Impedance measurements were made for AISI 304L and 316L stainless steels in a 5% NaCl solution at room temperature. Nyquist plots in the pitting potential region show three loops: a capacitive loop at high frequencies; a loop with inductive effects at intermediate frequencies; and a second capacitive response at low frequencies. An equivalent electrical circuit has been proposed to model the AISI 304L and 316L SS/NaCl systems. Negative capacitance and resistance were obtained. The impedance data do not satisfy Kramers-Kronig (KK) transforms. Details of the KK determinations are included.