Effect of Zinc Powder Reduced Graphene Oxide on the Corrosion Resistance of Waterborne Inorganic Zinc-Rich Coatings

Graphene oxide (GO) is considered an ideal material for applications involving corrosion resistance due to its excellent properties. However, the structure, surface functional groups, and distribution of GO in zinc-rich coatings (ZRCs) have a remarkable influence on coating properties. GO was reduced in a hydrochloric acid environment using spherical zinc powder, and the resulting products were subsequently dried and incorporated into waterborne inorganic ZRCs. Results show that zinc powder effectively reduces oxygen-containing functional groups on the GO surface, and reduced GO (rGO) is deposited on the surface of zinc powder. This improves the electron migration efficiency of rGO and decreases its surface energy. The electrochemical impedance spectroscopy (EIS) and salt spray test results demonstrate that among the coatings, the ZRC containing 0.2 wt.% rGO (40Zn–0.2rGO) exhibits the highest impedance modulus at the low frequency end. Its impedance modulus reaches 1 × 104 Ω∙cm2 after 216 h immersion. Furthermore, 40Zn–0.2rGO exhibits no signs of corrosion at the marked areas even after 216 h of the salt spray test. The good dispersion effect of the added 0.2 wt.% rGO in the coating, coupled with its exceptional electrical conductivity, facilitates the enhanced contribution of zinc powder to cathodic protection, thereby mitigating the matrix erosion caused by corrosive media. Following zinc powder corrosion, the surface of the coating can still be adorned with insoluble corrosion products such as ZnO or Zn5(OH)8Cl2, thereby offering shielding protection to the substrate.