Part II: Impact of ionic liquids as anticorrosives and additives on Ni-Co alloy electrodeposition: Experimental and DFT study

Abstract

The impacts of 1-methyl-3-(2-oxo-2 ((2,4,5trifluorophenyl)amino)ethyle)-1H-imidazol-3-ium iodide ([MOFIM]I) and 1-(4-fluorobenzyl)-3-(4-phenoxybutyl)imidazol-3-ium bromide ([FPIM]Br) ionic liquids as additives on the corrosion behavior and the electrodeposition nucleation mechanism of a Ni-Co alloy were elucidated. A systematic investigation of the corrosion protection ability of Ni-Co alloys in a 3.5% NaCl solution was carried out using Tafel polarization and electrochemical impedance spectroscopy (EIS) studies. The mechanism of the Ni-Co alloy electrodeposition from the Ni70-Co30 bath was investigated using potentiodynamic cathodic polarization, cyclic voltammetry (CV) and anodic linear stripping voltammetry (ALSV). The studied ionic liquids (ILs) inhibit Co2+ and Ni2+ ion deposition due to their adsorption, which obeys the Langmuir adsorption isotherm. Quantum chemical calculations were performed at the B3LYP/6-311++G(d,p) level of the density functional theory (DFT). Several quantum parameters and natural atomic charges were calculated to investigate the correlation between the molecular structures of [MOFIM]I and [FPIM]Br and their corrosion inhibition performance. [MOFIM]I at 1 × 10−5 M shows a higher inhibition efficiency (IE%) of 53.05% than [FPIM]Br, at 44.3%. The results show that the calculated values of the quantum parameters are consistent with the experimental findings.