Electrochemical behaviour of an AISI 304L stainless steel implanted with nitrogen

In this paper the electrochemical behaviour of AISI 304L stainless steel implanted with nitrogen is studied in alkaline media and chloride-containing media, and it is compared with the behaviour of the unimplanted material. Implantation was done at a saturation dose (4 × 10¹⁷ ions cm⁻²) at an acceleration voltage of 150 keV. The results show a clear improvement of the corrosion resistance for the implanted specimens. No pitting potential is observed in the alkaline media or in the neutral media containing high chloride concentration. The improved corrosion resistance is presumed to be due to the modifications that N⁺ implantation induces in the passive layer that is naturally formed on the alloy. XPS analysis reveals Ni⁰ and Cr³⁺ enrichment in this passive layer. Moreover, a carbon-rich layer is found at the outermost part of the passive layer. The presence of this outermost layer is verified with electrochemical impedance measurements and SEM observations.