One of the attractive low activation steels is the austenitic Mn-Cr steel from the view point of waste disposal because of few long-lived nuclides. In this paper, three types of Mn-Cr austenitic steels were fabricated by vacuum induction furnace. Then plates with 10 mm thickness were fabricated by hot-rolling. The physical metallurgy of these steels was studied by the corrected Schaeffler diagram, X-ray and electron diffraction patterns. The corrected Schaeffler diagram and X-ray diffraction (XRD) results have shown that the matrix of these steels is a single γ-phase structure. Also, the corrosion behaviour in 0.1M HCl solution was evaluated by open-circuit potential, Tafel polarization, and electrochemical impedance spectroscopy (EIS). The results of Tafel polarization experiments show corrosion current density of all three Cr-Mn steels is in the range of 10-4 A cm-2 which indicates their appropriate resistance in this acidic environment. The Nyquist plots showed that polarization resistance from the first to third Cr-Mn steels decreases. This trend is due to increase in corrosion current density which corresponds to Tafel polarization curves. تفاصيل المقالة

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. تفاصيل المقالة

In this study, electrochemical behaviour of passive films formed on AISI 316L stainless steel (AISI 316L) in three acidic solutions concentrations (0.3, 0.6, and 0.9M HNO3) under open circuit potential conditions were evaluated by potentiodynamic polarization, Mott–Schottky analysis and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization results showed that the corrosion potentials of AISI 316L shift towards positive direction with increase in solution concentration. Also, these results reveal that the corrosion rate of AISI 316L is enhanced in solutions with higher nitric content. Mott–Schottky analysis revealed that passive films behave as p-type and n-type semiconductors at potentials below and above the flat band potential, respectively. Also, Mott–Schottky analysis indicated that the donor and acceptor densities increased with solution concentration. EIS data showed that the equivalent circuit Rs((RctQdl)(RfQf)) by two time constants is applicable. Also, EIS results reveal that the charge transfer resistance and passive film resistance decrease with solution concentration. تفاصيل المقالة