why Tafel relationship is dependent on activation control method and not on diffusion control ?
Dear Dr. Osamah Ihsan Ali ,
that numerous reactions involved in corrosion can be described using the Tafel equation makes it feasible, with the basis of the straightforward electrochemical kinetics, to represent mixed potential theory, predicting the corrosion rate and potential according to the kinetics and thermodynamics of all of the reactions taking place on an electrode surface. Generally, Tafel kinetics are an accurate explanation of corrosion kinetics for conditions under which mass transport limitations are not considered, because corrosion conditions usually are removed from the reversible potentials for all the reactions.
In Tafel method, the electrochemistry reaction of the electrode potential determines the rate of the reaction and this process depends on the arrival and supply of electro active species to the electrode - If you have near the interface , electrochemically active species is plenty then the reaction rate is determined by the Electrode potential - this is called activation controlled. If the arrival of the species was slow - the reaction rate was limited by the arrival of the species -in this case, the rate of the reaction was controlled by diffusion- -- the condition was under. diffusion controlled.
For more details please see the following tech-note at: https://www.ameteksi.com/-/media/ameteksi/download_links/documentations/library/princetonappliedresearch/application_note_corr-1.pdf?la=en
Best regards, Pierluigi Traverso
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