Long Term Corrosion Investigation of Cold Rolled High Nitrogen Steels in Simulated Body Fluid

The corrosion behavior of cold rolled and annealed (solution treated from 1050 C) Ni-free high nitrogen austenitic stainless steels (HNSs) was assessed in simulated body fluid (SBF) using weight loss (long term) method. Surface analysis of the lms formed and composition of species on these steels exposed to SBF was done using X-ray photoelectron spectroscopy (XPS). It was detected that increase in nitrogen content signicantly increased the corrosion resistance i. e. decreased weight loss in solution annealed (0 % cold worked) condition. The cold working had noteworthy impact on the corrosion resistant properties. The weight loss and corrosion rates decreased with increasing degree of cold working and nitrogen content in the alloy. The XPS results indicated that the main elements in the passive oxide layer are Cr, Fe, Mo and Mn. Cr-oxide (ox) Cr-hydroxide (hy) ratio and Fe-oxide (ox) Fe-hydroxide (hy) ratio were observed higher in case of rolled material than annealed material indicating that the passive films on rolled materials are more protective which correspond to slow dissolution rate and improve its corrosion resistance. X-ray diffraction proles of annealed as well as deformed alloys were revealed and no evidence of formation of martensite or any other secondary phases was observed.