Novel quaternary ammonium Gemini surfactant as a highly efficient inhibitor for the corrosion of steel in HCl and H2 SO4 solutions

Ethyl-bis(octadecyl dipolyoxyethylene ammonium chloride) (E-BODAC) was a novel quaternary Gemini surfactant and was first found and identified as an excellent inhibitor with excellent surface activity and suitability. The ethoxy group enhances its hydrophilicity, and facilitates a dense adsorption film on metal surface. The inhibitive action and mechanism of E-BODAC on cold rolled steel (CRS) in HCl and H2 SO4 solutions was studied in detail by theoretical and experimental methods. The surface activity and degree of polymerization of the surfactant are tightly related to the anti-corrosion properties. HCl has a lower critical micelle concentration (CMC) than H2 SO4 solutions. The hydrophilic group in E-BODAC is the preferred site for donating and accepting electrons, with chemical interactions occurring among O, C, and Fe. The addition of E-BODAC obeys Langmuir isotherm, which can drastically reduce the diffusion of H3 O+ , Cl-/SO4 2-. E-BODAC has superior corrosion inhibition performance and lower dosage, and the inhibition efficiency for CRS reaches 92.9 % in 1.0 M HCl with only 10 mg L-1 of E-BODAC and 91.5 % in 0.50 M H2 SO4 . The inhibition is through physical and chemical adsorption to form a protective film that covers the reaction site, blocking the corrosion reaction. CLSM, SEM, AFM, XPS, and time-of-flight secondary ion mass spectrometer (TOF-SIMS) provide evidence of the adsorption of E-BODAC, efficiently slowing down the corrosion of CRS surface. E-BODAC always shows higher efficiency in HCl than in H2 SO4 , which is attributed to the re-dissolution of the adsorbed film in the H2 SO4 solution. Besides, SO4 2- ions are larger and migrate more slowly than Cl- ions, resulting in weak adsorption on the metal surface. The assessment of E-BODAC's suitability and durability in different corrosive environments provides the opportunity to determine its optimum conditions and applicability to maximize its corrosion inhibition effect. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.