Super-Anticorrosive Materials Based on Bifunctionalized Reduced Graphene Oxide

The design of new materials with two or more functional groups must be strongly considered to achieve multifunctional coatings with outstanding properties such as active-passive protection against corrosion, low-friction, antifouling, and sensing, among others. In this sense, nanocomposites based on solvent-free epoxy resin/bifunctionalized reduced graphene oxide layers with NH₂ and NH₃⁺ groups (ER/BFRGO) with super-anticorrosive properties are for the first time reported here. The amine groups (-NH₂) act as cross-linker agents, which react with epoxy terminal groups from resin, thus closing the gap between the BFRGO layers and the polymeric matrix. Meanwhile, the ammonium ions (-NH₃⁺) are effective trapping agents of negatively charged atoms or molecules (e.g., Cl^-). This novel combination enables us to obtain nanocomposite coatings with passive-active protection against corrosion. ER/BFRGO deposited onto A36 mild steel exhibited a remarkably enhanced barrier against corrosion into a saline medium (1 M NaCl; 58.4 g/L), wherein the corrosion current density (i_corr) was diminished 6 orders of magnitude (i_corr = 5.12 × 10^-12 A/cm²), with respect to A36 mild steel coated only with ER (i_corr = 2.34 × 10^-6 A/cm²). Also, the highest polarization resistance R_p = 6.04 × 10⁷ Ω/cm² was obtained, which represents the lowest corrosion rate and corresponds to 3 orders of magnitude higher than A36 mild steel coated with ER (R_p = 1.43 × 10⁴ Ω/cm²). The strategy of bifunctionalization proposed herein to obtain bifunctionalized reduced GO with NH₂ and NH₃⁺ groups has not been disclosed in the literature before; in consequence, this work opens a new pathway toward the design of smart materials based on multifunctional nanomaterials.