Synthesis of 2-aminofluorene bis-Schiff base and corrosion inhibition performance for carbon steel in HCl

Three new bis-Schiff bases, including bis(2-aminofluorene) glyoxal(L1), bis(2-aminofluorene) p-phthalaldehyde (L2) and bis(2-aminofluorene) 4,4′-biphenyldicarboxaldehyde (L3), were synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR) and mass spectrometry (MS). Weight loss methods indicated that all these inhibitors have good resistance to 1.0 mol·L −1 hydrochloric acid corrosion , and the highest inhibition efficiency was 98.2% at 65 °C for L3. Polarization curves and electrochemical impedance spectroscopy (EIS) indicated that L3 exhibited excellent inhibition effect when concentration was 1.0 mmol·L −1 . Moreover, the L3 was adsorbed spontaneously onto the surface by both physisorption and chemisorption , which followed the Langmuir adsorption isotherm . The relationship between molecular structure and quantum chemical structure parameters of three bis-Schiff base corrosion inhibitors was studied by Quantum chemistry calculation performed by density function theory (DFT) method. Results showed that L3 had excellent inhibition performance, which was consistent with experimental results.