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On the Mechanism of breakdown of passivity of iron for instationary conditions
Author(s) -
Löchel B. P.,
Strehblow H.H.
Publication year - 1980
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19800310505
Subject(s) - nucleation , electrolyte , passivity , metal , adsorption , chemistry , electrode , inorganic chemistry , chemical physics , materials science , metallurgy , organic chemistry , electrical engineering , engineering
The formation of Fe 2+ ‐ions is studied in 0.5 M H 2 SO 4 and 1 M HClO 4 during changes of the potential of passivated iron specimen with the rotating‐ring‐disk technique. An Fe 2+ ‐pulse is found during the decrease of the electrode potential serving as an indicator for the short exposure of small areas of bare metal to the electrolyte. In the presence of aggressive anions the repassivation of these defects is prevented leading to the formation of pits. The increase of the pit nucleation after potential changes coincides qualitatively with the occurrence of the Fe 2+ transients. The adsorption mechanism may be excluded for these conditions because it postulates the action of aggressive anions for the very beginning of the breakdown process.