Preparation of Zn5Mo2O11·5H2O@Sulfonated Graphene by Template Method and Its Anticorrosion Mechanism in Polyurethane Coatings

Currently, waterborne coatings are widely used, but their poor anticorrosion performance compared with solvent-based coatings hinders their further application. In this study, a series of Zn5Mo2O11·5H2O@sulfonated graphene (SZMO@SG) composites are prepared using the template method. SZMO@SG is a type of two-dimensional material with a large diameter and low thickness compared to traditional zinc molybdate. Combining SZMO@SG with waterborne hydroxy acrylic latex and isocyanate, the polyurethane coatings with 3 wt% SZMO@SG achieve the best anticorrosion performance in the 3.5 wt% NaCl immersion test. In electrochemical impedance spectroscopy (EIS), the charge transfer resistance (Rct) of polyurethane coatings with 3 wt% SZMO@SG reaches 283,100 Ω·cm2 after soaking in a 3.5 wt% NaCl solution for 48 h. Its corrosion potential and corrosion current are only −0.453 V and 1.71 × 10−3 mA/cm2, respectively. After metal substrate corrosion, the metal substrate of polyurethane coatings with SZMO@SG contain more Mo, Zn and low-state Fe atoms. It confirms that a passivation film was deposited on the metal substrate and prevents Fe from oxidation. The elemental content and distribution of the coatings after the NaCl solution immersion test indicate that SZMO@SG may have the Na+ adsorption function.