Modified graphene oxide/waterborne epoxy composite coating with enhanced corrosion resistance

Waterborne epoxy (WEP) resin is drawing increasing attention due to its environmentally friendly nature. However, its application has been greatly hindered by poor corrosion resistance due to its rich inherent defects. In this work, maleic acid diamine (C4H6N2O2, MAD) modified graphene oxide (M-GO) was designed as the filler, and GO/WEP composite coatings with a high cross-linking degree, improved hydrophobicity, and high barrier properties were prepared. M-GO had a good water dispersibility and high affinity to the resin. The chemical grafting between the amino group of MAD and WEP can improve the degree of chemical cross-linking inside the coating to form a compact structure. Electrochemical impedance spectroscopy (EIS) measurements and salt spray test results indicate that the M-GO/WEP composite coating with 0.3 wt% M-GO has the best anti-corrosion performance. After being immersed in 3.5 wt% NaCl solution for 96 h, the |Z|0.01Hz value of M-GO/WEP composite coating is 1.03 × 108 Ω•cm2, corrosion current density is 0.00040 ɥA/cm2 and the protection efficiency reaches 99.99 %.