In situ XANES study of the cathodic reduction behavior of the passive film on iron and artificial passive films

Technical Report · Wed Oct 01 04:00:00 EDT 1997

DOI:https://doi.org/10.2172/537262· OSTI ID:537262

Schmuki, P; Virtanen, S; Boehni, H ^[1]; Isaacs, H S; Ryan, M P; Oblonsky, L J ^[2]

---

1. Swiss Federal Inst. of Tech., Zurich (Switzerland). Inst. of Materials Chemistry and Corrosion
2. Brookhaven National Lab., Upton, NY (United States)

The objective of the present work is to compare the behavior of the passive film on iron with artificial passive films (thin sputter-deposited films of iron oxides on inert substrates). In situ XANES measurements were used to monitor both dissolution and changes in the valence state of passive films on iron during cathodic reduction in borate buffer and in NaOH. Reductive dissolution of the passive film on iron proceeds by a very similar mechanism as has been found for artificial passive films (thin, sputter-deposited films of iron oxides on inert substrates)--i.e. including a conversion step of the passive film to a lower-valent oxide. With low reduction current densities, the dissolution process does not stop when the metal is exposed but can proceed as active metal dissolution. In NaOH, no or very minor material loss takes place during reduction due to the insolubility of Fe(2+) species in the alkaline solution. By potential stepping of a thin film iron sample between reduction and oxidation range of the passive film, a conversion of the whole sample from metallic film into an oxide film can be achieved.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 537262
• Report Number(s): BNL--64151; CONF-970805--; ON: DE98000296
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORATES
DISSOLUTION
ELECTROCHEMICAL CORROSION
EXPERIMENTAL DATA
IRON
PASSIVATION
PROTECTIVE COATINGS
REDOX REACTIONS
SODIUM HYDROXIDES
VAPOR DEPOSITED COATINGS