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    Volume 11, Issue 2 (July 2021)

    Special Issue Paper

    Active Protection of Magnesium Alloy AZ91D Using Corrosion Inhibitor Encapsulated Halloysite Nanoclay-Based Smart Sol-Gel Coatings

    (Received 6 October 2020; accepted 3 June 2021)

    Published Online: 23 July 2021

    CODEN: MPCACD

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    Abstract

    Magnesium alloys are preferred extensively in automobile and aerospace industries, because of their very low density and high-specific strength. However, magnesium alloys are unstable in highly corrosive environments because of their extremely low standard electrode potential (−2.37 V). One of the most promising approaches to overcome this limitation is the use of eco-friendly and versatile sol-gel coatings. In the present work, corrosion-inhibition ability of various corrosion inhibitors, such as Ce3+-Zr4+, 8-hydroxyquinoline and 2-mercaptobenzothaizole, was evaluated on magnesium alloy AZ91D. For this purpose, inhibitors were loaded in as-received halloysite nanotubes (HNTs), which were then end-stoppered using polymeric microcapsules and dispersed in a hybrid silane matrix. The surface morphology of raw and inhibitor-loaded HNTs was examined with transmission electron microscopy analysis, whereas Brunauer-Emmett-Teller and scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses were carried out to verify the encapsulation of inhibitors. The coatings were developed on coupons of AZ91D by the dip-coating technique, which were then thermally cured for 1 h at 130°C. The anticorrosion ability of inhibitor-encapsulated, HNT-based sol-gel coatings on AZ91D was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization for different durations of exposure to sodium chloride solution of 0.6 M concentration. Salt spray analysis was also carried out according to ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus, to examine the anticorrosion ability of coatings for a prolonged duration of exposure, 168 h. Electrochemical measurements and salt spray analyses have revealed that Ce3+-Zr4+-loaded HNT-based coatings were found to give better anticorrosion properties during prolonged durations of exposure to extremely corrosive environments, such as a 0.6 M sodium chloride solution.

    Author Information:

    Adsul, Swapnil H.
    Centre for Sol-Gel Coatings, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, Telangana State

    Department of Chemical Engineering, National Institute of Technology, Warangal,

    Sonawane, Shirish H.
    Department of Chemical Engineering, National Institute of Technology, Warangal,

    Subasri, R.
    Centre for Sol-Gel Coatings, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, Telangana State


    Stock #: MPC20200147

    ISSN:2379-1365

    DOI: 10.1520/MPC20200147

    Author
    Title Active Protection of Magnesium Alloy AZ91D Using Corrosion Inhibitor Encapsulated Halloysite Nanoclay-Based Smart Sol-Gel Coatings
    Symposium ,
    Committee B08