Preparation Of Functionalized Graphene And Its Application In Anticorrosion Coatings For Waterborne Coatings

Organic coatings are widely used in corrosion protection of metal structures in modern industry.Due to strict regulations on the use of volatile organic compounds(VOC),waterborne coatings have been paid more and more attention in metal protection.Organic coatings usually act as physical barriers to prevent oxygen,water and other corrosive ions from entering the metal surface.However,the two main disadvantages of organic coatings are the permeability and weak adhesion of coatings.In this regard,nano-composite coatings are the most promising method to improve the corrosion resistance of the organic coatings.In order to improve the corrosion resistance of the coatings,graphene and its derivatives were used as nano-fillers in waterborne polyurethane(WPU)to prepare excellent anti-corrosion composite coatings.In this study,graphene oxide(GO)was prepared by improved Hummers method,and GO was modified with phosphoric acid to obtain phosphorylated graphene oxide(PGO).The successfully preparation of PGO was confirmed by FT-IR,Raman spectra and so on.In the electrochemical analysis,PGO enhanced WPU showed good anti-corrosion effect.In order to improve the corrosion assistance of the composite coatings,graphene based polymer nano-composites(PPGO and DPPGO)were synthesized by functionalizing PGO with dodecylbenzenesulfonic acid(DBSA)and polyaniline(PANI).The preparation of PPGO and DPPGO was confirmed by FT-IR,XRD,XPS and so on.0.3 wt%GO,PPGO and DPPGO were added into WPU coating to prepare composite solution.DPPGO has the best compatibility and excellent dispersion in WPU.Different coatings have been tested by electrochemical impedance,water absorption and other tests.The impedance modulus of DPPGO reinforced WPU remained at about10~8Ωafter soaking in 3.5 wt%salt water for 63 days,indicating that DPPGO has the highest anti-corrosion efficiency in WPU compared with GO and PPGO.Finally,the synergistic corrosion mechanism among graphene,phosphate group and PANI in graphene based polymer nano-composites was discussed.A kind of chemical process of GO reduction in WPU matrix was explored by using prepared GO and WPU prepared by self-emulsifying method,and RGO/WPU coating was successfully prepared.The surface of RGO/WPU is smoother than that of GO/WPU coating by SEM,which indicated that RGO has better dispersion and compatibility in polymer.In the EIS analysis,the impedance radius and impedance modulus of RGO/WPU coating are the largest,and the phase angle is also the maximum,which shows good corrosion resistance.