for quercetin, proved a perfect correlation between structure and corrosion inhibition efficiency. © 2021 Informa UK Limited, trading as Taylor & Francis Group.Item Development of Composition Modulated Multilayer (NiTi) Alloy Coatings for Improved Corrosion Protection of Mild Steel(Pleiades Publishing, 2024) Harshini Sa, G.; Hegde, A.Abstract: A new class of materials known as composition modulated multilayer (CMM) alloy coatings has created an ever-increasing interest in materials research due to their improved functional properties. In this direction, an effort has been made to improve the poorer corrosion resistance performance of conventional monolayer nickel–titanium (NiTi) alloy coatings (due to inherent induced type of codeposition), their multilayer alloy coatings have been developed. CMM (NiTi) alloy coatings have been fabricated electrolytically on mild steel (MS) from a citrate bath, using the glycerol as additive. Multilayer alloy coatings of varying matrices have been developed by periodic modulation of direct current (DC), in terms of pulse height and pulse duration. Coating configurations in both composition and thickness of alternate layers were optimized for best performance of the alloy coatings against corrosion. Corrosion behaviours were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. Experimental study revealed that the corrosion rate (CR) of CMM coatings decreased successively with increase in number of layers up to certain limit, and then started increased. Experimental findings demonstrated that CMM (NiTi) alloy coating having optimal configuration, represented as (NiTi)2.0/4.0/120 is approximately five times more corrosion resistant than its monolayer counterpart, deposited from the same bath for same duration. Development of coatings in layered pattern was confirmed by scanning electron microscopy (SEM) analyses. EDX and XRD techniques confirms the composition and phase structure of alloy coatings. The corrosion mechanism responsible for delayed corrosion of multilayer coatings has been explained, and experimental results are discussed. © Pleiades Publishing, Ltd. 2024. ISSN 2070-2051, Protection of Metals and Physical Chemistry of Surfaces, 2024, Vol. 60, No. 2, pp. 178–189. Pleiades Publishing, Ltd., 2024.