Corrosion of metal products can seriously affect their reliability. The application of coatings is the most widely used method of corrosion protection due to the desire for easy application and low cost. Most of the present corrosion-resistant coatings are solvent coatings. Due to the high content of volatile organic compounds, the use of solvent coatings is restricted. Currently, the corrosion resistance of waterborne coatings is much lower than that of solvent coatings, so research and development of waterborne corrosion-resistant coatings are necessary and valuable. A corrosion-resistant waterborne polyurethane modified epoxy (WPUME) emulsion was prepared and characterized by Fourier transform infrared (FTIR) spectra, transmission electron microscopy, and thermal gravimetric analysis. The particle size, dispersion, and solid content of the emulsion were tested by laser-scattering equipment and a weighing method. Coatings were prepared based on the emulsion, and the properties (i.e., water absorption rate, salt spray resistance, and flexibility) of the coatings were tested by the standard method, respectively. Results show that the synthesis reaction accords well with the molecule design, and the average diameter of the particles in the emulsion is 100 nm approximately. The cured coating, which is coated on tinplate sheets, has good flexibility and can withstand the salt spray test for more than 60 days (i.e., 1,440 h). The emulsion has many potential practical applications in the protection of metal materials.

Conventional waterborne polyurethane (WPU) has poor water resistance and poor overall performance, which limits its application in outdoor coatings. A solution to this problem is urgently needed. The introduction of fluorine-containing groups can effectively improve the water resistance of WPU. In this study, a new fluorinated chain extender (HFBMA-HPA) synthesized by free radical copolymerization and epoxy resin (E-44) were used to co-modify WPU, and five waterborne fluorinated polyurethane (WFPU) emulsions with different fluorine contents were prepared by the self-emulsification method. The effects of HFBMA-HPA content on the emulsion particle properties, coating surface properties, mechanical properties, water resistance, thermal stability, and corrosion resistance were investigated. The results showed that the WFPU coating had excellent thermal stability, corrosion resistance, and mechanical properties. As the content of HFBMA-HPA increased from 0 wt% to 14 wt%, the water resistance of the WFPU coating gradually increased, the water contact angle (WCA) increased from 73° to 98°, the water absorption decreased from 7.847% to 3.062%, and the surface energy decreased from 32.8 mN/m to 22.6 mN/m. The coatings also showed impressive performances in the adhesion and flexibility tests in extreme conditions. This study provides a waterborne fluorinated polyurethane material with excellent comprehensive performance that has potential application value in the field of outdoor waterproof and anticorrosion coatings.