Test panels of aluminum alloy 2024-T3 were painted with isocyanate and isocyanatefree
topcoats and analyzed using electrochemical impedance spectroscopy (EIS). A total of 6
isocyanate-free and 1 isocyanate-containing topcoats were analyzed, both in the non-scribed
and scribed conditions. All test panels were exposed to salt fog for 2000 hours and removed
at specific time intervals for EIS measurements. The EIS characterizations were made in 0.1M
sodium borate. Results suggest that there may be a relationship between the barrier
properties of a topcoat and its resistance to scribe-induced corrosion where topcoats with
relatively lower barrier resistance allow dissolution and transport of inhibitors to the defect site.