Hello everyone...
Please, in electrochemical corrosion studies, what can explain the variation between the open circuit potential obtain during chronopotentiometry measurement and the corrosion potential obtain on the polarization curves ?
Thank you in advance..
Dear Dr. Odilon R. Wamba-Tchio ,
I answer your question hoping to have interpreted it correctly.
The measurement of open circuit potential (OCP) as a function of time shows how stable our sample is in the corrosive solution. We can have different trends; generally it is preferable to have a constant OCP (no particular corrosive attacks occur on our sample) while in the case of strongly oscillating trends we could be in the presence of a highly unstable electrode and subject to localized corrosion phenomena.
The corrosion potential (Ecorr) instead obtained from the potentiodynamic polarization curves and is instead a given result of an anodic and a cathodic branch and is obtained at the intersection of the Tafel lines, from which it is obtained together with the corrosion current (Icorr) which gives us a useful indication of the corrosion tendency of the sample examined.
For more details, please see:
-Review of the Electrochemical Basis of Corrosion by Gamry
Available at: https://www.gamry.com/application-notes/corrosion-coatings/basics-of-electrochemical-corrosion-measurements/
My best regards, Pierluigi Traverso.
Dear Odilon
In the first case you measure the OCP directly ,i.e., no current in the electrochemical cell.
However, and in the second case,you estimate the OCP from the polarization curves,which is subjected to a number of pparameters,i.e., applied potential, current acquission, time of the polarization test, IR drop due to the ionic solution resistance, and so on.
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