Electropolymerization of camphorsulfonic acid doped conductive polypyrrole anti-corrosive coating for 304SS bipolar plates

Conductive polymer coating doped with large molecular organic acid is an alternative method used to protect stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). However, it is difficult to select the proper doping acid, which improves the corrosion resistance of the coating without affecting its conductivity. In this study, large spatial molecular group camphorsulfonic acid (CSA) doped polypyrrole (PPY) conductive coating was prepared by galvanostatic electropolymerization on 304SS. The electrochemical properties of the coating were evaluated in 0.1   M H 2 SO 4 solution in order to simulate the PEMFC service environment. The results indicate that the coating increased the corrosion potential and shifted E corr towards more positive value, particularly the j corr value of PPY-CSA coated 304SS was dropped from 97.3 to 0.00187   μA   cm −2 . The long-term immersion tests (660   h) show that the PPY-CSA coating exhibits better corrosion resistance in comparison with the small acid (SO 4 2− ) doped PPY-SO 4 2− or PPY/PPY-SO 4 2− coatings. Moreover, the PPY-CSA coating presents low contact resistance and maintains strong corrosion resistance during the prolonged exposure time due to barrier effect and anodic protection.