INVESTIGATION ON PERFORMANCE OF EPOXY COATED STEELS WITH NANO-SIO2 AND POLYANILINE COMPOSITE USING COMPLEX IMPEDANCE SPECTROSCOPY

Abstract

This study was conducted to characterize an anti-corrosive epoxy coating for steel with Nano-SiO₂-Polyaniline (PANI) composites using low impedance spectroscopy. The epoxy coating was modified using a varying concentration of nano-filler combination. Coated steels were dipped in 3.5 wt% NaCl solution to induce corrosion. Impedances were measured from 20 Hz to 20 MHz. The electrical characterization was related to the coating performance of epoxy coating with varying concentration. The Nyquist and Bode plots were displayed and related to the graphs with the coating resistance and capacitance. Based on Nyquist plots, 40-60% combination of Nano-SiO₂ and PANI has the largest semi-circle curve, while on Bode plots, still, the 40-60% combination has the largest magnitude of impedance and phase angles. Equivalent circuit model was fitted to measure directly the coating resistance and coating capacitance of the coated steel. Based on the equivalent circuit model, the 40-60% of Nano-SiO₂ to PANI combination had the highest coating resistance equal to 9.50E7 ohms, and lowest coating capacitance of 2.0E-12 Farads. The results presented that all combinations have better corrosion protection performance compared to that of pure epoxy coated steel.