LDH/MOF composite-layered slippery liquid-infused porous surface for excellent corrosion resistance and self-healing of AZ31 Mg alloy

Conventional Mg-Al layered double hydroxide (LDH) monolayers offer insufficient space to accommodate the lubricants required for slippery liquid-infused porous surfaces (SLIPSs). Therefore, Mg-MOF-74 was deposited onto the as-prepared Mg-Al LDH, to construct an LDH/MOF composite-layered structure, which increased the storage capacity of lubricants and imparted AZ31 Mg alloy with enhanced anti-corrosion and self-healing performance. Notably, the as-synthesized Mg-MOF-74 featured abundant open metal sites, facilitating the loading of 8-hydroxyquinoline (8-HQ) corrosion inhibitor. Specifically, 8-HQ could be loaded both in the interlayers of Mg-Al LDH and open Mg sites of Mg-MOF-74. Due to the effective incorporation of 8-HQ and better insulation of a thicker lubricant layer, the LDH/MOF composite-layered SLIPS exhibited the best corrosion resistance with a corrosion current density of 5.13 × 10⁻¹⁰ A·cm⁻². Furthermore, its self-healing performance was assessed by scanning vibration electrode technique and subsequent electrochemical measurements. Results indicated that the artificial scratch on the composite coating was fully repaired after 24 h of immersion in 3.5 wt% NaCl, with its impedance modulus (1.75 × 10⁸ Ω·cm²) restored to the same order of magnitude as that of the non-scratched specimen. This was primarily attributed to the physical self-healing of lubricants and chemical self-healing via the “gradual release & layer-by-layer deposition” of Mg²⁺ and 8-HQ. Thus, the as-fabricated composite SLIPS coating demonstrates significant industrial application potential.