Synthesis, spectroscopic, and density functional theory studies of the corrosion inhibitive behaviour of n-(1,4-dihydro-1,4-dioxonaphthalene-3-yl)pyrazine-2-carboxamide chelator-ligand

Abstract

The inhibitory effect of N-(1,4-dihydro-1,4-dioxonaphthalene-3-yl) pyrazine-2-carboxamide (HL chelator) on the corrosion of mild steel (Ms) in 1M HCl remained appraised via weight loss (WL) estimations, atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM) and computational studies. The adsorption of the appraised ligand remained found to conform to Langmuir adsorption isotherm (LAI). The data acquired for ΔG_ads denotes chemisorption adsorption mechanism for the inhibitor while acquired AAS analysis results revealed that the concentration of iron in the inhibited corrosive medium is less than the concentration of iron in the uninhibited solution after immersion with Ms at the same contact time and was also observed to reduce with upsurge in concentration of the inhibitor. SEM micrographs acquired revealed that the existence of the studied compound lessened the degree of corrosion in addition to decreased surface roughness signifying establishment of protective inhibitor film at the Ms surface. The energy of highest occupied molecular orbital (E_HOMO) as well as energy of lowest unoccupied molecular orbital (E_LUMO) remained estimated via density functional theory (DFT) method from which other parameters were determined. The results acquired from computational studies were in conformity with those from experimental studies and both validate the use of HL chelator as an excellent and efficient inhibitor for the corrosion of Ms in 1 M HCl.