Graphene oxide (GO) prepared by a modified Hummers method was reduced by NaBH4 at room temperature for 12 h in a 0.5 mg/mL GO water suspension to obtain reduced GO (RGO), using CaCl2 as a catalyst. The GO and RGO were characterized by XPS, FT-IR, UV-Vis and electrical resistivity measurements. Results show that CaCl2 improves the reduction ability of NaBH4 for oxygen-containing functional groups onthe GO. After reduction, the C/O atomic ratio increased, most of the oxygen-containing functional groupswere eliminated, and the electrical resistance decreased significantly. The highest C/O atomic ratio was 5.38 and the lowest electrical resistance of RGO was 18.6 kΩ/sq, the latter being about two orders of magnitudes lower than the RGO prepared without CaCl2. This reduction method opens a possibility of reducing GO under ambient conditions without using a toxic/corrosive reducing agent and an organic solvent.

Graphene reinforced waterborne polyurethane (PU) composite coatings were fabricated on steel surfaces. When the filler content was 0.4 wt%, self-alignment of graphene was driven by the reduction of the total excluded volume. The superior anticorrosion properties were proven by electrochemical impedance spectroscopy (EIS) analysis for the PU matrix composite coating reinforced by 0.4 wt% of aligned graphene. The interaction mechanism between electrolyte and graphene layers was discussed for the three-dimensional randomly distributed graphene and the in-plane aligned graphene, respectively, to better understand their effects as anticorrosive barriers.

Graphene reinforced waterborne polyurethane (PU) composite coatings were fabricated on steel surfaces. When the filler content was 0.4 wt%, self-alignment of graphene was driven by the reduction of the total excluded volume. The superior anticorrosion properties were proven by electrochemical impedance spectroscopy (EIS) analysis for the PU matrix composite coating reinforced by 0.4 wt% of aligned graphene. The interaction mechanism between electrolyte and graphene layers was discussed for the three-dimensional randomly distributed graphene and the in-plane aligned graphene, respectively, to better understand their effects as anticorrosive barriers.