Effect of immersion in NaOH solution on ferritic stainless steel as a bipolar plate for polymer electrolyte membrane fuel cells

The surface of 446M ferritic stainless steel (FSS) is modified by immersing in NaOH solution to understand its effect on the interfacial contact resistance (ICR) and corrosion. Immersion in NaOH solution under optimum condition can lead to decrease the ICR value of 446M FSS with no decrease in the corrosion resistance. Immersion of 446M FSS in NaOH solution increases the ratio of Cr oxy-hydroxide/oxide, which contributes to decrease the ICR value. This means that the bound water present in the form of the OH− group in the passive film acts as a donor-type impurity and provides the active sites for electrical conduction in the oxide. This imparts positive effect on the electrical conduction and leads to decrease in the ICR value even after the long-term immersion in the simulated PEMFC environment.

► The immersion in NaOH solution is performed with 446M ferritic stainless steel.
► The immersion in NaOH solution decreases the ICR value of 446M.
► The immersion in NaOH solution increases the OH−/O2− ratio in the passive film.
► The bound water acting as a donor-type impurity leads to the decrease in the ICR.