Passive films growth on different Ni-Cr alloys from the migration of cation vacancies

One of the most popular models taking into account the semiconductive behavior of passive film is the Point Defect Model (PDM) which assumes that growth and breakdown kinetics are mainly governed by the migration of point defects under the high electric field within the film. Based on these PDM approaches and employing electrochemical technics such as a multi-frequency Mott-Schottky analysis, the role of Cr addition in synthetic Nickel-based alloys is investigated in this work. Particular attention is paid to cation vacancy diffusivity and flux. The accuracy of the transport coefficient of point defects as a good parameter for assessing the kinetics of film growth is then debated. Moreover, a beneficial synergic alloying effect on cation vacancy diffusivity for Nickel alloy with 24 wt% Cr is also observed and discussed.