Innovative hybrid and bifunctional rare earth complexes as corrosion inhibitors for AA2024 Alloy: Electrochemical and surface analysis enhanced by DFT/MD simulation

Abstract

The hybrid inorganic–organic compounds, RE-thioglycolates (RE = Ce, Nd, Sm), were analyzed as effective green corrosion inhibitors of AA2024 alloy in 0.1 M NaCl solution. Utilizing Electrochemical Impedance Spectroscopy the protective inhibitory film on the alloy's surface was affirmed, alongside the persistence of a natural oxide layer over time. These complexes demonstrated notable corrosion inhibition efficiency over immersion from 1 h to 3 days, with Sm-thiog retaining the high inhibition efficiency of over 95 % during 72 h. All RE-thioglycolates are mixed-type inhibitors, imparting resistance against both general and pitting corrosion. The presence of a protective inhibitory film on the AA2024 surface in NaCl solution has been substantiated through various analytical techniques including FTIR, SEM/EDS and XPS. A detailed examination of the differential inhibition exhibited by these bifunctional complexes is elucidated through theoretical calculations. The smallest difference of HOMO and LUMO orbitals for Sm-thiog of 3.21 eV indicates that this inhibitor attains the strongest donor–acceptor interactions with the metal surface. Predictions generated by Density Functional Theory/Molecular Dynamics simulations suggest the potential formation of diverse inhibitory species within the electrolyte. The corrosion inhibition mechanism proposed for RE-thioglycolates is grounded in electrochemical and theoretical insights, and subsequently validated through surface analysis methods.