Surface coatings can enhance the substrate material’s properties and increase its lifetime. HEA-based materials have been extensively investigated as coating materials due to their superior hardness, excellent oxidation and corrosion resistance, effective diffusion barrier properties and wear resistance. Magnetron sputtering has been regarded as one of the most efficient methods for the deposition of HEA-based thin films. Metallic- and nitride-based HEA coatings can be easily deposited by introducing N₂ gas along with the Ar in the reaction chamber. The parameters such as target composition, bias voltage, sputtering power and notably, gas flow ratio, influence the thin film’s morphology and mechanical properties.

Secondary aluminum production is required for the conservation of the environment. It can significantly reduce greenhouse gas emissions and energy consumption and reduce the consumption of alumina, a source of primary aluminum. Secondary aluminum production requires sorting processes for the metal scrap before starting the refining process. Salt slags generated from both primary and secondary aluminum production need to be recycled/treated as they are considered hazardous byproducts. This review paper discusses the methods used for sorting and refining aluminum waste and managing and utilizing slag cakes/slag from recycling techniques.