The protection mechanism of surface modified NPhE/TNC epoxy coating. Display omitted •NPhE/TNC modifier was fabricated for improving the epoxy coating properties.•Salt spray accelerated corrosion test displayed a superior protective behavior for NPhE/TENC-E coating.•SEM survey confirmed the mitigation performance of modified NPhE/TNC coatings.•The proper acids and alkali resistance was offered for the modified 2.5% NPhE/TNC epoxy film.•TiO, TiOC and OTiO linkages with DGEBPA prohibited the transmission paths of aggressive species. Nanocomposite modifiers reinforce the whole characteristics of epoxy coatings for different steel surface applications. To support this concept, sol-gel synthesized TiO2 nanoparticles (TNPs) were mixed with nonylphenol ethoxylate (NPhE) to form nonylphenol ethoxylate/TiO2 nanocomposite (NPhE/TNC) as a modifier for epoxy coating applied on the C-steel surface. TNPs were characterized by XRD, SEM and HR-TEM techniques. Various modified NPhE/TNC epoxy coating formulations with different loading levels (0.5, 1, 1.5, 2 and 2.5%) by weight were prepared. FT-IR spectra were used for characterizing of the formed nanocomposites. The anti-corrosion behavior of surface-modified NPhE/TNC coated films versus unmodified conventional epoxy was studied by salt spray accelerated corrosion test. The obtained results demonstrated a considerable improvement in the rust grade, blistering size and frequency, and adhesion strength of modified NPhE/TNC epoxy nanocomposite coated films and affirmed by SEM morphology survey. The impact resistances of unmodified and modified NPhE/TNC epoxy coatings were measured where the best impact resistance was recorded for NPhE/TENC-E coated film at 51 J. Acids and alkali chemical immersion test was performed to check the chemical immovability for the surface-modified NPhE/TNC coated films against conventional epoxy where NPhE/TENC-E coating showed the suitable immovability levels.