Smart epoxy coatings reinforced with g-C3N4/Clinoptilolite hybrid nanofillers for corrosion protection and self-healing

In this study, clinoptilolite (C) zeolite was used as an epoxy coating filler, modified with g-C 3 N 4 (CN) via thermal condensation to enhance its properties. The CN content on zeolite, determined by thermogravimetric analysis, was 17.03 % (CN–C). Fillers loaded with Zn 2+ ions through cation exchange and electrostatic interactions were labeled as C–Zn, CN–Zn, and 17.03 % CN–C–Zn. The synthesized materials were characterized using FESEM-EDX, XRD, FTIR, DRS, and BET. The successful loading of Zn 2+ ions was confirmed by XRD, FTIR, and FESEM-EDX analysis. In Tafel polarization tests, the 17.03 % CN–C–Zn material demonstrated 59.1 % inhibition efficiency by forming a protective film on bare steel after 24 h of soaking; this film provided simultaneous anodic and cathodic protection. Also, the release of Zn 2+ ions from the investigated materials was monitored using ICP, EIS, Tafel, and FESEM-EDX analysis. CN as a semiconductor (2.67 eV bandgap) improved UV shielding, reducing color change (ΔE) around 8–11 % versus bare epoxy. The EIS, salt spray, and cathodic delamination tests demonstrated that EC/17.03 % CN–C–Zn coating provided more effective corrosion protection against saline electrolytes than other investigated coatings in this paper. The ׀Z׀ 10mHZ of the EC/17.03 % CN– C–Zn is 676 times greater than that of the bare epoxy after 202-day immersion. The self-healing ability of scratched coatings was evaluated via EIS during immersion in 3.5 wt.% NaCl. The EC/C–Zn and EC/17.03 % CN–C–Zn coatings demonstrated a total resistance R T (R coat + R charge transfer ) roughly two times higher than the bare epoxy. Also, EC/17.03 % CN–C–Zn increased the mechanical strength of the bare epoxy by around 72.5 %.