Epoxy composite coating with excellent anti-corrosion and self-healing properties based on mesoporous silica nano-containers

Anti-corrosion coating containing smart nano-containers loaded with inhibitors played an increasingly important role in extending the coating lifetime and slowing down metal corrosion. Whereas, the low loading capacity of the inhibitors in the nano-container limits its applications. In this work, mesoporous silica (SiO2) nano-materials with large pore diameter were prepared and designed as the nano-containers loaded by 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) inhibitors. The prepared nano-containers not only achieved acid-responsive release ability but also greatly increased the loading capacity of the inhibitors. The results showed that the loading capacity of the AMT inhibitors reached 36% and the release amount of them from the SiO2-based nano-containers increased as the gradually decreased pH value of the system. When the pH was 3, 5 and 7, the release amount of the AMT inhibitors was 92.3%, 73.6% and 50.2%, respectively, indicating that the strong acidic system could exacerbate the metal damage, whereas the increasing release amount of the inhibitors could effectively slow down the metal corrosion. The experiments about the release process of the inhibitors from the nano-container ensured that the epoxy composite coating doped by the above-mentioned nano-containers could exhibit self-healing function under different acidic conditions. In addition, the prepared epoxy composite coating (EP/AMT@MSN-PAA) showed an increasing Rct value with the immersion time (that varied from 3105 Ω·cm2 to 4509 Ω·cm2 when the immersion time lasted from 0 h to 48 h). Compared to the blank epoxy coating (EP), the Rct value significantly decreased from 2876 Ω·cm2 to 658 Ω·cm2 with the time, which indicated that the epoxy composite coating had wonderful anti-corrosion performance and excellent self-healing function in harsh environments.