Nine different coating systems on cold rolled steel were tested by recording EIS-data during immersion in 0.5 N NaCl (open to air). One set of samples tested was in the as-received condition and an artificial defect applied. Another set of samples were tested after 2 year's of outdoor exposure at Cape Canaveral, FL. For this set, the susceptibility to cathodic delamination was also evaluated. The as-received condition samples were tested for 1 year. The sample with an all-latex coating was eliminated from further testing since the coating was so porous that the impedance spectra resembled those usually found for bare steel. In long term testing, alkyd/enamel, alkyd/ enamel Si- alkyd, and the zinc-rich primer/epoxy polyamide/polyurethane coatings were damaged. For set of samples tested for 55 days after being outdoors, the only coating damage detected was the alkyd/enamel Si-alkyd coating. The coating properties degraded faster than the as-received sample, indicating that outdoor exposure had weakend the coating. In the cathodic delamination tests, the largest amount of damage occurred on the other alkyd-based coatings. A theoretical analysis of the impedance of polymer coated steel was performed for the purpose of identifying parameters that could be used in the design of a coating monitor.