Barrier properties of innovative epoxy coatings containing 10 or 20 phr of phosphate/phosphonium ionic liquid (IL) were investigated using mainly electrochemical impedance spectroscopy. The impedance diagrams revealed quasi-pure capacitive behavior and the impedance modulus at low frequency, related to corrosion resistance, remains at around 1012 Ω cm2 during immersion time in 0.1 M NaCl solution. The capacitances were graphically extracted from Cole–Cole representations, and the resistances were determined using R//C electric equivalent circuits. Both epoxy–IL coatings were free of porosity and impeded the hydration of the matrix. The results were also compared to those of conventional epoxy coatings, for which hydration occurs owing to their porosity. Results indicate that this new epoxy–IL coating system would offer excellent anticorrosion protection for metallic substrates.