THE EFFECT OF PERMEATED HYDROGEN ON THE PITTING OF TYPE-304 STAINLESS-STEEL

The effect of permeated hydrogen on the pitting behavior of type 304 s tainless steel was investigated using a Devanathan type cell. One side of the stainless steel sheer was galvanostatically charged with hydro gen, while the other side was subjected to pitting tests. The permeate d hydrogen typically enhanced the pitting susceptibility of the stainl ess steel; the pitting potential during potentiodynamic polarization b ecame less noble and the induction period for pitting became shorter. However, the permeated hydrogen did not change the critical pitting po tential determined potentiostatically. The effect of permeated hydroge n on the pitting potential and the induction period diminished after h ydrogen charging was stopped. Analysis by X-ray photoelectron spectros copy showed that the cationic fraction of chromium in a hydrogen-charg ed passive film was lower than that in an uncharged film. Thus, the pe rmeated hydrogen is thought to suppress the aging process of the passi ve film with respect to enrichment of chromium. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.