Effect of Morphology and Surface Modification of Silica Nanoparticles on the Electrodeposition and Corrosion Behavior of Zinc-Based Nanocomposite Coatings

This study mainly reports on the co-electrodeposition of solid and mesoporous silica (SiO2) particles into zinc-matrix composite coatings. Different morphologies of SiO2 nanoparticles, i.e. solid and mesoporous (MPS), were co-electrodeposited with zinc under different electroplating conditions including nanoparticle concentration and deposition current density and the composite coating micro-hardness, internal microstrain, surface roughness, and corrosion rate were investigated. An optimized electrodeposition condition at a current density of 17.5 A/cm2, and a concentration of silica and/or MPS of 1 g/l was determined. Results reveal that the crystallite size, micro-hardness, internal microstrain, roughness, and corrosion properties depend on the amount of electrodeposited silica and MPS incorporated into the zinc-matrix. It was observed that silica nanoparticles are more difficult to co-deposit than MPS, where they develop rougher surfaces, lower micro-hardness and corrosion resistance. However, composite coatings produced with silica and MPS particles surface-modified by 3-mercaptopropyltrimethoxysilane (MPTMS;-SH) exhibited higher corrosion resistance. It was shown that the corrosion resistance decreases in the order: of Zn-MPS-SH > Zn-SiO2-SH > Zn-MPS > Zn-SiO2.