Structure and performance insights in carbon dots-functionalized MXene-epoxy ultrathin anticorrosion coatings

MXene nanosheets have showed potential application in metal protection fields due to their large specific surface area and superior mechanical properties. However, MXene for anticorrosion is still underdeveloped, and some associated matters involving susceptibility to oxidation as well as corrosion-promotion activity derived from high conductivity need to be solved. Herein, we use carbon dot (CD) to functionalize Ti3C2Tx MXene nanosheets via Ti-O-C bonding to obtain CD-Ti3C2Tx hybrids, which significantly improves the chemical stability of MXene in water. Then a flow-induced approach is introduced to construct CD-Ti3C2Tx reinforced epoxy (EP) composite coatings, in which CD-Ti3C2Tx is self-aligned to form an oriented layered structure. The unique structure endows the EP coatings with outstanding anticorrosion performance, and more than 4 orders improvement in impedance modulus at an ultrathin thickness of ∼ 25 μm, and 2 orders much higher than random-dispersed composites with the same fillers content. Besides, the CD also provides additional passivation effect to efficiently suppress crack and local damage propagation. More importantly, the parallel arrangement CD-Ti3C2Tx platelets can inhibit the corrosion-promotion activity by eliminating connections of MXene/MXene and MXene/metal in vertical direction, which will further improve the stability and durability of coatings. This work provides a novel strategy to realize chemically stable MXene and inhibit the corrosion-promotion activity of MXene-based coatings, which possess a combination of anticorrosion performance and passivation effect that are suitable for heavy-anticorrosion applications in harsh sea environment.