Semiconducting Properties of Passive Films Formed on AISI 420 Stainless Steel in Nitric Acid Solutions

This study focuses on the semiconductor properties of passive films formed on AISI 420 stainless steel immersed in four nitric acid solutions under open circuit potential (OCP) conditions. For this purpose, the passivation parameters and semiconductor properties of passive films were derived from potentiodynamic polarization and Mott–Schottky analysis, respectively. The OCP plots showed that the open circuit potential of AISI 420 stainless steel is directed towards positive amount, which are indicative of the formation of passive film and its role in increasing protectivity with time. The potentiodynamic polarization results showed that the corrosion current density of AISI 420 stainless steel increased with the increase in the concentration of solutions. Mott–Schottky analysis revealed that the existence of a duplex passive film structure composed of two oxide layers of distinct semiconductivities (n-type and p-type). Also, Mott–Schottky analysis indicated that the donor densities are in the range 1021 cm-3 and increased with solution concentration.