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Abstract: 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.
Keywords: niobium; bipolar plate; corrosion resistance; fuel cel
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