On the Limits of the EIS Low-Frequency Impedance Modulus as a Tool to Describe the Protection Properties of Organic Coatings Exposed to Accelerated Aging Tests

This study analyzes the limitations of low-frequency EIS impedance modulus as a tool to describe protective properties organic coatings subjected accelerated aging tests. Acrylic clear-coated steel and hot-dip galvanized were exposed test methods such neutral salt spray chamber Prohesion for up 2000 3000 h, respectively. During exposure, monitored by visual inspection. We observed significant discrepancy between measured in low frequency range (|Z0.01Hz|), actual deterioration metal–paint interface. The degradation two painted substrates is independent considered. |Z0.01Hz| values do not represent state metal–polymer manuscript discusses reasons lack agreement using are highlighted, several cautions interpreting raw data suggested. reliability possible thresholds (e.g., failure below 106 ohm∙cm2) define performance coating turned out be misleading.