Hi,
I am doing work on corrosion protective coating on mild steel sample, I have extracted EIS data from electrochemical workstation. I am using Zsimpwin software to fit Nyquist and Bode plot to get equivalent circuit. My EIS data is not fitting to simple circuit like RQR, RCR etc but it is well fitted for RQRQR circuit, So I want to Know how to analyse corrosion inhibition action of coating by discussing different circuit elements.
Hi Mahesh
From Bode plot of the bare steel sample and the coated sample, at an angular velocity of w=1 or w=2(Pi) f=1rad/s, the f=[1/(2(3.14))]=0.16 hz, on the x-axis.Try to extend a vertical line from the f=0.16hz to intersect the Bode curve. Then,from the point of intersection, try to extrapolate a tangential line to the Y-axix. At the point of the intersection of the extrapolated line with the y-axis, this represents the absolute values of the A.C.impedance | Z|, the inversed value of |Z|=1/|Z|=Cdl, the double layer capacitance. Since |Z| would be obtained at the open circuit potential of the samples in the solutions, |Z| can be considered the polarization potential of the samples in the solutions. So, thereafter, you can Gary-Stern equation to determine the corrosion rate or corrosion current density of the samples.
Indeed, it is a good review paper.
Also, you can refer to " Basics of Electrochemical Impedance Spectroscopy" y princeton applied technology:(https://www.scribd.com/document/109223656/EIS-Nota-AC-1-EG-G)
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