Preparation Of Polyaniline/graphene Composite Coating On The Surface Of Stainless Steel Bipolar Plate By Electrochemical Method And Its Corrosion Resistance Study

Owing to its easy processing property,excellent electrical and thermal conductivity,and low cost,stainless steel becomes one of the most popular bipolar plate materials for the proton exchange membrane fuel cell(PEMFC).However it is easy to suffer from corrosion in long time service and then affect its service life.So surface modification is needed to improve its corrosion resistance.Polyaniline and graphene have been reported to be used to improve the corrosion resistance of stainless steel respectively,but study on composite materials of polyaniline and graphene using for the corrosion protection for stainless steel has been reported rarely,especially in the working environment of PEFMC.This paper tries to use the electrochemical method to prepare polyaniline / graphene double-layer composite coating and polyaniline / graphene co-deposition coating on the surface of stainless steel plate material.And the influence parameters on deposition behavior,mechanism of deposition,microstructure and composition of the two coating were analyzed.The electrochemical corrosion behavior and corrosion resistance mechanism of these two kinds of coatings in simulated PEFMC operating conditions were researched.And the advantages and disadvantages of the two methods were compared.In the preparation of double layer composite coating,polyaniline film was firstly synthesized on the surface of stainless steel by cyclic voltammetry,and then dispersion aqueous solution of graphene oxide was dropped onto the surface of polyaniline coating,after drying,samely by using cyclic voltammetry,polyaniline / graphene bilayer coating was prepared by reduction of graphene oxide on the top of the polyaniline.For the codeposition film,the graphene was modified by acid oxidation,then to get the soluble sulfuric acid mixed solution of aniline monomer and acidified graphene.By using chronoamperometry,polyaniline/graphene codeposition film was prepared by one-step deopsition,and the effect of the acidified graphene content on the properties of the deposited film was explored.The two types of composite coatings were characterized by FTIR,XRD,SEM,EDAX and water contact angle test.The peak shift of infrared spectra of polyaniline/graphene co-deposition coating compared with single polyaniline coating indicated the relative strong interaction force between the polyaniline and graphene molecules.In the co-deposition film,polyaniline grains dispersed in the layer-structure of grapheme to form graphene lamellar stacking being mingled with polyaniline grains.And the crystallinity of polyaniline is greatly reduced so that the characteristic peaks in XRD spectra of polyaniline disappeared.The mutual effect between polyaniline and graphene on the crystalline form and infrared spectra property is relatively small in the bilayer films.And the lamellar structure of graphene was the mainly observed topography in the surface of the bilayer film.In the co-deposition coating,graphene contains more unreduced polar groups,and the surface also contains polar polyaniline blend,so the degree of reduction of hydrophilicty of the surface is weaker than the double layer coating.Electrochemical corrosion behavior study and corrosion morphology observation showed that the both the two kinds of composite films could improve the corrosion protection performance compared with single polyaniline layer.For co-deposition film the best corrosion protection performance was obtained at acidification graphene concentration of 0.1 g/L.The operation of co-deposition method is simple,but the protection effect is slightly inferior to that of the double layer coating.The double layer coating method is more complex,but the film thickness and compactness are more excellent,and the weaken degree of hydrophily of the surface is more notable,so the corrosion prevention effect is more remarkable.