Dear all,
I am investigating the corrosion resistance of ceramic coating (deposited by PVD process) on Stainless steel samples using Gamry Instrument with parameters OCP (77.78 mV conducting before tafel curve), then scan rate = 1 mV/s, Potential = -0.5 to 0.5 Vs OCP in 0.5M NaCl environment. During starting of tafel curve, there is overloading error within 3-5 minutes and also coating was seen peeled off at the point of contact/interface between solution and Coating having area .022 cm2.
Kindly suggest the best possible solutions to overcome this problem.
Thank you
Dear Dr. Shashi Kant ,
I suggest you to have a look at the interesting Application Note CORR-1 by Princeton Applied Research, available at:
https://www.ameteksi.com/-/media/ameteksi/download_links/documentations/library/princetonappliedresearch/application_note_corr-1.pdf?revision=72ff248d-93aa-470e-a16b-ea23a8f8148a
My best regards, Pierluigi Traverso.
I suspect you have put a very tight shell that cannot be polarized and the potentiostat is "pumping" the current to impose the desired potential. Then the coating breaks through and, for example, hydrogen may be released on the electrode at high current density. The applied coating is delaminated in this process.
greetings
Stefan
Dear Dr. Pierluigi Traverso , Dr.Stefan Krakowiak
Thank you for your interest and support
Dear Shashi Kant ,
I suggest you to measure the Potential instead of your (quasi-floating[1]) cell voltage. In other words, you must add a third electrode, the RE[2] (reference electrode) in this study, in order to be able to measure the Potential difference (and ECORR[3]) against the RE, and avoid any "coatings' peeled off", due to some possible[4,5] Oxygen Reduction Reaction (ORR) and/or Oxygen Evolution Reaction (OER).
1. Potential difference between two half cells, in: The Cell Potential https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Voltaic_Cells/The_Cell_Potential
2. Reference Electrodes in Metal Corrosion https://www.hindawi.com/journals/ijc/2010/756950/
3. Electrochemical Corrosion Potential https://www.corrosionpedia.com/definition/435/electrochemical-corrosion-potential-ecp
4. Oxygen reduction reaction at rust free iron surface in neutral unbuffered chloride solutions https://www.sciencedirect.com/science/article/abs/pii/S0010938X01000786
5. Effect of cathodic polarisation on the corrosion behaviour of 316L stainless steel under static and dynamic conditions https://biblio.ugent.be/publication/6883768
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