FNC Post Oxidation Processes and Comparisons of Corrosion Resistance Performance

Ferritic-nitrocaburizing (FNC) is becoming a more popular process to improve a part’s mechanical properties and corrosion resistance on plain carbon and low alloy constructional steels.  Advertised as a major contribution to enhanced corrosion resistance, post-oxidation of ferritic-nitrocarburized steel is used to help tie up free iron on the surface and prevent/delay corrosion in service.  There are different methods of oxidizing the steel after the FNC process.  Different trademarked processes claim to provide more corrosion resistance than other similar processes.  This paper will focus on the post-oxidation process and review the different oxygen-containing media used for oxidation.  Those processes will be compared and tested to determine how much the oxidation portion of the processes enhances corrosion resistance and which method provides the best corrosion resistance.