Enhanced pitting corrosion resistance of 304L stainless steel by plasma ion implantation

High‐nitrogen, austenitic stainless steels combine a variety of superior mechanical properties with an increased resistance to localized pitting/crevice corrosion in halide environments. However, nitrogen content in the bulk is restricted during normal melt/solidification processes due to limited solubility, which, if exceeded, leads to nitride formation and possible sensitization. Plasma ion implantation (PII) techniques may result in much higher nitrogen contents via nonequilibrium surface modification. PII of nitrogen into 304L stainless steel, and its subsequent effect on the pitting corrosion of this alloy, has been investigated. The implantation process at the University of Tennessee Microwave Plasma Facility results from a large‐volume (206 l  ), steady‐state, uniform plasma, generated by up to 2 kW of 2.45 GHz microwave power. Samples were negative pulse biased to potentials of 10 and 20 kV, with doses ranging from 1014 to 1018 ions/cm2. Rutherford backscattering spectroscopy analyses of dose unif...