*2.1.2. Stainless steel*

Stainless steel has been shown to have the potential to meet all of the requirements for bipolar plates. It has a relatively low cost with high electrical and thermal conductivity, good me‐ chanical properties, and ease of machining. Stainless steel bipolar plates[16] can be rapidly manufactured in large quantities by stamping. In the acidic environment within the fuel cell, stainless steel passivates forming Cr2O3 which elevates the interfacial contact resistance.

Most conventional coatings for stainless steel have shown to add to overall cost and also leave surface defects which result in local corrosion, damaging the fuel cell. The development of cost-effective coatings is the most significant research area in metallic bipolar plates. Despite the excellent physical properties and high-volume manufacturing processes available for metal bipolar plates, current technology places the estimated cost at \$60–100/kW or 6 to 10 times the current target for transportation[17].
