Enhancing wear and corrosion resistance of magnesium alloys through in-situ Al2O3 doping for plasma electrolytic oxidation coating

Abstract

The surface of PEO coatings may contain micro-cracks and pores, which can facilitate the penetration of corrosive media and initiate corrosion. Doping particles has been identified as an effective method for enhancing corrosion resistance. This study investigates the impact of in-situ doping of Al2O3 particles of varying sizes on the performance of PEO coatings. It was observed that at lower concentrations, the particles are primarily inertly doped into the coating, while larger particles tend to be deposited on the surface. The addition of Al2O3 particles through the PEO process improves breakdown and final voltages, reduces porosity, and enhances abrasion resistance of the coatings. Furthermore, the │Z│0.01 Hz of Al2O3-containing coatings remained at approximately 107 Ω⋅cm2 for 10 days during immersion in NaCl solution. The corrosion current density is reduced from 78.01 to 6.51 nA/cm2. Among the different coatings, the PEO- Al2O3-200 coating exhibited the most promising results in terms of corrosion resistance and lubricating properties. The enhanced corrosion resistance is attributed to the promotion of Mg2Al(OH)7 formation during the corrosion process.