Improving performance in PEMFC by applying different coatings to metallic bipolar plates

Abstract

In the present study, aluminum plates were coated with three different materials using thermal spray in order to be used as bipolar plate in proton exchange membrane fuel cells (PEMFC). NiCr, NiCrBSi, and (Co,Ni)CrAlY were selected as coating materials due to their high corrosion resistance. High velocity oxy-fuel (HVOF) was the spray coating method used in the present study. Accelerated corrosion resistance and interfacial contact resistance (ICR) tests were conducted on the coatings under simulated PEMFC conditions. The corrosion current density of the bipolar plates coated with NiCrBSi, NiCr, and (Co,Ni)CrAlY, on Al-substrate in the simulated cathodic environment of a proton-exchange membrane fuel cell (PEMFC) were found to be −4.98 (1.03 E−5), −3.89 (0.00012), and −2.91 (0.0012) A/cm2, respectively. Also Ecorr for NiCr, NiCrBSi and (Co,Ni)CrAlY were −0.36, −0.31 and −0.39 (±0.01) volt. The electrochemical impedance spectroscopy (EIS) and polarization curves show that the NiCrBSi coating has higher corrosion resistance than other coatings. The interfacial contact resistance between the NiCrBSi and NiCr coated samples and carbon paper are the smallest on typical fuel cell stack compression force of 140 N/cm2. Then, long-term durability tests were conducted on single cell with coated bipolar plates. The results showed a considerably better performance and no decrease in cell voltage in the single cell with NiCrBSi coated bipolar plates. It can be concluded that the performance of NiCrBSi alloy coated bipolar plate developed using HVOF coating is acceptable in fuel cells as bipolar plate.