Characterization of films fabricated on AZ31 magnesium alloy by heat treatment and immersion methods
By Jeong, Hyunju; Cho, Jaegdong
Published in Surface and Coatings Technology
2018
Abstract
Thin films were fabricated on the surface of AZ31 magnesium alloy by heat treatment and subsequent immersion in deionized water or a NaOH solution. In this study, dense films were synthesized during the initial stage of immersion by increasing the (OH)? concentration at the interface of the high-temperature substrate and the solution. The surface of the magnesium substrates was covered by dense films aligned with the surface during the initial stages of immersion. The surface features of these films were different from those of the films formed simply by immersion in aqueous solutions. The cross-sectional results showed that the films formed in a NaOH solution with heat treatment were denser than those grown by DI water immersion with heat treatment. The X-ray photoelectron spectroscopy results revealed that the films fabricated by immersing the heat-treated substrates were mostly composed of MgO and Mg(OH)2 in both the outer and inner layers. Potentiodynamic polarization measurements showed that the films formed by the immersion of heat-treated substrates showed passive regions, and hence could act as passive layers. The morphology and structure of the films were observed by field-emission scanning electron microscopy and transmission electron microscopy. The compositions of the films were investigated using scanning transmission electron microscopy-energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Potentiodynamic polarization measurements were conducted to investigate the corrosion behavior of the films.