Electrochemical properties of tungsten-alloying-modified AISI 430 stainless steel as bipolar plates for PEMFCs used in marine environment

Abstract

To improve the corrosion resistance and surface electrical conductivity of AISI 430 stainless steel (430 SS) as bipolar plates for proton exchange membrane fuel cells (PEMFCs) used in marine environment, a tungsten alloying layer has been successfully prepared on 430 SS substrate via the plasma surface diffusion alloying technique. The tungsten-modified (W-modified) 430 SS displays a 7-8 μm tungsten alloying layer with a body-centered-cubic structure. The W-modified surface also shows a better hydrophobicity with contact angle of 93.5° and a lower interfacial contact resistance compared with the untreated 430 SS. The potentiodynamic and potentiostatic polarization and electrochemical impedance spectroscopy measurements show that the corrosion resistance of 430 SS is obviously improved in simulated PEMFC environment (0.05 M H2SO4 + 2 ppm HF + 0.01 M NaCl solution at 70 °C), after the plasma surface diffusion alloying process.