Preparation and characterization of the low-energy plasma electrolysis oxide coatings on Mg Li alloy

Plasma electrolytic oxidation (PEO) is a promising surface treatment method to improve the surface properties of light alloys. However, the high operating voltages led to significant power consumption and a burden on the grid, which limited its application. In this work, we employ a relatively low voltage (~100 V) in an organic-inorganic mixed electrolyte solution, and successfully achieve aa low energy plasma electrolysis oxidation (LEPEO) coating, enabling the reduction of the energy consumption of PEO on MgLi alloy. The energy consumption per unit volume (ECPUV) of the LEPEO process is 8.3 kJ·(dm2·μm)−1, which is approximate 57.0% energy consumption savings compared with the PEO process (19.3 kJ·(dm2·μm)−1, NaOH-Na2SiO3 electrolyte). Results show no remarkable difference between the two coatings in terms of morphologies, thickness, element type and distribution. The fracture process and corrosion protection performance of the coatings were evaluated by in-situ SEM tensile test and electrochemical impedance spectroscopy (EIS). The LEPEO coating only consists of MgO and amorphous SiOx, showing higher tensile strength, deformation displacement and better corrosion resistance compared with the PEO coating. The improved surface properties and lower energy consumption of LEPEO coatings will facilitate the application and development of PEO technology.