| Summary: | An organotin(IV) dithiocarbamate compound namely bis(N-ethyl-isopropyl dithiocarbamate)chlorido butyltin(IV) [EIDTC2ClBuSn] was successfully synthesised and characterised, and showed good potentiality as a corrosion inhibitor on mild steel surfaces in 1 M hydrochloric acid (HCl). This organotin(IV) compound was synthesised using in situ method and characterised via physical and spectroscopic analysis. The physical analyses involved are melting point determination and elemental analysis. Meanwhile, the spectroscopy analyses involved are Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) and Nuclear Magnetic Resonance (NMR), specifically proton (1H), carbon (13C) and tin (119Sn) NMR. Corrosion inhibition efficiency for the synthesised complex was determined using the conventional method of weight loss and electrochemical measurements involving Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarisation (PDP) analysis. Surface analysis techniques such as Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM-EDX) and Atomic Force Microscopy (AFM) were also employed. The inhibition efficiency was also found to increase with the concentration of inhibitor solution, and the highest percentage of inhibition efficiency (IE%) recorded was 91.78 %, 87.20 % and 98.27 % at 0.005 mM during weight loss, EIS and PDP analysis, respectively. The interaction between mild steel and the corrosion inhibitor is further described using theoretical studies involving the adsorption isotherm theory and thermodynamic calculation. The adsorption of EIDTC2ClBuSn onto the mild steel surface obeys the Langmuir isotherm, and the type of adsorption involved based on Gibbs Free Energy (ΔGads) calculation is chemical adsorption. The neutral form of EIDTC2ClBuSn is subjected to the Density Functional Theory (DFT), revealing the predominant delocalisation of high-density electrons around the nitrogen and sulphur atoms. Despite ΔGads suggesting chemical adsorption, the theoretical investigation indicates the potential protonation of EIDTC2ClBuSn through the nitrogen atom, as identified by the Mulliken population analysis in the DFT study. Consequently, this suggests that the compound is capable of adsorbing onto the mild steel surface through both initial physical adsorption and subsequent chemical adsorption. © 2024 Elsevier Ltd
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