When I use the Gamry Echem Analyst to analyze corrosion, I frequently receive "The difference between Ecoc and Ecorr is large" warning. Even though there isn't much of a difference, the chi-squared value is also relatively low.
It would be beneficial if the scientific community could assist me in addressing this issue and why it is occurring.
Dear Dr. Prabhakar Kumar Singh ,
I suggest you to have a look at the Gamry Application Note "Getting Started with Electrochemical Corrosion Measurement" which should clarify your doubts related to the warning message that is displayed to you.
This document is available at: https://www.gamry.com/assets/Application-Notes/Getting-Started-with-Electrochemical-Corrosion-Measurement.pdf
My best regards, Pierluigi Traverso.
Before starting the Tafel measurement, the open system potential is measured. From this potential, the system is polarized by -0.25 V (cathode polarization). Then the potential is changed towards anode potentials of 0.25 vs Eoc. During the measurement, the corrosion potential of the tested system is determined. In some cases (unstable system, changing significantly during cathodic polarization) there is a difference between the two values. And a "disturbing" message appears.
stefan
Thank you Stefan Krakowiak sir. Is there a special purpose for selecting 0.25v, sir? How do we ensure that we are not ignoring the pitting effect, which may occur if we exceed a particular voltage?
For example, some standards recommend this level of polarization with respect to the Eoc potential. Then we certainly obtain rectilinear sections, characteristic of the Tafel method (at least we should get :)). If in this potential range the sample is already subject to pitting corrosion, it is safer to use linear polarization to assess the corrosion rate.In fact, I probably once happened to exceed the pitting corrosion potential (Enp) during the test using the Tafel method.
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