A MSssbauer Spectroscopy Study of the Potential Dependence of Passivated Iron Films

The potent ia l dependence of the passive film formed on iron in borate buffer is examined by Mbssbauer effect spec-troscopy. T ransmiss ion measuLements are per formed with a paral lel plate work ing/countere lect rode conf igurat ion to at-ta in in situ data w i thout sacrif icing un i form current d istr ibut ion. When stepped anodical ly, the passive fi lm shows a de-creasing isomer shift and increas ing quadrupo le spl i t t ing with potential. Effects of dry ing for fi lms formed at two di f ferent potent ia ls are also reported. In recent years there has been an increas ing number of Mbssbauer (1-5) and EXAFS (5-6) invest igat ions of passi-vated i ron fi lms because of the possibi l i ty o f obta in ing local struct~#ral in format ion us ing in situ measurements. However, none of these efforts has examined the potent ia l dependence of the passive fi lm except one study (7) in wh ich ex situ convers ion e lectron M6ssbauer spectra were obtained, but relative absorpt ions at di f ferent potent ia ls could not be compared. The present work appl ies in sit