A β-phase crystal poly (vinylidene fluoride) incorporated epoxy-based composite coating with excellent oxygen barrier and anti-corrosion

Among the factors causing metal corrosion, oxygen and the corresponding electrochemical reaction are important aspects of the whole corrosion process. Herein, epoxy (EP) as the matrix resin, and poly (vinylidene fluoride) (PVDF) as the blend were used to fabricate EP/PVDF composite coatings. The EP/PVDF20 (mass ratio of PVDF was 20% that of EP) obtained excellent anti-corrosion performance. The |Z| 0.01 Hz impedance of EP/PVDF20 after 90 days of immersion in a 3.5 wt% NaCl solution was about 2.9 × 10 11  Ω cm 2, which did not significantly change from the initial test value. The O 2 gas transmission rate of EP/PVDF20 was significantly reduced to only 22% that of EP (22.4 vs. 104.6 cm 3 /m 2 ·24 h·0.1 MPa), and the maximum water absorption was decreased by nearly 20%, indicating EP/PVDF20 has excellent oxygen resistance and water resistance. After 7 days of immersion in a coupling environment of 3.0 MPa pure O 2 and the 3.5 wt% NaCl solution, the (low frequency) impedance of EP/PVDF20 was still 99% of the initial value, suggesting it has good corrosion resistance under adverse conditions. The protection mechanism of EP/PVDF20 is ascribed to the blending of the epoxy resin and PVDF in improving corrosion resistance, and the dense and orientation structure of β-phase crystal PVDF in EP/PVDF20 is more favorable for blocking either oxygen gas molecules or corrosive substances. This study provides a new application field for polymer composites and presents a new idea for preparation of oxygen-resistant and anti-corrosion composite coatings.