An Examination of Current Fluctuations during Pit Initiation in Fe‐Cr Alloys

Abstract

Random fluctuations of the passive current for Fe-Cr alloys of various Cr content were examined, in borate buffer and in the same solution with 0.1M NaC1 added. Frequency spectra of these fluctuations were recorded before and dur- ing pit initiation. No detectable fluctuations were observed in the absence of chlorides, where pitting does not occur. Comparison with the current noise measured before pit initiation indicates that the most important role of the aggres- sive ions is that of increasing the chance of local breakdown of the passive film. Frequency spectra give information concerning the time constants of the various processes, including repassivation. No correlation was found between the rate of attack during pitting and noise amplitude. During