Synergistic enhancement of polyaniline/hydroxylated boron nitride epoxy coatings for robust corrosion protection in a wide temperature range

Epoxy (EP) coatings are highly susceptible to performance degradation under elevated temperatures, which limits their long-term reliability in harsh industrial environments. In this study, polyaniline (PANI) was grafted onto hydroxylated hexagonal boron nitride (OH-BN) through an in situ oxidative polymerization process, forming a BN-PANI hybrid filler with a hierarchical structure. Microstructural characterizations demonstrate that PANI is uniformly deposited on the surface of OH-BN nanosheets, indicating the formation of stable interfacial interactions. Electrochemical evaluations indicate that the incorporation of BN-PANI improves the barrier performance of EP coatings over a temperature range from 303–363 K. The coating containing 2 wt% BN-PANI maintains a high charge transfer resistance (R_ct) of (1.81 ± 0.18) × 10⁴ Ω·cm² even after 168 h of continuous immersion at 363 K, which is substantially higher than that of the neat EP coating. OH-BN introduces tortuous diffusion pathways within the coating, effectively increasing the penetration distance for corrosive species, while the PANI layer contributes to interfacial passivation and retards interfacial corrosion processes. The synergistic effect of these mechanisms enhances the interfacial stability of the coating under elevated temperatures.