Modified epoxy coatings based on BI@ZIF-8@TA for the application of long-effective corrosion protection

The hydrophilic benzimidazole@ZIF-8@tannic acid (ZBT) nanoparticles and the pH-responsive modified epoxy (EP) coatings based on ZBT were prepared innovatively. The result exhibited that the ZBT had excellent compatibility with the EP coatings, and the addition of ZBT improved the protective properties of the EP coatings, which were attributed to the formation of the Zn(OH)2 deposition film, the inhibitor adsorption film and the ferric tannate film on the steel substrate. Meanwhile, the original adhesion and wet adhesion strengths of the ZBT/EP coatings were both enhanced, which was mainly attributed to the enhanced interaction between the ZBT/EP coatings and the carbon steel, and the crosslinking density and the degree of curing of the coatings were also improved. After 173 days of immersion, the impedance value of the ZBT coatings remained at 7.89 × 107 Ω·cm2, while the EP coatings decreased to 3.94 × 103 Ω·cm2. The wet adhesion loss of EP and ZBT/EP coatings was 63.6 % and 27.1 %, respectively. In the end, the protective mechanism of the ZBT/EP coatings was first proposed.