Preparation And Corrosion Resistance Of Graphene-based Anti-corrosive Coatings

The corrosive environment of the ocean has caused serious corrosion problems to ships and other marine equipments and facilities.It is of great significance to adopt appropriate corrosion control technologies and methods to prevent or slow down corrosion.Paint coating anti-corrosion is a cost-effective and widely used method.Epoxy resin is a commonly used anticorrosive material and has good adhesion to metal surfaces.However,epoxy resin has micropores and defects,and long-term contact with corrosive electrolyte will cause structural damage,which needs to be solved by adding fillers.Graphene has become one of the most promising corrosion-resistant fillers due to its excellent electrical conductivity and mechanical properties,high chemical inertness,and barrier effect to gases and ions.Graphene and graphene oxide(GO)have great development and application potential in the field of composite materials,and have become a research hotspot in recent years.However,due to the nano-size effect and incompatibility with polymers,the agglomeration of graphene and GO in the coating affects the corrosion resistance.Therefore,modifying graphene or GO through covalent or non-covalent modification is the key to achieving enhanced anti-corrosion performance.In this paper,a series of graphene-based composites were designed.Graphene and its derivatives were modified by polymer molecules and functionalized by inorganic nanoparticles to generate graphene-based composites,and their composition,structure and shape were characterized and analyzed by a variety of techniques.In order to improve the pore and defect insufficiencies of epoxy resins themselves,graphenebased composites were added as fillers into epoxy resins to promote the anti-corrosion performance of coatings,and their effects on anticorrosive resistance were tested and analyzed by means of various physiochemical techniques coupled with electrochemical methods.In the first chapter,a polyaniline/expanded graphite/epoxy composite anticorrosive coating was prepared by a polymerization using aniline and expanded graphite as raw materials.Taking the polyaniline/epoxy coating as a control,the electrochemical tests showed that the composite coating had a better anti-corrosion effect,and the long-term effective protection lifetime for the substrate is 63 days,an increase of about 22%.In the second chapter,graphene was modified by a conductive polymer molecule of polyaniline,which was used a raw materials for preparing the polyaniline/graphene/epoxy composite coating.The anti-corrosion performance of the polyaniline/graphene/epoxy composite coating was explored by a variety of testing methods.The results showed that polyaniline and graphene exhibited a synergistic anticorrosion effect.This is due to the good conductivity of polyaniline,which promotes the formation of a passivation film on the surface of the substrate through electrical activity,and meanwhile,the increased conductivity of graphene is conducive to reducing polyaniline,which provides a shielding performance for the entire coating.In the third chapter,the long-term corrosion resistance of graphene-based composite anticorrosive coatings has been further improved.On the basis of the second Chapter,the graphene oxide was modified with cerium oxide to improve the stacking and agglomeration of GO,and then polymerized with aniline.The obtained polyaniline/cerium oxide/graphene oxide composite material was used as a filler to fill into epoxy resin for studying the corrosion resistance of the composite coating.The various characterizations and electrochemical tests showed that the polyaniline/cerium oxide/graphene oxide/epoxy composite coating exhibited a slightly less effect than the polyaniline/graphene/epoxy composite coating in terms of the initial anti-corrosion performance.As the time goes by,the barrier performance of the polyaniline/graphene/epoxy composite coating will decrease,and the corrosive medium will gradually contact the substrate.However,due to the double modification of graphene oxide by polymer molecules and inorganic nano-oxides,the polyaniline/cerium oxide/graphene oxide/epoxy composite coating exhibited a better long-term corrosion resistance.