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On the Mechanism of breakdown of passivity of iron for instationary conditions

✍ Scribed by B. P. Löchel; Priv.-Doz. Dr. H.-H. Strehblow

Publisher
John Wiley and Sons
Year
1980
Tongue
German
Weight
665 KB
Volume
31
Category
Article
ISSN
0947-5117

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✦ Synopsis

Abstract

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.

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