In-depth experimental assessment of two new aminocoumarin derivatives as corrosion inhibitors for carbon steel in HCl media combined with AFM, SEM/EDX, contact angle, and DFT/MDs simulations

•AMT and AMH of two Schiff bases were synthesized and confirmed successfully.•Polarisation investigations revealed that both inhibitors were mixed-type inhibitors.•According to adsorption studies, the inhibitors followed the Langmuir isotherm.•The experimental findings and theoretical computations were in agreement. The suitability of the two synthesized hydrazones namely N''-[(4-aminocoumarin-3-yl)methylidene]thiocarbonohydrazide (AMT), and 2-[(4-Aminocoumarin-3-yl)methylidene]hydrazinecarbodithioic acid (AMH) as corrosion inhibitors for N80 carbon steel (N80 CS) metal in acidic hydrochloric solution has been investigated at different concentrations of inhibitors (10–7 to 10–3 M) and different temperatures (298–328 K). The Inhibition efficiency was examined by gravimetric measurements, electrochemical methods supplemented with AFM, SEM-EDX, contact angle measurement, and XRD. The compounds have been characterized using IR, 1H NMR, 13C NMR, and mass spectra. It was found that AMT and AMH exhibit maximum inhibition efficiency of 90.52 and 93.28 %, respectively, at 10−3M against N80 CS corrosion in 1.0 M HCl solutions. The adsorption of inhibitors on the N80 CS surface tends to obey the Langmuir adsorption isotherm. Potentiodynamic polarization results revealed that AMT and AMH functioned as mixed-type inhibitors. All thermodynamic parameters were estimated and discussed. The combination of density functional theory (DFT) and molecular dynamic simulations was used to understand the sites in the AMT and AMH molecules where interaction with the N80 CS surface can occur. Results of the biological test revealed the excellent bioactivity of the AMT and AMH compounds, suggesting AMT and AMH are environmentally friendly corrosion inhibitors. [Display omitted]