Effect of Aluminum Content on the Crevice Corrosion Behavior of Magnesium Alloys

In this work, the effect of aluminum content on the crevice corrosion behavior of the magnesium alloys has been investigated. The as-cast AZ31, AM60B and AZ80 alloys were subjected to the crevice corrosion in a freely aerated 3.5 wt.% NaCl solution, and the extent of the damage was quantified using weight loss measurement and 3D surface topography using an optical profilometer. The as-cast AM60B and AZ31 alloys exhibited the lowest and highest crevice corrosion resistances, respectively. The surface investigation using a scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) and analysis of the corrosion products by Raman spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) suggested that the corrosion damage predominantly was primarily a function of the volume fraction and distribution of the Mg 17 Al 12 precipitates. The lower corrosion resistance of the as-cast AM60B alloy (corrosion rate ~ 240 mpy) as compared to the as-cast AZ80 alloys (corrosion rate ~ 60 mpy) was attributed to the combined effect of the reduction in the barrier effect of the Mg 17 Al 12 precipitates due to their discontinuous distribution and increase in the extent of the micro-galvanic effect due to the lower aluminum content in the α -Mg matrix in the AM60B alloy.