| It is an economical and effective method to apply antiseptic coating on metal surface to protect metal from corrosion.The common anticorrosive coating is mostly to block,fill and other passive protection way,to prevent the invasion of corrosive medium.However,pores and defects will inevitably occur in the long-term service of the coating,leading to the occurrence of corrosion and the failure of the coating barrier effect.Therefore,it is necessary to study the active and automatic protective coating,and combine the passive isolation,corrosion inhibitor control release,active passivation and corrosion warning effect to effectively improve the anticorrosive efficiency of the coating.In this thesis,8-hydroxyquinoline(8-HQ)was selected as the corrosion inhibitor and the fluorescence probe for corrosion warning.It was loaded into mesoporous nano-silicon dioxide(MSN),and the surface was encapsulated with polyelectrolyte of cationic polyelectrolyte-polyethylenimide(PEI).The MSN/8-HQ/PEI anti-corrosion enhancement component was synthesized.The MSN/8-HQ/PEI/EP composite coating was prepared by adding it to waterborne epoxy resin coating(EP).The control and release effects of MSN/8-HQ/PEI on corrosion inhibitors were studied under different corrosion environments.The automatic corrosion protection and corrosion self-warning characteristics of MSN/8-HQ/PEI/EP composite coating on carbon steel were explored.The main research contents and results are as follows.(1)Based on the preparation of mesoporous nano-silica MSN,the modified MSN/8-HQ composite was prepared by introducing 8-hydroxyquinoline into mesoporous nano-silica by coupling blending method.PEI was deposited on MSN/8-HQ by electrostatic deposition method,and MSN/8-HQ/PEI anti-corrosion enhancement components were prepared.By X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),UV-visible diffuse reflection spectroscopy(UV-vis)and Zeta potential,MSN,MSN/8-HQ and composite MSN/8-HQ/PEI were analyzed and characterized.SEM and TEM analysis showed that MSN was uniform spherical,and 8-HQ particles were loaded in MSN.With the increase of PEI deposition time,the particle size of MSN/8-HQ/PEI increased gradually.FTIR and UV-vis further confirmed that 8-HQ and MSN formed a complex.Through TGA test,the load of 8-HQ in MSN/8-HQ/PEI is27.1wt.%,and the coverage of PEI is about 8.3 wt.%.Zeta potential analysis showed that there was electrostatic adsorption between MSN/8-HQ and PEI.MSN/8-HQ/PEI has good dispersion and stability in epoxy polymer emulsion.(2)The corrosion inhibition effect of 8-HQ on Q235 carbon steel was analyzed by in-situ weightloss method,electrochemical polarization curve and molecular dynamics simulation(MD).The corrosion inhibition efficiency of 8-HQ on Q235 carbon steel reached 99.592% at 150 mg/L,and the corrosion of Q235 in the presence of 8-HQ was significantly inhibited.The MD analysis showed that the 8-HQ molecule had strong chemisoradsorption on the surface of Fe(110).When metal corrosion occurs,the corrosion environment in the microanode region is generally weak acid,while the microcathode region is weak alkaline.Therefore,the p H change in the corrosion environment can be simulated,and the controlled release of corrosion inhibitor by MSN/8-HQ/PEI can be analyzed to determine the automatic corrosion protection effect of the anti-corrosion coating.Based on UV-vis spectrum,the release control performance of 8-HQ and fluorescence characteristics of 8-HQ were analyzed by MSN/8-HQ/PEI anticorrosion enhancement components.When the p H of the corrosion environment is neutral,the release rate of 8-HQ/PEI on MSN/8-HQ/PEI is low.When the p H is acidic or alkaline,the release rate of 8-HQ on MSN/8-HQ/PEI reaches 92.3% and83.1% respectively in 360 min,and the release law is stepped.The results show that MSN/8-HQ/PEI can control the release time of corrosion inhibitor when corrosion occurs,and achieve the purpose of automatic corrosion protection.The results also show that the fluorescence probe 8-HQ can effectively detect the presence of Fe3+ions of carbon steel corrosion products,which provides an experimental basis for the preparation of intelligent coatings with warning characteristics.(3)The MSN/8-HQ/PEI anticorrosive enhancement filler was added to the waterborne epoxy polymer emulsion to make waterborne anticorrosive coating.The coating was coated on Q235 carbon steel with the coating machine to make the epoxy anticorrosive coating.The anticorrosive efficiency,automatic protection and corrosion self-warning behavior of the coating under the condition of accelerated corrosion in the laboratory were studied.It was compared with the blank sample coating,MSN,8-HQ and MSN/8-HQ coating.The stability of composite coating(MSN/8-HQ/PEI-EP)is good.After soaking in salt water for 24 h,there is no change and the adhesion remains above grade 1.The composite coating has good permeability resistance and water resistance.Compared with the control coating,the fracture morphology of 0.3MSN/8-HQ/PEI composite coating shows rough and disordered ductile fracture characteristics,and the compatibility of the composite material MSN/8-HQ/PEI with water-based coatings is good.The addition of MSN/8-HQ/PEI EP coating produced significant fluorescent color development at the early stage of corrosion,and the addition of phenanthroline to the coating showed a red color visible to the naked eye when corrosion was just beginning to occur.The XRD and FT-IR analysis of the corrosion products verified the automatic protection effect of the composite coating.The combination of fluorescence color development,controlled release of 8-HQ inhibitor,automatic passivation and fluorescence color development and o-phenylene color development made the MSN/8-HQ/PEI-EP coating realize the integration of automatic protection and corrosion self-warning.(4)Mechanism analysis shows that MSN filling and blocking,8-HQ corrosion inhibition,PEI p H control release and 8-HQ electrochemical reaction with corrosion to produce the fluorescence effect of corrosion product ions,realized the coordination of MSN/8-HQ/PEI composite coating automatic protection and selfwarning characteristics.The results provide experimental basis and research data for improving the anti-corrosion properties and economic added value of MSN/8-HQ/PEI-EP waterborne coatings and avoiding the corrosion spread of steel matrix. |
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