CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 5
143-146]. Nitrogen as an alloying element in austenitic stainless steel has met with wide range of
success, apart from being an austenite stabilizer, (1) it enhances passivation property in
aggressive solutions, (2) provides beneficial effects from intergranular and pitting corrosion, (3)
increases hardness, friction coefficient, load bearing capacity and wear behavior, and (4)
improves fatigue resistance and cavitation corrosion behaviour [38, 51-54]. Song et al [147] have
shown improvement in passivation property, and inhibition of anodic dissolution process of
nitrogen implanted 18-8 austenitic stainless steel in acidic media. Hirvonen et al [148] have
detected minor change in peak current density for nitrogen implanted AISI 420 SS in 1 N H 2 SO 4
medium. Study by Kamachi Mudali et al [149] for pitting, and intergranular corrosion resistance
of nitrogen implanted type 304 SS showed significant increase in pitting resistance as well as
insignificant intergranular attack in acid chloride media. Picard et al [143] have indicated
decrease in passive current density for nitrogen implanted AISI 304 SS as compared to untreated
sample in 1 N H 2 SO 4 medium, and study by Martinez et al [150] have reported improvement in
corrosion property of nitrogen implanted 304L SS in chloride media. Nevertheless, nitrogen ion
implantation has its own limitations, as it is not suited for very high abrasive conditions due to
limited depth of implanted layer, and increase in energy of implantation to increase the depth of
implanted layer deteriorates the corrosion resistance due to accumulation of surface defects
owing to ballistic effect of ions [151]. Moreover, the mechanism by which nitrogen ion improves
corrosion resistance is still under considerable debate.
The objective of the chapter is to evaluate the effect of sub-surface modification using
nitrogen ion implantation on surface property and corrosion resistance of AISI 304L SS in nitric
acid medium (1 M) using surface analytical, electrochemical, and morphological studies. The
various effects of nitrogen implantation, and its correlation with passivity, and corrosion
resistance are discussed and highlighted in this chapter.