The effect of 1, 8-Diazabicyclo [5.4.0] undec-7-ene (DBU) on corrosion of alloy 600 coupons was studied at room temperature. The experiments were carried out using AC-Impedance spectroscopy at frequency range of 100 kHz -5 Hz to study response of alloy 600 to the presence of DBU in an aqueous solution. Equivalent circuit representing frequency response of DBU in aqueous solution on alloy 600 is presented. The Nyquist plots showed very good corrosion protection initially but the film failed after exposing to amine solution for 24 hours.