Hybrid Filler Synergy: Engineering Epoxy Composite Coatings with Nano- and Micro-Fillers for Superior Metal Corrosion Protection

Micron-sized hollow microsphere (HMS) fillers in anticorrosion coatings often suffer from inadequate dispersion, limiting their protective performance. Conventional practices such as surface activation (aHMS) and functionalization (sHMS) of HMS have shown limited improvement in dispersion and corrosion resistance. Here we show that, by introducing nanoparticles like TiO2 (MO, ∼21 nm) along with HMS in epoxy composite coating synergistically enhanced barrier property and corrosion protection. After 720 h of exposure to a corrosive environment, coating resistance increased by two orders and protection efficiency by 22% compared to the coatings with single filler (HMS). Further, the composite coatings with silica-modified HMS (sHMS) and stearic acid-modified nanometal oxide (sMO) fillers exhibited no blistering during a 720 h water immersion test, confirming excellent resistance to water diffusion. When nano- and microfillers are used together, the HMS dispersion in the coating matrix significantly improves, demonstrating that varying filler sizes and surface modifications can be an effective strategy to utilize HMS for enhanced corrosion protection.