CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 5
nitrogen forming Cr 2 N phase in 304L SS due to limited solubility in austenitic stainless steel, as
evidenced from GIXRD and XPS analysis [21].
Fig. 5.5b: XPS spectra of nitrogen (N1s) region (dose 1×10 17 N + /cm 2 ) [21].
5.2. 6 Open circuit potential vs. time measurement
The OCP-time measurements for unimplanted and nitrogen implanted 304L SS during
immersion for 6 h in 1 M HNO 3 are shown in Fig. 5.6 [21]. In unimplanted as well as in low dose
of nitrogen implantation (1×10 15 , 1×10 16 N + /cm 2 ), open circuit potential showed steady state
indicating spontaneous, and stable passive film formation, and in case of higher dose nitrogen
implanted specimens (1×10 17 N + /cm 2 , 2.5×10 17 N + /cm 2 ), OCP shifted towards more nobler values.
The OCP values improved from 100 mV vs. Ag/AgCl in unimplanted condition to 395 mV vs.
Ag/AgCl with highest dose of nitrogen implantation. The improvement in open circuit potential by
nitrogen implantation is an indication of stable passive film formation in nitric acid medium, and
is attributed to enrichment of nitrogen at the surface of the alloy. When exposed to the