Corrosion behavior of melt-spun Mg65Ni20Nd15 and Mg65Cu25Y10 metallic glasses

Abstract

The corrosion characteristics of melt-spun metallic glasses Mg-Ni and Mg-Cu with and without Nd and Y addition in 0.01 M NaCl (pH 12) electrolyte were studied by hydrogen evolution testing and potentiodynamic polarization methods. Both the dissolution rate and corrosion current density of ternary Mg65Ni20Nd15 and Mg65Cu25Y10 were found to be lower than those of binary Mg82Ni18 and Mg79Cu21 alloys. Potentiostatically formed surface layers on Mg65Ni20Nd15 and Mg65Cu25Y10 were characterized with depth profile X-ray photoelectron spectroscopy (DP-XPS). The native and breakdown films were also characterized for comparison. For both Mg65Ni20Nd15 and Mg65Cu25Y10, it revealed that both the surface products of the native and passive films consisted of oxide species of all metallic elements and the depth distributions of oxide species were same: MgO was enriched at the outer region while NiO or CuO was depleted throughout the whole layer; Nd2O3 and Y2O3 were depleted in the outer region and then enriched in the inner region. The breakdown films consisted of the mixture of oxides and hydroxides, mainly of Mg(OH)2. The incorporation of NiO and Nd2O3 (for Mg65Ni20Nd15) and CuO and Y2O3 (for Mg65Cu25Y10), especially the rare earth (RE) oxides, in the passive layers has a beneficial effect to improve the corrosion resistance while their hydroxidation leads to the passivity breakdown. © 2003 Elsevier Science Ltd. All rights reserved.