The effect of nitrogen on the corrosion resistance of austenitic stainless alloys containing molybdenum

Abstract

The microstructure, corrosion resistance, and electrochemical characteristics of stainless alloys containing 18 to 20 wt pct chromium, 13 to 25 wt pct nickel, and 3 to 6 wt pct molybdenum, with up to 0.25 wt pct nitrogen were evaluated. Nitrogen was found to suppress the formation of secondary phases during thermal aging and welding. The crevice and intergranular corrosion resistance of the examined alloys was improved by the addition of nitrogen. Resistance to general corrosion attack was not altered by the nitrogen content of the alloys. The range of passive potentials was expanded by increasing alloy nitrogen contents, while the critical corrosion current densities were reduced. The localized corrosion resistance of autogenously welded samples was improved by adding 5 wt pct nitrogen to an argon shieldgas. A survey of the literature accompanies the test results.