Pitting and Crevice Corrosion Behavior of Nitrogen-Bearing Type 316LN Stainless Steels

摘要

Pitting and crevice corrosion behavior of two different nitrogen containing type 316LN-A (0.076 percent N) and 316LN-B (0.086 wt percent N) stainless steels have been studied using potentiodynamic polarisation method in 0.5 NaCl solution. The passive films developed on these alloys were characterised using Auger Electron Spectroscopy (AES). Studies on the influence of cold working (10 percent and 20 percent), thermal ageing (at 650 deg C - 200h), pickling and passivation treatment indicated a higher pitting and crevice corrosion resistance for alloy with 0.086 wt percent N content compared to the alloy with 0.076 wt percent N content. The results also indicated that increase in cold working level (10 percent and 20 percent), and thermal ageing treatment at 650 deg C for 200h reduced both pitting and crevice corrosion resistances of these alloys. Chemical treatments like pickling (20 percent HNO_3+ 3 percent HF) and passivation (20 percent HNO_3 enhanced the pitting corrosion resistance. The result is supported with AES analysis of the chemically treated surfaces indicating an enrichment of chromium and Iron oxide with nitrogen. The optical microscopy and SEM studies after the pitting and crevice corrosion studies were also carried out