Developing epoxy-based anti-corrosion functional nanocomposite coating with CaFe-Tolyl-triazole layered double hydroxide@g-C3N4 as nanofillers on Q235 steel substrate against NaCl corrosive environment

• CaFe LDH intercalated with tolyl-triazole inhibitor (TTA) was synthesized using the in-situ intercalation co-precipitation approach. • g-C 3 N 4 was then used to fabricate the nanohybrid of CaFe-TTA LDH and g-C 3 N 4 via simple sonication and stirring. • The prepared materials were used as nanofillers in epoxy coatings for corrosion protection application. • The electrochemical and salt-spray test results revealed the excellent protection and self-healing activity of the coating. • The DFT simulation supported the corrosion protection mechanism and reaction kinetics during the corrosion process. Nanofillers are considered the most aspiring materials in recent years for the anti-corrosion functional coatings applied to the metal surface. Herein, the CaFe-tolyl-triazole layered double hydroxide (CaFe-TTA LDH) nanoplates and CaFe-tolyl-triazole layered double hydroxide@graphitic carbon nitride (CaFe-TTA LDH@g-C 3 N 4 ) nanohybrids were successfully prepared using the facile approaches. The prepared CaFe-TTA LDH nanoplates/CaFe-TTA LDH@g-C 3 N 4 nanohybrids were incorporated into the epoxy resin to develop corrosion-resistant nanocomposite coatings. The resistances at 0.01 Hz (|Z| 0.01 ) of EP/CaFe-TTA LDH and EP/CaFe-TTA LDH@g-C 3 N 4 samples were reduced by one order of magnitude after 60 days of immersion in 3.5% NaCl solution (from 5.49 × 10 8 Ω cm 2 to 4.42 × 10 7 Ω cm 2 and from 1.18 × 10 9 Ω cm 2 to 2.25 × 10 8 Ω cm 2 respectively), compared to the pristine EP coating, which decreased approximately two orders of magnitude (from 2.61 × 10 8 Ω cm 2 to 7.69 × 10 6 Ω cm 2 ). The localized electrochemical impedance spectroscopy (LEIS) and salt spray tests further explored the self-healing activity of the coatings and revealed that the scratched EP/CaFe-TTA LDH@g-C 3 N 4 coatings maintained excellent corrosion resistance. The pull-off adhesion test showed an improved adhesion strength as compared to the pristine epoxy coating. Moreover, the density functional theory simulation confirmed the reaction mechanism of the nanofillers during the corrosion process. Hence, the results revealed that the EP/CaFe-TTA LDH@g-C 3 N 4 -based coatings delivered superior barrier/active inhibition performance due to the labyrinth and self-healing effect of nanofillers, suggesting a promising avenue for the development of a variety of nanocomposite coatings for various functional applications.