Functionalized borosilicate-silica-epoxy nanocomposite superhydrophobic coating for corrosion inhibition under harsh environment

Abstract

Current work proposes a facile scheme for fabrication of robust superhydrophobic borosilicate-silica-epoxy nanocomposite coatings on steel substrate with hierarchical structures, capable of inhibiting corrosion under harsh environment. The scheme amalgamates the advantageous properties of three ingredients: acid resistant property of borosilicate glass, superhydrophobic features of functionalized silica nanoparticles and durability of epoxy resin. The various steps of synthesis include 1. ball milling of borosilicate glass to micron and submicron size (~500 nm to 1.5 μm) 2. grafting of silica nanoparticles (~20 nm, through stober method) on the borosilicate particles to form rough hierarchical structure and 3. preparation of stable dispersion of the nanoparticles in epoxy-based resin followed by coating through immersion technique. Efficacy of the scheme was established through morphological, durability and electrochemical impedance studies. The surface morphology revealed hierarchical structures of functionalized silica nanoparticles (size range 20–100 nm) grafted on micro-sized borosilicate particles, which sustained water droplets with contact angle as high as 164.5° ± 2°. Sandpaper abrasion test proved excellent durability retaining hydrophobicity up to 250 abrasion cycles. The prepared surface maintained notable interface stability under aggressive environment: 3 and 10 days under pH 1 and 13 respectively. The electrochemical study in 3.5 wt% NaCl aqueous solution showed significant decrease in corrosion current density of coated surface (0.3585 μA/cm2) compared to uncoated surface (43.918 μA/cm2) suggesting excellent corrosion resistance. The results highlight scope of using this robust coating for abrasive and harsh environment.