Electrochemical characterization of a novel multicomponent Al₇₅Mg₅Li₁₀Zn₅Cu₅ low entropy alloy in different pH environments

The corrosion behavior and microstructure of a novel multicomponent Al₇₅Mg₅Li₁₀Zn₅Cu₅ low entropy alloy (Al LEA) were investigated in different Cl⁻ ion concentrations of acidic (HCl), neutral (NaCl), and alkaline (NaOH) media. The study was performed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The surface morphologies and chemical composition were examined by using a scanning electron microscope with energy-dispersive X-ray spectroscopy. The results indicated that with the increase of the Cl⁻ ion concentrations, the degradation rate with more pits and cracks was observed in both acidic and neutral media. This is due to the breakdown of Al(OH)₃/Al₂O₃ passive layer. In an alkaline medium, increasing of pH value from pH 8 to pH 12, there was a slight increment in corrosion rate (CR). However, the corrosion trend was not witnessed on alloy surfaces because of the formation of Mg₃₂(Al, Zn)₄₉ and AlCu phases, which are more stable than α-Al. The order of Al-LEA CR is found to be HCl > NaCl > NaOH. The results obtained from the polarization and EIS were in good agreement with each other.