Robust ZIF-67/AC/PDMS hybrid nanocomposite for superhydrophobic steel protection

A superhydrophobic coating synthesized from Cobalt-based Zeolitic Imidazolate Framework (ZIF-67), Activated Carbon (AC), and Polydimethylsiloxane (PDMS) was successfully fabricated on a steel substrate. This coating was synthesized with concentration ratios S2 (1 wt% ZIF-67), S3 (3 wt% ZIF-67), S4 (5 wt% ZIF-67) and S5 (7 wt% ZIF-67), respectively. XRD and HR-TEM were applied to examine the crystalline structure and morphology of the synthesized nanocomposite. The results revealed S4 (5 wt% ZIF-67) composite as an optimized coating as it performed an exceptional surface wettability with a water contact angle (WCA) of 170° and superior chemical stability. Long-time laps of immersion tests in different pH range (3-11) nominated the S4 coating for retaining superhydrophobic integrity over 48 h, even placed in aggressive acidic or alkaline media. Electrochemical Impedance Spectroscopy (EIS) confirmed a robust corrosion protection performance of the S4 coating, as it recorded a high charge transfer resistance (R_ct) reaching 5 × 10⁵ Ω⋅cm². This enhanced performance is attributed to the modified roughness resulting from the ZIF-67/AC framework and the low surface energy of the PDMS matrix that stabilized a persistent Cassie-Baxter state. These results demonstrate the ZIF-67/AC/PDMS nanocomposite as a promising strategy for sustained corrosion protection of steel in severe industrial environments.