Hydrophilic modification of fluorinated graphene for corrosion protection of waterborne epoxy coatings

Fluorinated graphene has a layered structure and insulating nature, and this physical property can prevent the corrosive agent penetration and reduce galvanic corrosion, which is a new type of anticorrosion filler. However, its superhydrophobicity hinders its use in waterborne coatings. In this paper, fluorinated graphene is changed from hydrophobic to hydrophilic by a simple oxidation and modification. The prepared hydrophilic modified fluorinated graphene oxide (HFGO) has good hydrophilicity and can be uniformly dispersed in waterborne epoxy (WEP). Addition of 0.3 wt% HFGO can achieve the optimum corrosion resistance. HFGO/WEP has the corrosion potential of -224.1 mV, the corrosion current density of 3.45 x 10-12 A/cm2 and a protection efficiency of 99.49% according to the polarization curve. The impedance modulus of HFGO/WEP, based on electrochemical impedance spectroscopy (EIS), can reach 9.67 x 109 Omega & sdot;cm2, and the duration of its resistance to salt spray can reach 336 h. The excellent anticorrosion property mainly because well-dispersed HFGO can effectively slow the infiltration of the corrosive agent by filling the micropores in WEP as well as via the "labyrinth effect". Moreover, when the corrosive agent infiltrates to the metallic base, the insulating property of HFGO reduces galvanic corrosion. Our study provides an effective, simple and low-cost means for hydrophilic modification of fluorinated graphene and its application in waterborne coatings.