Investigation on zinc phosphate effectiveness at different pigment volume concentrations via electrochemical impedance spectroscopy

This research is based on studying corrosion inhibitive effect of zinc phosphate at different pigment volume concentration (PVCs) in epoxy–polyamide system. EIS has been examined at open circuit potential (OCP) after 7 days of immersion in 3.5% NaCl solution to indicate electrochemical properties of epoxy coated mild steel at different levels of pigmentation. Coating capacitance, coating resistance, double layer capacitance and charge transfer resistance have been extracted from fitting of EIS results with an electrical circuit, while impedance magnitude at 100 mHz and phase angle (θ) at 10 kHz have been extracted directly from bode plots. Also OCP behavior was examined. Results showed best performance at PVC = 36.5%.