Smart corrosion sensing phenanthroline modified alkyd coatings

Alkyd resin was chemically modified with 1,10-phenanthroline-5-amine and characterized by Fourier transform infrared (FTIR) and 13C Nuclear magnetic resonance (13C NMR) spectroscopy. The complex forming ability of phenanthroline modified alkyd resin with Fe2+ ions was studied by UV-Visible spectroscopy. Mixture of Fe2+ solution and modified alkyd resin showed new absorption bands in UV-Visible spectroscopy confirmed the formation of modified alkyd resin-Fe(II) complex. Corrosion sensing property of modified alkyd coating was evaluated by immersing the coated mild steel specimens in 3.5% NaCl solution. Color change was observed in the coating due to onset of corrosion at metal-coating interface. Electrochemical impedance spectroscopy (EIS) was used for correlating the polarization resistance (Rp) of coating with color change. Scanning electron microscopic (SEM) analysis on the surface of metal specimens indicated that the point of color change was the corrosion site. Results revealed that phenanthroline modified alkyd resin can be used in corrosion sensing coating formulations.