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

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 (theta = 105 degrees) and outstanding passive-active protection against corrosion for A36 mild steel (A36MS) in a saline solution (1 M approximately equal to 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).

Automated summary

The study presents graphene oxide bifunctionalized with NH2/NH3+, showing potential for smart nanocomposite coatings with hydrophobic properties and dual corrosion protection. The newly disclosed bifunctionalization mechanisms involve covalent functionalization of graphene oxide using microwave irradiation, leading to BFGO with NH2:NH3+ groups. The nanocomposites based on Epoxy Resin/BFGO exhibit excellent corrosion protection properties against A36 mild steel in a saline solution, significantly reducing corrosion current density and corrosion rate compared to neat Epoxy Resin coatings.