Eco-friendly design of active montmorillonite nanofillers for reinforcing the anti-corrosion property of epoxy coating

In this work, a montmorillonite (MMT)-based composite coating with long-term corrosion protection for mild steel was prepared. This composite coating incorporated the montmorillonite@polydopamine@cerium phytate (MMT@PDA@PACe) nanofiller, prepared by the easily layer-by-layer surface assembly method. Electrochemical impedance spectroscopy (EIS) and surface morphology studies showed that the prepared composite coating exhibited long-term protective performance, self-healing performance, and good integrity. In this instance, on the one hand, two-dimensional (2D) MMT could block the path of corrosive media penetrating the coating. Also, organic modification of PDA and PACe could enhance the dispersibility and compatibility of inorganic MMT fillers, thus enhancing the coating barrier effect. On the other hand, composite materials could perceive corrosion reactions and actively release corrosion inhibitors to improve corrosion resistance performance further. The coating's self-healing performance and release characteristics of corrosion inhibitors were investigated by the EIS and inductively coupled plasma optical emission spectrometer (ICP-OES) tests. Moreover, after 60 d immersion, the |Z|_{0.01 Hz} value of the 0.5 wt% MMT@PDA@PACe composite coating was over 10⁹ Ω·cm², which is 3 orders of magnitude higher than that of the bare coating. Simultaneously, the adhesive force studies were applied to the composite coatings, and the results illustrated that the coating had the highest dry conditions adhesion force with 5.43 MPa and the lowest adhesion force loss rate at 14.1 % after 30 d of immersion.