Development of polyaniline/chitosan (PANI/CTS) and TiO2-PANI/CTS nanocomposites as anti-corrosion coatings: Synthesis and characterization

Polyaniline/chitosan (PANI/CTS) and TiO2-PANI/CTS nanocomposites were synthesized via in situ oxidative polymerization and characterized by different spectroscopies techniques. The interaction of PANI with the CTS structure and that of the TiO2 nanoparticles with the PANI/CTS copolymer matrix were confirmed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD) analyses of the synthesized nanocomposites show a crystalline structure like their base materials (CTS, PANI and TiO2). The incorporation of PANI, CTS, and TiO2 in the formation of nanocomposites was confirmed by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). Thermogravimetric and differential scanning calorimetry (TGA and DSC) analyses indicate that the PANI/CTS and TiO2-PANI/CTS nanocomposites present greater resistance to thermal decomposition in relation to the CTS and PANI polymers, as well as the highest glass transition temperature (Tg). The anti-corrosion coatings were made by mixing the polymers and synthesized nanocomposites in an alkyd resin (AR) and deposited on 1018 carbon steel and evaluated in 3.5 wt% NaCl solution by linear polarization and electrochemical impedance spectroscopy (EIS) techniques. The best performance against corrosion was observed for the coating made from TiO2-PANI/CTS, since it shows the noblest values in potential, as well as the highest protection efficiencies, even after its immersion for 30 days, which is attributed to the high degree of cross-linking that the nanocomposite has, forming a dense protective film on the steel surface.