Research On Corrosion Resistance Of Aluminum Alloy Bipolar Plate In Simulated Proton Exchange Membrance Fuel Cell Environment

Compared with stainless steel,graphite and titanium alloy,aluminum alloy has the advantages of wide application,low density,high strength,light weight and wide application field.In the environment of PEMFC,the metal surface is still easily eroded by F^-,H⁺,SO₄^2-and other corrosive ions.Therefore,the surface of aluminum alloy needs to be treated to improve corrosion resistance and stability.In order to solve the corrosion problem and stability of aluminum alloy under the condition of strong acid?rich oxygen?,this paper mainly uses the anodizing method to build porous structure on the surface of aluminum alloy,combined with other physical and chemical methods to build composite film on the surface of aluminum alloy,so as to achieve the corrosion resistance of aluminum alloy under the condition of rich oxygen and strong acid:1.The porous honeycomb structure was constructed on the surface of aluminum alloy by anodizing,and the composite film of pan and pan-go was prepared by coating on the porous aluminum alloy.Scanning electron microscopy?SEM?,atomic force microscopy?AFM?and X-ray photoelectron spectroscopy?XPS?were used to characterize the surface morphology and composition of the film.The results show that the corrosion potential of polyacrylonitrile film is positive shifted by 141 m V and the corrosion current density is reduced from 1.341 × 10-4 A·cm-2 to 4.868 × 10-8 A·cm-2,which is four orders of magnitude lower than that of untreated aluminum alloy.Its protection efficiency is as high as 99.96%.By adding graphene oxide?GO?,the film resistance and stability in the simulation solution were improved.After soaking in 0.5 M H₂SO₄+ 2ppm HF and oxygen enriched for 5 days,the protective efficiency of the composite film to the substrate was still over 90%,which indicated that the composite film had excellent stability to the corrosion resistance of aluminum alloy.Through SEM and AFM analysis,the porous structure of the surface is conducive to the infiltration of polyacrylonitrile solution,thus strengthening the adhesion between polyacrylonitrile and the substrate.At the same time,due to the physical barrier effect of Polyacrylonitrile and graphene oxide on corrosive ions,the corrosion resistance of the modified aluminum alloy in acid solution is enhanced.2.A honeycomb porous structure is constructed on the surface of aluminum alloy by anodizing method,and a carbon-boron nitride composite film with good corrosion resistance is prepared on the surface of porous aluminum alloy.The surface morphology and composition of the film were analyzed using scanning electron microscope?SEM?and other characterization methods.The electrochemical test of the modified aluminum alloy shows that the aluminum alloy with a composite film layer is under strong acid?0.5 M H₂SO₄ + 2 ppm HF?conditions compared to the untreated aluminum alloy and the carbon-coated aluminum alloy.The corrosion current density dropped from 1.341 × 10-4 A·cm-2?AA5052?and 5.370 × 10-5 A·cm-2?carbon layer aluminum alloy?to 2.466 × 10-8 A·cm-2,A decrease of 3-4 orders of magnitude,the protection efficiency of the composite film layer on the substrate is as high as 99.98%.At the same time,the composite membrane layer has been immersed in a cathodic environment?0.5 M H₂SO₄ + 2 ppm HF,oxygen-enriched?of a simulated proton exchange fuel cell for five days,and still has good corrosion resistance.It is observed by SEM that the surface coating still has protective effect on the modified aluminum alloy after soaking for five days,which is mainly because the layered structure of boron nitride blocks the corrosion of corrosive ions.3.Anodizing was used to construct a honeycomb porous structure on the surface of aluminum alloy,and hydrothermal method was used to synthesize a reduced graphene oxide-tin dioxide composite coating in situ on the surface of porous aluminum alloy.Scanning electron microscope?SEM?,X-ray diffraction?XRD?and other characterization methods were used to analyze the surface morphology and composition of the film.Electrochemical testing of the film of this sample by an electrochemical workstation showed that the reduced graphene oxide-tin dioxide composite coating was more effective in oxygen-rich and strong acid?0.5 M H₂SO₄ + 2 ppm?compared to the untreated aluminum alloy.HF),the corrosion current density of the sample decreases by 2-3 orders of magnitude,and the load transfer resistance increases by 4 orders of magnitude.The protection efficiency of the composite film layer to the substrate is as high as 99%.The coating has excellent corrosion resistance to aluminum alloys.After XRD characterization,tin dioxide was successfully synthesized on the anodized aluminum alloy surface to protect the aluminum alloy surface.