Corrosion properties of surface-modified AZ91D magnesium alloy

Samples of AZ91D magnesium alloy were dipped into AlCl3–NaCl molten salt at different temperatures between 250 °C and 400 °C for 28800 s. The thickness of the alloying layer is increased with the rise of the treatment temperatures. The coating was mainly composed of Al12Mg17 and Al3Mg2 intermetallic compounds. The corrosion resistance of the coating which is obtained at 300 °C for 28800 s is the best. When the treatment temperature is higher than 300 °C, some cracks developed in the alloying layers. The cracks were resulted from the thermal stress due to the different thermal expansion coefficient of the AZ91D substrate and the alloying coating during the rapid cooling process.