Influence of different electrolyte systems on the structure and corrosion behavior of micro-arc oxidation coatings on magnesium-lithium alloys

Purpose This study aims to systematically investigate the influence of carbonate-, phosphate- and silicate-based electrolyte systems on the discharge behavior, microstructure, phase composition and corrosion performance of micro-arc oxidation (MAO) coatings formed on LA103Z Mg-Li alloy. Design/methodology/approach The LA103Z Mg-Li alloy was subjected to surface treatment via micro-arc oxidation in carbonate-based, phosphate-based and silicate-based electrolytes. The coating morphology and elemental distribution were characterized by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS). Potentiodynamic polarization and electrochemical impedance spectroscopy were adopted to test the electrochemical performance in 3.5 Wt.% NaCl solution, and the corrosion resistance was evaluated by immersion tests and neutral salt spray tests. Findings Electrolyte composition strongly governs the voltage response and coating architecture during MAO. Carbonate electrolyte produces a thin, loose coating via carbonate decomposition and CO2 evolution; phosphate generates a thicker coating with large pores and through-cracks; silicate yields a uniform double-layer coating with fine pores and the greatest thickness. Phase analysis reveals Mg2SiO4 forms exclusively in silicate coatings, whereas phosphate-containing species were likely present in an amorphous or poorly crystalline form. The silicate coating exhibits the highest corrosion potential, lowest corrosion current density and best long-term stability in immersion and salt spray tests. Practical implications This study provides practical guidance for the design of MAO coatings on Mg–Li alloys for corrosion protection in chloride-containing environments. The results of this study demonstrate that electrolyte chemistry significantly influences coating structure and long-term corrosion resistance, with silicate-based systems offering superior performance. These findings can support the optimization of MAO process parameters for lightweight Mg–Li components in aerospace, transportation and electronics industries where improved durability and reduced corrosion failure are critical. Social implications Improving the corrosion resistance of Mg–Li alloys contributes to the broader adoption of lightweight structural materials, which can reduce energy consumption and carbon emissions in transportation and aerospace sectors. By enhancing the durability of magnesium-based components, this study indirectly supports sustainability goals through material efficiency and extended service life, aligning with global efforts toward low-carbon and resource-efficient engineering systems. Originality/value This study systematically compares the differences in structure and performance of MAO coatings on LA103Z Mg–Li alloy in carbonate-, phosphate- and silicate-based electrolytes, addressing the deficiencies of previous single-system investigations. By establishing correlations among electrolyte chemistry, discharge behavior, coating microstructure and corrosion performance, this study provides mechanistic insights and practical guidance for the rational design of durable MAO protective coatings on Mg–Li alloys.