Influence of CrN-coating thickness on the corrosion resistance behaviour of aluminium-based bipolar plates

The electrical and corrosion properties of CrN-coated aluminium alloy Magnal-45 (Al-5083) probes have been evaluated, in order to assess their viability to be used as bipolar plates in polymer electrolyte fuel cells. To this end, ceramic micro-layers of chromium nitride (CrN) with different thicknesses (3, 4, and 5 μm) have been deposited on the surface of the Al alloy (Al-5083) using the physical vapour deposition (PVD) technique. A decrease in 2 orders of magnitude of Icorr values for the coated Al has been observed compared to the as-received Al-alloy when the probes have been exposed to simulated anodic conditions in a micro-reactor. On the other hand, when subjected to a cathodic-simulated environment, the Al–CrN probes with 3 μm and 4 μm coatings have shown a decrease in Icorr of one order of magnitude, while a variation of two orders of magnitude has also been obtained for the 5 μm coating.