Electron-Donor Functionalization at the N-Position of Ethylenediamine Derivatives for Enhanced Aluminum Corrosion Inhibition.

The use of ethylenediamine-based compounds, including ethylenediamine (EDA), tetramethylethylenediamine (TMEDA), and disodium ethylenediaminetetraacetate (EDTA-2Na), as corrosion inhibitors for aluminum radiators in high-voltage direct current (HVDC) converter valve systems is investigated. The results of the electrochemical analysis demonstrate that EDA spontaneously adsorbs on aluminum surfaces through N-Al coordination, resulting in the formation of a protective layer that achieves a 97.28% corrosion inhibition rate. The electron-donating effect of methyl and carboxymethyl groups increases the electron cloud density of N, which facilitates their electrophilic reaction with Al. The carboxymethyl groups of EDTA-2Na facilitate chelate bonding via simultaneous Al-O/N coordination, resulting in the formation of stable complexes that achieve 99.09% inhibition efficiency. In contrast, the steric hindrance of the methyl group attached to the N atom of TMEDA weakens the adsorption between N and Al, lowering the inhibition efficiency to 96.10%. These molecular-level insights establish definitive structure‒activity relationships, providing scientific guidance for optimizing HVDC coolant formulations through strategic N-functionalization of ethylenediamine scaffolds.