| Proton exchange membrane fuel cell（PEMFC）is a new type of energy conversion device,which directly converts chemical energy stored in hydrogen into electricity through proton exchange membrane and catalyst,with the advantages of high efficiency,cleanliness and low temperature,and has wide application potential in transportation,portable energy,aerospace and other fields.The bipolar plate is an important component of PEMFC,which accounts for about 45%of the total cost and 80%of the total weight of the reactor,playing the role of support protection,current collection and gas diversion.Stainless steel bipolar plate has superior processing performance,good mechanical properties,excellent gas tightness,low cost,is the ideal material for the preparation of fuel cell bipolar plate.However,stainless steel bipolar plates are prone to surface passivation under the operating conditions of PEMFC,leading to an increase in the internal resistance of the cell.Coating the surface of stainless steel bipolar plates with a conductive and corrosion-resistant coating is widely regarded as a proven surface modification method.a-C coating has become the focus of research by many scholars and companies for its excellent corrosion-resistant and conductive properties.a-C coating has the disadvantages of low lifetime and easy peeling during fuel cell operation.In this paper,the corrosion resistance and contact resistance of a-C coatings are investigated in terms of preparation parameters（temperature and bias）and microstructure（Cr N interlayer）using magnetron sputtering as a means of preparation,and the mode of coating failure is studied.The main results are as follows.（1）The a-C coatings prepared at different bias voltage at different temperatures have different properties.At temperatures of 130°C and 250°C,the increase in preparation bias will lead to a decrease in coating thickness,and the coating thickness at250℃is higher than that at 130℃.The detection results of Raman spectroscopy show that the sp2 content of the coating prepared at temperature 130℃increases with the increase in bias pressure;the coating prepared at 250℃sp2 hybridization content increases first and then decreases.The indentation and scratch tests show that the mechanical bonding force of the coating is around 30 N under this experimental condition,and the coating does not peel off large pieces;the corrosion resistance of the coating decreases and then increases with the increase of bias voltage,and the best corrosion current density is 0.55μA/cm2,which reaches the standard of DOE;the contact resistance of the coating decreases with the increase of bias voltage,and the smallest contact resistance appears at 250℃bias voltage of 400 V,reaching 15 mΩ·cm2.（3）a-C coating with Cr N interlayer can effectively improve the corrosion resistance and contact resistance performance of carbon coating.The corrosion current density of the composite structure of the coating can reach 0.7247μA/cm2 contact resistance reaches 10.56 mΩ·cm2,basically reaching the DOE standard set by the U.S.Department of Energy;the introduction of the Cr N interlayer increases the coating bonding force from 30 N to 60 N.The Cr N interlayer can effectively improve the a-C carbon coating bonding force and improve the coating service life. |
