In this study, the protective performance of zinc chromate at various PVCs (Pigment Volume Concentration = 25,30,35, 40, 45, 50) in epoxy ester resin is evaluated through electrochemical impedance technique. The obtained data is compared with those of routine tests, including, adhesion and salt spray fog chamber. The results show that in electrolyte with 3.5 % sodium chloride content, the values of log Z decrease for the samples exposed to salt spray for 24 hours, compared to the blank, while the behavior of samples exposed to salt spray chamber for two weeks increase it. These findings indicate that the impedance value changes in inverse proportion to the amount of water absorption, dielectric constant, and electrical capacitance of the coating. The results imply that the: best performance of this primer is in the PVC range of 30-40.