Abstract: Al-Mg intermetallic compound coatings were prepared on ZL 102 alloy by arc spraying and thermal diffusion.Their microstructure and corrosion resistance were also analyzed by optical microscopy.The corrosion resistance property of coatings layer was tested by means of electrochemical tests and immersion tests in 5% NaCl.The results showed that after thermal diffusion the distribution of magnesium and aluminum elements was changed to uniform,and the magnesium-rich layer coating film disappeared.The coatings were changed from clear layer of aluminum,magnesium alternating lamellae changed into uniform and continuous distribution.After thermal diffusion a certain amount of Al-Mg intermetallic compound is found in the coating.The Al-Mg intermetallic compound has a low corrosion potential and high corrosion resistance,so it would play an important role in materials protection.