Inhibition action and mechanism of the quaternary ammonium cationic surfactant of benzyldimethylstearylammonium chloride on steel corrosion in HCl solution

Benzyldimethylstearylammonium chloride (BDMSAC) is a quaternary ammonium cationic surfactant with widespread and effective bactericidal action. Nevertheless, there is little report of its application in metal anticorrosion research. This work comprehensively explored the inhibitory property and mechanism of BDMSAC on the corrosion of cold rolled steel (CRS) in 1.0 M HCl using a series of classical experiments as well as molecular modeling calculations. The results show that the critical micelle concentration (CMC) of BDMSAC is 3.81 mg L- 1 in HCl solution, demonstrating high surface activity and thus existing excellent and stable inhibition action, with a maximum efficiency of 98.5 %. Its adsorption on the CRS surface matches the Langmuir isotherm and serves as a mixed inhibitor that suppresses both anodic and cathodic reactions, with the reaction course being driven by charge transfer resistance. Characterization by XPS, SEM, AFM and contact angle measurements confirms the generation of a stable adsorptive film on CRS, enhancing surface hydrophobicity. Theoretical calculations show that benzene group and N atom interact remarkably with CRS, maximizing the prevention of corrosive media penetration, and acting as an effective inhibitor.