Hello, if your sample is passivated during polarization (and with the help of your potentiostat), you will get a passivation peak with a following sudden drop in current (typical for passivation). If your sample does not show this and is still at very low current, you may already have a passive layer on the surface or some other current limiting process. Is this what you meant? Sincerely yours, Andreas

(p.s. in which electrolyte did you perform your experiment? Is the titanium active in this solution or can it passivate itself)

The technical reaseon for the disparity in passivity for high corrosion rate of Titanium with low corrosion rate is that Since titanium depends for its passivity on the presence of an oxide film, it follows that it is significantly more resistant to corrosion in oxidising solutions than in non-oxidising media where high rates of attack can occur.

Dear Dr. Mohabbat Amirnejad,

considering that the experimental set-up, before and during the electrochemical analyzes, was the same for the different samples, I suggest you to have a look at the following interesting application notes, both by Princeton Applied Research:

-Basics of Corrosion Measurements

Available at: https://www.ameteksi.com/-/media/ameteksi/download_links/documentations/library/princetonappliedresearch/application_note_corr-1.pdf?la=en

- Electrochemistry and Corrosion: Overview and Techniques

Available at: https://www.ameteksi.com/-/media/ameteksi/download_links/documentations/library/princetonappliedresearch/application_note_corr-4.pdf?la=en

Best regards, Pierluigi Traverso.

The sample with a higher corrosion rate and a passive region possess higher surface electrochemical reactivity which increases the passivation ability resulting in rapid formation of stable passive film. In this respect the cathodic reaction(s) becomes inhibited and the Ecorr become more negative than Ecorr of the other sample with lower corrosion current density.

Now, surface electrochemical reactivity is a direct function to surface electron activity and the most effective parameter in this function is the grain size.

Best regards