Developing anticorrosion epoxy composite coating based on PEG-gallic acid complex functionalized two-dimensional zeolitic imidazolate framework nanosheets

Two-dimensional Metal-organic frameworks have recently emerged as promising materials for enhancing the anticorrosion protection performance of polymeric coatings. In this study, ZIF-ZG@PEG-GA nanofiller was synthesized by modifying zeolitic imidazolate framework nanosheets with a polyethylene glycol-gallic acid (PEG-GA) complex shell, and subsequently incorporated into waterborne epoxy matrix. Potentiodynamic polarization analysis revealed that the addition of ZIF-ZG@PEG-GA to a 3.5 wt% NaCl solution reduced the corrosion current density from 5.528×10 −6 A/cm 2 to 1.892 × 10 −6 A/cm 2 . Electrochemical impedance spectroscopy (EIS) analysis revealed that ZGPG/EP exhibited superior protective performance after 42 d of immersion, with the highest |Z| f=0.01Hz (1.87 × 10 9  Ω·cm 2 ), R coat (4.27 × 10 8  Ω·cm 2 ), and R ct (1.43 × 10 9  Ω·cm 2 ). Furthermore, EIS analysis of scratched coatings demonstrated that ZIF-ZG@PEG-GA effectively impeded corrosion propagation and prevented further coating degradation. The enhanced anticorrosion performance is attributed to the passive protection by increasing the diffusion resistance of corrosive species, and the active protection through the release of gallic acid from the PEG-GA complex.