Anti-corrosion, self-healing and environmental-friendly Ti 3 C 2 T x /MgAl-LDH @epoxy composite organic coating for Mg alloy protection

In order to obtain compact epoxy-based organic coatings with superior corrosion resistance and self-healing performance, a novel Ti 3 C 2 T x /LDH-epoxy hybrid coating was prepared on AZ31 magnesium alloy in this work. The layered double hydroxide (LDH) adopted here is MgAl-LDH intercalated by the cysteine acid (Cys), an environmentally friendly organic acid anions, as corrosion inhibitors, and the MXene (Ti 3 C 2 T x )/MgAl-LDH (TML) heterostructure nanosheets were grown by a facile in situ assembled method. The morphology, composition, structure and the corrosion protection of the Ti 3 C 2 T x /MgAl-LDH-epoxy (EP-TML) composite coatings were systematically investigated and compared with the other three epoxy-based coatings: bare waterborne epoxy resin (EP), Ti 3 C 2 T x pigmented in EP (EP-T), MgAl-LDH in EP (EP-ML). It is found that the TML heterostructure has good dispersion and compatibility with the epoxy resin. The corrosion current density and the impedance value at low frequency (|Z| 0.01 Hz ) of the EP-TML composite coating are 1.4 × 10 –9 A/cm 2 and 1.66 × 10 7 Ω cm 2 , which is 4 orders of magnitude lower than that of the uncoated Mg substrate and 1–2 orders of magnitude higher than that of EP (8.7 × 10 5 Ω cm 2 ), respectively, indicating its excellent corrosion resistance. And the self-healing efficiency of EP-TML composite coating is found to be higher as 56.17% after 6 days immersion in a corrosive environment. The significant improvement of the anti-corrosion and self-healing performance of the EP-TML composite coating are mainly ascribed to the synergistic effect of "barrier effect" of TML and the corrosion inhibition effect of the cysteine acid encapsulated in MgAl-LDH. This work provides some valuable insights to widen the functional application of Ti 3 C 2 T x and the design of highly corrosion-resistant and self-healing organic coatings for Mg alloys. Graphical abstract