Enhancement of Corrosion Resistance and Tribological Properties of LA43M Mg Alloy by Cold-Sprayed Aluminum Coatings Reinforced with Alumina and Carbon Nanotubes

Magnesium is a suitable material for structural and aerospace applications owing to its high strength to weight ratio, yet the wide usage of Mg alloys is restricted due to their poor corrosion and mechanical properties. In this study, cold gas spraying method was used to produce pure Al, Al-Al₂O₃ and Al-Al₂O₃-CNTs coatings with feedstock powder containing Al admixed with 5 wt.% Al₂O₃ and 1 wt.% CNTs to improve electrochemical and tribological properties of Mg-LA43M alloy. X-ray diffraction spectroscopy and scanning electron microscopy were performed for compositional and microstructural analysis of feedstock powders as well as coatings. Furthermore, corrosion properties of coatings were examined by photodynamic polarization, electrochemical spectroscopy and long-term immersion test in 3.5% NaCl solution. The obtained results were correlated with microstructural analysis and we found that reinforcement of hard particles, especially CNTs, resulted in better corrosion resistance of MMC coatings as compared to Mg substrate and pure Al coatings. Reinforcements of Al₂O₃ and CNTs also improved the sliding wear resistance of the coatings. Al-Al₂O₃-CNTs exhibited lower coefficient of friction and wear rate than the Mg substrate, pure Al, and Al-Al₂O₃ coatings due to the denser microstructure.