Preparation And Anticorrosion Study Of Multi-Layer Polymer Coatings Based On Corrosion-Inhibited Polyaniline/Reactive Graphene Oxide

The structural advantages of epoxy resin endow the epoxy resin coating with excellent physical and chemical properties,which makes it occupy a place in the environment-friendly heavy-duty anti-corrosion coating,and is the most widely used coating primer.Aliphatic fluorinecontaining polyurethane is widely used in the outermost layer of coating system due to its strong plasticity,weather resistance,hydrophobicity,high chemical stability and low surface energy.Graphene anti-corrosion coatings are a typical case of the application of two-dimensional nanomaterials in polymer resins.Based on the graphene nanostructure,the nanosheets are uniformly dispersed in the polymer matrix to build a labyrinth in the polymer for the corrosive medium(water,oxygen and electrolyte)to limit the intrusion of the corrosive medium.It is a new type of functional filler.Polyaniline anticorrosion coatings passivate the substrate under the coating through redox,enhance the ability to resist the invasion of corrosive media and improve the anti-corrosion performance.In the field of anticorrosion,a series of problems,such as the dispersion stability of graphene and polyaniline and their derivatives in resin,and the interfacial compatibility between filler and resin,need to be solved urgently.In this study,guided by the above problems,a self-emulsifying waterborne epoxy resin curing agent was synthesized,a waterborne epoxy resin emulsion was obtained by emulsifying epoxy resin E-51,and a fluorine-containing polyurethane emulsion was prepared by synthesizing fluorine-containing monomers.Use functionalized graphene derivatives and poly-o-toluidine microcapsules as functional fillers to develop supporting composite anticorrosion coatings,study the anti-corrosion mechanism of composite anticorrosion coatings,and build anti-corrosion models.The specific research work is as follows:(1)Self-emulsifying water-based epoxy resin curing agent(SWECA)was synthesized using epoxy resin E-51,ethylenediamine(EDA),tetraethylene pentaamine(TEPA),pentaerythritol triacrylate(PETA),hydroxypropyl acrylate(HPA)and o-tolyphenyl glycidyl ether(CGE)as raw materials.SWECA emulsified E-51 to produce aqueous epoxy resin emulsion(WEP)and applied it as a base resin to metal anti-corrosion primers.It was found that different proportions of mixed amines can control the viscosity and curing time of the emulsion.At the same time,by adjusting the ratio of end-capping agent,the emulsifying ability of the curing agent is very different,and the hydrophilic and hydrophobic properties and mechanical properties of the cured coating are changed.The synthetic formulations in this article are[EDA]:[TEPA]=0.15:0.05 and[HPA]:[CGE]=0.02:0.03.The DSC test showed that the epoxy coating combined performance was best obtained by curing at 79℃ for 40 min and then curing at 130℃ for 36 min.And salt spray experimental tests confirmed that it has better corrosion resistance than other samples in the same group.The low-frequency impedance of electrochemical test is 3.150×108Ω·cm2.The application field of the self-emulsifying waterborne epoxy resin curing agent is suitable for low-viscosity epoxy resins represented by epoxy resin E-51.Provided technical support for the design and development of high-performance environmentally friendly epoxy coatings.(2)The anti-corrosion filler(CI@POT)was prepared by coating the corrosion inhibitor with poly-o-toluidine,and dispersed in the water-based epoxy coating to prepare the CI@POT/WEP composite coating.The mechanism of action between poly-o-toluidine capsules coated with corrosion inhibitor and resin in WEP was studied,and an anti-corrosion model was constructed.The results show that the introduction of CI@POT improves the water resistance and shielding performance of the coating;through electrochemical testing(EIS)and corrosion product testing(XRD),it is found that CI@POT can greatly improve the resistance of WEP to corrosion by corrosive media.Restricting the penetration and spread of the corrosion area,the low-frequency impedance reaches 4.670×108Ω·cm2 after being eroded by 3.5%NaCl salt spray for 500 h.Through the electrochemical impedance test of the composite coating after artificial damage,CI@POT/WEP can form a protective film on the damaged part.In addition,the analysis of corrosion products under the coating shows that CI can limit the diffusion of the corrosion area,and the metal under the coating has no serious damage.Corrosion,the corrosion products are onlyγ-Fe2O3 and Fe3O4,and the POT redox effect prolongs the corrosion resistance time of iron-based passivation.(3)Fluorine-containing monomers were prepared by Michael addition reaction by reacting trifluoroethyl methacrylate with polyetheramine at room temperature.Then the fluorine-containing monomer and 1,4butanediol were prepared by orthogonal experiments and single-factor experiments to prepare fluorine-containing polyurethane coatings with excellent performance.The adhesion mechanism of fluorine-containing polyurethane coating as topcoat and epoxy primer and the advantages of supporting anti-corrosion system were studied.The study found that the fluorine-containing polyurethane formed chemical bonds and hydrogen bonds with the epoxy coating through mutual transfer during the curing process,the composite coating was dense,and had excellent mechanical properties and anti-corrosion properties.function,greatly extending the service life of the coating.The results show that:1)When D2000-F:D230F:BDO=2:1:2(wt%),the prepared paint film has the best performance,the water absorption rate for 20 days is 0.30%;the mechanical properties are excellent,and the elongation at break is excellent.%and tensile strength are 69.13%and 25.45 MPa,respectively;2)FPU film has hydrogen bond self-healing ability at room temperature,and the selfhealing performance is obvious,FPU can protect the substrate from corrosion more lastingly as a topcoat;3)By Electrochemical impedance spectroscopy(EIS)test shows that the prepared FPU-WEP composite coating system enhances the defense against corrosion by corrosive media,effectively delays the corrosion of metal substrates,and exhibits good corrosion protection ability.FPU-WEP has the highest low-frequency impedance in the initial state(|Z|f=0.01Hz=2.854×1011Ω·cm2);and after 600 h of salt spray corrosion,its low-frequency impedance value can still maintain 2.530×108Ω·cm2.(4)A highly active acid chloride group was introduced on the surface of graphene oxide by acid chloride reaction,and then reacted with 2amino-4,6-dichloropyrimidine and sodium amide to prepare amine functionalized graphene oxide(AFGO).A uniform AFGO/FPU nanocomposite coating was obtained by mixing AFGO with fluorinecontaining polyurethane through a ball-milling dispersion process.The prepared AFGO utilizes the formed primary amine group to impart covalent bonding between graphene oxide and FPU,and utilizes the formed amide bond to impart hydrogen bonding between graphene oxide and FPU.The study found that AFGO uses covalent bonds to bond with the matrix resin to improve the re-agglomeration phenomenon after the composite of the nano-filler and the resin matrix,significantly enhance the compactness of the nano-composite coating,and greatly improve the barrier properties of the coating.The amine group and amide structure in AFGO can improve the hydrogen bonding between the nanofiller and the resin,which makes the composite emulsion extremely advantageous in terms of dispersion stability and composite coating in terms of mechanical properties,erosion resistance,aging resistance and long-term corrosion resistance.The comparison found that the permeability resistance,small molecule shielding performance,aging resistance and corrosion resistance of AFGO/FPU are much higher than that of graphene oxide/fluorinecontaining polyurethane composite coating(GO/FPU).In addition,after 1800 h of simulated corrosion environment by the salt spray machine,|Z|f=0.01Hz=6.236×109Ω·cm2 of AFGO/FPU-CI@POT/WEP,the corrosion service period is greatly prolonged.The AFGO/FPU composite emulsion designed in this subject is a new type of green anti-aging and anti-corrosion coating,which provides a molecular design idea for the construction of self-crosslinking graphene in resin matrix.