Polyaniline/ZrO2 doped epoxy nanocomposite coatings with synergistic maze-passivation and hydrophobicity for marine anticorrosion and antifouling

Corrosion and biological fouling of marine engineering equipment leads to substantial annual economic losses. To address these dual challenges, this study developed a novel multifunctional epoxy composite coating by blending polyaniline (PANI) and nano-zirconia (nano-ZrO 2 ) into epoxy (designated as EP/PA/Zr), followed by in-situ hydrophobic modification using polymethyltrimethoxysilane (PMTMS). The composite coating exhibited superior performance on AISI 304 stainless steel (SS) in artificial seawater, as evaluated through surface characterization, electrochemical tests, antibacterial assays, and long-term immersion experiments. The EP/PA/Zr-2 composite coating achieved a water contact angle (WCA) of 103.4 ± 0.4° and maintained a perfect 5B adhesion strength according to ASTM D 3359-09e2 standard even after prolonged exposure. After 28 days of immersion in artificial seawater, the corrosion rate of the EP/PA/Zr-2 composite coating was only 0.043 μm·a −1 , which was over 200 times lower than that of the bare SS substrate. Particularly, the coating resistance ( R c ) and charge transfer resistance ( R ct ) remained at high levels of 4.068 × 10 6 Ω·cm 2 and 2.822 × 10 6 Ω·cm 2 , respectively, further confirming the excellent and durable protective performance. Remarkably, the EP/PA/Zr-2 composite coating exhibited no visible corrosion or peeling after an extended 180-day immersion, confirming exceptional long-term durability. Furthermore, antibacterial and antibiofouling tests revealed that the EP/PA/Zr-2 composite coating enhanced antibacterial efficiency by 48.3% against Pseudomonas aeruginosa and achieved anti-adhesion rates of 27.0% ( P. aeruginosa ), 30.5% ( Escherichia coli ), and 39.9% ( Staphylococcus aureus ) compared to the bare SS substrate. This integrated performance stemmed from the complementary roles of its components: nano-ZrO 2 particles filled matrix pores to create a tortuous physical barrier, PANI induced a redox-mediated passive layer on the metal substrate, and PMTMS modification lowered surface energy to enhance hydrophobicity and self-cleaning ability. This work provides an effective strategy for designing durable, multifunctional protective coatings with promising application potential in harsh marine environments. • An EP/PA/Zr-2 coating integrates maze-passivation and hydrophobicity for marine protection. • Achieves 103.4° WCA, 5B adhesion strength, and 200-fold lower corrosion rate (0.043 μm·a −1 ). • Maintains integrity with no corrosion/peeling after 180-day seawater immersion. • Exhibits increased antibacterial efficiency by 48.3% and reduced bacterial adhesion rate by 27.0%.