Passivity of iron in alkaline solutions studied by in situ XANES and a laser reflection technique

Journal Article · Tue Jun 01 04:00:00 EDT 1999 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.1391897· OSTI ID:680024

Schmuki, P ^[1]; Buechler, M; Virtanen, S; Boehni, H ^[2]; Isaacs, H S; Ryan, M P ^[3]

---

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

Passivity of iron in alkaline solutions was investigated by in situ X-ray absorption near edge spectroscopy (XANES) and with a laser absorption technique. In 0.1 M NaOH, no significant material loss takes place during reduction of the iron passive film, but the ferric passive film is converted completely to a ferrous film. Subsequent anodic polarization leads to growth of a new passive film underneath the converted layer. By multiple potential stepping a thin iron film (100 {angstrom}) (between reduction and oxidation potential range) can be completely converted from the metallic state into an oxide. This thick oxide layer remains electrochemically active, i.e., during potential cycles the redox reactions Fe(II) {yields} Fe(III) and FE(III) {yields} Fe(II) take place in the entire layer. The formation of such a porous oxide/hydroxide layer does not take place when ethylenediaminetetraacetic acid (EDTA) is added to electrolyte, as the ferrous layer formed during reduction is dissolved in presence of EDTA. The behavior of the Fe electrode during potential cycling in NaOH + EDTA becomes reversible with respect to oxide formation and reductive dissolution.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 680024
• Journal Information: Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 6 Vol. 146; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DISSOLUTION
EDTA
IRON
PASSIVATION
PROTECTIVE COATINGS
SODIUM HYDROXIDES
VALENCE