Effects of P/B on the properties of anticorrosive coatings with different particle size

The effect of the pigment/binder ratio (P/B) on the corrosion resistance properties of polyurethane paints on carbon steel was investigated by ac impedance techniques. Painted steel electrodes were studied during exposure to 3.5% NaCl solution for up to 1000 h. Two series of polyurethane paints were used: conventional ZnO or nano-ZnO as pigments. The results showed that the corrosion resistance is affected by the P/B ratio, the optimum amount of zinc oxide of conventional zinc oxide (P/B = 1) is more than that of nano-zinc oxide (P/B = 0.3). Therefore, better anticorrosive protection is achieved by the coatings pigmented with nano-ZnO and a lesser amount of nano-ZnO is required.