The Study On The Metallic Bipolar Plates Of Fuel Cell Modified By Films Deposited By AIP

Bipolar plates are the key components of PEMFC and occupy the most part of the cost and the total weight of a fuel cell stack, the performance of bipolar plates influence the performance of the fuel cell. Ideal bipolar plates should have good conductivity and machining property, and good anti-corrodibility property.Metallic bipolar plates usually have good conductivity and machining property, and they are the best choice for the material of bipolar plates. However, the anti-corrodibility property for metallic bipolar plates of the fuel cell is poor, and the production of the corrosion causes a high contact resistance and the performance of the fuel cell decreases. Depositing flims on the surface of the metal to improve the performance of the metal is an effective way to solve the problem. The actual emphases is to lower the contact resistance and improve the anti-corrodibility property.The metal has good conductivity, because it owns a large number of movable free electrons. However, the chemistry corruption and electrochemistry corruption are the processes that the metal atom loses its free electrons and produces metallic cation. So the anti-corrodibility property and conductivity are incompatible. Except for some kinds of heavy metals such as Au and Ag, it is difficult to obtain a kind of metal which both has good conductivity and anti-corrodibility property.This research paper chooses the stainless steel as the substrate of the bipolar plates, and changed its property through depositing films consisting of some cheap metals and their nitride by Arc Ion Plating. Choose Cr and Ni/Cr as the main electric materials which are based on the needs for metallic bipolar plates, and improve the anti-corrodibility property of films through the proper design of the nitrification and the structure. Deposite Cr-N series multilayer films and Ni-Cr-N series multilayer films on the stainless steel sheets by Arc Ion Plating. The principle of the design is that the pure metallic films can reduce the contact resistance, and metallic films with nitrification can improve anti-corrodibility property. Finally, the films can both reduce the contact resistance and improve anti-corrodibility property. Film surface morphology, hardness, structure, adhesion force, the contact resistance, and electrochemical corruption property are investigated.The result shows that the Cr-N multilayer films can effectively improve the anti-corrodibility property of bipolar plates. Comparing with the naked stainless steel bipolar plates, the contact resistance decreases by an order of magnitude, and the anti-corrodibility property improves by 2 orders of magnitude. The contact resistance of Ni-Cr-N multilayer films is the least one, near to the standard for the actual application, and the anti-corrodibility property is also better than that of the naked stainless steel. Both two films have the potential for replacing the electrodeposit Ag.