Formation of a protective nitride layer by electrochemical nitridation on 316L SS bipolar plates for a proton exchange membrane fuel cell (PEMFC)

Abstract

In the present study, an attempt has been made to increase the corrosion resistance of 316L stainless steel (SS) bipolar plates (Bp) through electrochemical nitridation using a nitrate bearing electrolyte solution of 0.1 M HNO₃ and 0.5 M KNO_3. The X-ray photoelectron spectroscopy (XPS) studies revealed that the modified SS was covered with ammonium ions and mixed nitrides, namely CrN and Cr₂N, on the surface. The average contact angle value with water for nitrided SS favored a PEMFC operating environment. The electrochemical corrosion behaviour was studied in a simulated PEMFC environment (0.5 M H₂SO₄ and 2 ppm of HF) to ensure that the modified SS exhibits enhanced corrosion resistance. Surface resistance values for both untreated and nitrided SS showed low values and increased conductivity after the polarization studies.