Synergistic barrier reinforcement and interfacial passivation of Q235 steel by PANI-modified Mo₂C/epoxy hybrid coatings

Metal corrosion is a constant and difficult problem that demands advanced strategies to improve the durability of structural materials in corrosive environments. Epoxy coatings are prevalent, but they may be brittle, low-temperature cure slow and degrade in the environment. These restrictions affect their long-term shielding tendency. The present study proposes a coating system for epoxy with nanoparticles of molybdenum carbide (Mo2C) to solve the above problems. Mo₂C was compounded with PANI at different weight ratios (10–40 wt%) and the synergistic effect on anti-corrosion performance was evaluated. The successful incorporation of Mo₂C into PANI matrix was confirmed with structural characterization using FTIR, XRD and XPS. The morphological analyses showed uniform dispersion of the nanoparticles, especially at 20 wt%, with minimum aggregation, integrity of the coating, and hydrophobicity up to 94.5%. The electrochemical corrosion studies analysis showed that the 20 wt% PANI@Mo₂C/EP coating had the highest corrosion inhibition efficiency up to 86.21%. The corrosion mechanism analysis confirmed the dual action of the 20 wt% PANI@Mo₂C hybrid as an electrochemical inhibitor and physical barrier to corrosion, providing a tortuous route for complex diffusion that results in long-lasting corrosion protection in a 3.5% NaCl salt solution. The novelty of the lies in the use of PANI-modified Mo₂C as a hybrid anticorrosive filler, where Mo₂C provides barrier reinforcement and PANI promotes interfacial passivation, resulting in a synergistic protective response that is distinct from conventional PANI/epoxy coatings.