Protection of mild steel with molecular engineered epoxy nanocomposite coatings containing corrosion inhibitor functionalized nanoparticles

Abstract

Selection of appropriate intelligent coatings to protect metallic objects from corrosion is still challenging especially when filler or dispersing materials are used for reinforcing polymer matrix. A novel siloxane corrosion inhibitor precursor was designed and chemically grafted onto the silica nanoparticles to prepare molecular engineered nanofiller (NPInh). The 1H NMR, 13C NMR, FT-IR, TGA and TEM characterization were applied to confirm the successful preparation of NPInh and the grafting amount of corrosion inhibitor precursor onto silica nanoparticles. The surface morphology, dispersion behavior of functionalized nanofiller, mechanical properties and corrosion resistance of the prepared inhibitor functionalized silica nanoparticles with epoxy composites coated on the mild steel were studied. The experimental results indicated the homogeneous dispersion of nanofiller in the epoxy nanocomposite coatings could be enhanced by silica surface modification using inhibitor precursor, and the NPInh component acted as a crucial role in improving the mechanical properties and corrosion resistance of nanocomposite coatings through the combined contribution of mechanical enhancement of nanoparticles and the shielding effect of corrosion inhibitor component. Combining with the apparently optimized strain durability, impact resistance and adhesion strength, the electrochemical measurements showed that the novel epoxy nanocomposite coatings blended with corrosion inhibitor functionalized nanoparticles (NPInh) were capable of superior corrosion resistance with decreased corrosion current (10−10 A/cm2) and a greatly improved protection efficiency (99.9%) after immersion in 3.5 wt% NaCl solution. Moreover, the salt spray durability characterization elucidated that epoxy nanocomposite coating modified with NPInh achieved higher salt spray resistances up to 1000 h. Therefore, it is anticipated that the molecular engineered nanocomposite coatings could open up a new category in the field of corrosion protection by spontaneously improving the dispersity of nanofiller and the barrier effect of coating.