Preparation And Performance Study Of Conductive Anticorrosive Coating On Stainless Steel Bipolar Plates

As one of the most important components in proton exchange membrane fuel cells?PEMFC?,bipolar plates not only play a role in collecting and transferring current and providing structural support for membrane components,but also their cost and performance are whether fuel cells can be widely used key elements.Stainless steel is used to manufacture bipolar plates because of its advantages of excellent conductivity,high corrosion resistance,and cheap material cost.However,stainless steel has excessive surface contact resistance and corrosion which will also occur after long-term operation in acidic environments.Therefore,the method of stainless steel surface modification is used to reduce the surface contact resistance and improve the corrosion resistance of the bipolar plate.In order to meet the requirements of contact resistance and corrosion resistance after modification of the stainless steel surface coating,this paper designed and prepared a multi-layer multi-functional protective coating system,and through X-ray photoelectron spectroscopy?XPS?,X-ray diffractometer?XRD?,scanning Measurement methods such as electron microscopy?SEM?and electrochemical testing analyzed the coating morphology,structure,composition and performance,and explored its corrosion resistance mechanism.First,the structure and performance of Cr-C surface layer were optimized.The results show that the deposition potential has a significant effect on the morphology,composition,corrosion resistance and surface contact resistance of the electroplated Cr-C surface layer.When the deposition potential is-1.8VSCE,the prepared Cr-C coating has a dense amorphous structure,showing the lowest surface contact resistance and corrosion current density.Secondly,electroplated Ni-Mo,electroplated Ni-Mo-P,and electroless Ni-Mo-P were selected as the intermediate layer materials,and a multi-layer multi-functional protection system was optimized.performance.The results show that the uniform and dense surface morphology of electroless Ni-Mo-P can improve the compactness of the surface layer Cr-C and improve the physical shielding effect of the coating on the stainless steel substrate.When the surface Cr-C coating has defects and the corrosion solution penetrates into the Ni-Mo-P intermediate layer through the Cr-C defects in the surface layer,the presence of Mo in the Ni-Mo-P coating not only forms a chemical passivation film on the coating surface It inhibits the anode activation process and prevents the development of Ni-Mo-P corrosion,effectively inhibits the occurrence of point or crevice corrosion at defects to penetrate into the substrate,so that the substrate is protected from corrosion.The surface contact resistance?ICR?of the Ni/Ni-Mo-P/Cr-C protective coating prepared by electroless Ni-Mo-P as the intermediate layer material is 4.5m?·cm²?140N/cm²?at 70?,In a simulated environment of 0.5 mol/L H₂SO₄+2 mg/L HF,the corrosion current density is 0.85?A/cm²,which meets the basic requirements of the US Department of Energy?DOE?for the performance index of bipolar plates?ICR<10 m?·cm²,I<1?A/cm²?.