Nickel-Free Stainless steel (NFSS) was improved as the next generation in biomedical implant alloys. Inappropriate heat treatment or prolonged exposure at high temperatures in NFSS affects the secondary phase formation and harms corrosion resistance. In this study, the effect of cooling rate during solution treatment on the corrosion behavior of NFSS was observed using Polarization and Electrochemical Impedance Spectroscopy (EIS). NFSS-10Mn-16Cr-3Mo-0.2N was melted in Induction Furnace, solution treated at 1050 ℃ for one hour, and quenched in various media: furnace environment, water, brine, and open-air. The NFSS-10Mn-16Cr-3Mo-0.2N has 21.29 points for the %wt Cr equivalent and 5.25 points for the %wt Ni equivalent. The metallographic result confirmed that the microstructure of NFSS-0.2N consists of elongated ferrite and martensite phase. The cooling rate increased, and the average diameter decreased to 0.021 mm. Consequently, the large of passivity zone (Epass 94.5 to 497.32 mV in 0.2-2 x 10-6 A of Ipass) was obtained after furnace cooling. The passivity starts from the passivating species (Cr2O3) adsorption on a metal surface and improves corrosion resistance. In addition, slowed cooling sample has lower values of corrosion (-38.2 mV for Ecorr, 0.128 μA/cm2 for Icorr, and 1.49x10-3 mm/year) and highest value of impedance |Z’|. The Bode plot of EIS shows that the passive film being formed at low frequency and the reduction of cooling rate leads to increasing the arc radii.