DBPapers
DOI: 10.5593/sgem2012/s02.v2041

THE MECHANISM OF TRANSPASSIVE DISSOLUTION OF ASS N25 AUSTENITIC STAINLESS STEEL IN SULPHURIC ACID SOLUTION

N. LAJCI, M. METIKOS HUKOVIC, Z. PETROVIC
Wednesday 1 August 2012 by Libadmin2012

References: 12th International Multidisciplinary Scientific GeoConference, www.sgem.org, SGEM2012 Conference Proceedings/ ISSN 1314-2704, June 17-23, 2012, Vol. 2, 313 - 324 pp

ABSTRACT

The transpassive dissolution of ASS N25 nitrogen alloyed austenitic stainless steel
austenitic stainless in a 0.5 M sulphate solution with pH 0.4 was studied using a cyclic
voltammetry on static and rotating electrode and electrochemical impedance
spectroscopy. The main process in the transpassive potential region was found to be the
release of soluble Cr(VI). Secondary passivation readily occurs for ASS N25 alloys
whereas chromium dissolves at high current densities in the whole transpassive
potential range. The secondary pasivation occurs, probably due to enrichment of Fe in
the outermost layer of the surface film. The obtained results are compared with pure
chromium as the main alloys constituents. A kinetic model of the processes is proposed,
including a two step transpassive dissolution of Cr via a Cr(VI) intermediate species and
the dissolution of Fe(III) through the anodic film.

Keywords: Nitrogen alloyed austenitic stainless steel, Transpassive dissolution, Cyclic
voltammetry, Kinetic model.