Dear Dr. Wan Mohamad Ikhmal ,

I would try with an amplitude of sinusoidal perturbation signal of 5 or 10 mV but I suggest you also to have a look at the following, interesting papers/thesis:

-Study on pitting process of 316L stainless steel by means of staircase potential electrochemical impedance spectroscopy

Zhijun Jia, Cuiwei Du, Cheng-tao Li, Zou Yi, Xiao-gang Li

International Journal of Minerals Metallurgy and Materials, 18(1):48-52 (2011)

Available, on RG, at: https://www.researchgate.net/publication/225481319_Study_on_pitting_process_of_316L_stainless_steel_by_means_of_staircase_potential_electrochemical_impedance_spectroscopy

-Role of Modern Localised Electrochemical Techniques to Evaluate the Corrosion on Heterogeneous Surfaces

R. Leiva-García, R. Sánchez-Tovar, C. Escrivà-Cerdán and J. García- Antón

In Book: Modern Electrochemical Methods in Nano, Surface and Corrosion Science (2014)

Available at: https://www.intechopen.com/books/modern-electrochemical-methods-in-nano-surface-and-corrosion-science/role-of-modern-localised-electrochemical-techniques-to-evaluate-the-corrosion-on-heterogeneous-surfa

-Aciers inoxydableset corrosion localisée: le rôle du molybdène

Thesis of Dr. Thiago José MESQUITA - UNIVERSITÉ DE GRENOBLE (2012)

Available at: https://www.google.it/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjYobKy0r7tAhVLDuwKHYlrDuQ4ChAWMAR6BAgCEAI&url=https%3A%2F%2Fwww.theses.fr%2F2012GRENI006.pdf&usg=AOvVaw0-KXDbUuaYaJ56HGE-pjf9

My best regards, Pierluigi Traverso.

The standard amplitude for EIS is 10 mV (rms), and that should be fine. For the bare sample, you can go smaller if you are having issues with non-linear responses at low frequencies, but I would recommend > 1 mV (rms).

For the coated sample, it depends on the coating, but larger amplitudes can sometimes be used with barrier coatings--if your impedance spectrum is almost all capacitive or has one time constant with the low frequency resistance associated with "pore resistance" then you can use a larger amplitude to improve signal from the high Z sample--up to maybe 50 mV. If you have any electrochemical activity (either the coating itself or the metal under the coating) then you should stay with 10 mV or less.

Dear Dr. Wan Mohamad Ikhmal ,

I would try with an amplitude of sinusoidal perturbation signal of 5 or 10 mV but I suggest you also to have a look at the following, interesting papers/thesis:

-Study on pitting process of 316L stainless steel by means of staircase potential electrochemical impedance spectroscopy

Zhijun Jia, Cuiwei Du, Cheng-tao Li, Zou Yi, Xiao-gang Li

International Journal of Minerals Metallurgy and Materials, 18(1):48-52 (2011)

Available, on RG, at: https://www.researchgate.net/publication/225481319_Study_on_pitting_process_of_316L_stainless_steel_by_means_of_staircase_potential_electrochemical_impedance_spectroscopy

-Role of Modern Localised Electrochemical Techniques to Evaluate the Corrosion on Heterogeneous Surfaces

R. Leiva-García, R. Sánchez-Tovar, C. Escrivà-Cerdán and J. García- Antón

In Book: Modern Electrochemical Methods in Nano, Surface and Corrosion Science (2014)

Available at: https://www.intechopen.com/books/modern-electrochemical-methods-in-nano-surface-and-corrosion-science/role-of-modern-localised-electrochemical-techniques-to-evaluate-the-corrosion-on-heterogeneous-surfa

-Aciers inoxydableset corrosion localisée: le rôle du molybdène

Thesis of Dr. Thiago José MESQUITA - UNIVERSITÉ DE GRENOBLE (2012)

Available at: https://www.google.it/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjYobKy0r7tAhVLDuwKHYlrDuQ4ChAWMAR6BAgCEAI&url=https%3A%2F%2Fwww.theses.fr%2F2012GRENI006.pdf&usg=AOvVaw0-KXDbUuaYaJ56HGE-pjf9

My best regards, Pierluigi Traverso.

Dear Wan Mohamad

+/-5mV would be a suitable amplitude for the coated and bare 316 stainless steel using the EIS.

Thank you so much for the answers everyone. :))

The amplitude of the perturbation signal can be selected experimentally by making measurements at different amplitudes and observing the spectrum obtained. I personally use an amlituda of 20 mV and it is not too high a value. Of course, the research environment should also be taken into account.

stefan

Thank you Prof. Stefan Krakowiak :))