Mille crepe cake structure-inspired fabricating parallelly-arranged TA@Ti3C2Tx composite coating for long-term corrosion resistance under alternating hydrostatic pressure

Addition of Ti3C2Tx nanosheets into epoxy matrix is crucial for improving the mechanical and anti-corrosion properties, depending on their unique structures and properties. However, randomly-arranged Ti3C2Tx nanosheets failed to meet higher corrosion protection requirements especially under alternating hydrostatic pressure (AHP) environment. Herein, inspired by the unique structure of mille crepe cake, the tannic acid (TA)-functionalized Ti3C2Tx nanosheets were distributed parallelly in the epoxy matrix using a simple blade-coating method to form layer-by-layer (LBL) coating. Particularly, epoxy matrix incorporated with TA@Ti3C2Tx exhibited a nearly perfect internal parallel arrangement structure due to shear force during blade-coating, excellent compatibility, and higher binding force. As being immersed 60 days at 1 atm and 240 h at 20 MPa AHP in 3.5 wt% NaCl solution, the worst frequency impedance values was enhanced by 1-3 orders of magnitude for the parallel alignment in comparison to the randomly-arranged TA@Ti3C2Tx composite coating. The results were mainly due to the fact that parallelly-arranged TA@Ti3C2Tx could maximize tortuosity and got the utmost out of the barrier properties of composite coating. Moreover, electrochemical characterization of defects and Molecular Dynamics (MD) simulations results proved that TA could react with Q235 steel in three ways to form ferric-tannates, which could further prevent the corrosion of steel. Prospectively, the parallelly alignment of TA@Ti3C2Tx nanosheets in epoxy would greatly increase the corrosion resistance of composite coating, especially suitable for AHP environment.