Pyridazinium-based ionic liquids as novel and green corrosion inhibitors of carbon steel in acid medium: Electrochemical and molecular dynamics simulation studies

Two new pyridazinium-based ionic liquids namely 1-(6-ethoxy-6-oxohexyl)pyridazin-1-ium bromide (S₁) and 1-(2-bromoacetyl) pyridazinium bromide (S₂) were synthesized and their inhibitive performance towards the corrosion of mild steel in 1 M hydrochloric acid was studied using electrochemical impedance spectroscopy (EIS) at various temperatures (303–333 K). It was shown that the inhibition efficiency increased with the concentration of S₁ and S₂ and reached 84% for S₁ and 82% for S₂ at 10^{− 3} M (303 K). Impedance measurements revealed that the charge transfer resistance (R_ct) increased and the double layer capacitance (C_dl) decreased with an increase in the concentration of both the inhibitors. The thermodynamic parameters provided the evidence of the inhibitory effect. Langmuir isotherm model fitted well with the adsorption of the studied compounds. Furthermore, spontaneity of the adsorption process, evaluated from the sign of free energy (ΔG_ads^o) values, showed an increase upon increase in temperature in the presence of inhibitors. Dynamics simulation indicated the possibility of gradual substitution of water molecules from the iron surface.