Graphene oxide bifunctionalized with NH2/NH3+ and their outstanding-performance against corrosion

Abstract Graphene oxide bifunctionalized with NH2/NH3+ (BFGO) is presented here. Further, its potential application to produce smart nanocomposite coatings (Epoxy Resin-BFGO) with hydrophobic and dual corrosion protection (active-passive) is demonstrated. The underlying bifunctionalization mechanisms were disclosed for the first time, in which graphene oxide was covalently functionalized using N-isopropylidene-3-aminopropyl-triethoxysilane (ITES) by microwave irradiation. The bifunctionalization is produced when the imine is protonated (amine deprotection) under acidic conditions, leading to BFGO with NH2:NH3+ groups (atomic ratio = 43:57) confirmed by XPS. Nanocomposites based on Epoxy Resin/BFGO exhibited hydrophobic contact angles (θ = 105°) and outstanding passive-active protection against corrosion for A36 mild steel (A36MS) in a saline solution (1 M ≅ 58.4 g/L). These smart nanocomposite coatings exhibited a corrosion current density (icorr) diminished in around 5 orders of magnitude (icorr = 3.89 E−08 mA/cm2) compared to A36MS coated with neat Epoxy Resin (icorr = 2.34 E−03  mA/cm2). Furthermore, Epoxy Resin-BFGO showed a more noble corrosion potential value (Ecorr = −158 mV) and the lowest corrosion rate (CR = 4.57 E−07 mm/year).