An ionic liquid-assisted strategy for enhanced anticorrosion of low-energy PEO coatings on magnesium–lithium alloy

A low-energy plasma electrolytic oxidation (LePEO) technique is developed to simultaneously improve energy efficiency and anti-corrosion. Ionic liquids (1‑butyl‑3-methylimidazole tetrafluoroborate (BmimBF₄)) as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid (ILs) during the LePEO process for LA91 magnesium–lithium (Mg–Li) alloy. Results show that the ionic liquid BmimBF₄ participates in the LePEO coating formation process, causing an increment in coating thickness and surface roughness. The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process (LePEO-IL). After adding BmimBF₄, corrosion current density decreases from 1.159 × 10⁻⁴ A·cm⁻² to 8.143 × 10⁻⁶ A·cm⁻². The impedance modulus increases to 1.048 × 10⁴ Ω·cm⁻² and neutral salt spray remains intact for 24 h. The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid. The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.