Structural characterization and corrosion performance of acrylic/silica nanocomposite coatings

Acrylic coatings based on Paraloid B72 were modified by adding silica nanoparticles to obtain transparent، non-yellowing and chemically stable coatings، having also good corrosion resistance. CK60 steel sheets were used as substrates. Morphologies and cross-sections of the films were investigated using scanning electron microscope (SEM). The distribution of the silica nanoparticles in the acrylic resin was studied by transmission electron microscopy technique. Atomic force microscopy (AFM) was also used to evaluate the topography and surface roughness of the coatings. The effects of the incorporation of the silica nanoparticles on the corrosion behavior of the acrylic coatings were elucidated using potentiodynamic polarization، electrochemical impedance spectroscopy (EIS) and salt spray tests in 3. 5 wt. % NaCl solution at room temperature. Micro-structural studies indicate that silica nanoparticles were homogeneously dispersed thorough the polymeric matrix. The results of the electrochemical measurements showed that the corrosion protection performance of the acrylic coating was strongly affected in the presence of the silica nanoparticles، and indicate that the nanocomposite coating modified with SiO2 nanoparticles has better corrosion resistance in comparison with its net counterpart. This fact can be mainly attributed to the increased density of the coating and also to the decreased diffusion paths of the aggressive ions from the electrolyte into the coating.