Improvement of Electrical Conductivity and Corrosion Resistance of 316L Stainless Steel by Low Temperature Constant Current Nitriding

This paper aims to solve the deterioration of the performance of 316LSS caused by hydrogen evolution reaction during constant potential electrochemical nitriding, and proppose the galvanostatic electrohemical technology. The effects of reduction current density on the surface morphology, corrosion resistance, hydrophobicity and interfacial contact resistance of 316LSS were studied by cyclic voltammetry (CV), chronopotentiometry, electrochemical impedance spectra (EIS), potentiodynamic polarization, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). When the reduction current density was 5 mA/cm2, the nitrogen-doped 316LSS showed hydrophobic property and the maximum hydrophobic angle was 103.7°, and the interface contact resistance was 8.9 mΩ·cm2 at 140 N/cm2, and the corrosion current density was 0.025 μA/cm2 in 0.5 mol/L H2SO4 and 5 mg/L F– test electrolyte. The corrosion current density of the same plate was less than 1 μA/cm2 in the durability test of cathode and anode for a total of 13 hours, and there were only a few corrosion pits after corrosion. The properties of 316LSS are obviously improved after being modified by nitriding in the mixed solution of 0.5 mol/L KNO3 and 0.1 mol/L HNO3. In the process of galvanostatic electrochemical modification, the selective dissolution of iron oxide film and the doping of chromium oxide by nitrogen improve the stability and conductivity of 316LSS. This work sheds new light on the development of 316LSS bipolar plate with low cost and long service life. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.