Preparation of Nitrogen‐Phosphorus Co‐Doped Graphene Oxide‐Polyaniline Composite and Its Waterborne Epoxy Coating for Enhancing Corrosion Resistance Ability

ABSTRACT To further improve the corrosion protection ability of waterborne epoxy (WEP) composite coatings for metals, a novel nitrogen and phosphorus co‐doped graphene oxide‐polyaniline (NPGO‐PANI) composite material was prepared by using combined hydrothermal and in situ polymerization methods. Then, NPGO‐PANI composites were mixed with WEP to prepare NPGO‐PANI/WEP anti‐corrosion coatings on the surface of Q235 steel. Electrochemical test results indicate that the impedance module at 0.01 Hz of NPGO‐PANI/WEP coatings remains at approximately 10 ⁸ Ω cm ² after 720 h of immersion, with no significant modulus attenuation. In addition, potentiodynamic polarization curve tests demonstrate that the corrosion rate of NPGO‐PANI/WEP coatings is 5 orders of magnitude lower than that of WEP. These data exhibit significant anti‐corrosion ability of NPGO‐PANI/WEP composite coatings because of the synergistic effect of the coordination of nitrogen atoms to metal ions, the chelation of polyphosphates to metal ions, the enhanced dispersibility in WEP of NPGO‐PANI filler by facilitating the electrostatic interactions, and the accelerated passivation on the metal surface by PANI. The synergistic inhibition of NPGO and PANI effectively hinders charge and material transfer related to the corrosion reaction, thereby significantly enhancing the corrosion protection properties.