Self-healing, Solvent-free Anti-corrosion Coating based on Skin-like polyurethane/carbon nanotubes Composite with Real-time Damage Monitoring

Abstract Self-healing anti-corrosion coatings are widely regarded as a promising long-term corrosion protection strategy, and it is even more significant if the coating damage can be monitored in real-time and thus repaired. Inspired by the hierarchical structure of human skin, a self-healing solvent-free polyurethane/carbon nanotubes coating (SFPUHE-HTF-CNTs) with a skin-like bilayer structure was constructed by scraping and spraying techniques. The SFPUHE-HTF-CNTs is composed of a self-healing functional layer and a corrosion protection layer. In detail, the hydrophobic solvent-free polyurethane (SFPUHE-HTF) containing disulfide bonds and fluorinated polysiloxane chain segments consists of the self-healing functional layer, and the CNTs with good electrical conductivity consist of the corrosion protection layer, which also allows real-time monitoring of coating damage. SFPUHE-HTF-CNTs can self-repair cracks when heated at 60 ℃ for 16 min or irradiated with UV light at the energy of 200 for 48 h. The results of corrosion protection experiments indicate that the coating has a low corrosion current density (8.94×10 − 9 A·cm − 2 ), a positive corrosion potential (-0.38 V) and a high impedance modulus (|Z|=4.79×10 5 Ω·cm 2 ). The impedance modulus could still reach 4.54×10 4 Ω·cm 2 after self-healing, showing excellent self-healing properties for anti-corrosion protection. Synchronously, SFPUHE-HTF-CNTs exhibits satisfying damage sensing performance, enabling real-time monitoring of fractures at different sizes. This work realized the effective combination of self-healing performance and corrosion protection and real-time damage monitoring function through bionic design, and completed the simple, green, low-cost and rapid preparation of multi-functional self-healing coating, which has the advantage of scale production.