Corrosion protection of magnesium alloys anode by cerium-based anodization coating in magnesium-air battery

Abstract

CeN3O9·6H2O (0.5, 1.0, 1.5, and 2.0 g/L) was added into an 8.0% NaCl electrolyte solution to investigate this electrolyte for use in a Mg-air battery. The effects of the amount of CeN3O9·6H2O on the corrosion resistance of an AZ31 Mg alloy anode and battery performance were investigated using microstructure, electrochemical (dynamic potential polarization method and electrochemical impedance spectroscopy), and battery measurements. The results show that the addition of CeN3O9·6H2O to the electrolyte leads to the formation of a Ce(OH)3 protective film on the surface of the AZ31 Mg alloy that improves the corrosion resistance of the Mg alloy. An increase in the concentration of CeN3O9·6H2O results in a denser Ce(OH)3 protective film and decreases corrosion rate of the AZ31 Mg alloy. When the concentration of CeN3O9·6H2O is 1.0 g/L, the corrosion rate of the Mg alloy is the lowest with a corrosion inhibition rate of 70.4%. However, the corrosion rate increases due to the dissolution of the Ce(OH)3 protective film when the concentration of CeN3O9·6H2O is greater than 1.0 g/L. Immersing the Mg alloy in the electrolyte solution containing CeN3O9·6H2O for 50 h leads to the formation of the Ce(HO)3 protective film on its surface, which was confirmed by scanning electron microscopy of the AZ31 alloy. The Mg2+ charge transfer resistance increases by 69.5 Ω from the equivalent circuit diagram, which improves the corrosion resistance of the Mg alloy. The discharge performance of CeN3O9·6H2O improves according to a discharge test, and the discharge time increases by 40 min.