| Corrosion has caused serious safety hazards,environmental pollution,and huge economic losses for many decades.It is estimated that the annual economic losses caused by corrosion even exceed 3%of global GDP.Applying organic polymeric coating on the surface of metal substrate is a cost-effective and widely-used anti-corrosion method.Organic epoxy coatings are widely used owning to their excellent performance,such as good adhesion on the substrate,high crosslinking density,excellent chemical and weather resistance.But traditional solvent-borne epoxy coatings normally contain high volatile organic compounds（VOCs）,with the increasing awareness of environmental protection,environmentally friendly waterborne epoxy coatings（WEP）have attracted more and more attention.However,micropores and microcracks are generated in the WEP coating because of the evaporation of the water during the curing process,thereby corrosive media can easily penetrate into the metal surface and trigger corrosion.Two-dimensional（2D）nanomaterials have large aspect ratios,excellent water and oxygen barrier properties,ion permeability resistance and chemical stability.As functional fillers combined with polymeric coatings,they can exert their“nano-barrier effect”and build a“labyrinth effect”in the coating to extend the penetration path of the corrosive media,effectively ensuring the long-term corrosion protection of the coating.MXenes,a new type of 2D nanomaterial first discovered in 2011,are transition metal carbides,nitrides or carbonitrides.MXene has high specific surface area,excellent hydrophilicity and abundant surface functional groups.However,the easily aggregation and natural restacking tendency ofMXene in organic polymeric coatings seriously limits its effective barrier and anti-corrosion properties.In this thesis,the surface functionalization ofMXene was carried out by three different methods to improve the dispersibility and interfacial compatibility ofMXene in WEP coatings,thereby enhancing the corrosion resistance of composite WEP coatings,and to explore its mechanism of corrosion resistance enhancement.（1）MXene（Ti3C2Tx）nanosheets were modified by an amino acid（L-Cysteine）to fabricate functionalized MXene（fMX）hybrid material.Results derived from FTIR,XRD,EDS and XPS confirm that L-Cysteine has succeeded in covalently functionalizing MXene’s surface.Later,fMX was introduced into the waterborne epoxy（WEP）coating as fillers,and its anti-corrosion performance was studied through electrochemical impedance spectroscopy and potentiodynamic polarization tests.After being immersed in 3.5 wt.%NaCl solution for30 days,fMX/WEP still maintains a higher impedance modulus at lowest frequency（1.21×10~9Ω·cm~2）and a lower corrosion rate(7.95×10-6 mpy)compared to blank WEP.It is resulted from the well dispersion of fMX nanosheets in WEP matrix as well as the enhanced barrier properties offered by fMX.This chapter provides a promising strategy for green modified MXene to improve the corrosion resistance of the coating.（2）A novel nanofiller,phosphoric acid modified chitosan（mCS）functionalized MXene（fMX）has been successfully constructed and used to endow WEP coatings with brilliant corrosive resistance.Electrochemical results demonstrate the|Z0.01Hz|value for 0.2 wt.%fMX/WEP composite coating（4.73×10~7Ω·cm~2）is more than two orders of magnitude higher than that of the blank WEP（2.09×10~5Ω·cm~2）and the corrosion current density value of 0.2wt.%fMX/WEP maintains above 5.44×10-9 A/cm~2 after soaking in 3.5wt.%NaCl solution for 50 days.It is nearly two orders lower than that of blank WEP(5.23×10-7 A/cm~2).Thus,this novel mCS functionalized MXene can serve as an effective composite nanofiller for preparing MXene-based high-performance anti-corrosive coatings.（3）The MXene-ZrP@PDA heterojunction was fabricated by polydopamine（PDA）in-situ functionalization of a composed ofMXene and exfoliatedα-ZrP（e-ZrP）binary fillers.The morphology,crystal structure composition,and functional groups ofMXene-ZrP@PDA were characterized in detail.Then MXene-ZrP@PDA was introduced into WEP coating to achieve uniform dispersion.EIS and PD measurements were used to evaluate the anticorrosion properties of the composite coatings,and the wear resistance was characterized by the friction test.The corrosion rate ofMX-ZrP/WEP(1.70×10-4 mpy)is one order of magnitude lower than that of blank WEP(1.28×10-3 mpy).Moreover,the wear rate ofMX-ZrP/WEP composite coating decreased by 82.06%compared with blank WEP coating.In sum,the introduction ofMXene-ZrP@PDA can significantly improve the anti-corrosion/anti-wear properties of WEP. |
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