Film formation on magnesium alloy AZ31B in 1-butyl-3-methylimidazolium dibutylphosphate ionic liquid

A process to protect the magnesium alloy AZ31B against corrosion is introduced in this work. Immersing the alloy into 1-butyl-3-methylimidazolium dibutylphosphate ionic liquid at the presence of water a film was observed on the surface of the alloy. Scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDX), X-ray photoelectron spectroscopy (XPS), and the cross-sectional SEM were used to characterize the film. The results showed that the immersion in the ionic liquid produced a non-uniform film on the surface of the alloy and the defects on the film were Al and Mn-rich intermetallic. The cross-sectional SEM gave the visual of the film which indicate that the thickness of the film is about 3 μm. Electrochemical methods were used to monitor the formation of the film and evaluate the corrosion rates of the alloy covered by the film, and the results showed that the ionic liquid converting film enhanced the corrosion resistance of the alloy.