Three Birds with One Stone: Zif-8@G-C3n4 Nanosheets Simultaneously Enhance the Passive Protection, Active Protection and Uv Aging Resistance of Epoxy Coatings

Abstract

Addressing the challenge of the epoxy coating's limited ability to mitigate electrochemical reactions following metal corrosion, as well as its susceptibility to degradation and aging under ultraviolet irradiation. A room-temperature synthesis method is used to load ZIF-8 particles onto the surface of g-C3N4 nanosheets, forming ZIF-8@g-C3N4 smart nanoparticles (ZCN). These nanoparticles exhibit an acidic pH response, releasing Zn2+ cations and imidazole molecules, achieving an 87.2% corrosion inhibition efficiency on carbon steel within 5 hours. ZCN modified the epoxy coating (ZCN/EP), and the coating retains a high Log |Z|0.01 Hz value even after a 40-day immersion in a 3.5 wt% NaCl solution. Furthermore, ZIF-8 responds to pH changes from localized corrosion when the coating is damaged, releasing inhibitors and forming zinc oxide/zinc hydroxide and Fe-Im chelate to further impede corrosion progression. In exploring the anti-UV mechanism, the UV absorption of g-C3N4 and the UV reflection/scattering ability of ZIF-8 are examined using a photometric system. Their synergistic action provides ZCN/EP coatings with exceptional UV resistance, maintaining exceptional anti-corrosion after 300 hours of UV exposure. Additionally, its water absorption, surface characteristics, and thermal-mechanical performance remain unaffected by UV irradiation. This provides a novel concept for developing long-lasting coatings with multifunctionality.

Keywords: ZIF-8, epoxy coating, g-C3N4, anti-UV aging, Anti-corrosion