For some coating I know we could use borate buffer for EIS evaluation of metal and coated one for comparison. My substrates are carbon steel and brass and I am wondering borate solution might have a inhibitor effect on brass.
I appreciate if you answer my question and give me some references.
Dear Rachel,
could you specify more precisely your experimental set-up ? i have a reasonable expertise in EIS, but have no idea what sol-gel is and what is its purpose. The same goes for borate buffer. Also, what is meant by "inhibitor effect" ? Do you mean that borate solution might increases brass electrode-solution interface resistance ?
With best regards
Petr
Dear Petr,
Thank you for the answer. I am electrochemist, but new in a field of sol-gel coating. I would like to perform three electrode system EIS test to evaluate the coating in compare to bare metal. I need a solution which is not interfering with coating. For example in a case of Al alloy I use borate solution to get the reality of coating behavior. So, after this test I perform EIS in NaCl solution to see the differences.
About the inhibitor effect, your point is correct. I guess it will change the substrate resistivity. I appreciate if you could give me some idea or reference.
Best regards.
Rachel.
Evaluating the sol-gel coating on SS or brass using EIS, standard redox couple like ferri/ferrocyanide would be a good choice. I found a paper (check the link below) where 3.5% NaCl was used as an electrolyte for Cu substrate.
http://www.ijcce.ac.ir/article_23557_fd6dd44635c02be62f0bca1e86572e78.pdf
Dear Rachel,
thank you for some clarifications, but I will be still guessing:
Sol-Gel coating probably inhibits/changes electron transfer across the metal electrode-solution interface.
The EIS proper IS NOT 3-electrode arrangement, it is just that electro-chemists believe that in this way, you can bias independently the two electrodes that one should use for the EIS measurements. This is true only approximately and even this assumption is questionable.
So, I would use well defined one metal electrode -solution-well defined second metal electrode arrangement (this is known as sandwich geometry). If the areas of the electrodes are well defined and the separation of the electrodes is small relative to the square root of the electrodes' area, you get effectively one-dimensional system which is easy to evaluate quantitatively.
The EIS measurements should be (~must be) done in a reasonably wide frequency range (my guess in your case would
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