This paper aimed to test the epoxy and polyester blends as an organic coating on mild steel against the harsh marine environment (NaCl 3.5 wt%) that causes corrosion. The electrochemical impedance spectroscopy (EIS) and fitting impedance data by ZsimpWin 3.22 software were used to estimate the barrier of the samples for different exposure times (30, 60, 90, and 120 min). One equivalent electrical circuit was used to fix the physical barrier and get an appropriate fitting. Epoxy and polyester blend coating showed excellent corrosion protection for steel. The blend coating showed better protection and stability against aggressive salt solutions over time. The connection between the coating film's dielectric properties (impedance spectrum) and how it acts as a physical barrier protection tells us about the electrochemical process's capacitive behavior. It lets us guess how it will be a barrier to protection in the real world. The observation is the radius of a semi-circle of a real part and the imaginary part of impedance (Z) in the Nyquist plot. The exponential power (n) of the constant phase element (CPE) is much less than one, indicating that CPE is far from a pure capacitor. All the phase angles for all and impedance with frequency in the Bode plot showed behavior similar to immersion times. Atomic force microscopy (AFM) appears as a thin peak topography with uniform disruption, which refers to a constant roughness for the specimen surface.