Corrosion Protection Mechanism Of Ti₃C₂T_x Modified Epoxy Composite Coating In Deep-sea Environment

With the country’s exploration and development of deep-sea resources and the proposal of the strategic goal of"going to deep-sea oceans",our country’s marine construction process has moved from near-shallow sea to deep-sea.Among the many technical problems of deep-sea engineering,the rapid corrosion and failure of metal materials under the deep-sea environment are the key scientific problems restricting the stability and reliability of equipment.Ti₃C₂T_x MXene two-dimensional nanomaterial is a new kind of nanomaterial,which has typical lamellar structure.On the one hand,it has excellent mechanical properties.On the other hand,Ti₃C₂T_xwith the lamellar structure,which is arranged.It can form a“labyrinth effect”in the coating,which can effectively inhibit the infiltration and diffusion of corrosive species.In this work,aiming at the corrosion failure problem of protective coatings on the surface of marine equipment,the microstructure and morphology design,the multi-interface optimization and analysis of long-term Ti₃C₂T_x two-dimensional nanosheets modified polymer composite coatings under the deep-sea environment are studied.The main research contents and results are as follows:（1）To enhance the interfacial compatibility between epoxy resin and nanofillers,nanocellulose-modified Ti₃C₂T_x nanofillers with topological structure were designed and synthesized.The anti-corrosion behavior of the composite coating under normal pressure and alternating high pressure（AHP）was investigated.The in situ deep-sea high-pressure electrochemical data showed that the low-frequency impedance modulus of the composite coating was an order of magnitude higher than that of the pure coating after immersion in AHP environment with 15 MPa for 240 h.Meanwhile,the adhesion strength of the composite coating was 132%higher than that of pure epoxy coating.This was attributed to the topological structure of the nanofillers,which could promote the interface compatibility and dispersion between Ti₃C₂T_x and the epoxy,thus improving the corrosion protection performance of the coating.（2）In order to reduce the zinc content of the zinc-rich coating and improve the cathodic protection period of the coating,polypyrrole（PPy）was in-situ modified on the surface of Ti₃C₂T_x by hydrothermal method.The corrosion performance of composite zinc rich coatings with different zinc contents under normal pressure and high pressure was systematically studied.Under a simulated high pressure environment of 20 MPa,the cathodic protection period of 60 ZRC with nanofillers was twice higher than that of pure 60 ZRC.This was attributed to the excellent electrical conductivity of PPy/Ti₃C₂T_x,which could effectively connect isolated zinc particles inside the coating to form a three-dimensional conductive network,greatly enhanced the cathodic protection period of the coating and the utilization rate of zinc powder.Thus,PPy/Ti₃C₂T_x-60ZRC showed excellent anti-corrosion performance.（3）To endow the coating with self-healing properties,Ti₃C₂T_x nanosheets were grafted with DL-phenylalanine.The corrosion and self-healing properties of composite coatings were investigated.After immersion in the simulated 30 MPa environment for240 h,the composite coating showed excellent corrosion resistance,and its low-frequency impedance modulus was as high as 10⁷Ω·cm²,which was an order of magnitude higher than that of the pure epoxy coating;the adhesion strength was increased by 119%compared with that of pure epoxy coating.（4）In order to improve the mechanical properties of the coatings,carbon fibers were used in synergy with Ti₃C₂T_x nanosheets,and the mechanical and electrochemical properties of the CF/Ti₃C₂T_x-EP composite coatings were investigated.The results showed that the composite coating exhibited excellent corrosion protection,which was immersed in a simulated 30 MPa environment for 240 h.The CF modification effectively improved the strength of the coating system,and at the same time,Ti₃C₂T_xplayed an excellent physical shielding effect,and the synergy endowed the composite coating with excellent deep-sea high pressure corrosion resistance.