Abstract: The effect of ceria particles on the corrosion resistance of Mg-rich primer on AZ91D magnesium alloy was studied using the Machu test, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The results show that addition of a small amount of cerium oxide (0.1% , mass fraction) had no effect on the corrosion resistance of the coating, and the addition of excessive particles (3%) reduces the corrosion resistance of the coating. However, addition of 0.5% ceria particles to the Mg-rich primer can significantly improve the protection performance of the primer on AZ91D magnesium alloy. The coating resistance increases and coating capacitance decreases after the addition of ceria particles. Although the addition of ceria does not change the protection mechanisms of the magnesium-rich primer on AZ91D magnesium alloy, the electrochemical activity of the magnesium particles in the primer decreases and the service life of the Mg-rich primer is obviously prolonged. The ceria particles also result in an improved barrier effect. In addition, the presence of ceria particles on the AZ91D alloy surface can increase the corrosion potential and decrease the current density of the alloy, which is beneficial for cathode protection of the pure magnesium particles on the alloy substrate.

Key words: Corrosion resistance, AZ91D magnesium alloy, Mg-rich primer, Ceria, Electrochemical impedance spectroscopy