Repurposing electrical waste materials for developing corrosion-resistant medium entropy alloys

Reusing electrical waste as a sustainable metal source is a promising approach for producing next-generation alloys. In this work, vacuum arc melting (VAM) was used to produce three aluminum-based medium-entropy alloys (AlCuFeCrSi MEAs) from recycled electrical waste. The alloys contained Al in the range 36-46%; Cu in the range 28-35%; Fe in the range 11-18%; Cr in the range 5-6%; and Si in the range 3-6%, with variations in elemental composition resulting from the use of different recovered electrical waste components. Their corrosion performance was evaluated at room temperature, in a 3.5% NaCl solution with and without 1 g/L Mn or 1 g/L Zn as inhibitors. The phase composition and microstructural characterization were reported before corrosion testing. Hardness tests were performed on all investigated metals and MEAs and post-corrosion surface morphology analysis were used to determine the main deterioration features. Thermodynamic parameters, including mixing enthalpy, mixing entropy, and lattice distortion, were calculated to assess phase stability and solid-solution formation, and to determine relationships between these factors and corrosion behavior. According to potentiodynamic polarization studies, the Al35Cu15Fe5.5Cr3.5Si alloy had the lowest corrosion rate among MEAs in 3.5% NaCl (0.4 μm/y) and in 3.5% NaCl with Zn inhibitor (145.7 μm/y). On the other hand, the Al30Cu15Fe5.5Cr5.5Si alloy, with relatively higher Si content, exhibited the lowest corrosion rate among the MEAs (121.7 μm/y) in 3.5% NaCl with a Mn inhibitor. Post-corrosion examination revealed uniform corrosion, galvanic coupling, and localized pitting in all the MEAs studied.