Titanium dioxide/conducting polymers composite pigments for corrosion protection of cold rolled steel

Titanium dioxide (TiO2)/conducting polymers composite pigments were synthesized by chemical oxidative polymerization technique in a simple and eco-friendly manner. These composite pigments were characterized for morphology by scanning electron microscopy and transmission electron microscopy, for conductivity by four point probe and conductive-atomic force microscopy, for elemental composition by X-ray photoelectron spectroscopy, and for chemical composition by Fourier transform infrared spectroscopy. Three different types of composite pigments were synthesized, namely TiO2/polypyrrole composite pigment, TiO2/polypyrrole composite pigment doped with tungstate anion, and TiO2/polyaniline composite pigment. Core and shell morphology was obtained for TiO2/polypyrrole composite pigment and TiO2/polypyrrole composite pigment doped with tungstate anion. Coatings based on these pigments were formulated and applied on a cold rolled steel substrate. Constant immersion in 5% sodium chloride was employed for studying the corrosion resistance offered by composite pigments-based coatings. The corrosion resistance of the coatings was monitored by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization technique. EIS results demonstrated increased corrosion protection for the core and shell TiO2/polypyrrole composite, TiO2/polypyrrole (tungstate doped) composite, and TiO2/polyaniline composite. Additionally, potentiodynamic scan results demonstrated passivation achieved by synthesized composite pigments-based coatings, suggesting improved corrosion protection.