Ecological assessment and corrosion inhibition potential of novel double-chain arginine-based cationic surfactants

This study investigates the environmental impact and corrosion inhibition of novel double-chain arginine-based cationic surfactants developed as antimicrobial agents. The research focuses on asymmetric double-chain surfactants (LANHCx) with a 12-carbon alkyl chain and a second chain of 3-10 carbons, linked to the amino acid polar head group via amide bonds. The study assessed how alkyl chain length affects the ecological properties. Aerobic biodegradability (CO₂ headspace test) and aquatic toxicity (short-term exposure on Daphnia magna, Aliivibrio fischeri, Tetraselmis chuii, and Phaeodactylum tricornutum) were evaluated. Corrosion inhibition efficiency was determined using electrochemical impedance spectroscopy (EIS). Alkyl chain length significantly influenced biodegradation rates (1-63 % at 12 mg C/L), with the C6 homologue showing minimal degradation, though it improved at lower concentrations. Biodegradation correlated with antimicrobial potency. These compounds exhibited over one order of magnitude lower aquatic toxicity than conventional quaternary ammonium surfactants (QACs). The arginine-based surfactant LANHC₆ effectively inhibited carbon steel corrosion in neutral conditions (80 % at 0.5 mM), outperforming conventional DTAC at a 32-fold lower concentration. Overall, these new amino acid-derived antimicrobial agents demonstrate higher biodegradation rates and lower toxicity compared to conventional QACs, making them promising alternatives as environmentally preferable corrosion inhibitors.