Damage resistance and anticorrosion properties of nanosilica-filled epoxy-resin composite coatings

Silica nanoparticles surface-capped with diglycidyl ether of bisphenol A were dispersed in a solution of epoxy resin, hardener and acetone. The resultant suspension was then coated onto the surface of duplex stainless steel of type DSS 2205 and cured with temperature, generating a 50 μm thick silica/epoxy coating. Epoxy coating without nanosilica was also prepared as a reference in the same manner. Mechanical properties of these coatings were compared and characterized using the Vickers hardness test. Three-point bending test was performed in combination with acoustic emission to analyze the damage initiation and development in the coating. The effects of incorporating the silica particles on the surface characteristics and the corrosion resistance of the epoxy-coated steel were investigated with contact-angle and surface energy as well as by potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5 wt.% NaCl solution. Results indicate, that silica particles significantly improved the microstructure of the coating matrix, which was reflected in an increased damage resistance, reduced degree of delamination, increased surface roughness and induced hydrophobicity. The silica/epoxy coating was proven to serve as a successful barrier in a chloride-ion-rich environment with an enhanced anticorrosive performance, which was confirmed by the reduced corrosion rate.