Calculation of the rate constants of nickel electrodissolution in acid medium from EIS

A kinetic analysis of the electrochemical impedance spectra for nickel electrodissolution in an acid medium based on the characteristic points of the faradaic impedance function has been performed when chloride ions are present in the acid medium. Moreover, the obtained results are compared with the event when chloride ions are not present in the acid medium. Chloride ions cause a decrease in both Gamma(1) and Gamma(2) surface concentration assuming a two consecutive electron transfer mechanisms, Ni(0) --> Ni(I) + e(-) --> Ni(II) + e(-), followed by a dissolution process, Ni(II) --> Ni-aq(2+). An increase of the pH favors the formation of a Ni(OH)(2) passive layer that impedes to distinguish clearly between both electron transfers from electrochemical impedance results.