Preparation of Smart Self-Healing Coatings on Zinc Surfaces Using Halloysite Nanotubes Loaded with Corrosion Inhibitors.

This work presents the development of a novel nanotube (S12HNTS-T-P) that is coated with polyethylenimine (PEI) and internally loaded with a corrosion inhibitor (thiourea) utilizing vacuum negative pressure and electrostatic adsorption methods. A smart self-healing coating with self-repairing properties was fabricated on the basis of S12HNTS-T-P. Bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69), a widely used organosilane coupling agent, provides stability and corrosion resistance. The integration of S12HNTS-T-P into Si69 significantly enhances the coating's corrosion resistance and self-healing capabilities. To further evaluate the performance of the smart self-healing coating, a control group comprising Si69 coatings without S12HNTS-T-P was established. Electrochemical tests revealed that the coating with 3 wt % S12HNTS-T-P exhibited markedly superior corrosion resistance compared to those with 0, 1, and 5 wt % S12HNTS-T-P. In comparison to the control group, the coating with 3 wt % S12HNTS-T-P demonstrated a 99.4% increase in corrosion inhibition efficiency after 72 h of immersion in a 3.5 wt % NaCl solution. Scanning electron microscopy (SEM) and immersion tests further corroborated that the smart self-healing coating exhibited self-repairing behavior when subjected to external scratching stimuli. Simulation results indicated that thiourea released from the nanotubes can adsorb and form a protective film at the scratch sites, effectively repairing the coating's defects. The exceptional corrosion resistance and high healing rates of the smart self-healing coating suggest that S12HNTS-T-P plays a pivotal role in enhancing the corrosion protection of zinc.