For solving the problems of liquid absorbing and plasticization, interface layering, and corrosion below film which epoxy resin coatings often meet in acidic working environments, this research has prepared a reactive fluorosilicon low polymer that can co-solidify with epoxy systems, and systematically studied its adjustment functions on the nano-structure and acid corrosion resistance of the coatings. Through the control of fluorosilicon content, the surface enrichment, size of nano-phase domains, surface energy, crosslinking density, acid absorption, electrochemical response, and failure morphology after immersion have been compared for coatings that have different formulations. Furthermore, quantitative interrelations among structure parameters and long-term impedance holding were established through the utilization of AFM, XPS, DMA, and EIS. The outcomes show that fluorosilicon compositions can form a surface layer with much fluorine and silicon in the curing process, and enhance the diffusion curvature inside the membrane, therefore the 6 wt% formula displays the best comprehensive performance: the water contact angle increased to 112.8°, the surface free energy decreased to 19.6 mN·m-1, acid absorption rate after 30 d decreased to 2.87%, and the apparent diffusion coefficient decreased to 7.6×10-10cm2·s-1; in 0.1 mol·L-1H₂SO₄, its remained at 7.90×106 Ω·cm² after 30 d, the corrosion current density was only 3.92×10⁻⁸A·cm⁻², and the adhesion retention rate reached 86.5%, demonstrating the best overall acid resistance.Mechanism analysis indicates that the enhanced acid resistance stems from the synergistic effects of a stable low-energy surface layer, an appropriate distribution of nanostructures, and a continuous cross-linked network, whereas an excess of fluorosilicon weakens the long-term barrier effect due to coarsening of the phase regions. This study provides a basis and reference for the formulation design and mechanism analysis of epoxy protective coatings in acidic media, which can be directly applied to engineering screening, failure diagnosis, and formulation scaling.
