Preparation of octadecylamine modified SiO₂/silicon-acrylic composite coating and concrete corrosion protection

The phenomenon of chloride ion corrosion in concrete during freeze-thaw cycles was addressed. A silicone-acrylic emulsion (TSA) was synthesized via semi-continuous seeded emulsion polymerization. TES served as the organosilicon monomer, while methyl methacrylate, butyl acrylate, and acrylic acid were used as main raw materials. Nano-SiO₂ was surface-functionalized with octadecylamine (ODA) to prepare modified nanoparticles. Composite coatings were fabricated by physically mixing TSA and ODA-SiO₂. The impact of TES content on TSA emulsion properties was analyzed. The effects of ODA-SiO₂ addition on coating performance, including mechanical strength, hydrophobicity, aging resistance, and corrosion resistancewere examined. The protective mechanisms were also explored. The results indicate that the TSA emulsion prepared with 6wt% TES shows a narrow particle size distribution centered at 122 nm, the glass transition temperature of 4.22°C, and low surface energy. When the ODA-SiO₂ content are 2wt%, the composite coating achieves optimal mechanical properties and the lowest chloride ion penetration of 0.308×10⁻³ mg/(cm²·d). It exhibits high compactness, with the lowest water absorption rate of 3.94%. After application on concrete, the 6h electric flux is 559.44 C. Following 50 freeze-thaw cycles, the concrete demonstrates a compressive strength loss rate of 17.3% and bonding strength of 1.83 MPa, confirming effective corrosion protection for concrete.