On the Choice of an Equivalent Circuit for the Description of Electrochemical Impedance Spectra of Zn-Filled Polymer Primers and Coatings

The results of a study of the impedance and electrochemical properties of Zn-filled primers applied on different metal substrates for a wide range of exposure times to aggressive media have been reviewed. The correctness of the description of the electrochemical impedance spectra within the most common equivalent electric circuits is analyzed. It is shown that the most correct description of the results of electrochemical impedance spectroscopy over wide time (up to 300 days) and frequency (from 10–2 to 105 Hz) ranges in most cases is achieved for coatings with different content of Zn filler applied on different substrates (Pt, steel, and Zn) by using a hybrid seven-component series-parallel circuit on the basis of R, C, and W components, which makes it possible to avoid the use of constant phase components.