Austenitic Stainless Steels (ASS) own their name & applications to the phenomena of passivity & they have assumed status of a special class of materials for a variety of applications because of their excellent combination of properties at high temperature fabricability & possessing high corrosion resistance coupled with cost effectiveness. The passive region of a ASS as defined by the low current region between the active – passive transition & the pitting potential or the transpassive potential is discussed in terms of solid solution alloying & microstructure. This is primarily due to formation of thin film on their surface. Film may be formed of adsorbed oxygen or other gas of ions or due to electronic configuration of atoms making stable oxide film. Metal beneath the film still remains active. Therefore nature quality & mechanism involved in its formation are main factors accounting for passivation behavior of these steels. The technological developments in steel making have given rise to different SS with improved mechanical physical & corrosion resistant properties like increasing Molybdenum content increases the pitting or localized corrosion resistance of SS in chloride containing environment. In this thesis an attempt has made to understand affect of alloying element & to study the passivation behavior of different ASS by electro chemical methods in oxidizing reducing & neutral environments. AC Impedance Surface Analysis studies the nature & quality of the film. The surface morphology & sensitization effect were also studied using standard metallographic techniques.