Enhancement of the erosion-corrosion resistance of Dacromet with hybrid SiO2 sol-gel

A hybrid SiO2 gel/Dacromet composite coating system was designed and prepared by brushing technique from nano-scale organofunctional silica sol on Dacromet-coated carbon steel to enhance the erosion-corrosion resistance of the Dacromet. This particular silica sol was synthesized by the acid catalyzed hydrolysis with TEOS (tetraethoxysilane) and gamma-MAPTS (gamma-Methacryloxypropyltrimethoxysilane) in an ethanol medium. The silica particles showed a characteristic shape due to the intertwisting of the organic chain. The hybrid SiO2 gel/Dacromet composite coating system exhibited a mass loss rate with 4.5 times lower than that of single Dacromet in the simplified industrial medium (3.5% NaCl, 35 wt.% sand and distilled water). A crack-free surface was observed for the hybrid SiO2 gel/Dacromet system due to the incorporation of an organic group during the preparation process so as to produce a restrained synergistic effect of erosion and corrosion. The nano-particles in SiO2 sols did enter into the micro-defects of Dacromet as confirmed by SEM. The change in IR spectra indicated a chemical covalent bond between the gel film and Dacromet through certain reactions. The electrochemical measurement showed that the composite system also presented a longer controlled cathodic protection than that of Dacromet and an enhanced corrosion resistance for Dacromet.