Effect of Y(NO 3 ) 3 ·6H 2 O addition on the structure and properties of micro-arc oxidation coatings on LA141 magnesium–lithium alloy

Abstract

Magnesium–lithium (Mg–Li) alloys are the lightest structural metals with high specific strength, but their aerospace, defense, and 3C applications are limited by micro-galvanic corrosion from α-Mg/β-Li phase potential differences and by micropores/cracks in micro-arc oxidation (MAO) coatings that accelerate corrosive media penetration. To address these issues, this study introduces Y(NO₃)₃·6H₂O as a functional additive in the MAO electrolyte for LA141 Mg–Li alloy (14 wt.% Li), aiming to improve coating densification and corrosion resistance. Unlike conventional rare-earth additives (Ce, La), Y(NO₃)₃·6H₂O avoids forming insoluble silicates that reduce electrolyte conductivity. Orthogonal experiments determined optimal parameters: 10 g/L Na₂SiO₃, 5 A/dm², 15% duty cycle, and 10 min oxidation. At 1.0 g/L Y(NO₃)₃·6H₂O, the coating showed improved hardness (+244.88 HV), thickness (+10.0 μm), reduced roughness (0.736 μm) and porosity (7.23%), and a one-order decrease in corrosion current density with a 0.194 V positive shift in potential. XRD and SEM/EDS confirmed Y³⁺ incorporation as Y₂O₃, which influenced plasma discharge, promoted MgO/Mg₂SiO₄ formation, and suppressed micropores—an effect not reported in previous rare-earth-modified MAO coatings for high-Li alloys.

This work demonstrates a scalable MAO route for LA141 with enhanced protective performance, and offers insights into Y(NO₃)₃·6H₂O's role in coating formation on α/β dual-phase Mg–Li alloys. The approach could help balance coating compactness, mechanical strength, and corrosion resistance, supporting broader Mg–Li alloy use in demanding service environments.