Corrosion shortens the service period of bipolar plates (BPs) and increases the costs of proton exchange membrane water electrolyser (PEMWE). In this work, TaN coatings are deposited on Ti BPs by magnetron sputtering to improve the corrosion resistance and service period, and the influences of N2 flow on the surface morphology, hydrophobicity, crystallinity, corrosion resistance and interfacial contact resistance of TaN coatings are studied in details. As the N2 flow increases, the roughness of TaN coatings decreases firstly and then increases in accordance with the hydrophobicity. At the N2 flow of 3 sccm, TaN coating with the larger grain size presents the lower roughness and hydrophobicity. As a result, the coating possesses the lowest Icorr of 2.82 μA?cm-2 and the highest Ucorr of -0.184 V vs. RHE in the simulated PEMWE environment. After 10 h potentiostatic polarization test, fewer corrosion pits are observed on the TaN coatings deposited at the 3 sccm N2 flow. Hence, the TaN coating on BPs could improve the corrosion resistance properties and thus enhance the electrolysis efficiency (68.87%) in the tested single electrolytic cell after 75 h.