The present study examined the behavior of zinc-rich paints (ZRP) based on an epoxy binder in 3% sodium chloride (NaCl) solution. The study focused on the effect of some design parameters often considered in paint formulation. The paint thickness, the zinc particle grain size, and the zinc particle distribution in the paint were studied. The study was based mainly on electrochemical impedance spectroscopy (EIS). EIS results were interpreted using a model involving the contact impedance between zinc particles. The contact impedance and electrolyte resistance throughout the coating defined the protective action of ZRP. Based on these two concepts, a practical approach to evaluate ZRP performance was given. This approach, called total film resistance (TFR), can be used for optimization criteria in paint formulation.