Investigation of benzyldimethylstearylammonium chloride as an effective cationic surfactant inhibitor for steel corrosion in Cl2CHCOOH solution

• ⸱BDMSAC is a highly efficient steel inhibitor, which can achieve an excellent corrosion inhibition rate (93.62%) even under trace conditions (at a concentration of 10 mg L -1 ). • ⸱The ToF-SIMS technology was innovatively used to assess the BDMSAC fragments on the CRS surface, verifying that these fragments can effectively bind to the CRS to form chemical conjugates. • ⸱The adsorption mechanism at the active sites of BDMSAC was elucidated by quantum chemical and molecular dynamics calculations. • ⸱The results of the FFV model containing BDMSAC were smaller than those of the FFV model without an inhibitor, confirming the high adsorption efficiency of BDMSAC and its ability to inhibit metal corrosion by filling membrane voids and enhancing the barrier effect. To develop an efficient cationic surfactant inhibitor, the corrosion inhibition mechanism and behavior of benzyldimethyloctadecylammonium chloride (BDMSAC) on cold rolled steel (CRS) in Cl 2 CHCOOH medium were investigated in this paper. Weight loss tests demonstrated that BDMSAC was an efficient inhibitor, with its performance influenced by the critical micelle concentration (CMC, 3 mg L -1 ) and achieving a maximum inhibition efficiency of 93.62%. Electrochemical measurements demonstrated that BDMSAC inhibited both cathodic and anodic reactions, and the double layer capacitance ( C dl ) decreased significantly from an initial value of 15.00 × 10 -2 to 6.75 × 10 -2 μ F cm -2 . X-ray Photoelectron Spectroscopy (XPS) surface analyses validated BDMSAC adsorption via N-polar head group interactions to form an inhibition film. Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) detected fragments (C 27 H 50 N + ) of BDMSAC, which confirmed that BDMSAC effectively binds to CRS. The adsorption mechanism of the active sites of BDMSAC was elucidated through quantum chemical (QC) calculations and was strongly supported by molecular dynamics (MD) simulations, providing theoretical insights into its inhibitory behavior. Theoretical calculations indicated that BDMSAC adsorbed parallelly on the steel surface, with electrophilic C and nucleophilic N as active sites. The addition of BDMSAC reduced the fractional free volume (FFV) from 17.35% to 7.45%, suggesting that the BDMSAC film inhibits the diffusion of corrosive particles.