Sealing of Anodized AZ31B Magnesium Alloy in Lanthanum-Based Solution: Interplay Between Sealing Parameters, Surface Chemistry, and Corrosion Resistance.

In the present work, a La-based sealing procedure was developed for the anodized AZ31B magnesium alloy. The effects of sealing time and temperature on the electrochemical behavior of the samples were investigated. The corrosion resistance was evaluated in 3.5 wt.% NaCl solution using potentiodynamic polarization tests. Scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) were used to examine the morphology and composition of the sealing films. The results were discussed based on the interplay between film composition, morphological aspects and surface roughness. The best corrosion resistance was obtained for the sample sealed for 20 minutes at 50 °C that exhibited the widest passive range, surpassing that of the anodized (unsealed) sample by more than three times. As indicated by the SEM and XPS results, the formation of a uniform sealed layer comprised of a mixture of La₂O₃ and La(OH)₃ enhanced the corrosion resistance of the anodized AZ31B. [ABSTRACT FROM AUTHOR]