Synergistic π-π interaction-driven quinacridone-graphene oxide hybrids for ultra-corrosion resistant epoxy composite coatings on mild steel.

Developing environmentally benign anticorrosion coatings with high performance is essential for protecting mild steel infrastructure, yet reconciling chemical stability with long-term durability remains a major challenge. Herein, leveraging the π-π conjugation between quinacridone (QA) and graphene oxide (GO), we construct QA-functionalized GO hybrids and incorporate them into a waterborne epoxy (EP) coating to form an ordered self-assembled composite architecture. The resulting QA-GO/EP coating delivers an initial low-frequency impedance modulus as high as 4.53 × 106 Ω cm2 in 3.5 wt% NaCl solution-more than an order of magnitude higher than that of neat EP. Furthermore, electrochemical tests on scratched coatings reveal that QA-GO induces the formation of a stable passivation layer at damaged sites, effectively suppressing localized corrosion propagation. This work presents a new materials design paradigm for achieving ultra-corrosion-resistant epoxy coatings via controlled molecular-scale interactions.