With the help of scanning electron microscopy

energy spectrum analysis and X-ray diffraction

the microstructure of intermetallic compounds layer formed during AZ91 Dalloy surface thermal diffusion in the ZnCl2-NaCl low temperature molten salt system was observed

and effects of intermetallic compounds layer on the corrosion resistance of alloy were examined by using polarization curve test.Results show that at diffusion treatment temperature of 325 ℃ and diffusion treatment time of 9

12 and 15h

respectively

the corresponding average thickness of AZ91 Dalloy surface thermal diffusion layer reaches7.7、8.4and 14.7μm

respectively.Surface diffusion layers are mainly composed ofφ-（Mg11Al5Zn4）

τ-Mg32（Al

Zn）49intermetallic compounds with the diffusion treatment time from 9h to 12 h

while the diffusion treatment time is increased to 15 h

it consists ofτ-Mg32（Al

Zn）49intermetallic compounds.The thermal diffusion layer of alloy surface can obviously improve the corrosion resistance of alloy.