Boronization of nickel and nickel clad materials for potential use in polymer electrolyte membrane fuel cells

A new low-cost, nickel clad bipolar plate concept is currently being developed for use in polymer electrolyte membrane fuel cells. Reported in this paper are the details of a powder-pack boronization process that could be used to establish a passivation layer on the electrolyte exposed surfaces of the bipolar plate in the final stage of manufacture. Results from energy dispersive X-ray analysis, X-ray diffraction, and scanning electron microscopy indicate that under moderate boronization conditions a homogeneous Ni3B layer grows on the exposed surfaces of the nickel. The thickness of this layer depends on the time and temperature of boronization according to a Wagner-type scale growth relationship. At higher temperatures and longer reaction times, a Ni2B overlayer forms on top of the Ni3B during boronization. Preliminary results indicate that boronization dramatically improves the corrosion resistance of nickel.