8-hydroxyquinoline can be used as a raw material for the synthesis of corrosion inhibitors. And studies have reported the corrosion inhibition of 8-hydroxyquinoline derivatives on N80 steel in 1 M hydrochloric acid medium.

Firstly, three corrosion inhibitors containing different heteroatoms, namely N-dodecyl-5-amino-methyl-8-hydroxyquinoline (12N-HQ), 5-dodecyloxy-methyl-8-hydroxyquinoline (12O-HQ), and 5-dodecylthio-methyl-8-hydroxyquinoline (12S-HQ) were synthesized from 1-dodecylamine, 1-dodecanol, 1-dodecanethiol, and 8-hydroxyquinoline. The structures of the synthesized products were characterized by infrared spectroscopy and nuclear magnetic resonance hydrogen spectrometry.

The effects of 12N-HQ, 12O-HQ, and 12S-HQ on the corrosion of N80 steel in hydrochloric acid solution were studied by electrochemical measurements: electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). The surface analysis of N80 steel was carried out using infrared spectroscopy (FT-IR), scanning electron microscopy (FE-SEM), and X-ray diffractometer (XRD). The IR and 1HNMR spectra results confirmed the generation of characteristic peaks of C-N-C, C-O-C, and C-S-C, indicating that the products were 12N-HQ, 12O-HQ, and 12S-HQ.

The PDP results demonstrated that the 12N-HQ, 12O-HQ, and 12S-HQ corrosion inhibitors were all mixed corrosion inhibitors. The EIS results were 93.60%, 93.37%, and 95.31% corrosion inhibition efficiency for the three inhibitors at a concentration of 1 mM, respectively. The FT-IR, FE-SEM, and XRD studies showed that 12N-HQ, 12O-HQ, and 12S-HQ molecules adhered and constructed a surface protective layer on the surface of N80 steel. Density flooding theory (DFT) calculations and molecular dynamics simulations (MD) better explain the influence of 12N-HQ, 12O-HQ, and 12S-HQ molecular structures and electrons on corrosion resistance, in addition to the results obtained by DFT and the simulation of MD agree with the experimental results.

References:

[1] JING WU . Design, characteristics, and theoretical analyses of 8-hydroxyquinoline derivatives with different heteroatoms as effective corrosion inhibitors[J]. Materials Chemistry and Physics, 2023, 304: Article 127929. DOI:10.1016/j.matchemphys.2023.127929.