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Author: search.filters.author.Amudha, A.Subject: search.filters.subject.Sodium chloride

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    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.
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    Enhanced corrosion resistance of atmospheric plasma-sprayed zirconia–GNP composite by graphene oxide nanoplatelet encapsulation
    (Springer, 2020) Amudha, A.; Hosakoppa S, N.; Holavanahalli Doraiswamy, S.
    The unique natural diffusion barrier property of graphene plays a crucial role in protecting the carbon steel substrates from corrosion, particularly using graphene oxide nanoplatelets (GNP)–zirconia (ZrO2) composites. In the present work, atmospheric plasma spraying (APS) technique has been used to coat both the spray-dried pristine ZrO2 and ZrO2–(0.5, 1.0, 1.5 and 2) wt% GNP composite on the carbon steel substrate. The retention of GNPs in the coating was confirmed using XRD, Raman spectroscopy, TEM, FE-SEM, and EDAX techniques. The corrosion properties of the coatings in 3.5 wt%NaCl electrolyte were studied using linear polarization resistance and electrochemical impedance spectroscopy technique. This reveals the enhanced charge transfer resistance, decreased corrosion current density and corrosion rate of ZrO2–GNP composite. Further, the corrosion rate of ZrO2–2 wt% GNP coating is 130 times less than the plasma-sprayed ZrO2. Compared to 0.5, 1.0 and 1.5 wt% GNP added zirconia coatings, ZrO2–2 wt% GNP displayed the highest stability up to 14 days in 3.5% NaCl electrolyte. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Mechanical and wetting properties of 25%NiCr-75%Cr2C3 cermet coated on low carbon steel using HVOF thermal spray technique
    (Elsevier B.V., 2021) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.
    The hydrophobic ceramic–metal composites with enhanced mechanical properties will have longer durability because of the embedded liquid-repellent properties, with low water and salt absorption. In this work, the 25%NiCr-75%Cr2C3 cermet powder has been coated on low carbon steel substrate, using High Velocity Oxy-fuel thermal spray technique. The SEM is employed to analyse the morphological characterization of the coating. The mechanical properties of the 25%NiCr-75%Cr2C3 coating is evaluated using the Vickers micro-indentation technique. The micro-hardness, fracture toughness and brittleness index of the coatings are obtained. Also, the wetting property of the coating in 3.5% NaCl salt solution is investigated using the contact angle measured by sessile drop method. The contact angle of the coating is observed to be hydrophobic in nature with a contact angle of 98.14?. Thus, 25%NiCr-75%Cr2C3 hydrophobic coatings helps in the improvement of brittleness, fracture toughness, and the microhardness. © 2020 Elsevier B.V.