Covalently Grafted 2,6‐Diaminopyridine‐Functionalized Graphene Oxide/Polyaniline Triple Synergistic Nanofillers for Improving Long‐Term Anticorrosion Ability of Waterborne Epoxy Coatings

ABSTRACT To address the limitations of traditional waterborne epoxy (WEP) coatings under corrosive environments and enhance the long‐term anticorrosion ability of carbon steel, this study designed and synthesized a covalently grafted 2,6‐diaminopyridine (DAP)‐functionalized graphene oxide (GO)/polyaniline (PANI) triple synergistic nanofiller (DAPGO‐PANI). The chemical modification of GO was carried out using the corrosion inhibitor DAP, thereby introducing nitrogen‐containing heterocyclic active sites simultaneously. Then, PANI was uniformly grafted onto the surface of DAPGO via in situ oxidative polymerization of aniline, using DAP as a bridge. The resulting DAPGO‐PANI hybrid was embedded within the WEP matrix and fabricated into a DAPGO‐PANI/WEP composite coating with enhanced anticorrosion performance applied for protection of metallic substrates. Following 30 days of exposure to 3.5 wt% NaCl, the optimized 0.10 DAPGO‐PANI/WEP coating still maintained an impedance of 1.54 × 10 8 Ω·cm 2 , with an ultralow corrosion rate (9.98 × 10 −6 mm/year). Moreover, virtually no corrosion products were observed at the scribed region of coated Q235 steel after 30 days of salt‐spray exposure. Overall, the DAPGO‐PANI nanofiller remarkably improved the anticorrosive performance of WEP coatings through a triple synergistic mechanism: physical barrier, electrochemical passivation, and coordination interaction. This work provides a feasible strategy for developing polymer coatings applied in anticorrosion of metals.