Cerium containing pH-responsive microcapsule for smart coating application: Characterization and corrosion study

In the following paper first, novel pH-sensitive melamine-formaldehyde microcapsules containing ethylene glycol with three concentrations of cerium nitrate were synthesized. Then, three different quantities of the microcapsules were introduced to the epoxy coatings and applied on the AA2024-T3 substrate to meet the increasing demands for self-healing coatings. The characteristics of microcapsules were studied by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR), and dynamic light scattering (DLS). The UV–Vis spectroscopy was accomplished to the appraise pH-triggered release of the microcapsules. The salt spray test along with electrochemical impedance spectroscopy (EIS) was conducted for studying the anti-corrosion and self-healing proficiency of microcapsule-based coatings. The UV–Vis spectroscopy outcomes showed that the synthesized microcapsules are responsive to alkaline pH and the release rate of microcapsules in the basic medium rises with increasing the pH values. Moreover, the EIS and salt spray results indicated that incorporation of 10 wt% of the microcapsules into the epoxy coating not only improved the anti-corrosion strength of the aluminum substrate compared to neat epoxy coating remarkably but also, provided active corrosion protection of the substrate through the self-healing action of cerium ions. Also, the attendance of cerium cations in the scratch surface was confirmed by field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX) map.