Bipolar plate is a key component of Polymer Electrolyte Fuel Cell (PEFC) with several essential functions, and has to resist to harsh cell operating conditions. Usually made of graphite or carbon composite, this component is studied worldwide in order to develop a commercially viable alternative: different ways have been being investigated, and to date, stainless steel (SS) appears as a good candidate material, but corrosion issues hinder its general use. This paper offers a comprehensive study of parameters impacting SS plate material corrosion through ex situ electrochemical investigations. Impact of ageing under various conditions is reported and studied in terms of film structure, semiconductivity behaviour, and cation release, on as received 316L and 904L alloys, and also surface-treated by low-cost surface modifications. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.