Preparation Of Graphene Dispersion With High Solid Content And Good Dispersibility And Its Application In Anticorrosive Waterborne Coatings

In this paper,an easy,green,non-covalent surface modification of graphene(GR)was carried out using a single-step method between sodium carboxymethyl cellulose(CMC)modifier and graphene,resulting in the formation of modified CMC-GR(CGR)dispersion with 15%nanosheets content.The stability,dispersibility and microstructure of graphene dispersion CGR was tested and characterized,and then the best graphene dispersion CGR was used to prepare anticorrosive waterborne coatings with excellent corrosion resistance.First of all,results obtained from thermogravimetry analysis(TGA),Raman spectroscopy,and atomic force microscopy(AFM)confirm that CMC modifier was successfully decorated on the surface of graphene.Then,the modified graphene dispersion CGR was shown to be highly well-dispersed by using transmission spectroscopy,zeta potential analyzer,and transmission electron microscopy(TEM).More importantly,the unmodified graphene is insoluble,while modified CGR-2mixed with 0.9 wt%CMC modifier has the smallest effective diameter and modified CGR-3 mixed with 1.1 wt%CMC modifier correspondingly can be easily well-dispersed in water and has good flowability,and no sedimentation is observed more than 3 months.The anticorrosive waterborne coatings WEP-GR was obtained by mixing graphene dispersion CGR and waterborne epoxy coatings,and the testings of two parts have been done.Firstly,the water resistance and alkali resistance of WEP-GR were tested.The results show that the modified water-based anti-corrosion coating has good water resistance and alkali resistance owing to dispersed graphene nanosheets,which can form a physical shielding layer in matrix to block the penetration of corrosive media such as water,oxygen and salt ions.Secondly,the anticorrosive performance of the modified WEP-GR was mainly studied by using electrochemical and neutral salt spray.The analysis of electrochemical impedance spectroscopy shows that the corrosion resistance of the modified coating WEP-GR0.2 mixed with 0.2wt%graphene reaches the best,and its low frequency impedance reaches 2.001×10⁹?after being immersed in salt water for 28 days,2 to 3 orders of magnitude higher than other coatings.The fitting results of Tafel curve reveals that the corrosion potential of WEP-GR0.2 is the highest at 0.505V,and the corrosion current density is the smallest at 5.68×10^-6?A·cm-2.After 300h of salt spray test,the anti-corrosion of the WEP-GR0.2 coating is the best,indicating that the WEP-GR0.2 coating has the best corrosion resistance.