Pyridinium-based ionic liquids as novel eco-friendly corrosion inhibitors for mild steel in molar hydrochloric acid: Experimental & computational approach

Two ionic liquids (ILs), (E)-4-(2-(4-fluorobenzylidene)hydrazinecarbonyl)-1-propylpyridin-1-ium iodide (Ipyr-C3H7) and (E)-4-(2-(4-fluorobenzylidene) hydrazinecarbonyl)-1-pentylpyridin-1-ium iodide (Ipyr-C5H11) were evaluated as novel inhibitors for mild steel corrosion in 1 M HCl using electrochemical techniques and quantum chemical calculation. The results revealed that Ipyr-C3H7 and Ipyr-C5H11 acted as mixed-type inhibitors with anodic predominance and achievd an inhibition efficiency of around 88%. The adsorption of the ILs on the metal surface followed the Langmuir kinetic-thermodynamic isotherm. The theoretical approach was performed using DFT calculations at B3LYP, 6-311++G(d,p) to correlate the experimental results. Most descriptors showed a good correlation with the inhibition performance achieved experimentally. Molecular dynamics simulations show that the selected molecules adsorb parallel to the substrate surface.