Surface‐enhanced Raman spectra (SERS) have been obtained from an iron electrode that contains on its surface a discontinuous layer of silver. The mechanism of Raman enhancement of this system has been explored through a systematic study of the time stability and the potential reversibility of SERS spectra as well as the relation between the amount of silver deposited and the intensity of SERS. It is concluded that the local electromagnetic field mechanism is the dominant contributor to enhancement in this system. It is also shown that the anodic polarization characteristics of the iron electrode are unaffected by the presence of the discontinuous silver layer. Comparisons between in situ and ex situ, as well asin situ and semi‐in situ Raman spectra have indicated the importance of characterizing the anodic passive film by in situtechniques. The limitation and possible extensions of the SERS technique in studies of passivity are also discussed.