I am currently testing the corrosion behaviour of some metal based materials. The first behaviour was clear for me (as it expected). After polarizing the sample at a high portential for a long time and repating the potentiodynamic polarization measuments afterward, I got a a potentiodyamic polrization curve ( the I-V curve is attached) that has totally different corroison behaviour with three corrosion potential regions . Does anyone have an interprestion for such a behaviour ?
Dear Dr. Abu Bakr Nassr,
you are looking at an active-passive system that is shifting between these two modes of behavior. After polarizing the sample at a high portential for a long time and repating the potentiodynamic polarization measuments afterward, the surface passive film of your sample probably was in bad conditions and after, during the polarization where you increasing potential scan, you are starting with a surface that is free of a protective passivating film and you get an anodic spike at the potential where the passive film forms. Then, after the surface passivates, you get a "cathodic loop," with two additional zero crossings, due to the fact that the cathodic current is greater on the passivated surface than the anodic current. The 2nd and 3rd zero crossings on increasing potential should correspond to the curvature change and zero crossing on the decreasing potential scan.
A similar behaviour is present in the discussion on RG at: https://www.researchgate.net/post/How_do_I_explain_the_irregularities_in_my_polarization_curve2
Best regards, Pierluigi Traverso
@ Pierluigi Traverso : thank you so much for the useful and clear interpretation. Indeed, your answer will help me to get the right points in understanding my metal system more and more
Dear Abu Bakr Nassr
I agree with Pierluigi Traverso , also see the attached paper where you can see graphical and mathematical explanations of your experiments (see Fig 9).
Dear Branimir N. Grgur , Thank you so much. This articl is really helpful.
Dear Abu Bakr Nassr
See also Fig 5b at:
https://www.palmsenscorrosion.com/knowledgebase/polarization-curves/#processing
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