Marine waste-derived β-chitin/MXene/TA-HNT reinforced waterborne polyurethane coatings for simultaneous self-healing and corrosion protection applications

Damage repair through self-healing and corrosion-protective coatings is important for sustainable materials used in aerospace, marine, and lightweight unmanned aerial vehicle (UAV) applications. The use of β-chitin extracted from waste from squid pens was chosen as the bio-based reinforcement, while the use of tannic-acid-loaded halloysite nanotubes (TA-HNT) was selected as the corrosion-inhibiting nanocontainers, and the use of MXene as the barrier-enhancing nanofiller within a waterborne polyurethane (WPU) matrix was used in this study. Five coating formulations were fabricated and evaluated. The optimized S4 formulation (94% WPU, 3% β-chitin, 1.5% MXene, and 2.5% TA-HNT) showed Vickers microhardness of 56.2 ± 2.8 HV and flexural strength of 82.0 ± 3.6 MPa. The self-healing efficiency of S4 was measured after exposure for 48 h under ambient conditions and was determined to be 92.2 ± 2% from the shrinkage of the mean scratch width. This performance may be associated with reversible hydrogen-bond interactions between β-chitin and WPU. In the salt-spray test, S4 exhibited a rusted area of 2.8 ± 0.3% and a corrosion creep of 0.7 ± 0.1 mm. Electrochemical impedance spectroscopy (EIS) further revealed a coating resistance (Rc) of 8.5 × 10 6 Ω·cm 2 and a charge-transfer resistance (Rct) of 1.8 × 10 7 Ω·cm 2 , indicating enhanced barrier performance and corrosion protection. Potentiodynamic polarization measurements showed that the corrosion current density decreased from 7.21 μA/cm 2 for the neat WPU coating (S 1 ) to 0.34 μA/cm 2 for the optimized S 4 coating, indicating improved corrosion resistance. These findings demonstrate the potential of marine-waste-derived β-chitin/MXene/TA-HNT-reinforced WPU coatings as sustainable, multifunctional protective materials for advanced engineering applications.