Corrosion Behavior of AZ31B Magnesium Alloy under Thin Electrolyte Layer

Abstract

[Purposes] This work is conducted to gain a deeper understanding of the atmospheric corrosion behavior of magnesium alloys. [Methods] Immersion experiments were taken in thin electrolyte layers (TEL), and electrochemical tests, scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy were used for characterizations. The corrosion behaviors of extruded and cast AZ31B magnesium alloys in 3.5 wt% NaCl TEL and bulk solutions of different thicknesses were investigated. [Results] The results indicate that the corrosion rates of AZ31B magnesium alloys in 3.5 wt% NaCl bulk solution are higher than those in TEL, and the corrosion rate in TEL decreases with decreasing film thickness. Conditions of TEL favor the formation of Mg5(CO3)4(OH)2·5H2O, which enhances the protective ability of the corrosion product film. The corrosion morphology of extruded AZ31B in TEL is uniform corrosion, with an overall increasing trend in corrosion resistance with increasing immersion time, while cast AZ31B exhibits mainly localized corrosion, with a continuous decrease in corrosion resistance with increasing immersion time.