Electrodeposition of conductive PAMT/PPY bilayer composite coatings on 316L stainless steel plate for PEMFC application

Stainless steel fulfills most of the requirements as bipolar plates in Proton Exchange Membrane Fuel Cell. However, it undergoes severe corrosion in fuel cell operating condition. This can be resolved by coating the stainless steel with corrosion resistive conducting polymers. In this study, homogeneous and adherent conductive Poly(2-amino-5-mercapto-1,3,4- thiadiazole)/Polypyrrole (PAMT/PPY) mono and bilayer polymer composite coatings are electrosynthesized on 316L SS in 0.5 M H₂SO₄ by cyclic voltammetry and chronopotentiometry. The hydrophobicity and surface morphology of the coatings are analyzed by contact angle and scanning electron microscopy respectively. The polymer coatings are evaluated in 0.5 M H₂SO₄ medium by potentiodynamic polarization and impedance techniques at 25 °C. The polarization results reveal that PAMT on PPY composite coating shifts the E_corr of the 316L SS towards noble direction. The EIS study reveals that the R_f value of PAMT on PPY coating is significantly higher by three orders (x10³ Ωcm²) of magnitude than uncoated 316L SS. The corrosion performance of the coatings in simulated PEMFC environment is investigated by potentiodynamic and potentiostatic studies. Results show that the PAMT on PPY and PPY on PAMT bilayer coatings are stable and increased the corrosion potential by about 410–470 mV and 275–310 mV (SCE) in simulated cathodic and anodic conditions respectively. This investigation reports that the PAMT on PPY bilayer coating is serving as a good physical barrier and protecting the 316L SS against corrosion in PEMFC environment.