In order to enhance the corrosion resistance of 304 stainless steel,niobium was electrodeposited on its surface in air- and water-stable ionic liquids.The electrochemical behaviors of bare and niobium-coated 304 stainless steel were evaluated by electrochemical tests in a simulated proton exchange membrane fuel cell (PEMFC) environment.The results showed that niobium could be electrodeposited on the surface of 304 stainless steel from ionic liquids,and a smooth and strong chemical inert compound film was obtained on the surface of 304 stainless steel,which was mainly composed of NbO and Nb2O5.The thin composite film acted as a barrier and remarkably improved the corrosion resistance of 304 stainless steel in the PEMFC environment.