A smart anticorrosion self-healing waterborne siloxane-type polyurethane composite coating based on modified montmorillonite nanosheets and halloysite nanotubes loaded with 8-hydroxyquinoline

Waterborne polyurethane (WPU) coatings exhibit poor water resistance and are highly permeable to corrosive media. Consequently, they may inevitably sustain damage during prolonged use, which significantly compromises their corrosion resistance. In this study, we synthesized a self-healing waterborne siloxane-modified polyurethane (WPU-Si). To develop a PU composite coating exhibiting both exceptional hydrophobicity and corrosion resistance, modified montmorillonite nanosheets and halloysite nanotubes encapsulated with 8-hydroxyquinoline were prepared. Compared to pristine WPU, WPU-Si demonstrated remarkable mechanical property enhancements, with tensile strength increasing by 293% (from 4.6 MPa to 18.1 MPa) and elongation at break enhancing by 44.5% (from 445% to 643%).The water contact angles increased from 71.04° (WPU) to 82.39° (WPU-Si), indicating enhanced hydrophobicity. All coatings demonstrated complete self-healing (100% recovery efficiency) following 12-h thermal treatment at 50 °C. The MMT-HNT/WPU-Si coating showed outstanding corrosion resistance, with 97.35% protection efficiency, due to the shielding effect of the modified montmorillonite sheets and the smart active protection provided by the release of 8-hydroxyquinoline from halloysite nanotubes. The charge transfer resistance was 3.25 × 10 7 Ω cm 2 after 30-min in 3.5 wt% NaCl solution, maintaining 6.92 × 10 5 Ω cm 2 after 30 days. This work provides constructive guidance for creating a low-cost self-healing smart PU composite coating with long-term corrosion resistance.