Effect of Al addition on corrosion behavior of high-purity Mg in terms of processing history

Abstract

In this study, the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history. The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure, including the β phase and Al-Mn or Al-Fe phases, and the protectiveness of the surface film according to the Al content and processing history. In the as-cast alloys, the corrosion rate increased due to the increase of β phase as the Al content increased, but in the as-extruded alloys, the corrosion rate, which was high due to intermetallic compounds caused by impurities in the low Al alloy, decreased as the Al content increased, and then increased again. This is due to the combined effect of the increase of the β phase and decrease of the impurity effect, and the increase of the dissolved Al content. The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.

Keywords

• Mg
• High purity
• Mg-Al alloys
• Processing history
• Micro-galvanic
• Surface film