The electrolyte diffusion into the coating/metal interface is responsible for the relative increase of electrochemical active surface area. One way to determine the relative increase of delaminated area is the evaluation of the increase of fb. In fact, the delaminated area of the coating was approximately proportional to fb[43,44]. The increase of fb is indicative of the increase of delaminated area. From the results obtained, it can be seen that the frequency at break increased after 30 days’ immersion and it occurred at higher frequencies for the untreated sample in comparison to the treated samples. This may be attributed to the loss of the barrier properties of the epoxy coating applied on the untreated steel and the electrolyte diffusion to the interface of the metal/coating. The lowest increase of fb was observed for the sample treated by Zn-PVA. These mean that the microscopic delaminated area on this sample is lower than Zn treated one. All of these observations show that addition of PVA to the zinc phosphate solution enhanced the corrosion protection properties of the epoxy coating through enhancing the adhesion properties and decreasing the electrochemical activity of the steel surface.