Atmospheric corrosion of two field-exposed AZ31B magnesium alloys with different grain size

A fine-grained AZ31B alloy and a commonly hot-extruded AZ31B alloy with coarser grains were exposed to marine and urban environments for 1 year, and the atmospheric corrosion behavior of the AZ31B alloys was investigated. The fine-grained AZ31B alloy displays slightly higher corrosion resistance than the commonly hot-extruded AZ31B, particularly in urban environment. Magnesium carbonate hydrate and hydromagnesite are principal corrosion products of the two AZ31B alloys in both marine and urban environments. Besides, it is found that Al–Mn intermetallic particles have little influence on the atmospheric corrosion of the AZ31B alloys.

► Two AZ31B alloys were exposed in marine and urban environments for 1 year.
► Grain refinement improves the atmospheric corrosion resistance of AZ31B alloy.
► Corrosion of AZ31B alloys is more severe in marine environment than urban environment.
► Al–Mn intermetallic phase has little influence on the atmospheric corrosion of AZ31B alloy.