Yolk–shell structured carbon hollow spheres (CHS)/metal-organic framework nanoparticles-holding epoxy composite inheriting smart anti-corrosion feature

This study represents the synthesis of carbon hollow spheres (CHSs) to encapsulate Zeolite Imidazole Frameworks (ZIF-8) inside and outside the CHS (ZCHS-II), and once inside the CHSs' structure (ZCHS-I) to control ZIF-8′s release properties and its influence on mild steel substrate's anti-corrosion characteristics. Nanoparticles were characterized by FE-SEM/EDX-mapping, XRD, FT-IR, HR-TEM, Raman (50–3500 cm−1), and XPS. ZIF-8 nanoparticles were successfully decorated both inside and outside the CHSs' structure according to BET and HR-TEM results. Additionally, ZCHS-II exhibited better control of Zn ions release compared to ZIF-8 and ZCHS-I nanoparticles. It was found that the ZCHS-II nanocomposite considerably enhanced the steel substrate's corrosion resistance. After 72 h of contact in NaCl media, |Z|f = 0.01 for the scratched ZCHS-II/EP (79,432 Ω.cm2) was higher than other nanocomposites and the EP coating. Moreover, ZCHS-II demonstrated excellent barrier properties during 50 days of immersion in NaCl media (log |Z|f = 0.01 > 10 Ω.cm2) and superior pull-off strength in wet conditions (2.92 MPa).