Application Of Graphene In Metal Anti-corrosion Field

Metal corrosion would cause economic losses and waste of resources.Developing new anti-corrosion coatings to prevent metalscorrosing is very urgent.Graphene with lightweight,chemical stability,antibacterial activity,outstanding barrier property,and excellent thermal and electrical properties was reported to be a promising material in improving the anticorrosion property of metals.Graphene oxide(GO)with different size and oxidation degree was synthesized by Hummers method in this paper.Waterborne alkyd resin/graphene oxide(AR/GO)composite coatingwas prepared by blending GO(as a filler)and waterborne alkyd resin.Fourier-transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),atomic force microscope(AFM),and transmission electron microscopy(TEM)were used to investigate the structure of multi-scale graphene oxide(dispersion,size,and oxidation degree).Tafel polarization curves were used to analyze the effect of multi-scale graphene on the corrosion resistance of waterborne alkyd resins.The anticorrosion effect of AR/GO is enhanced with the increasing of GO content,until the high content of GO(2 wt%)forms a micro-conducting path from the metal surface to the outermost edge of the coating which would accelerate corrosion of metals.When the GO content is 1.5 wt%,with the increasing of the size of GO,the large flake size structure of GO could extend the path of the corrosive medium into the coatings,which is beneficial to the anti-corrosion performance of AR/GO.The effect of oxidation degree of GO on anticorrosion properties of AR is more complex.GO with lower oxidation may increase the aromaticity and inter layerπ-πinteraction and lead the non-uniform dispersion of GO which would decrease the shielding effect of GO to the corrosive medium.With the increasing of the oxidation,the surface structure of the GO may be destructed,which would reduce the electrical properties and mechanical properties of coatings.When the flake size of GO is 120μm and the oxidation degree sp~2/sp~3 is 2.61,the preservative efficiency of AR/GO compound is 98.14%。GO(120μm,sp~2/sp~3=2.61)was be chosen as a filler to prepare AR/GO(GO:1.5wt%)composite coating.And the thermal oxygen aging test of AR/GO was carried out at 100°C.The chemical structure of the waterborne alkyd resin was hardly changed characterized by FTIR.Results suggested that graphene can inhibit the resin’s aging process in some extent.AR/GO system has better corrosion resistance than AR through the electrochemical impedance tests and Tafel polarization curve tests.The C=C bond of the graphene sheets may capture the peroxy radicals generated from the resin ageing process,whichmay inhibit the degradation of the resin.The anti-corrosion effect of the waterborne resin is generally inferior to that of the solvent-based resin.Thus a solvent-type epoxy resin was selected as a film-forming substance.PGO was prepapered byamino modified graphene.And PGO/PANI composite filler was successfully prepared by in-situ polymerization to combine the composite filler have both the barrier properties and conductivity of GOand the redox property of PANI.The epoxy resin(EP)was blended to prepare PPEc.The physicochemical structure of the composite fillers was characterized by FTIR,XRD,TEM andSEM.The effect of PGO content on the anticorrosion effect of composite coatings was studied in this paper.The Tafel curves and electrochemical impedance tests showed that the anticorrosion effect of composites was the best(Rp:1.50×10~7?·cm~2)when the PGO content was 7wt%.The results of accelerated soaking test of PPEc suggested that polyaniline coated with PGO wasuniformly dispersed in the epoxy resin matrix which would effectively slowing down or even preventing the penetration of the corrosion medium into the interior of the coating.After soaking for 24h,the coating still remained good anti-corrosion properties.PGO(7wt%)was be chosen as filler to prepare 7PPEc composite coating.And the thermal oxygen aging test of 7PPEc was carried out at 100°C.The chemical structure of the waterborne alkyd resin was hardly changed characterized by FTIR.Results suggested that graphene could inhibit the resin’s aging process in some extent.According to the adhesion test,the surface of 7PPEc coating did not show bubbling or cracking,but only a few PGO migrated to the surface of the coating after thermal oxidation.The electrochemical impedance test and Tafel polarization curve test revealed that the 7PPEc system was stable in corrosion resistance,indicating that the system had good aging resistance.