Protective properties of functionalised tetrazine on an aerospace aluminium alloy (AA 2024-T3)

Environmental health concerns over conventional chromium based surface treatments on aluminium substrates are well known. Current research efforts have concentrated on developing protective technologies for multiple applications. Such properties would enable manufacturers to address both corrosion and bacterial threats in areas such as fuel tanks and delivery systems. The present study explores the anticorrosion properties of 1,2-dihydro 1, 2, 4, 5 tetrazine-3, 6-dicarboxylic acid (H₂DCTZ) on a copper rich aerospace aluminium alloy (AA 2024-T3). Furthermore the antimicrobial activity of the tetrazine is evaluated against Gram-positive and Gram-negative bacteria, both capable of inducing corrosion. The protective action of the tetrazine was investigated at different concentrations in a chloride ion rich environment (3.5% (w/v) NaCl) utilising electrochemical impedance spectroscopy (EIS). Results over a 72 h period proved that an optimum concentration was 500 ppm. FTIR and SEM elemental mapping of the surface confirmed the nitrogen rich tetrazine affinity for the copper rich intermetallic sites, through coordinate bonds, which delayed corrosion onset and reduced pit formation. Moderate antibacterial tetrazine activity was observed against Escherichia coli and 100% efficacy against Staphylococcus aureus at 250 ppm was achieved. The damage of the bacterial cell envelope at the critical concentrations (250 ppm) is proposed as a possible mechanism for antibacterial action.