Greetings,
I just want to ask a simple question in relates to the coating capacitance. Based on my little bit of understanding, the coating capacitance can be used to quantifies the water uptake by the organic coating especially during its initial exposure to the solution.
It says that, as the water uptake or absorb by the coating increase, the dielectric constant (coating) will increase and the coating capacitance will also increase.
Moreover, through the result we can also know the solubility of the coating. And as the coating thickness increase the water uptake will also increase.
So, my question is, whats more can we know based on coating capacitance? And if theres a major variation in relates to time what does it means?
Thank you.
Dear Wan Mohamad Ikhmal,
some of the contemporary points and issues[1] in your question, on coating capacitance progress, start to have an initiative, but an up-to-date, discussion[2,3].
1. say, 1)larger AC amplitude effects, 2)different quality of coating defects, etc.
2. EIS of Organic Coatings and Paints:How to Measure an Impossible System https://www.gamry.com/application-notes/EIS/eis-of-organic-coatings-and-paints/
3. Water uptake in protective organic coatings and its reflection in measured coating impedance https://www.sciencedirect.com/science/article/pii/S0300944017308342
Dear Dr. Wan Mohamad Ikhmal,
The coating capacitance is one of the most important parameters obtained by EIS measurements for the evaluation the protective properties of organic coatings. Analysing this parameter it is possible to measure the water uptake phenomena (diffusion till saturation and further increase) which are very important in barrier coatings.
The ideal trend described in many cases is not representative of the actual evolution measured on coatings. Often one phase is missing or a reduction of the coating capacitance is measured.
A very interesting paper about this topic, that I allow myself to suggest you, is:
"Organic coating capacitance measurement by EIS: ideal and actual trends"
by F. Deflorian, L. Fedrizzi, S. Rossi, P.L. Bonora
Electrochimica Acta
Volume 44, Issue 24, 31 July 1999, Pages 4243-4249.
Best regards, Pierluigi Traverso
In my opinion the function of coating capacitance change with time of exposure to corrosive environments is a cheap and easy tool to highlight the integrity of the coating system in protecting the metal surface over time.
The high coating integrity comes from proper coating material and proper coating application on metal surface. These factors are highly affecting lifetime and the protective properties of any coating system. Now from this function one can experimentally verify many coating system and rank them based on their integrity and time to failure or establishing this function for field continuous protective performance monitoring of any existing coating system in service.
Best regards
Thank you very much Dr. Ioannis Samaras , Dr. Pierluigi Traverso and Dr. Mohammed Hussein j. H. Al'Atia for the answers and enlightenment :)
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