Corrosion performance of waterborne epoxy coatings containing polyethylenimine treated mesoporous-TiO2 nanoparticles on mild steel

Waterborne epoxy coatings were modified by adding mesoporous-TiO₂ nanoparticles (meso-TiO₂). In order to achieve proper dispersion of meso-TiO₂ in the epoxy-based coating and make possible chemical interactions between meso-TiO₂ and polymeric coating, meso-TiO₂ was treated with polyethylenimine (PEI) of various molecular weights. Corrosion performance of mild steel coated specimens was investigated employing electrochemical impedance spectroscopy (EIS) and salt spray test. Coatings with meso-TiO₂/PEI (600 molecular weight) possessed the best corrosion performance among the coating specimens. The EIS results showed that the resistance value of coating with meso-TiO₂/PEI (600 molecular weight) was above 9.87 × 10⁷ Ω cm² which was higher than neat epoxy coating. Possible chemical interactions between polymeric matrix and treated nanoparticles caused high barrier properties and high degree of cross-linking.