Construction of waterborne epoxy smart anti-corrosion coating based on mPDA/Ti3C2Tx nanocomposites - Synergistic barrier effect and self-repair mechanisms

MXene-based two-dimensional layered materials have significant potential for application in the field of functional coatings, but nanosheet self-aggregation phenomena lead to limited dispersion stability in polymer anti-corrosion coatings. In this study, mesoporous polydopamine spheres (mPDA) were successfully prepared using a nanoemulsion assembly strategy and loaded onto the Ti 3 C 2 Tx MXene surface by interfacial self-assembly technique. Sodium molybdate (Na 2 MoO 4 ) was further introduced into the mesoporous structure of mPDA using vacuum negative pressure impregnation to construct MXene@mPDA@Mo nanohybrid materials (MPMo) with multilevel structures. Corrosion-resistant composite protective coatings were prepared by doping MPMo nanohybrid materials into waterborne epoxy resin (WEC) matrix. The electrochemical impedance spectroscopy (EIS) test showed that the Rc of the MPMo/WEC composite coating decreased from 5.839 × 10 9 Ω·cm 2 to 7.257 × 10 8 Ω·cm 2 after 60 d of immersion in 3.5 wt% NaCl solution, which is three orders of magnitude higher than that of the pure epoxy resin. The excellent self-healing properties of the MPMo/WEC coatings were confirmed by EIS testing of the scratched areas of the coatings, accelerated corrosion testing with 700 h salt spray, SEM-EDS analysis of the scratched areas and XPS characterization of the corrosion products . In addition, the results of UV aging and thermal cycling tests have demonstrated the excellent corrosion resistance of the composite coating . In the mechanical property test, the adhesion of MPMo/WEC composite coating reached 6.59 MPa and the tensile strength reached 36.46 MPa, which were better than that of the pure epoxy coating. In summary, the present study, based on the molecular assembly strategy and supplemented by the self-repair mechanism, not only effectively inhibited the agglomeration of MXene in the waterborne epoxy matrix , but also significantly enhanced the comprehensive anticorrosive and mechanical properties of the coatings, which provided a new idea for the efficient application of MXene-based functional materials in waterborne epoxy anticorrosive coatings. • A three-stage construction strategy is used to improve the problem of MXene nanosheets being prone to self-aggregation. • Metal chelation by PDA and anodic passivation effect by MoO 4 2− provide multistage self-healing for composite coatings. • The self-healing properties of composite coatings give them excellent corrosion resistance and self-healing capabilities.