NH ₂ -MIL 101 (Cr)-Assisted Smart Composite Endows Epoxy Coating with Passive and Active Corrosion Protection: Enhanced Interfacial Strength and Self-healing Properties

Metal-organic framework materials with large specific surface areas are ideal choices for storing corrosion inhibitors in organic coatings. Existing reports focus on materials such as ZIF-8 and ZIF-67, which release corrosion inhibitors by disintegrating themselves upon external stimuli. This release mechanism may lead to the formation of holes within the coating, providing channels for penetration into corrosive media. In this study, NH₂-MIL 101 (Cr), which is stable under acidic/alkaline conditions, was grown on Ti₃C₂Tx surface via a hydrothermal method. Its porous structure was utilized to load environmentally friendly MoO₄^2- corrosion inhibitors, and a stimulus-responsive TEOS shell was wrapped as a valve to control the release of the corrosion inhibitors. The synthesis of the Ti₃C₂Tx-MIL 101-MoO₄^2--TEOS (TMIT) composite material was verified by FT-IR spectroscopy and XPS, respectively. The TMIT-epoxy (TMITP) composite coating was prepared through a solid-liquid mixing method. The surface-active groups of NH₂-MIL 101 (Cr) (-NH₂) enhanced the interfacial strength with the resin and the crosslinking density, significantly increasing the tensile strength and adhesion strength of the composite coating. Due to the improved interfacial strength, the low-frequency impedance value remained at 4.14 × 10⁸ Ω cm² after 6 cycles of accelerated cyclic electrochemical tests (-4.0 V, 30 min), which greatly shortening the evaluation period of the coating performance. Additionally, the stimulus-responsive release mechanism of the TMIT filler endowed the coating with self-healing effects, achieving corrosion inhibition in damaged areas. Notably, the acid/alkali stability of NH₂-MIL 101 (Cr) ensured that few holes would form within the coating after the release of corrosion inhibitors, preventing the penetration of corrosive media. This study utilized the pores of NH₂-MIL 101 (Cr) to load corrosion inhibitors and prepare self-healing composite coatings, achieving intelligent release and enhancing the corrosion resistance of coatings, thus broadening the application strategy of MOF materials in corrosion protection coatings.