APTES-grafted Hal and LDH-8HQ hybrid fillers achieve dual corrosion protection and self-healing properties in epoxy coatings

To overcome the limitations of traditional corrosion-resistant coatings, which rely solely on passive protection and exhibit poor durability, this study innovatively prepared a multifunctional hybrid filler, halloysite@layered double hydroxide loaded with 8-hydroxyquinoline and functionalized with 3-aminopropyltriethoxysilane (Hal@LDH-8HQ@APTES, HLQA). Specifically, calcined halloysite (Hal) was used as a template to in situ grow layered double hydroxide (LDH) loaded with 8-hydroxyquinoline (8-HQ) corrosion inhibitor, forming the Hal@LDH-8HQ (HLQ) hybrid. Subsequently, 3-aminopropyl triethoxysilane (APTES) was used for surface modification to enhance its interface compatibility with the polymer matrix. The resulting composite coating achieves a dual synergistic protective mechanism: (1) passive protection through physical shielding and prolonging the diffusion path of corrosive media; (2) active protection and self-healing functionality based on the anion exchange properties of LDH, simultaneously achieving chloride ion capture and controlled release of the 8-HQ corrosion inhibitor. Electrochemical impedance spectroscopy (EIS) test results indicate that the HLQA/EP composite coating exhibits outstanding long-term corrosion resistance. After immersion in a 3.5 wt% NaCl solution for 45 days, its low-frequency impedance modulus (|Z| 0.01 Hz ) remains as high as 10 9  Ω·cm 2 . Most importantly, for artificially damaged coatings, after only 12 h of immersion in a 3.5 wt% NaCl solution, the low-frequency impedance values in the damaged areas showed a significant upward trend, strongly validating the self-healing capability of the coating. This study not only significantly enhances the comprehensive protective performance of the coating but also achieves significant progress in realizing an integrated synergistic mechanism of “passive-active-self-healing” for the coating.