I have conducted EIS tests of two samples and made Nyquist plot. Unfortunately, the plot does not look like typical semicircular type. I want to compare the electrochemical corrosion of two samples. How can I explain the Nyquist plot (attached) in the best possible way with regard to corrosion.
I am thankful in advance.
Dear Zahid Hussain;
The linear graph of the non-anodized sample referring to the increases in the resistance against the passing of the ionic species through the pores of the metal surface/solution interface.
Dear Mahmood H. M.
Thank you for the answer. Can you elaborate your answer a bit more? Do you mean linear graph of sample #1 in attached figure indicates larger resistance?
Thank you very much
Dear Zahid Hussain;
The Nyquist plot contains a semicircle curve with two intersecting points for the real axis (Z’), Values of solution resistance (Rs) obtained from the first intercept point, closer to the origin, and the value of total resistance (Rs+Rct) obtained from the second intercept farthest from the origin point. Simultaneously, the double layer capacitance Cdl is measured from the intermediate frequency from the equation.
Cdl = 1/(ω×Rct),
where ω= 2πf where f is the frequency in Hertz.
The semicircular curve is attributed to the small charge transfer capacity between oxide coating and solution. In contrast, the linear curve of the non-anodized sample refers to the increases in the diffusion of corrosive species through the pores in the metal/solution interface. the straight line indicates a diffusion mechanism of ions through the pores.
I think you have to draw the Bode plots of log impedance modulus (Z) vs. log frequency (f), for the samples to get the values of Rs, Rct, Rp, and Cdl
I suggest changing the scale of your graph maybe you will get a better result.
more details in the following references;
file:///C:/Users/USER/Desktop/2019-H.Herrera_H.-ArabianJOURNAL.pdf
https://www.hindawi.com/journals/ijc/2014/721208/
Article Corrosion Resistance Properties of Aluminum Coating Applied ...
What system are you investigating, any information to help determine what is visible on the spectra :) ???
Dear Mahmood H. M.
Thank you for the answer. The papers you suggested are really helpful, I will go through these and hopefully find the explanation of my data. By the way, Bode plots and potentiodynamic experiments indicate that sample#1 shows more corrosion resistance. In my view, the dimension of semicircle loop can be seen substantially larger than that of sample#2, so I was expecting the increased corrosion resistance of sample#1.
Thank you very much.
Dear Stefan Krakowiak ,
I am investigating the hBN reinforced metal matrix (and not coating). hBN is supposed to be present at the grain boundaries of metal matrix. I want to quantitatively and qualitatively investigate the effect of hBN on the metal matrix.
Thank you.
Dear Dr. Zahid Hussain ,
I suggest you to have a look at the following, interesting documents:
- Basics of Electrochemical Impedance Spectroscopy by Gamry
Available at: https://www.gamry.com/application-notes/EIS/basics-of-electrochemical-impedance-spectroscopy/
- Bode and Nyquist Plot by Palmsense (different chapters are present…)
Available at: https://www.palmsenscorrosion.com/knowledgebase/bode-and-nyquist-plot/
- Physical Interpretations of Nyquist Plots for EDLC Electrodes and Devices
Bing-Ang Mei, Obaidallah Munteshari, Jonathan Lau, Bruce Dunn,and Laurent Pilon
J. Phys. Chem. C, 122, 194-206 (2018)
Available at: https://www.seas.ucla.edu/~pilon/Publications/JPCC2018-interpretation%20EIS.pdf
- Use of Electrochemical Impedance Spectroscopy (EIS) to monitoring the corrosion of reinforced concrete
D.V. RIBEIRO, C.A.C. SOUZA, J.C.C. ABRANTES
BRACON Estrut. Mater., 8 (4) (2015)
Available at: https://www.scielo.br/j/riem/a/3FMqWgfrgzzRxVpRjzchvMD/?lang=en
My best regards, Pierluigi Traverso.
Hello Mr Hussain
Can you add some information to the plot Whats the lowest frequency applied how long does the measurement takes place? I think the sample one is not in a steady state (or the capacitance is not ideal) because it has some "flatened" semicirular shape. At the end of both plots it seems that diffusion dominates (thats why i ask for the frequency range scanned). So the angle of 45° at the end of the plots indicates a Warburg impedance.
- Badges
- Science topic
- Similar topics
- Phytochemistry
- Extracts