Study On Preparation And Anti-Corrosion Properties Of Modified-Graphene Waterborne Coatings

Shortcomings of traditional solvent based anticorrosion coatings are high porosity,poor hydrophobicity and low coating strength.It is a common method to mix nanoparticles in conventional coatings for reducing porosity,improving hydrophobicity and enhancing coating strength.Graphene is a kind of two-dimensional alveolate carbon nanomaterials with large specific surface area,high compactness and chemical inertness.Because of the strong physical shielding property for corrosive medium,the organic coatings can effectively improve anticorrosion properties which mixed with graphene.However,the dispersion of grapheme in the coatings is low,and it is easy to agglomerate,which leads to corrosion pits and destroys the structures of coatings.In order to improve the dispersibility of grapheme,in-situ polymerization and one-step hydrothermal method were used to prepare modified graphene waterborne epoxy resin coating.Anticorrosive properties of modified composite coatings were analyzed and compared for revealing anticorrosion mechanisms.The graphene/polypyrrole composite(rGO/PPy)was prepared by in-situ polymerization of graphene(GO),pyrrole monomer and reduced by hydrazine hydrate;A new type of rGO/PPy waterborne anticorrosive coating was prepared by doping the filler of rGO/PPy in the waterborne epoxy resin(WEP)as film forming substances.On the basis of upper experiment,the graphene/p-phenylenediamine composite(FGO)were synthesized by one-step hydrothermal method.The aqueous solution of FGO was dispersed in waterborne epoxy resin(WEP)by wet transfer method with addition of film-forming agent and curing agent.The anticorrosive FGO/WEP coatings were prepared after heating and drying.The crystal lattice structure,the combination mode of functional groups,distance of lamellar structure and surface morphology of composites were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy(Raman)and Scanning electron microscopy(SEM).And the anticorrosive performance of the coatings on Q235 carbon steel was detected by using Open circuit potential(OCP),Tafel polarization curves(Tafel),Electrochemical impedance spectra(EIS),weight loss,corrosion morphology and water contact angle.The results showed that the graphene/polypyrrole nanomaterial was prepared successfully.The corrosion potential(Ecorr),the corrosion current density(Icorr)and the protection degree(Pi)of bare steel of 1wt% rGO/PPy waterborne epoxy resin were-613 mV,46.42μA·cm-2 and 91.02%,respectively.Compared with rGO anticorrosive coating,the corrosion current density and the corrosion rate of rGO/PPy composite coating were decreased by 38.62μA·cm-2 and 5 times,respectively.The graphene oxide/p-phenylenediamine(FGO)composite material was prepared by using one-step hydrothermal method.The FGO was dispersed in waterborne epoxy resin(WEP)by wet transfer method.PPDA and GO layer were intercalated vertically and WEP macromolecules were also integrated in the GO layer.The GO agglomeration was greatly reduced in the WEP.Corrosion potential(Ecorr),corrosion current density(Icorr)and the protection degree(Pi)of bare steel of FGO/WEP coatings were-453 mV,34.87μA·cm-2 and 93.24%,respectively.Compared with GO/WEP anticorrosion coatings,the corrosion current density decreased by 76.62μA·cm-2 and the corrosion rate reduced by 6 times;The particle transfer impedance and barrier performance of FGO/WEP coating were larger.Its hydrophilicity was lower;After 20 days of corrosion,the coating surface only slightly stratified.The FGO/WEP coatings exhibited high stability.In this paper,rGO/PPy and FGO composites were prepared by using modified grapheme for improving the dispersion of graphene in waterborne epoxy resin matrix.As the dispersion was improved,the stability,anticorrosion,and water resistance of composite coating were improved.