In the present study an assessment has been made of the air-formed passive film and the passive film existing after a short exposure to a synthetic seawater environment on austenitic (UNS S31603), superaustenitic (UNS S31254 and UNS S32654) and superduplex (UNS S32760) stainless steels and a Ni-based alloy (UNS N06625) using X-Ray Photoelectron Spectroscopy (XPS). Assessment of their corrosion behavior has been made through use of electrochemical accelerated tests supported by post-test microscopy. The passive film on the Ni-base (low Fe) UNS N06625 alloy is remarkably similar to those formed on the high Cr and Mo stainless steels. It has been demonstrated that the Fe/Cr ratio in the passive film is dependent on alloy composition and on the conditions to which the material has been exposed and a general correlation between passive film constitution and corrosion resistance is evident. Keywords : Corrosion, XPS, Passive Film, Seawater