Electrochemical corrosion characteristics of conducting polypyrrole/polyaniline coatings in simulated environments of a proton exchange membrane fuel cell

A bilayer conducting polymer coating consisting of an inner layer of polypyrrole (Ppy) with large dodecylsulfate ionic groups and an external polyaniline (Pani) layer with small SO42− groups was electrodeposited on type 304 stainless steel bipolar plates of a proton-exchange membrane fuel cell (PEMFC). The corrosion performance of conducting Ppy/Pani bilayer coatings on 304SS in simulated cathode and anode environments (0.1 M H2SO4 solution bubbled with air or H2 at 80 °C) of a PEMFC was investigated by electrochemical impedance spectroscopy, polarization and open circuit potential measurements. The experimental results showed that the Ppy/Pani bilayer increased the free corrosion potential of the steel by about 310 mV (SCE) and 270 mV (SCE) in simulated cathodic and anodic environments of the PEMFC, respectively. Long-term exposure studies showed that the bilayer was highly stable and inhibited the corrosion of the steel effectively in simulated cathodic and anodic environments, which was attributed to its “self-healing” effect.