Preparation and corrosion resistance of rare earth ceramic film on AZ91 Magnesium alloy

With the purpose of improving corrosion resistance and solving environmental pollution caused by traditional protective technique, rare earth ceramic film on AZ91 magnesium alloy was prepared by dip coating process, and technical parameters of preparation were defined. Microstructure and composition of the film were studied and corrosion resistance was evaluated as well. The results show that rare earth ceramic film is uniform, dense, with strong cohesion and intact coverage. The film is mainly made up of CeO₂ and MgCeO₃. The results of corrosion experiments approve that the film acts as a barrier to isolate the contact of the substrate with corrosion media and decrease corrosion rate. Polarization curve of the coated sample shifts to positive potential obviously, corrosion current density declines from 12 to 0.2 mA·cm² and polarization resistance increases from 100 to 2.7×10⁴Ω. These facts indicate that rare earth ceramic film could effectively improve corrosion resistance of AZ91 magnesium alloy.