Corrosion behavior of fine-grained AZ31B magnesium alloy

The corrosion behavior of two fine-grained AZ31B alloys was investigated using immersion test, cyclic neutral-salt spray test and electrochemical analysis, and compared to that of commonly hot-extruded AZ31B and AM60 alloys with coarser grains. The fine-grained AZ31B alloys display a higher corrosion resistance than commonly hot-extruded AZ31B, but their corrosion resistance is inferior to that of AM60 alloy. The corrosion resistance of AZ31B alloy tends to increase as grain size is reduced, probably due to the enhanced passivity of surface oxide film, while the effect of grain size is not as significant as that of chemical compositions.

► The corrosion behavior of two fine-grained AZ31B alloys was investigated.
► Immersion test, cyclic neutral-salt spray test and electrochemical analysis were used.
► The corrosion resistance of AZ31B alloy is improved as average grain size is reduced.
► The enhanced corrosion resistance is ascribed to the enhanced passivity of surface film.