Faculty Publications
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Item The inhibiting effect of N - cyclohexyl - N?- phcnyl thiourea (CPTU) and N-naphthyl-N?- phenyl thiourea (NPTU) on the corrosion of mild steel in aqueous solution of 0.1 N H2SO4 have been demonstrated using potentiodynamic polarization technique. The polarization data have shown that these compounds act as efficient anodic inhibitors for mild steel. Adsorption of these compounds on the mild steel surface was found to obey Temkin's adsorption isotherm. Good inhibition efficiency (IE) was evidenced in both the compounds and it was found to vary with concentration of the inhibitors. The kinetic parameters of adsorption obtained reveal spontaneous adsorption and a strong interaction of the compounds on the mild steel surface. © 2006 SAEST.(Inhibition of mild steel corrosion in sulphuric acid solution) Divakara Shetty, S.; Shetty, P.; Sudhaker Nayak, H.V.2006Item Trifluoromethyl-quinolin-yl-thio-propanohydrazide as an effective inhibitor of mild steel corrosion in HCl solution(2006) Ramesh Saliyan, V.; Vasudeva Adhikari, A.V.3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide(TFQTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in 1 M HCl and 2 M HCl solution using different techniques: potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that TFQTPH is an excellent inhibitor for mild steel in acid medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. In the temperature range 20° to 60° C, the TFQTPH adsorption follows Langmuir isotherm model. The protection efficiency increased with increasing inhibitor concentration (10 to 500 ppm), even at higher temperature also, it recorded good inhibition efficiency. © 2006 SAEST.Item The corrosion inhibition of maraging steel under weld aged condition by 1(2E)-1-(4-Aminophenyl)-3-(2-Thienyl)prop-2-en-1-one in 1.5 M hydrochloric acid medium(Springer New York LLC barbara.b.bertram@gsk.com, 2012) Sanatkumar, B.S.; Nayak, J.; Nityananda Shetty, A.N.The influence of 1(2E)-1-(4-Aminophenyl)- 3-(2-Thienyl)prop-2-en-1-one (ATPI) on the corrosion behavior of weld aged maraging steel in 1.5 M hydrochloric acid was studied by potentiodynamic polarization method and AC impedance (EIS) technique at different temperatures. The results showed that the inhibition efficiency of ATPI increased with the increase in the concentration of inhibitor and decreased with the increase in temperature. ATPI acts as a mixed type inhibitor without affecting the mechanism of the hydrogen evolution reaction or iron dissolution. The adsorption of ATPI on a weld aged maraging steel surface obeys the Langmuir adsorption isotherm equation. Both activation and thermodynamic parameters were calculated and discussed. ATPI inhibits the corrosion through both physisorption and chemisorption on the alloy surface. The surface morphology of the weld aged maraging steel specimens in the presence and the absence of the inhibitors was studied by the respective SEM images. © ACA and OCCA 2011.Item High temperature corrosion behaviour of HVOF sprayed WC-CrC-Ni coatings(Inderscience Publishers, 2016) Somasundaram, B.; Kadoli, R.; Ramesh, M.R.; RAMESH, C.S.The present work aims to study the hot corrosion resistance of high velocity oxy-fuel (HVOF) sprayed WC-CrC-Ni coating developed on three types of boiler tube materials such as SA213-T22, MDN-310 and Superfer 800 H steels. Hot corrosion studies were conducted in a molten salt environment of Na2SO4-60%V2O5 at 700°C and thermogravimetric analysis was used to establish kinetics of corrosion. Corrosion kinetics of coated steels followed nearly parabolic behaviour and showed a lower corrosion rate in comparison to uncoated alloys. It is concluded that corrosion is restricted to the external surface of the coating and the formation of thick scale composed of oxides of Cr, Ni and their spinel oxides, acts as a diffusion barrier to the transportation of corrosive species into the coating. The carbides of tungsten and chromium uphold the strength of the coating. © © 2016 Inderscience Enterprises Ltd.Item Corrosion resistance and in-vitro bioactivity of BaO containing Na2O-CaO-P2O5 phosphate glass-ceramic coating prepared on 316 L, duplex stainless steel 2205 and Ti6Al4V(Institute of Physics Publishing helen.craven@iop.org, 2018) Edathazhe, A.B.; Shashikala, H.D.The phosphate glass with composition 11Na2O-15BaO-29CaO-45P2O5 was coated on biomedical implant materials such as stainless steel 316 L, duplex stainless steel (DSS) 2205 and Ti6Al4V alloy by thermal enamelling method. The structural properties and composition of glass coated substrates were studied by x-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive x-ray spectroscopy (EDS) analysis. The coatings were partially crystalline in nature with porous structure and pore size varied from micro to nanometer range. The polarization curve was obtained for uncoated and coated substrates from electrochemical corrosion test which was conducted at 37 °C in Hank's balanced salt solution (HBSS). The corrosion resistance of 316 L substrate increased after coating, whereas it decreased in case of DSS 2205 and Ti6Al4V. The XRD and SEM/EDS studies indicated the bioactive hydroxyapatite (HAp) layer formation on all the coated surfaces after electrochemical corrosion test, which improved the corrosion resistance. The observed electrochemical corrosion behavior can be explained based on protective HAp layer formation, composition and diffusion of ions on glass coated surfaces. The in-vitro bioactivity test was carried out at 37 °C in HBS solution for 14 days under static conditions for uncoated and coated substrates. pH and ion release rate measurements from the coated samples were conducted to substantiate the electrochemical corrosion test. The lower ion release rates of Na+ and Ca2+ from coated 316 L supported its higher electrochemical corrosion resistance among coated samples. Among the uncoated substrates, DSS showed higher electrochemical corrosion resistance. Amorphous calcium-phosphate (ACP) layer formation on all the coated substrates after in-vitro bioactivity test was confirmed by XRD, SEM/EDS and ion release measurements. The present work is a comparative study of corrosion resistance and bioactivity of glass coated and uncoated biomedical implants such as 316 L, DSS and Ti6Al4V. © 2018 IOP Publishing Ltd.Item On the corrosion resistance of some selective laser melted alloys(Elsevier B.V., 2018) Suryawanshi, J.; Baskaran, T.; Prakash, O.; Arya, S.; Ramamurty, U.The electrochemical corrosion resistances of selective laser melted (SLM) 316 L austenitic stainless steel (SS), 18(Ni) 300-grade maraging steel (MS), and Al-12 wt.% Si (AS) alloy in a 0.1 M NaCl solution at room temperature were evaluated. The effects of laser scanning strategy (single melt vs. checker board styles), post-SLM heat treatment, and corroding surface orientation (with respect to the scan and build directions) on the corrosion behavior were examined. In all cases, results were compared with those obtained on samples with the same compositions, but manufactured using conventional means. The experimental results show that, for the particular set of experimental conditions employed in this study, SLM in general improves the corrosion resistances of Al-12 wt.% Si and stainless steel alloys and degrades the corrosion resistance of the maraging steel, in comparison to the respective corrosion resistances of their conventionally manufactured counterparts. These results are discussed in terms of microstructural refinement and porosity that are common to the SLM alloys. © 2018 Acta Materialia Inc.Item Crosslinked polymer doped binary coatings for corrosion protection(Elsevier B.V., 2018) Kaur, H.; Sharma, J.; Jindal, D.; Arya, R.K.; Ahuja, S.K.; Arya, S.Solvent-based polymeric multilayer coatings prepared by ex-situ addition of crosslinked poly(styrene-co-divinyl benzene) in poly(styrene)-ethylbenzene solution were examined for corrosion protection of mild steel in a simulated water environment equivalent to sea water and acid rain. Electrochemical impedance spectroscopy (EIS) technique was used to determine the corrosion resistance behavior of the prepared polymeric coatings in 3.5 wt % of NaCl aqueous solution. EIS analysis suggested that the sample solution prepared by adding 1% crosslinked polymer in poly(styrene)-ethylbenzene solution, has better corrosion resistance as compared to the sample solutions prepared by adding 3% and 2% of crosslinked polymer in poly(styrene)-ethylbenzene solutions. Scanning electron microscopy (SEM) revealed that substrate coated with polymeric solution prepared by adding 1% of crosslinked polymer in poly(styrene)-ethyl benzene solution showed less corrosion as compared to the substrates coated with sample solutions prepared by adding 3% and 2% of crosslinked polymer in poly(styrene)-ethylbenzene solutions. © 2018 Elsevier B.V.Item Corrosion protection of low-cost carbon steel with SS-309Mo and Inconel-625 bimetallic weld overlay(Institute of Physics Publishing helen.craven@iop.org, 2019) Mudha, A.A.; Shashikala, H.D.; Nagaraja, H.S.The dissimilar weld overlay coatings of components can lead to corrosion. In the present work, two different weld overlay layers (SS-309Mo and Inconel-625) are deposited on IS2062 grade B carbon steel, in order to avoid distortions and improve corrosion resistance. The microstructural investigations revealed that the intermediate layer SS-309Mo on carbon steel prevents the dilution by aiding crack-free weld overlay of Inconel-625 on the top. The corrosion behaviour of the coatings is studied using Linear Polarization Resistance and the Electrochemical Impedance Spectroscopy. The corrosion rate of the coatings decreased by two orders of magnitude compared to that of low carbon steel substrate. The corrosion rate of the deposited Inconel-625 along with intermediate SS-309Mo is 1.16×10-3 and is comparable to that of bare Inconel-625 (1.12×10-3 mmpy). Further, the immersion tests for 14 days show that, the depositions are stable with the formation of the passive film. ©2019 IOP Publishing Ltd.Item Hot corrosion behaviour of HVOF sprayed Ni3Ti and Ni3Ti + (Cr3C2 + 20NiCr) coatings in presence of Na2SO4-40%V2O5 at 650 °c(IOP Publishing Ltd custserv@iop.org, 2019) Reddy, N.C.; Koppad, P.G.; Reddappa, H.N.; Ramesh, M.R.; Babu, E.R.; Varol, T.Ni3Ti and Ni3Ti + (Cr3C2 + 20NiCr) coatings were deposited on gas turbine based ASTM B265 titanium (Ti-15) and AISI 420 stainless steel (MDN-420) substrate materials using HVOF technique. Thermocyclic hot corrosion tests were carried out at 650 °C in molten salt environment of Na2SO4-40%V2O5 for about 50 cycles. Thermogravimetric analysis was carried out to study the hot corrosion kinetics of uncoated and coated titanium and stainless steel substrates. The weight gain per unit area showed that the coated substrate materials displayed better resistance to hot corrosion when compared with that of uncoated substrate materials. The surface morphology of uncoated and coated substrate materials were analysed using scanning electron microscopy and elemental analysis. The formation of different types of oxides and compounds were analysed using x-ray diffraction. The uncoated substrates surface showed microspalling at several regions while coated substrates surface were composed of protective oxide layers. The presence of ternary NiCr2O4 protective oxides on the surface of Ni3Ti + (Cr3C2 + 20NiCr) coated substrates leads to reduction in the diffusion of corrosive species inside the coating. © 2019 IOP Publishing Ltd.Item Effect of graphene oxide loading on plasma sprayed alumina-graphene oxide composites for improved anticorrosive and hydrophobic surface(IOP Publishing Ltd custserv@iop.org, 2019) Amudha, A.; Shashikala, H.D.; Asiq Rahman, O.S.; Keshri, A.K.; Nagaraja, H.S.Alumina is a widely used anticorrosive coating material for protection of metal surfaces. The graphene oxide (GO)-Alumina composite coatings can enhance the anticorrosion property of carbon steel surfaces used in an industrial scale. In the present work, the spray dried graphene oxide nanoplatelets of 0, 0.5, 1, 1.5 and 2 wt% reinforced alumina (?-Al2O3) were deposited on the low carbon steel substrate by Atmospheric Plasma Spray (APS) technique. The GO-Alumina nanocomposite coatings are characterised using XRD, FE-SEM, HR-TEM and Raman Spectroscopy. The electrochemical corrosion behaviour of the coatings on carbon steel has been examined using three electrode electrochemical method in 3.5 wt% NaCl electrolyte. A remarkable improvement in the corrosion resistance (with a corrosion current density of 0.01 nAcm-2) of about six orders with respect to pristine alumina was observed. The wettability tests revealed that, with 1.5 and 2 wt% graphene oxide nanoplatelets addition, the surface coating turned out to be hydrophobic with contact angle of 127°, from hydrophilic with contact angle 36°, which complements the anticorrosion results. The in situ reduction of GO to r-GO by APS deposition and bridging of alumina splats by the GO sheets accounts for observing the superior performance of the composite coatings. © 2019 IOP Publishing Ltd.