N-[2-(3-indolyl)ethyl]-cinnamamide synthesized from cinnamomum cassia presl and alkaloid tryptamine as green corrosion inhibitor for Q235 steel in acidic medium

In this work, N-[2-(3-indolyl)ethyl]-cinnamamide (IA) synthesized from tryptamine (TA) and cinnamic acid was evaluated as green corrosion inhibitor for Q235 steel in 0.5 M HCl solution by weight loss tests, potentiodynamic polarization (PDP) curve and electrochemical impedance spectroscopy (EIS). Gravimetric measurements displayed the maximum inhibition efficiencies of TA and IA at 1.0 mM were up to 92.8% and 97.6%, respectively. PDP and EIS studies revealed they could hinder both hydrogen evolution and metal dissolution reactions and that the inhibiting effect was temperature and concentration dependent. The surface analysis of sample was presented through scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and atomic force microscope (AFM), which indicated the anti-corrosion ability of Q235 steel in hydrochloric acid was enhanced by the inhibitor. The adsorptive behavior of inhibitors including physisorption and chemisorption obeyed Langmuir isotherm. The inhibition mechanism was elucidated by determining the potential of zero charge (Epzc) at solid/liquid interface. Quantum chemistry calculation provided a theoretical estimate of the reactivities of TA and IA as corrosion inhibitors to ascertain the correlation between the inhibition efficiency and molecular structures. Results of molecular dynamics (MD) simulations confirm that IA shows better inhibitive performance due to higher interaction energy (- 79.1 kJ mol-1 for TA and - 144.16 kJ mol-1 for IA).