Research On The Application Technology Of Graphene In Waterborne Epoxy Resin Anti-corrosion Coating

Waterborne epoxy resin has lower VOC content than oily epoxy resin,and does not pollute enviroment accords with the national sustainable development strategy.However,the water-based epoxy resin has poor film formation and water resistance,poor shielding effectiveness for corrosive medium such as oxygen and water molecules,so that its applications were limited.Graphene,a novel two-dimension nanomaterial can overcome some shortcomings of water-based coatings by using it as filler and has a good application prospect in the field of anticorrosion.In this paper,we comparatively research on the application technology and effect of graphene oxide,graphene,mixed grapphene suspension and graphene powder in waterborne epoxy resin anticorrosive coating.The research results are great significance for the application of graphene in waterborne anticorrosive coating.The specific contents are as follows.(1)Preparation technique of graphene,named rotating packed bed(RPB)which invented by our group,is used to prepare graphene(R-RGO)suspension and graphene oxide(R-GO)suspension.Graphene/waterborne epoxy resin composite coatings were prepared by blending and concentrating.Analyzing polarization curves,Waterborne epoxy resin(WEP)protection efficiency(?)is only 82.1%,the ? of graphene oxide/waterborne epoxy resin(1%R-RGO/EP)and graphene/waterborne epoxy resin(1%R-RGO/EP)reach 99.5%and 99.9%,respectively.The analysis results of EIS further verify the above conclusion.The contact angle between WEP and NaCl solution is 53.1°,the contact angle between 1%R-GO/EP and NaCl solution is reduced to 45°,the contact angle between 1%R-RGO/EP and NaCl solution is double than that of WEP,reaching 106.9°,making the coating hydrophobic.In salt water resistance test,the coating of WEP began to shed after 41 days,the coating of R-GO/EP was damaged and substrate was corrosion after 84 days,R-RGO/EP coating shedding,substrate corrosion and so on was oberved after 135 days.The mechanism of graphene-reinforced waterborne epoxy resin coating for corrosion resistance is due to the following reasons.Firstly,reduced graphene oxide can fill holes formed during the solidification of WEP,enhancing deseness.Secondly,reduced graphene oxide increases the contact angle between the NaCl solution and the coating which can form a hydrophobic layer.Thirdly,reduced graphene oxide has good conductivity which can transfer electrons generated by corrosion on the metal surface to the outside of the coating,OH-and Cl-outside the coating cannot corrode with metal.Finally,reduced graphene oxide extends the path of corrosive media into the substrate.(2)Preparation technique of graphene,named high speed rotor-stator mixer(HRSM)which invented by our group,is used to prepare mixed graphene(MG)suspension.For the first time,the application of mixed graphene in waterborne epoxy resin anti-corrosion coating was studied.SEM shows good dispersion of graphene in WEP.The corrosion current(Icorr)of the coating is two orders of magnitude smaller than that of WEP and the corrosion voltage(Ecorr)is increased by 52%.The maximum contact angle between composite coating and NaCl solution can reach 103°,forming hydrophobic coating.Although the conductivity of graphene(H-G)prepared by HRSM is 300 times higher than that of R-RGO,it has little effect on the anticorrosion performance of the coating,indicating that the conductivity does not play a decisive role in the anticorrosion performance.(3)Then we studied on the dispersing method of graphene powder in waterborne epoxy resin coating.LS can be used as a dispersant to disperse reduced graphene oxide which prepared by rotating packed bed reduction oxide method into a component of waterborne epoxy resin,composite coating that graphene dispersed well can be obtained by utrasonic at 3h.Coating adhesion and hardness tests show that dispersant has no effect on the physical properties of the composite coating.The dispersion effect of LS is better than that of other despersants.The Ecorr of waterborne epoxy composite coating containing 1%graphene powders increased by 57.8%and Icorr reduced by three orders of magnitude.