Question

What are the reason of two semicircle in impedance spectra?

Answer 1

Answer:

I know the basics of Electro chemical impedance spectroscopy. I know how to predict the behavior of materials and corrosion rate.

Also,

Semicircle nature of Nyquist plot depends on the equivalent circuit of the electrochemical systems. When your resistor and capacitor are in the parallel arrangement, we will end-up a semicircle Nyquist plot.