Selective synthesis of new sugars based on 8-hydroxyquinoline as corrosion inhibitors for mild steel in HCl solution-effect of the saturated hydrocarbon chain: Theoretical and experimental studies

Abstract

New glucose derivatives based on 8-hydroxyquinoline have been prepared, and characterized by infrared (IR), and nuclear magnetic resonance (1H and 13C NMR). These compounds were tested as a corrosion inhibitors of mild steel in 1.0 M HCl medium, using mass loss (ML), Potentio-dynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), density functional theory (DFT) and monte carlo simulation (MCS). The surface of the steel after corrosion test has been characterized by scanning electron spectroscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The corrosive solutions have been characterized by UV–visible spectrometry (UV–vis). The inhibitory efficacy increases with decreasing temperature and increases with inhibitor concentration and reached to 96.5% for the best inhibitor at 298 K and the optimum concentration (1 × 10−3 M). The results of the studies show that these compounds are effective in the corrosion inhibition of mild steel, and the inhibition efficiency depends on the length of the saturated carbon chain. The polarization study shows that the two inhibitors act as mixed type inhibitors. The results of thermodynamic studies show that the two compounds are absorbed on the metal surface by chemical bonds (Chemisorption) following Langmuir isotherm. UV–visible analysis shows that the two compounds capable of forming chemical bonds with the iron metal. The theoretical studies are in good agreement with those of the experimental studies.