| Graphene is widely used as a functional filler to improve the compactness of anti-corrosive coatings and hinder the diffusion of the corrosive medium.The environmental protection performance of the anti-corrosive coatings can be effectively improved by reducing the addition amounts of traditional chromate fillers,and theirinternal binding force and toughness can also be enhanced to reduce the risks of cracking,spalling as well as the water penetration.Therefore,according to the basic performance characteristics of rGO and coating,three kinds of nonionic polymer block dispersants(solvation chain were A:70%,B:80%,C:90%)were prepared by polymerization reaction.The epoxy/fluorine-containing coatings were doped and modified.The dispersion of rGO in the epoxy/fluorine-containing coatings and the influence mechanism on the coating performance were studied by scanning,Raman,electrochemical,salt spray corrosion experiments.The main conclusions are as follows:Among the three dispersants,the best candidate was found to be the non-ionic polymer block dispersant B.The number-average molecular weight Mn of B is 2672 and the weight-average molecular weight Mw of B is 3600,the paint fineness was 15?m.Four kinds of dispersants were used to graft the rGO fillers,respectively.When the dispersant B and the rGO filler content were 0.2 wt%,the distribution of the fillers in the anti-corrosive coating was relatively uniform,and the porosity reached the minimum value of 0.18%with a small number of the rGO sheets.The microstructure of the B-rGO-0.2 wt.%modified coating was better because the rGO filers promoted the decrease of porosity,whereae the agglomeration occured when the content of the rGO fillers was further increased.Electrochemical,neutral salt spray test and EDS test of the anti-corrosive coatings prepared with the four kinds of dispersants were carried out.The results showed that the self-corrosion current density of polymer block dispersant B-rGO-0.2 wt.%was the lowest,which was 2.35×10-7A/cm2.The maximum polarization resistance was 22.057 k?,and the maximum impedance modulus at the low-frequency range was 105?·cm-2.The water resistance and high-/low-temperature impact tests of the coatings showed that the modified anti-corrosive coating of B-rGO-0.2 wt.%possessed good water resistance,artificial seawater erosion and high-/low-temperature impact performance.After the tests,the coating surface did not show obvious change,free fromcracking,foaming,peeling and other phenomena.The main reasons are the rGO filler in B-rGO-0.2 wt.%modified anti-corrosion coating was uniformly dispersed without agglomeration,and the rGO fillers partially covered the pores to reduce the porosity in the coating and improve its physical barrier ability.In addition,in the early soaking stage,the corrosive ion Cl-gradually filled the internal pores and the defects of the graphene modified anti-corrosion coating,effectively inhibiting the penetration and diffusion of the corrosive media.As a result,the distribution of the corrosive ions in the coating tended to be stable,slowing down the corrosion of Cl-plasma on the aluminum alloy matrix.The high adhesion and the hardness of the coating was significantly retained,which was also an important factor to improve the corrosion resistance of the anti-corrosive coating.According to the above research,the graphene modified anti-corrosive coatings showed better corrosion resistance,immersion resistance,binding force and other properties than the traditional coatings.The selection of appropriate rGO content and the matching polymer block dispersant can make the more effective disperse,and the performance can be improved by more than 10% compared with the traditional coatings. |
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