Plasma-nitrided ۳۱۶L stainless steel as a bipolar plate in polymer fuel cells

In this research, plasma nitriding method was used to improve the contact resistance and corrosion resistance of the ۳۱۶L stainless steel. In order to perform the plasma nitriding process, a working cycle of ۷۰% and a frequency of ۸ kHz were used. The Operation time ۴ h, gas composition N۲/H۲ :۱/۳ and pressure ۶ torr were considered. Also, the temperature of the plasma nitration process was as ۳۸۰ oC.Nitriding is one of the most widely used technologies in surface engineering. Phase S formed on the surface of austenitic stainless steel during the nitriding process, in addition to improving hardness and abrasion resistance, also improves the corrosion resistance property. Therefore, it can be mentioned that nitriding process is one of the methods that increases the corrosion resistance of steels. Also, the nitride layer formed due to the penetration and diffusion of nitrogen atoms into the substrate does not have the problem of adhesion in the joint and does not peel under electrochemical corrosion. Therefore, this method has been considered by researchers as one of the most important methods used to cover the surface of bipolar plates of polymer fuel cells [۱, ۲].After surface treatment, potentiodynamic polarization and potentiostatic polarization tests were performed on bare and plasma-nitrided ۳۱۶L stainless steel sheet (۱۰۰ μm). ICR test was performed after electrochemical tests on plasma-nitrided stainless steel sheets. According to the potentiodynamic polarization curves shown in Figures ۱ and ۲, the corrosion rate for ۳۱۶L stainless steel sheet relative to nitrided stainless steel sheet has decreased from ۱.۰۷ μA /cm۲ to ۰.۶ μA /cm۲. On the other hand, the potentiostatic polarization curves, which can be seen in Figures ۳ and ۴, indicated that the corrosion current density after one hour for raw stainless steel sheet compared to nitrified sample increased from ۰.۳۳ μA/cm۲ to as ۰.۷ μA/cm۲. The ICR results are shown in Figure ۵. after electrochemical tests, the ICR value at a pressure of ۱.۴ kPa for the first and second samples was measured as ۱۱.۴ mΩ.cm۲ and ۹.۳ mΩ.cm۲, respectively.

کلیدواژه ها:

Plasma nitriding ، ۳۱۶L stainless steel ، Polymer fuel cell ، Corrosion ، Contact resistance