Study of ceramic-like aluminum oxide thin films developed using plasma electrolytic oxidation applied on austenitic steels

Austenitic steels 304L and 316L are used extensively as nuclear structural materials. The objective of this study is to determine if their corrosion behavior can be improved by developing an Al-containing surface layer by a complex surface treatment, including substrate modification by growth of oxide layers using anodic oxidation, cyclic voltammetry and autoclaving in water, as well as a micro-arc oxidation (MAO) treatment in 0.1M NaAlO2 aqueous solution. The processes and structures obtained by MAO under various experimental conditions were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectrometry analysis. The corrosion behavior, studied by Tafel potentiodynamic polarization, was correlated to the microstructure and the chemical composition of the surface layers which are strongly dependent on the treatment parameters. An overall description of the electrochemical processes involved in the growth of aluminum coating, the surface properties improvement, together with some consideration about the new materials development for energy technologies are presented. Copyright (c) 2016 John Wiley & Sons, Ltd.