Corrosion Behavior of Niobium-Coated 316L Stainless Steels as Metal Bipolar Plates for Polymer Electrolyte Membrane Fuel Cells

Niobium was coated on 316L stainless steel by pulsed direct-current (DC) magnetron sputtering to improve corrosion behavior. The applied bias voltage highly affected the microstructure and crystallographic features, which lead to improved corrosion behavior. Due to the increased bias voltage, the microstructure of the niobium coating layer presented a smaller crystallite size and a densified structure, which obviously reduced the number of pinholes in the coated layer. Additionally, an increase in the degree of orientation toward the (110) plane, the most densely packed plane, lead to reduced dissolution of metal ions. Therefore, a pure niobium coating layer effectively protected the metal bipolar plate from a highly corrosive environment of polymer electrolyte membrane fuel cell (PEMFC) stacks. In particular, higher bias voltages of 600 and 800 V induced improved corrosion resistance, which satisfied the demand for the bipolar plate.

Automated summary

Coating niobium on 316L stainless steel using pulsed direct-current magnetron sputtering significantly improves corrosion resistance. Increased bias voltage leads to a denser microstructure with smaller crystallite size, reducing the number of pinholes and preventing metal ion dissolution, effectively protecting the bipolar plate in a corrosive environment. Higher bias voltages of 600 and 800 V induce enhanced corrosion resistance, meeting the demands for the bipolar plate.