Dual phase (DP) steels have a great deal of importance in the automotive industry. These steels are used to fabricate structural parts of vehicles with the goal of passenger safety. In this study, the corrosion properties of DP 600 and 800 steel in 3.5wt.% NaCl environment were evaluated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and weight loss methods. Although the samples were quite similar to each other in their composition, it was observed that the very small differences changed the corrosion resistance property. For this reason, the calculated charge transfer resistance (R-ct) of the DP-800 in the 3.5wt.% NaCl environment was 51% greater than that of the DP-600 sample. This finding was confirmed by using weight loss, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and optical profilometer (OP) analysis.