The coating system containing various sizes (similar to 10, 50, 100, 150 nm) of nano-TiO2 were prepared and investigated for corrosion protection of carbon steel in 1.0 M H2SO4 using polarization, EIS and transmission electron microscopy (TEM) techniques. It was found that nano-TiO2 particles improved the corrosion resistance of alkyd coatings. The corrosion resistance occurs via physical adhesion on the metal surface. O-2 and H2O permeability of coating decreased with decrease in the nano-TiO2 size. The inhibition efficiency was found to increase with decreasing the size of nano-TiO2 and with decreasing the temperature. (C) 2014 Elsevier B.V. All rights reserved.