In literature I have seen people carried out polarizarion tests at a certain potential range (-250 mV to + 250 mV) vs Eocp or vs Ref electrode. Which one is the correct method?
Dear Dr. Sana Mirza ,
the Open Circuit Potential (OCP) is the potential established between the working electrode (the metallic surface to be studied) and the environment, with respect to a reference electrode, which will be placed in the electrolyte close to the working electrode.
Generally, the Potentiodynamic and Cyclic Polarization Scans (anodic and cathodic) start when OCP is stable, from this potential or very near (for anodic scan, researchers often start slightly cathodic of the open-circuit potential, and for a cathodic scan, the starting point is often slightly anodic).
For more details you can see:
-Potentiodynamic and Cyclic Polarization Scans by Gamry
Available at: https://www.gamry.com/application-notes/corrosion-coatings/potentiodynamic-cyclic-polarization/
This is if you want to make two polarization curves, eg. for the calculation of the i corr and the E corr using the Tafel method.
Personally, many times working by comparison between different samples, I perform only a single scan, starting from a hundred mV below the OCP and scanning in the anodic direction for a few hundred mV.
This allows me, with a single polarization curve, to evaluate both the i corr and the Ecorr and subsequently follow the formation and rupture trend of the passive film.
My best regards, Pierluigi Traverso.
Normally, a potential range of -250 mV to + 250 mV is used in polarization curves for Tafel analysis. In that case, the value are referred to the OCP, i.e., we are studying a potential window around this potential.
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering
- Electrodes