Study On The Corrosion Behavior Of Stainless Steel Bipolar Plates In Cooling Water Of Polymer Electrolyte Membrane Fuel Cell

Polymer electrolyte membrane fuel cell is a generating device which takes suchstored chemical energy of fuels and oxidants directly change into electrical energy.Polymer electrolyte membrane fuel cell has the advantages of high energy conversionefficiency, environmentally friendly, quick start in room temperature and noelectrolyte loss. Therefore polymer electrolyte membrane fuel cell has broadapplication prospects in portable power, stationary station and transportation areas.Bipolar plates are part of the key components in the polymer electrolyte membranefuel cell. Bipolar plates have many important functions，such as provide mechanicalsupport to the membrane electrode assembly, uniformly distribute the reactive gases,collect and conduct electrical current, remove excess product water from the reactionzone and dissipate heat. Stainless steel is regarded as ideal bipolar plates materialused for polymer electrolyte membrane fuel cell, this is due to stainless steel hasexcellent electrical conductivity, excellent thermal conductivity, good mechanicalproperties, high gas impermeability, easy processing，low cost and so on. Currently,one of the hot research problems of stainless steel bipolar plates is the corrosionbehavior in the reaction zone of PEMFC. There is almost no research about thecorrosion behavior of stainless steel bipolar plates in the circulating cooling water ofPEMFC. In this paper, we propose corrosion mechanism of stainless steel bipolarplates in circulating cooling water according to the basic structure and workingprinciples of PEMFC; The change laws of pure deionized water in the circulationprocess of PEMFC are studied; Many researches are focused on the corrosionbehavior of304stainless steel plates in circulating cooling water of PEMFC througha series of experiments; The relationship between the corrosion behavior of304stainless steel plates in circulating cooling water and voltage/time are also discussed.Some conclusions can be drawn as followings:(1) The pure deionized water (conductivity is0.42uS·cm-1) as cooling water usedfor PEMFC, the conductivity of circulating cooling water is increased to47uS·cm-1when the PEMFC stack operates30min. The coupled plasma emission spectrometer test results show that the circulating cooling water contains large amounts of metallicelements, such as Ca, K, Na, Zn, Mg and Fe. This shows that pure deionized waterwill be contaminated with impurity ions during the operation of PEMFC stack,leading to the conductivity of circulating cooling water increase.(2) Electrochemical testing results show that the current of304stainless steelplates in pure deionized water is very small. This indicates that the electrochemicalstability of304stainless steel plates in pure deionized water is good. The current of304stainless steel plates in circulating cooling water is large. This indicates that theelectrochemical stability of the304stainless steel plates in the circulating coolingwater is poor and the304stainless steel plates in circulating cooling water with highconductivity are prone to corrosion.(3) The corrosion behavior of304stainless steel plates in circulating coolingwater is studied by electrochemical corrosion experiment.304stainless steel platescorrode in the circulating cooling water with the effect of voltage. Both anode andcathode stainless steel plates surface produce much bubbles. There is dissolution ofstainless steel in anode side result in a significant reduction of anode area, a lot oftawny sediment is found to be deposited on the cathode electrode. Energy dispersespectroscopy results indicate that the corrosion product contains elements such as Fe,Cr, Ni, Si and O.(4) The relationship between the corrosion behavior of304stainless steel platesin circulating cooling water and voltage/time is studied by electrolytic corrosionexperiments. Experimental results indicate that the corrosion behavior of304stainless steel plates in contact with simulated circulating cooling water has a positivecorrelation with the voltage. The corrosion current of304stainless steel in circulatingcooling water is almost no change which means that the304stainless steel platesoccur corrosion in circulating cooling water with a constant corrosion rate.