In situ observation of formation and spreading of micro-droplets on magnesium and its alloy under cyclic wet–dry conditions

The formation and spreading of micro-droplets on pure magnesium and its alloy in an atmosphere of water vapor under cyclic wet–dry conditions was studied using an environmental scanning electron microscope (ESEM). The in situ observations indicated that the corrosion product stimulated the formation and spreading of micro-droplets, and the grain boundaries for pure magnesium and β phase for AZ91 magnesium alloy had no influences on this process. The oxygen concentration on the surface generally increased with the wetting time. The corrosion products decreased the corrosion rate.