TaN coatings were deposited on Ti bipolar plates by magnetron sputtering to improve corrosion resistance and service life. The influence of N₂ flow rate on the surface morphology, hydrophobicity, crystallinity, corrosion resistance, and interfacial contact resistance of TaN coatings was studied. Results show that as the N₂ flow rate increases, the roughness of TaN coatings decreases firstly and then increases, and the hydrophobicity increases firstly and then decreases. At the N₂ flow rate of 3 mL/min, TaN coating with larger grain size presents lower roughness and high hydrophobicity. The coating possesses the lowest corrosion current density of 2.82 μA·cm^-2 and the highest corrosion potential of -0.184 V vs. SCE in the simulated proton exchange membrane water electrolyser environment. After a potentiostatic polarization test for 10 h, a few corrosion pits are observed on the TaN coatings deposited at an N₂ flow rate of 3 mL/min. After 75 h of electrolytic water performance testing, the TaN coating on bipolar plate improves the corrosion resistance and thus enhances the electrolysis efficiency (68.87%), greatly reducing the cost of bipolar plates.