Investigation on the Relationship between the Surface Chemistry and the Corrosion Resistance of Electrochemically Nitrided AISI 304 Stainless Steel

The relationship between the surface chemistry and the corrosion resistance of electrochemically nitrided AISI 304 stainless steel samples has been investigated. The nitriding treatment was carried out in HNO3 0.1 M and HNO3 0.1 M + KNO3 0.5 M at room temperature. Samples were subjected to the nitriding procedure for 30 minutes under a cathodic potential of -0.7 VAg/AgCl. The chemical composition of the nitrided layers was assessed by X-ray photoelectron spectroscopy (XPS). Depth profiles of the main elements present in the nitrided layers were also obtained by XPS by etching them with argon ions. The corrosion behavior of the nitrided samples was evaluated by potentiodynamic polarization. The results showed that the nitrided layers consisted of a mixture of chromium nitrides, chromium oxides, iron oxides/oxyhydroxides, and nickel oxide. The best corrosion resistance was obtained by electrochemical nitriding in the HNO3 0.1 M + KNO3 0.5 M solution. This result could be correlated with the composition and thickness of the nitrided layer.