The study of electroplating trivalent CrC alloy coatings with different current densities on stainless steel 304 as bipolar plate of proton exchange membrane fuel cells

• The Cr–C coatings on steel are electroplated for utilization as bipolar plate.
• The electrical conductivity and corrosion resistance increase with carbon content.
• The power density of Cr–C coated steel is superior to the bare steel.

In this study, the trivalent Cr–C coatings were electroplated on stainless steel 304 (SS304) substrates for an application in bipolar plates (BPPs) that was because of coating's excellent electric conductivity and corrosion resistance. The images of scanning electron microscope showed that the thickness of the coatings was between 1.4 and 11.4 μm, which increased with increase of coating current density. The surface morphology of Cr–C plated at coating current density of 10 A/dm2 was smooth, crack- and pinhole-free, while cracks and pinholes appearing in networks were observed apparently in the deposits plated at a higher coating current density. Additionally, the C content in the coating decreased with increasing the coating current density. Moreover, the polarization curve with different coating current densities (10, 30, 50 A/dm2) exhibited the coating prepared at 10 A/dm2 and 10 min possessing the best corrosion resistance (Icorr = 9.360 × 10− 8 A/cm2). The contact resistance of Cr–C plated at coating current density of 10 A/dm2 was the lowest (16.54 mΩ cm2 at 150 N cm− 2), which showed great potential of application. The single cell test with Cr–C coated SS304 prepared at coating current density of 10 A/dm2 as BPPs showed the highest current density (about 791.532 mA/cm2) and power density (about 270.150 mW/cm2).