Corrosion performance of epoxy coatings modified by nanoparticulate SiO2

Electrochemical impedance spectroscopy (EIS) was employed to investigate the corrosion performance of nanoparticulate SiO₂ modified epoxy coatings on carbon steel in 3.5 wt% NaCl solution, coupled with salt spray test. Capacitance‐gravimetric methods and delamination tests were performed to analyze the water uptake behavior and interface stability against delamination of modified coatings, respectively. Four systems were studied, including a clear coating and three pigmented coatings (with 1, 2, and 3 wt% nanoparticulate SiO₂). The experimental results showed that nanoparticulate SiO₂ particles can improve the anti‐corrosion performance of the coatings and the optimal addition content is 2 wt%. The results obtained with capacitance‐gravimetric measurements showed that the diffusion process of water through epoxy coatings with different pigment volume concentration (PVC) obeyed the second Fick's diffusion law in the initial period. Adding nanoparticulate SiO₂ into epoxy coatings can act effectively. The positive influence is attributed to the reaction between nanoparticles and epoxy resin which is confirmed by FTIR, improving the barrier and dispersion effectiveness of coatings. The negative one is increasing the number of pores in the coatings when the adding amount is beyond the critical PVC.