Enhanced electrical conductivity of two layers AlN–TiN coating on SS316L as bipolar plate using plasma focus device

• AlN–TiN coating is deposited on SS316L as PEM bipolar plate using plasma focus.
• Average size of nanoparticles in the coated sample is 50–100 nm.
• The ICR of TiN–AlN coated sample is 5 times lower than TiN sample.
• Such an improved ICR leads to the significant enhanced of fuel cell performance.

Two layers of AlN–TiN coating were deposited onto SS316L as PEM bipolar plate using plasma focus device for 5, 10 and 20 shots number. The XRD patterns of all coated samples reveal formation of TiN, Ti2N and AlTi3N crystallite phases on the surface. Using the Scherrer formula the crystallite size of the coating layer is estimated about 20–40 nm. Thickness of the two layers coating obtained from cross sectional SEM of the samples is in the range of 5–15 μm. Through the potentiostatic test considerable decrease of the current density of the 20 shots coated samples is achieved. The ICR of the samples reduced as follows: 20 shots < 10 shots < 5 shots < bare sample which confirms that the electrical conductivity of the bipolar plate is increased due to the formation of AlN and TiN coating. SEM morphology of all samples before and after potentiostatic tests shows that the coated samples are exposed to less corrosion compare with the bare sample. These results are in good agreement with electrochemical tests and the 20 shots sample has the lowest corrosion.