PROPERTIES OF CORROSION RESISTANT AND HYDROPHOBIC COATING ON TITANIUM BIPOLAR PLATES
In order to improve the corrosion resistance and hydrophobicity of titanium bipolar plates for proton exchange membrane fuel cells,indium tin oxide(ITO)coatings with different tin content were prepared on titanium substrate by sol-gel method.The surface morphology and microstructure of the coatings were characterized by scanning electron microscopy(SEM),atomic force microscopy(AFM)and X-ray diffraction(XRD).The boonding between coating and substrate is evaluated by bonding method.The hydrophobicity and corrosion resistance of the coatings in simulated battery environment(0.5 mol/L H2SO4+2 mg/L HF)were tested by water contact angle tester and electrochemical measurement instrument.The results show that the ITO coatings with different tin contents have different effects on improving the hydrophobicity and corrosion resistance of titanium bipolar plates.ITO coating of In3+∶Sn4+=1∶0.10 is the most uniform and dense,and well bonded with the substrate.Its corrosion current density is 2.336 μA/cm2,which is an order of magnitude lower than that of the substrate.Its water contact angle inereased from 43.98° on the substrate to 121.87°,showing hydrophobic,and its charge transfer resistence was 55 455 Ω·cm2,which was about 145 times tho change transfer resistence value of the substrate,and it provides the best corrosion proteetion for titanium metal bipolar plates.
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