Two new cationic Gemini surfactants: synthesis, surface activity, and applicability as a corrosion inhibitor

Two novel cationic Gemini surfactants (2CnGeQS, n = 12, 18) was designed and prepared via amidation and quaternization reaction. The molecular structure of the 2CnGeQS was confirmed by FTIR, 1H NMR and elemental analysis. The critical micelle concentration (CMC) of aqueous solutions of these surfactants was determined by surface tension measurements, and the surface activity parameter, such as effectiveness (πCMC), efficiency (pC20), critical micelle concentration (CMC), maximum surface excess (Гmax), minimum surface area (Amin), were obtained. The results showed that 2CnGeQS have a higher surface activity than conventional monomeric surfactant. The CMC decreases with an increment in hydrophobic chain length, however, the surface tension at the cmc (γCMC) shows the opposite trend. The thermodynamic parameters indicate that both micellization and adsorption processes of 2CnGeQS were spontaneous. In addition, the results obtained from weight loss measurements show that 2CnGeQS exhibits a greater protective effect than that of DTAB; inhibition efficiency (ηw%) of 2C12GeQS, 2C18GeQS%, and DTAB is 95.6%, 96.86%, and 52.8% for A3 carbon steel at 1 × 10−3 M.